Light-receiving element and distance measuring device

Abstract

To provide a light-receiving element that can suppress the influence of light outside the measurement target with a simple configuration. [Solution] The photodetector has a photodetector array in which multiple photodetectors are arranged in two dimensions. The photodetector measures the elapsed time from a reference time until the incidence of light on the multiple photodetectors is detected, and determines the final elapsed time based on the multiple measured elapsed times. Each of the multiple photodetectors has multiple photoelectric conversion elements having adjacent photoelectric conversion regions, and an insensitive region to incident light provided between adjacent photodetectors.

Description

[Technical Field]

[0001] This invention relates to a light-receiving element and a distance measuring device. [Background technology]

[0002] A distance measurement method called the Time-of-Flight (TOF) method is known, which measures the distance to an object that reflects light based on the time (TOF) from the time light is shone on the object until the reflected light is detected.

[0003] To accurately measure distance using the TOF method, it is crucial to correctly detect the reflected light from the irradiated light. For example, in Patent Document 1, an aperture is placed in front of the light-receiving element to suppress the incidence of ambient light and other light unrelated to the measurement target onto the light-receiving element. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-215324 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, when an aperture is used, precise alignment with the photodetector is necessary. This alignment is particularly difficult when multiple photodetectors are used. Furthermore, a configuration with an aperture is disadvantageous in terms of miniaturization and cost.

[0006] In light of the limitations of the conventional technology, the present invention, in one embodiment, provides a light-receiving element and a distance measuring device that can suppress the influence of light outside the measurement target with a simple configuration. [Means for solving the problem]

[0007] In one embodiment, the present invention provides a light-receiving element comprising: a light-receiving element array in which a plurality of light-receiving elements are arranged in two dimensions; a measuring means for measuring the elapsed time from a reference time until the incidence of light on the plurality of light-receiving elements is detected; and a determining means for determining the final elapsed time based on the measured plurality of elapsed times, wherein each of the plurality of light-receiving elements comprises a plurality of photoelectric conversion elements having adjacent photoelectric conversion regions, and an insensitive region to incident light provided between adjacent light-receiving elements. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a light-receiving element and a distance measuring device that can suppress the influence of light other than the object being measured with a simple configuration. [Brief explanation of the drawing]

[0009] [Figure 1] Block diagram showing an example of the functional configuration of a distance measuring device according to an embodiment. [Figure 2] Schematic diagram of an example configuration of the light-emitting unit shown in Figure 1. [Figure 3] Schematic diagram of an example configuration of the measurement unit shown in Figure 1. [Figure 4] Equivalent circuit diagram of pixels in the photodetector array according to the embodiment [Figure 5] (A) is a diagram showing an example of the arrangement of subpixels on the light-receiving surface of a pixel, and (B) is a diagram showing an example of the configuration of microlenses corresponding to pixels. [Figure 6] Cross-sectional view at line A-A' in Figure 3. [Figure 7] A diagram illustrating the conjugate relationship between the light-emitting element array and the light-receiving element array in the distance measuring device according to this embodiment. [Figure 8] (A) is a schematic diagram showing light rays near the light-emitting element, and (B) is a schematic diagram showing light rays near the pixel. [Figure 9] This diagram illustrates the relationship between the image formed on an object and the position where the reflected light from the image enters the photodetector array. [Figure 10] A figure showing an example of sub-pixel arrangement in a pixel according to a modified embodiment. [Figure 11] Cross-sectional view taken along line A-A' of FIG. 10 [Figure 12] (A) is a diagram for explaining the relationship between an image formed on an object and the position where the reflected light of the image enters the light receiving element array in a modified example, and (B) is a diagram for explaining an example of a sub-pixel to be invalidated in the modified example

Mode for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in detail based on its exemplary embodiments with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Also, although a plurality of features are described in the embodiments, not all of them are essential for the invention, and the plurality of features may be arbitrarily combined. Furthermore, in the accompanying drawings, the same or similar components are denoted by the same reference numerals, and duplicate explanations are omitted.

[0011] (Overall Configuration of the Distance Measuring Device)

[0012] FIG. 1 is a block diagram showing a functional configuration example of a distance measuring device according to an embodiment. The distance measuring device 100 includes a light emitting unit 110, a measurement unit 120, an image side telecentric lens 130, an overall control unit 140, and a beam splitter 150.

[0013] The light emitting unit 110 includes a light source unit 113 and a light source control unit 114. The light source unit 113 includes a light emitting element array 111 in which a plurality of light emitting elements are arranged in a two-dimensional array, and a light emitting element driving unit 112.

