FIELD

The present disclosure relates to a multi-spectral optical sensor and, in particular though not exclusively, to a sectored-view multi-spectral optical sensor comprising a plurality of spectral channels, each spectral channel comprising a corresponding lens element, a corresponding optical filter and a corresponding optical detector arrangement, wherein the multi-spectral optical sensor is configured so as to at least partially compensate for the chromatic aberration of the lens elements in two or more spectral channels. The present disclosure also relates to a multi-spectral camera and a multi-spectral optical emitter arrangement.

BACKGROUND

Colour constancy is a desirable attribute of image-sensing devices, such as cameras. Colour constancy refers to a capability of observing a feature or object as being of a relatively constant colour under different illuminations. That is, an appearance of an image captured by a camera may be affected by an ambient illumination. By means of example, if a colour temperature of an ambient light source is relatively low, e.g. in the region of 3000 Kelvin as may be the case for an incandescent light source, an image of a white object exposed to the ambient light source will comprise a reddish hue. In contrast, for an ambient light source with a high colour temperature, e.g. in the region of 6000 Kelvin as may be the case for daylight on an overcast day, the image of the white object will comprise a slight blueish hue. That is, the object will be observed by a camera as comprising a colour that depends upon the illumination of the object by the ambient light source.

It is known to compensate for such effects by using a multi-spectral ambient light sensor (ALS) to measure spectral information relating to a scene. For example, it is known to use white balancing, and preferably automatic white balancing (AWB), to adjust the colouration of images captured under different illuminations. For example, it is known to use predefined settings for typical lighting conditions such as daylight, fluorescent lighting or incandescent lighting to adjust the colouration of images captured under different illuminations. In some instances, the predefined settings may be automatically selected.

Existing techniques for white balancing include image processing by applying an algorithm based on a “Gray-World Theory” or a “White Patch Theory”. The Gray World Theory is based on an assumption that the average reflectance in a captured image is achromatic. That is, the average of three colour channels: red, green and blue, should be roughly equal. The White Patch Theory is based on an assumption that a brightest pixel in a captured image corresponds to a reflection of the ambient light source, and therefore the brightest pixel may correspond to a spectrum of the ambient illumination. Both approaches have known limitations and, notably, both approaches tend to produce substantially different results.

Moreover, different parts of a scene may be subject to different ambient lighting conditions. For example, even different parts of a uniform coloured object in a scene may appear differently according to the corresponding ambient lighting conditions of the different parts of the uniform coloured object. Accordingly, it is desirable to be able to correct a captured image of a scene for the effects of different ambient illumination conditions on different parts of the scene, without incurring the shortcomings of the prior art AWB methods. In this regard, it is known to detect the optical power in different spectral ranges incident on a sectored-view multi-spectral ALS from different directions of a scene and to use spectral reconstruction to determine the spectrum of the light incident on the sectored-view multi-spectral ALS from the different directions of the scene and to use the determined spectrum of the light incident on the sectored- view multi-spectral ALS from the different directions of the scene to correct a captured image of the scene. For example, referring to FIG. 1A, there is shown a sectored-view multi-spectral optical sensor in the form of a sectored-view multi-spectral ambient light sensor (ALS) 2 which defines a plurality of spectral channels 4. Each spectral channel 4 comprises a corresponding lens element 10, a corresponding optical filter 12 and a corresponding optical detector arrangement 14, wherein the lens element 10, the optical filter 12 and the optical detector arrangement 14 of each spectral channel 4 are aligned along a corresponding optical axis. The optical axes of the different spectral channels 4 are parallel to one another. Each optical filter 12 is a passband optical interference filter which defines a corresponding spectral passband. The optical filters 12 of two or more of the spectral channels 4 have different optical transmission spectra such as different optical transmission spectra having different spectral passbands.

As shown in more detail in FIG. 1B, the optical detector arrangement 14 of each spectral channel 4 comprises an array of optical detector regions 22 of a monolithic semiconductor chip 24, wherein the optical detector regions 22 are formed adjacent to a front surface of the monolithic semiconductor chip 24, and wherein each array of optical detector regions 22 has the same number and relative spatial arrangement of optical detector regions 22 as each of the other arrays of optical detector regions 22. Specifically, each optical detector arrangement 14 comprises a 3x3 array of optical detector regions 22 of the monolithic semiconductor chip 24. As may be appreciated from FIG. 1 B, the spectral channels 4 are arranged in a 3x4 array of spectral channels 4. The optical filter 12 of each spectral channel 4 is formed on, or attached to, the front surface of the monolithic semiconductor chip 24 over, or in front of, the corresponding 3x3 array of optical detector regions 22. The optical axis of each spectral channel 4 is generally perpendicular to the front surface of the monolithic semiconductor chip 24.

As shown in FIG. 1A, the lens elements 10 of the plurality of spectral channels 4 are defined by a microlens array (MLA) generally designated 30, wherein the microlens array 30 comprises a transparent substrate 32, and wherein the lens elements 10 are disposed on a front surface 34 of the substrate 32. The sectored-view multi-spectral ALS 2 also includes an opaque spacer 40 located between the monolithic semiconductor chip 24 and the substrate 32 of the MLA 30. The monolithic semiconductor chip 24 and the substrate 32 of the MLA 30 are attached to opposite sides of the spacer 40. Furthermore, the spacer 40 defines a plurality of apertures 42, wherein each aperture 42 is aligned with the optical axis of a corresponding one of the spectral channels 4.

From the foregoing description of the sectored-view multi-spectral ALS 2, one of skill in the art will understand that, in use, electrical signals generated by the different optical detector regions 22 of the same spectral channel 4 are associated with light incident on the sectored-view multi-spectral ALS 2 from a scene along corresponding different directions of incidence. One of skill in the art will also understand that, in use, electrical signals generated by corresponding optical detector regions 22 of different spectral channels 4 are associated with light incident on the sectored-view multi- spectral ALS 2 from the scene along the same direction of incidence.

However, as will now be described with reference to FIGS. 2A and 2B, any chromatic aberration of the lens elements can lead to differences in the focusing of light of different wavelengths incident on the corresponding optical detector regions of the different spectral channels. Specifically, referring to FIG. 2A there is shown a multi- spectral optical sensor in the form of a sectored-view multi-spectral ALS 102 which defines a plurality of spectral channels 104. Each spectral channel 104 comprises a corresponding lens element 110, a corresponding optical filter 112 and a corresponding optical detector arrangement 114, wherein the lens element 110, the optical filter 112 and the optical detector arrangement 114 of each spectral channel 104 are aligned along a corresponding optical axis. The optical axes of the different spectral channels 104 are parallel to one another. Each optical filter 112 is a passband optical interference filter which defines a corresponding spectral passband. The optical filters 112 of the different spectral channels 104 have different optical transmission spectra such as different optical transmission spectra having different spectral passbands.

The optical detector arrangement 114 of each spectral channel 104 comprises an array of optical detector regions 122 of a monolithic semiconductor chip 124, wherein the optical detector regions 122 are formed adjacent to a front surface 123 of the monolithic semiconductor chip 124, and wherein each array of optical detector regions 122 has the same number and relative spatial arrangement of optical detector regions 122 as each of the other arrays of optical detector regions 122. The optical axis of each spectral channel 104 is generally perpendicular to the front surface 123 of the monolithic semiconductor chip 124.

The lens elements 110 of the plurality of spectral channels 104 are defined by a MLA generally designated 130, wherein the MLA 130 comprises a transparent substrate 132, and wherein the lens elements 110 are disposed on a front surface 134 of the substrate 132.

The optical filter 112 of each spectral channel 104 is formed on, or attached to, the front surface 123 of the monolithic semiconductor chip 124 over, or in front of, the corresponding array of optical detector regions 122.

In use, when ambient light as represented by the (black) solid rays in FIG. 2A, is incident on the lens element 110 of any one of the spectral channels 104, the lens element 110 focusses different wavelengths to different focal planes as a consequence of the chromatic aberration of the lens element 110, wherein each focal plane is generally parallel to the front surface 123 of the monolithic semiconductor chip 124 and each focal plane is located at a different axial position with respect to the optical axis of the spectral channel 104. For example, as represented by the (red) dashed rays in FIG. 2A, the lens element 110 in each spectral channel 104 focusses light having a first wavelength to a first focal plane located at a first axial position. Similarly, as represented by the (green) dashed-dotted rays in FIG. 2A, the lens element 110 in each spectral channel 104 focusses light having a second wavelength to a second focal plane located at a second axial position, and, as represented by the (blue) dotted rays in FIG. 2A, the lens element 110 in each spectral channel 104 focusses light having a third wavelength to a third focal plane located at a third axial position. Referring now to FIG. 2B there is shown a multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 202 which defines a plurality of spectral channels 204. Each spectral channel 204 comprises a corresponding lens element 210, a corresponding optical filter 212 and a corresponding optical detector arrangement 214, wherein the lens element 210, the optical filter 212 and the optical detector arrangement 214 of each spectral channel 204 are aligned along a corresponding optical axis. The optical axes of the different spectral channels 204 are parallel to one another. Each optical filter 212 is a passband optical interference filter which defines a corresponding spectral passband. The optical filters 212 of the different spectral channels 204 have different optical transmission spectra such as different optical transmission spectra having different spectral passbands.

