PATTERNS OF COLOR AND DEPTH PIXELS IN AN IMAGE ACQUISITION SENSOR

Description

[0001] This application claims priority from French patent application 21 / 02581 Domaine technique

[0002] This description relates generally to the field of image acquisition devices. This description relates more particularly to image acquisition devices adapted to acquire a 2D image and a depth image of a scene. Technique antérieure

[0003] Image acquisition devices are known that are capable of acquiring a 2D image and a depth image of a scene. In particular, devices are known that comprise 2D image pixels and depth pixels integrated into an array of photodetectors of the same image sensor. Examples of such devices are described in particular in patent applications US2018167606 and US2019191067 previously filed by the applicant. Patent application US 2012 / 293696 discloses an image sensor comprising a plurality of pixels distributed into elementary groups of 5x5 pixels, each row and each column of each elementary group comprising 1 or 2 R pixels, 1 or 2 B pixels, and 2 or 3 G pixels. This arrangement reduces colored moiré. Summary of the invention

[0004] There is a need to improve existing devices for acquiring a 2D image and a depth image of a scene. In particular, it would be desirable to produce an image sensor integrating, in the same photodetector array, 2D image pixels and depth pixels, the sensor having, for the acquisition of 2D images and depth images, reduced colorimetric performance and artifacts compared to known sensors.

[0005] An object of an embodiment is to overcome all or part of the drawbacks of known devices for acquiring a 2D image and a depth image of a scene.

[0006] For this, one embodiment provides an image sensor comprising a plurality of pixels distributed into elementary groups, each elementary group consisting of several adjacent pixels arranged in a matrix according to rows and columns, each elementary group comprising first, second and third visible image pixels sensitive in different wavelength ranges and fourth depth image pixels, in which each row of each elementary group comprises at least one fourth pixel.

[0007] According to one embodiment, each column of each elementary group comprises at least a fourth pixel.

[0008] According to one embodiment, the first and second pixels are chrominance pixels and the third pixels are luminance pixels.

[0009] According to one embodiment, the first pixels are sensitive mainly to red light and the second pixels are sensitive mainly to blue light.

[0010] According to one embodiment, the third pixels are sensitive mainly to green light.

[0011] According to one embodiment, the third pixels comprise pixels of a first type and pixels of a second type sensitive in different wavelength ranges.

[0012] According to one embodiment, the third pixels of the first type are sensitive mainly to green light and the third pixels of the second type are sensitive mainly to white, yellow or emerald green light.

[0013] According to one embodiment, within each group of pixels, all rows and all columns have the same number of third pixels of the first type and third pixels of the second type.

[0014] According to one embodiment, within each elementary group, all the rows and all the columns have the same number of first pixels and the same number of second pixels.

[0015] According to one embodiment, within each elementary group, each line comprises two to four times more third pixels than first pixels.

[0016] According to one embodiment, within each elementary group, each column comprises two to four times more third pixels than second pixels.

[0017] According to one embodiment, within each elementary group, each row and each column comprises as many second pixels as first pixels.

[0018] According to one embodiment, within each elementary group, each row and each column comprises as many fourth pixels as second pixels.

[0019] According to one embodiment, the fourth pixels are time-of-flight distance measurement pixels.

[0020] One embodiment provides an image sensor comprising a plurality of pixels distributed in elementary groups of 5x5 pixels, each elementary group consisting of several adjacent pixels arranged in a matrix according to rows and columns, each row and each column of each elementary group comprising exactly: a first visible image pixel sensitive mainly to red light; a second visible image pixel sensitive mainly to blue light; two third luminance pixels; and a fourth depth image pixel. Brève description des dessins

