METHOD

The present invention relates to an optical vehicle environmental sensor, a vehicle comprising the optical vehicle environmental sensor, and a manufacturing method of a plurality of the optical vehicle environmental sensors.

Modern vehicles are equipped with an optical environmental sensor, also known as a rain sensor or a rain-light sensor, which is mounted to an inner side of a windscreen of the vehicle. A rain light sensing functionality of the optical environmental sensor transmits infrared light towards the windscreen and measures infrared light reflected back to the sensor. Based on the reflected infrared light, a degree of wetting of the windscreen is determined. Further optical functionality is commonly integrated into the rain-light sensor, such as ambient light sensing functionality, road illumination sensing functionality and the like. Each of the functionalities uses a different lens to focus light onto different respective light sensing elements of the sensor and/or to focus light emitted by different respective light emitting elements of the sensor. Conventionally optical elements, such as free-form optics or diffractive optics, including Fresnel lenses, are integrated into an optical-grade plastic housing that may be formed integrally in a multi-component moulding step or the like. A printed circuit board on which the light sensing elements and the light emitting elements are mounted is accommodated in the housing. Each optical element of the housing focuses light to a respective one of the light sensing elements or from a respective one of the light emitting elements. Thus, the optical elements of the housing and the light sensing and/or emitting elements need to be arranged side by side, and conventional rain-light sensors are therefore large, typically about 3 centimetres in diameter. Also, the printed circuit board and the housing need to be optically aligned to each other during assembly of the rain-light sensor, which is a time-consuming and costly procedure.

It is one object of the present invention to provide an optical vehicle environmental sensor that is easy to assemble and has a small footprint. According a first aspect, there is provided an optical vehicle environmental sensor comprising a housing and a multi-layered circuit board accommodated in the housing. The multi-layered circuit board comprises: a microoptics layer comprising a number of microoptical elements and an electronic layer having a number of light sensing elements. Herein, each of the light sensing elements is arranged in a light path of incident light that has passed through an associated one of the number of microoptical elements.

The proposed optical vehicle environmental sensor provides the following advantages: The use of microoptics allows to substantially downsize the optical vehicle environmental sensor by at least one order of magnitude. Due to the fact that both the microoptical elements and the light sensing elements are packaged in the multi-layered circuit board, a step of performing optical alignment of the housing and a circuit board during assembly may become unnecessary. The housing does not need to be made of optical-grade plastics, but can be made of less expensive lower grade plastics. Nonetheless, due to a simpler configuration of the housing a more compact design of the multi-layer circuit board that packages both the microoptics and the electronics, the proposed optical vehicle environmental sensor may be much sturdier than a conventional vehicle rain sensor. Furthermore, the multi-layered circuit board can be manufactured at scale in batches using semiconductor manufacturing techniques. That is, the size, the bill of material and the cost of the optical vehicle environmental sensor may be drastically reduced.

In particular, the optical vehicle environmental sensor performs sensing using visible or invisible light. In particular, the optical vehicle environmental sensor is suitable for being installed as an on-board part in a vehicle. In particular, the optical vehicle environmental sensor is configured to provide a signal from which one or more environmental conditions in the environment of the vehicle can be deduced.

Herein, the environmental conditions may comprise examples such as sunshine, ambient lighting, headlights of oncoming traffic, road illumination, fog, rain and the like. The optical vehicle environmental sensor may be adapted to be installed at an inner side of a window of the vehicle and to operate through the window of the vehicle. The window may be, in particular, a windscreen of the vehicle.

The optical vehicle environmental sensor may comprise circuitry configured to communicate a signal indicative of the incident light detected by the respective light sensing element to a control unit of the vehicle. Said circuitry may be comprised by the electronic layer of the multi-layered circuit board and/or may be comprised by another circuit board accommodated in the housing.

The term "a number of" may refer to a number of one and more, i.e., to either or a singularity or to a plurality, unless context dictates that a number of two or more, i.e., a plurality, is necessary.

The number of microoptical elements and the number of light sensing elements need not be the same. It is possible that two or more of the microoptical elements share the same associated light sensing element. In this case, different light arriving from different ones of the microoptical elements at the same light sensing element may cause the light sensing element to generate a composite sensing signal that may later be divided up into the individual contributions from each of the microoptical elements by software.