The optical detector arrangement 214 of each spectral channel 204 comprises an array of optical detector regions 222 of a monolithic semiconductor chip 224, wherein the optical detector regions 222 are formed adjacent to a front surface 223 of the monolithic semiconductor chip 224, and wherein each array of optical detector regions 222 has the same number and relative spatial arrangement of optical detector regions 222 as each of the other arrays of optical detector regions 222. The optical axis of each spectral channel 204 is generally perpendicular to the front surface 223 of the monolithic semiconductor chip 224.

The lens elements 210 of the plurality of spectral channels 204 are defined by a MLA generally designated 230, wherein the MLA 230 comprises a transparent substrate 232, and wherein the lens elements 210 are disposed on a front surface 234 of the substrate 232.

However, unlike the sectored-view multi-spectral ALS 102 of FIG. 2A, in the sectored-view multi-spectral ALS 202 of FIG. 2B, the optical filter 212 of each spectral channel 204 is formed on, or attached to, the front surface 234 of the transparent substrate 232 of the MLA 230 and the corresponding lens element 210 is formed, or attached to, the optical filter 212.

In use, when ambient light as represented by the solid (black) rays in FIG. 2B, is incident on the different optical filters 212 and lens elements 210 of different spectral channels 204, the different optical filters 212 transmit different wavelengths, or different ranges of wavelengths. As a consequence of the chromatic aberration of the lens elements 210, the lens elements 210 of different spectral channels 204 focus the corresponding different wavelengths, or different ranges of wavelengths, to different focal planes, wherein each focal plane is generally parallel to the front surface 223 of the monolithic semiconductor chip 224 and each focal plane is located at a different axial position with respect to the front surface 223 of the monolithic semiconductor chip 224. For example, as represented by the (red) dashed rays in FIG. 2B, the optical filter 212 in a first spectral channel 204 may transmit light having a first wavelength and the corresponding lens element 210 in the first spectral channel 204 may focus the light having the first wavelength to a first focal plane located at a first axial position. Similarly, as represented by the (green) dashed-dotted rays in FIG. 2B, the optical filter 212 in a second spectral channel 204 may transmit light having a second wavelength and the corresponding lens element 210 in the second spectral channel 204 may focus the light having the second wavelength to a second focal plane located at a second axial position, and, as represented by the (blue) dotted rays in FIG. 2B, the optical filter 212 in a third spectral channel 204 may transmit light having a third wavelength and the corresponding lens element 210 in the third spectral channel 204 may focus the light having the third wavelength to a third focal plane located at a third axial position.

The differences in the focusing of different wavelengths incident on the optical detector regions 22, 122, 222 of different spectral channels 4, 104, 204 in the sectored- view multi-spectral ALS 2, 102, 202 of FIGS. 1A, 2A, 2B can impair the accuracy and/or resolution with which the spectrum of the light incident on the sectored-view multi-spectral ALS 2, 102, 202 from any given direction from the scene can be determined using spectral reconstruction. A known solution to this problem is to employ two or more lens elements in each spectral channel 4, 104, 204 to compensate for the chromatic aberration of the lens elements 10, 110, 210. However, the use of two or more lens elements in each spectral channel 4, 104, 204 can add to the complexity and cost of the sectored-view multi-spectral ALS 2, 102, 204. Moreover, the use of two or more lens elements in each spectral channel 4, 104, 204 requires that the two or more lens elements in each spectral channel are aligned relative to one another and to the corresponding optical detector arrangement 14, 114, 214, for example to sub-micron accuracy, and then secured or held relative to one another and to the corresponding optical detector arrangement 14, 114, 214, thereby increasing the complexity and cost of manufacturing such a sectored-view multi-spectral ALS.

For similar reasons, chromatic aberration is also a problem in other known multi-spectral optical sensors such as multi-spectral cameras comprising a plurality of different spectral channels, each spectral channel comprising a corresponding lens element, a corresponding optical filter and a corresponding optical detector arrangement. Chromatic aberration is also a problem in known multi-spectral optical emitter arrangements comprising a plurality of different spectral channels, each spectral channel comprising a corresponding optical emitter having a corresponding optical emission spectrum and a corresponding lens element.

SUMMARY

According to an aspect of the present disclosure there is provided a multi- spectral optical sensor defining: a plurality of spectral channels, wherein each spectral channel comprises a corresponding lens element, a corresponding optical filter and a corresponding optical detector arrangement, wherein the lens element, the optical filter and the optical detector arrangement of each spectral channel are aligned along a corresponding optical axis and wherein the lens element and the optical detector arrangement of each spectral channel define a corresponding optical path extending from the lens element to the optical detector arrangement, wherein the optical filters of two or more of the spectral channels have different transmission spectra, and wherein the optical paths of said two or more spectral channels have optical path lengths which are selected so as to at least partially compensate for chromatic aberration of the lens elements of said two or more spectral channels.

Optionally, the optical filters of said two or more spectral channels have transmission spectra which include different spectral passbands.

Optionally, the lens elements of said two or more spectral channels are the same.

Optionally, each lens element comprises a corresponding lens profile and wherein the lens profiles of the lens elements of said two or more spectral channels are the same.

Optionally, said two or more spectral channels each comprise a single lens element.

Optionally, the optical paths of said two or more spectral channels have different path lengths.

Optionally, the optical axes of the spectral channels are generally parallel, wherein the optical detector arrangements of said two or more spectral channels are located in the same plane transverse to a direction of the optical axes of the spectral channels but wherein the lens elements of said two or more spectral channels are located in different planes transverse to the direction of the optical axes of the spectral channels.

Optionally, the multi-spectral optical sensor comprises solid transparent material in the optical paths of said two or more spectral channels.

Optionally, in each spectral channel, the solid transparent material is located or formed on a surface of the corresponding optical detector arrangement.

Optionally, the solid transparent material is joined or attached, for example bonded, to a surface of the optical detector arrangement.

Optionally, the solid transparent material defines a stepped profile, wherein the stepped profile includes a plurality of step regions, wherein each step region is located in the optical path of a corresponding spectral channel.

Optionally, each step region of the solid transparent material has a corresponding constant thickness across the step region.

Optionally, the multi-spectral optical sensor comprises different thicknesses of solid transparent material in the optical paths of said two or more spectral channels.

Optionally, the multi-spectral optical sensor comprises different thicknesses of the same solid transparent material in the optical paths of said two or more spectral channels.

Optionally, the multi-spectral optical sensor comprises different solid transparent materials in the optical paths of said two or more spectral channels, the different solid transparent materials having different refractive indices.

Optionally, the optical detector arrangement of each spectral channel comprises at least one corresponding optical detector.

Optionally, the optical detector arrangement of each spectral channel comprises a corresponding array of optical detectors.

Optionally, each array of optical detectors has the same number and relative spatial arrangement of optical detectors as each of the other arrays of optical detectors.

Optionally, the optical detector arrangement of each spectral channel comprises at least one corresponding optical detector region of a monolithic semiconductor chip.

Optionally, the optical detector arrangement of each spectral channel comprises a corresponding array of optical detector regions of a monolithic semiconductor chip.

Optionally, each array of optical detector regions has the same number and relative spatial arrangement of optical detector regions as each of the other arrays of optical detector regions. Optionally, each array of optical detector regions comprises a 2D array of optical detector regions such as a uniform 2D array of optical detector regions.

Optionally, each 2D array of optical detector regions has a first dimension which includes a plurality of optical detector regions, for example 3, 5, 10, one hundred or more, or one thousand or more, optical detector regions and a second dimension which includes a plurality of optical detector regions, for example 3, 5, 10, one hundred or more, or one thousand or more, optical detector regions.

Optionally, the lens elements of the plurality of spectral channels are defined by a microlens array.

Optionally, the microlens array comprises a transparent substrate.

Optionally, the lens elements are disposed on a front surface of the substrate of the microlens array.

Optionally, the lens elements are disposed towards the corresponding optical detector arrangement.

Optionally, the optical axes of the spectral channels are generally parallel, and wherein the plurality of lens elements are located in the same plane transverse to the direction of the optical axes of the spectral channels.

Optionally, the front surface of the substrate of the microlens array defines a stepped profile, wherein the stepped profile includes a plurality of step regions, and wherein each lens element is defined or formed on a corresponding step region.

Optionally, each step region of the substrate of the microlens array has a corresponding constant thickness across the step region.

Optionally, a rear surface of the substrate of the microlens array is generally planar.

Optionally, the lens elements are disposed on a rear surface of the substrate of the microlens array.

Optionally, the lens elements are disposed away from the corresponding optical detector arrangement.

Optionally, wherein a front surface of the substrate of the microlens array defines a stepped profile, wherein the stepped profile includes a plurality of step regions, wherein each step region is aligned with a corresponding lens element on the rear surface of the substrate of the microlens array.

Optionally, each step region of the substrate of the microlens array has a corresponding constant thickness across the step region. Optionally, solid transparent material is located or formed on the rear surface of the substrate of the microlens array or wherein solid transparent material is joined or attached, for example bonded, to the rear surface of the substrate of the microlens array.

Optionally, the multi-spectral optical sensor comprises a solid transparent member which includes, or which is formed from, one or more solid transparent materials, wherein the solid transparent member comprises a plurality of regions, each region is located in the optical path of a corresponding spectral channel between the corresponding lens element and the corresponding optical detector arrangement of the spectral channel.

