Optical CRA detector unit, multispectral sensor system and camera system

Abstract

An optical CRA detector unit (14) includes an optical CRA sensor (26) disposed on a substrate (22), where the optical CRA sensor (26) includes a plurality of CRA detector pixels (30) having the same spectral sensitivity, each CRA detector pixel generating an irradiance sensor signal, where the irradiance sensor signal is transmitted to the substrate (22). The irradiance sensor signals generated by the CRA detector pixels (30) are provided with parametric characteristics of the chief ray angle (CRA) for generating the irradiance of the CRA detector unit (14), should allow a specific compact and miniaturized package. According to the invention, this is achieved by providing an aperture element (32) disposed above the optical CRA sensor (26) with respect to the substrate (22), the aperture element (32) comprising a flat, laterally extending refractor element (34) defining a top surface (36) and a bottom surface (38) wherein the top and bottom surfaces (36, 38) are provided with a top aperture layer (40) and a bottom aperture layer (42), respectively, and wherein the top aperture layer (40) is provided with a top aperture (44) and the bottom aperture layer (46) is provided with a bottom aperture (46), the lateral dimension of which is at least the lateral dimension of the top aperture (44).

Description

TECHNICAL BACKGROUND

[0002] The present invention relates to an optical or multispectral CRA (Chief Ray Angle) detector unit. More specifically, the present invention relates to an optical CRA detector unit comprising an optical CRA sensor arranged on a substrate for detecting received photons, the optical sensor comprising a plurality of CRA sensor pixels, each CRA sensor pixel generating an irradiance signal, wherein the irradiance sensor signals generated by the CRA detector pixels are provided for generating a parametric characteristic of the angle of incidence of the irradiance of the CRA detector unit. Furthermore, the present invention relates to a multispectral sensor system comprising such an optical CRA detector unit and to a camera system comprising such an optical CRA sensor. BACKGROUND

[0003] Optical or multispectral sensors are increasingly used in a variety of technical fields such as smart phones and mobile devices, smart home and building, industrial automation, medical technology, interconnected vehicles. At the same time, sensor data becomes more complex and is expected to meet the requirements for high accuracy. Currently, color and spectral light sensing at chip scale has a variety of applications in color recognition, data authentication, spectral analysis, and other industrial and consumer level optical detection applications. In a number of important applications, particularly for camera applications, such sensors are used as ambient light sensors for so-called "auto white balance" functions in order to provide the necessary background information for appropriate correction functions and thereby to improve the imaging quality in general.

[0004] Common multispectral sensors are usually based on a pixel array and a pixel- on-filter for each pixel. For spectroscopy applications, the filters can be selected to have linearly independent filter characteristics. In order to achieve an accurate spectral measurement of a given source, the incident radiation should be known in order to compensate for the different responses of the individual pixels. In this way, the amplitude of the spectral signals of the pixels can be used to calculate a spectral reconstruction of the studied light source. Usually, multispectral sensors also comprise interference filters designed specifically for the use case.

[0005] However, a uniform distribution of the incident radiation over the pixel array is an ideal situation. In real systems, in contrast, the actual illumination detected at sensor level can vary for different channels due to geometric effects limiting the individual field of view (FOV), the dominant angle of incidence or "chief ray angle" (CRA) of the incident radiation, etc. In such systems, the geometric effects can be caused by misalignments of individual components due to manufacturing tolerances, etc. However, especially for use in ambient light sensor devices, the uniformity of the incident light distribution at detector level can be of particular importance. In order to provide a highly reliable uniform distribution, a diffuser can be used at a location before the incident radiation reaches the pixels in order to mix the incident light as good as possible and to deliver the light to the sensor array in a uniform (ideally Lambertian) way. Furthermore, the spectral sensitivity of an interference filter based multi-spectral sensor strongly depends on the angular distribution of the light illuminating the filter on the detector array. Especially for interference filters, the angular dependent transmission characteristics need to be considered for providing correct results. This is another important reason why a diffuser is usually used to generate an always similar angular distribution.

[0006] Generally, in ambient light sensor systems, such a setup and use of a (nearly) Lambertian diffuser is expected to provide reliable relative measurements between individual channels of the sensor, independent of the direction or angle of the incident light. Due to this reliable measurement of the respective spectral channel ratios, it will be possible to perform a correct spectral reconstruction to correctly characterize the incident radiation, independent of the angle of illumination. However, this will not be true for the measurement of the total amount of incident radiation or irradiance or illuminance, which can strongly depend on the tilt angle of the respective device with respect to the incident radiation, especially the so-called angle of incidence (AOI), also called "chief ray angle" (CRA) in the presence of a dominant light source. However, the global value characteristic of the incident light intensity can be relevant for other signal processing and the absolute value of the irradiance detection will decrease as a cosine function for typical designs and layouts of detector channels. Especially, a typical wearable or handheld device such as a smart watch or mobile phone will be tilted at any time and the accuracy of the illuminance measurement etc. will provide false output values for applications in such devices.

[0007] In some solutions, a compensation approach can be used by providing additional compensation pixel structures which are arranged to collect geometric information about the incident illumination and other potential sources of detection errors and to provide them to the sensor control logic in order to modify the spectral compensation matrix for the actual sensor pixels. For such a correction setup, a cost-efficient and reliable structure is desired, especially in a very compact design which can be used for miniaturization concepts. SUMMARY

[0008] It is therefore the object of the present application to provide an improved CRA detector unit of the above-identified type, which detector unit comprises an optical sensor with an array of detector elements or pixels, which helps to overcome the above-identified drawbacks (in particular in a certain reduced and simple setup) in order to reduce the manufacturing costs. Moreover, an improved multispectral sensor shall be provided.

[0009] With respect to an optical CRA detector unit, the object is achieved in that an aperture element is arranged above the optical CRA sensor unit with respect to a substrate, the aperture element comprising a planar, laterally extending refractor element, the refractor element defining a top surface and a bottom surface, wherein the top surface and the bottom surface are provided with a top aperture layer and a bottom aperture layer, respectively, and wherein the top aperture layer is provided with a top aperture and the bottom aperture layer is provided with a bottom aperture, the lateral dimension of the bottom aperture being at least the lateral dimension of the top aperture.

[0010] The preferred embodiments are subject matter of dependent claims.

[0011] The present application is based on the consideration that in order to overcome the above-identified potential drawbacks and to provide a performance-improved ambient light sensor, a dedicated CRA detector unit shall be provided, preferably in addition to and in combination with a spectral detector unit. In order to correctly and comparably refer to light intensity values, the CRA detector pixels preferably all shall have the same spectral sensitivity. In order to be able to provide angular information with respect to the incident radiation, the CRA detector pixels shall be provided with a common or joint aperture in order to provide a certain spatial resolution and angular information. In order to make the design concept compact and multifunctional, according to one aspect of the present application, the common or joint aperture is provided by a dedicated aperture component, which dedicated aperture component due to its physical structure can also perform a cover or housing function of the sensor array.

