A light detection unit, a UV index sensor, and a method for multispectral light sensing, particularly for UV index determination.

Abstract

In a photodetector unit (10) including a photosensor (16) disposed within a chamber (14) containing an aperture (18) within a housing (12), the photosensor (16) is arranged to detect photons received through the aperture (18), and the photosensor (16) comprises a plurality of sensor channels (44), each channel (44) comprising a sensor pixel (38) and an optical filter (42) associated with the sensor pixel (38), which would be made possible for UV index determination with improved accuracy and data reliability. According to the present invention, this is achieved by designing at least two, preferably three in a preferred embodiment, of the channels (44) as UVI measurement channels (44), each UVI measurement channel (44) having a spectral responsiveness with a peak wavelength between 280 nm and 370 nm.

Description

Technical Field

[0001] The present invention relates to an optical detection unit. More particularly, the present invention relates to an optical detection unit including an optical sensor disposed within a chamber including an aperture within a housing, the optical sensor being arranged to detect photons received via the aperture, the optical sensor comprising a plurality of sensor channels, each channel comprising a sensor pixel and an optical filter associated with the sensor pixel. The present invention further relates to a sensor for measuring a UV index comprising such an optical detection unit, and a method for multispectral light sensing.

Background Art

[0002] Optical sensors are increasingly being used in a variety of technical fields such as smartphones and mobile devices, smart homes and smart buildings, industrial automation, medical technology and connected vehicles. As sensor data and performance improve, more and more applications and individualized solutions become possible, thereby improving the comfort and functionality of mobile devices such as smartphones. Currently, chip-scale color and spectral light sensing has various applications in color discrimination, data authentication, spectroscopy and other industrial and consumer-level optical detection applications.

[0003] One potential future application of significant interest might be the possibility of measuring the UV index within mobile devices. The ultraviolet index, or UV index, is an internationally standardized measurement of the intensity of ultraviolet (UV) radiation that causes sunburn at a given location and time. Currently, it is primarily used for daily and hourly forecasts targeting the general public. The UV index is designed as an open-ended linear scale that is directly proportional to the intensity of UV radiation and adjusts wavelengths based on what causes sunburn on human skin. The purpose of the UV index is to help people effectively protect themselves from UV radiation, which has moderate health benefits but, in excess, causes sunburn, skin aging, DNA damage, skin cancer, immunosuppression, and eye damage such as cataracts. Therefore, it may be highly desirable for mobile devices, such as cell phones, to be able to provide users with real-time spot information on the current UV index.

[0004] Given the widespread use of optical sensors in mobile devices, there is a growing interest in extending their capabilities to include information about the UV component within the detected spectrum. For example, International Publication No. 2021 / 130155 discloses an integrated UV radiation sensor that provides a relatively simple single detector with spectral responsiveness of a type of relatively narrow band-filtering in the UV region, in addition to existing sensor arrays. However, these solutions have limited accuracy and, due to the use of interference filters, are highly susceptible to filter (inter-device) performance and process variations. Because there is only one detection channel, the only possible calibration is scaling, and the lack of correlation with the UV index limits their ability to estimate the UV effects on human skin. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2021 / 130155 Brochure [Overview of the project] [Problems that the invention aims to solve]

[0006] Therefore, an object of the present invention is to provide an improved photodetector of the type identified above that overcomes the defects identified above and helps provide user-friendly data that may be used directly to evaluate risk factors due to the effects of incident UV radiation. Furthermore, an improved sensor for direct use, particularly as a UV index sensor, and an improved method for multispectral light sensing should be provided.

[0007] With respect to the photodetector unit, this objective is achieved by the photosensor of the detection unit comprising a plurality of sensor channels, each channel comprising a sensor pixel and an optical filter associated with the sensor pixel, wherein at least two of the channels are designed as UVI measurement channels, and each UVI measurement channel has a spectral response with a peak wavelength between 280 nm and 370 nm.

[0008] A preferred embodiment is the subject of a dependent claim.

