WO2024056159A1

WO2024056159A1 - Color filter pattern and module for spectral camera

Info

Publication number: WO2024056159A1
Application number: PCT/EP2022/075417
Authority: WO
Inventors: Lei Jiang; Samu Koskinen; Mikko Perala; Huihui Wang
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-09-13
Filing date: 2022-09-13
Publication date: 2024-03-21
Anticipated expiration: 2025-03-13

Abstract

A multispectral filter array (1) comprising a plurality of identical mosaic elements (2) arranged in a two-dimensional pattern, each mosaic element having a plurality of visible filter elements (3), UV filter elements (4) and at NIR filter elements (5) arranged to transmit spectral energy through a corresponding filter channel. A multispectral imaging system is also provided where the multispectral filter array (1) is arranged on an image sensor (14) in at least two separate filter areas (8, 10) with dedicated types of filter elements, each filter area covered by a corresponding image lens (16, 17) adapted to the wavelength range of the light spectrum transmitted by the filter elements arranged in the corresponding filter area.

Description

COLOR FILTER PATTERN AND MODULE FOR SPECTRAL CAMERA

TECHNICAL FIELD

The disclosure relates to digital image sensors, in particular a multispectral filter array for an image sensor and a multispectral imaging system comprising an image sensor and a multispectral filter array.

BACKGROUND

Typical image sensors like the ones we use in digital cameras are comprised of many individual photosensors, all of which capture light. These photosensors are natively able to capture the intensity of light but not its wavelength (color). As a result, image sensors are typically overlaid with a "color filter array" or a "color filter mosaic." This overlay consists of many tiny filters that cover the known pixels and allow them to render color information.

A digital image processor can decode the color of an area by essentially averaging the color data from the various interpolated color filters and the relative brightness registered by the pixels. One of the most common filter arrangements at work in modern devices is called the Bayer filter. This arrangement uses a proportion of two green filter elements (G) for each red (R) and blue (B) filter element. The entire array is spread over a 2x2 block of pixels (mosaic elements), and each microfilter covers one-quarter of a pixel. Such a Bayer filter mosaic is also called a color filter array (CFA) and is used for arranging RGB color filters on a square grid of photosensors. Its particular arrangement of color filters is used in most single-chip digital image sensors used in digital cameras, camcorders, and scanners to create a color image. Once recorded, digital algorithms are applied to interpolate or "demosaic" the resulting Bayer pattern and turn it into full-fledged color data for the image.

Multispectral imaging captures image data within specific wavelength ranges across the electromagnetic spectrum. The wavelengths may be separated by filters that are sensitive to particular wavelengths, including light from frequencies beyond the visible light range, i.e. infrared (IR) and ultra-violet (UV). Multispectral imaging can thus allow extraction of additional information the human eye fails to capture with its visible receptors for red, green and blue.

Thanks to some technical progress in interferencefilter design based on different technologies, it became possible to successfully implement the concept of multispectral filter array based sensors in mobile devices. Based on recent studies, spectral cameras could potentially provide new solutions and enhanced user experiences to customers when integrated in mobile devices such as smartphones with integrated cameras.

Some use cases, such as security features using Face ID, or health features like face skin health detection need high resolution and wide spectral range. In the case of Face ID, the applications need higher than VGA resolution for proper identification, and better wavelength coverage in the near-infrared spectrum for recognizing user-specific facial features. In the case of face skin health detection, the camera also needs high resolution and coverage in the UV channel in order to get more details for an accurate skin health analysis.

In order to solve these issues using smartphone cameras, some manufacturers introduced spectral sensors. In the conventional design such spectral sensors include several (typically 16) channels in the visible area and 1 NIR (near-infrared) channel.

However, one issue with the current spectral sensor solutions is that they only offer single point detection, which means they cannot support the cases of complex light sources. There is therefore also a need for a multi-point spectral sensor solution at least for executing local Auto White Balance (AWB) in such complex lighting conditions.

There is thus a need for spectral camera sensing systems to cover the whole spectral range from UV and NIR while providing high resolutions in both the UV and NIR channels to achieve accurate Face ID and to provide sufficient and reliable support for camera-based health analysis.