[0021] These and other features and advantages will be set forth in detail in the following description of particular embodiments given without limitation in relation to the attached figures, among which: there figure 1 is a top view schematically and partially illustrating an example of an embodiment of a 2D image and depth image sensor; figure 2 is a top view schematically illustrating an exemplary embodiment of an elementary group of pixels of the image sensor of the figure 1 ; there figure 3 is a top view schematically illustrating another example of embodiment of the elementary group of pixels of the image sensor of the figure 1 ; there figure 4 is a top view schematically illustrating yet another example of embodiment of the elementary group of pixels of the image sensor of the figure 1 ; there figure 5 is a top view schematically illustrating yet another example of embodiment of the elementary group of pixels of the image sensor of the figure 1 ; there figure 6 is a top view schematically illustrating yet another example of embodiment of the elementary group of pixels of the image sensor of the figure 1 ; there figure 7 is a top view schematically illustrating yet another example of embodiment of the elementary group of pixels of the image sensor of the figure 1 ; there figure 8 is a top view schematically illustrating yet another example of embodiment of the elementary group of pixels of the image sensor of the figure 1 ; there figure 9 is a top view schematically illustrating yet another example of embodiment of the elementary group of pixels of the image sensor of the figure 1 ; there figure 10 is a top view schematically illustrating yet another example of embodiment of the elementary group of pixels of the image sensor of the figure 1 ; and the figure 11 is a sectional view schematically and partially illustrating a 2D image pixel and a depth pixel of the image sensor of the figure 1 . Description des modes de réalisation

[0022] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0023] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the production of the photodiodes and the control circuits of the 2D image pixels and the depth pixels has not been detailed, the production of such pixels being within the scope of the person skilled in the art from the indications of the present description.

[0024] Unless otherwise specified, when two elements are connected together, this means directly connected without intermediate elements other than conductors, and when two elements are connected (in English "coupled") together, this means that these two elements can be connected or be connected by means of one or more other elements.

[0025] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0026] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0027] There figure 1 is a top view schematically and partially illustrating an example of an embodiment of an image sensor 1.

[0028] In the example shown, the sensor 1 comprises a plurality of PIX pixels. The PIX pixels are, in this example, arranged in a matrix according to rows and columns. The rows are for example substantially perpendicular to the columns. Each row of PIX pixels of the sensor 1 corresponds for example to a horizontal row, in the orientation of the figure 1 , of adjacent PIX pixels. Each column of PIX pixels of sensor 1 corresponds for example to a vertical row, in the orientation of the figure 1 , of adjacent PIX pixels.

[0029] The PIX pixels of sensor 1, for example, each have a roughly square shape, as illustrated in figure 1 . All PIX pixels, for example, have identical lateral dimensions, apart from manufacturing variations.

[0030] The image sensor 1 comprises, among the pixels PIX of the matrix, 2D image pixels or visible image pixels. The 2D image pixels are for example adapted to capture visible light coming from a scene to form a two-dimensional image of this scene. In the case where the image sensor 1 is adapted to capture 2D color images, the 2D image pixels are of different types, for example adapted to measure light intensities in distinct wavelength ranges. Each 2D image pixel comprises for example a color bandpass filter, transmitting for example mainly green, red or blue radiation depending on the wavelength range of the pixel.

[0031] Among the PIX pixels, the image sensor 1 comprises, in addition to the 2D image pixels, depth pixels. The depth pixels are, for example, suitable for estimating distances between the sensor 1 and points in the scene. This makes it possible to form a depth image or map of the scene. Each depth pixel comprises, for example, a depth bandpass filter, transmitting, for example, mainly radiation in the near infrared. For example, each depth pixel comprises a filter structure having a maximum transmittance for a wavelength equal to approximately 850, 905 or 940 nm and a spectral width (half-maximum width of the transmission band) of between 20 and 30 nm.

[0032] The sensor 1 is for example intended to be used in combination with a light source, for example a laser source, emitting light at a specific wavelength or in a specific wavelength range. The emission wavelength range of the light source is for example located outside the visible range, for example in the near infrared, for example in the range of 700 to 1000 nm. For example, when the depth filter has a maximum transmittance for a wavelength equal to approximately 940 nm, the source has an emission wavelength range centered on approximately 940 nm and with a width at half maximum of less than 3 nm.

[0033] In operation, the light signal produced by the light source is emitted towards the scene, for example in the form of light pulses, for example periodic. The return light signal reflected by the scene is captured by the depth pixels of the image sensor 1, for example so as to measure the time of flight of the light signal at different points of the scene, which makes it possible to estimate the distance of these points relative to the image sensor 1. As a variant, the light signal produced by the light source can form a structured light pattern. The return light signal reflected by the scene is captured by the depth pixels of the image sensor 1. The analysis of the deformations of the pattern by the scene makes it possible to determine depth information.

