High dynamic range pixel

Abstract

High Dynamic Range Pixel This description relates to a pixel (1) comprising a photosensitive element (PD) and a filter (110) above a face (102) of the photosensitive element intended to receive light. The filter (110) comprises a plurality of identical patterns (112) of a phase-change material. The filter (1) comprises a plurality of heating elements defined in an electrically conductive layer (114) of the filter and configured such that a temperature of the heating elements determines a temperature of the phase-change material. The pixel (1) further comprises a circuit for controlling the temperature of the heating elements. Figure for the abstract: Fig. 1

Description

Title of the invention: High dynamic range pixel technical field

[0001] The present description relates generally to electronic circuits, and more particularly to a high dynamic range (HDR) pixel and a light sensor comprising a plurality of high dynamic range pixels. Previous technique

[0002] A pixel is an element configured to convert light received within a range of pixel operating wavelengths into a pixel output signal, for example a current or a voltage, having a value representative of the amount of light received.

[0003] When a sensitive pixel operates in low-light conditions, a small change in the amount of light received results in a corresponding change in the pixel's output signal. However, a drawback of a sensitive pixel is that, when it operates in high-light conditions, the pixel's output signal saturates and its value is no longer representative of the amount of light received.

[0004] Conversely, a less sensitive pixel, when operating in bright light conditions, ensures that its output signal does not saturate and accurately reflects the amount of light received. However, when a less sensitive pixel operates in low light conditions, the amount of light received is insufficient to cause a corresponding change in the pixel's output signal, and the light is not detected by the pixel.

[0005] To overcome the above drawbacks, so-called high dynamic range pixels have been proposed; that is, pixels whose output signal varies with the amount of light received, whether the pixel is operating in low or high light conditions. For example, a pixel is said to have a high dynamic range when its output signal varies substantially linearly over a dynamic range of at least 80 dB, preferably at least 90 dB. More preferably, a pixel is said to have a high dynamic range when its output signal varies substantially linearly over a dynamic range of at least 100 dB, preferably at least 115 dB.

[0006] However, these high dynamic range pixels have several drawbacks. For example, these pixels are more complex and / or bulkier to implement. For example, these pixels require more complex and / or expensive specific processing circuits. Summary of the invention

[0007] There is a need for a high dynamic range pixel that overcomes all or part of the disadvantages of known high dynamic range pixels.

[0008] One embodiment overcomes all or part of the known disadvantages of high dynamic range pixels.

[0009] One embodiment provides for a pixel comprising: a photosensitive element; a filter above one face of the photosensitive element intended to receive light, the filter comprising: - a plurality of identical patterns in a phase-change material, and - a plurality of heating elements defined in an electrically conductive layer of the filter, the electrically conductive layer being parallel to said face intended to receive light and the heating elements being configured so that a temperature of the heating elements determines a temperature of the phase-change material of the patterns; and a circuit configured to control the temperature of the heating elements.

[0010] According to one embodiment, the filter is configured so that a filter transmission rate for light in a range of operating wavelengths depends on a phase-change material state.

[0011] According to one embodiment, the patterns are arranged periodically.

[0012] According to one embodiment, each motif comprises two parallel faces between they and to the electrically conductive layer, the pattern extending from one to the other of said two faces and having a first of said two faces which is turned towards the electrically conductive layer.

[0013] According to one embodiment, the filter comprises, for each pattern, a portion of anti-reflective layer resting on and in contact with that of said two faces of the pattern which is intended to receive light.

[0014] According to one embodiment: the anti-reflective layer is in tantalum nitride or oxide, for example tantalum pentoxide, and the phase-change material is antimony trisulfide, antimony sulfide, germanium sulfide or germanium telluride.

[0015] According to one embodiment, the filter further comprises, on the side of the second faces of the motifs, a thermally conductive layer.

[0016] According to one embodiment, the thermally conductive layer is made of a material transparent at pixel operating wavelengths, for example in indium tin oxide.

[0017] According to one embodiment, the electrically conductive layer is made of a material transparent at pixel operating wavelengths, for example in indium tin oxide.