SUMMARY

It is an object to provide an improved multispectral filter array for an image sensor and a multispectral imaging system which overcomes or at least reduces the problems mentioned above.

The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

According to a first aspect, there is provided a multispectral filter array for an image sensor comprising a plurality of identical mosaic elements arranged in a two-dimensional pattern, with a plurality of visible filter elements, at least one UV filter element and at least one NIR filter element arranged in each mosaic element to transmit spectral energy through a corresponding filter channel.

Such a multispectral filter array arrangement enables covering the whole spectral range from UV to NIR through the whole visible light spectrum, while also providing high resolutions in both the UV and NIR channels to achieve accurate Face ID and to provide sufficient and reliable support for camera-based health analysis.

In a possible implementation form of the first aspect each mosaic element comprises a plurality of visible filter elements, a plurality of UV filter elements, and a plurality of NIR filter elements allowing for better coverage and higher resolutions in the UV and NIR spectral ranges.

In a further possible implementation form of the first aspect at least one of the UV filter channel(s) or the NIR filter channel(s) have higher resolution than the visible filter channels, which provides a better balancing of data for image processing.

In a further possible implementation form of the first aspect each of the plurality of visible filter elements is configured to transmit spectral energy in a different band of the visible light spectrum, through a corresponding one of a plurality of visible filter channels, each of the plurality of UV filter elements is configured to transmit spectral energy in the same ultraviolet range of the invisible light spectrum, through a single UV filter channel, and each of the plurality of NIR filter elements is configured to transmit spectral energy in the same near-infrared range of the invisible light spectrum, through a single NIR filter channel. This enables better resolutions and provides a better balancing of image data for further image processing.

In a further possible implementation form of the first aspect each mosaic element comprises 16 filter elements arranged in a 4x4 matrix, which pattern is advantageous for image processing algorithms.

In a further possible implementation form of the first aspect each mosaic element comprises 12 visible filter elements corresponding to 12 different visible filter channels; 2 UV filter elements corresponding to a single UV filter channel; and 2 NIR filter elements corresponding to a single NIR filter channel; wherein the filter elements in each mosaic element are arranged so that adjacent filter elements correspond to different filter channels, which allows dedicated channel numbers balancing based on application requirements. In a further possible implementation form of the first aspect each mosaic element is divided into a first mosaic area comprising 6 visible filter elements, 1 UV filter element, and 1 NIR filter element; and a second mosaic area comprising 6 visible filter elements, 1 UV filter element, and 1 NIR filter element, allowing for better coverage and higher resolutions in the UV and NIR spectral ranges.

In an embodiment the first mosaic area and the second mosaic area are arranged identically. In another embodiment the first mosaic area and the second mosaic area are arranged in different patterns.

In a further possible implementation form of the first aspect each mosaic element comprises 8 visible filter elements corresponding to 8 different visible filter channels; 4 UV filter elements corresponding to a single UV filter channel; and 4 NIR filter elements corresponding to a single NIR filter channel; wherein the filter elements in each mosaic element are arranged so that adjacent filter elements correspond to different filter channels, thereby enabling to achieve a better spectral camera resolution.

In a further possible implementation form of the first aspect the filter elements in each mosaic element are arranged so that each UV filter element is adjacent to a NIR filter element, thereby enabling to achieve a better spectral camera resolution.

In a further possible implementation form of the first aspect the filter elements in each mosaic element are arranged so that each UV filter element and NIR filter element is only adjacent to visible filter elements, thereby enabling to achieve a better spectral camera resolution.

According to a second aspect, there is provided a multispectral filter array for an image sensor comprising a first filter area with a plurality of identical first mosaic elements arranged in a two- dimensional pattern; and a second filter area with a plurality of identical second mosaic elements arranged in a two-dimensional pattern. Each of the mosaic elements comprise at least one of a plurality of UV filter elements configured to transmit spectral energy in an ultraviolet range of the invisible light spectrum, a plurality of NIR filter elements configured to transmit spectral energy in a near-infrared range of the invisible light spectrum, and a plurality of visible filter elements each configured to transmit spectral energy in a different band of the visible light spectrum.