Optionally, different regions of the solid transparent member have different thicknesses of solid transparent material.

Optionally, different regions of the solid transparent member have different thicknesses of the same solid transparent material.

Optionally, a front surface of the solid transparent member defines a stepped profile, wherein the stepped profile includes a plurality of step regions, wherein each step region is located in the optical path of a corresponding spectral channel.

Optionally, each step region of the solid transparent member has a corresponding constant thickness across the step region.

Optionally, the solid transparent member comprises a transparent substrate and one or more layers of solid transparent material disposed on the substrate, wherein each layer of solid transparent material extends over a corresponding area of the substrate so as to define the plurality of step regions.

Optionally, a rear surface of the solid transparent member is generally planar.

Optionally, the front surface of the solid transparent member is disposed towards the monolithic semiconductor chip or away from the monolithic semiconductor chip.

Optionally, each region of the solid transparent member comprises a different solid transparent material, each different solid transparent material having a different refractive index.

Optionally, the solid transparent member is joined or attached, for example bonded, to the monolithic semiconductor chip.

Optionally, the solid transparent member is joined or attached, for example bonded, to the microlens array. Optionally, the optical filter of each spectral channel is located outside the corresponding optical path between the corresponding lens element and the corresponding optical detector arrangement.

Optionally, the optical filter of each spectral channel is located or formed on a surface of the substrate of the microlens array, or wherein the optical filter of each spectral channel is joined or attached, for example bonded, to a surface of the substrate of the microlens array, wherein said surface of the substrate of the microlens array is disposed towards, or away from, the monolithic semiconductor chip.

Optionally, the optical filter of each spectral channel is located in the corresponding optical path between the corresponding lens element and the corresponding optical detector arrangement.

Optionally, the optical filter of each spectral channel is located or formed on a surface of the solid transparent member, or wherein the optical filter of each spectral channel is joined or attached, for example bonded, to a surface of the solid transparent member.

Optionally, the optical filter of each spectral channel is located or formed on a surface of the monolithic semiconductor chip or wherein the optical filter of each spectral channel is joined or attached, for example bonded, to a surface of the monolithic semiconductor chip.

Optionally, each spectral channel comprises a corresponding aperture.

Optionally, the aperture of each spectral channel is located outside the corresponding optical path between the corresponding lens element and the corresponding optical detector arrangement.

Optionally, the apertures of the plurality of spectral channels are defined by an aperture member or by a patterned layer of opaque material which is located or formed on a surface of the substrate of the microlens array or is joined or attached, for example bonded, to a surface of the substrate of the microlens array.

Optionally, the aperture of each spectral channel is located in the corresponding optical path between the corresponding lens element and the corresponding optical detector arrangement.

Optionally, the apertures of the plurality of spectral channels are defined by an aperture member or by a patterned layer of opaque material which is located or formed on a surface of the solid transparent member or is joined or attached, for example bonded, to a surface of the solid transparent member. Optionally, the optical filters of different spectral channels are different and wherein the optical paths of different spectral channels have different optical path lengths.

Optionally, the lens elements of all of the spectral channels are the same.

Optionally, the multi-spectral optical sensor may be configured for operation at one or more wavelengths in an ultraviolet (UV), a visible (VIS), a near-infrared (NIR), a short-wavelength infrared (SWIR) or a mid-infrared (MIR) wavelength range, and the lens element, the optical filter and the optical detector arrangement of each spectral channel may be configured accordingly.

According to an aspect of the present disclosure there is provided a sectored- view multi-spectral optical sensor or a multi-spectral camera comprising: the multi-spectral optical sensor as described above, wherein the optical detector arrangement of each spectral channel comprises a corresponding array of optical detectors, each array of optical detectors having the same number and relative spatial arrangement of optical detectors as each of the other arrays of optical detectors.

Optionally, each array of optical detectors comprises an array of optical detector regions of a monolithic semiconductor chip.

Optionally, each array of optical detector regions comprises a 2D array of optical detector regions such as a uniform 2D array of optical detector regions.

Optionally, each 2D array of optical detector regions has a first dimension which includes a plurality of optical detector regions, for example 3, 5, 10, one hundred or more, or one thousand or more, optical detector regions and a second dimension which includes a plurality of optical detector regions, for example 3, 5, 10, one hundred or more, or one thousand or more, optical detector regions.

Optionally, the lens element, the optical filter and the array of optical detectors of each spectral channel are arranged so that electrical signals generated by different optical detectors of the same spectral channel are associated with light incident on the sectored-view multi-spectral optical sensor or the multi-spectral camera from a scene along corresponding different directions of incidence.

Optionally, the lens element, the optical filter and the array of optical detectors of each spectral channel are arranged so that electrical signals generated by corresponding optical detectors of different spectral channels are associated with light incident on the sectored-view multi-spectral optical sensor or the multi-spectral camera from the scene along the same direction of incidence. According to an aspect of the present disclosure there is provided a multi- spectral optical emitter arrangement comprising: a plurality of spectral channels, wherein each spectral channel comprises a corresponding optical emitter and a corresponding lens element aligned along a corresponding optical axis, wherein the optical emitter and the lens element of each spectral channel define a corresponding optical path extending from the optical emitter to the lens element, wherein the optical emitters of two or more of the spectral channels have different emission spectra, and wherein the optical paths of said two or more spectral channels have optical path lengths which are selected so as to at least partially compensate for chromatic aberration of the lens elements of said two or more spectral channels.

Optionally, the optical emitters of said two or more spectral channels have different narrowband emission spectra.

Optionally, the lens elements of said two or more spectral channels are the same.

Optionally, said two or more spectral channels each comprise a single lens element.

Optionally, the optical emitters of the plurality of spectral channels are defined by different regions of the same monolithic semiconductor chip.

It should be understood that any one or more of the features of any one of the foregoing aspects of the present disclosure may be combined with any one or more of the features of any of the other foregoing aspects of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Multi-spectral optical sensors, sectored-view multi-spectral optical sensors and multi-spectral optical emitter arrangements will now be described by way of non-limiting example only with reference to the drawings of which:

FIG. 1A is a schematic cross-section of a known multi-spectral optical sensor;

FIG. 1B is a schematic plan view of a monolithic semiconductor chip of the known multi-spectral optical sensor of FIG. 1A; FIG. 2A is a schematic cross-section of a known multi-spectral optical sensor illustrating the effects of the chromatic aberration of a lens element in each spectral channel;

FIG. 2B is a schematic cross-section of a known multi-spectral optical sensor illustrating the effects of the chromatic aberration of lens elements in different spectral channels;

FIG. 3 is a schematic cross-section of a first multi-spectral optical sensor according to the present disclosure;

FIG. 4 is a schematic cross-section of a second multi-spectral optical sensor according to the present disclosure;

FIG. 5 is a schematic cross-section of a third multi-spectral optical sensor according to the present disclosure;

FIG. 6 is a schematic cross-section of a fourth multi-spectral optical sensor according to the present disclosure;

FIG. 7 is a schematic cross-section of a fifth multi-spectral optical sensor according to the present disclosure;

FIG. 8 is a schematic cross-section of a sixth multi-spectral optical sensor according to the present disclosure;

FIG. 9 is a schematic cross-section of a seventh multi-spectral optical sensor according to the present disclosure;

FIG. 10 is a schematic cross-section of an eighth multi-spectral optical sensor according to the present disclosure;

FIG. 11 is a schematic cross-section of a ninth multi-spectral optical sensor according to the present disclosure; FIG. 12 is a schematic cross-section of a tenth multi-spectral optical sensor according to the present disclosure;

FIG. 13 is a schematic cross-section of an eleventh multi-spectral optical sensor according to the present disclosure;

FIG. 14 is a schematic cross-section of a twelfth multi-spectral optical sensor according to the present disclosure;

FIG. 15 is a schematic cross-section of a thirteenth multi-spectral optical sensor according to the present disclosure;

FIG. 16 is a schematic cross-section of a fourteenth multi-spectral optical sensor according to the present disclosure;

FIG. 17 is a schematic cross-section of a fifteenth multi-spectral optical sensor according to the present disclosure;

FIG. 18 is a schematic cross-section of a sixteenth multi-spectral optical sensor according to the present disclosure;

FIG. 19 is a schematic cross-section of a seventeenth multi-spectral optical sensor according to the present disclosure;

FIG. 20A is a schematic cross-section of an eighteenth multi-spectral optical sensor according to the present disclosure;

FIG. 20B is a schematic plan view of a monolithic semiconductor chip of the multi- spectral optical sensor of FIG. 20A; and

FIG. 21 is a schematic cross-section of a multi-spectral optical emitter arrangement according to the present disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS Referring initially to FIG. 3 there is shown a first multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 302 which defines a plurality of spectral channels 304. Each spectral channel 304 comprises a corresponding lens element 310, a corresponding optical filter 312 and a corresponding optical detector arrangement 314, wherein the lens element 310, the optical filter 312 and the optical detector arrangement 314 of each spectral channel 304 are aligned along a corresponding optical axis. Each optical filter 312 is a passband optical interference filter which defines a corresponding spectral passband. The optical filters 312 of the different spectral channels 304 have different optical transmission spectra such as different optical transmission spectra having different spectral passbands.