[0014] The measurement unit 120 includes a light receiving element array 121 in which a plurality of light receiving elements are arranged in a two-dimensional array, a TDC (Time-to-Digital Convertor) array unit 122, a signal processing unit 123, a measurement control unit 124, and a row selection circuit 125. [[ID=3']]

[0015] The beam splitter 150 has a half mirror 151 that transmits a portion of the incident light and reflects a portion of it. The beam splitter 150 is arranged such that the half mirror 151 reflects light from the light-emitting element array 111 towards the image-side telecentric lens 130 and transmits light from the image-side telecentric lens 130 to the photodetector array 121.

[0016] The optical bandpass filter 160 is positioned between the beam splitter 150 and the photodetector array 121, allowing light of a predetermined wavelength band, including the wavelength of light emitted by the light-emitting element array 111, to pass through, while reflecting or absorbing light of other wavelengths.

[0017] When the light-emitting element array 111 in the light source unit 113 emits light, the emitted light is incident on the half mirror 151 of the beam splitter 150. The light reflected by the half mirror 151 is projected into the outside space via the image-side telecentric lens 130.

[0018] Light projected into the external space is partially reflected when it reaches an object in the external space. A portion of the reflected light then enters the image-side telecentric lens 130. The image-side telecentric lens 130 converts the light incident from the external space into rays parallel to the optical axis and outputs them to the beam splitter 150. The half-mirror 151 of the beam splitter 150 transmits a portion of the light incident through the image-side telecentric lens 130. The transmitted light enters the photodetector array 121 via the optical bandpass filter 160.

[0019] The TDC array unit 122 measures the time (TOF) from when the light-emitting element array 111 emits light until the reflected light is detected by the photodetector array 121. The TDC array unit 122 measures the TOF for each photodetector included in the photodetector array 121. In addition, during distance measurement, the light-emitting element array 111 is made to emit light multiple times, and the TOF is measured for each emission.

[0020] The signal processing unit 123 statistically processes the TOF measured for each emission and for each photodetector to suppress the influence of noise components such as ambient light and dark count included in the measured values, as well as the influence of noise from measurement circuits such as the TDC array unit 122, and determine the final TOF. For example, the signal processing unit 123 can generate a TOF histogram and determine the TOF value based on the frequency distribution, thereby determining a TOF that suppresses the influence of ambient light and noise.

[0021] The TOF determined by the signal processing unit 123 is output to the overall control unit 140 via the measurement control unit 124. The overall control unit 140 can calculate the distance L between the distance measuring device 100 and the object that reflected the light by substituting the TOF obtained from the measurement unit 120 into the following equation (1). In equation (1), c is the speed of light. Alternatively, the measurement control unit 124 may calculate the distance L. L = TOF × c / 2 ... (1)

[0022] (Light-emitting unit) An example of the configuration of the light-emitting unit 110 will be further explained with reference to Figure 2. Figure 2 is a schematic diagram showing an example of the configuration of the light-emitting unit 110, with particular attention paid to the configuration of the light-emitting element array 111.

[0023] The light-emitting element array 111 has a plurality of light-emitting elements 201 arranged in a two-dimensional array on a substrate. The light-emitting elements 201 may be, for example, vertical cavity surface-emitting laser (VCSEL) elements. The light-emitting elements 201 may also be other light-emitting elements such as end-face-emitting laser elements or LEDs (light-emitting diodes). The plurality of light-emitting elements 201 constituting the light-emitting element array 111 may be arranged on multiple substrates. The light-emitting element array 111 may be, for example, a configuration in which multiple substrates (laser bars) in which the plurality of light-emitting elements 201 are arranged in one dimension are lined up (laser bar stack), or a configuration in which the plurality of light-emitting elements 201 are arranged two-dimensionally on a single substrate.

[0024] The emission wavelengths of multiple light-emitting elements 201 may be the same. In this embodiment, as an example, it is assumed that multiple light-emitting elements 201 have the same wavelength within the near-infrared band. However, in reality, there may be variations in wavelength due to manufacturing errors, tolerances, etc.

[0025] When a VCSEL element is used as the light-emitting element 201, for example, by using a GaAs-based material, an emission wavelength in the near-infrared region can be achieved. In this case, the dielectric multilayer film that forms the DBR (distributed reflection) mirror constituting the VCSEL can be constructed by alternately and periodically stacking two thin films made of materials with different refractive indices (GaAs / AlGaAs).

[0026] Furthermore, multiple VCSEL elements arranged in a one-dimensional array in the row direction have a common anode electrode in addition to their individual cathode electrodes, and these electrodes are connected to the corresponding drive circuits 202. By operating only a specific drive circuit 202 of the light-emitting element drive unit 112, only the VCSEL elements located in the corresponding specific row can be made to emit light.