Providing a multispectral filter array comprising two different filter areas with different filter element patterns carries the aforementioned advantages and further enables the implementation of the multispectral filter array in a smartphone camera configuration with multiple lenses with dedicated wavelengths.

In a possible implementation form of the second aspect each first mosaic element consists of a plurality of UV filter elements and a plurality of NIR filter elements; and each second mosaic element consists of a plurality of visible filter elements. Arranging the UV and NIR filters in one area and the visible filters in a separate area allows for implementation of the multispectral filter array in a smartphone camera configuration with one dedicated lens for the visible spectrum and another dedicated lens for the UV and NIR spectrum.

In a further possible implementation form of the second aspect each first mosaic element consists of 2 UV filter elements and 2 NIR filter elements arranged in a 2x2 matrix; wherein the different filter elements in the first mosaic element are arranged alternatingly so that each UV filter element is only adjacent to NIR filter elements and vice versa. This pattern is advantageous for image processing algorithms.

In an embodiment the UV filter elements correspond to a single UV filter channel, and the NIR filter elements correspond to a single NIR filter channel.

In another embodiment each UV filter element corresponds to a dedicated one of two UV filter channels, and each NIR filter element corresponds to a dedicated one of two NIR filter channels.

In a further possible implementation form of the second aspect each second mosaic element consists of 12 visible filter elements corresponding to 12 different visible filter channels, arranged in a 3x4 matrix. This pattern is advantageous for image processing algorithms.

In a further possible implementation form of the second aspect each second mosaic element is divided into a first mosaic area comprising 6 visible filter elements and a second mosaic area comprising 6 visible filter elements, allowing for better coverage and higher resolutions in the UV and NIR spectral ranges.

In a further possible implementation form of the second aspect each second mosaic element consists of 9 visible filter elements corresponding to 9 different visible filter channels, arranged in a 3x3 matrix. This pattern is advantageous for image processing algorithms. In a further possible implementation form of the second aspect each first mosaic element consists of a plurality of visible filter elements a plurality of UV filter elements and each second mosaic element consists of a plurality of NIR filter elements. This arrangement allows for implementation of the multispectral filter array in a smartphone camera configuration with one dedicated lens for the visible and the UV spectrum and another dedicated lens for the NIR spectrum.

In a further possible implementation form of the second aspect each first mosaic element consists of a plurality of visible filter elements a plurality of NIR filter elements and each second mosaic element consists of a plurality of UV filter elements. This arrangement allows for implementation of the multispectral filter array in a smartphone camera configuration with one dedicated lens for the visible and the NIR spectrum and another dedicated lens for the UV spectrum.

In an embodiment all the NIR/UV filter elements in the second mosaic element correspond to a single NIR/UV filter channel.

In another embodiment the NIR/UV filter elements are distributed to correspond to a dedicated one of two or three NIR/UV filter channels.

In a further possible implementation form of the second aspect each first mosaic element comprises 9 filter elements arranged in a 3x3 matrix. This pattern is advantageous for image processing algorithms.

In a further possible implementation form of the second aspect each first mosaic element comprises 16 filter elements arranged in a 4x4 matrix. This pattern is advantageous for image processing algorithms.

In a further possible implementation form of the second aspect the multispectral filter array further comprises a third filter area arranged between the first filter area and the second filter area, the third filter area consisting of dummy mosaic elements configured not to transmit spectral energy in any light spectrum. This allows for a better separation of filter channels and for better positioning of different lenses over different filter areas.

According to a third aspect, there is provided a multispectral imaging system comprising a multispectral filter array according to any one of the above implementation forms of the first and/or the second aspect, the multispectral filter array being arranged on an image sensor; and at least one image lens arranged to cover the multispectral filter array.

This arrangement of a multispectral imaging system enables the implementation of the multispectral filter array in a smartphone camera configuration with multiple lenses with each adapted to the wavelength range of the light spectrum transmitted by the filter elements arranged in the corresponding filter area.

In an embodiment the image sensor is a CMOS image sensor.

In an embodiment the pixel resolution of the image sensor is 1600 x 1200 px.

