Technical Field

This invention relates to a camera adapter, and in particular to a camera adapter and method for photographing an iris.

Background of the Invention

Images of the human iris are photographed for several different purposes, including for biometric identification, medical imaging, and artistic benefit. Traditionally, images of the iris are taken with a standard photographic camera. A problem with capturing an image of an iris in this way is that several reflections on the iris are often apparent on the image. These reflections are due to the highly reflective nature of the human eye, as well as its rounded shape. In particular, the shape of the human eye means that reflections can occur from light sources in a wide field of view. This can make it difficult to locate and remove the source of the reflections appearing in the image of the iris. Since capturing images of the human iris requires light, and darker iris colours usually require even more light, the problem of specular reflections in the iris is difficult to solve.

Attempts to solve this problem include overlaying an image taken in the visible spectrum of light with an image taken at infrared wavelengths, or similarly, using a light filter that is transparent to infrared light as is disclosed in published international patent application WO2015131 198 (A1). However, systems including an infrared camera are often more expensive and detail with regard to the different visible colours of the iris is diminished when an image is taken in this way.

We have appreciated that it would be desirable to provide a camera adapter and method for capturing images of the human iris in the visible spectrum that solves the problem of undesirable specular reflections in the iris.

Summary of the Invention

The invention is defined in the independent claims to which reference should now be made. Advantageous features are set forth in the dependent claims.

According to one aspect of the invention, there is an adapter for a camera device, the adapter comprising: an elongate adapter body formed of a material that is opaque to visible light and that has a first end for connecting to a camera device and a second end for placing in contact with a subject's face over a subject's eye in order to take a picture, wherein the adapter body is prism shaped or cylindrical, and the interior of the adapter body and each of the first and second ends is transparent to visible light, an illumination section adapted to be connected to the adapter body at the first end, the illumination section having one or more light sources and defining a first transparent section transparent to visible light, wherein the one or more light sources are arranged on the periphery of the first transparent section; the first transparent section being concentrically aligned with the first end of the adapter body when the illumination section is connected to the adapter body, such that the subject's eye is visible through the adapter body from the first end, and wherein the length of the elongate body and the position of the one or more light sources within the adapter body when the illumination section is connected are configured such that the reflection from the one or more light sources in the subject's eye falls entirely within the pupil of the subject's eye when the camera device is used to take a picture of the subject's eye through the elongate adapter body.

According to another aspect of the invention, there is a method for capturing an image of an iris, the method comprising: using a camera device with a camera adapter, aligning one end of the camera adapter with a human eye in a concentric manner;

activating a light source within the camera adapter; capturing an image of the human eye with the camera device, wherein reflections from the light source that are apparent in the image are contained within the pupil of the human eye.

Brief Description of the Drawings

Examples of the invention will now be described in more detail, by way of example, and with reference to the drawings in which:

Figure 1 is a rear isometric view of the invention according to a preferred embodiment;

Figure 2 is a front isometric view of the invention according to the preferred embodiment of Figure 1 ;

Figure 3 is a front exploded view of the invention according to the preferred embodiment of Figure 1 ;

Figure 4 is a top view of the invention according to the preferred embodiment of Figure 1 , in operation on a human iris;

Figure 5 is a front cross-sectional view of the invention according to the preferred embodiment of Figure 1 ;

Figure 6 is a block diagram comprising method steps for working the invention according to the preferred embodiment.

Detailed Description of the Preferred Embodiments

A preferred embodiment of the invention will now be described with reference to the Figures. Figures 1 and 2 show rear and front isometric views of the camera adapter 100 according to the present invention. The camera adapter 100 comprises a body portion 102. The body portion 102 is substantially hollow in order to allow the passage of light within the body portion 102, and has an opening 108 at the front end, and an opening 109 at the rear end. The exterior surface 106 of the body portion 102 is substantially opaque so light cannot travel through the surface 106.

The body portion 102 is tubular and may be made from plastic, metal or any other substantially rigid material.

The body portion 102 comprises a grip 11 1 on the exterior surface 106. The grip 1 11 is formed of a repeating pattern of rectangular shaped protrusions in an outwards direction from the surface 106. The body portion 102 also comprises a securing means 107 in the vicinity of the perimeter of opening 109, for securing the body portion 102 to a detachable, end connector ring 1 14 and to an interior light source housing 112.