[0012] In a preferred embodiment, the CRA detector pixels are arranged in a sensor array within a base plane defined by at least three of the CRA detector pixels. In a further preferred embodiment, a plurality of the CRA detector pixels are located within a peripheral range of the sensor array and at least one of the CRA detector pixels is located within a central region of the sensor array within the base plane. In this setup, the central pixel can be used for reference in order to correctly and comparably identify changes in the detected irradiance in the other pixels by comparison. Moreover, such a central pixel will also facilitate the identification of point-type radiation sources and thus significantly improve the evaluation capabilities of the system.

[0013] In yet another preferred embodiment, each of the CRA detector pixels located in the peripheral range of the sensor array is associated with at least one other pixel in the peripheral range in a relative position with respect to the center of the sensor array among the CRA detector pixels or "partner pixels". In such an arrangement, for any direction defined by such a pair of pixels, a direct value of the angle of illumination can be determined by comparison or by a ratio of the respective sensor values.

[0014] To facilitate the effect of measuring the tilt angle or the angle of illumination, in an important aspect of the present invention considered as an independent invention, the effective aperture of the CRA detector is designed to be smaller or narrower compared to the lateral extension or size of the underlying CRA sensor arrangement. In the design provided by the present invention, it is realized that the aperture width of the bottom aperture of the aperture element is smaller than the lateral dimension of the sensor array in the base plane. In said context, the aperture or aperture width is thus understood to refer to the free aperture or its diameter through which the light rays are received by the underlying sensor system. This design principle will ensure that the respective CRA detector pixel is enabled to detect the incident radiation, especially in case the direction of the light is tilted with respect to the system and the portion below the aperture edge is illuminated. Preferably, the width of the aperture is smaller than the lateral dimension of the sensor arrangement. In a preferred embodiment, and according to an aspect of the present invention, the width of the aperture is selected to be about 50% of the lateral dimension of the sensor arrangement. In a preferred embodiment, the width of the aperture can be about 200 pm, while the lateral dimension of the sensor arrangement can be about 400 pm.

[0015] In a preferred embodiment, each of the CRA detector pixels consists only of a photonic measurement unit, preferably a photodiode.

[0016] In another preferred embodiment, the CRA detector unit further comprises a measurement unit configured to provide a sensor signal generated by the optical sensor, wherein the measurement unit is arranged to calculate the parametric characteristic of the chief ray angle (CRA) based on a calculation of a ratio of the irradiance sensor signals generated by any two of the CRA detector pixels.

[0017] In a preferred embodiment, the refractor unit is a glass element, in particular a glass wafer or glass substrate or spacer. In this aspect of the present invention, a glass-based aperture element is provided. The aperture unit of this aspect of the present invention comprises a glass element having a first or top aperture layer and a second or bottom aperture layer. For these layers, in an aspect of the present invention, a material with high absorption and minimal transmission is selected, such as "black chrome". Alternatively, a suitably designed stack of an interference filter comprising further metal layers can also be provided.

[0018] The aperture unit can be provided on a through-silicon via (TSV) chip with diodes. In this setup, the FOV is defined by the diameter of the apertures on the first and second aperture layers on and below the glass element, the distance of the glass element to the substrate, the thickness of the glass and the refractive index of the glass. In this preferred embodiment, the accurate process of the aperture mask and the wafer scale mounting guarantees the same angular power distribution for all spectral channels, since these parameters can be provided identically for all channels due to the high production and manufacturing standards.

[0019] Depending on the individual use case and potentially other parameters or requirements, the aperture element can be positioned away from the substrate carrying the sensor unit, whereby a certain type of gap is left between the substrate surface and the bottom aperture layer. However, in the preferred embodiment, the aperture element and its bottom aperture layer are mounted directly on top of the substrate and the optical sensor, preferably even in contact with the substrate and the optical sensor. In this preferred embodiment, due to the direct contact between these components, a very compact design with high mechanical strength can be achieved.

[0020] With respect to the multispectral sensor system, the above-mentioned object of the present application is achieved in that, in addition to the optical CRA detector unit described above, a spectral detector unit is provided, which comprises an optical spectral sensor arranged on the substrate for detecting received photons, which optical spectral sensor comprises a plurality of sensor pixels, each sensor pixel generating a multispectral sensor signal as part of one of a plurality of detector channels.

[0021] In a preferred embodiment, which is considered to be a separate aspect of the present application, the spectral detector unit in the multispectral sensor system comprises an aperture element arranged above the spectral detector unit with respect to the substrate, which aperture element comprises a flat, laterally extending refractor element, which refractor element defines a top surface and a bottom surface, wherein: - the top surface and the bottom surface are provided with a top aperture layer and a bottom aperture layer, respectively, - the top aperture layer and the bottom aperture layer are provided with a plurality of top apertures and bottom apertures, respectively, the top apertures and the bottom apertures being arranged in pairs, thereby forming a plurality of dual apertures, such that in each dual aperture the top aperture is arranged on top of its corresponding bottom aperture, and - for each of the detector channels, a single one of the dual apertures is provided which is associated with each channel.

[0022] This aspect of the present invention is based on the consideration that in addition to the effect of the respective device being tilted with respect to the incoming radiation, also the geometrical effects introduced by the various components can be a source of potential poor performance of the sensor system. In particular, in the present consideration the main source of error and inaccuracy is associated with the provision of one single common aperture and diffuser system to the various or all sensor channels. Thus, in such conventional systems the differences and variations between the individual pixels or channels with respect to the detection of the incoming radiation will be caused by the individual positioning differences of them with respect to the single joint aperture / diffuser system. In order to overcome this potential source of inhomogeneity between the individual channels, this aspect of the present invention suggests to provide a separate individual aperture for each channel. Thereby, the necessary design and positioning accuracy of each individual aperture can be provided for the optical and transmission properties of each channel, and by a proper, highly correct manufacturing of the aperture system, the homogeneity and comparability between the different channels can be ensured.

[0023] In one aspect of the present invention, this "one aperture per channel" approach can be implemented by providing a common joint aperture element for the set of channels, wherein a planar shaped central refractor element is provided with aperture layers on both of its planar sides, each aperture layer providing a plurality of openings or apertures. These layers and their openings or apertures can then be arranged at both planar sides of the refractor element such that in a pair-wise structure each aperture in the first layer has a corresponding aperture in the second layer positioned on top of its counterpart or in the same lateral space as its counterpart, thereby forming a double aperture structure which can be individually associated with an individual sensor channel. In principle, this "one aperture per channel" concept can be implemented by only one aperture layer, which is necessary for the correct definition of the FOV of the underlying sensor. Preferably, the upper or top aperture layer is arranged in this way. Preferably, also an additional lower aperture layer is arranged in order to correctly define the optical geometry.