In a possible implementation form of the third aspect the multispectral imaging system comprises a multispectral filter array according to any one of the implementation forms of the second aspect with a first filter area and a second filter area. In this implementation form the system comprises a first image lens arranged to cover the first filter area; and a second image lens arranged to cover the second filter area; wherein at least one of the first image lens and the second image lens is adapted to the wavelength range of the light spectrum transmitted by the filter elements arranged in the corresponding filter area. This allows each lens to be designed specifically for the underlying filter area, which enables high quality and resolution of image sensing with the possibility of lenses configured for dedicated processing algorithms.

In a further possible implementation form of the third aspect a filter element of the multispectral filter array corresponds to a single pixel of the image sensor, which is advantageous for an efficient image processing.

In an embodiment the size of a single pixel ranges between 1.6pm ~ 4pm. In a particular embodiment the pixel size is 2pm.

In a further possible implementation form of the third aspect a filter element of the multispectral filter array corresponds to 4 pixels of the image sensor in a 2x2 pixel binning arrangement, which provides for a higher resolution in the corresponding filter ranges.

In an embodiment the size of a pixel in a 2x2 pixel binning ranges between 0.8pm ~ 2.4pm. In a particular embodiment the pixel size is 2pm.

In an embodiment the size of a 4x4 mosaic element is 16pm x 16pm. In an embodiment the size of a 4x3 mosaic element is 16pm x 12pm.

In an embodiment the resolution of each mosaic element is 100 x 100 px.

These and other aspects will be apparent from the embodiment(s) described below.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present disclosure, the aspects, embodiments and implementations will be explained in more detail with reference to the example embodiments shown in the drawings, in which:

Fig. 1 is a schematic top view of a multispectral filter array with a zoomed-in view of a mosaic element in accordance with an example of the embodiments of the disclosure;

Fig. 2 is schematic top view of a mosaic element of a multispectral filter array in accordance with another example of the embodiments of the disclosure;

Fig. 3 is a schematic top view of a multispectral filter array with a zoomed-in view of a mosaic element in accordance with another example of the embodiments of the disclosure;

Fig. 4 is a schematic top view of a multispectral filter array with a zoomed-in view of a mosaic element in accordance with another example of the embodiments of the disclosure;

Fig. 5 is a schematic top view of a multispectral filter array comprising multiple filter areas in accordance with another example of the embodiments of the disclosure;

Fig. 6 is a schematic top view of a multispectral filter array comprising multiple filter areas in accordance with another example of the embodiments of the disclosure;

Fig. 7 is a schematic top view of a multispectral imaging system with a multispectral filter array comprising multiple filter areas in accordance with another example of the embodiments of the disclosure; and

Fig. 8 illustrates a multispectral imaging system with a multispectral filter array comprising multiple filter areas in accordance with another example of the embodiments of the disclosure.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are set forth by way of examples in order to provide a thorough understanding of the relevant disclosure. However, it should be apparent to those skilled in the art that the present disclosure may be practiced without such details. In other instances, well known methods, procedures, systems, components, and/or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present disclosure. Steps and features that are the same or similar to corresponding steps and features previously described or shown throughout the description below are denoted by the same reference numerals for simplicity.

Fig. 1 illustrates a multispectral filter array 1 with a zoomed-in view of a mosaic element 2 in accordance with an embodiment of the disclosure. The filter array 1 is made up of a plurality of identical mosaic elements 2 arranged in a two-dimensional pattern, wherein the expression “pattern” is synonymous to "a repeated design", and is meant to define a repetitive arrangement of the mosaic elements in the filter array along at least one axis of the array.

As shown in Fig. 1 , each mosaic element 2 comprises a plurality of filter elements 3, 4, 5 configured to transmit spectral energy through corresponding filter channels. In particular, each mosaic element 2 comprises a plurality of visible filter elements 3 each configured to transmit spectral energy in a different band of the visible light spectrum (between approx. 400nm - 700nm); at least one UV filter element 4 configured to transmit spectral energy in an ultraviolet range (between approx. 300 - 400nm) of the invisible light spectrum; and at least one NIR filter element 5 configured to transmit spectral energy in a near-infrared range (between approx. 770 - 1100nm) of the invisible light spectrum.