[0009] This invention is based on the consideration that, in order to overcome the potential shortcomings and limited capabilities of existing systems, the true effects of incident UV radiation on human skin and the risks caused thereby should be considered by relating the evaluation of data more systematically than before to the characteristics of the UV index. In particular, it should be taken into consideration that the UV index is a number that is linearly related to the intensity of incident UV radiation that causes sunburn. However, for proper risk assessment, the UV of most concern occupies the wavelength spectrum from 295 nm to 325 nm, and shorter wavelengths are already largely absorbed by the time they reach the Earth's surface, so it should not be simply related to irradiance. However, skin damage from sunburn is wavelength-related, with shorter wavelengths resulting in greater damage. Therefore, the UV intensity spectrum for determining the UV index is multiplied by the so-called erythematous spectrum. This result is integrated over the entire spectrum to give a weighted UV irradiance value or erythematous dose rate in order to obtain an appropriate UV index. According to one aspect of this invention, in order to obtain a useful sensor-based approximation of this risk exposure, it is necessary to consider the spectral distribution of this skin sensitivity represented by the erythematous spectrum. [Means for solving the problem]

[0010] To achieve this, in one aspect of the present invention, the detection unit comprises at least two dedicated channels used to determine parameters approximating the UV index, which are hereby referred to as "UVI measurement channels." Considering the characteristics of the erythema spectrum combined with a typical incident light spectrum, according to one aspect of the present invention, each of these UVI measurement channels should have a spectral responsiveness with peak values ​​in the relevant range between 280 nm and 370 nm. By providing at least two of these UVI measurement channels, the detection unit can compensate, at least to some extent, for spectral effects associated with UVI values.

[0011] In a preferred embodiment, according to one aspect of the present invention, the engineering design of the spectral characteristics of each channel takes into account that, for incident radiation, the most relevant transmission variations to its original solarized spectrum originate from Rayleigh scattering and ozone absorption. Both have different absorption spectral shapes that define the final effective spectrum and UVI number. Therefore, preferably, spectral variations in the range of 280 nm to 340 nm should be measured multispectrally to distinguish different absorption effects or to reconstruct the final effective spectrum, and thus the UVI measurement channel should have peak responsiveness in this range.

[0012] In particular, according to one aspect of the present invention, a spectral reconstruction technique is used for a sensor signal generated by a UVI measurement channel to approximate the UV index, preferably using a well-defined shape for at least two, preferably three or potentially four spectral channels of the peak wavelength, FWHM, and the aforementioned wavelength range, along with knowledge of the actual spectral characteristics and a procedure for reconstructing the surface spectrum based on this defined individual transfer matrix.

[0013] According to one aspect of the present invention, the photosensor further comprises a third sensor channel designed as one of the UVI measurement channels, which also has spectral responsiveness with a peak wavelength between 280 nm and 370 nm. As described above, the product of the expected weighted spectral function for approximating the UV index, i.e., the expected spectrum of the incident radiation including the erythemal spectrum, is a curved spectral function, rendering linear extrapolation from the visible spectrum measurement to the UV spectrum to a limited value. Therefore, providing exactly three UVI measurement channels of the type defined above is particularly beneficial and is considered independently inventive. Rather, by providing three sets of sensor data, at least a rough approximation of the curved spectrum becomes possible. On the other hand, of course, more than three UVI measurement channels may be provided, but it has been found that their additional contribution to sensor accuracy is of limited value at a significant additional cost. Therefore, from the viewpoint of cost-benefit ratio, according to one aspect of the present invention, it is preferable to provide exactly three UVI measurement channels.

[0014] In a preferred embodiment, each UVI measurement channel has a spectral response where the FWHM is between 10 nm and 30 nm.