[0024] In this aspect of the present invention providing a combined solution of the optical CRA detector unit with this version of the spectral detector unit, the optical spectral detector unit can be arranged in a non-diffuser bearing arrangement in front of the sensor, which is considered highly beneficial with respect to cost and efficiency aspects. Thereby, this combined arrangement allows for use cases with different AOI conditions, wherein the spectral sensitivity itself can be different in any condition. Since the angular distribution of the radiation is known due to the combination with the CRA detector unit, the effective filter transmittance can be calculated (e.g. by the transfer matrix method), and based thereon, the matrix for the spectral reconstruction can be calculated.

[0025] Each pixel of the spectral detector unit can comprise a photodiode as signal generating unit. According to a preferred aspect of the present invention, the detector channels each comprise at least one of these pixels and an optical filter associated with the at least one pixel. As with comparable sensor designs, in such a design the filter determines the transmission characteristics of the respective sensor pixel. In embodiments of the present invention, such a collection of pixels or photodiodes with associated optical filters can be arranged next to each other in a stacked or packaged type of design. However, in a further aspect of the present invention, considered as an independent invention, for at least one of the detector channels, the optical filter is arranged on top of the top aperture of the dual aperture associated with the at least one channel. In other words, in this preferred arrangement, the photodiode or pixel of the channel is positioned directly on the substrate, i.e. "underneath" the aperture element covering the substrate, while the optical filter associated therewith is positioned on top of the aperture element and thus spaced apart from the pixel or photodiode associated therewith by the thickness of the aperture element. In this design, the optical filter, typically and preferably an interference filter, can be machined and structured on top of the aperture element and thus as a last process step before dicing after mounting of the aperture element.

[0026] In a further preferred embodiment, an additional direct current blocking filter can be arranged on top of the top aperture of the dual aperture of one or more of these detector channels or on top of the optical filter associated therewith. In particular, the direct current blocking filter can be a VIS bandpass filter arranged to suppress the additional UV and / or NIR range of all spectral channels.

[0027] Due to the main design of the detector unit, a uniform illumination of the individual channels and their actual sensors is achieved, as these channels are provided with individual associated apertures and by manufacturing the aperture elements with appropriate accuracy the same conditions can be provided for all channels. Even if misalignments etc. occur, the effect will be the same for all channels and no differences between the channels will occur. Thus, as one of the advantages of the present invention, the detector unit can be designed without a diffuser element as in conventional designs, even under high quality and accuracy standards. In principle, such a diffuser element can be considered obsolete in the concept of the present invention, as the uniformity between the channels is achieved by other means, in particular by the "individual aperture per channel" concept. This allows for a very compact design of the detector unit in a miniaturized sensor configuration. In an aspect of the present invention, this advantage is further extended by combining this concept with modern wafer level chip scale packaging ("WLCSP") technology in order to obtain a reliable and cost-effective compact and miniaturized sensor design using only a few components. In an aspect of the present invention, the detector unit is designed in WLCP technology.

[0028] In a preferred embodiment, the spectral sensor pixels each have different transmission characteristics, and preferably are linearly independent. The pixels can be regarded as channels of a multi-spectral sensor. Further, in a yet further aspect of the present application and in view of the intended application or use of the detector unit in an ambient light sensor (ALS), preferably about 5 to 12 channels with different transmission characteristics, in particular peak spectral sensitivity, are provided. Based on the preferred number range of channels, and taking into account that an at least approximately reconstructed detected spectrum in the visible range is desired, in a preferred embodiment, the spectral sensitivity of some or each of the channels is of a cosine shape, wherein the width of the full width at half maximum (FWHM) approximately equals the spacing between adjacent peaks. In a yet further embodiment, the spectral sensitivity of one or each channel can be of a Gaussian shape.

[0029] In a yet further aspect of the present application, which is considered to be an independent invention, the multi-spectral sensor system can be provided in a hybrid or integrated design, which means that both the optical CRA sensor and the optical spectral sensor are part of a joint or integrated chip structure, in particular by being provided with both a common or joint substrate and a common or joint aperture element. In this preferred provision, the optical CRA sensor of the optical CRA detector unit and the optical spectral sensor of the spectral detector unit are arranged on the same substrate, and the same aperture element is provided above both the optical CRA sensor of the optical CRA detector unit and the optical spectral sensor of the spectral detector unit. In this aspect of the present application, the optical CRA detector unit can be understood as providing an additional channel with an optical CRA sensor array structure behind a dual aperture dedicated to the optical CRA sensor, with respect to the design concept of the optical spectral sensor unit being the "one aperture per channel" approach.

[0030] In a preferred embodiment, the multi-spectral sensor system is designed as an ambient light sensor. In a yet further preferred embodiment, the multi-spectral sensor system is designed as a UV sensor, providing a measure of the current UV load by ambient light, for example for providing information on potential risks to exposed human skin due to UV load in an application. In such a UV sensor, typically the sun is considered as one dominant radiation source under consideration, and thus the compensation concept of the present application for such an application, including the determination of the CRA, can be particularly versatile.

[0031] In one aspect, the present application also proposes a camera system, preferably in a smartphone or a wearable device, comprising an ambient light sensor and / or a UV sensor with an optical detector unit of the type identified above.

[0032] It can be seen that the main advantage achieved by the present application lies in the fact that the basic idea of integrating the aperture of the CRA sensor system into a laterally extending aperture element based on a refractor element allows a very compact design which is particularly suitable for miniaturization concepts, wherein the aperture element can also be used as a cover element to protect the sensor positioned thereunder.

[0033] Furthermore, the idea of providing separate optical channels for the multispectral sensor component, wherein the respective pixels of each channel are associated with an individual aperture system, allows these channels to have identical optical and geometrical properties at low tolerances. Thus, the detector unit can be designed with high accuracy and reliability without the use of special diffuser elements and thus at reduced costs, particularly suitable for advanced production techniques and miniaturized designs. Thus, enhanced optical and spectral performance can be achieved at reduced costs and with a reduced number of components.

[0034] In other words, according to the idea of the present application, each channel is provided with its own, associated optical aperture. It is further geometrically separated from the adjacent channels, thereby preventing or at least minimizing cross-talk between the channels. The channel-wise optical separation defines similar and comparable optical properties (FOV, synchronous alignment, power distribution over the filter, etc.) for all color or spectral channels without the use of additional optical components such as diffusers.

