Optical detector unit, multispectral optical sensor and method for multispectral light sensing

Abstract

An optical detector unit (10) comprising an optical sensor (16) arranged in a chamber (14) having an aperture (18) within a housing (12), the optical sensor (16) being arranged to detect photons received through the aperture (18); and a diffuser (22) arranged on top of the aperture (18) on the housing (12), should provide enhanced accuracy and data reliability. According to the invention, this is achieved in that the optical sensor (16) comprises an array (36) of sensor pixels (38s) of a first type and pixels (38c) of a second type, the pixels (38s) of the first type each having a different spectral transmission characteristic, each generating a multispectral sensor signal, and the pixels (38c) of the second type having the same transmission characteristic, each generating a multispectral sensor signal. Compensation sensor signals are each generated, and wherein the compensation sensor signals generated by the pixels (38c) of the second type are provided for generating compensation parameters for each sensor pixel (38s).

Description

Technical Field

[0001] The present invention relates to an optical detector unit. More specifically, the present invention relates to an optical detector unit including an optical sensor disposed in a chamber having a hole in a housing, the optical sensor being arranged to detect received photons passing through the hole; a diffuser disposed on top of the hole in the housing; and a measurement unit configured to provide a sensor signal generated by the optical sensor. The present invention also relates to a multispectral sensor including such an optical detector unit, and to a method for multispectral light sensing. Background Art

[0002] Optical sensors are increasingly being used in various technical fields such as smartphones and mobile devices, smart homes and buildings, industrial automation, medical technology, and connected vehicles. At the same time, sensor data is becoming more complex and there is a desire to meet the requirements of high accuracy. In addition, chip-level color and spectral light sensing has various applications in color recognition, data authentication, spectroscopy, and other industrial and consumer-level optical detection applications. In many important applications, especially in camera applications, such sensors are used as ambient light sensors for the so-called "auto white balance" functionality in order to provide the necessary background information for proper correction functionality, thereby generally improving the imaging quality.

[0003] Common multispectral sensors typically are based on a pixel array and a pixel-on filter for each pixel. For spectral applications, filters with linearly independent filter characteristics can be selected. 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 signal of the pixels can be used to calculate the spectral reconstruction of the light source under study.

[0004] However, the uniform distribution of the incident radiation on the pixel array is an ideal condition. Especially when used in ambient light sensor devices, the uniformity of the incident light distribution may be of particular significance, and in order to provide a highly reliable uniform distribution, a diffuser can be used at a position before the incident radiation reaches the pixels in order to mix the incident light as much as possible and deliver the light to the sensor array in a uniform (ideally in a Lambertian form) manner. In addition, the spectral sensitivity of a multispectral sensor based on interference filters depends to a large extent on the angular distribution of the light incident on the filter of the detector array.

[0005] In addition, in many existing sensor devices for averaging the limitations of the field of view (“FOV”), the lid aperture is used in combination with a diffuser on top of the aperture or in front of the aperture with respect to the direction of the incident light, in order to collect and mix the incident light from a relatively wide angle of incidence (up to 180°). However, due to insufficient tolerances and precision in the encapsulation during the assembly process, the position of the lid relative to the underlying sensor array may vary significantly. This change in relative position may result in changes in the magnitude and spectral shape of the sensitivity due to changes in the angular power distribution. Depending on the array position, each channel will be affected in a different way. The change in the angular distribution will cause a change in the spectral sensitivity.

[0006] Depending on the performance of the associated diffuser, the system accuracy may also depend on the position of the dominant radiation point. A wide diffuser object will scatter light more uniformly inward into the detector array than a dominant and small point. Generally, each diffuser with a common transmittance also has an ideal Lambertian diffusion and will also change the power distribution depending on the position (tilt relative to the detector) and spectral sensitivity. Knowledge of the settings depending on the spectral sensitivity is important for generating a useful transfer matrix for spectral reconstruction.