The body portion 102 further comprises an eyepiece 120 at the front end of the camera adapter, as shown in Figures 1 and 2. The eyepiece 120 is placed on the perimeter of the opening 108. The eyepiece 120 may be made from rubber, foam, PVC or any other material suitable for contact with the area of a person's face around the eye. The eyepiece 120 is therefore made of substantially smooth and comfortable material. The eyepiece 120 is relatively thicker in comparison to the thickness of exterior surface 106 of the body portion 102, such that the eyepiece 120 protrudes in an outwards direction from the surface 106.

The opening 108 formed by at the front end of the body portion 102 and the eyepiece 120 is shaped to fit the area around a human eye. In particular, the shape of the eyepiece 120 and the body portion 102 allows for a snug fit on a human face, such that contact with a subject's face around the eye acts to substantially close or cover opening 108. This means that during use, light is restricted from entering the body portion 102 through the opening 108.

The shape of opening 108 is substantially circular, with a portion of the wall that defines the opening 108 protruding further outwards from the body portion 102, such that it is elongated with respect to the rest of the wall and forms a 3D curvature, with a

component of curvature in the direction of the concentric axis of the body portion 102. The shape of the opening 108 can be achieved by 3D printing, moulding or the like.

The interior surface of the body portion 1 18 can also be seen in Figure 2. The interior surface 118 of the body portion 102 is coloured black and made from material with light dampening qualities. Materials which have light dampening qualities include felt, foam or the like. The interior surface 1 18 may also be matte to further enhance its light dampening qualities.

As can be seen more clearly in the exploded view of Figure 3, the camera adapter

100 comprises an end connector ring 1 14 for securing the camera adapter 100 to a filter thread around a lens on the front of a camera, and an interior light source housing 1 12. The body portion 102 is removably detachable from the end connector ring 114. In particular, the threaded end connector ring 114 can be screwed onto the securing means 107 around the opening 109 of the body portion 102.

The interior light source housing 1 12 is positioned between a circular flange 115 located in the interior of the body portion 102 and the opening 109 of the body portion 102 when in use. The flange 115 prevents the light source housing from moving down the tube of the body portion 102. The position of the light source housing 112 is kept secure during use by the flange 1 15 on one side and the threaded end connector ring 1 14 on the opposite side. In other words, the light source housing 112 is securely accommodated between the flange 1 15 and the threaded end connector 114 during use to prevent substantial movement of the light source housing 1 12. To accommodate the light source housing 112 more securely, the end connector ring is provided with an annular recess in which the light source housing is contained.

The light source housing 112 itself comprises a diffuser. The diffuser comprises a circular transparent trough. In particular, the diffuser includes two concentric tubular portions, joined together at one end by a ring shaped plate. The two tubular portions are annular, wherein one tubular portion has a smaller circumference than the other. The plate that joins the tubular portions is fitted in the space between them when they are aligned in a concentric manner. In use, the light source is fitted between the two tubular portions and against the plate that joins them. It is to be understood that the dimensions of the space between the tubular portions should be approximately equal to the thickness of the light source. The light source housing 112 is transparent so that light from the light source can easily travel through the light source housing 1 12 when in use.

The end connector ring connects to the body portion 102 via securing means 107 on one side, and to the lens of a camera device on the other side. The end connector ring 114 is annular and substantially opaque.

It is to be understood that the end connector ring 1 14 is designed to be compatible standard filter thread diameters on digital single-lens reflex cameras, but can be modified to connect to the lens of any camera device capable of capturing images.