[0035] In addition, due to the channel-wise optical configuration of the spectral channels in one aspect of the present application, preferably in combination with the high accuracy of available modern process techniques, low tolerances and enhanced optical and spectral performance are allowed. In a further result, the arrangement provides more degrees of freedom for the distribution of the optical channels within the chip area, since there is no need to provide common elements such as a joint diffuser for all channels. Thus, the individual channels can be spaced relatively wide from each other on the chip, thereby providing gaps between adjacent channels which can possibly be filled with circuitry parts or other electronic components on the chip in an intelligent arrangement.

[0036] In a further advantage, interference ripples in the IC passivation can be reduced due to the explicit and wide AOI (FOV). The filter design can be specified for this angular distribution.

[0037] In the combined system, a device is provided which can be used without the use of a diffuser, thus saving costs, while the angular condition can be correctly identified and on the basis of which an effective measurement result can be generated if the incidence angle is smaller than the maximum incidence angle given by the sun illumination. The spectral variation of the responsivity can be corrected on the basis of which, allowing excellent accuracy. The typical cosine error resulting from the diffuser arrangement as well as the angular-dependent filter transmission spectrum shift can be compensated.

[0038] In summary, the same angular power distribution (compared to the spectral variations caused by conventional geometric tolerances in conventional systems) can be achieved between channels to obtain similar spectral performance to interference filters. Optical channel separation can be provided by appropriate characteristics of the refractive index of the refractive elements. The limitations of conventional filter design rules and the necessary compact arrangement of channels can be overcome. Therefore, a single spectral channel is sufficient, whereas in previous systems, it might have been necessary to use opposing dual diodes to compensate for geometric, angular, and spectral effects. Attached Figure Description

[0039] Preferred embodiments and aspects of the present invention will be further described with reference to the accompanying drawings. In these drawings, Figure 1 A camera system is shown, specifically designed for use in smartphones. Figure 2 Shown in cross-section Figure 1 The multispectral sensor system of the camera system in the middle.

[0040] Figure 3 shows a top view of an embodiment of the sensor pixel arrangement of the CRA detector unit; Figures 4 through 6 each show a cross-section. Figure 1 Another alternative implementation of the optical detector unit of the camera system in the image.

[0041] Identical parts are identified by the same reference numerals in the accompanying drawings. Detailed Implementation

[0042] Figure 1 An example of camera system 1 is shown in cross-section. In the illustrated embodiment, the camera system is integrated into a mobile device, such as a smartphone. However, it should be noted that the concepts presented below can be well applied to other systems or devices, such as wearables. Camera system 1 comprises the following as its main components: an actual camera sensor system 2, the details of which are of less importance to the invention disclosed herein; and a dedicated sensor associated with it. In the illustrated embodiment, the dedicated sensor is an ambient light sensor 4, but in other embodiments, the design principles discussed herein can also be used in, for example, other dedicated sensors, such as a UV sensor. Camera sensor system 2 and ambient light sensor 4 are mounted on the back of a common cover glass 6, which may be the cover glass 6 of the smartphone itself. Ambient light sensor 4 is primarily used for the so-called “automatic white balance” function in camera system 1 to provide the necessary background information for appropriate correction functions, and thereby improve the overall image quality of camera system 1. In other embodiments, a UV sensor is provided as an alternative or supplement. Such a UV sensor can be used to determine measurements of the current UV load that may potentially affect exposed skin, for example in applications that provide specific UV warnings to users.

[0043] The ambient light sensor 4 comprises an optical detector unit 10 in the form and design of an optical sensor chip. It should be noted that the concepts presented herein can be applied to various types of optical sensor chips and optical arrangements, and the present invention only relates to the design of the optical detector unit 10 and thus it is fully possible to use the optical detector unit 10 in other applications within the scope of the present invention.

[0044] The multi-spectral sensor system 10 (in Figure 2 The multi-spectral sensor system 10 (in

[0045] In the context of the present disclosure, the "chief ray angle" will be understood as the angle between the optical axis of the respective unit 12, 14 and the axis of the incident irradiance from the dominant light source and thus also as the dominant "angle of incidence" of the ambient light measured in the ambient light sensor 4. According to one aspect of the present invention, the CRA detector unit 14 is provided in combination with the spectral detector unit 12 of the multi-spectral sensor system 10 in order to compensate for irradiance value changes due to changes in the tilt angle of the respective arrangement and in particular to compensate for the cosine error effect for ambient color and spectral sensing in the spectral detector unit 12 in tilt use cases.

[0046] As Figure 2As shown, the optical CRA detector unit 14 comprises a carrier or substrate 22 which provides mechanical support and electrical connections for the electronic components integrated into the multi-spectral sensor system 10. In the shown embodiment, the substrate 22 is designed in a so-called wafer-level-chip-scale-package (“WLCSP”) technology together with the electronic components integrated therein, as symbolized by the conductor elements 24. On the substrate 22, the optical CRA sensor unit 26 is arranged. In the particular embodiment shown, the optical CRA sensor unit 26 is integrated into a single semiconductor sensor die 28 together with other electronic components. The optical CRA sensor unit 26 comprises a plurality of individual optical detector elements or CRA detector pixels 30 all having the same spectral sensitivity. The pixels 30 are each composed of a photonic measurement cell and are realized as, for example, photodiodes in the shown embodiment.

[0047] According to an aspect of the present application, the optical CRA detector unit 14 is designed for a particularly compact yet mechanically stable layout, particularly usable in highly miniaturized packages. To achieve this, in the shown embodiment, the optical CRA detector unit 14 comprises an aperture element 32 which is arranged above the optical CRA sensor 26 with respect to the substrate 22. The aperture element 32 comprises a flat, laterally extending refractor element 34 which is a glass element in the shown embodiment, but can be selected from any other material deemed appropriate in view of, for example, appropriate refractive index, appropriate transmission characteristics, availability, cost, etc. Due to its essentially flat, laterally extending shape, the refractor element 34 defines a top surface 36 which, in the shown mounted state, faces away from the substrate 22 carrying the sensor unit 26, and a bottom surface 38 which, in the shown mounted state, faces towards the substrate 22 carrying the sensor unit 26. Figure 2 Figure 2

[0048] The top surface 36 as well as, equivalently, the bottom surface 38 are provided with a top aperture layer 40 and a bottom aperture layer 42, respectively. In the shown embodiment, the aperture layers 40, 42 are made of a material having a high absorption and a minimum transmission, such as “black chrome”. Alternatively, a suitably designed stack of interference filters comprising other metal layers can also be provided. The top aperture layer 40 is provided with a top CRA aperture 44. Correspondingly, the bottom aperture layer 42 is provided with a bottom CRA aperture 46. As Figure 2 ​​As shown, at their lateral positions in the top / bottom surfaces 36, 38, the top CRA aperture 44 and the bottom CRA aperture 46 are arranged such that the top CRA aperture 44 is positioned exactly on top of the bottom CRA aperture 46, thereby forming an effective aperture for the CRA sensor unit 26. The aperture layers 40, 42 can be easily deposited onto the glass substrate providing the refractive element 34 using modern standard deposition techniques with high accuracy. The apertures 44 and 46 in the top aperture layer 40 and the bottom aperture layer 42 can also be fabricated with high precision, for example, using photolithography.