The optical detector arrangement 314 of each spectral channel 304 comprises an array of optical detector regions of a monolithic semiconductor chip 324, wherein the optical detector regions are formed adjacent to a front surface 323 of the monolithic semiconductor chip 324, and wherein each array of optical detector regions has the same number and relative spatial arrangement of optical detector regions as each of the other arrays of optical detector regions. The optical axis of each spectral channel 304 is generally perpendicular to the front surface 323 of the monolithic semiconductor chip 324.

The lens elements 310 of the plurality of spectral channels 304 are defined by a MLA generally designated 330, wherein the MLA 330 comprises a transparent substrate 332, and wherein the lens elements 310 are disposed on a front surface 334 of the substrate 332.

The optical filter 312 of each spectral channel 304 is formed on, or attached to, the front surface 323 of the monolithic semiconductor chip 324 over, or in front of, the corresponding optical detector arrangement 314.

Each spectral channel 304 defines a corresponding optical path extending from the corresponding lens element 310 to the corresponding optical detector arrangement 314. Unlike the sectored-view multi-spectral ALS 2, 102, 204 of FIGS. 1A, 2A, 2B, the sectored-view multi-spectral ALS 302 of FIG. 3 includes different thicknesses of solid transparent material 350 in the optical paths of the different spectral channels 304 so that the optical paths of the different spectral channels 304 have different optical path lengths. Specifically, different thicknesses of solid transparent material 350 are disposed on the front surface 323 of the monolithic semiconductor chip 324 over, or in front of, the optical filters 312 so as to define a stepped profile on a front surface 352 of the solid transparent material 350, wherein the stepped profile includes a plurality of step regions, and wherein each step region is located in the optical path of a corresponding spectral channel 304.

The different thicknesses of solid transparent material 350 may be formed on, deposited on, or applied to, the front surface 323 of the monolithic semiconductor chip 324 over, or in front of, the optical filters 312. For example, the different thicknesses of solid transparent material 350 may be defined by forming, depositing, or applying, an initial layer of solid transparent material 350 on the front surface 323 of the monolithic semiconductor chip 324 over, or in front of, the optical filters 312 and then applying one or more subsequent layers of solid transparent material 350 on the initial layer of solid transparent material 350, wherein each subsequent layer of solid transparent material 350 is disposed on a different area of the preceding layer of solid transparent material 350 so as to define the stepped profile on the front surface 352 of the solid transparent material 350.

Alternatively, the sectored-view multi-spectral ALS 302 may comprise a solid transparent member which includes, or which is formed from, the solid transparent material 350, wherein a rear surface 354 of the solid transparent member is attached, for example, bonded to the front surface 323 of the of the monolithic semiconductor chip 324 over, or in front of, the optical filters 312, wherein the solid transparent member comprises a plurality of regions, each region having a different thickness so as to define the stepped profile on the front surface 352 of the solid transparent member.

Moreover, each step region of the solid transparent material 350 has a corresponding constant thickness of the solid transparent material 350 across the step region, wherein the thickness is selected so as to at least partially compensate for the chromatic aberration of the corresponding lens element 310.

In use, when ambient light such as ambient visible light as represented by the solid (black) rays in FIG. 3, is incident on the lens element 310 of any one of the spectral channels 304, the lens element 310 refracts light of different wavelengths towards different focal planes as a consequence of the chromatic aberration of the lens element 310, wherein each focal plane is generally parallel to the front surface 354 of the monolithic semiconductor chip 324 and each focal plane is located at a different axial position with respect to the optical axis of the spectral channel 304. However, as a consequence of the corresponding thickness of the solid transparent material 350 in each spectral channel 304, the different wavelengths or ranges of wavelengths which are transmitted by the different optical filters 312 in the different spectral channels 304 are focussed by the different lens elements 310 of the different spectral channels 304 onto the different optical detector arrangements 314 adjacent to the front surface 354 of the monolithic semiconductor chip 324 so as to thereby at least partially compensate for the chromatic aberration of the lens elements 310.

For example, as represented by the (red) dashed lines in FIG. 3, the lens element 310 in each spectral channel 304 focusses light having a first wavelength to a focal plane located at an axial position coinciding with the corresponding optical detector arrangement 314. Similarly, as represented by the (green) dashed-dotted lines in FIG. 3, the lens element 310 in each spectral channel 304 focusses light having a second wavelength to the same focal plane located at the axial position coinciding with the corresponding optical detector arrangement 314, and, as represented by the (blue) dotted lines in FIG. 3, the lens element 310 in each spectral channel 304 focusses light having a third wavelength to the same focal plane located at the axial position coinciding with the corresponding optical detector arrangement 314.

At least partially compensating for the chromatic aberration of the lens elements 310 in the different spectral channels improves the accuracy and/or resolution with which the spectrum of the light incident on the sectored-view multi-spectral ALS 302 from any given direction from the scene can be determined using spectral reconstruction when compared with the accuracy and/or resolution of known sectored- view multi-spectral ALS 2, 102, 202. Moreover, it may be simpler and cheaper to form or attach the solid transparent material 350 to the front surface 323 of the monolithic semiconductor chip 324 so as to at least partially compensate for the chromatic aberration of the lens elements 310, than to use two or more lens elements in each spectral channel 304 so as to at least partially compensate for the chromatic aberration of the lens elements. Furthermore, as a consequence of the constant thickness of each region of the solid transparent material 350, the precision with which the stepped profile of the solid transparent material 350 needs to be aligned relative to the monolithic semiconductor chip 324 and the MLA 330 may be less than the (sub-micron) alignment precision required to align two or more lens elements in each spectral channel relative to one another and relative to the monolithic semiconductor chip such that the complexity and cost of manufacturing such a sectored-view multi-spectral ALS 302 may be less than the complexity and cost of manufacturing a sectored-view multi- spectral ALS having two or more lens elements in each spectral channel.

Referring to FIG. 4 there is shown a second multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 402. The sectored-view multi-spectral ALS 402 of FIG. 4 is essentially the same as the sectored-view multi-spectral ALS 302 of FIG. 3 except that in the sectored-view multi-spectral ALS 402 of FIG. 4, an optical filter 412 of each spectral channel 404 is formed on, or attached to, a front surface 434 of a transparent substrate 432 of a MLA 430 and the MLA 430 includes a lens element 410 which is formed over, or attached to, the corresponding optical filter 412 of each spectral channel 404. One of ordinary skill in the art will understand that the operation of the sectored-view multi-spectral ALS 402 of FIG. 4 is similar to the operation of the sectored-view multi-spectral ALS 302 of FIG. 3.

Referring to FIG. 5 there is shown a third multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 502. The sectored-view multi-spectral ALS 502 of FIG. 5 is essentially the same as the sectored-view multi-spectral ALS 302 of FIG. 3 except that in the sectored-view multi-spectral ALS 502 of FIG. 5, an optical filter 512 of each spectral channel 504 is formed on, or attached to, a rear surface 536 of a transparent substrate 532 of a MLA 530. One of ordinary skill in the art will understand that the operation of the sectored-view multi-spectral ALS 502 of FIG. 5 is similar to the operation of the sectored-view multi-spectral ALS 302 of FIG. 3.

Referring now to FIG. 6, there is shown a fourth multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 602 which defines a plurality of spectral channels 604. Each spectral channel 604 comprises a corresponding lens element 610, a corresponding optical filter 612 and a corresponding optical detector arrangement 614, wherein the lens element 610, the optical filter 612 and the optical detector arrangement 614 of each spectral channel 604 are aligned along a corresponding optical axis.

The lens elements 610 of the plurality of spectral channels 604 are defined by a MLA generally designated 630, wherein the MLA 630 comprises a transparent substrate 632, and wherein the lens elements 610 are disposed on a front surface 634 of the substrate 632.

The optical detector arrangement 614 of each spectral channel 604 comprises an array of optical detector regions of a monolithic semiconductor chip 624, wherein the optical detector regions are formed adjacent to a front surface 623 of the monolithic semiconductor chip 624, and wherein each array of optical detector regions has the same number and relative spatial arrangement of optical detector regions as each of the other arrays of optical detector regions. The optical axis of each spectral channel 604 is generally perpendicular to the front surface 623 of the monolithic semiconductor chip 624. The optical filter 612 of each spectral channel 604 is formed on, or attached to, the front surface 623 of the monolithic semiconductor chip 624 over, or in front of, the corresponding optical detector arrangement 614.

Each spectral channel 604 defines a corresponding optical path extending from the corresponding lens element 610 to the corresponding optical detector arrangement 614. The sectored-view multi-spectral ALS 602 further includes different thicknesses of solid transparent material 650 in the optical paths of the different spectral channels 604 so that the optical paths of the different spectral channels 604 have different optical path lengths and the thickness of solid transparent material 650 in each spectral channel 604 is selected so as to at least partially compensate for the chromatic aberration of the corresponding lens element 610.

The sectored-view multi-spectral ALS 602 of FIG. 6 is essentially the same as the sectored-view multi-spectral ALS 302 of FIG. 3 except that in the sectored-view multi-spectral ALS 602 of FIG. 6, the different thicknesses of solid transparent material 650 are provided in the form of a solid transparent member 660 which defines a stepped profile on a front surface 662 thereof, which has a generally planar rear surface 664, and which is separated from the monolithic semiconductor chip 624 by a gap. In other respects, the sectored-view multi-spectral ALS 602 of FIG. 6 is identical to the sectored-view multi-spectral ALS 302 of FIG. 3. Consequently, one of ordinary skill in the art will understand that the operation of the sectored-view multi-spectral ALS 602 of FIG. 6 is similar to the operation of the sectored-view multi-spectral ALS 302 of FIG. 3.