The light source itself (not shown in Figures 1 to 3) is annular and comprises a light emitting element. The light emitting element may be a continuous light emitting ring or a plurality of individual light emitting devices arranged in a circular pattern. The light emitting devices or continuous light emitting ring may be comprised of Light Emitting Diodes (LEDs), Compact Fluorescent Lamps (CFLs), or any other source of incandescence or luminescence. The inner and outer circumference of the light source should be greater than the circumference of the inner tube of the light source housing 112, but smaller than the circumference of the outer tube of the light source housing 1 12, so that the light source can fit in the light source housing 1 12 and the body portion 102. The light source 122 may be powered by an internal battery, or an external battery. In the case wherein the battery is external, the body portion 102 includes a groove or through-hole 1 16. The groove or through-hole may be any reasonable shape for allowing electrical wiring through the body portion 102. Preferably the groove or through-hole 116 is similar in size to the diameter of the wiring, so as to minimise the amount of light entering the interior of the camera adapter system 100.

The light source housing 1 12, the end connector ring 1 14 and the light source all comprise an aperture or opening 110. When the camera adapter 100 is fully assembled, the openings 108, 109 and 110 are substantially concentric, such that light can pass from opening 108 through opening 110 and vice-versa.

When the camera adapter 100 is assembled and then connected to a camera device via the threaded end connector ring, the lens of the camera device is substantially aligned in a concentric manner with the opening 108, 109 and 110.

Figure 4 shows an embodiment of a camera adapter 100 according to the present invention, and how it may be positioned relative to a human eye whilst in use. The apparatus and a method for capturing an image of an iris are described here.

In operation, the light source is securely housed in the light source housing 112. The camera adapter 100 is connected to a camera device capable of capturing

photographic images, such as a digital camera or a smartphone, via a connection between the end connector ring 1 14 and the camera device. The connection between the camera adapter 100 and the camera is non-permanent, meaning the camera and the adapter 100 are removably detachable from each other. The connection is made such that the lens of the camera is concentric with the opening 1 10 in the end connector ring 114 and the light source housing 1 12, the opening at the back of the body portion 109, and the opening at the front of the body portion 108.

To capture an image of a human iris 124, the camera is positioned such that the camera lens and the openings 108, 109 and 1 10 of the connected camera adapter 100 are concentrically aligned with the human eye as seen in Figure 5. The body portion 102 is positioned with respect to the person such that the eyepiece 120 engages the person's face, or at least comes into close proximity with the person's face. The close proximity of the eyepiece 120 with the person's face minimises the amount of light that can enter the camera adapter 100 from the opening 108 at the front end. The body portion 102 is also aligned such that the curvature of the opening 108 substantially matches the curvature of the person's face. In other words, the elongated portion of the wall that forms the opening 108 should be positioned towards the person's ear which is closest to the eye which is being photographed. In this way, the 3D curvature of the opening 108 should substantially follow the curvature of the person's face. In order to align the elongated part of the wall that forms opening 108 with the person's face, the body portion 102 or the end connector ring 114 or the connection that connects the connector ring 1 14 to the camera, may be rotatable around the central concentric axis of the camera adapter 100. Hence, the body portion 102 can be rotated without a need to rotate the connected digital camera/ smartphone.

Alternatively, the connections between the body portion 102 and the end connector ring 114, or the camera adapter 100 and the camera may be configured such that when these parts are connected together, the elongated portion of the opening 108 is

automatically in the correct position. This can be realised by specifically positioning the threading that forms the connections so that when the parts are screwed and/or locked together, the camera adapter 100 is aligned correctly with respect to the camera and with respect to the person's face.

Once the opening 108 is aligned correctly with the person's eye and the eyepiece 120 is within close proximity to the person's face, the light source is turned on. The light source may have an internal power source and internal wiring, connected to a control such as a button and/or dimmer switch located on the outer surface of the body portion 102.

Alternatively, wiring from the light source 122 may be fed out of the camera adapter 100 via a hole or groove 1 16 to an external power source. The external power source may be a battery or mains electricity, and may also feature an external set of controls such as a button or dimmer switch. The light source may be connected to a dimmer such that the brightness of the light source can be modified between a predetermined range when in use. The light source may be capable of providing 3000 Lumens or more of light, but should be limited to a brightness which does not damage or adversely affect the human eye. For instance, the light source may be rated at 1 15, 285 or 450 Im, or any intermediate brightness rating.

Alternatively, the controls may be separated from the power source. Furthermore, the light source may be controlled from the connectable camera/smartphone. The light source may connect to the camera/smartphone via a USB connection, Bluetooth, Wi-Fi or the like.