[0018] Another embodiment provides for a light sensor comprising a plurality of pixels as defined above.

[0019] Another embodiment provides a method comprising: to control, in a pixel comprising a photosensitive element and a filter above a face of the photosensitive element intended to receive light, with a circuit of the pixel, a temperature of a plurality of heating elements defined in a layer of the filter which is electrically conductive and parallel to said face intended to receive light, so as to modify a state of a plurality of identical patterns into a phase-change material. Brief description of the drawings

[0020] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0021] [Fig.1] represents, by a schematic cross-sectional view, an example of an embodiment of a high dynamic range pixel;

[0022] [Fig.2] represents, by a schematic perspective view, a detailed example of the implementation of a pixel filter of [Fig.1] according to one embodiment;

[0023] Figure 3 illustrates, by means of curves, the operation of an example embodiment of the pixel filter of Figure 1; and

[0024] Figure 4 schematically represents, in block form, an example of a sensor comprising a plurality of pixels of the type shown in Figure 1. Description of embodiments

[0025] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0026] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been represented and are detailed.

[0027] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements coupled together, this means that these two elements can be connected or linked through one or more other elements.

[0028] 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", "superior", "inferior", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0029] Unless otherwise specified, the expressions "approximately", "roughly", and "on the order of" mean to within 10% or 10°, preferably to within 5% or 5°.

[0030] A pixel comprising a dynamically configurable filter is proposed here so that the transmission rate of the filter, for light received in a range of operating wavelengths of the filter, is controllable, for example between at least a high transmission state for which the transmission rate is, for example, at least 80%, or even at least 90%, and a low transmission state for which the transmission rate is, for example, at most 20%, or even at most 10%.

[0031] Thus, the pixel can be designed to operate in low light conditions, the filter then being controlled to have a high transmission rate, and in high light conditions, the filter then being controlled to have a low transmission rate, so that, preferably, the output signal of the pixel does not saturate.

[0032] More specifically, the proposed filter comprises a plurality of patterns in a phase-change material, and a plurality of heating elements configured such that a temperature of the heating elements determines a temperature of the phase-change material. Thus, when, for a range of operating wavelengths of the pixel or the filter, the transmission rate of the filter depends on the state of the phase-change material, the transmission rate of the filter can be controlled by changing the state of the phase-change material, that is, by controlling the temperature of the heating elements.

[0033] One advantage of such a filter is that simply incorporating it into a pixel configured to operate under low-light conditions transforms that pixel into a high dynamic range pixel. The resulting pixel is therefore less complex, less bulky, and / or less expensive to implement than known high dynamic range pixels. In particular, the resulting pixel is, for example, less complex to implement in terms of the CMOS (Complementary Metal Oxide Semiconductor) manufacturing process. Furthermore, the resulting pixel does not require complex, bulky, and / or expensive processing circuits, as is the case with known high dynamic range pixels, for example, known high dynamic range pixels configured for multiple exposure acquisition.

[0034] Fig. 1 represents, by a schematic cross-sectional view, an example of an embodiment of a pixel 1.

[0035] Pixel 1 includes a photosensitive element PD. For example, the photoconversion element PD corresponds to a portion of a semiconductor substrate 100. For example, the photosensitive element PD extends from a rear face 102 (upper face in [Fig.1]) to a front face 104 (lower face in [Fig.1]) of the substrate 100.

[0036] Typically, electronic components (not shown in [Fig.1]), such as transistors and / or horizontal or vertical transfer gates, are arranged in and / or on the substrate 100, on the side of its front face 104.

[0037] Typically, an interconnection structure 106, for example of type BEOL (from the English "back end of line"), rests on the front face 104 of the substrate 100 and comprises portions of electrically conductive layers (not shown in [Fig.1]) connected together by electrically conductive vias (not shown in [Fig.1]) to electrically connect, together and / or to connection pads, electronic components arranged on the side of the front face 104.