Referring to FIG. 7 there is shown a fifth multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 702. The sectored-view multi-spectral ALS 702 of FIG. 7 is essentially the same as the sectored-view multi-spectral ALS 602 of FIG. 6 except that in the sectored-view multi-spectral ALS 702 of FIG. 7, an optical filter 712 of each spectral channel 704 is formed on, or attached to, a generally planar rear surface 764 of a solid transparent member 760. One of ordinary skill in the art will understand that the operation of the sectored-view multi-spectral ALS 702 of FIG. 7 is similar to the operation of the sectored-view multi-spectral ALS 602 of FIG. 6.

Referring to FIG. 8 there is shown a sixth multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 802. The sectored-view multi-spectral ALS 802 of FIG. 8 is essentially the same as the sectored-view multi-spectral ALS 602 of FIG. 6 except that in the sectored-view multi-spectral ALS 802 of FIG. 8, an optical filter 812 of each spectral channel 804 is formed on, or attached to, a front surface 834 of a transparent substrate 832 of a MLA 830 and the MLA 830 includes a lens element 810 which is formed over, or attached to, the corresponding optical filter 812 of each spectral channel 804. One of ordinary skill in the art will understand that the operation of the sectored-view multi-spectral ALS 802 of FIG. 8 is similar to the operation of the sectored-view multi-spectral ALS 602 of FIG. 6.

Referring to FIG. 9 there is shown a seventh multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 902. The sectored-view multi-spectral ALS 902 of FIG. 9 is essentially the same as the sectored-view multi-spectral ALS 602 of FIG. 6 except that in the sectored-view multi-spectral ALS 902 of FIG. 9, an optical filter 912 of each spectral channel 904 is formed on, or attached to, a rear surface 936 of a transparent substrate 932 of a MLA 930. One of ordinary skill in the art will understand that the operation of the sectored-view multi-spectral ALS 902 of FIG. 9 is similar to the operation of the sectored-view multi-spectral ALS 602 of FIG. 6.

Referring to FIG. 10 there is shown an eighth multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 1002. The sectored-view multi-spectral ALS 1002 of FIG. 10 is similar to the sectored-view multi-spectral ALS 602 of FIG. 6 except that rather than the sectored-view multi-spectral ALS 1002 of FIG. 10 having different thicknesses of solid transparent material in different spectral channels 1004, the sectored-view multi-spectral ALS 1002 of FIG. 10 has different solid transparent materials 1050a, 1050b, 1050c of different refractive indices in the different spectral channels 1004. Specifically, the sectored-view multi-spectral ALS 1002 of FIG. 10 includes a solid transparent member 1060 which defines a plurality of regions, each region aligned with a different spectral channel 1004 and each region comprising a corresponding solid transparent material 1050a, 1050b, 1050c of a refractive index which is selected so as to at least partially compensate for the chromatic aberration of lens elements 1010 in the different spectral channels 1004.

One of ordinary skill in the art will understand that, although the path lengths of the different spectral channels 1004 of the sectored-view multi-spectral ALS 1002 of FIG. 10 from the lens elements 1010 to the optical detector arrangements 1014 are equal, as a consequence of the different refractive indices of the solid transparent materials 1050a, 1050b, 1050c in the different spectral channels 1004, the optical path lengths of the different spectral channels 1004 of the sectored-view multi-spectral ALS 1002 of FIG. 10 are different. In other respects, the sectored-view multi-spectral ALS 602 of FIG. 10 is identical to the sectored-view multi-spectral ALS 602 of FIG. 6. Consequently, one of ordinary skill in the art will understand that the operation of the sectored-view multi-spectral ALS 1002 of FIG. 10 is similar to the operation of the sectored-view multi-spectral ALS 602 of FIG. 6.

Referring to FIG. 11 there is shown a ninth multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 1102. The sectored-view multi-spectral ALS 1102 of FIG. 11 is essentially the same as the sectored-view multi-spectral ALS 1002 of FIG. 10 except that in the sectored-view multi-spectral ALS 702 of FIG. 11, an optical filter 1112 of each spectral channel 1104 is formed on, or attached to, a generally planar rear surface 1164 of a solid transparent member 1160. One of ordinary skill in the art will understand that the operation of the sectored-view multi- spectral ALS 1102 of FIG. 11 is similar to the operation of the sectored-view multi- spectral ALS 1002 of FIG. 10.

Referring to FIG. 12 there is shown a tenth multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 1202. The sectored-view multi-spectral ALS 1202 of FIG. 12 is essentially the same as the sectored-view multi-spectral ALS 1002 of FIG. 10 except that in the sectored-view multi-spectral ALS 1202 of FIG. 12, an optical filter 1212 of each spectral channel 1204 is formed on, or attached to, a front surface 1234 of a transparent substrate 1232 of a M LA 1230 and each lens element 1210 is formed over, or attached to, the corresponding optical filter 1212. One of ordinary skill in the art will understand that the operation of the sectored-view multi- spectral ALS 1202 of FIG. 12 is similar to the operation of the sectored-view multi- spectral ALS 1002 of FIG. 10.

Referring to FIG. 13 there is shown an eleventh multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 1302. The sectored-view multi-spectral ALS 1302 of FIG. 13 is essentially the same as the sectored-view multi-spectral ALS 1002 of FIG. 10 except that in the sectored-view multi-spectral ALS 1302 of FIG. 13, an optical filter 1312 of each spectral channel 1304 is formed on, or attached to, a rear surface 1336 of a transparent substrate 1332 of a MLA 1330. One of ordinary skill in the art will understand that the operation of the sectored-view multi-spectral ALS 1302 of FIG. 13 is similar to the operation of the sectored-view multi-spectral ALS 1002 of FIG. 10.

Referring now to FIG. 14, there is shown a twelfth multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 1402 which defines a plurality of spectral channels 1404. Each spectral channel 1404 comprises a corresponding lens element 1410, a corresponding optical filter 1412 and a corresponding optical detector arrangement 1414, wherein the lens element 1410, the optical filter 1412 and the optical detector arrangement 1414 of each spectral channel 1404 are aligned along a corresponding optical axis.

The lens elements 1410 of the plurality of spectral channels 1404 are defined by a M LA generally designated 1430, wherein the MLA 1430 comprises a transparent substrate 1432, wherein the transparent substrate 1432 comprises a plurality of regions, each region having a different thickness so as to define a stepped profile on a front surface 1434 of the transparent substrate 1432. Moreover, each step region of the transparent substrate 1432 has a corresponding constant thickness across the step region, wherein the thickness is selected so as to at least partially compensate for the chromatic aberration of the corresponding lens element 1410. Each lens element 1410 is disposed on a corresponding step region of the transparent substrate 1432.

The optical detector arrangement 1414 of each spectral channel 1404 comprises an array of optical detector regions of a monolithic semiconductor chip 1424, wherein the optical detector regions are formed adjacent to a front surface 1423 of the monolithic semiconductor chip 1424, and wherein each array of optical detector regions has the same number and relative spatial arrangement of optical detector regions as each of the other arrays of optical detector regions. The optical axis of each spectral channel 1404 is generally perpendicular to the front surface 1423 of the monolithic semiconductor chip 1424.

The optical filter 1412 of each spectral channel 1404 is formed on, or attached to, the front surface 1423 of the monolithic semiconductor chip 1424 over, or in front of, the corresponding optical detector arrangement 1414.

Each spectral channel 1404 defines a corresponding optical path extending from the corresponding lens element 1410 to the corresponding optical detector arrangement 1414.

One of ordinary skill in the art will understand that the sectored-view multi- spectral ALS 1402 of FIG. 14 is similar to the sectored-view multi-spectral ALS 302 of FIG. 3, but that the sectored-view multi-spectral ALS 1402 of FIG. 14 does not include any solid transparent material disposed on the optical filters 1412 of the different spectral channels 1404. Instead, and, as a consequence of the stepped profile of the front surface 1434 of the substrate 1432 of the MLA 1430, the optical paths of the different spectral channels 1404 have different path lengths, and therefore also different optical path lengths, wherein the path length or the optical path length of each spectral channel 1404 is selected so as to at least partially compensate for the chromatic aberration of the corresponding lens element 1410. In other respects, the sectored-view multi-spectral ALS 1402 of FIG. 14 is similar to the sectored-view multi-spectral ALS 302 of FIG. 3 and the operation of the sectored-view multi-spectral ALS 1402 of FIG. 14 is similar to the operation of the sectored-view multi-spectral ALS 302 of FIG. 3.

Referring now to FIG. 15, there is shown a thirteenth multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 1502. The sectored-view multi-spectral ALS 1502 of FIG. 15 is essentially the same as the sectored-view multi- spectral ALS 1402 of FIG. 14 except that in the sectored-view multi-spectral ALS 1502 of FIG. 15, an optical filter 1512 of each spectral channel 1504 is formed on, or attached to, a front surface 1534 of a transparent substrate 1532 of a M LA 1530 and each lens element 1510 is formed over, or attached to, the corresponding optical filter 1512. One of ordinary skill in the art will understand that the operation of the sectored- view multi-spectral ALS 1502 of FIG. 15 is similar to the operation of the sectored-view multi-spectral ALS 1402 of FIG. 14.