The housing may be made of plastics or of any other suitable material. The housing may comprise holes or transparent portions. The holes or transparent portions may allow light to enter the housing and be incident on the number of microoptical elements, and may allow light to be emitted from the number of microoptical elements to pass to an outside of the housing. The housing may comprise a connector accommodated in or provided integrally with the housing and adapted for connecting the optical vehicle environmental sensor to a wiring harness of the vehicle.

The respective microoptical element may be, for example, a microlense or a micrograting. The respecdtive microoptical element may be a diffractive microoptical element or a refractive microoptical element. The respective microoptical element may be an optical element that is between a micrometre and a millimetre in size. The respective microoptical element may be a microlense or micrograting that is integrated into the microoptics layer of the multi-layer circuit board. The respective microoptical element may manufactured by one of micromachining, photopolymerization, printing of diffractive patterns or the like. A plurality of microoptical elements may be manufactured simultaneously on a wafer and may be bonded at the wafer level.

In particular, the respective light sensing element is an element that is configured to output an electric signal indicative of light incident on the light sensing element. The respective light sensing element may be a charged coupled device, a complementary metal-oxide semiconductor, a phototransistor, a photodiode, or the like.

Each respective light sensing element may be a separate light sensor chip, and the number of light sensor chips may be distributed about an area of the electronic layer. For example, each light sensor chip may be arranged at a position substantially beneath an associated one of the microoptical elements. Alternatively, two or more of the sensing elements may be different sensing areas of a single integrated multi-sensor chip.

The light path may be a direct light path or an indirect light path. In other words, the light may pass directly from the microoptical element to the associated light sensing element, or the light may be guided, reflected, refracted or the like on its path from the microoptical element to the associated light sensing element. The microoptical layer and the electronic layer, as well as any optional further layers to be described below, may be stacked on top of each other. The respective layers may be glued together by an adhesive such as epoxy.

According to an embodiment, the multi-layered circuit board further comprises a spacer layer stacked between the microoptics layer and the electronic layer.

The spacer layer advantageously allows to increase a distance between the light sensing elements of the electronic layer and the microoptical elements of the microoptics layer. Thus, may be possible to arrange the light sensing elements in a focal point of the microoptical elements.

Accordingly, advantageously, no manual work of optically aligning the microoptical elements with the light sensing elements may be necessary.

The spacer layer may comprise solid portions that provide structural integrity and allow the microoptics layer to rest on the spacer layer and to allow the spacer layer to rest on the electronic layer. The space layer may further comprise void or transparent portions that allow light to pass from the microoptical elements to the light sensing element.

According to a further embodiment, each of the microoptical elements is adapted to bundle incident light onto the respective associated one of the number of light sensing elements.

That is, the light path of incident light from each microoptical element to the respective associated light sensing light element may be a direct light path. Herein, a "direct light path" describes a light path that is deflected or refracted only by one or more microoptical elements, but otherwise travels along a straight line between the microoptical elements and the light emitting elements. According to a further embodiment, the multi-layered circuit board further comprises a waveguiding layer stacked between the microoptics layer and the electronic layer. The waveguiding layer comprises a number of waveguides formed in the waveguiding layer. Each of the microoptical elements Is adapted to bundle incident light onto an associated one of the number of waveguides. Each of the waveguides is adapted to guide the bundled incident light to an associated one of the light sensing elements.

The waveguiding layer advantageously allows to guide light from that is incident from each of the microoptical elements to the respective associated one of the sensing elements along a nonlinear path. Therefore, the waveguiding layer advantageously allows for flexibility in design of the multi-layered circuit board. That is, thanks to the waveguiding layer, a position of a respective light sensing element in the electronic layer may not need to correspond to a position of the associated one of the microoptical elements in the microoptics layer.

For example, the waveguiding layer may be manufactured by photopolymerization of polymers such as polydimethylsiloxane.

According to a further embodiment, a plurality of the light sensing elements are respective sensing areas of a single integrated multi-component sensor chip.

A single integrated multi-component sensor chip may be a single chip that tightly integrates the plurality of sensing areas on a small space. Thanks to the waveguiding layer, which lifts the requirement of the light sensing elements having to be arranged at positions corresponding to the microoptical elements, it is possible to guide the light from the number of microoptical elements to the tightly integrated sensing areas of the single integrated sensor chip on the electronic layer that serve as the number of light sensing elements. Thereby, the level of integration may be improved and the bill of materials of the proposed optical vehicle environmental sensor may be advantageously reduced even further. According to a further embodiment, the multi-layered circuit board comprises a number of additional microoptics layers stacked between the microoptics layer and the electronic layer. Each additional microoptics layer comprises a number of microoptical elements. Each of the light sensing elements is arranged in a light path of incident light that has passed through a respective associated one of the number of microoptical elements of at least one of the microoptics layer and the number of additional microoptics layers.