[0027] The light-emitting element array 111 further includes a microlens array 220. The microlens array 220 has a configuration in which multiple microlenses 221, each corresponding to one light-emitting element 201, are arranged in a two-times configuration. Each microlens 221 focuses the light emitted by the corresponding light-emitting element 201. In this embodiment, the microlenses 221 constituting the microlens array 220 are arranged in a one-to-one correspondence with each light-emitting element 201.

[0028] (Measurement unit) Figure 3 is a schematic diagram showing an example configuration of the measurement unit 120, with particular attention paid to the configuration of the light-receiving element array 121. The light-receiving element array 121 has a configuration in which pixels 301, which act as light-receiving elements, are arranged in two dimensions. As will be described later, each pixel 301 has a photoelectric conversion region that is divided into multiple parts. It should be noted that the term "pixel" in this embodiment is a convenient designation and differs from pixels in a typical image sensor. The pixels 301 in this embodiment are used to detect the incidence of light and do not output a signal corresponding to the amount of light received during the exposure period. Each pixel 301 is connected to one row selection signal line 303 and one output line 304.

[0029] The row selection circuit 125 has multiple row selection signal lines 303 for selecting multiple pixels 301 arranged two-dimensionally in the photodetector array 121 on a row-by-row basis. Similarly, the TDC array unit 122 has multiple output lines 304 provided for each column of multiple pixels 301 arranged two-dimensionally in the photodetector array 121. For the pixel row selected by the row selection circuit 125, the TDC array unit 122 can read the output from the pixels 301 of the selected row by sequentially scanning the multiple output lines 304.

[0030] Figure 4 is a circuit diagram showing an example configuration of a pixel 301. Pixel 301 has four SPADs (Single Photon Avalanche Diodes) 401, which are photoelectric conversion elements, four load transistors 402, four inverters 403, an output circuit 404, a row selection pulse line 303, and an output line 304. In the following description, a combination of interconnected SPADs 401, load transistors 402, and inverters 403 will be referred to as a sub-pixel 405. Each sub-pixel 405 has its own photoelectric conversion region and can independently detect incident light.

[0031] The reason for dividing a single pixel 301 into multiple sub-pixels 405 is that if two or more photons are incident on the same photoelectric conversion region during the measurement period, the Time of Flight (TOF) cannot be measured accurately. By dividing a single pixel 301 into multiple sub-pixels 405, that is, by dividing the photoelectric conversion region into multiple parts, the probability of multiple photons being incident on the same photoelectric conversion region during the measurement period can be reduced. In addition, since TOF can be measured for each sub-pixel, the number of measurement samples per pixel 301 can be increased, which is advantageous in statistical processing to suppress the effects of ambient light and other factors.

[0032] Furthermore, as will be described later, the individual light-emitting elements 201 arranged in the light-emitting element array 111 and the individual pixels 301 arranged in the light-receiving element array 121 are arranged in a conjugate relationship. Therefore, when light emitted from a light-emitting element 201 is specularly reflected by an object, it is incident on the center of the corresponding pixel 301. For this reason, the sub-pixels 405 are arranged so that their photoelectric conversion regions receive light incident on the center and surrounding area of ​​the pixel 301. As will be described in detail later, multiple sub-pixels are arranged so that the center of the photoelectric conversion region of the entire sub-pixel is equal to the center of the pixel 301.

[0033] As will be described later using Figure 6, SPAD401 has a light-receiving region (photoelectric conversion region) 621 and an avalanche region 622. When light (photons) is incident on SPAD401, it is photoelectrically converted in the light-receiving region 621, generating electrons and holes. Positively charged holes are discharged through the anode electrode Vbd. Negatively charged electrons (signal charges) move through the light-receiving region 621 toward the avalanche region 622 due to an electric field set so that the potential decreases toward the avalanche region 622. When the signal charges reach the avalanche region 622, the strong electric field of the avalanche region 622 induces avalanche breakdown, generating an avalanche current.

[0034] When no avalanche current is generated, the voltage of the anode electrode Vbd is set so that a reverse bias greater than or equal to the breakdown voltage is applied to the avalanche region 622 of SPAD401. At this time, no current flows through the load transistor 402, so the cathode potential Vc of SPAD401 is close to the power supply voltage Vdd, and the output signal of inverter 403 is "0".

[0035] When an avalanche current is generated, the cathode potential Vc of SPAD401 drops, and the output of inverter 403 changes from "0" to "1". As the cathode potential Vc of SPAD401 decreases, the reverse bias applied to SPAD401 decreases, and when the reverse bias falls below the breakdown voltage, no avalanche current is generated. Hereafter, the operation that returns to a state where no avalanche current is generated will be referred to as the quench operation.

[0036] Subsequently, when the load transistor 402 conducts and a hole current flows from Vdd to the cathode of SPAD401, the cathode potential Vc of SPAD401 rises, the output of inverter 403 returns from "1" to "0", and the system returns to the state before the photon incident. In this way, the output of SPAD401 changes temporarily with each photon incident.