In the embodiments shown in Fig. 1 through 8, each mosaic element 2 comprises a plurality of visible filter elements 3, a plurality of UV filter elements 4, and a plurality of NIR filter elements 5.

In the embodiments shown in Fig. 1 through 4, each visible filter element 3 is configured to transmit spectral energy in a different band of the visible light spectrum, through a corresponding one of a plurality of visible filter channels, i.e. each visible filter element 3 having a dedicated visible filter channel. In the same arrangements, each UV filter element 4 is configured to transmit spectral energy in the same ultraviolet range of the invisible light spectrum, through a single UV filter channel, and similarly, each NIR filter element 5 is configured to transmit spectral energy in the same near-infrared range of the invisible light spectrum through a single NIR filter channel.

This means that in the embodiment shown in Fig. 1 , where each mosaic element 2 comprises 16 filter elements arranged in a 4x4 matrix, there are 12 visible filter elements 3 corresponding to 12 different visible filter channels, 2 UV filter elements 4 corresponding to a single UV filter channel and 2 NIR filter elements 5 corresponding to a single NIR filter channel. In this and further embodiments explained below, the filter elements are arranged in each mosaic element 2 so that adjacent filter elements correspond to different filter channels, thereby enabling to achieve a better spectral camera resolution.

As shown in the example of Fig. 1 , this can be achieved by a pattern shown in the arrangement of mosaic element 2, i.e. by arranging the respective UV filter elements 4 and NIR filter elements 5 above each other, surrounded by 6 visible filter elements 3 in an L-shaped configuration.

As further shown in the example of Fig. 1 , each mosaic element 2 can further be divided into a first mosaic area 6 comprising (as outlined above) 6 visible filter elements 3, 1 UV filter element 4, and 1 NIR filter element 5; and a second mosaic area 7 comprising 6 visible filter elements 3, 1 UV filter element 4, and 1 NIR filter element 5.

In this exemplary embodiment the first mosaic area 6 and the second mosaic area 7 are arranged in different patterns whereby the visible filter elements 3 in the different mosaic areas (V1-V6 and V7-V12) also have different channel settings.

In another possible embodiment (not shown) the first mosaic area 6 and the second mosaic area 7 are arranged identically.

In the arrangement shown in Fig. 1 each filter element of the multispectral filter array 1 corresponds to a single pixel of the image sensor 14. The size of a single pixel may range between 1.6pm ~ 4pm. In a particular embodiment the pixel size is 2pm.

In an embodiment the size of a 4x4 mosaic element is 16pm x 16pm, whereby the size of a 4x3 mosaic element (as shown in Fig. 5 and Fig. 8) is 16pm x 12pm. The resolution of each mosaic element is e.g. 100 x 100 px.

Fig. 2 shows another possible arrangement, wherein each filter element of the multispectral filter array 1 corresponds to 4 pixels of the image sensor 14 in a 2x2 pixel binning arrangement. In this example, the remaining features of the multispectral filter array 1 are similar as described above.

In an embodiment the size of a pixel in a 2x2 pixel binning ranges between 0.8pm ~ 2.4pm. In a particular embodiment the pixel size is 2pm. Fig. 3 and 4 illustrate further possible arrangements for the multispectral filter array 1 wherein each mosaic element 2 comprises 16 filter elements corresponding to 10 filter channels, namely: 8 visible filter elements 3 corresponding to 8 different visible filter channels; 4 UV filter elements 4 corresponding to a single UV filter channel; and 4 NIR filter elements 5 corresponding to a single NIR filter channel. In this arrangement as well, the filter elements in each mosaic element 2 are arranged so that adjacent filter elements correspond to different filter channels.

In the exemplary arrangement shown in Fig. 3, the filter elements in each mosaic element 2 are arranged so that each UV filter element 4 is adjacent to a NIR filter element 5, arranged intermittently with the 8 visible filter elements 3 (V1-V8) that are arranged in pairs.

In another possible arrangement shown in Fig. 4, the filter elements in each mosaic element 2 are arranged so that each UV filter element 4 and NIR filter element 5 is only adjacent to visible filter elements 3, arranged intermittently with the 8 visible filter elements 3 (V1-V8) that are arranged individually between each UV filter element 4 and NIR filter element 5.