Referring now to FIG. 16, there is shown a fourteenth multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 1602. The sectored-view multi-spectral ALS 1602 of FIG. 16 is essentially the same as the sectored-view multi- spectral ALS 1402 of FIG. 14 except that in the sectored-view multi-spectral ALS 1602 of FIG. 16, an optical filter 1612 of each spectral channel 1604 is formed on, or attached to, a generally planar rear surface 1636 of a transparent substrate 1632 of a MLA 1630. One of ordinary skill in the art will understand that the operation of the sectored-view multi-spectral ALS 1602 of FIG. 16 is similar to the operation of the sectored-view multi-spectral ALS 1402 of FIG. 14.

Referring now to FIG. 17, there is shown a fifteenth multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 1702 which defines a plurality of spectral channels 1704. Each spectral channel 1704 comprises a corresponding lens element 1710, a corresponding optical filter 1712 and a corresponding optical detector arrangement 1714, wherein the lens element 1710, the optical filter 1712 and the optical detector arrangement 1714 of each spectral channel 1704 are aligned along a corresponding optical axis.

The lens elements 1710 of the plurality of spectral channels 1704 are defined by a MLA generally designated 1730, wherein the MLA 1730 comprises a transparent substrate 1732, wherein the transparent substrate 1732 comprises a plurality of regions, each region having a different thickness so as to define a stepped profile on a front surface 1734 of the transparent substrate 1732. Moreover, each step region of the transparent substrate 1732 has a corresponding constant thickness across the step region, wherein the thickness is selected so as to at least partially compensate for the chromatic aberration of the corresponding lens element 1710. Each lens element 1710 is disposed on a generally planar rear surface 1736 of the transparent substrate 1732.

The optical detector arrangement 1714 of each spectral channel 1704 comprises an array of optical detector regions of a monolithic semiconductor chip 1724, wherein the optical detector regions are formed adjacent to a front surface 1723 of the monolithic semiconductor chip 1724, and wherein each array of optical detector regions has the same number and relative spatial arrangement of optical detector regions as each of the other arrays of optical detector regions. The optical axis of each spectral channel 1704 is generally perpendicular to the front surface 1723 of the monolithic semiconductor chip 1724.

The optical filter 1712 of each spectral channel 1704 is formed on, or attached to, the front surface 1723 of the monolithic semiconductor chip 1724 over, or in front of, the corresponding optical detector arrangement 1714.

Each spectral channel 1704 defines a corresponding optical path extending from the corresponding lens element 1710 to the corresponding optical detector arrangement 1714.

One of ordinary skill in the art will understand that the sectored-view multi- spectral ALS 1702 of FIG. 17 is similar to the sectored-view multi-spectral ALS 302 of FIG. 3, but that the sectored-view multi-spectral ALS 1702 of FIG. 17 does not include any solid transparent material disposed on the optical filters 1712 of the different spectral channels 1704. Instead, and, as a consequence of the stepped profile of the front surface 1734 of the substrate 1732 of the MLA 1730, each spectral channel 1704 corresponds to a region of the substrate 1732 of the MLA 1730 having a different thickness and different spectral channels 1704 have different optical path lengths, wherein the optical path length of each spectral channel 1704 is selected so as to at least partially compensate for the chromatic aberration of the corresponding lens element 1710.

In other respects, the sectored-view multi-spectral ALS 1702 of FIG. 17 is similar to the sectored-view multi-spectral ALS 302 of FIG. 3 and the operation of the sectored-view multi-spectral ALS 1702 of FIG. 17 is similar to the operation of the sectored-view multi-spectral ALS 302 of FIG. 3.

Referring now to FIG. 18, there is shown a sixteenth multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 1802. The sectored-view multi-spectral ALS 1802 of FIG. 18 is essentially the same as the sectored-view multi- spectral ALS 1702 of FIG. 17 except that in the sectored-view multi-spectral ALS 1802 of FIG. 18, an optical filter 1812 of each spectral channel 1804 is formed on, or attached to, a front surface 1834 of a transparent substrate 1832 of a M LA 1830. One of ordinary skill in the art will understand that the operation of the sectored-view multi- spectral ALS 1802 of FIG. 18 is similar to the operation of the sectored-view multi- spectral ALS 1702 of FIG. 17.

Referring now to FIG. 19, there is shown a seventeenth multi-spectral optical sensor in the form of a sectored-view multi-spectral ALS 1902. The sectored-view multi-spectral ALS 1902 of FIG. 19 is essentially the same as the sectored-view multi- spectral ALS 1702 of FIG. 17 except that in the sectored-view multi-spectral ALS 1902 of FIG. 19, an optical filter 1912 of each spectral channel 1904 is formed on, or attached to, a generally planar rear surface 1936 of a transparent substrate 1932 of a MLA 1930 and each lens element 1910 of the MLA 1930 is formed over, or attached to, the corresponding optical filter 1912. One of ordinary skill in the art will understand that the operation of the sectored-view multi-spectral ALS 1902 of FIG. 19 is similar to the operation of the sectored-view multi-spectral ALS 1702 of FIG. 17.

Referring now to FIGS. 20A and 20B, there is shown an eighteenth multi- spectral optical sensor in the form of a sectored-view multi-spectral ALS 2002 which defines a plurality of spectral channels 2004. Each spectral channel 2004 comprises a corresponding aperture 2008, a corresponding lens element 2010, a corresponding optical filter 2012 and a corresponding optical detector arrangement 2014, wherein the aperture 2008, the lens element 2010, the optical filter 2012 and the optical detector arrangement 2014 of each spectral channel 2004 are aligned along a corresponding optical axis.

The lens elements 2010 of the plurality of spectral channels 2004 are defined by a MLA generally designated 2030, wherein the MLA 2030 comprises a transparent substrate 2032, and wherein the lens elements 2010 are disposed on a front surface 2034 of the substrate 2032.

As shown most clearly in FIG. 20B, the optical detector arrangement 2014 of each spectral channel 2004 comprises an array of optical detector regions 2022 of a monolithic semiconductor chip 2024, wherein the optical detector regions 2022 are formed adjacent to a front surface 2023 of the monolithic semiconductor chip 2024, and wherein each array of optical detector regions 2022 has the same number and relative spatial arrangement of optical detector regions 2022 as each of the other arrays of optical detector regions 2022. The optical axis of each spectral channel 2004 is generally perpendicular to the front surface 2023 of the monolithic semiconductor chip 2024.

The optical filter 2012 of each spectral channel 2004 is formed on, or attached to, the front surface 2023 of the monolithic semiconductor chip 2024 over, or in front of, the corresponding optical detector arrangement 2014.

Referring back to FIG. 20A, each spectral channel 2004 defines a corresponding optical path extending from the corresponding lens element 2010 to the corresponding optical detector arrangement 2014. The sectored-view multi-spectral ALS 2002 further includes different thicknesses of solid transparent material 2050 in the optical paths of the different spectral channels 2004 so that the optical paths of the different spectral channels 2004 have different optical path lengths and the thickness of solid transparent material 2050 in each spectral channel 2004 is selected so as to at least partially compensate for the chromatic aberration of the corresponding lens element 2010.

The different thicknesses of solid transparent material 2050 are provided in the form of a solid transparent member 2060 which defines a stepped profile on a front surface 2062 thereof, wherein the stepped profile includes a plurality of step regions, and wherein each step region is located in the optical path of a corresponding spectral channel 2004.

The solid transparent member 2060 may comprise a solid transparent substrate 2066 and the different thicknesses of solid transparent material 2050 may be formed on, deposited on, or applied to, a front surface 2068 of the solid transparent substrate 2066. For example, the different thicknesses of solid transparent material 2050 may be defined by forming, depositing, or applying, an initial layer of solid transparent material 2050 on the front surface 2068 of the solid transparent substrate 2066 and then applying one or more subsequent layers of solid transparent material 2050 on the initial layer of solid transparent material 2050, wherein each subsequent layer of solid transparent material 2050 is disposed on a different area of the preceding layer of solid transparent material 2050 so as to define the stepped profile on the front surface 2062 of the solid transparent member 2060.

The front surface 2062 of the solid transparent member 2060 is separated from the monolithic semiconductor chip 2024 by a gap. A rear surface 2064 of the solid transparent substrate 2066 of the solid transparent member 2060 is generally planar and is separated from the MLA 2030 by a gap. The sectored-view multi-spectral ALS 2002 further comprises an aperture member 2070, wherein the different apertures 2008 of the different spectral channels 2004 are defined in the aperture member 2070.

The sectored-view multi-spectral ALS 2002 further comprises a base member 2080, such as a PCB, and a housing 2082. The monolithic semiconductor chip 2024 and the housing 2082 are mounted on the base member 2080. The monolithic semiconductor chip 2024, the solid transparent member 2060, the MLA 2030 and the aperture member 2070 are held in alignment relative to one another by the base member 2080 and the housing 2082.