[0037] Pixels 301 selected by row selection signal line 303 (where the potential of the connected row selection signal line 303 is at the "on" level) are controlled so that the output of inverter 403 is output to output line 304. On the other hand, pixels 301 not selected by row selection signal line 303 (where the potential of the connected row selection signal line 303 is at the "off" level) are controlled so that the output of inverter 403 is disconnected from output line 304. As a result, the row selection circuit 125 can detect only the light incident on pixels 301 belonging to a specific row selected by row selection signal line 303. Therefore, the output of pixels 301 belonging to the row selected by row selection circuit 125 is output to the TDC array unit 122 as a low-latency digital signal.

[0038] The TDC array unit 122 is provided with one TDC for each row, and measures the elapsed time (TOF) from the emission time (reference time) of the light-emitting unit 110 until a signal is detected at the pixel 301, based on the output of the corresponding pixel 301. The TOF measured for each pixel 301 by the TDC array unit 122 is transmitted to the signal processing unit 123. The reference time is notified to the measurement unit 120 from, for example, the overall control unit 140 or the light-emitting unit 110 for each emission timing of the light-emitting unit 110. Alternatively, the light-emitting unit 110 and the measurement unit 120 may be synchronized based on the same clock, and a predetermined emission timing may be used as the reference time.

[0039] For example, the signal processing unit 123 determines one TOF from the TOF detected by sequentially selecting one row at a time for each pixel 301 included in the light-receiving element array 121, as described above. The determined TOF is substituted into equation (1) by the measurement control unit 124 or the overall control unit 140 and converted into distance information.

[0040] Figure 5(A) schematically shows the configuration of the light-receiving surface of a 2x2 pixel 301 among the multiple pixels 301 included in the light-receiving element array 121. Figure 5(B) is a top view showing an example of the configuration of microlenses provided on the light-receiving surface of the pixel 301. Figure 6 schematically shows the A-A' cross section of Figure 5. For convenience, reference numbers are only added to the leftmost pixels in Figure 6.

[0041] In this embodiment, the pixel 301 is formed across both the photodetector substrate 600 and the logic substrate laminated on the photodetector substrate 600, and is configured to receive light from the side opposite to the wiring layer. In other words, the photodetector array 121 has a so-called back-illuminated configuration. The photodetector substrate 600 is a semiconductor substrate made of silicon (Si), for example, and has an optical layer 610, a semiconductor layer 620, and a wiring layer 630. The logic substrate laminated below the photodetector substrate 600 has a wiring layer 640 and a semiconductor layer (not shown).

[0042] In Figure 5, the insensitive region 501 is a region configured by the microlens 612 and the light-shielding layer 611 to have no sensitivity to incident light. Having no sensitivity to incident light means that even if light is incident on the insensitive region 501, no charge is generated, or even if a charge is generated, the charge does not flow into the subpixel. The light-shielding layer 611 is not essential, but by providing it, the sensitivity of the insensitive region 501 to incident light can be more reliably eliminated. Here, the insensitive region 501 is provided to surround a square region along the outer edge of the light-receiving region 621 of the subpixel, but it may be provided to surround a region of other shapes, such as a circle, depending on the outer edge shape of the light-receiving region 621 of the subpixel.

[0043] Furthermore, although the light-shielding layer 611 is formed along the outer edge of the light-receiving area 621 of the subpixel, it may also be provided so as to cover a part of the light-receiving area 621 from the outside in order to reduce the effective light-receiving area 621 of the subpixel. This makes it possible to suppress the number of photons incident on the subpixel.

[0044] There are no dead zones between the light-receiving regions 621 of the four subpixels (SPAD401) formed in each of the pixels 301. The subpixels are arranged in a vertical and horizontal arrangement of two in the center of the pixel 301. The four light-receiving regions 621 provided in the same pixel 301 are separated by a separation region 623. The separation region 623 is formed of a semiconductor into which impurities have been implanted so that its potential is higher than that of the light-receiving region 621. By separating the light-receiving regions 621 of adjacent subpixels with a PN junction (separation region 623) that forms a potential barrier, the charge generated by light incident on the separation region 623 is detected in one of the subpixels adjacent to the separation region 623. Furthermore, since the light-receiving region 621 of the subpixels is a division of the light-receiving region of the pixel 301, the overall center of the light-receiving region 621 of the subpixels is equal to the center 330 of the pixel 301.

[0045] Furthermore, in the example shown in Figure 6, the insensitive region 501 has a light-receiving region. However, a charge discharge region 626 is provided so that the charge generated by the light incident on the insensitive region 501 is discharged without being detected by the subpixel. Even when light passes through the light-shielding layer 611 and is incident on the semiconductor region 620 of the photodetector substrate 600, the charge converted photoelectrically within the charge discharge region 626 is discharged and not detected by the subpixel. The same is true even when there is no light-shielding layer 611.