[0038] In the example of [Fig. 1], pixel 1 is illuminated from the rear face 102. In other words, pixel 1 is configured so that its photosensitive element PD receives light to be converted from the rear face 102 side of the substrate 100. Put another way, the photosensitive element PD is configured to receive light from a face of the photosensitive element PD which is arranged on the rear face 102 side of the substrate 100.

[0039] By way of example, the photosensitive element PD is laterally delimited by insulation structures 105, such as deep trench isolation (DTI) or capacitive deep trench isolation (CDTI).

[0040] The face 102 of the substrate 100, i.e. the face 102 of the element PD in the example of [Fig.1], is preferably coated with a passivation layer 108 resting on and in contact with the face 102.

[0041] Pixel 1 further comprises a filter 110. The filter 110 is disposed above the face 102 of the element PD that is intended to receive light. Preferably, the filter 110 is opposite the entire surface of the photosensitive element PD that is intended to receive light. By way of example, the filter 110 rests on the passivation layer 108, for example in contact with the passivation layer 108.

[0042] The filter 110 comprises a plurality of identical patterns 112. The patterns 112 are in a phase-change material. For example, each motif 112 comprises a first face facing the PD element and parallel to the face 102, a second face parallel to the first face, and extends from one of these first and second faces to the other. The motifs 112 are arranged in a dielectric layer 113. Although this not to be visible in [Fig. 1], as an example, each motif has a cylindrical shape extending vertically from one of the first and second faces to the other, the base of the cylinder being, for example, circular or regular polygonal. As an example of a regular polygonal base, the base of motif 112 can be triangular, hexagonal, square, octagonal, decagonal, dodecagonal, etc.

[0043] Preferably, the patterns 112 are arranged periodically, for example in two directions orthogonal to each other and parallel to the face 102. For example, the period of a grating formed by the patterns 112 is determined by a range of operating wavelengths of the pixel 1, for example by a range of wavelengths of the filter 110.

[0044] Preferably, for a range of operating wavelengths of the filter 110, the patterns 112 and the layer 113 form a fan-resonant filter at least for a given state, for example the crystalline state, of the phase-change material.

[0045] The filter 110 further includes an electrically conductive layer 114. The layer 114 is parallel to the face 102, or, in other words, extends parallel to the face 102. Although this is not visible in [Fig. 1], heating elements are defined in the layer 114. These heating elements are configured so that a temperature of the heating elements determines a temperature of the phase-change material of the motifs 112, and therefore the state, for example crystalline or amorphous, of the phase-change material.

[0046] Layer 114 is made of a material that is transparent in the operating wavelength range of filter 110. For example, layer 114 is made of a material that is transparent for the operating wavelengths of pixel 1. By way of example, a layer is said to be made of a material that is transparent at a given wavelength when more than 80%, preferably more than 90%, of a light radiation at that wavelength is transmitted through the thickness of that layer.

[0047] In the example of [Fig. 1], the layer 114 is arranged between the face 102 and the motifs 112. In other words, the faces of the motifs 112 that are turned towards the photosensitive element PD are also turned towards the layer 114. In the example of [Fig. 1], the layer 114 rests on, and for example in contact with, the passivation layer 108. In this case, each motif 112 has its face turned towards the element PD which is, for example, in contact with the layer 114, for example, with one or more of the heating elements defined in the layer 114.

[0048] In other examples not shown, the layer 114 is arranged on the side of the faces of the motifs 112 that are not turned towards the face 102 of the PD element. In other words, in these other examples, the motifs 112 are arranged between the face of the PD element that is intended to receive light and the layer 114.

[0049] Furthermore, although not illustrated in [Fig.1], pixel 1 includes a circuit configured to control the temperature of the heating elements defined in layer 114. For example, the circuit is configured to control a value of a current flowing in layer 114, for example so that the higher the current, the higher the temperature of the heating elements.

[0050] According to one embodiment, the circuit controlling the filter 110, i.e., the temperature of the heating elements, is configured to control the filter based on the value of the pixel output signal (voltage or current). For example, when the pixel output signal exceeds a threshold and approaches a saturation value, the circuit is configured to control the filter 110 so as to reduce the filter's transmission rate.