In this way, by using a plurality of microoptics layers through which the incident light passes, wherein each microoptical element contributes to converging (or diverging, diffracting or refracting) of the incident light beam, it may be possible to more fully focus the incident light on the associated light sensing element even when an overall thickness of the multi-layered circuit board is comparatively small.

It is noted that a respective spacer layer may be arranged between any two of the microoptics layers and/or between the downmost microoptics layer and the electronic layer.

According to a further embodiment, all the microoptical elements of a same one of the microoptics layers are either diffractive microoptical elements or refractive microoptical elements.

By replacing the conventional lenses that are moulded together with the housing with the microoptics layer, greater flexibility in the optical design is enabled. In particular, in addition to diffractive lenses, also refractive microoptical elements, such as graded-index lenses, gratings, and the like may be used. However, preferably, a single microoptics layer comprises either only diffractive or only refractive optics, as the limitation to one of the two types of optics in each layer may be technologically beneficial.

According to a further embodiment, different respective sensing units comprising, respectively, at least one of the microoptical elements and an associated one of the light sensing elements are adapted to detect light in a different wavelength range and/or light in a different intensity range and/or light having a different angle of incidence.

Herein, the term "sensing unit" may refer to a combination of any one light sensing element with one or more of the microoptical elements and, potentially, additional circuitry used for operating the light sensing element and/or for shaping and/or processing a signal that is generated by the light sensing element in response to light incident on the light sensing element.

By packaging both the microoptics layer and the electronic layer into a single multi-layered circuit board, semiconductor wafer production methods can be used that advantageously allow to place differently configured sensing units adjacent to each other in the respective layers with an extremely small footprint.

Therefore, it may advantageously be possible to include a large variety of different functionalities in a single optical vehicle environmental sensor having a small footprint.

According to a further embodiment, different respective sensing units comprising, respectively, at least one of the microoptical elements and an associated one of the light sensing elements are adapted to provide at least part of a different functionality of the optical vehicle environmental sensor.

That is, the optical vehicle environmental sensor may advantageously be a multifunctional sensor device that can measure a large number of different environmental parameters.

Two or more sensing units and, optionally and additionally one or more emitting units to be described below, can cooperate to embody a single functionality. For example, a fog sensing functionality may be embodied by an emitting unit that emits light and a sensing unit that senses light reflected in response to the light being emitted by the emitting unit. Hence, each sensing unit embodies "at least part of" the respective functionality. According to a further embodiment, the respective functionality of the optical vehicle environmental sensor is selected from an ambient light sensing functionality, a forward light sensing functionality, a road brightness sensing functionality, a sun position sensing functionality, a solar light sensing functionality, and a fog detection functionality of the optical vehicle environmental sensor.

The forward light sensing functionality may be functionality for detecting headlights of oncoming traffic. The ambient light sensing functionality may be functionality for detecting ambient lighting conditions. The forward and the ambient light sensor elements may be used to control switching on and off of upper and/or lower beam headlights of the vehicle. The sun position sensing functionality may be functionality for detecting a position of the sun on the sky. The solar light sensing functionality may be functionality for detecting an amount of incident direct sunlight. The sun position sensing functionality and the solar light sensing functionality may be used for supporting an air conditioning system of the vehicle. The road brightness sensing functionality may be a functionality for measuring a road surface illumination and may be used to decide on an optimum and safe brightness level of a head- up display projected onto a windscreen of the vehicle by a head-up display unit. The fog detection functionality may be functionality for detecting a grade of fogging outside the vehicle that can be used to control a fog tail lamp, to issue a warning to slow down to the driver, to control slowing down of the vehicle, and the like.

According to a further embodiment, the electronic layer further comprises a number of light emitting elements. For each of the number of light emitting elements, an associated one or more of the microoptical elements are arranged in a light path of light that is emitted by the respective light emitting element.

Certain sensor functionalities, such as the fog sensing functionality, that require light to be emitted in order to be able to sense reflections of the specific light that was emitted, may thus be enabled. The respective light emitting element may be a light emitting diode or the like.