[0015] In another aspect of the present invention, which is considered independently inventive, the spectral responsiveness of the UVI measurement channels is designed to allow data evaluation within a particularly high significance range. According to this aspect of the present invention, the first UVI measurement channel has a spectral responsiveness with a peak wavelength of approximately 290 nm, and the second UVI measurement channel has a spectral responsiveness with a peak wavelength of approximately 320 nm. This aspect of the present invention takes into consideration that, in particular, the characteristics of the expected weighted influence spectrum are most important at these wavelengths, thereby providing the most useful information regarding UV influences. With such selected design peak wavelengths, even two UVI measurement channels may be sufficient to provide important signals.

[0016] In yet another independent inventive aspect of the present invention, at least three UVI measurement channels are provided, wherein a first UVI measurement channel has a spectral response with a peak wavelength of about 290 nm, a second UVI measurement channel has a spectral response with a peak wavelength of about 305 nm, and a third UVI measurement channel preferably has a spectral response with a peak wavelength of about 340 nm.

[0017] According to a preferred embodiment of the present invention, each channel pixel comprises a photodiode and a filter, the filter determining the transmission characteristics of each sensor pixel.

[0018] For proper evaluation of the individual output signals provided by the UVI measurement channels, recalibration or rescaling may be required or recommended to compensate for different individual sensitivities. In a manner comparable to a similar multi-channel system, according to one aspect of the present invention, this may be achieved by a standard calibration procedure in which the individual responsiveness of all channels may be measured under standard and equal conditions, and the results are used for subsequent rescaling and compensation. This correction of the channel signals may be performed within an external control unit or within an integrated component of the detection unit or the sensor itself. In this embodiment of the present invention, the detection unit further comprises an evaluation unit configured to provide characteristics of the output sensor signal and UV index generated by the photosensor, the output signal being calculated from individual output signals from each of the UVI measurement channels.

[0019] With respect to multispectral sensors, the above-mentioned objective is achieved in that the multispectral sensor comprises the type of photodetector unit specified above. In another aspect of the present invention, the multispectral sensor is designed to be a UV index sensor and intended to be used as is.

[0020] Regarding a method for multispectral light sensing, according to one aspect of the present invention, the object specified above is - Detecting photons received through an aperture of the chamber by an optical sensor disposed within a chamber of the housing, where the optical sensor comprises a plurality of sensor channels, each channel comprising a sensor pixel and an optical filter associated with the sensor pixel, at least two of the channels being designed as UVI measurement channels, each UVI measurement channel having a spectral responsiveness with a peak wavelength between 280 nm and 370 nm; - Generating a UVI measurement channel signal for each UVI measurement channel; - Generating an output sensor signal of the optical sensor and characteristics of the UV index from the UVI measurement channel signal of each of the UVI measurement channels are used to achieve.

[0021] Preferably, the method further comprises performing spectral reconstruction of the UVI measurement channel signal by a relevant calibration vector or correction values individually assigned to each of the UVI measurement channels before an output sensor signal of the optical sensor indicating characteristics of the UV index is generated.

[0022] In one aspect of the present invention, the concepts defined above are used for applications for UV index determination, preferably for mobile devices.

[0023] In a further aspect of the present invention, a mobile device, particularly a smartphone, comprising a UV index sensor having an optical detection unit of the type specified above is envisaged.

[0024] The main advantages achieved by the present invention are that by providing at least two, preferably three dedicated UVI measurement channels, the real-time spot index value of the UV index may be provided with much higher accuracy and reliability than conventional systems, so that users can receive improved information regarding current risk factors due to the effects of incident UV radiation. By incorporating a sensor based on this concept into a mobile device, particularly a smartphone, a portable solution for managing the risk of a user's UV exposure may be provided.

[0025] Brief Description of the Preferred Embodiments Preferred embodiments and aspects of the present invention are further described in relation to the drawings.