[0051] According to one embodiment, the filter 110 comprises a thermally conductive layer 116. The layer 116 is disposed on the side of the faces of the motifs 112 which are opposite the faces of the motifs turned towards the layer 114, that is to say on the side of the upper faces of the motifs 112 in the example of [Fig.1] where the lower faces of the motifs 112 are turned towards the layer 114. Thus, in the example [Fig.1], the layer 116 is disposed above the motifs 112.

[0052] Layer 116 is configured to dissipate heat from patterns 112. In other words, layer 116 is a radiator for patterns 112. For example, layer 116 is made of a material transparent to the operating wavelengths of pixel 1. For example, layer 116 is made of a material transparent to the operating wavelengths of filter 110.

[0053] In alternative embodiments, layer 116 may be omitted.

[0054] According to one embodiment, the filter comprises, for each motif 112, a portion of an antireflective coating 118 resting on and in contact with the face of the motif 112 opposite the face of the motif facing the face 102 of the PD element intended to receive light. In other words, the filter comprises, for each motif 112, a portion of an antireflective coating 118 resting on and in contact with the face of the motif 112 intended to receive light. Thus, in the example of [Fig. 1], each motif 112 has its upper face coated by a portion of an antireflective coating 118. By way of example, this portion of the antireflective coating implements an antireflective function within the operating wavelength range of the filter 110.

[0055] By way of example, for each motif 112, the portion of anti-reflective layer 118 which covers the motif 112 has, in planes parallel to the face 102, the same dimensions as those of the motif 112.

[0056] By way of example, in [Fig.1] where layer 114 is arranged between face 102 and patterns 112, and where filter 110 includes layer 116, the latter can be in contact with anti-reflective portions 118.

[0057] Typically, pixel 1 can include other elements based on filter 110, on the side of filter 110 which is intended to receive light.

[0058] For example, as illustrated in [Fig. 1], pixel 1 may include a dielectric layer 120 resting on, and for example in contact with, the face of the filter 110 intended to receive light. In the example of [Fig. 1], this layer 120 rests on and is in contact with layer 116.

[0059] For example, as illustrated in [Fig. 1], pixel 1 may include, in addition to filter 110, a filter 122, for example a filter configured to allow visible light having a wavelength within a given range of visible wavelengths, for example a filter for blue, green, or red visible light. In the example in [Fig. 1], this filter 122, for example made of resin or, for example, an interferometric multilayer filter, rests on layer 120, for example in contact with layer 120.

[0060] For example, as illustrated in [Fig. 1], pixel 1 may include a microlens 124 resting on the side of the filter 110 that is intended to receive light. In the example in [Fig. 1], the microlens 124 rests on, and for example in contact with, the filter 122.

[0061] By way of example, the filter 110 is configured to operate in a wavelength range within the near-infrared (NIR) region, the near-infrared corresponding to a wavelength range from, for example, 700 nm to 1 pm. For example, the filter 110 is configured so that its transmission rate depends on the state of the phase-change material of its motifs 112 in a wavelength range from approximately 920 nm to approximately 945 nm, this range then corresponding to the operating wavelength range of the filter. In this case, the phase-change material is, for example, antimony trisulfide (Sb2S3), the antireflective portions then being, for example, tantalum pentoxide (Ta2O5).

[0062] However, the phase-change material of the patterns 112 and / or the material of the antireflective portions 118 are not limited to the example given above, and a person skilled in the art will be able to adapt these materials according to the operating wavelength range of the filter 110. For example, a person skilled in the art may choose the phase-change material from antimony trisulfide, antimony sulfide, germanium sulfide, or germanium telluride. For example, a person skilled in the art may use other materials for the antireflective portions 118, for example, another tantalum oxide or nitride.

[0063] According to one embodiment, when the filter 110 is configured to operate in a wavelength range belonging to the near-infrared or infrared domain, the filter 110 is further configured so that its rate of visible light transmission of at least 50%, preferably at least 60%, regardless of the phase change material state of the patterns 112.