According to a further embodiment, different respective emitting units comprising, respectively, at least one of the microoptical elements and an associated one of the number of light emitting elements are adapted to emit light in a different wavelength range and/or light having a different angle of emission and/or is adapted to provide at least part of a different functionally of the optical vehicle environmental sensor.

According to a further embodiment, the electronic layer further comprises either an infrared light emitting element or an infrared light sensing element, and a sensing unit comprising one of the number of microoptical elements and further comprising either the infrared light emitting element or the infrared light sensing element is adapted to provide part of a rain sensing functionality of the optical vehicle environmental sensor.

The rain sensing functionality may detect a grade of wetting of the windshield by transmitting infrared light and detecting reflected infrared light. The rain sensing functionality may be used to set a wiping speed of a wiper and/or to turn the wiper on or off. The rain sensing functionality may require a certain distance between the infrared light emitting element and the infrared light sensing element due to being based on a necessity of total internal reflections of the emitted infrared light on the windshield. A partial miniaturization of the rain sensing functionality is advantageously possible by including one of the infrared light emitting element and the infrared light sensing element in the proposed multi-layer circuit board.

According to a second aspect, there is provided a vehicle comprising the optical vehicle environmental sensor of the first aspect or any of its embodiments. The optical vehicle environmental sensor is installed at an inner side of a window of the vehicle and is communicatively connected with a control device of the vehicle. The vehicle may be any vehicle having at least one window or other type of glass pane, such as a car, a light vehicle, a lorry, a motorcycle, an electric bike, a hovercraft, a boat, a sea vessel, an airplane, and the like.

The control device of the vehicle may be an electronic control unit (ECU) that implements higher-level functionality based on the output of the various sensing functionalities of the vehicle environmental sensor, such as climate control, headlight or taillight control, wiper control, parking assistance, driving assistance, fully or partly autonomous driving control and the like.

The optical vehicle environmental sensor may be communicatively connected with the control device by wire, such as via a vehicle wiring harness, or wirelessly, such was via WLAN, Bluetooth, Zigbee and the like.

The window of the vehicle may be a windscreen.

According to a third aspect, there is proposed a method of manufacturing a plurality of the optical vehicle environmental sensors of the first aspect or any of its embodiments. The method comprises the steps of: producing a microoptics wafer comprising a plurality of the microoptics layers arranged horizontally adjacent to each other; producing an electronic wafer comprising a plurality of the electronic layers arranged horizontally adjacent to each other; packaging a stack comprising the microoptics wafer and the electronic wafer; vertically cutting the stack of wafers into a plurality of dice, each die comprising one of the microoptics layers and one of the electronic layers; and accommodating each of the dice in a respective housing.

In this way, advantageously, a plurality of solid integrated multi-layer circuit boards are formed in a single manufacturing process. In particular, the step of packaging is performed at wafer-level before the dicing step. Thus, no alignment of optics may be necessary in the later manufacturing stages of the optical vehicle environmental sensor. Efficient mass production of the optical vehicle environmental sensors is advantageously enabled.

Further possible implementations or alternative solutions of the invention also encompass combinations - that are not explicitly mentioned herein - of features described above or below with regard to the embodiments. The person skilled in the art may also add individual or isolated aspects and features to the most basic form of the invention.

Further embodiments, features and advantages of the present invention will become apparent from the subsequent description and dependent claims, taken in conjunction with the accompanying drawings, in which:

Fig. 1 shows a vehicle according to exemplary embodiments of the invention.

Fig. 2 shows a multi-layered circuit board of an optical vehicle environmental sensor according to a first exemplary embodiment;

Fig. 3 shows a multi-layered circuit board of an optical vehicle environmental sensor according to a second exemplary embodiment;

Fig. 4 illustrates steps of an exemplary manufacturing method;

Fig. 5 shows wafers according to the exemplary manufacturing method;

Fig. 6 shows a stack of wafers according to the exemplary manufacturing method; and

Fig. 7 shows a plurality of dice cut from the stack of wafers.