Figs. 5 through 8 illustrate another aspect of the disclosure, wherein a multispectral filter array 1 for an image sensor 14 comprises a first filter area 8 and a second filter area 10. The first filter area 8 comprises a plurality of identical first mosaic elements 9 arranged in a two- dimensional pattern; and similarly, the second filter area 10 comprises a plurality of identical second mosaic elements 11 arranged in a two-dimensional pattern.

As illustrated in the figures, each first mosaic element 9 and each second mosaic element 11 comprises either a plurality of UV filter elements 4 configured to transmit spectral energy in an ultraviolet range (between approx. 300 - 400nm) of the invisible light spectrum, a plurality of NIR filter elements 5 configured to transmit spectral energy in a near-infrared range (between approx. 770 - 110Onm) of the invisible light spectrum, and/or a plurality of visible filter elements 3 each configured to transmit spectral energy in a different band of the visible light spectrum (between approx. 400nm - 700nm).

As further shown in Figs. 5 through 8, the multispectral filter array 1 can further comprise a third filter area 12 arranged between the first filter area 8 and the second filter area 10 for better separation of filter channels and for positioning different lenses over different filter areas, as will be explained below. This third filter area 12 consists of dummy mosaic elements 13 configured not to transmit spectral energy in any light spectrum. In the arrangements shown in Figs. 5 and 6, each first mosaic element 9 consists only of UV filter elements 4 and NIR filter elements 5 arranged in a checkered pattern, with 2 UV filter elements 4 and 2 NIR filter elements 5 in a repeating 2x2 matrix so that each UV filter element 4 is only adjacent to NIR filter elements 5 and vice versa; wherein each second mosaic element 11 consists only of visible filter elements 3.

In an embodiment the UV filter elements 4 correspond to a single UV filter channel, and the NIR filter elements 5 correspond to a single NIR filter channel. In another embodiment each UV filter element 4 corresponds to a dedicated one of two UV filter channels, and each NIR filter element 5 corresponds to a dedicated one of two NIR filter channels.

In the exemplary arrangement of Fig. 5, each second mosaic element 11 consists of 12 visible filter elements 3 corresponding to 12 different visible filter channels, arranged in a 3x4 matrix. The second mosaic element 11 can be further divided into a first mosaic area 6 comprising 6 visible filter elements 3; and a second mosaic area 7 comprising 6 visible filter elements 3.

In the exemplary arrangement of Fig. 6, each second mosaic element 11 consists of 9 visible filter elements 3 corresponding to 9 different visible filter channels, arranged in a 3x3 matrix. In this arrangement, similarly to the arrangement of Fig. 2, each visible filter element 3 corresponds to 4 pixels of the image sensor 14 in a 2x2 pixel binning arrangement.

Fig. 7 illustrates a multispectral imaging system with a multispectral filter array 1 comprising a first filter area 8, a second filter area 10 and a third filter area 12 arranged between the first filter area 8 and the second filter area 10, as explained before with respect to Figs. 5 and 6.

In this arrangement, each first mosaic element 9 arranged in the first filter area 8 consists only of visible filter elements 3 and UV filter elements 4, wherein each second mosaic element 11 arranged in the second filter area 10 consists only of NIR filter elements 5.

In an alternative version of this arrangement (not shown) each first mosaic element 9 arranged in the first filter area 8 consists only of visible filter elements 3 and NIR filter elements 5, wherein each second mosaic element 11 arranged in the second filter area 10 consists only of UV filter elements 4.

In an embodiment all the NIR/UV filter elements 4 when arranged in the second mosaic element 11 correspond to a single NIR/UV filter channel. In another embodiment the NIR/UV filter elements 4 when arranged in the second mosaic element 11 are distributed to correspond to a dedicated one of two or three NIR/UV filter channels.

In a possible arrangement each first mosaic element 9 comprises 16 filter elements arranged in a 4x4 matrix, with 14 visible filter elements 3 and 2 UV filter elements 4. In another possible arrangement (not shown) each first mosaic element 9 comprises 9 filter elements arranged in a 3x3 matrix. In both possible arrangements, as described before, adjacent filter elements correspond to different filter channels (i.e. the UV filter elements 4 are arranged with visible filter elements 3 in between).