[0049] Therefore, as Figure 2 As can be seen, the illustrated embodiment (in one aspect of the invention considered an independent invention) provides an optical CRA detector unit 14 that uses a glass-based refractive element 34 on top of a detector array, thereby defining the structure of the detector arrangement. The aperture element 32 is essentially composed of glass having a first (top) aperture layer 40 and a second (bottom) aperture layer 42. The CRA detector unit 14 includes the aperture element 32 in addition to a TSV chip having photodiodes providing sensor pixels 30. The FOV of the CRA sensor unit 26 is defined by the diameter of the glass 34 and the associated apertures 44, 46 on the first and second aperture layers 40, 44, the thickness of the glass 34, and the refractive index of the glass 34.

[0050] In another aspect of the invention, which is also considered an independent invention, the multispectral detector unit 12 of the multispectral sensor system 10 is constructed with a design similar to that of the CRA detector unit 14. Additionally, as... Figure 2 As shown, as part of the optical multispectral detector unit 12, the optical sensor unit 50 is arranged on the carrier 22 for detecting received photons. In this particular embodiment, the optical sensor 50 is also integrated into a single semiconductor sensor die 28 and includes multiple individual optical detector elements or multispectral detector pixels 52, which may be implemented as photodiodes, for example.

[0051] As other parts of the optical multispectral detector unit 12, a plurality of optical filters 54 are provided, such that each optical multispectral pixel 52 is associated with an associated optical filter 54 having different transmission characteristics. The pixel 52 and the associated filter 54 together form the detector channel 56 of the optical multispectral detector unit 12. The optical filter 54 may be an interference filter, such as an optical cutoff filter, bandpass filter, long-pass or short-pass filter, dielectric filter, Fabry-Perot filter, and / or polymer filter.

[0052] A control unit and a measurement unit (not shown) are integrated into the semiconductor sensor die 28 together with the optical multispectral sensor 16. The measurement unit can be regarded as a control unit of the optical sensor unit 2. It can provide, for example, the sensor signals generated by the optical sensor 50. The control unit and the measurement unit can be implemented as control logic, state machines, microprocessors, etc. They can also comprise additional components such as analog-to-digital converters, time-to-digital converters, amplifiers, which can also be located in the semiconductor sensor die 28. The semiconductor die 28 can have a printed circuit board, PCB, which provides electrical communication to the individual components of the multispectral sensor. In operation, the incident radiation can be detected by means of the optical sensor 50. Each optical multispectral sensor pixel 52 generates a multispectral sensor signal in response, respectively. The measurement unit thus provides a set of multispectral sensor signals in total.

[0053] In a conventional sensor unit with such a detector channel 56, the substrate 22 with the optical sensor 50 would be arranged in a housing which would be provided with an aperture in order to allow the light or radiation to pass through correctly. This aperture would be located within the field of view (FOV) of the optical sensor 50. The field of view of the optical sensor 50 comprises all points in space from which, at least theoretically, light from an external radiation or light source can propagate towards the optical sensor 50, e.g. for a fixed detector position and orientation.

[0054] Generally, the accuracy and reliability of the output signals provided by the optical sensor 50 can be limited and reduced by a number of factors. In particular, both static and dynamic sources of potential errors in the signals can be relevant. As an example of a static source of such errors, geometrical factors can become relevant. More precisely, the spectral sensitivity of the interference filter based multispectral sensor used in the illustrated embodiment strongly depends on the uniformity of the light impinging on the respective filter 54 of the detector pixels 52 in order to ensure that the response of the pixels 52 relative to each other is constant under different operating conditions. Considering that the FOV of the optical sensor 50 is limited by the aperture, the relative lateral position of the detector with respect to the aperture is important for the accuracy. Ideally, the sensor arrangement should be concentric with the aperture, thereby providing symmetric conditions for all individual pixels 52. However, the positioning and its accuracy can vary and be influenced by differences or tolerances in the packaging process during assembly of the detector unit 12 as well as the relative alignment of the components, thus potentially creating variations in the amplitude and spectral shape of the sensitivity due to variations in the angular power distribution.

[0055] To overcome or at least minimize this deficiency, in conventional systems a diffuser is to be provided on top of the aperture or in the region of the aperture in order to increase the uniformity of the incident radiation. However, as a further source of potential errors or misinterpretations of the pixels 52, in addition to effects resulting from the radiation source or light source itself, dynamic aspects such as tilting or angular displacement of the sensor arrangement relative to the dominant radiation source or light source should be considered. Depending on the performance of the integrated diffuser, the system accuracy is particularly dependent on the position of the dominant radiation point or light source as well. A light-diffusing object will scatter light more uniformly into the interior of the detector array than a dominant small point-type light source. Typically, each diffuser with the same transmittance ratio also has an ideal Lambertian distribution and will also vary the power distribution according to position (tilt relative to the detector) and spectral sensitivity.

[0056] Furthermore, the optical filters 54 are characterized by spectral transmission properties, respectively. In particular, they each have different spectral transmission properties; preferably, their transmittance properties can be linearly independent. Finally, the channels 56 have their own spectral sensitivity, can be susceptible to cross-talk and typically exhibit temperature dependence. The temperature profile of the channels 56 can be influenced by ambient temperature, device temperature, emitter temperature and thermal gradients in the optical arrangement. Any of these effects can contribute to errors in the sensor signal generation.

[0057] To overcome these potential deficiencies and provide a multispectral optical detector unit 12 with improved performance, according to one aspect of the present application, in the illustrated embodiment, the detector unit 12 employs a radically different concept to compensate for this radiation distribution, increase the uniformity of the incident radiation of the channels 56 and perform spectral reconstruction. To achieve this compensation, in the illustrated embodiment, the detector unit 12 is designed as a "one aperture per channel 56" layout rather than being provided with a common aperture shared by all channels 56.

[0058] In view of this design objective, the optical detector unit 12 in this aspect of the present application further comprises an aperture element 32 which is arranged above the optical sensor 50 relative to the substrate 22. The aperture element 32 further comprises a flat, laterally extending refractor element 34 which, in the illustrated embodiment, is a glass element but can be selected from any other material deemed appropriate in view of aspects such as suitable refractive index, suitable transmission properties, availability, cost, etc. As mentioned above, due to its essentially flat, laterally extending body, the refractor element 34 defines a top surface 36 which, in the mounted state as Figure 2 illustrated, faces away from the substrate 22 carrying the sensor unit 50 and a bottom surface 38 which, in the mounted state as Figure 2 illustrated, faces towards the substrate 22 carrying the sensor unit 50.