[0007] To compensate for these aspects, different measurement systems have been proposed. These systems are based on a robust optical construction or a strictly defined measurement geometry, for example, measuring at defined angles such as 45° / 0° or 22.5° / 22.5°, or using an integrating sphere. Such systems are typically used for color measurements with strictly faded glossiness and a constant measurement distance. To compensate for the non-uniform radiation distribution through the optical device, one possibility is to use a diffuser and an optical lens for mixing. However, the field of view (FOV) and size ratio are usually not practical. Other solutions employ image analysis using an image camera, which may help obtain additional information about the characteristics of the measurement surface. In low-cost systems, additional spacers for the contact surface are often used. However, the market demand for non-contact measurements is increasing. Summary of the Invention

[0008] Accordingly, it is an object of the present invention to provide an improved optical detector unit of the above-determined type, including an optical sensor having an array of detector elements or pixels, which helps to overcome the above-determined drawbacks. In addition, an improved multi-spectral sensor and an improved method for multi-spectral light sensing should be provided.

[0009] Regarding the optical detector unit, this object is achieved by:

[0010] - The optical sensor includes an array of sensor pixels of a first type and pixels of a second type,

[0011] - Each pixel of the first type has different spectral transmission characteristics, generates a multispectral sensor signal respectively, and

[0012] - Each pixel of the second type has the same transmission characteristics and generates a compensation sensor signal respectively,

[0013] wherein the compensation sensor signal generated by the pixels of the second type is provided for generating a compensation parameter for each sensor pixel.

[0014] The preferred embodiments are the subject matter of the dependent claims.

[0015] The present invention is based on the following considerations: In order to overcome these potential defects and provide a multispectral sensor with improved performance, the detector unit should be provided with means for compensating such radiation distribution and for spectral reconstruction. To achieve such compensation, the detector unit should be enabled to calculate the compensation parameter for each sensor pixel.

[0016] According to one aspect of the present invention, such enabling can be achieved by dividing the sensor pixels of the optical sensor into two subgroups. The pixels of the first subgroup can be used as "conventional" sensor pixels, while the pixels of the second subgroup can be designed as compensation pixels, i.e., for compensation purposes. Thus, in an embodiment of the present invention, the optical sensor can include an array of sensor pixels of the first type and pixels of the second type. The pixels of the first type are designed as "conventional" sensor pixels and thus each has different transmission characteristics. However, the pixels of the second type can be dedicated to generating compensation sensor signals. Then, these signals can be processed to calculate the compensation parameter for each sensor pixel.

[0017] In one aspect of the present invention, the calculation of the compensation parameter can be performed in an external computing or arithmetic device. In a preferred embodiment and according to an embodiment of the present invention, through a particularly compact and general arrangement, the optical detector unit itself is configured to provide sensor signals in this "compensation mode". In this preferred embodiment, the detector unit can include an integrated measurement unit, which is arranged to calculate the compensation parameter for each sensor pixel and modify the multispectral sensor signal generated by each pixel of the first type by the compensation parameter calculated for the corresponding pixel, so as to obtain the compensated multispectral sensor signal of each pixel of the first type. In yet another preferred embodiment, the measurement unit is arranged to modify the multispectral sensor signal generated by each pixel by the compensation parameter calculated for the corresponding pixel, so as to obtain the compensated multispectral sensor signal of each pixel of the first type.

[0018] In a preferred embodiment, the different transmission characteristics of the first type of pixels are linearly independent. These pixels can be regarded as channels of a multispectral sensor. Furthermore, in another aspect of the present invention, in view of the intended application or use of the detector unit in an ambient light sensor (ALS), it is preferred to provide 5 to 12 channels with different transmission characteristics, in particular peak spectral sensitivities. Given this preferred channel number range and considering the desired at least approximate reconstruction of the detected spectrum in the visible range, in a preferred embodiment, the spectral sensitivity of some or each channel has a cosine shape, where the full width at half maximum (FWHM) is approximately equal to the spacing between adjacent peaks. In yet another embodiment, the spectral sensitivity of one or each channel can have a Gaussian shape.

[0019] According to a preferred aspect of the present invention, at least the first type of pixels each include a photodiode and a filter, where the filter determines the transmission characteristics of the corresponding sensor pixel.

[0020] According to one aspect of the present invention, in a sensor array, compensation pixels are positioned such that they allow for the calculation of compensation parameters in out-of-plane extrapolation / interpolation. Thus, in view of the fact that a plane is defined by three reference points, in a preferred embodiment, at least three compensation pixels are provided in the sensor array. In the case of incident illumination by a radiation source, individual sensor measurements can be obtained for each compensation pixel, and on this basis, appropriate compensation values can be calculated for each sensor pixel by linear extrapolation / interpolation in the plane established by the sensor array.