A user of the camera device, such as a camera or smartphone, can then control the brightness and illumination of the light source via the camera device control panel or touchpad.

In the case wherein the power source is an external battery, the power source is connectable to at least one of the camera adapter 100 and the camera/smartphone. In order to connect to the camera/smartphone, the external battery includes a default or universal means for connecting to regular camera/smartphone ports and fittings. For instance, the battery may include a fixed threaded bolt designed to connect to the standard tripod port in most digital cameras. In this way, the battery pack can be removably detachable from the camera, meaning the whole device, including the camera adapter 100 and the camera, can be mobile and portable without the need to carry a separate battery pack.

When turned on, the light source 122 illuminates the opening 108, and therefore the human iris 124 to be photographed. The body portion 102 comprises a light dampening material on its inner surface 118, which may also be black and matte, so as to reduce internal reflections within the body portion 102. Furthermore, the connection between the camera lens and the camera adapter 100 is substantially flush, so as to avoid any light pollution from opening 1 10. Additionally, the opening 108 should be substantially close to the face of the person who is to be photographed, to avoid light pollution. These

considerations all mean that the only light within the camera adapter 100 when in use should be from the housed light source 122.

Due to the specific dimensions of the light source 122 and the body portion 102, the reflections 126 from the light source 122 are arranged to be spatially contained within the pupil of the human eye once the image is captured. Specifically, the position of the reflections 126 from the light source 122 is dependent on a relationship that exists between the diameter of the annular light source 122 and the displacement of the light source 122 from the eye. The problem of specular reflections in the iris 124 has been considered and solved by determining this relationship and focusing the reflections 126 from the light source 122 within the pupil. The configuration of the camera adapter 100 allows the iris to be illuminated so that a clear image can be captured, without any specular reflections on the iris 124.

It is to be understood that since different cameras/smartphones have lenses of different diameters and fields of view, the dimensions of the light source 122 can be modified to accommodate these differences. The inner diameter of the light source 122 that forms the opening 1 10 should be equal to or greater than the diameter of the lens of the camera that is to be used to capture the image. The outer diameter of the light source 122 may be smaller or larger than 60mm, as long as the reflections 126 from the light emitted from the light source 122 are contained within the person's pupil.

In order to capture an image, the light source 122 is turned on and may be adjusted in terms of brightness through the application of a dimmer switch. For darker irises 124, it is useful to use a higher brightness setting. For lighter irises, such as blue irises, it is useful to select a lower brightness setting. Once the correct brightness setting has been selected, the camera is focused on the iris 124 and the camera is controlled to execute an image capturing function.

When an image of the iris 124 is captured, the reflections 126 are present in the pupil. Since human pupils are substantially black, the reflections 126 can be easily removed using simple image editing techniques. The image editing can be performed manually, by altering the RGB values of the pixels containing reflections 124 to substantially match surrounding pixels of the pupil that are unaffected by reflections 124. Other manual methods include overlaying the region of the image containing the reflections 124 with a region of black pixels, and subsequently blending the edges of the overlaid region with the remainder of the pupil. This manual process can be performed by the user or a third party. The third party may be a provider of relevant editing software for instance. In this case, the image is automatically uploaded to a server via the camera/smartphone or otherwise, and a third party can then edit the image, before returning the edited image to the user via the camera/smartphone or otherwise.

Alternatively, the editing process may be automatic. In this case, the editing process can be performed on the camera/smartphone or any other computer device, using image processing algorithms. These algorithms may include pattern recognition techniques, image segmentation/thresholding, edge detection, feature extraction algorithms or the like. Once the pupil has been edited to remove the reflections 126, further image editing may occur to enhance, expand or crop the image to show the detail in the iris. This can also be done automatically using similar algorithms and techniques.

Figure 5 shows the embodiment of a camera adapter 100 according to the present invention, from a cross-sectional perspective. In particular, figure 5 clearly shows the light source 122 disposed between the concentric tubes of the light source housing 1 12. Since the light source housing 112 is transparent, the light source 122 can be seen through it, from the eyepiece 120. Figure 5 also shows the concentric alignment of openings 108, 109 and 1 10, from position of the iris to the camera lens.