[0059] The top surface 36 and, equivalently, the bottom surface 38 are provided with a top aperture layer 40 and a bottom aperture layer 42, respectively. In order to provide an effective aperture for the channels 56 as well, the top aperture layer 40 is provided with a plurality of additional openings through which radiation can pass, thereby providing a top multi-spectral aperture 58 each. Correspondingly, the bottom aperture layer 42 is provided with a plurality of bottom multi-spectral apertures 60. As Figure 2 illustrated in their lateral positions in the top / bottom surfaces 36, 38, the top multi-spectral apertures 58 and the bottom multi-spectral apertures 60 are arranged in pairs, which means that each top multi-spectral aperture 58 is positioned right on top of a corresponding bottom multi-spectral aperture 60, thereby forming a plurality of dual apertures 62.

[0060] As Figure 2 can be seen, for each of the channels 56 in the detector channels 56, a separate aperture of the dual apertures 62 is provided which is associated therewith. The illustrated embodiment thus provides a detector unit 12 which is designed with a channelled aperture system and optical configuration using a glass-based refractor element 34 on top of the detector array, thereby defining the structure of the detector arrangement. The aperture element 32 essentially consists of glass with a first (top) aperture layer 40 and a second (bottom) aperture layer 42. The detector unit 12 comprises the aperture element 32 in addition to a TSV chip with photodiodes providing multi-spectral detector pixels 52. The FOV of each channel 56 and, correspondingly, the associated multi-spectral detector pixel 52 is defined by the diameter of the associated multi-spectral apertures 58, 60 on the glass 34 and the first and second aperture layers 40, 42 on the IC, the thickness of the glass 34 and the refractive index of the glass 34. The widely available aperture mask and the accurate process of wafer scale mounting guarantee that all spectral channels 56 have the same angular power distribution. In particular, the channelled optical separation defines similar optical performance (FOV, synchronous alignment, power distribution over the filter, etc.) for all color or spectral channels 56 without additional optics.

[0061] In a lateral perspective view, the channels 56 including the respective multi-spectral sensor pixels 52 and the associated dual apertures 62 can be positioned at a relatively large distance from each other, leaving a relatively large gap in between. This positioning freedom (made possible by the concept of assigning individual apertures to each channel 56) allows for an efficient use of the chip surface area, as electronic components, circuitry, etc. can be placed into the gap between the channels 56. Furthermore, optical cross-talk between adjacent channels 56 can be blocked by the minimum distance defined between the channels 56. Depending on the refractive index inside the glass 34, for example, the AOI will always be less than 41°. In relation to the glass thickness, this defines a minimum absorber width between the channels 56.

[0062] As Figure 2As can also be seen, in yet another aspect of the present invention, which is considered to be an independent invention, the multispectral sensor system 10 is designed in a fully integrated hybrid concept, which combines the multispectral detector unit 12 and the CRA detector unit 14. In particular, since the basic design concept of both units 12, 14 is similar, in the shown embodiment, they are designed in a combined package, sharing structural elements such as the substrate 22, the aperture element 32, the refractor element 34, the layers 42, 44, etc. In this hybrid concept, and in this aspect of the present invention, the optical CRA detector unit 14 can be understood as an additional channel of a multi-channel system with an array structure of optical CRA sensors 26 arranged behind the dual apertures 44, 46 dedicated to the optical CRA sensor 26, with respect to the design concept of the optical multispectral sensor unit 12 being the "one aperture per channel" approach. In this embodiment, the integration can even be exploited to the extent that, as Figure 2 shown, the CRA sensors 26 are positioned in the lateral direction between the individual ones of the channels 56 of the multispectral sensor 50.

[0063] The aperture element 32 can be positioned at a distance from the substrate 22 carrying the sensors 26, 50, thereby forming a gap between the top surface of the substrate 22 and the bottom aperture layer 42 of the aperture element 32. However, in the preferred embodiment as Figure 3a shown and in accordance with one aspect of the present invention, the aperture element 32 and its bottom aperture layer 42 are mounted directly on top of the substrate 22 and the optical sensors 26, 50. In this configuration, the aperture element 32, which enables additional functionality, also serves as a protection and cover for the sensors 26, 50 positioned below and for all potential additional electronics. Furthermore, in this way, the aperture element 32 can be considered to functionally replace the conventional cover for the sensor unit 26, 50, which is typically designed as a mold or overmold, compared to conventional sensor systems. In addition to the increased mechanical strength and durability provided by the aperture element 32 in this function compared to a typical overmold, the aperture element tends to have significantly less aging properties and also reduced temperature dependency, since the basic material is glass.

[0064] In the illustrated embodiment, the multi-spectral sensor system 10 is intended to be used as an ambient light sensor system with enhanced accuracy and precision. In this regard, the spectral detector unit 12 is designed as a rather conventional spectral ambient light sensor system. Thus, since in one aspect of the application, contrary to conventional systems and in order to save costs and allow for a small form factor package, the spectral detector unit 12 is not provided with a diffuser arranged on top, for a correct characterization of the incident radiation, it will be necessary to perform a correct spectral reconstruction, compensating appropriately for variations in the angle of illumination. This is particularly true for measurements of the total amount of incident radiation or irradiance or illuminance, which can strongly depend on the tilt angle of the respective device with respect to the incident radiation. The global value characteristic of the incident light intensity can be related to other signal processing, and for typical designs and layouts of the detector channels 56, the absolute value of the irradiance detection will decrease as a cosine function.

[0065] In order to be able to compensate for this variation, the optical CRA detector unit 14 is provided. According to one aspect of the application, each CRA detector pixel 30 is designed to generate an irradiance sensor signal. Since all CRA detector pixels 30 are designed to have the same spectral sensitivity, and after appropriate calibration to eliminate differences from the production process etc., a comparison of the irradiance sensor signals provided by the CRA detector pixels 30 can be used to generate a parameter characteristic of the dominant angle of incidence (AOI) for the irradiance of the detector system 10 or the "chief ray angle" (CRA) of the ambient light measured in the ambient light sensor 4. This parameter can later be used for the purpose of compensation or correction of the signals generated by the spectral detector unit 12. In the illustrated embodiment, the measurement unit is arranged to calculate the parameter characteristic of the angle of incidence (AOI) based on a calculation of the ratio of the irradiance sensor signals generated by any two of the CRA detector pixels 30.

[0066] In order to allow for such an angle of incidence determination, in one aspect of the application, the CRA detector unit 14 (in particular with respect to the arrangement of the CRA apertures 44, 46 with respect to the CRA sensor 26 positioned thereunder), in one aspect of the application, the CRA detector pixels 30 are arranged in a sensor array or structure within a base plane (in particular, the surface plane of the sensor die 28) defined by at least three of the CRA detector pixels 30.