[0064] According to one embodiment, a method for controlling the filter 110 includes controlling the temperature of the filter's heating elements so as to modify the state of the phase-change material of the filter's motifs 112, i.e., for example, so as to modify the state of the phase-change material between a crystalline state and an amorphous state. This results in a modification of the transmission rate of the filter 110 within its operating wavelength range.

[0065] Figure 2 represents, by way of a schematic perspective view, an example of Detail of the implementation of filter 110 of pixel 1 according to one embodiment. More specifically, [Fig.2] represents a portion of filter 110, layer 116 not being shown and the portion shown in [Fig.2] comprising only one of the patterns 112 of filter 110.

[0066] In this example, the electrically conductive layer 114 comprises openings 200 extending through the entire thickness of the layer 114. The openings are, for example, arranged periodically in two directions orthogonal to each other and parallel to the face 102 of the photosensitive element. By way of example, the openings 200 have, in top view, a substantially circular or oval shape. The openings 200 define portions 202 of the layer 114 that correspond to the heating elements of the filter 110. For example, between every two openings 200, the layer 114 comprises a heating element 202.

[0067] According to one embodiment, a matrix of heating elements 202 is defined in the layer 114, by means of the openings 200.

[0068] In this example, the motif 112 has a cylindrical shape with a circular base. Furthermore, in this example, the motif 112 has a face coated with a portion of an anti-reflective layer 118.

[0069] By way of example, each motif 112 is arranged on a corresponding opening 200. The motif 112 may extend onto the layer 114, and, more particularly, onto one or more heating elements 202. For example, when the layer 114 comprises oval or elliptical openings 200 and each motif 112 is arranged on a corresponding opening 200, the motif 112 may extend onto the layer 114 on either side of the opening 200 taken in its width direction (to the left and right of the opening 200 in [Fig.2]), or, in other words, the motif 112 may extend onto adjacent heating elements 202.

[0070] A person skilled in the art will be able to foresee other ways of implementing the heating elements 202 defined in layer 114. For example, conductive tracks having identical and constant cross-sections may be defined in layer 114, and each conductive track then constitutes a heating element 202.

[0071] Moreover, as previously pointed out, a person skilled in the art will be able to foresee other forms of patterns 112 than that illustrated in [Fig.2].

[0072] The [Fig.3] by curves 300 and 302 the operation of an example embodiment of the filter 110 of pixel 1 of the [Fig.1], when the filter 110 is implemented as illustrated in [Fig.2].

[0073] More specifically, in this example, the filter 110 is configured so that its transmission rate can be controlled in the wavelength range from approximately 920 nm to approximately 945 nm. This wavelength range in which the filter's transmission rate can be controlled by changing the state of the phase-change material of the motifs 112 corresponds to the filter's operating wavelength range.

[0074] In this example: - the phase change material of the motifs 112 is antimony trisulfide (Sb2S3) and the antireflective portions 118 are made of tantalum pentoxide (Ta2O5); - the electrically conductive layer 114 is made of indium tin oxide (ITO from the English 'Indium Tin Oxide'); - filter 110 includes layer 116, and this is made of indium tin oxide; - layer 113 of the filter is made of silicon oxide; - the thickness (or height) of each motif 112 is 180 nm; - the repetition period of the motifs 112, in the first and second directions orthogonal to each other and parallel to the face 102, is 570 nm; and - the radius of the circular base of the motifs 112 is equal to 130 nm.

[0075] Curve 300, respectively 302, illustrates the normalized transmission rate T of the filter 110 as a function of wavelength (in pm) when the phase change material is crystalline, respectively amorphous.

[0076] These curves show that the filter 110 has, in its operating wavelength range, a transmission rate greater than 0.90 when the phase change material is amorphous (curve 302) and a transmission rate less than 0.05 when the phase change material is crystalline.