Brief Description of the Drawings

[0026] [Figure 1] It is a diagram showing a part of a mobile device, particularly a smartphone. [Figure 2] It is a cross-sectional view of the light detection unit of the mobile device of FIG. 1. [Figure 3] It is a diagram showing several graphs for determining the UV index. [Figure 4a] It is a diagram showing several graphs showing the influence of scattering on the solar spectrum. [Figure 4b] It is a diagram showing several graphs showing the influence of scattering on the solar spectrum. [Figure 5] It is a diagram showing several graphs representing the relative spectral responsivity of the UVI measurement channels of the detection unit of FIG. 2.

Modes for Carrying Out the Invention

[0027] The same parts are denoted by the same reference numerals.

[0028] Figure 1 shows a cross-sectional view of a portion of mobile device 1 in an embodiment in which a smartphone is shown. Mobile device 1 includes a UV index sensor 2 as part of an integrated system that provides the user with any kind of appropriate information regarding the current UV index status, as a result of pursuing superior functionality and versatility among other typical and conventional features and applications. The type of information provided to the user within this function may include an approximate value of the current UV index determined by the system, and / or risk factors indicating the user's risk of skin damage, sunburn, etc., and / or general warning messages including recommendations to the user, such as not exposing skin to avoid increased risk of sunburn at the moment.

[0029] For this purpose, the UV index sensor 2 is mounted on the back of the cover glass 6, which may be the cover glass 6 of the smartphone 1, along with potentially various other components. The UV index sensor 2 comprises a photodetector unit 10 in the form and design of a photosensor chip. It should be noted that the concepts proposed herein can be applied to various types of photosensor chips and optical devices, and the present invention relates only to the design of the photodetector unit 10, and therefore may very well be used in other configurations of the photodetector unit 10 within the scope of the present invention. In particular, it should be noted that in the illustrated embodiment, the photodetector unit 10 is designed as a separate, independent sensor component, but in alternative embodiments, within the scope of the present invention, existing conventional sensor chips may also have their functionality extended to include the ability to provide UV index measurements by adding individual technical features or components according to the concepts described below.

[0030] The photodetection unit 10 of the UV index sensor 2 shown in Figure 2 comprises a housing 12 that includes a sensor chamber 14 in which the actual UV index sensor unit 16 is positioned. The housing 12 is provided with an opening or aperture 18 to allow proper passage of light or radiation to reach the sensor unit 16 through the housing 12. The aperture 18 may be covered by a VIS and NIR cut filter 20, which may be covered by a diffuser 22 depending on the precise positioning and design of the components. In the illustrated embodiment, the diffuser 22 is positioned directly adjacent to the cover glass 6.

[0031] As shown in Figure 2, the housing 12 of the detection unit 10 is placed on a substrate or carrier 30. A cover portion or lid 32, which also forms part of the aperture 18 and housing 12, is located on the opposite side of the carrier 30 and thereby covers the chamber 14. The carrier or substrate 30 mechanically supports and electrically connects the electronic components to be integrated into the photodetection 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 be part of the housing 12, and the electronic components may be embedded in the housing 12, for example, by molding.

[0032] As part of the photodetection unit 10, the photosensor unit 16 is located inside the chamber 14 and on the carrier 30. In this particular embodiment, the photosensor 16 is integrated with other electronic components into a single semiconductor sensor die 34. The photosensor comprises a configuration 36 of individual photodetectors or pixels 38, which will be described in more detail below. The pixels 38 may be implemented, for example, as photodiodes. As a further part of the photodetection unit 10, a configuration 40 of optical filters 42 is located inside the chamber 14 above the photosensor unit 16. The configuration 40 of optical filters 42 is mounted on the photosensor 16. Each of the pixels 38 is associated with an associated optical filter 42 having different transmission characteristics. Together, the pixels 38 and associated filters 42 form a channel 44 of the photodetection unit 10. The optical filters 42 may be light-blocking filters, band-pass filters, long-pass or short-pass filters, dielectric filters, Fabry-Perot filters and / or polymer filters, and other interference filters. The spectral sensitivity or responsiveness of each channel 44 is achieved by the individual design of each optical filter 42 in combination with their associated pixels 38, for example, based on the appropriate design of the interference filter. The filters 42 can be designed or engineered so that each sensor pixel 38 and each channel 44 has its own spectral sensitivity.