[0021] According to yet another aspect of the present invention, in order to cover as large a surface as possible between them and provide measurement value differences due to geometric parameters such as component tilt and / or light source position, at least some or preferably most of the compensation pixels should be positioned as far as possible outside the sensor array. In a preferred embodiment, the compensation pixels are thus positioned in the (outer) corners of the sensor array. In another preferred embodiment, in one aspect of the present invention, in combination with the corner pixels mentioned above, at least one second type of pixel is located in the central region of the sensor pixel array, thereby providing a reference for the pixels that are expected to receive the maximum illumination under normal conditions.

[0022] Regarding the multispectral sensor, the above-mentioned object is achieved by the multispectral sensor including an optical detector unit of the above type. Furthermore, in a preferred embodiment and according to yet another aspect of the present invention, the multispectral sensor is intended to be used as an ambient light sensor, particularly for a camera system. In different applications, the multispectral sensor can further include a light emitter unit, and in yet another preferred embodiment, the light emitter unit includes a light emitter that can be arranged in a chamber with holes in a housing.

[0023] Regarding a method for multispectral light sensing, according to one aspect of the present invention, the above-mentioned determination objective is achieved through the following steps:

[0024] - Detecting received photons through a hole in a chamber by means of an optical sensor disposed in the chamber of the housing,

[0025] wherein the optical sensor includes an array of sensor pixels of a first type and pixels of a second type,

[0026] - Generating a multispectral sensor signal for each pixel of the first type,

[0027] - Generating a compensation sensor signal for each pixel of the second type,

[0028] - Calculating a compensation parameter for each sensor pixel from the compensation sensor signals generated by the pixels of the second type,

[0029] - Modifying the multispectral sensor signals generated by each pixel with the compensation parameters calculated for the corresponding pixels, and

[0030] - Providing the modified multispectral sensor signals as output signals of the optical detector unit.

[0031] In one aspect of the present invention, a camera system is also proposed, preferably for a smart phone or a wearable device, the camera system including an ambient light sensor having an optical detector unit of the above-mentioned determined type.

[0032] Due to the basic concept of the present invention, it can be seen that the main advantages achieved by the present invention are:

[0033] - Defining corner pixels (without filters) on the multispectral detector array,

[0034] - Using arbitrary pixels to achieve different spectral sensitivities (filters), and

[0035] - Supporting a method for compensating spectral reconstruction variations,

[0036] Higher reliability of the sensor output can be achieved.

[0037] The proposed use of corner pixels for compensating pixels allows the detection and compensation of geometric effects that generate spectral reconstruction variations. This also allows the use of larger single spectral channels or more channels with a better fill factor, thereby increasing the performance and accuracy of the detector. In particular, depending on the position of the hole relative to the pixel array position (package misalignment) and / or different AOIs of external dominant sources, the four corner pixels will obtain different signals.

[0038] It is possible to simultaneously detect and compensate for the effects of constant offsets (e.g., due to package misalignment) and dynamic variations (e.g., due to tilt and / or dominant sources). Based on these parameters, the reconstruction matrix can be spectrally compensated. In a preferred embodiment, the geometrically dependent variations of the channel-wise spectral sensitivities can be simulated and stored as a calibration data set (e.g., in a look-up table).

[0039] A further advantage can be seen in that the values and directions of package misalignment (pixel-level offset and spectral distortion) can be detected and compensated. It is possible to distinguish between uniform offsets and position-dependent dynamic effects, such as dominant small objects (dynamic variations in specific applications). In addition, support parameters and methods for spectral compensation under non-ideal Lambertian diffuse light coupling can also be provided. Furthermore, due to the use of a single spectral channel, the sensitivity of the detector can be increased by a larger detector size and a better fill factor or the availability of more different spectral channels. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The preferred embodiments and aspects of the present invention will be further described below in conjunction with the accompanying drawings. In the drawings:

[0041] Figure 1 A camera system is shown, particularly for a smartphone,[[]]END]]

[0042] FIG. 2 schematically shows the radiation patterns of various embodiments of the diffuser,[[]]END]]

[0043] Figure 3 is shown[[]]END]] Figure 1 a cross-sectional view of the optical detector unit of the camera system of;

[0044] Figures 4 to 6 Each shows an embodiment of an optical sensor for a multispectral sensor;