[0077] Although a pixel 1 with back-facing illumination has been described in relation to Figures 1 to 3 in which the filter 110 is disposed on the side of the back face of the pixel 1, that is to say on the side of the back face 102 of the substrate 100, a person skilled in the art will be able to adapt the pixel 1 to front-facing illumination, the filter 110 then being disposed on the side of the front face of the pixel 1, that is to say on the side of the front face 104 of the substrate, for example on the interconnection structure 106 which will then be disposed between the filter 110 and the substrate 100.

[0078] Furthermore, a person skilled in the art will be able to adapt the above description of pixel 1 in the case where pixel 1 comprises only one filter 110, to the case where pixel 1 comprises a stack of filters 110, for example, two filters 110, each configured to have a controllable transmission rate in different wavelength ranges. Indeed, the provision of several stacked filters 110 with different operating wavelength ranges makes it possible to implement optical logic functions between the operating wavelength ranges of these stacked filters.

[0079] Furthermore, although examples have been described where the state of the phase-change material is either crystalline or amorphous, a person skilled in the art will be able to foresee a control of the filter 110 allowing the phase-change material to be, in addition to the two states mentioned above, in one or more intermediate states between the crystalline state and the amorphous state, each intermediate state then corresponding to a transmission rate having an intermediate value between maximum and minimum values ​​corresponding to the crystalline and amorphous states.

[0080] Although only one pixel 1 has been described above, according to one embodiment a light sensor, for example an image sensor, comprising a plurality of pixels 1, for example arranged in a matrix of pixels 1, is provided. In such a sensor, a control circuit for the filters 110 of the pixels 1 is provided.

[0081] Fig. 4 represents schematically and in block form an example of a 400 sensor comprising a plurality of pixels 1.

[0082] The 400 sensor comprises a plurality of pixels 1, only one pixel 1 being represented and referenced in [Fig.4] so as not to clutter the figure. In the example of the 400 sensor in [Fig.4], the pixels 1 are arranged in a 408 matrix of pixels 1, the 408 matrix comprising rows and columns of pixels 1.

[0083] The sensor 400 further includes a pixel control circuit 404, for example a circuit 404 configured to control the pixel lines 1. For example, the circuit 404 is configured to control a reading of the pixel lines one after the other, all the pixels of a line being read simultaneously.

[0084] The sensor 400 further includes a pixel reading circuit 402. For example, the circuit 402 is configured to receive the output signals from the pixels 1 being read, for example the output signals from all the pixels of a line being read.

[0085] By way of example, the sensor 400 includes a processing circuit 410. The circuit 410 receives signals from the circuit 402, these signals corresponding to the output values ​​of the read pixels. For example, the circuit 402 is configured to implement an analog-to-digital conversion of the output signals of pixels and / or doubles correlated sampling etc., and to provide the resulting signals to circuit 410. Circuit 410 is, for example, configured to reconstruct an image of a scene captured by sensor 400, from the signals it receives from circuit 402.

[0086] By way of example, the sensor 400 may include a circuit 406 allowing the synchronization of circuits 406 and 402.

[0087] The implementation of a sensor comprising a plurality of pixels 1 is not limited to the example described above in relation to [Fig.4].

[0088] Although the pixel 1 described above has been presented as a high dynamic range pixel, the pixel 1 including the filter comprising filter 110 can also be used in other contexts, taking advantage of the benefits provided by filter 110. For example, pixel 1 can be used as a pixel in a time-of-flight (ToF) sensor, for example, a direct time-of-flight (dToF) sensor or an indirect time-of-flight (iToF) sensor. Furthermore, although not specified so far, the photoconversion element PD of pixel 1 can be, for example, a conventional photodiode, a pinned photodiode, a single-photon avalanche diode (SPAD), or any other photoconversion element commonly used in a pixel.For example, the PD element can be a SPAD in the case where pixel 1 is used in a ToF sensor.

[0089] Furthermore, one or more pixels 1 can be used in various fields and applications.