[0033] To allow the proper passage of light or radiation, an aperture 18 is provided in the cover or lid 32 of the housing 12. The aperture 18 is positioned above the light sensor 16. In fact, the aperture 18 is within the field of view (FOV) of the light sensor 16. The field of view of the light sensor 16 includes, at least theoretically, all points in space over which light emitted from external radiation or a light source may cross toward the light sensor 16, for example, due to the position and orientation of a fixed detector.

[0034] In the illustrated embodiment, the control unit 50 and the measurement unit 52 are integrated with the optical sensor 16 on the semiconductor sensor die 34. The measurement unit 52 can be considered the control unit of the optical detection unit 10. For example, the measurement unit 52 provides the sensor signal generated by the optical sensor 16. The control unit 50 and the measurement unit 52 may be implemented as control logic, a state machine, a microprocessor, etc. They may also include additional components such as analog-to-digital converters, time-to-digital converters, and amplifiers located within the semiconductor sensor die 34. The semiconductor die 34 may have a printed circuit board (PCB) that provides electrical connections to the individual components of the multispectral sensor. However, in alternative embodiments, it is understood that some or all of the functions provided by the control unit 50 and / or the measurement unit 52 may be performed in other control units or control logic outside the detection unit 10.

[0035] The detection unit 10 is designed and engineered to allow the UV index sensor 2 to provide the parameter characteristics of the so-called UV index, in particular the type of characteristic information identified above, especially quantitative values ​​of the current UV index and / or messages or other parameters derived therefrom, for further processing. With this design objective in mind, the detection unit 10 is designed to gather information of specific relevance for determining the UV index. For further explanation of the background considerations, Figure 3 shows several graphs illustrating the relevant background information for UV index determination.

[0036] In Figure 3, Graph 60 shows irradiation by the solar spectrum as a function of wavelength on a logarithmic scale. Graph 62 is the so-called erythematous spectrum as a function of wavelength on a normal scale, and generally speaking, it shows the intensity of the human skin response to UV irradiation exposure. Graph 64 is the result of multiplying Graphs 60 and 62, showing the relevant effective spectrum on a logarithmic scale for assessing the risk of damaging human skin as a result of irradiation by the solar spectrum. This effective spectrum, represented by Graph 64 and commonly used in public services, is, for example, the basis for calculating the UV index. As is evident from Figure 3, the major and almost significant contribution from the effective spectrum represented by Graph 64 is in the wavelength range of approximately 290 nm to 370 nm.

[0037] However, in real-world situations, whether the solar spectrum efficiently reaches human skin or, similarly, the detection unit 10 may be due to variations in ambient conditions. The main sources of variation in the solar spectrum can be seen in the effects of Rayleigh scattering and ozone absorption in the atmosphere, both of which reduce the transmittance of lower wavelengths. Figure 4 is a set of graphs showing several graphs 60' representing the solar spectrum under various scattering conditions (Figure 4a) on a logarithmic scale, multiplied by the erythema effect spectrum, and showing several graphs 64' representing the effective exposure spectrum under the same various scattering conditions. Clearly, as can be seen from these graphs 64', variations in ambient conditions can have a significant impact on the accurate calculation of the UV index. Within the scope of the present invention, these effects of scattering on the incident light spectrum are considered one of the main causes of the insufficient performance of conventional UV index sensors.

[0038] To overcome these shortcomings of conventional UV index sensors, the photodetection unit 10 of the UV index sensor 2 shown in Figure 2 is designed to compensate for the potential effects of such fluctuations. To achieve this, according to one aspect of the present invention, in at least two, more precisely three, preferred separate embodiments of the present invention are shown, where channel 44 is designed as a dedicated channel 44, i.e., a UVI measurement channel 44. In one aspect of the present invention, each such UVI measurement channel 44 should be understood to be characterized by a spectral responsiveness with a peak wavelength between 280 nm and 370 nm.