Figure 6 shows a block diagram comprising method steps for working the invention according to the preferred embodiment.

In step 601 , if the camera adapter 100 is not already assembled, a user of the camera adapter should assemble its components. This involves inserting the light source 122 into the light source housing 112, and inserting the light source housing 112 into the body portion 102 behind flange 115. The rear of the light source housing should be secured with the end connector ring 114, by connecting the end connector ring 1 14 to the body portion 102 using the securing means 107.

In step 602, the user of the camera adapter 100 should connect the adapter 100 with a camera/smartphone, via the attachment on the rear connector ring 114 and the standard lens connecting means of the camera device. This should be done such that the lens of the camera/smartphone and the openings 108, 109 and 1 10 of the camera adapter 100 are concentrically aligned. In this step, the user of the camera adapter may also connect the external battery to the base of the camera via a threaded port, in the case wherein the light source is powered by an external battery. In step 603, the user may position the camera and camera adapter 100 such that the eyepiece 120, or front opening 108 of the adapter, is positioned within close proximity to a target person's face. In particular, the adapter 100 should be positioned such that the target person's eye is concentrically aligned with the openings 108 109 and 1 10 of the adapter 100 and the lens of the camera/smartphone.

In step 604, the user turns on the light source 122 and adjusts the brightness of the light source if possible, using controls such as a dimmer switch, or the camera/smartphone controls. Darker pigments in the person's iris require brighter light in order to be seen properly in a captured image. Therefore, brightness is adjusted dependent on the colour of the target person's iris. Once a suitable brightness has been selected, the camera may be focused, and a photograph image captured. The image may include reflections 126 from the light source 122, but these will be contained within the image of the pupil.

Alternative embodiments according to the present invention are now described. It is to be understood that these embodiments are compatible with the preferred embodiment, meaning features of the following embodiments may be included or substituted for similar features in the preferred embodiment.

In one alternative embodiment, the camera adapter may comprise a body portion 102 that is substantially tubular, cylindrical, or any other regular or irregular prism shape. The body portion 102 may also be tapered at one end. The adapter also comprises a light source 122, a light source housing 1 12, and an end connector ring 1 14. These features may also have a prism shape.

The body portion 102 may include an inner section that is at least partially made of material that is transparent to visible light, and an outer surface 106 that is opaque to visible light.

The openings 108 and 109 of the body portion, on each end of its prism shape, may comprise lenses or other material that is transparent to visible light. The surface that separates the opaque surface 106 of the body portion and the interior transparent material, on the inside of the body portion 102, may include a material suitable for light dampening, such as foam, felt, or the like. Furthermore, the inside of the body portion 102 may be coloured black and may be matte, so that the reflective qualities of the inside of the body 102 are substantially diminished.

In another alternative embodiment, the camera adapter 100 comprises a body portion 102 and a light source 122, without the need for a housing for a light source 1 12. The light source 122 may comprise a securing means such as a threading, a clip mechanism, a zip or any other fastening suitable for connecting the body portion 102 to the light source 122. The light source 122 may be internal, and restricted by a flange 1 15 and the securing means, or could be external, in which case it is joined to opening 109 of the body portion 102 through the securing means. The end connector ring 114 connects to the light source 122 on one side and the lens of a camera device on the other side.

Alternatively, the light source 122 may comprise further securing means for securing the light source to the lens on the camera device. In this way, the light source connects on one side to the body portion 102 and on the other side to the camera device, meaning the end connector ring 1 14 is not required. The connection may be a thread on both sides of the light source 122, for example.

Alternatively still, the light source 122 and the body portion 102 may be permanently fixed to each other in the vicinity of the second opening 109. The permanent fixing between the body portion 102 and the light source 122 may be achieved by welding, screwing, gluing or any other process suitable for permanently fixing the body portion 102 and the light source 122. In this way, the camera adapter would be one fixed unit, capable of connecting to the camera device through a removably detachable connection.