[0090] For example, one or more pixels 1 can be used in electronic systems embedded in vehicles. For example, a sensor comprising one or more pixels 1 can be designed to implement radar functions, for example, to obtain distance maps between the vehicle and surrounding elements. For example, a sensor comprising one or more pixels 1 can be designed to obtain images of the vehicle's environment or the interior of the vehicle's passenger compartment. For example, a sensor comprising one or more pixels 1 can be used to provide input data to driver assistance systems or autonomous driving systems.

[0091] By way of further examples, one or more pixels 1 may be provided in personal electronic systems such as, for example, mobile phones or Internet of Things (IoT) devices. For example, an image sensor comprising one or more pixels 1 may be provided in a mobile phone, for example in the phone's camera or in the phone's facial recognition device. For example, an image sensor comprising one or more pixels 1 may be provided in an IoT device to put implementing the device's environment depth mapping functionalities or detecting the presence of an object in the sensor's field.

[0092] By way of further examples, one or more pixels 1 may be provided in electronic systems embedded in industrial devices. For example, an image sensor comprising one or more pixels 1 may be provided in a robot to provide three-dimensional and / or two-dimensional images enabling the robot to understand its environment in order to perform a specific function.

[0093] By way of further examples, one or more pixels 1 may be provided in autonomous robotic systems. For example, an image sensor comprising one or more pixels 1 may be provided in an autonomous robot, for example an industrial or domestic vacuum cleaner robot, to provide three-dimensional and / or two-dimensional images enabling the robot to know its environment in order to perform a specific function.

[0094] Various embodiments and variations have been described. A person skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will become apparent to a person skilled in the art.

[0095] Finally, the practical implementation of the embodiments and variants described is within the reach of a person skilled in the art, based on the functional indications given above.

Claims

Demands

1. Pixel (1) comprising: a photosensitive element (PD); a filter (110) above a face (102) of the photosensitive element intended to receive light, the filter comprising: - a plurality of identical patterns (112) in a phase-change material, and - a plurality of heating elements (202) defined in an electrically conductive layer (114) of the filter, the electrically conductive layer being parallel to said face (102) intended to receive light and the heating elements (202) being configured so that a temperature of the heating elements determines a temperature of the phase-change material of the patterns; and a circuit configured to control the temperature of the heating elements.

2. Pixel according to claim 1, wherein the filter (110) is configured such that a filter transmission rate for light in a range of operating wavelengths depends on a phase-change material state.

3. Pixel according to claim 1 or 2, wherein the patterns (112) are arranged periodically.

4. Pixel according to any one of claims 1 to 3, wherein each pattern (112) comprises two faces parallel to each other and to the electrically conductive layer (114), the pattern extending from one to the other of said two faces and having a first of said two faces which is turned towards the electrically conductive layer (114).

5. Pixel according to claim 4, wherein the filter comprises, for each pattern (112), a portion of anti-reflective layer (118) resting on and in contact with that of said two faces of the pattern (112) which is intended to receive light.

6. Pixel according to claim 5, wherein: the antireflective layer (118) is tantalum nitride or oxide, for example tantalum pentoxide, and the phase-change material (112) is antimony trisulfide, antimony sulfide, germanium sulfide or germanium telluride.

7. Pixel according to any one of claims 4 to 6, wherein the filter (110) further comprises, on the side of the second faces of the patterns (112), a thermally conductive layer (116).

8. Pixel according to claim 7, wherein the thermally conductive layer (116) is made of a material transparent at pixel operating wavelengths, for example in indium tin oxide.

9. Pixel according to any one of claims 1 to 8, wherein the electrically conductive layer (114) is made of a material transparent at pixel operating wavelengths, for example in indium tin oxide.

10. Light sensor (400) comprising a plurality of pixels (1) according to any one of claims 1 to 9.

11. Method comprising: controlling, in a pixel (1) comprising a photosensitive element (PD) and a filter (110) above a face (102) of the photosensitive element intended to receive light, with a circuit of the pixel (1), a temperature of a plurality of heating elements (202) defined in a layer (114) of the filter (11) which is electrically conductive and parallel to said face intended to receive light, so as to change a state of a plurality of identical patterns (112) into a phase-change material.

Images