Fig. 8 illustrates a multispectral imaging system with a multispectral filter array 1 according to the example shown in Fig. 5, wherein the multispectral filter array 1 is arranged on an image sensor 14. In an embodiment the image sensor 14 is a CMOS image sensor 14. In an embodiment the pixel resolution of the image sensor 14 is 1600 x 1200 px.

As shown in Fig. 8, a first image lens 16 arranged to cover the first filter area 8; and a second image lens 17 arranged to cover the second filter area 10; wherein at least one of the first image lens 16 and the second image lens 17 is adapted to the wavelength range of the light spectrum transmitted by the filter elements arranged in the corresponding filter area. This allows each lens to be designed specifically for the underlying filter area, which enables high quality and resolution of image sensing with the possibility of lenses configured for dedicated processing algorithms.

The various aspects and implementations have been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed subject-matter, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

The reference signs used in the claims shall not be construed as limiting the scope.

Claims

1. A multispectral filter array (1) for an image sensor (14), the filter array (1) comprising: a plurality of identical mosaic elements (2) arranged in a two-dimensional pattern; each mosaic element (2) comprising a plurality of filter elements (3, 4, 5) configured to transmit spectral energy through a corresponding filter channel; the plurality of filter elements (3, 4, 5) comprising: a plurality of visible filter elements (3) each configured to transmit spectral energy in a different band of the visible light spectrum; at least one UV filter element (4) configured to transmit spectral energy in an ultraviolet range of the invisible light spectrum; and at least one NIR filter element (5) configured to transmit spectral energy in a near-infrared range of the invisible light spectrum.

2. The multispectral filter array (1) according to claim 1 , wherein each mosaic element (2) comprises a plurality of visible filter elements (3), a plurality of UV filter elements (4), and a plurality of NIR filter elements (5).

3. The multispectral filter array (1) according to claim 2, wherein each of the plurality of visible filter elements (3) is configured to transmit spectral energy in a different band of the visible light spectrum, through a corresponding one of a plurality of visible filter channels, each of the plurality of UV filter elements (4) is configured to transmit spectral energy in the same ultraviolet range of the invisible light spectrum, through a single UV filter channel, and each of the plurality of NIR filter elements (5) is configured to transmit spectral energy in the same near-infrared range of the invisible light spectrum, through a single NIR filter channel.

4. The multispectral filter array (1) according to any one of claims 1 to 3, wherein each mosaic element (2) comprises 16 filter elements arranged in a 4x4 matrix.

5. The multispectral filter array (1) according to claim 4, wherein each mosaic element (2) comprises:

12 visible filter elements (3) corresponding to 12 different visible filter channels;

2 UV filter elements (4) corresponding to a single UV filter channel; and

2 NIR filter elements (5) corresponding to a single NIR filter channel; and wherein the filter elements in each mosaic element (2) are arranged so that adjacent filter elements correspond to different filter channels.

6. The multispectral filter array (1) according to claim 5, wherein each mosaic element (2) is divided into a first mosaic area (6) comprising 6 visible filter elements (3), 1 UV filter element (4), and 1 NIR filter element (5); and a second mosaic area (7) comprising 6 visible filter elements (3), 1 UV filter element (4), and 1 NIR filter element (5).

7. The multispectral filter array (1) according to claim 4, wherein each mosaic element (2) comprises:

8 visible filter elements (3) corresponding to 8 different visible filter channels;

4 UV filter elements (4) corresponding to a single UV filter channel; and

4 NIR filter elements (5) corresponding to a single NIR filter channel; and wherein the filter elements in each mosaic element (2) are arranged so that adjacent filter elements correspond to different filter channels.

8. The multispectral filter array (1) according to claim 7, wherein the filter elements in each mosaic element (2) are arranged so that each UV filter element (4) is adjacent to a NIR filter element (5).

9. The multispectral filter array (1) according to claim 7, wherein the filter elements in each mosaic element (2) are arranged so that each UV filter element (4) and NIR filter element (5) is only adjacent to visible filter elements (3).