[0039] Furthermore, in the illustrated embodiment, each UVI measurement channel 44 has a spectral response where the FWHM is between 10 nm and 30 nm.

[0040] Figure 5 shows a graph 66 representing the sensitivity or responsiveness of the relative spectra of the three UVI measurement channels 44 of the photodetector unit 10. As shown in the figure, the first UVI measurement channel of the UVI measurement channel 44 has a spectral responsiveness with a peak wavelength of approximately 290 nm, the second UVI measurement channel of the UVI measurement channel 44 has a spectral responsiveness with a peak wavelength of approximately 305 nm, and the third UVI measurement channel of the UVI measurement channel 44 has a spectral responsiveness with a peak wavelength of approximately 340 nm.

[0041] Since the individual responsiveness of channel 44 may vary due to manufacturing process variations, etc., appropriate correction to the individual sensor output may be necessary or desirable in order to assign appropriate weights to each channel 44 when calculating an approximate value of the UV index. Accordingly, the integrated evaluation or measurement unit 52 may be configured to provide the output sensor signal and UV index characteristics generated by the photosensor 16, which is calculated from the individual output signals from each of the UVI measurement channels 44, each potentially corrected by appropriate weighting coefficients obtained from previous calibration measurements of the individual channels 44.

[0042] In preferred embodiments, the Gaussian shape of the filter 42 (FWHM 10...30 nm), or preferably the responsiveness of the complete UVI measurement channel 44, is provided in particular to obtain a reliable sensor signal independent of potential spectral noise. In the preferred embodiment shown in Figure 5, a channel 44 with an FWHM of 20 nm is provided.

[0043] As described above, according to one aspect of the present invention, a system with only two UVI measurement channels 44 may be selected, particularly in favor of a simple configuration. In all embodiments, a preferred channel peak wavelength in the range of 290 nm to 340 nm is selected. While a configuration with two UVI measurement channels 44 is beneficial for compensating for offset and slope, it may not be beneficial for modifying convex strain. Therefore, three or more UVI measurement channels 44 are preferred.

[0044] The UVI measurement channels 44 in the selected wavelength range may be distributed in an optimized design with peak wavelengths of approximately 290 nm, 305 nm, and 340 nm, respectively, to obtain superior performance from this reconstructed spectrum in reconstruction and ultimately UVI calculations. Furthermore, while more than three UVI measurement channels are considered to be within the scope of the present invention, they are not expected to significantly improve the accuracy of the system.

[0045] The sensor unit 16 designed according to the present invention may be provided in an integrated multispectral detection device (CMOS and / or upper interference filter). In general, the design and concept of the UV index sensor 2 provides the possibility of particularly high-precision UVI measurement independent of valuable filter process variations, in particular by compensating for spectral filter variations through individual calibration. The compensation parameters may be provided by a memory device within the sensor system or supported by a chip ID via a cloud system. The design concept may further enable high-quality, potentially even complete spectral reconstruction in the effective and relevant spectral range, resulting in high-precision UVI calculations even when considering spectral effects due to ozone absorption and / or Rayleigh scattering. This type of improved measurement concept further enables the calculation of various UV parameters such as vitamin D3 production, DNA skin damage, and eye damage.

[0046] Embodiments of the optical sensor device 1 described herein are disclosed for the purpose of enabling the reader to understand novel aspects of the concept. While preferred embodiments have been shown and described, many changes, modifications, equivalents, and substitutions of the disclosed concept may be made by those skilled in the art without unnecessarily departing from the claims.

[0047] In particular, this disclosure is not limited to the disclosed embodiments, and provides as many examples of alternative embodiments as possible of the features included in the described embodiments. However, any modifications, equivalents, and substitutions of the disclosed concepts are intended to be included within the claims appended herein.

[0048] Features described in separate dependent claims may be advantageously combined. Furthermore, reference numerals used in the claims should not be construed as limiting the scope of the claims.