[0067] In yet another aspect of the application, the CRA detector pixels 30 are arranged laterally to provide a rich information that can be used to determine the angle of incidence. Fig. 3 shows in a top view the arrangement of the CRA detector pixels 30 in two exemplary embodiments together with the apertures 44, 46 on top. The CRA pixels 30 that are covered by the aperture layers 40, 42 are shown in dashed lines, while the CRA pixels 30 that are directly below the apertures 44, 46 and thus not covered by the layers 44, 46 are shown in solid lines. Among others, Figure 3b A "square" or rectangular configuration of the CRA detector pixels 30 is shown together with matching square-shaped apertures 44, 46, while in Figure 3a In the shown embodiment, the CRA detector pixels 30 are arranged in a circular configuration, combined with circular-shaped apertures 44, 46.

[0068] In both shown embodiments, a plurality of CRA detector pixels 30o is located in a peripheral range of the sensor array or arrangement, and at least one of the CRA detector pixels 30c is located in a central region of the sensor arrangement, directly below a central region of the apertures 44, 46. In the shown embodiments, and according to yet another aspect of the application, the CRA detector pixels 30o of the outer side are arranged in pairs at opposite positions relative to the central pixel 30c, so that a relative difference of illumination in a direction defined by such pairs of pixels 30o can be easily detected and evaluated. In other words, in the shown arrangement, each of the CRA detector pixels 30c located in a peripheral range of the sensor arrangement is associated with at least one other pixel of the CRA detector pixels 30o located in a peripheral range in an opposite position relative to the center of the sensor array.

[0069] To facilitate the effect of measuring the tilt angle or illumination angle, in an aspect of the application that is considered to be an independent invention, the two CRA apertures 44, 46 are designed to be smaller or narrower compared to the lateral extension or dimension of the underlying sensor arrangement, so that at least some of the peripheral pixels 30o are at least partially covered by the layers 40, 42. This design principle will ensure to enable the respective CRA detector pixels 30o to detect the incident radiation, especially in case the direction of the light is tilted relative to the system and the portion below the edges of the apertures 44, 46 is illuminated. In other words, in embodiments of the application, the width w of the apertures 44, 46 is smaller than the lateral dimension W of the sensor arrangement. Depending on the basic geometry, respectively, for a rectangular system as Figure 3b The width w and the lateral dimension W can be understood as the side length of the pattern, while in a circular arrangement as Figure 4a The width w and the lateral dimension W can be understood as the side length of the pattern, while in a circular arrangement as

[0070] In a preferred embodiment, and in accordance with one aspect of the present application, the width w of the aperture 44, 46 can be selected to be about 50% of the lateral dimension of the sensor arrangement. In a preferred embodiment, the width of the aperture 44, 46 can be about 200 μιη, while the lateral dimension W of the sensor arrangement can be about 400 μιη.

[0071] In yet another embodiment of the present application, the CRA detector pixels 30 are positioned in segments of the sensor die 28 that are equipped with other electronic systems. Since the CRA detector sensor 26 requires a relatively small number of individual sensor pixels 30 that can be well distributed over a relatively large area, the free space in between can be well used to accommodate other components or electronic elements. In particular, pixel gaps of relatively small size of the aperture can be provided, and the pixels 30 can be distributed between other IC structures in the sensor die 28.

[0072] In another embodiment of the present application, the multi-spectral sensor system 10' can be designed as shown in a cross-section in Figure 4b and a top view in Figure 4b In this embodiment, one single aperture system can be provided instead of the "one aperture per channel 56" design discussed above, including a top aperture 64 and a bottom aperture 46 for both the CRA detector pixels 30 and the multi-spectral detector pixels 52, while still maintaining the hybrid integrated structure providing a single common aperture element 30 for both the multi-spectral detector unit 12 and the CRA detector unit 14. In this embodiment, as shown in a top view of the underlying pixel arrangement in Figure 5a the multi-spectral detector pixels 52 can be arranged at the center of the compact detector array, while the CRA detector pixels 30 can be arranged in corner structures 68 in the outer boundary region of the sensor array. In embodiments, such corner order boundary related structures can approve measurements or detect diffuse distribution for dominant sources in the valid AOI.

[0073] In a similar embodiment of the present application, the multi-spectral sensor system 10" can be designed as shown in a cross-section in Figure 5b and a top view in Figure 5b In this embodiment, one single aperture system can also be provided, including a top aperture 64 and a bottom aperture 66 for both the CRA detector pixels 30 and the multi-spectral detector pixels 52, while still maintaining the hybrid integrated structure providing a single common aperture element 30 for both the multi-spectral detector unit 12 and the CRA detector unit 14. In this embodiment, as shown in a top view of the underlying pixel arrangement in Figure 6aAs shown in the top view, in addition to the previously described setup, an additional CRA detector pixel 30 can be arranged at the center of the array and multispectral detector pixel 52. Specifically, the profile can be provided by a diode structure or by a second aperture overlapping the diode, thereby reducing alignment correlation.

[0074] In yet another similar embodiment of the invention, the multispectral sensor system 10'" can be designed as follows Figure 6b The cross section and Figure 5b As shown in the top view. In this embodiment, a single-aperture system can also be provided, which includes a top aperture 64 and a bottom aperture 66 for both the CRA detector pixel 30 and the multispectral detector pixel 52, while still maintaining a hybrid integrated structure that provides a single common aperture element 30 for both the multispectral detector unit 12 and the CRA detector unit 14. In this embodiment, as with the potential pixel arrangement ​ As shown in the top view, the four corner pixels of the CRA detector pixel 30 can be set together with the additional CRA detector pixel 30 arranged at the center of the array and multispectral detector pixel 52.

[0075] In the operation of the multispectral sensor system 10, 10', 10", 10'", received photons are detected by means of CRA detector unit 14. In response, optical CRA sensor 26, including CRA detector pixels 30, generates irradiance sensor signals for each CRA detector pixel 30, and based on these sensor signals, calculates the parametric characteristics of the principal ray angle (CRA) or incident angle (CRA) of the irradiance of the detector unit. Specifically, and according to one aspect of the invention, the parametric characteristics for the principal ray angle (CRA) are calculated based on the ratio of the irradiance sensor signals generated by any two pixels of the CRA detector pixels 30.

[0076] Other received photons are detected by means of the arranged optical spectral sensor unit 12. For each multispectral detector pixel 52 of the optical spectral sensor 50 (each pixel has different spectral transmission characteristics), a multispectral sensor signal is generated, and a modified multispectral sensor signal is calculated for each multispectral sensor signal by compensating the corresponding multispectral sensor signal using the parametric characteristics of the principal ray angle (CRA), and the modified multispectral sensor signal is provided as the output signal of the multispectral sensor system.