In the Figures, like reference numerals designate like or functionally equivalent elements, unless otherwise indicated. Fig. 1 shows a vehicle 1 according to exemplary embodiments of the invention. The vehicle 1 has a windscreen 2, and an optical vehicle environmental sensor 4 is mounted at an inner side 3 of the windscreen 2. The optical vehicle environmental sensor 4 comprises a housing 5 and a multi-layered circuit board 6. None-shown circuitry on one of the layers of the multilayered circuit board 6 of the optical vehicle environmental sensor 4 is connected, via a wiring harness 7, with an electronic control unit 8. It is noted that the optical vehicle environmental sensor 4 in Fig. 1 is not drawn to scale, but is enlarged relative to the vehicle 1 to facilitate illustration.

The electronic control unit 8 performs processing for assisting a driver of the vehicle 1 and/or for autonomous driving of the vehicle 1 . Some of said processing requires environmental information about the environment of the vehicle 1 . Said environmental information may constitute information about headlights of oncoming traffic, information about ambient lighting conditions, information about a position of the sun on the sky or about an amount of incident direct sunlight, information about a level of road surface illumination, information about a grade of fogging outside the vehicle, and/or information about a degree of wetting of the windscreen 2 of the vehicle 1 , for example.

The electronic control unit 8 uses the optical vehicle environmental sensor 4 to acquire each of the above-mentioned kinds of environmental information. The optical vehicle environmental sensor 4 unit provides optical sensing functionalities for each of the aboveidentified kinds of environmental information. That is, the respective optical sensing functionality of the optical vehicle environmental sensor 4 detects the corresponding light, such as oncoming headlight, ambient light, solar light, or emits test light for testing outside fogging or windscreen wetting and detects a reflection of the test light, for example.

Each of the optical sensing functionalities may operate at a different wavelength range or different intensity. Merely as an example, ambient light sensing is performed with visible light in an intensity range of 0 to 25400 lux, for example, whereas test light for detecting windscreen wetting typically is infrared light in a wavelength range from 750 to 950 nm and with an intensity of 0 to 1020 W/m ² , for example. Furthermore, it is desirable to acquire distinct sensing signals for each of the kinds of light, i.e. for each kind of environmental information to be sensed. Therefore, as discussed hereinbelow in more detail, the optical vehicle environmental sensor 4 is provided with multiple distinct sensing units, wherein each sensing unit may be adapted to detect different kinds of light.

Fig. 2 shows the multi-layered circuit board 6 of an optical vehicle environmental sensor 4 according to a first exemplary embodiment in more detail.

The multi-layered circuit board 6 comprises an electronic layer 9 and a microoptics layer 10 that are stacked on top of each other.

The electronic layer 9 comprises three light sensing elements 12, 13 and 14 that may be mounted onto the electronic layer 9 or may be formed integrally with the electronic layer 9. The light sensing elements 12-14 detect incident light 15-17. Each of the light sensing elements 12-14 generates an electrical signal that is indicative of the respective incident light 15-17. The electrical signal is processed by non-shown circuitry that may also be mounted on or integrated into the electric layer 9 and/or may be arranged on a different non-shown circuit board inside the housing (5 in Fig 1), and is transmitted over the wiring harness (7 in Fig. 1 ) to the electronic control unit (8 in Fig. 1 ) of the vehicle (1 in Fig. 1 ).

It is noted that in the first exemplary embodiment, the light sensing elements 12-14 constitute three separate light sensing devices 12, 13 and 14, such as photodiodes, CMOS devices, CCD devices or the like.

The microoptics layer 10 comprises three microoptical lenses (microlenses) 18, 19, 20 that are integrated into the microoptics layer 10. Positions of the microlenses 18, 19, 20 in the microoptics layer 10 correspond to positions of the light sensing elements 12-14 in the electronics layer 9. Each of the microlenses 18-20 bundles the respective incident light 16-17 to an associated one of the light sensing elements 12-14. That is, each light sensing element 12-14 is arranged in a light path of the respective incident light 15-17 that has passed through the associated one of the microlenses 18-20.

Thus, the first light sensing element 12 and the first microlense 18 form a first sensing unit for sensing the incident light 15. The second light sensing element 13 and the second microlense 19 form a second sensing unit for sensing the incident light 16. The third light sensing element 14 and the third microlense 20 form a third sensing unit for sensing the incident light 17.

By appropriately selecting and adapting the microlenses 18-20 and the light sensing elements 12-14, each of the different sensing units may be adapted to detect light in a different wavelength range and/or light in a different intensity range and/or light having a different angle of incidence. Thus, each of the different sensing units may provide a different one of the functionalities of the optical vehicle environmental sensor (4 in Fig. 1) discussed above.