[0034] For example, the depth image of the scene can be combined with the 2D image of the same scene. Such combinations can be used in applications such as facial recognition, virtual or augmented reality, autonomous driving of vehicles, etc.

[0035] In figure 1 , the 2D image pixels and depth pixels of image sensor 1 are not differentiated.

[0036] In the example shown, the PIX pixels of the sensor 1 are distributed into elementary groups 3. In this example, each PIX pixel belongs to only one elementary group 3. The elementary groups 3 of the sensor 1 are each made up of several adjacent PIX pixels, that is to say that two PIX pixels forming part of the same elementary group 3 are not separated by one or more PIX pixels belonging to another elementary group 3. Inside each elementary group 3, the PIX pixels are arranged in a matrix according to rows and columns.

[0037] Each elementary group 3 defines, in top view, an elementary mosaic pattern corresponding to the smallest set of PIX pixels from which it is possible to reconstruct, by horizontal and vertical translations of the pattern, the arrangement of all the PIX pixels of the matrix of the sensor 1. The elementary groups 3 of the sensor 1 are identical to each other, apart from manufacturing dispersions. All the elementary groups 3 of the sensor 1 have the same number of PIX pixels. In addition, all the elementary groups 3 have the same number of 2D image pixels and the same number of depth pixels. The 2D image pixels and the depth pixels are arranged in relation to each other in an identical manner for all the elementary groups 3 of the sensor 1.

[0038] Each elementary group 3 comprises, for example, a network of color filters and depth filters ("Color and Depth Filter Array" - CDFA). The network of color filters and depth filters of each elementary group 3 constitutes, for example, the smallest pattern from which it is possible to reconstruct, by translations of the pattern, the arrangement of the color filters and depth filters of the entire matrix of pixels PIX of the sensor 1.

[0039] There figure 2 is a top view schematically illustrating an example of embodiment of the elementary group 3 of PIX pixels of the image sensor 1 of the figure 1 .

[0040] In the example shown, elementary group 3 comprises 2D image pixels of different types and depth pixels. More specifically, in this example, elementary group 3 comprises: 2D image R pixels, for example sensitive mainly to red light; other 2D image G pixels, for example sensitive mainly to green light; still other 2D image B pixels, for example sensitive mainly to blue light; and depth Z pixels, for example sensitive mainly to infrared light.

[0041] In the invention, the elementary group 3 comprises twenty-five pixels PIX distributed in five rows and five columns.

[0042] According to the invention, each row of elementary group 3 comprises exactly one depth Z pixel. The fact that each row comprises one depth Z pixel makes it possible to reduce the presence of artifacts in the visible 2D image. In addition, each column of elementary group 3 comprises exactly one depth Z pixel. In the example shown, each row of PIX pixels of elementary group 3 comprises a single depth Z pixel. Furthermore, in this example, each column of PIX pixels of elementary group 3 comprises a single depth Z pixel.

[0043] In the example shown, the rows of PIX pixels in elementary group 3 all have as many Z pixels as B pixels. Furthermore, in this example, all columns of PIX pixels in elementary group 3 have as many Z pixels as B pixels.

[0044] In the example illustrated in figure 2 , the rows of PIX pixels of elementary group 3 all have the same number of R pixels and the same number of B pixels. Furthermore, in this example, all the columns of PIX pixels of elementary group 3 have the same number of R pixels and the same number of B pixels. The number of R pixels and the number of B pixels in each row are respectively equal to the number of R pixels and the number of B pixels in each column. In the example shown, each row of PIX pixels of elementary group 3 has as many R pixels as B pixels. Furthermore, in this example, each column of PIX pixels of elementary group 3 has as many R pixels as B pixels. The fact that each row and each column includes one R pixel and one B pixel makes it possible to reduce the presence of colored artifacts (colored moiré or "aliasing" in English) in the visible 2D image.

[0045] In the example shown, the rows of PIX pixels in elementary group 3 all have as many Z pixels as R pixels. Furthermore, in this example, all the columns of PIX pixels in elementary group 3 have as many Z pixels as R pixels.