[0077] The embodiments of the optical multispectral sensor system 10, 10', 10", 10'" discussed herein have been disclosed for the purpose of familiarizing the reader with the novel aspects of the present concept. Although preferred embodiments have been shown and described, those skilled in the art will readily understand that many changes, modifications, equivalents, and substitutions can be made to the disclosed concept without necessarily departing from the scope of the claims.

[0078] In particular, the present disclosure is not limited to the disclosed embodiments and gives examples of as many alternatives as possible of the features included in the discussed embodiments. However, it is intended that any modifications, equivalents and substitutions of the disclosed concept be included within the scope of the appended claims.

[0079] The features recited in the individual dependent claims can be combined advantageously with one another. Furthermore, the use of reference signs in the claims is not to be interpreted as limiting the scope of the claims.

[0080] Furthermore, as used herein, the term "comprising" does not exclude other elements. In addition, as used herein, the term "a" or "an" is intended to refer to one or more of the described elements or components, and is not limited to a single one of the described elements or components.

[0081] Unless explicitly stated otherwise, any method set forth herein is not construed as requiring its steps to be performed in a particular order. Hence, if a method claim does not actually recite a specific order thereof, or if an order is not otherwise specifically recited in the claims or specification, it is in no way intended to be inferred as requiring any particular order of steps.

[0082] List of reference signs

Claims

1. An optical CRA detector unit (14) comprising an optical CRA sensor (26) arranged on a substrate (22), wherein, The optical CRA sensor (26) comprises a plurality of CRA detector pixels (30) having the same spectral sensitivity, each CRA detector pixel generating an irradiance sensor signal, wherein the irradiance sensor signals generated by the CRA detector pixels (30) are provided for generating a parametric characteristic of the chief ray angle (CRA) of the irradiance of the CRA detector unit (14), and the optical CRA detector unit comprises an aperture element (32) arranged above the optical CRA sensor (26) relative to the substrate (22), the aperture element (32) comprising a flat, laterally extending refractor element (34) defining a top surface (36) and a bottom surface (38), wherein the top and bottom surfaces (36, 38) are provided with a top aperture layer (40) and a bottom aperture layer (42), respectively, and wherein the top aperture layer (40) is provided with a top aperture (44) and the bottom aperture layer (46) is provided with a bottom aperture (46), the lateral dimension of the bottom aperture being at least the lateral dimension of the top aperture (44).

2. The optical CRA detector unit (14) according to claim 1, wherein The CRA detector pixels (30) are arranged in a sensor array within a base plane defined by at least three of the CRA detector pixels (30).

3. The optical CRA detector unit (14) according to claim 2, wherein A plurality of the CRA detector pixels (30o) are located in a peripheral range of the sensor array, and at least one of the CRA detector pixels (30c) is located in a central region of the sensor array within the base plane.

4. The optical CRA detector unit (14) according to claim 3, wherein Each of the CRA detector pixels (30o) located in the peripheral range of the sensor array is associated with at least one other pixel of the CRA detector pixels (30o) located in the peripheral range in a relative position relative to a center of the sensor array.

5. The optical CRA detector unit (14) according to any one of claims 2 to 4, wherein, An aperture width (w) of the bottom aperture (46) is smaller than a lateral dimension (W) of the sensor array in the base plane.

6. The optical CRA detector unit (14) according to any one of claims 1 to 5, wherein Each of the CRA detector pixels (30) consists only of a photon measurement unit, preferably only of a photodiode.

7. The optical CRA detector unit (14) according to any one of claims 1 to 6, further comprising a measurement unit configured for providing a sensor signal generated by the optical sensor (26), wherein, The measurement unit is arranged for calculating the parametric characteristic of the chief ray angle (CRA) based on a calculation of a ratio of irradiance sensor signals generated by any two of the CRA detector pixels (30).

8. The optical CRA detector unit (14) according to any one of claims 1 to 7, wherein, The refractor element (34) is a glass element.

9. The optical CRA detector unit (14) according to any one of claims 1 to 8, wherein, The aperture element (32) and the bottom aperture layer (42) of the aperture element are mounted directly on top of the substrate (22) and the optical sensor (26).

10. A multispectral sensor system (10) comprising an optical CRA detector unit (14) according to any one of claims 1 to 9 and a spectral detector unit (12), the spectral detector unit (12) comprising an optical spectral sensor (50) arranged on a substrate (22) for detecting received photons and the spectral sensor (50) comprising a plurality of multispectral sensor pixels (52) each generating a multispectral sensor signal as part of one of a plurality of detector channels (56), and - an aperture element (32) is arranged above the spectral sensor (50) with respect to the substrate (22), the aperture element (32) comprising a flat, laterally extending refractor element (34) defining a top surface (36) and a bottom surface (38), wherein: - the top and bottom surfaces (36, 38) are each provided with a top aperture layer (40) and a bottom aperture layer (42), - the top and bottom aperture layers (40, 42) are each provided with a plurality of top and bottom multispectral apertures (58, 60), the top and bottom multispectral apertures (58, 60) being arranged in pairs thereby forming a plurality of dual apertures (62) such that in each of the dual apertures (62) the top multispectral aperture (58) is arranged on top of the bottom multispectral aperture (60) corresponding to the top multispectral aperture, and - for each of the detector channels (56) a single one of the dual apertures (62) is provided which is associated with each channel.

11. The multispectral sensor system (10) according to claim 10, wherein Each of the detector channels (56) of the spectral sensor (50) comprises at least one of the multispectral pixels (52) and an optical filter (54) associated with the at least one pixel.

12. The multispectral sensor system (10) according to claim 11, wherein For at least one of the channels (56) the optical filter (54) is arranged on top of the top multispectral aperture (58) of the dual aperture (62) associated with the at least one channel.

13. The multispectral sensor system (10) according to any one of claims 10 to 12, wherein The aperture element (32) and the bottom aperture layer (42) thereof are directly mounted on top of the substrate (22) and the optical sensor (50).

14. The multispectral sensor system (10) according to any one of claims 10 to 13, wherein The multispectral sensor channels (56) each have different spectral transmission characteristics.

15. The multispectral sensor system (10) according to any one of claims 10 to 14, wherein The optical CRA sensor (26) of the optical CRA detector unit (14) and the optical spectral sensor (50) of the spectral detector unit (12) are arranged on the same substrate (22) and the same aperture element (32) is provided above the optical CRA sensor (26) of the optical CRA detector unit (14) and the optical spectral sensor (50) of the spectral detector unit (12).

16. The multispectral sensor system (10) according to any one of claims 10 to 15, the multispectral sensor system being designed as an ambient light sensor (4).

17. A camera system (1) comprising an ambient light sensor (4) according to claim 16.

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