[0046] Furthermore, an insulating region 625 is positioned between the light-receiving region 621 and the charge-discharging region 626 to suppress the movement of charge between the light-receiving region 621 and the charge-discharging region 626. The insulating region 625 is composed of, for example, SiO and is called Deep Trench Isoration (DTI). In addition, a region 624 is provided between the light-receiving region 621 and the insulating region 625, in which impurities are implanted to create a high potential and many holes, thereby suppressing dark counts caused by the interface between the insulating region 625 and the light-receiving region 621.

[0047] Each subpixel has a load transistor 402, inverter 403, and output circuit 404, which are located in the semiconductor region (not shown) of the logic board, and the row selection signal line 303 and output line 304 are located in the wiring layer 640 of the logic board.

[0048] The microlenses 612 that constitute the microlens array provided in the optical layer 610 have a configuration in which microlenses for each subpixel with the same curvature are combined. Specifically, as shown in Figure 5(B), for a pixel 301 having four subpixels 401, the optical axis centers of the four microlenses 612 are combined in an arrangement such that they are eccentric toward the center 330 of the pixel 301 (or the center of the photoelectric conversion region of the entire subpixel 401).

[0049] By configuring the microlenses 612 corresponding to each individual pixel in this way, it becomes possible to reliably detect light incident on the center of the pixel 301 in one of the subpixels. Furthermore, the curvature of the microlenses 612 can be reduced while suppressing its height. However, the microlenses 612 may have other configurations. Due to the image-side telecentric lens 130, light parallel to the optical axis is incident on the microlenses 612. The light focused by the microlenses 612 is then incident on the center 330 of the pixel 301 or its vicinity, among the four light-receiving regions 621. Therefore, the time it takes for the charge generated by photoelectric conversion in the subpixels 401 to reach the avalanche region 622 becomes approximately equal among the subpixels 401, reducing measurement time errors.

[0050] Furthermore, in the microlens array, the microlens 612 is configured such that its outer edge 627 does not extend beyond the outer edge of the light-receiving area 621 of the subpixel. This is to prevent light that should not be incident on the subpixel from being incident on by the microlens 612. Also, in the microlens array, the portion 628 where the microlens 612 is not provided is configured to be flat.

[0051] (Relationship between light projection and light reception) The process from when the light emitted from the light-emitting element array 111 is projected to the outside by the image-side telecentric lens 130, until the reflected light reaches the photodetector array 121, will be explained using Figures 7 to 9.

[0052] Figure 7 is a schematic diagram showing the relationship between light emission and light reception in the distance measuring device 100. The light-emitting element array 111 and the light-receiving element array 121 are conjugate via the half-mirror 151 of the beam splitter 150, and the individual light-emitting elements 201 and individual pixels 301 are also conjugate. Note that in Figure 7, the number of rows in the light-emitting element array 111 and the light-receiving element array 121 is set to 8, but this is merely an example.

[0053] The row numbers of the light-emitting element array 111 are assigned starting with row 1, which has the smallest Yv value in the XvYvZv coordinate system shown in Figure 7, and increasing by 1 each time. Similarly, the row numbers of the light-receiving element array 121 are assigned starting with row 1, which has the smallest Y value in the XYZ coordinate system shown in Figure 7, and increasing by 1 each time. The light-emitting elements 201 and pixels 301 belonging to the same row number are arranged to have a conjugate relationship.

[0054] In Figure 7, as an example, the conjugate relationship between row number 1 and row number 2 of the light-emitting element array 111 and the photodetector array 121 is shown by optical paths 701 and 702. 701 is the optical path of the light emitted from the light-emitting element 201 belonging to row number 1, and 702 is the optical path of the light emitted from the light-emitting element 201 belonging to row number 1.

[0055] The light emitted from the light-emitting element 201 belonging to row number 1 is projected into the outside space via the beam splitter 150 and the image-side telecentric lens 130. Of the light reflected by objects in the outside space, the light with an angle close to specular reflection is incident on the image-side telecentric lens 130 and, via the beam splitter 150, is incident on the pixel 301 belonging to row number 1 of the photodetector array 121. Similarly, the light emitted from the light-emitting element 201 belonging to row number 2 is incident on the pixel 301 belonging to row number 2 of the photodetector array 121.

[0056] Figure 8(A) is a schematic diagram illustrating the light rays near the light-emitting element 201 in Figure 7, and Figure 8(B) is a schematic diagram illustrating the light rays near the pixel 301 in Figure 7. The position of the photodetector array 121 in the Z-axis direction is determined such that the microlens 612 is positioned at position 801 where parallel light rays incident on the afocal system, which is composed of the microlens array 220 and the image-side telecentric lens 130, converge. Position 801 is determined from the focal lengths of the microlens 221 and the image-side telecentric lens 130.