[0045] Identical components are labeled with the same reference numerals.[[]]END]] DETAILED DESCRIPTION

[0046] Figure 1 An example of a cross-sectional view of the camera system 1 is shown. In the illustrated embodiment, the camera system is integrated into a mobile device such as a smartphone. The camera system 1, as its main components, includes an actual camera sensor system 2, the details of which are of less significance for the invention of the present disclosure, and an associated ambient light sensor 4. The camera sensor system 2 and the ambient light sensor 4 are mounted on the back of a common cover glass 6, which can be the cover glass 6 of the smartphone itself. The ambient light sensor 4 is mainly used for the so-called "auto white balance" functionality in the camera system 1 in order to provide the necessary background information for proper correction functionality, thereby generally improving the imaging quality of the camera system 1.[[]]END]]

[0047] The ambient light sensor 4 includes an optical detector unit 10 in the form and design of an optical sensor chip. It should be noted that the concept proposed by the present invention is applicable to various types of optical sensor chips and optical devices, and the present invention only relates to the design of the optical detector unit 10. Therefore, within the scope of the present invention, this design can be fully used for the optical detector unit 10 in other applications.

[0048] The optical detector unit 10 of the ambient sensor 4 includes a housing 12 having a sensor chamber 14, and the actual sensor unit 16 is positioned in this sensor chamber. To allow light or radiation to appropriately pass through the housing 12 to reach the sensor unit 16, the housing 12 is provided with an opening or hole 18. The hole 18 is covered by an infrared cut-off filter 20, which in turn is covered by a diffuser 22. The diffuser 22 is positioned directly adjacent to the cover glass 6. For illustration, the field of view of the camera detection system 2 and the field of view of the ambient light sensor 4 are also shown in Figure 1 and are labeled as cones 24, 26 respectively.

[0049] FIG. 2 schematically shows the radiation patterns for various types and / or situations of the diffuser 22. In an ideal system, as Figure 2a shown, the diffuser 22 should fully mix and re-scatter the light or radiation entering through the cover glass 6, thereby generating a so-called Lambertian-shaped hemispherical (semicircular in cross-sectional view) radiation pattern 28a. This "ideal" radiation pattern will result in a nearly laterally uniform exposure of the sensor unit 16 located below the diffuser 22. In particular, in such an ideal system, the sensor unit 16 will detect and be limited by the hole 18 behind the diffuser 22. However, in a real system, deviations from this ideal behavior must be expected, which may be due to defects in the diffuser 22 or surrounding components, or a reduction in the diffusing characteristics in order to increase the transmittance, thereby generating a more droplet-shaped radiation pattern 28b as shown in Figure 2b or may be due to the main light source incident at an oblique angle, resulting in a radiation pattern 28c as shown in Figure 2c Obviously, in the latter two cases, the influence of the incident radiation on the sensor unit 16 below the diffuser is laterally non-uniform.

[0050] The optical detector unit 10 of the ambient sensor 4 is shown in Figure 3 in an enlarged cross-sectional view. As shown in Figure 3As shown, the housing 12 of the detector unit 10 is arranged on a substrate or carrier 30. A cover section or cover body 32 forming the hole 18, which is at the same time part of the housing 12, is opposed to the carrier 30 so as to cover the chamber 14. The carrier or substrate 30 provides mechanical support and electrical connection for the electronic components integrated into the optical detector unit 10. For example, the carrier 30 may include a printed circuit board (PCB) (not shown). However, in other embodiments (not shown), the carrier 30 may also be part of the housing 12 and the electronic components may be embedded in the housing 12 by, for example, molding.

[0051] As part of the optical detector unit 10, the optical sensor unit 16 is arranged within the chamber 14 and on the carrier 30. In this particular embodiment, the optical sensor 16 and other electronic devices are integrated into a single semiconductor sensor chip 34. The optical sensor includes an array 36 of individual optical detector elements or pixels 38, which will be discussed in further detail below. For example, the pixel 38 may be implemented as a photodiode.

[0052] As another part of the optical detector unit 10, an array 40 of optical filters 42 is arranged in the chamber 14 above the optical sensor unit 16. The array 40 of filters 42 is attached to the optical sensor 16. Each pixel 38 is associated with an associated filter 42 having different transmission characteristics. The pixel 38 and the associated filter 42 together form a channel 44 of the optical detector unit 10. The optical filter 42 may be an interference filter, such as an optical cut-off filter, band-pass, long-pass or short-pass filter, dielectric filter, Fabry-Perot filter and / or polymer filter.