From the foregoing description, one of ordinary skill in the art will understand that the sectored-view multi-spectral ALS 2002 of FIGS. 20A and 20B is very similar to the sectored-view multi-spectral ALS 602 of FIG. 6. Like the sectored-view multi- spectral ALS 602 of FIG. 6, in the sectored-view multi-spectral ALS 2002 of FIGS. 20A and 20B, the monolithic semiconductor chip 2024, the solid transparent member 2060, and the MLA 2030 are configured and/or arranged so that light in the different spectral channels 2004 is focussed to the same focal plane. However, unlike the sectored-view multi-spectral ALS 602 of FIG. 6 in which the monolithic semiconductor chip 624, the solid transparent member 660, and the MLA 630 are configured and/or arranged so that light in the different spectral channels 604 is focussed to a focal plane coinciding with the plane of the different optical detector arrangements 614 of the different spectral channels 604, in the sectored-view multi-spectral ALS 2002 of FIGS. 20A and 20B, the monolithic semiconductor chip 2024, the solid transparent member 2060, and the MLA 2030 are configured and/or arranged so that light in the different spectral channels 2004 is focussed to a focal plane which is offset from the plane of the different optical detector arrangements 2014 of the different spectral channels 2004. For example, the monolithic semiconductor chip 2024, the solid transparent member 2060, and the MLA 2030 may be configured and/or arranged so that light in the different spectral channels 2004 is focussed to a focal plane which is located axially between the front surface 2062 of the solid transparent member 2060 and the optical filters 2012 formed on, or attached to, the front surface 2023 of the monolithic semiconductor chip 2024. In other embodiments, the monolithic semiconductor chip 2024, the solid transparent member 2060, and the MLA 2030 are configured and/or arranged so that light in the different spectral channels 2004 is focussed to a focal plane which is located axially below the different optical detector arrangements 2014 of the different spectral channels 2004. Defocussing the light incident on the optical detector arrangements 2014 in this way may have advantages for spectral reconstruction. Regardless of the exact location of the focal plane relative to the plane of the optical detector arrangements 2014, one of ordinary skill will understand that the use of the solid transparent member 2060 at least partially compensates for the chromatic aberration of the lens elements 2010. Moreover, the step regions of the front surface 2062 of the solid transparent member 2060 are more easily aligned relative to the different lens elements 2010 and the different optical detector arrangements 2014 of the different spectral channels 2004 compared with the use of an additional lens element in each spectral channel.

In other respects, the sectored-view multi-spectral ALS 2002 of FIGS. 20A and 20B is identical to the sectored-view multi-spectral ALS 602 of FIG. 6. Consequently, one of ordinary skill in the art will understand that the operation of the sectored-view multi-spectral ALS 2002 of FIGS. 20A and 20B is similar to the operation of the sectored-view multi-spectral ALS 602 of FIG. 6.

Referring now to FIG. 21 , there is shown a multi-spectral optical emitter arrangement 2102 which defines a plurality of spectral channels 2104. Each spectral channel 2104 comprises a corresponding optical emitter 2114 and a corresponding lens element 2110, wherein the optical emitter 2114 and the corresponding lens element 2110 are aligned along a corresponding optical axis. The optical emitters 2114 of the different spectral channels 2104 have different optical emission spectra such as different narrowband optical emission spectra. The optical emitters 2114 may, for example, comprise LED’s or lasers.

The optical emitters 2114 may be mounted on, or formed monolithically in, a base member 2124, wherein the optical emitters 2114 are disposed adjacent to, or on, a front surface 2123 of the base member 2124. The optical axis of each spectral channel 2104 is generally perpendicular to the front surface 2123 of the base member 2124.

The lens elements 2110 of the plurality of spectral channels 2104 are defined by a M LA generally designated 2130, wherein the M LA 2130 comprises a transparent substrate 2132, and wherein the lens elements 2110 are disposed on a front surface 2134 of the substrate 2132.

Each spectral channel 2104 defines a corresponding optical path extending from the corresponding optical emitter 2114 to the corresponding lens element 2110.

The multi-spectral optical emitter arrangement 2102 includes different thicknesses of solid transparent material 2150 in the optical paths of the different spectral channels 2104 so that the optical paths of the different spectral channels 2104 have different optical path lengths. Specifically, different thicknesses of solid transparent material 2150 are disposed on the front surface 2123 of the base member 2124 over, or in front of, the optical emitters 2114 so as to define a stepped profile on a front surface 2152 of the solid transparent material 2150, wherein the stepped profile includes a plurality of step regions, and wherein each step region is located in the optical path of a corresponding spectral channel 2104.

The different thicknesses of solid transparent material 2150 may be formed on, deposited on, or applied to, the front surface 2123 of the base member 2124 over, or in front of, the optical emitters 2114. For example, the different thicknesses of solid transparent material 2150 may be defined by forming, depositing, or applying, an initial layer of solid transparent material 2150 on the front surface 2123 of the base member 2124 over, or in front of, the optical emitters 2114 and then applying one or more subsequent layers of solid transparent material 2150 on the initial layer of solid transparent material 2150, wherein each subsequent layer of solid transparent material 2150 is disposed on a different area of the preceding layer of solid transparent material 2150 so as to define the stepped profile on the front surface 2152 of the solid transparent material 2150.

Alternatively, the multi-spectral optical emitter arrangement 2102 may comprise a solid transparent member which includes, or which is formed from, the solid transparent material 2150, wherein a rear surface 2154 of the solid transparent member is attached, for example, bonded to the front surface 2123 of the base member 2124 over, or in front of, the optical emitters 2114, wherein the solid transparent member comprises a plurality of regions, each region having a different thickness so as to define the stepped profile on the front surface 2152 of the solid transparent member.

Moreover, each step region of the solid transparent material 2150 has a corresponding constant thickness of the solid transparent material 2150 across the step region, wherein the thickness is selected so as to at least partially compensate for the chromatic aberration of the corresponding lens element 2110.

In use, the different optical emitters 2114 emit light of different wavelengths or different ranges of wavelengths. The different thicknesses of solid transparent material 2150 in the different spectral channels 2104 at least partially compensate for the chromatic aberration of the different lens elements 2110 so that each lens element 2110 collimates the light emitted from the corresponding optical emitter 2114 or at least approximately collimates the light emitted from the corresponding optical emitter 2114.

At least partially compensating for the chromatic aberration of the lens elements 2110 in the different spectral channels 2104 improves the collimation of the beams of light emitted from the multi-spectral optical emitter arrangement 2102.

Moreover, it may be simpler and cheaper to form or attach the solid transparent material 2150 to the front surface 2123 of base member 2124 so as to at least partially compensate for the chromatic aberration of the lens elements 2110, than to use two or more lens elements in each spectral channel 2104 so as to at least partially compensate for the chromatic aberration of the lens elements 2110. Furthermore, as a consequence of the constant thickness of each region of the solid transparent material 2150, the precision with which the stepped profile of the solid transparent material 2150 needs to be aligned relative to the base member 2124 and the M LA 2130 may be less than the (sub-micron) alignment precision required to align two or more lens elements in each spectral channel relative to one another and relative to the base member 2124 such that the complexity and cost of manufacturing such a multi-spectral optical emitter arrangement 2102 may be less than the complexity and cost of manufacturing a multi- spectral optical emitter arrangement having two or more lens elements in each spectral channel.

One of ordinary skill in the art will understand that in a variant of the multi- spectral optical emitter arrangement 2102 of FIG. 21 , solid transparent material may be provided in each spectral channel by inserting a solid transparent member like the solid transparent member 660 of FIG. 3 or the solid transparent member 1060 of FIG. 10 into the optical path between the optical emitters 2114 and the MLA 2130 so as to at least partially compensate for the chromatic aberration of the lens elements 2110.

Additionally or alternatively, the MLA 2130 may be modified so that the substrate 2132 of the MLA 2130 defines a stepped profile on a front surface 2134 thereof and so that each lens element is defined in a different step region of the step profile like the MLA 1430 of FIG. 14.

Additionally or alternatively, the MLA 2130 may be modified so that the substrate 2132 of the MLA 2130 defines a stepped profile on a front surface 2134 thereof and so that each lens element is defined on a rear surface of the MLA like the MLA 1730 of FIG. 17.

One of ordinary skill in the art will also understand that various modifications are possible to any of the multi-spectral ALS described above. For example, the optical filters of the different spectral channels may be disposed on a stepped profile defined in a surface of solid transparent material, such as a surface of a solid transparent member, located in the different spectral channels. The optical filters of the different spectral channels may be disposed on a surface of the solid transparent member which is disposed towards the different optical detector arrangements or the monolithic semiconductor chip.

Although each of the multi-spectral optical sensors 302, 402, 502, 602, 702, 802, 902, 1002, 1102, 1202, 1302, 1402, 1502, 1602, 1702, 1802, 1902, 2002 is described above with reference to FIGS. 3 to 20B as a sectored-view multi-spectral ALS, any of the multi-spectral optical sensors 302, 402, 502, 602, 702, 802, 902, 1002, 1102, 1202, 1302, 1402, 1502, 1602, 1702, 1802, 1902, 2002 may be configured for use in a different context or for a different technical field of use. For example, any of the multi-spectral optical sensors 302, 402, 502, 602, 702, 802, 902, 1002, 1102, 1202, 1302, 1402, 1502, 1602, 1702, 1802, 1902, 2002 may be configured for use as a multi- spectral camera. For example, any of the multi-spectral optical sensors 302, 402, 502, 602, 702, 802, 902, 1002, 1102, 1202, 1302, 1402, 1502, 1602, 1702, 1802, 1902, 2002 may include a plurality of spectral channels, wherein each spectral channel includes a corresponding optical detector arrangement in the form of a 2D array of optical detector regions of a monolithic semiconductor chip, wherein the 2D array of optical detector regions has a first dimension that comprises many more than several, for example one hundred or more or one thousand or more, optical detector regions, and a second dimension that comprises many more than several, for example one hundred or more or one thousand or more, optical detector regions. In such a multi- spectral camera, each 2D array of optical detector regions may be, or may comprise, an image sensor array. Such a multi-spectral camera may be configured and/or used for humidity or tissue analysis.