[0057] In Figure 8(A), ray 811 is a ray emitted from the light-emitting element 201, and in Figure 8(B), ray 812 is a ray that has been reflected back by an object in the external space after ray 811 was reflected.

[0058] Figure 9 schematically shows the relationship between the position of light projected by the image-side telecentric lens 130 onto an object in the external space and the position of reflected light incident on the photodetector array 121. Here, nine pixels of the photodetector array 121, consisting of three horizontal and three vertical pixels, are shown.

[0059] The region 902 on the object is approximately proportional to the light-receiving region of the pixel 301 of the light-receiving element array 121. Since the microlens array 220 of the light-emitting element array 111 and the image-side telecentric lens 130 constitute an afocal system, the size d of the image formed on the object by light emitted from one light-emitting element 201 is approximately proportional to the light-receiving region 902 on the object. b This is expressed by the following equation (2). d b =( pf L ) / f M ...(2) Here, p is the light-emitting diameter of the light-emitting element 201, f M The focal length of the microlens 221 is f L This is the focal length of the image-side telecentric lens 130.

[0060] If there is no object at close range that reflects the light projected from the rangefinder, the light emitted by each light-emitting element 201 will form an image on the object at spaced-out positions, and the size of the image will be smaller than the light-receiving area of ​​the pixel 301.

[0061] In addition to the light projected from the rangefinder 100, ambient light such as light from other light sources in the external space and reflected light from surrounding objects may be projected onto the object. By selecting the emission wavelength of the light-emitting element 201 to be different from the wavelength of general ambient light, much of the ambient light that directly or indirectly enters the image-side telecentric lens 130 is removed by the optical bandpass filter 160.

[0062] However, ambient light incident on the image-side telecentric lens 130 that has a wavelength equal to or close to the emission wavelength of the light-emitting element 201 cannot be removed by the optical bandpass filter 160 and therefore enters the photodetector array 121.

[0063] In this embodiment, for multiple pixels 301 arranged two-dimensionally in the photodetector array 121, the light-receiving area is limited to the vicinity of the center of the pixel, and a dead zone 501 is provided between adjacent pixels. Therefore, light reflected at positions 903 and 904 on the object corresponding to the dead zone 501 in the photodetector array 121 (corresponding to the light ray 813 in Figure 8(B)) is not detected by the sub-pixels. It is reflected and absorbed by the light-shielding curtain 611 or converted into photoelectric light in the charge discharge region 626, and does not affect the TOF measurement.

[0064] Thus, according to this embodiment, ambient light having a wavelength similar to the emission wavelength can be suppressed by the insensitive region 501. Therefore, TOF measurement with suppressed ambient light influence can be achieved without using separate components as in the conventional technology.

[0065] (modified version) In the first embodiment, a dead zone was created by physically limiting the light-receiving area of ​​a pixel. However, a dead zone can also be realized by other methods. As an example of such a modification, this section describes a configuration in which a portion of the light-receiving area is effectively made a dead zone by disabling (not using for TOF measurement) a portion of the subpixels. The following section will focus on explaining the differences from the first embodiment.

[0066] Figure 10 is a schematic diagram showing the light-receiving area of ​​a 2x2 pixel 301 provided on the light-receiving element array 121. Figure 11 is a schematic diagram showing the B-B' cross section of Figure 10.

[0067] In the first embodiment, a subpixel (photoelectric conversion region) was provided at the center of the light-receiving surface of each pixel, and the remainder was a dead region. In this modified example, subpixels are arranged across the entire light-receiving surface of each pixel. In Figure 10, the boundaries of pixels 301 are shown with solid lines, and the boundaries between subpixels (photoelectric conversion regions) are shown with dashed lines. As shown in Figure 11, subpixels are provided in place of the charge discharge region of the first embodiment. Although a typical example is shown here in which subpixels are provided across the entire light-receiving surface of the pixel, a smaller dead region than in the first embodiment may also exist.

[0068] In this modification example, a substantial insensitive region is formed by invalidating a part of the sub-pixels. The invalidation of the sub-pixels can be realized by various methods. For example, the anode voltage Vbd is configured to be supplied to each sub-pixel via a separate wiring, and a reverse bias below the breakdown voltage is applied to the anode electrode of the sub-pixel to be invalidated. Thereby, avalanche amplification does not occur in the sub-pixel. Alternatively, for the sub-pixels to be invalidated, the signal may simply not be read out, or the TOF may not be measured.