10. A multispectral filter array (1) for an image sensor (14), the filter array (1) comprising: a first filter area (8) comprising a plurality of identical first mosaic elements (9) arranged in a two-dimensional pattern; and a second filter area (10) comprising a plurality of identical second mosaic elements (11) arranged in a two-dimensional pattern; each of the first mosaic element (9) and the second mosaic element (11) comprising at least one of a plurality of UV filter elements (4) configured to transmit spectral energy in an ultraviolet range of the invisible light spectrum, a plurality of NIR filter elements (5) configured to transmit spectral energy in a near-infrared range of the invisible light spectrum, and a plurality of visible filter elements (3) each configured to transmit spectral energy in a different band of the visible light spectrum.

11. The multispectral filter array (1) according to claim 10, wherein each first mosaic element (9) consists of a plurality of UV filter elements (4) and a plurality of NIR filter elements (5); and wherein each first mosaic element (11) consists of a plurality of visible filter elements (3).

12. The multispectral filter array (1) according to claim 11 , wherein each first mosaic element (9) consists of 2 UV filter elements (4) and 2 NIR filter elements (5) arranged in a 2x2 matrix; and wherein the different filter elements in the first mosaic element (9) are arranged alternatingly so that each UV filter element (4) is only adjacent to NIR filter elements (5) and vice versa.

13. The multispectral filter array (1) according to any one of claim 11 or 12, wherein each first mosaic element (11) consists of 12 visible filter elements (3) corresponding to 12 different visible filter channels, arranged in a 3x4 matrix.

14. The multispectral filter array (1) according to claim 13, wherein each first mosaic element (11) is divided into a first mosaic area (6) comprising 6 visible filter elements (3); and a second mosaic area (7) comprising 6 visible filter elements (3).

15. The multispectral filter array (1) according to any one of claim 11 or 12, wherein each first mosaic element (11) consists of 9 visible filter elements (3) corresponding to 9 different visible filter channels, arranged in a 3x3 matrix.

16. The multispectral filter array (1) according to claim 10, wherein each first mosaic element (9) consists of a plurality of visible filter elements (3) a plurality of UV filter elements (4); and wherein each first mosaic element (11) consists of a plurality of NIR filter elements (5).

17. The multispectral filter array (1) according to claim 10, wherein each first mosaic element (9) consists of a plurality of visible filter elements (3) a plurality of NIR filter elements (5); and wherein each first mosaic element (11) consists of a plurality of UV filter elements (4).

18. The multispectral filter array (1) according to any one of claim 16 or 17, wherein each first mosaic element (9) comprises 9 filter elements arranged in a 3x3 matrix.

19. The multispectral filter array (1) according to any one of claim 16 or 17, wherein each first mosaic element (9) comprises 16 filter elements arranged in a 4x4 matrix.

20. The multispectral filter array (1) according to any one of claims 10 to 19, further comprising a third filter area (12) arranged between the first filter area (8) and the second filter area (10), the third filter area (12) consisting of dummy mosaic elements (13) configured not to transmit spectral energy in any light spectrum.

21. A multispectral imaging system comprising: a multispectral filter array (1) according to any one of claims 1 to 20; the multispectral filter array (1) being arranged on an image sensor (14); and at least one image lens (15) arranged to cover the multispectral filter array (1).

22. The multispectral imaging system according to claim 21 , comprising: a multispectral filter array (1) according to any one of claims 10 to 20 comprising first filter area (8) and a second filter area (10); wherein the system comprises a first image lens (16) arranged to cover the first filter area (8); and a second image lens (17) arranged to cover the second filter area (10); wherein at least one of the first image lens (16) and the second image lens (17) is adapted to the wavelength range of the light spectrum transmitted by the filter elements arranged in the corresponding filter area.

23. The multispectral imaging system according to any one of claims 21 to 22, wherein a filter element of the multispectral filter array (1) corresponds to a single pixel of the image sensor (14).

24. The multispectral imaging system according to any one of claims 21 to 22, wherein a filter element of the multispectral filter array (1) corresponds to 4 pixels of the image sensor (14) in a 2x2 pixel binning arrangement.