[0046] In the example shown, all rows of PIX pixels in elementary group 3 have the same number of G pixels. Furthermore, in this example, all columns of PIX pixels in elementary group 3 have the same number of G pixels. The number of G pixels in each row is equal to the number of G pixels in each column.

[0047] In the example illustrated in figure 2 , each row of PIX pixels in elementary group 3 has twice as many G pixels as R pixels. Furthermore, in this example, each column of PIX pixels in elementary group 3 has twice as many G pixels as R pixels.

[0048] In this example, the G pixels correspond to luminance pixels of sensor 1. A luminance pixel means a pixel providing a majority contribution to a Y luminance signal.

[0049] The R and B pixels correspond to chrominance pixels of the image sensor 1. Chrominance pixels are pixels that produce a U chrominance signal, called the "blue difference", and another V chrominance signal, called the "red difference".

[0050] For the purposes of the present application, in the case of a sensor comprising N types of distinct 2D pixels, adapted to detect light radiation in N distinct wavelength ranges, centered respectively on N distinct wavelength values ​​λ1, λ2, ... λN, with N integer greater than or equal to 3 and λ1 < λ2 ... < λN, the term chrominance pixels refers to the two types of pixels having respectively as their central sensitivity wavelength the two extreme wavelengths λ1 and λN of the detection spectrum, and luminance pixels refer to the other type(s) of 2D pixels, having as their central sensitivity wavelength(s) the intermediate wavelength(s) λi of the detection spectrum, with i integer ranging from 2 to N-1.

[0051] Central wavelength means the wavelength at which the pixel exhibits maximum transmission in the visible spectrum.

[0052] For example, G pixels whose filters are selectively transparent in the green region of the visible spectrum are used to produce the Y luminance signal and R and B pixels whose filters are selectively transparent in the red and blue regions of the visible spectrum respectively are used to produce the V and U chrominance signals.

[0053] THE figures 3 And 4 are top views schematically illustrating other examples of embodiment of the elementary group 3 of PIX pixels of the image sensor 1.

[0054] The examples of realization of elementary group 3 illustrated in figures 3 And 4 each have the same number of PIX pixels as in the example of the figure 2 , namely a 5x5 pixel matrix PIX. The elementary groups 3 of the figures 3 And 4each have a distribution of R, G, B and Z pixels, by rows and by columns of the matrix, identical to that previously described in relation to the figure 2 .

[0055] In particular, the proportions of R, B, G and Z pixels per row and per column of elementary group 3 of the figure 3 and elementary group 3 of the figure 4 are identical to the proportions of R, B, G and Z pixels per row and per column of elementary group 3 of the figure 2 . Elementary groups 3 of the figures 3 And 4 differ from elementary group 3 of the figure 2 by the positioning of the R, G, B and Z pixels in each row and in each column.

[0056] In the embodiments set forth above in relation to the figures 2 à 4 , each elementary group 3 has exactly 5x5 PIX pixels, that is, exactly five columns and exactly five rows of PIX pixels. Each row and each column of each of the elementary groups 3 of the figures 2 à 4 comprises a single Z pixel, a single B pixel, a single R pixel and two G pixels. This gives an optimal configuration that minimizes the number of calculations required to reconstruct an image captured by sensor 1. Each row and each column comprising exactly one Z pixel and one pixel from each chrominance channel (a single B pixel and a single R pixel), each depth and chrominance information is present only once on each row and each column. Each Z, R, B pixel is also equidistant from four nearest neighboring pixels of the same type. Each Z, R, B pixel is more precisely separated from four neighboring Z, R, B pixels by a distance approximately equal to the pixel pitch (center-to-center distance between two pixels in the pixel matrix of image sensor 1) multiplied by √3. In Fourier space, this makes it possible to avoid repetition frequencies located at identical locations.This provides an even distribution, thus avoiding or reducing the appearance of colored moiré effects on the image in both horizontal and vertical directions.

[0057] As a variant, it is possible to replace all or part of the luminance pixels G of the elementary group 3 with luminance pixels W of another type. Examples of embodiments of such elementary groups are described below in relation to the figures 5 à 8 .