[0069] For example, if only the sub-pixels in the central portion of the pixel are made effective, the same effects as those of the first embodiment can be obtained. Further, as an effect peculiar to the modification example, there is a point that it is possible to cope with a shift that has occurred in the conjugate relationship between the light-emitting element array 111 and the light-receiving element array 121 due to causes such as manufacturing errors and changes over time.

[0070] FIG. 12(A) is a diagram schematically showing the position of the image formed by the emitted light of the light-emitting element 201 on the object in association with the light-receiving region of the sub-pixels provided in the light-receiving element array 121, similar to FIG. 9. FIG. 12 shows that due to a shift in the conjugate relationship between the light-emitting element array 111 and the light-receiving element array 121, the imaging position of the image 901 on the object is in the +X O direction and +Y O direction.

[0071] As shown in FIG. 7, the coordinates (X O , Y O ) on the object correspond to the coordinates (X, Y) on the light-receiving element array 121. Therefore, the reflected light of the image 901 is incident at a position shifted in the +X direction and +Y direction from the center 330 of the pixel, as indicated by 901' in FIG. 12(B).

[0072] In such cases, the detection of unwanted incident light can be suppressed by disabling the hatched sub-pixels in Figure 12(B) that are not included in a predetermined size (here, the size of two horizontal and vertical pixels) that includes the incident position 901'. Thus, according to this modification, the position of the effective light-receiving area can be dynamically changed according to the position where the light emitted from the light-emitting element 201 is reflected by an object and incident on a pixel of the light-receiving element array. Therefore, the required precision for the installation positions of the light-emitting element array 111 and the light-receiving element array 121 can be lowered compared to the first embodiment, which is advantageous from a manufacturing standpoint.

[0073] (Other embodiments) For example, in the pixel configuration shown in Figure 10, a light-shielding curtain may be provided in the portion of the pixel excluding the area near the center to achieve a configuration similar to that of the first embodiment.

[0074] Furthermore, although the above-described embodiment described a configuration using SPAD as the photoelectric conversion element, a general combination of photodiode and amplifier may also be used. However, since the time required for charge amplification in SPAD is much faster than when the charge multiplication of a general photodiode signal is performed using an analog circuit, using SPAD is advantageous in terms of TOF measurement accuracy.

[0075] This embodiment includes the following light-receiving element and distance measuring device. (Item 1) A photodetector array in which multiple photodetectors are arranged in two dimensions, A measuring means for measuring the elapsed time from a reference time until the incidence of light on the plurality of light-receiving elements is detected, It has a determination means for determining the final elapsed time based on multiple measured elapsed times, Each of the aforementioned multiple light-receiving elements is Multiple photoelectric conversion elements having adjacent photoelectric conversion regions, A region insensitive to incident light is provided between adjacent photodetectors, A light-receiving element characterized by having the following features. (Item 2) The light-receiving element according to item 1, characterized in that the plurality of photoelectric conversion elements are provided on a part of the light-receiving surface of the light-receiving element. (Item 3) The light-receiving element according to item 2, characterized in that the portion of the light-receiving surface includes the center of the light-receiving surface. (Item 4) The array further comprises a microlens array that collects light incident on the aforementioned light-receiving element array, The microlens array has a microlens for each of the multiple photoelectric conversion elements, which is formed by combining microlenses such that the optical axis is offset toward the center of the photoreceiving element. A light-receiving element according to item 2 or 3, characterized in that it is a light-receiving element. (Item 5) The light-receiving element according to any one of items 1 to 4, further comprising a light-shielding layer provided in the insensitive region. (Item 6) The photodetector according to any one of items 1 to 5, characterized in that the plurality of photoelectric conversion elements are SPADs (Single Photon Avalanche Diodes). (Item 7) In each of the above-mentioned multiple light-receiving elements, The photodetector according to item 6, characterized in that the plurality of photoelectric conversion elements are formed on a semiconductor substrate, and adjacent photoelectric conversion elements are separated by a potential barrier. (Item 8) The photodetector according to item 6, further comprising an insulating region provided between adjacent photodetectors of the plurality of photodetectors. (Item 9) The light-receiving element according to item 6, further comprising a charge discharge region for discharging charge generated by light incident on the insensitive region. (Item 10) A light-emitting array in which multiple light-emitting elements are arranged in a two-dimensional manner, A lens that projects light emitted from the light-emitting element array to the outside, A light-receiving element according to any one of items 1 to 9, which receives light incident through the lens, A calculation means for determining distance based on the final elapsed time, A distance measuring device characterized by having the following features. (Item 11) The light-receiving element according to item 1, characterized in that the plurality of photoelectric conversion elements are provided on the entire light-receiving surface of the light-receiving element, and a portion of the plurality of photoelectric conversion elements are disabled. (Item 12) The aforementioned photoelectric conversion element is Depending on the supplied voltage, Because the aforementioned elapsed time is not measured, The measured elapsed time is not used in determining the final elapsed time, or By shielding the photoelectric conversion region from light, The light-receiving element described in item 11, characterized by being deactivated. (Item 13) The photodetector according to item 11 or 12, characterized in that the plurality of photoelectric conversion elements are SPADs (Single Photon Avalanche Diodes). (Item 14) A light-emitting array in which multiple light-emitting elements are arranged in a two-dimensional manner, A lens that projects light emitted from the light-emitting element array to the outside, A light-receiving element described in any one of items 11 to 13, which receives light incident through the lens, A calculation means for determining distance based on the final elapsed time, A distance measuring device characterized by having the following features. (Item 15) The distance measuring device according to item 14, characterized in that the photoelectric conversion element to be deactivated is determined by the position at which the reflected light of the light projected by the lens enters the light receiving element. (Item 16) The distance measuring device according to item 14 or 15, characterized in that, among the plurality of photoelectric conversion elements, any photoelectric conversion element that is not included in a region of a predetermined size that includes the position where the reflected light projected by the lens enters the light receiving element is disabled.