[0053] To allow light or radiation to pass through properly, the lid or cover body 32 of the housing 12 is provided with a hole 18. The hole 18 is positioned above the optical sensor 16. In fact, the hole 18 is within the field of view (FOV) of the optical sensor 16. The field of view of the optical sensor 16 includes all points in space from which, at least in theory, light from an external radiation source or light source can propagate towards the optical sensor 16, for example, for a fixed detector position and orientation.

[0054] The control unit 50 and the measurement unit 52 are integrated together with the optical sensor 16 into the semiconductor sensor chip 34. The measurement unit 52 can be regarded as the control unit for the optical sensor unit 2. For example, this measurement unit provides the sensor signals generated by the optical sensor 16. The control unit 50 and the measurement unit 52 can be implemented as control logic, state machines, microprocessors, etc. They can also include additional elements such as an analog-to-digital converter, a time-to-digital converter, an amplifier, which are also located in the semiconductor sensor chip 34. The semiconductor chip 34 can have a printed circuit board PCB that provides electrical communication for the various components of the multispectral sensor. During operation, the incident radiation entering through the hole 18 can be detected by the optical sensor 16. Each sensor pixel 38 generates a multispectral sensor signal respectively in response. Thus, the measurement unit 52 provides a set of multispectral sensor signals in total.

[0055] Generally, the accuracy and reliability of the output signals provided by the optical sensor 16 can be limited and reduced by various factors. Specifically, both the static and dynamic sources of potential errors in the signals can be correlated. As an example of such a static source of error, geometric factors can become relevant. More precisely, the spectral sensitivity of the interference filter-based multispectral sensor as used in the illustrated embodiment depends to a large extent on the angular distribution of the light incident on the corresponding filter 42 of the detector array 36. Considering that the FOV of the optical sensor 16 is limited by the hole 18 in the housing 12, the relative lateral position of the detector array 36 with respect to the hole 38 is of great significance for accuracy. Ideally, the sensor array 36 should be concentric with the hole 38, thus providing symmetric conditions for all individual pixels 38. However, the positioning and its accuracy can vary due to differences or tolerances in the encapsulation process during the assembly of the detector unit 2 and the relative alignment of the components, and thus may cause changes in the sensitivity amplitude and spectral shape due to changes in the angular power distribution.

[0056] As another source of potential errors or misreadings of the pixel 38, as explained above in the context of FIG. 2, dynamic aspects such as the tilt or angular displacement of the sensor device relative to the dominant radiation or light source and the effects generated by the radiation source or light source itself should be considered. Depending on the performance of the integrated diffuser, the accuracy of the system also depends particularly on the position of the dominant radiation point or light source. A wide diffusing object will scatter light more uniformly into the detector array 36 than a dominant and small point-type light source. Generally, each diffuser with a common transmittance also has an ideal Lambertian diffusion and will also change the power distribution depending on the position (tilt relative to the detector) and spectral sensitivity.

[0057] In addition, the optical filters 42 are each characterized by their spectral transmission characteristics. Finally, the channels 44 have their own spectral sensitivities, may be susceptible to crosstalk, and typically exhibit temperature dependence. The temperature distribution of the channels 44 can be affected by the ambient temperature, the device temperature, the emitter temperature, and the thermal gradients in the optics. Any of these effects can lead to errors in the generation of the sensor signals.

[0058] To overcome these potential drawbacks and to provide a multispectral optical detector unit 10 with improved performance, in accordance with one aspect of the present invention, the detector unit 10 in the illustrated embodiment has means for compensating for such radiation distribution and for performing spectral reconstruction. To effect such compensation, the detector unit 10 in the illustrated embodiment is implemented to calculate compensation parameters for each channel 44.