[0058] There figure 5 is a top view schematically illustrating yet another example of embodiment of the elementary group 3 of PIX pixels of the image sensor 1.

[0059] The example of the figure 5 presents common elements with the example of the figure 2 . These common elements will not be described again below. The example illustrated in figure 5 differs from the example illustrated in figure 2 in that, in the example of the figure 5 , a part of the 2D image luminance G pixels are replaced by W luminance pixels of another type. The W luminance pixels are 2D image pixels and have, for example, a different sensitivity wavelength range than the G pixels.

[0060] W pixels are, for example, panchromatic, i.e., suitable for detecting light over a large part, or even the entirety, of the visible spectrum, for example between 400 and 700 nm. For this purpose, each 2D W image pixel includes, for example, a panchromatic filter. Alternatively, W pixels can be pixels sensitive mainly to yellow light, or to emerald green light. For this purpose, each 2D W image pixel includes, for example, a yellow or emerald green filter.

[0061] In the example shown, with respect to elementary group 3 of the figure 2 , one G pixel out of two is replaced by a W pixel. More precisely, half of the G pixels in each row, or half of the G pixels in each column, are for example substituted by a W pixel. In the example shown, each row has as many W pixels as G pixels, and each column has as many W pixels as G pixels.

[0062] Alternatively, an elementary group may be provided in which, with respect to elementary group 3 of the figure 5 , all G pixels are substituted by W pixels and all W pixels are substituted by G pixels.

[0063] There figure 6 is a top view schematically illustrating yet another example of embodiment of the elementary group 3 of PIX pixels of the image sensor 1.

[0064] The example of the figure 6 presents common elements with the examples of the figures 2 And 5. These common elements will not be described again below. The example illustrated in figure 6 differs from the examples illustrated in figures 2 And 5 in that, in the example of the figure 6 , all 2D image luminance G pixels are replaced by luminance W pixels.

[0065] In this example, each row has twice as many W pixels as Z, R, or B pixels, and each column has twice as many W pixels as Z, R, or B pixels. Specifically, in the example shown in figure 6 , each column has exactly two W pixels, one Z pixel, one R pixel and one B pixel. Similarly, each row of elementary group 3 of the figure 6 has exactly two W pixels, one Z pixel, one R pixel, and one B pixel.

[0066] There figure 7 is a top view schematically illustrating yet another example of embodiment of the elementary group 3 of PIX pixels of the image sensor 1.

[0067] The example of the figure 7 presents common elements with the example of the figure 2 . These common elements will not be described again below. The example illustrated in figure 7 differs from the example illustrated in figure 2 in that, in the example of the figure 7 , part of the 2D image luminance G pixels are replaced by luminance W pixels.

[0068] In the example shown, with respect to elementary group 3 of the figure 2 , half of the G pixels are replaced by W pixels. More precisely, all the G pixels of every other row, for example all the G pixels belonging to rows of even rank, are for example substituted by W pixels. In the example shown, with respect to elementary group 3 of the figure 2 , all G pixels of the second and fourth rows of PIX pixels of elementary group 3 are substituted by W pixels.

[0069] An advantage of elementary group 3 of the figure 7 compared to that of the figure 5 is due to the fact that the W pixels are grouped side by side in pairs, which can simplify their production.

[0070] There figure 8 is a top view schematically illustrating yet another example of embodiment of the elementary group 3 of PIX pixels of the image sensor 1.

[0071] The example of the figure 8 presents common elements with the example of the figure 2 . These common elements will not be described again below. The example illustrated in figure 8 differs from the example illustrated in figure 2 in that, in the example of the figure 8 , part of the 2D image luminance G pixels are replaced by luminance W pixels.

[0072] In the example shown, with respect to elementary group 3 of the figure 2 , half of the G pixels are replaced by W pixels. More precisely, all the G pixels of every other row, for example all the G pixels belonging to odd-rank rows, are for example substituted by W pixels. In the example shown, with respect to elementary group 3 of the figure 2 , all G pixels of the first, third and fifth rows of PIX pixels of elementary group 3 are substituted by W pixels.

[0073] There figure 9 is a top view schematically illustrating yet another example of the elementary group 3 of pixels PIX of the image sensor 1, which is not part of the invention.