[0049] Furthermore, as used herein, the term “including” does not exclude other elements. Furthermore, as used herein, the article “a” is intended to include one or more components or elements, and is not limited to being interpreted as meaning only one.

[0050] Unless otherwise specified, no method described herein is ever intended to be construed as requiring its steps to be performed in a specific order. Therefore, if a claim for a method does not actually enumerate the order in which its steps should be performed, or if it is not specifically stated in the claim or description that the steps should be limited to a particular order, no particular order is ever intended to be inferred. [Explanation of Symbols]

[0051] 1 Mobile device 2 UV Index Sensors 6 Cover glass 10. Light detection unit 12 Housing 14 Chambers 16 Sensor Unit 18 Aperture 20 IR cut filters 22 Diffuser 30 circuit boards 32 Lid 34 Sensor Dies 36 components 38 pixels 40 components 42 Light Filters 44 channels 50 control units 52 Measurement Units 60, 62, 64, 60', 64', 66 graph

Claims

1. A photodetector (10) comprising a photosensor (16), wherein the photosensor (16) comprises a plurality of sensor channels (44), each channel (44) comprising a sensor pixel (38) and an optical filter (42) associated with the sensor pixel (38), at least two of the channels (44) are designed as UVI measurement channels (44), and each UVI measurement channel (44) has a spectral response with a peak wavelength between 280 nm and 370 nm.

2. The photodetector unit (10) according to claim 1, wherein the photosensor (16) comprises a third sensor channel (44) designed as a UVI measurement channel (44) having a spectral response with a peak wavelength between 280 nm and 370 nm.

3. The photodetector unit (10) according to claim 1 or 2, wherein each of the UVI measurement channels (44) has a spectral response in which the FWHM is between 10 nm and 30 nm.

4. The photodetector unit (10) according to any one of claims 1 to 3, wherein the first UVI measurement channel among the UVI measurement channels (44) has a spectral response with a peak wavelength of approximately 290 nm, and the second UVI measurement channel among the UVI measurement channels (44) has a spectral response with a peak wavelength of approximately 320 nm.

5. The photodetector unit (2) according to claim 4, wherein the third UVI measurement channel among the UVI measurement channels (44) has a spectral response with a peak wavelength of approximately 340 nm.

6. The photodetector unit (10) according to any one of claims 1 to 5 further comprises an evaluation unit (52) configured to provide characteristics of the output sensor signal and the UV index generated by the photodetector (16), wherein the output signal is calculated from individual output signals from each of the UVI measurement channels (44).

7. A multispectral sensor comprising a light detection unit (10) according to any one of claims 1 to 6.

8. A UV index sensor (2) comprising a light detection unit (10) according to any one of claims 1 to 6.

9. A method for multispectral light sensing, - A step of detecting a photon received through the aperture (38) of the chamber (14) by an optical sensor (16) located inside the chamber (14) of the housing (12), The optical sensor (16) comprises a plurality of sensor channels (44), each channel (44) comprising a sensor pixel (38) and an optical filter (42) associated with the sensor pixel (38), at least two of the channels (44) are designed as UVI measurement channels (44), and each UVI measurement channel (44) has a spectral response with a peak wavelength between 280 nm and 370 nm, and - A step of generating a UVI measurement channel signal for each UVI measurement channel (44), - A step of generating the output sensor signal of the photosensor (16) and the UV index characteristics from each of the UVI measurement channel signals of the UVI measurement channel (44). Methods that include...

10. The method for multispectral light sensing according to claim 9, further comprising the step of performing spectral reconstruction of the UVI measurement channel signal by a relevant calibration value before the output sensor signal of the photosensor (16) exhibiting the characteristics of the UV index is generated.

11. Use of the method according to claim 9 or 10 for applications in determining the UV index, preferably in applications in mobile devices.

12. A mobile device (1), particularly a smartphone, comprising a UV index sensor (2) having a light detection unit (10) according to any one of claims 1 to 6.

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