In another alternative embodiment, the light source housing 112 is a different shape to the shape described for the preferred embodiment of the invention. In particular, the light source housing 112 may comprise two parallel rings, joined around the circumference of their inner apertures by a circular surface. The apertures of the two rings of the light source housing 1 12 may then form the opening 1 10. The parallel ring behind the light source 522 (in the direction of the lens of the camera device), may be opaque, in order to prevent light from travelling backwards in the adapter 100. On the contrary, the front parallel ring, which is between the light source and the iris, may be transparent, to let light through.

It is to be understood that a number of different ways to secure the light source at least for when it is in use are envisaged. The light source housing 112 may include a mechanism for connecting and securing the light source within the light source housing 1 12. Such a mechanism may allow the light source and the light source housing 112 to be removably detachable from each other. The mechanism for securely connecting the light source housing 112 and the light source could be a rotatable clip or a sliding lock for example. Alternatively, the mechanism could be the shape of the light source housing 1 12 itself. Specifically, the light source housing 1 12 could be made from an elastic material, with dimensions that are slightly smaller than the dimensions of the light source. The side walls of the light source housing 112 could be sufficiently flexible so as to expand to allow the insertion of the light source, but rigid enough so as to contract around the light source once it is positioned in place and provide a retaining force around the light source.

Alternatively, the walls of the light source housing 112 could be tapered such that it is sufficiently easy to push the light source into the light source housing 1 12, but more difficult to release the light source.

In these embodiments, the length dimensions of the camera adapter system may be, for example, approximately 98mm from opening 110 to opening 108 along the shortest edge of the body portion 102, and 136mm from the opening 110 to opening 108 along the elongated edge of the body portion 102. For these lengths, the width of the body portion may be approximately 72mm, and the light source may have an outer diameter of 60mm and an inner diameter of 14mm. The 60mm diameter of the light source 122 is the diameter of the outer circumference of the annular shape and the 44mm diameter of the light source 122 is the diameter of the inner circumference of the annular shape that effectively defines the aperture of the light source 122, which is the opening 109. The light emitting devices or continuous light ring element is disposed in the space between these two diameters. These dimensions are large enough such that the opening 109 does not obstruct the field of view of the lens of a digital camera when a digital camera is connected to the camera adapter system 100, and such that the reflections 126 from the light source 122 are contained within the person's pupil.

In an alternative embodiment wherein the camera adapter is designed for use on a smartphone, the camera adapter 100 may comprise a tapered prism shaped body portion, such that the opening 109 is substantially smaller than opening 108 and eyepiece 120. In this embodiment, light source 122 and end connecting ring 1 14 are smaller in diameter, due to the fact that the camera and lens of a smartphone are generally much smaller than the size and lens of a digital camera. In the absence of a threaded connection, the end connecting ring 114 comprises a clip to hook over at least one edge rim of the smartphone and securely retain the adapter in a removably fixed position over the smartphone lens, such that the lens and the openings 108 to 1 10 of the camera adapter are aligned in a concentric manner. In this embodiment of the camera adapter, the light source 122 can be substantially smaller and may not require as much power to operate. Therefore, the light source 122 may be electrically connected to the smartphone and hence draw power from the smartphone. Furthermore, this electrical connection may provide the smartphone with the control of the brightness of the light source 122.

In a further alternative embodiment relating to a camera adapter for a smartphone, the camera adapter is substantially the same size as the camera adapter 100 defined in the preferred embodiment. The camera adapter further includes a plurality of mirrors in an extension section protruding from the rear of the camera adapter, in the vicinity of opening 1 10 and the end connecting ring 114. The extension section comprises a plurality of opaque side portions including clips for engaging and hooking around the edges of the smartphone, such that the camera adapter is removably secured to the smartphone. The opaque side portions form an open section between the lens of the smartphone camera and the rear of the camera adapter. The camera adapter is aligned with the centre of the smartphone. The extension section comprises a plurality of mirrors located behind the light source and in the interior space defined by the side portions of the extension section and the rear of the camera adapter. One mirror is positioned behind the light source in a concentric manner with the openings 108 to 110 of the camera adapter. A second mirror is positioned in front of the field of view of the lens of the smartphone camera. These two mirrors are positioned in a periscope arrangement relative to each other, such that light from the opening 108 at the eyepiece 120 of the camera adapter, and hence light from the light source 122, reflected by an iris, can be detected via reflections from the two mirrors.