The multi-layered circuit board 6 shown in Fig. 2 may be manufactured at scale in batches using a semiconductor manufacturing technique. A single manufacturing process may be used to produce the multi-layered circuit board 6, which may constitute a single package. In other words, the positional relationships between the microoptics layer 10 and the electronic layer 9 are predetermined by the manufacturing process. No optical alignment between the microoptics layer 10 and the electronic layer 9 may need to be performed during assembly of the optical vehicle environmental sensor (4 in Fig. 1). Furthermore, through use of microoptics, the microlenses 18-20 may be lenses having a size in the sub-millimetre range. Therefore, the multi-layered circuit board 6 may have a small footprint (size).

Fig. 2 shows that a spacer layer 11 is stacked between the electronic layer 9 and the microoptics layer 10. The spacer layer 11 creates and defines a predetermined distance between the microoptics layer 10 and the electronic layer 9. In this way, the light sensing elements 12-14 may be located in a focal point of the microlenses 18-20, thus maximising the light yield and thus the efficiency of the optical vehicle environmental sensor (4 in Fig. 1). However, the spacer layer 11 is not a necessary feature. The optical vehicle environmental sensor (4 in Fig. 1) may also operate with sufficient efficacy if the light sensing elements 12- 14 are not exactly located in the focal points of the microlenses 18-20, and/or arranging the light sensing elements 12-14 in the focal points of the microlenses 18-20 may be achieved even without the spacer layer 11 .

It is noted that the microoptics layer 10, the spacer layer 11 and the electronic layer 9 may be glued to each other. In other words, the concept of "stacking" layers may comprise arranging the respective layers on top of each other in a sandwiching manner and gluing the layers to each other.

Fig. 3 shows a multi-layered circuit board 6 of an optical vehicle environmental sensor (4 in Fig. 1) according to a second exemplary embodiment.

In addition to the electronic layer 9, the microoptics layer 10 and the spacer layer 11 , the multi-layered circuit board 6 of the second exemplary embodiment comprises three additional microoptics layers 21 , 22, 23 two additional spacer layers 24, 25, and a waveguiding layer 26.

A first distinguishing difference over the first exemplary embodiment is that the multi-layered circuit board 6 of the second exemplary embodiment comprises the additional microoptics layers 21-23. Herein, the microoptics layer 10 comprises the converging microlens 18 and a void portion (opening) 27. The first additional microoptics layer 21 comprises further converging microlenses 28 and 29. The second additional microoptics layer 22 comprises a transparent portion 30 and a diverging microlens 31 . Whereas the microlenses 18, 28, 29, 31 constitute examples of diffractive optics, the third additional microoptics layer 23 comprises two refractive optical microelements 32, 33. It is noted that each of the microoptics layers comprises, aside from any void or transparent portion 27, 30, only one type of microoptics. The microoptics layer 10 and additional the microoptics layer 21 comprise only converging the diffractive microoptical elements 18, 28, 29. The additional microoptics layer 22 comprises only the diverging diffractive microoptical element 31 . The additional microoptics layer 23 comprises only the refractive microoptical elements 32, 33.

By stacking a plurality of microoptics layers 10, 21 , 22, 23 on top of each other, it is possible to construct complex optical systems that are tailored to the requirements of sensing each type of incident light 15, 16. Also, in a case where different types of incident light 15, 16, require different types of microoptics, such as converging vs. diverging, or diffractive vs. refractive, there is no need to integrate different types of microoptical elements on a single microoptics layer 10, which may pose technological issues. Rather different microoptics layers 10, 21-23 can be used for different types of microoptical elements 18, 28, 29, 31 ,-33.

A further difference over the first exemplary embodiment is the presence of the waveguiding layer 26. The waveguiding layer 26 comprises the waveguides 34 and 35. The waveguides are formed by laser-treating the waveguiding layer 26 so as to modify its refractive index at the intended locations of the waveguides 34, 35. The difference in refractive index between the waveguides 34, 35 and the surrounding material of the waveguiding layer 26 allows to form a waveguide along which incident light can travel, similar to an optical fibre.

The waveguides 34, 35 guide incident light 15, 16, that is bundled onto the upper (in Fig. 3) ends of the waveguides 34, 35 by the refractive microelements 32, 33, to the light sensing elements 12, 13 of the electronics layer 9.