[0076] The present invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of Symbols]

[0077] 100...Distance measuring device, 110...Light-emitting unit, 111...Light-emitting element array, 120...Measurement unit, 121...Photodetector array, 130...Image-side telecentric lens, 150...Beam splitter, 160...Optical bandpass filter

Claims

1. A photodetector array in which multiple photodetectors are arranged in two dimensions, A measuring means for measuring the elapsed time from a reference time until the incidence of light on the plurality of light-receiving elements is detected, It has a determination means for determining the final elapsed time based on multiple measured elapsed times, Each of the aforementioned plurality of light-receiving elements is Multiple photoelectric conversion elements having adjacent photoelectric conversion regions, A region insensitive to incident light is provided between adjacent photodetectors, A light-receiving element characterized by having the following features.

2. The light-receiving element according to claim 1, characterized in that the plurality of photoelectric conversion elements are provided on a part of the light-receiving surface of the light-receiving element.

3. The light-receiving element according to claim 2, characterized in that the portion of the above includes the center of the light-receiving surface.

4. The array further comprises a microlens array that collects light incident on the aforementioned light-receiving element array, The microlens array has a microlens for each of the multiple photoelectric conversion elements, which is formed by combining microlenses such that the optical axis is offset toward the center of the photoreceiving element. The light-receiving element according to feature 2.

5. The light-receiving element according to claim 1, further comprising a light-shielding layer provided in the insensitive region.

6. The light-receiving element according to claim 1, characterized in that the plurality of photoelectric conversion elements are SPADs (Single Photon Avalanche Diodes).

7. In each of the above-mentioned multiple light-receiving elements, The photodetector according to claim 6, characterized in that the plurality of photoelectric conversion elements are formed on a semiconductor substrate, and adjacent photoelectric conversion elements are separated by a potential barrier.

8. The photodetector according to claim 6, further comprising an insulating region provided between adjacent photodetectors of the plurality of photodetectors.

9. The light-receiving element according to claim 6, further comprising a charge discharge region for discharging charge generated by light incident on the insensitive region.

10. A light-emitting array in which multiple light-emitting elements are arranged in two dimensions, A lens that projects light emitted from the light-emitting element array to the outside, A light-receiving element according to any one of claims 1 to 9, which receives light incident through the lens, A calculation means for determining distance based on the final elapsed time, A distance measuring device characterized by having the following features.

11. The light-receiving element according to claim 1, characterized in that the plurality of photoelectric conversion elements are provided on the entire light-receiving surface of the light-receiving element, and a portion of the plurality of photoelectric conversion elements are disabled.

12. The aforementioned photoelectric conversion element is Depending on the supplied voltage, Because the aforementioned elapsed time is not measured, The measured elapsed time is not used in determining the final elapsed time, or By shielding the photoelectric conversion region from light, The light-receiving element according to claim 11, characterized by being deactivated.

13. The light-receiving element according to claim 11, characterized in that the plurality of photoelectric conversion elements are SPADs (Single Photon Avalanche Diodes).

14. A light-emitting array in which multiple light-emitting elements are arranged in two dimensions, A lens that projects light emitted from the light-emitting element array to the outside, A light-receiving element according to any one of claims 11 to 13, which receives light incident through the lens, A calculation means for determining distance based on the final elapsed time, A distance measuring device characterized by having the following features.

15. The distance measuring device according to claim 14, characterized in that the photoelectric conversion element to be deactivated is determined by the position at which the reflected light of the light projected by the lens enters the light receiving element.

16. The distance measuring device according to claim 14, characterized in that, among the plurality of photoelectric conversion elements, any photoelectric conversion element that is not included in a region of a predetermined size that includes the position where the reflected light projected by the lens is incident on the light receiving element is disabled.

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