[0074] In the example shown, elementary group 3 comprises sixty-four PIX pixels distributed in eight rows and eight columns.

[0075] Compared to elementary group 3 of the figure 5 , each row and each column of pixels PIX of the elementary group 3 of the figure 9 has three additional luminance pixels. In the example shown, these additional pixels are G pixels. Alternatively, the additional pixels may be, at least in part, W pixels.

[0076] In the example shown, elementary group 3 comprises an alternation of diagonals of pixels G and diagonals of pixels B, R, Z and W.

[0077] An advantage of the examples of elementary groups 3 described in relation to the figures 2 à 9 is that they enable the image sensor 1 to exhibit good colorimetric performance. In addition, 2D images captured by the image sensor 1 exhibit few color reconstruction artifacts such as colored moiré (aliasing).

[0078] More generally, in one embodiment each elementary group 3 of pixels is a square matrix of 5x5 pixels, in which each row of pixels comprises exactly one pixel of depth. Each column of pixels comprises exactly one pixel of depth. All the rows and all the columns have the same number of chrominance pixels of each type. The chrominance pixels of one type, for example the chrominance pixels having as their central sensitivity wavelength the lower wavelength λ1 of the detection spectrum, are present, on each row and on each column of the matrix, in the same quantity as the chrominance pixels of the other type, that is to say, in this example, the chrominance pixels having as their central sensitivity wavelength the upper wavelength λN of the detection spectrum.Each row of the pixel group 3 matrix contains twice as many luminance pixels as chrominance pixels of each type. In addition, each column of the pixel group 3 matrix contains twice as many luminance pixels as chrominance pixels of each type. All rows and columns contain the same number of luminance pixels of each type. The number of depth pixels is also equal, in each row and column, to the number of chrominance pixels of each type.

[0079] These features enable improved colorimetric performance and reduced artifacts compared to known devices, particularly compared to known devices comprising 2D image pixels and depth pixels. This further enables depth information to be obtained with satisfactory resolution for the applications targeted by the sensor 1.

[0080] There figure 10 is a top view schematically illustrating yet another example of the elementary group 3 of pixels PIX of the image sensor 1 which is not part of the invention.

[0081] In the example shown, all rows and columns of elementary group 3 have at least one R pixel, one G pixel and one B pixel. Some rows and some columns do not have any Z pixels.

[0082] There figure 11 is a sectional view schematically and partially illustrating a 2D image pixel, for example a G pixel, and a depth Z pixel of the image sensor 1.

[0083] In the example shown, the pixels G and Z are formed in and on a substrate 801. The substrate 801 is for example made of a semiconductor material, for example silicon.

[0084] Photosensitive areas are for example formed in the substrate 801. More specifically, in this example, a photosensitive area 803G of the pixel G and a photosensitive area 803Z of the pixel Z are formed in the substrate 801. The photosensitive areas 803G and 803Z, or photoconversion areas, are for example isolated from each other and from adjacent pixels by isolation trenches 805. For example, the isolation trenches 805 are capacitive deep trench isolation (CDTI).

[0085] In the example shown, regions 807G, 807Z for collecting the photogenerated carriers respectively in the photosensitive areas 803G and 803Z are formed in the substrate 801. In this example, the regions 807G and 807Z penetrate into the thickness of the photosensitive areas 803G and 803Z from a lower face of the areas 803G and 803Z. For example, the regions 807G and 807Z are N-type doped.

[0086] Although this has not been represented in figure 11 , regions 807G and 807Z are for example connected to control circuits located in substrate 801.

[0087] In the example shown, an upper face of the substrate 801 is coated with an anti-reflective layer 809. The layer 809 makes it possible, for example, to optimize the optical performance of the pixels G and Z.

[0088] In the example illustrated in figure 11 , a color filter 811 covers a portion of the upper face of the anti-reflection layer 809 located directly above the photosensitive zone 803G of the pixel G. The color filter 811 is, in this example, a bandpass filter transmitting mainly green light.

[0089] In the example shown, the color filter 811 is coated with a layer 813. The layer 813 is for example made of a resin transmitting visible light and absorbing radiation in the detection wavelength range of the pixel Z. As a variant, the resin layer 813 can be replaced by an interference filter. As a variant, it can be provided that the color filter 811 coats the resin layer 813.