With reference to Fig. 2 and Fig. 3, the waveguiding layer 26 of the second exemplary embodiment advantageously lifts the requirement of the first exemplary embodiment, where the positions of the microelements 12-14 (Fig. 2) needed to correspond to the positions of the microlenses 18-20. In contrast, thanks to the waveguiding layer 26, the light sensing elements 12, 13 of the second exemplary embodiments have no restrictions with regards to their disposition in electronic layer 9.

Further with reference to Fig. 3, in the second exemplary embodiment, for example, thanks to the waveguiding layer 26, it is possible to use a single integrated multi-component light sensor chip 36 instead of the plurality of separate light sensing devices 12-14 (Fig. 2). The light sensing elements 12, 13 of the second exemplary embodiments are formed by separate light sensing areas of the single integrated multi-component light sensor chip 36. Therefore, the light sensing areas 12, 13 are arranged close to each other on the single chip 36.

However, the waveguides 34, 35 of the waveguiding layer 26 can guide light that is bundled onto the waveguiding layer 26 by the refractive microoptical elements 32, 33 of the third additional microoptical layer 23, which are separated by a comparatively large distance, to the respective light sensing areas 12, 13, which are arranged close to each other.

Thus, in the second exemplary embodiment, a first sensing unit is formed by the converging microlens 18 of the microoptics layer 10, the converging microlens 28 of the first additional microoptics layer 21 , the transparent portion 30 of the second additional microoptics layer 22, the refractive microoptical element 32 of the third additional microoptics layer 23, the waveguide 34 of the waveguiding layer 26 and the sensing area 12 of the single integrated multi-component light sensor chip 36. A second sensing unit is formed by the void portion 27 of the microoptics layer 10, the converging microlens 29 of the first additional microoptics layer 21 , the diverging microlens 31 of the second additional microoptics layer 22, the refractive microoptical element 33 of the third additional microoptics layer 23, the waveguide 35 of the waveguiding layer 26 and the sensing area 13 of the single integrated multicomponent light sensor chip 36.

Specifically, the microoptical elements 18, 28, 30, 32, 34; 27, 29, 31 , 33 of each of the sensing units are not located on a respective linear path. However, thanks to the waveguides 34 and 35, which guide the light path in a nonlinear fashion, in each of the sensing units, the respective light sensing element 12, 13 is still arranged in a light path of incident light 15, 16 that has passed through the associated microoptical elements 18, 28, 30, 32, 34 or 27, 29, 31 , 33, respectively.

An example of a method of manufacturing a plurality of the optical vehicle environmental sensors 4 of the first or exemplary embodiment will now be described with reference to Fig. 4-Fig. 7. Fig. 4 illustrates steps of the exemplary manufacturing method. Fig. 5 shows wafers 37, 39 according to the exemplary manufacturing method. Fig. 6 shows a stack 41 of wafers 37, 39 according to the exemplary manufacturing method; and Fig. 7 shows a plurality of dice 42 cut from the stack 41 of wafers 37, 39.

In step S1 , a microoptics wafer 37 is produced that comprises a plurality of areas 38. The waver 37 is called "microoptics wafer" because each area 38 of the microoptics wafer 37 constitutes a microoptics layer 10 (Fig. 2) that comprises a number of microlenses 18-20 (Fig- 2).

In step S2, an electronic wafer 39 is produced that comprises a plurality of areas 40. The wafer 39 is called "electronic wafer" because each area 40 of the electronic wafer 39 constitutes an electronic layer 9 (Fig. 2) that comprises a number of light sensing elements 12-14 (Fig. 2), and may comprise additional supporting circuitry.

In step S3, packaging is performed. Specifically, a stack 41 is formed that comprises at least the microoptics wafer 37 and the electronic wafer 39, and may optionally comprise further wafers (not shown), such as spacer wafers comprising a plurality of the spacer layers 11 (Fig. 2), additional microoptics wafers comprising a plurality of additional microoptics layers 21-23 (Fig. 3), a waveguiding wafer comprising a plurality of the waveguiding layer 26 (Fig.