Any of the multi-spectral optical sensors 302, 402, 502, 602, 702, 802, 902, 1002, 1102, 1202, 1302, 1402, 1502, 1602, 1702, 1802, 1902, 2002 may be configured for operation at one or more wavelengths in an ultraviolet (UV), a visible (VIS), a nearinfrared (NIR), a short-wavelength infrared (SWIR) or a mid-infrared (MIR) wavelength range and the lens element, the optical filter and the optical detector arrangement of each spectral channel of each multi-spectral optical sensor 302, 402, 502, 602, 702, 802, 902, 1002, 1102, 1202, 1302, 1402, 1502, 1602, 1702, 1802, 1902, 2002 may be configured accordingly. Although the disclosure has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives to the described embodiments in view of the disclosure which are contemplated as falling within the scope of the appended claims. Each feature disclosed or illustrated in the present specification may be incorporated in any embodiment, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein. In particular, one of ordinary skill in the art will understand that one or more of the features of the embodiments of the present disclosure described above with reference to the drawings may produce effects or provide advantages when used in isolation from one or more of the other features of the embodiments of the present disclosure and that different combinations of the features are possible other than the specific combinations of the features of the embodiments of the present disclosure described above.

The skilled person will understand that in the preceding description and appended claims, positional terms such as ‘above’, ‘along’, ‘side’, etc. are made with reference to conceptual illustrations, such as those shown in the appended drawings. These terms are used for ease of reference but are not intended to be of limiting nature. These terms are therefore to be understood as referring to an object when in an orientation as shown in the accompanying drawings.

Use of the term "comprising" when used in relation to a feature of an embodiment of the present disclosure does not exclude other features or steps. Use of the term "a" or "an" when used in relation to a feature of an embodiment of the present disclosure does not exclude the possibility that the embodiment may include a plurality of such features.

The use of reference signs in the claims should not be construed as limiting the scope of the claims.

LIST OF REFERENCE NUMERALS

2 sectored-view multi-spectral ambient light sensor (ALS);

4 spectral channel;

10 lens element;

12 optical filter;

14 optical detector arrangement;

22 optical detector region;

24 monolithic semiconductor chip;

30 microlens array;

32 transparent substrate of microlens array;

34 front surface of substrate of microlens array;

40 spacer;

42 aperture;

102 sectored-view multi-spectral ambient light sensor (ALS);

104 spectral channel;

110 lens element;

112 optical filter;

114 optical detector arrangement;

122 optical detector region;

123 front surface of monolithic semiconductor chip;

124 monolithic semiconductor chip;

130 microlens array;

132 transparent substrate of microlens array;

134 front surface of substrate of microlens array;

202 sectored-view multi-spectral ambient light sensor (ALS);

204 spectral channel;

210 lens element;

212 optical filter;

214 optical detector arrangement;

222 optical detector region;

223 front surface of monolithic semiconductor chip;

224 monolithic semiconductor chip; 230 microlens array;

232 transparent substrate of microlens array;

234 front surface of substrate of microlens array;

302 sectored-view multi-spectral ambient light sensor (ALS);

304 spectral channel;

310 lens element;

312 optical filter;

314 optical detector arrangement;

323 front surface of monolithic semiconductor chip;

324 monolithic semiconductor chip;

330 microlens array;

332 transparent substrate of microlens array;

334 front surface of substrate of microlens array;

350 solid transparent material;

352 front surface of solid transparent material;

354 rear surface of solid transparent material;

402 sectored-view multi-spectral ambient light sensor (ALS);

404 spectral channel;

410 lens element;

412 optical filter;

430 microlens array;

432 transparent substrate of microlens array;

434 front surface of substrate of microlens array;

502 sectored-view multi-spectral ambient light sensor (ALS);

504 spectral channel;

510 lens element;

512 optical filter;

530 microlens array;

532 transparent substrate of microlens array;

534 front surface of substrate of microlens array;

536 rear surface of substrate of microlens array; 602 sectored-view multi-spectral ambient light sensor (ALS);

604 spectral channel;

610 lens element;

612 optical filter;

614 optical detector arrangement;

623 front surface of monolithic semiconductor chip;

624 monolithic semiconductor chip;

630 microlens array;

632 transparent substrate of microlens array;

634 front surface of substrate of microlens array;

660 solid transparent member;

662 front surface of solid transparent member;

664 rear surface of solid transparent member;

702 sectored-view multi-spectral ambient light sensor (ALS);

704 spectral channel;

712 optical filter;

760 solid transparent member;

764 rear surface of solid transparent member;

802 sectored-view multi-spectral ambient light sensor (ALS);

804 spectral channel;

810 lens element;

812 optical filter;

830 microlens array;

832 transparent substrate of microlens array;

834 front surface of substrate of microlens array;

902 sectored-view multi-spectral ambient light sensor (ALS);

904 spectral channel;

910 lens element;

912 optical filter;

930 microlens array;

932 transparent substrate of microlens array;

936 rear surface of substrate of microlens array; 1002 sectored-view multi-spectral ambient light sensor (ALS);

1004 spectral channel;

1010 lens element;

1012 optical filter;

1014 optical detector arrangement;

1050a first solid transparent material;

1050b second solid transparent material;

1050c third solid transparent material;

1060 solid transparent member;

1062 front surface of solid transparent member;

1064 rear surface of solid transparent member;

1102 sectored-view multi-spectral ambient light sensor (ALS);

1104 spectral channel;

1112 optical filter;

1160 solid transparent member;

1164 rear surface of solid transparent member;

1202 sectored-view multi-spectral ambient light sensor (ALS);

1204 spectral channel;

1210 lens element;

1212 optical filter;

1230 microlens array;

1232 transparent substrate of microlens array;

1234 front surface of substrate of microlens array;

1302 sectored-view multi-spectral ambient light sensor (ALS);

1304 spectral channel;

1312 optical filter;

1330 microlens array;

1332 transparent substrate of microlens array;

1336 rear surface of substrate of microlens array;

1402 sectored-view multi-spectral ambient light sensor (ALS); 1404 spectral channel;

1410 lens element;

1412 optical filter;

1414 optical detector arrangement;

1423 front surface of monolithic semiconductor chip;

1424 monolithic semiconductor chip;

1430 microlens array;

1432 transparent substrate of microlens array;

1434 front surface of substrate of microlens array;

1502 sectored-view multi-spectral ambient light sensor (ALS);

1504 spectral channel;

1510 lens element;

1512 optical filter;

1530 microlens array;

1532 transparent substrate of microlens array;

1534 front surface of substrate of microlens array;

1602 sectored-view multi-spectral ambient light sensor (ALS);

1604 spectral channel;

1612 optical filter;

1630 microlens array;

1632 transparent substrate of microlens array;

1636 rear surface of substrate of microlens array;

1702 sectored-view multi-spectral ambient light sensor (ALS);

1704 spectral channel;

1710 lens element;

1712 optical filter;

1714 optical detector arrangement;

1723 front surface of monolithic semiconductor chip;

1724 monolithic semiconductor chip;

1730 microlens array;

1732 transparent substrate of microlens array;

1734 front surface of substrate of microlens array; 1736 rear surface of substrate of microlens array;

1802 sectored-view multi-spectral ambient light sensor (ALS);

1804 spectral channel;

1812 optical filter;

1830 microlens array;

1832 transparent substrate of microlens array;

1834 front surface of substrate of microlens array;

1902 sectored-view multi-spectral ambient light sensor (ALS);

1904 spectral channel;

1910 lens element;

1912 optical filter;

1930 microlens array;

1932 transparent substrate of microlens array;

1936 rear surface of substrate of microlens array;

2002 sectored-view multi-spectral ambient light sensor (ALS);

2004 spectral channel;

2008 aperture;

2010 lens element;

2012 optical filter;

2014 optical detector arrangement;

2022 optical detector region;

2023 front surface of monolithic semiconductor chip;

2024 monolithic semiconductor chip;

2030 microlens array;

2032 transparent substrate of microlens array;

2034 front surface of substrate of microlens array;

2060 solid transparent member;

2062 front surface of solid transparent member;

2064 rear surface of solid transparent member;

2066 solid transparent substrate of solid transparent member;

2068 front surface of substrate of solid transparent member;

2070 aperture member 2080 base member;

2082 housing;

2102 multi-spectral optical emitter arrangement;

2104 spectral channel;

2110 lens element;

2114 optical emitter;

2123 front surface of base member;

2124 base member;

2150 solid transparent material;

2152 front surface of solid transparent material; and

2154 rear surface of solid transparent material.