[0090] In the example illustrated in figure 11 , an infrared filter 815 covers a portion of the upper face of the anti-reflection layer 809 located directly above the photosensitive zone 803Z of the pixel Z. The infrared filter 815 is, in this example, a bandpass filter adapted to transmit mainly infrared radiation in the detection wavelength range of the pixel Z.

[0091] In the example shown, the upper face of the resin layer 813 and the upper face of the infrared filter 815 are respectively coated with layers 817 and 819. Microlenses 821 and 823 are respectively located on and in contact with the upper face of the layers 817 and 819.

[0092] Layers 817 and 819 make it possible, for example, to compensate for height differences between, on the one hand, a stack consisting of the color filter 811 and the layer 813 and, on the other hand, the layer 815. This makes it possible, for example, to obtain a flat surface before the production of the microlenses 821 and 823.

[0093] In the example shown, the color filter 811 and the layer 813 are optically isolated from the filter 815 by a screen 825 and a vertical layer 827. For example, the screen 825 is made of a metal, for example tungsten, and the layer 827 is made of a material having a refractive index lower than the refractive indices of the layers 811, 813 and 815.

[0094] In the example shown, a filter 829 is located above the microlenses 821 and 823. The filter 829 is for example a “dual-band” type filter, for example adapted to transmit all or part of the visible spectrum and part of the infrared spectrum in the operating wavelength range of the pixel Z. By way of example, the filter 829 allows radiation to pass over a first wavelength range between 350 and 650 nm and over a second wavelength range between 920 and 960 nm, and cuts off the radiation outside these ranges.

[0095] The R, B and possibly W pixels of the sensor 1 may have a structure similar to that set out above in relation to the G pixel, the color filter 811 being for example adapted according to the type of pixel.

[0096] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, the R, G, and B pixels sensitive primarily to red, green, and blue may be replaced by pixels sensitive to other colors, for example, cyan, yellow, and magenta.

[0097] Furthermore, although application examples have been described above in which the depth pixels of the image sensor are suitable for performing time-of-flight distance measurements, the embodiments are more generally transposable to image sensors comprising any type of pixel making it possible to provide depth information, for example structured light acquisition pixels, avalanche photodiodes for detecting single photons (Single Photon Avalanche Diode - SPAD), etc.

[0098] Finally, the practical implementation of the embodiments and variants described is within the reach of the person skilled in the art from the functional indications given above.

Claims

1. An image sensor (1) comprising a plurality of pixels (PIX) divided in elementary groups (3) of 5x5 pixels, each elementary group consisting of a plurality of adjacent pixels arranged in a matrix, in rows and columns, each row and each column of each elementary group including exactly: - a first visible image pixel (R) predominantly sensitive to red light; - a second visible image pixel (B) predominantly sensitive to blue light; - two third luminance pixels (G, W); the sensor being characterized in that each row and each column of the elementary group (3) includes exactly: - a fourth depth image pixel (Z).

2. The sensor according to claim 1, wherein all third pixels (G) are predominantly sensitive to green light.

3. The sensor according to claim 1, wherein all third pixels (W) are predominantly sensitive to white, yellow or emerald-green light.

4. The sensor according to claim 1, wherein the third pixels include pixels of a first type (G) and pixels of a second type (W) sensitive in different wavelength ranges.

5. The sensor according to claim 4, wherein: - the third pixels of the first type (G) are predominantly sensitive to green light; and - the third pixels of the second type (W) are predominantly sensitive to white, yellow or emerald-green light.

6. The sensor according to claim 4 or 5, wherein each elementary group (3) has as many third pixels of the first type (G) as third pixels of the second type (W).

7. The sensor according to claim 6, wherein, within each group (3) of pixels, all rows and all columns have an equal number of third pixels of the first type (G) and of third pixels of the second type (W).

8. The sensor according to claim 6, wherein, within each group (3) of pixels, the third pixels of every other row are all of the first type (G), the third pixels of the other rows being all of the second type (W).

9. The sensor according to any of claims 1 to 8, wherein the fourth pixel (Z) is a pixel for measuring distance by time-of-flight.