3) and the like. In the stack 41 , the microoptics wafer 37 and the electronic wafer 39 are placed on top of each other such that the areas 38 of the microoptics wafer 37 are aligned with the areas 40 of the electronic wafer 39. In order to achieve said alignment, it is sufficient to align the wafers 37, 39 at each other, which may be a straightforward task. In step S4, dicing is performed. Specifically, the stack 41 is cut vertically, i.e. perpendicularly to a plane of the wafers 37, 39 forming the stack 41 , along the borders of the areas 38, 40, to achieve a plurality of dice 42. Each die 42 thus constitutes a multi-layered circuit board 6 as shown in Fig. 2.

In step S5. each of the dice 42 is accommodated in a respective housing (5 in Fig. 1). Advantageously, no optical alignment needs to be performed in step S5.

The exemplary manufacturing method allows the optical vehicle environmental sensors 6 to be produced at scale ion batches using a semiconductor manufacturing technique, with a reduced bill of materials, reduced cost and increased efficiency.

Although the present invention has been described in accordance with preferred exemplary embodiments, it is obvious for the person skilled in the art that modifications are possible in all embodiments.

Although the optical vehicle environmental sensor 4 shown in Fig. 1 is connected to the electronic control unit 8 by wire (wiring harness 7), it is also considered that the optical vehicle environmental sensor 4 could be connected to the electronic control 8 in a wireless manner.

The specific order and combinations of the microoptics layers 10, 21-23 shown in Fig. 2, the specific combinations of types of microoptical elements (diverging, converging, diffractive, refractive) 18-20, 28, 29, 31 -33 shown in Fig. 1 and Fig. 2 are mere examples. It will be appreciated that according to specific requirements of each sensing unit and emitting unit to be formed, arbitrary microoptical systems may be created by arranging any number of microoptics layers 10, 21-23 in any order and any types of microoptical elements 18-20, 28, 29, 31-33 in any order inside each of the microoptics layers 10, 21-23 in accordance with these requirements. Also in the first exemplary embodiment, a waveguiding layer 26 may be stacked between the microoptics layer 10 and the electronic layer 9 instead of or in addition to the spacer layer 1 1 . Also in the second exemplary embodiment, it is possible to omit the waveguiding layer 26 when using the electronics layer 9 comprising light sensing elements 12-14 that are formed as separate devices and arranged in positions corresponding to the positions of the microoptical elements 32, 33 of the downmost microoptical layer 23.

Although the first and second exemplary embodiments described sensing units each comprising at least one microoptical element 18-20, 27-33 and an associated light sensing element 12-14, the invention also pertains to arrangements in which at least one of the light sensing elements 12-14 is replaced with a light emitting element, such as a light emitting diode, and an emitting unit is formed that comprises at least one microoptical element 18-20, 27-33 and the associated light emitting unit. In this case, the light paths 15-17 are reversed and constitute light paths of emitted light. All other features and advantages described in the first and second exemplary embodiment are applicable to a case in which at least some of the sensing units are replaced by emitting units in this way.

Thus, it may be possible to form advantageous combinations of light emitting units and light sensing units, that can be used, for example, in a fog sensing functionality which emits test light and detects the reflected test light. Also, it is conceivable to integrate either one of an infrared emitting unit and an infrared sensing unit of a rain sensing functionality onto the multi-layered circuit board 6. The rain sensing functionality may comprise emitting infrared test light and sensing totally reflexions of the infrared light at the outer surface of the windscreen 2.

That is, according to exemplary embodiments, a plurality of various and diverse functionalities of an optical vehicle environmental sensor 4 may be advantageously integrated into a single multi-layered circuit board 6 that has a small footprint thank to the use of microoptics and that provides the further advantage that no optical alignment needs to be performed during further assembly of the optical vehicle environmental sensor 4.

REFERENCE NUMERALS

1 vehicle

2 windscreen

3 inner side of windscreen

4 optical vehicle environmental sensor

5 housing

6 multi-layered circuit board

7 wiring harness

8 electronic control unit

9 electronic layer

10 microoptics layer

11 spacer layer

12-14 light sensing elements

15-17 incident light

18-20 microlenses (microoptical elements)

21-23 additional microoptics layers

24-25 additional spacer layers

26 waveguiding layer

27 void portion

28, 29 converging microlenses (microoptical elements)

30 transparent portion

31 diverging microlens (microoptical element)

32, 33 refractive microoptical elements

34, 35 waveguides

36 integrated multi-component light sensor chip

37 microoptics wafer

38 area of microoptics layer

39 electronics wafer

40 area of electronics wafer 41 stack of wafers

42 dice