[0059] In accordance with one aspect of the present invention, this is achieved by providing a subgroup of the sensor pixels 38 of the optical sensor 16 and by designing the pixels 38 of this subgroup as compensation pixels 38c. Thus, in an embodiment of the present invention, the optical sensor 16 includes an array 36 of a first type of sensor pixels 38s and a second type of pixels 38c. The first type of pixels 38s are designed as "conventional" sensor pixels 38s and thus each have different transmission characteristics. However, the second type of pixels 38c are associated with an optical filter 42 having the same transmission characteristics or are not associated with an optical filter. In the latter case, their transmission characteristics are determined by the characteristics of the pixels 38c themselves. Each second type of pixel 38c (hereinafter simply referred to as a compensation pixel) generates a compensation sensor signal, which as a whole results in a set of compensation sensor signals. These signals can be processed to calculate the compensation parameters for each sensor pixel 38s.

[0060] In accordance with one aspect of the present invention, in the sensor array 36, the compensation pixels 38c are positioned such that they allow the calculation of the compensation parameters in an out-of-plane extrapolation / interpolation. Thus, in the sensor array 36, at least three compensation pixels 38c are provided, since a plane is defined by three reference points. In the case of incident illumination by a radiation source, individual sensor measurements can be obtained for each compensation pixel 38c, and on this basis, appropriate compensation values can be calculated for each sensor pixel 38s by linear extrapolation / interpolation in the plane established by the sensor array 36.

[0061] In view of the spirit of the present invention, as mentioned above, at least three compensation pixels 38c should be provided. Generally, the compensation pixels 38c can be located anywhere in the detector array 36. However, according to yet another aspect of the present invention, at least some or preferably all of the compensation pixels 38c should be located as far as possible outside the sensor array 36, in particular in order to cover as large a surface as possible between them and to provide the maximum difference in the measured values due to geometric parameters such as component tilt and / or light source position. In a preferred embodiment, the compensation pixels 38c are located in the (outer) corners 60 of the sensor array. In other words: in one aspect of the present invention, the corner pixels 38c of the sensor array 36 are designed for the functionality of the compensation pixels 38c.

[0062] Figure 4 An embodiment of the optical sensor 16 for the optical detector unit 10 in accordance with these considerations is shown. The drawing shows a top view of an array 36 of pixels 38 arranged in a 4×4 configuration. Four compensation pixels 38c are distributed symmetrically and are located in the corners 60 of the pixel array 36. The remaining pixels 38 are sensor pixels 38s. The array 40 of optical filters 42 is not shown in this schematic, but the array of optical filters is aligned with the pixels 38s in the pixel array 36. For example, the optical filter 42 is implemented as an interference filter.

[0063] In Figure 4 the embodiment shown, for each of the channels 44 shown, the pixels 38 are provided with the same geometry, each geometry being square. In Figure 5 the alternative embodiment shown, the top view shows various shapes and sizes of the individual channels 44 or pixels 38. Specifically, under preferred boundary conditions, at least three compensation pixels 38c (which are distributed in the x and y directions of the array 36) should be provided to adequately describe the geometric aspects and variations of the array. The dimensions, symmetries and numbers of the channels 44 can be freely selected within the scope of the present invention. In addition, any combination of opposing channels 44 with the same spectral filter characteristics as in the prior art can be provided. As mentioned above, the corner pixels or compensation pixels 38c may not be provided with a filter or may use a specific bandpass filter 42.

[0064] In yet another preferred embodiment, as Figure 6 shown in the top view of, at least one of the second type of pixels 38c or compensation pixels 38c is located in the central region 62 of the array 36 of sensor pixels 38. This central compensation pixel 38c can be used to analyze the diffuse distribution and dominant angle of the incident light source.

[0065] In the illustrated embodiment, the transmission characteristics of the sensor pixels 38s are linearly independent and can be considered as channels 44 of the detector unit 10. With linearly independent transmission characteristics, only light having a specific wavelength is attributed to a certain channel 44 or spectral pixel 38s. In Figure 4 In the illustrated preferred embodiment, the detection unit 10 is intended for use in the ambient light sensor 4 and is thus equipped with 12 sensor pixels 38s, corresponding to 12 sensor channels 44, such that the number of channels with different transmission characteristics is in a preferred range of approximately 5 to 12. In the illustrated preferred embodiment, taking into account the desired at least approximate reconstruction of the spectrum detected in the visible light range for providing ambient light information, the spectral sensitivity of the channels 44 has a cosine shape, where the full width at half maximum (FWHM) width is approximately equal to the spacing between adjacent peaks. However, in other embodiments, the spectral sensitivity of one or each channel may have a Gaussian shape.

[0066] The spectral sensitivity for spectral analysis can be achieved by the aforementioned array 40 of optical filters 42, for example, based on an appropriate design of interference filters. The filters 42 can be arranged such that each sensor pixel 38s has its respective spectral sensitivity. By appropriately combining the channels 44, a spectral response distribution (or spectrum) for measuring the characteristics of the sample can be generated. This can be analyzed by an algorithmic reconstruction method.

[0067] The foregoing concept allows for the construction of a multispectral sensor 1 based on an array 36 composed of sensor pixels 38s. Each sensor pixel 38s has known spectral characteristics. All sensor pixels 38s are linearly independent. For example, each sensor pixel 38s is sensitive to narrowband light. The narrowband can be UV, VIS, NIR, and / or IR. The spectral information characteristics of the light source can be reconstructed. The optical sensor 1 can be complemented with optics to determine the field of view (FOV) of the multispectral sensor 1, for example, for restricting the observation area on the target. The optics can be a microlens array arranged close to the sensor array 36 and / or an independent lens for optically imaging the target area on the optical sensor. In fact, the positions of the sensor pixels 38s can be arranged to detect only a specific range on the target.

[0068] Compensation pixels 38c can be distributed on the optical sensor 16, for example, in the corners 60 of the array 36, and can define the extent of the observed target area. The compensation signals generated by these pixels 38c can be used to evaluate the effect of non-uniform radiation. In order to recalculate the information on the target characteristics or the radiation distribution of the radiation source, it is recommended that the compensation pixels 38c have the same spectral sensitivity so that spectral differences are not misinterpreted. The compensation pixels 38c can be configured to not have filters or to have the same filters to enhance independence. The filters of the compensation pixels 38c can also be part of the spectral measurement.

[0069] The compensation signal and its deviation can be used as parameters to describe the non-uniform radiation incident on the optical sensor 10. By understanding the optical effects of other parts, a radiation gradient model can be generated, so as to compensate the signal amplitude of each sensor pixel according to the position of each sensor pixel 38s. The result of this compensation may lead to a more robust reconstruction of the spectral radiation characteristics.

[0070] Generally, this compensation can be based on the conventional compensation method for the spectral sensitivities of each sensor under ideal diffuse illumination conditions. Specifically, the following steps can be selected:

[0071] Initial operation / calibration:

[0072] Obtain typical compensation pixel data (C_typ) from ideal diffuse illumination conditions. This data also contains some information on package alignment.

[0073] Application, measurement:

[0074] Obtain compensation pixel data (C_app) under application conditions.

[0075] Application, compensation

[0076] Calculate the ratio to the typical value and scale each to the average value C_ratio = (C_app / C_app_mean) / (C_typ / C_typ_mean)

[0077] Calculate the ratio related to the pixel by position interpolation: P_ratio = interpolate(C_position, C_ratio, P_position)

[0078] Calculate the compensated pixel value: P_comp = P_app * P_ratio

[0079] The spectral shift caused by the angular change can be compensated separately by a look-up table or a prediction algorithm. Under higher requirements, a new transfer matrix can also be recalculated.

[0080] Embodiments of the optical sensor device 1 discussed in the present invention have been disclosed to familiarize the reader with the novel aspects of the idea. Although the preferred embodiments have been shown and described, those skilled in the art can make many variations, modifications, equivalents, and alternatives to the disclosed concepts without departing from the scope of the claims.

[0081] Specifically, the present disclosure is not limited to the disclosed embodiments, and examples of as many alternatives as possible for the features included in the discussed embodiments are given. However, any modifications, equivalents, and alternatives to the disclosed concepts are intended to be included within the scope of the appended claims.

[0082] Features recited in separate dependent claims may be advantageously combined. In addition, the reference signs used in the claims are not limited to being construed as limiting the scope of the claims.

[0083] In addition, as used in the present invention, the term "comprising" does not exclude the inclusion of other elements. Further, as used in the present invention, the article "a" is intended to include one or more components or elements and is not limited to denoting only one.

[0084] Unless otherwise expressly stated, no method described in the present invention is ever to be construed as requiring that its steps be performed in a specific order. Accordingly, no specific order is ever to be inferred where the method claims do not recite the order in which its steps are to be followed or where no specific statement in the claims or specification restricts the steps to a specific order.

[0085] List of reference signs

[0086] 1 Camera system

[0087] 2 Camera detection system

[0088] 4 Ambient light sensor

[0089] 6 Cover glass

[0090] 10 Optical detector unit

[0091] 12 Housing

[0092] 14 Chamber

[0093] 16 Sensor unit

[0094] 18 Hole

[0095] 20 IR cut-off filter

[0096] 22 Diffuser

[0097] 24, 26 Cone

[0098] 28 Radiation pattern

[0099] 30 Substrate

[0100] 32 Cover

[0101] 34 Sensor chip

[0102] 36 Array

[0103] 38 Pixel

[0104] 38c Compensation pixel

[0105] 38s Sensor pixel

[0106] 40 Array

[0107] 42 Optical filter

[0108] 44 Channel

[0109] 50 Control unit

[0110] 52 Measuring unit

[0111] 60 Corner

[0112] 62 Central region.

Claims

1. An optical detector unit (10) comprising: - An optical sensor (16) disposed in a chamber (14) having a hole (18) within a housing (12), the optical sensor (16) being arranged to detect received photons passing through the hole (18), and - A diffuser (22) disposed on top of the hole (18) in the housing (12); Wherein: - The optical sensor (16) includes an array (36) of sensor pixels (38s) of a first type and pixels (38c) of a second type, - Each of the pixels (38s) of the first type has different spectral transmission characteristics and each generates a multi-spectral sensor signal respectively, and - The pixels (38c) of the second type have the same transmission characteristics and each generates a compensation sensor signal, And wherein the compensation sensor signal generated by the pixels (38c) of the second type is provided for generating compensation parameters for each of the sensor pixels (38s).

2. The optical detector unit (10) according to claim 1, further comprising a measurement unit (52) configured to provide a sensor signal generated by the optical sensor (16), wherein, The measurement unit (52) is arranged to calculate the compensation parameters for each of the sensor pixels (38s) and modify the multi-spectral sensor signal generated by each of the pixels (38s) of the first type with the compensation parameters calculated for the corresponding pixels (38s) to obtain a compensated multi-spectral sensor signal for each of the pixels (38s) of the first type.

3. The optical detector unit (10) according to claim 1 or 2, wherein, The different transmission characteristics of the pixels (38s) of the first type are linearly independent.

4. The optical detector unit (10) according to any one of claims 1 to 3, wherein, At least each of the pixels (38s) of the first type includes a photodiode and a filter (42), wherein the filter (42) determines the transmission characteristics of the corresponding sensor pixel (38s).

5. The optical detector unit (10) according to any one of claims 1 to 4, wherein, At least three of the pixels (38c) of the second type are provided.

6. The optical detector unit (10) according to any one of claims 1 to 5, wherein, At least some of the pixels (38c) of the second type are located at corners (60) of the array (36) of the sensor pixels (38).

7. The optical detector unit (10) according to any one of claims 1 to 6, wherein, At least one of the pixels (38c) of the second type is located in a central region (62) of the array (36) of the sensor pixels (38).

8. A multi-spectral sensor comprising the optical detector unit (10) according to any one of claims 1 to 7.

9. The multispectral sensor according to claim 8, wherein, The multi-spectral sensor is designed as an ambient light sensor.

10. A method for multi-spectral light sensing, comprising the steps of: - Detecting received photons passing through a diffuser (22) disposed on top of a housing (12) and through a hole (18) of a chamber (14) by means of an optical sensor (16) disposed in the chamber (14) of the housing (12), Wherein the optical sensor (16) includes an array (36) of sensor pixels (38s) of a first type and pixels (38c) of a second type, - Generating a multi-spectral sensor signal for each of the pixels (38s) of the first type, - Generating a compensation sensor signal for each of the pixels (38c) of the second type, and - Calculating compensation parameters for each of the sensor pixels (38s) from the compensation sensor signals generated by the pixels (38c) of the second type.

11. The method according to claim 10 further comprises the following steps: - modifying the multi-spectral sensor signals generated by each of the pixels (38s) with the compensation parameters calculated for the respective pixels (38s), and - providing the modified multi-spectral sensor signals as output signals of the optical detector unit (10).

12. A method of using the method according to claim 10 or 11 in an application for ambient light sensing, preferably in a camera application.

13. A camera system (1) comprising an ambient light sensor (4) having an optical detector unit (10) according to any one of claims 1 to 9.

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