Distance measuring apparatus

Abstract

To provide a distance measuring device capable of measuring a distance with high accuracy in a range from a short distance to a long distance by reducing influence of noise light.SOLUTION: A distance measuring apparatus includes a light emitting unit, a light projecting unit configured to project light from the light emitting unit, and a light receiving unit including a light receiving pixel configured to receive reflected light obtained when the light projected by the light projecting unit reaches and is reflected by an object, wherein a first sub-pixel having a first sensitivity is arranged at a center of the light receiving pixel, and a plurality of second sub-pixels having a second sensitivity higher than the first sensitivity are arranged around the first sub-pixel so as to be rotationally symmetric about the first sub-pixel.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a distance measuring device. [Background technology]

[0002] Distance measuring devices are known that measure the distance to an object by measuring the time-of-flight (ToF), which is the time it takes from irradiating the object with a light pulse to receiving the light reflected from the object. In ToF distance measuring devices, the distance resolution is calculated by multiplying the measurable time resolution by half the speed of light. Therefore, distance measuring devices can achieve higher distance resolution by measuring time with higher time resolution. ToF distance measuring devices sometimes use a single photon avalanche diode (SPAD) to detect the time of incidence of photons at the light receiving unit with high time resolution (see, for example, Patent Document 1).

[0003] SPAD is an avalanche photodiode operated in Geiger mode by applying a bias voltage higher than the breakdown voltage VBD. Excess voltage above the breakdown voltage is called excess bias voltage, and is generally 2 to 5 V. The signal charge generated by photoelectric conversion causes avalanche breakdown, generating avalanche current. In the high electric field region, it takes 10 -12 The time is on the order of seconds, and the arrival of a single photon can be detected with high time resolution. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-081254 [Patent Document 2] Japanese Patent Publication No. 2022-187866 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 2 proposes a pixel in which light-receiving regions with different sensitivities are arranged so that their centers of gravity coincide with each other. With the configuration of Patent Document 2, it is difficult to configure a charge collection region at a position that is approximately the same distance from any position of the surrounding light-receiving region. If this light-receiving region is configured as a SPAD, the charge collection time within the same light-receiving region will vary, which will result in variation in distance measurement and deterioration of distance measurement accuracy when using a ToF method that is sensitive to the round-trip time of light.

[0006] An object of the present invention is to provide a distance measuring device that can reduce the influence of noise light and measure distances with high accuracy over a range from short distances to long distances. [Means for solving the problem]

[0007] The distance measuring device of the present invention comprises an emitting means, a light projecting means for projecting light from the emitting means, and a light receiving means including a light receiving pixel for receiving light reflected from an object when the light projected by the light projecting means reaches the object, wherein a first sub-pixel having a first sensitivity is arranged in the center of the light receiving pixel, and a plurality of second sub-pixels having a second sensitivity higher than the first sensitivity are arranged around the first sub-pixel in rotational symmetry with the first sub-pixel as the center. [Effects of the Invention]

[0008] According to the present invention, the influence of noise light is reduced and the It is possible to provide a distance measuring device capable of measuring distances with high accuracy. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a distance measuring device. [Figure 2] 3A and 3B are diagrams illustrating a light source unit included in the light projection unit. [Figure 3]FIG. 4 is a diagram schematically illustrating the intensity distribution of light emitted by a light source unit. [Figure 4] FIG. 2 is a schematic diagram of a measurement unit. [Figure 5] FIG. 2 is a diagram illustrating a configuration of a pixel. [Figure 6] 10 is an example of a histogram showing the relationship between the light-receiving time and the number of received photons. [Figure 7] 3 is a cross-sectional view of a sub-pixel including a semiconductor layer of a light-receiving element substrate. FIG. [Figure 8] FIG. 8 is a diagram showing the potential distribution in the aa' cross section of FIG. [Figure 9] FIG. 8 is a diagram showing the potential distribution in the cross section bb' of FIG. [Figure 10] FIG. 8 is a diagram showing the potential distribution in the cc' cross section of FIG. [Figure 11] FIG. 2 is an equivalent circuit diagram of a pixel. [Figure 12] FIG. 2 is a diagram schematically illustrating a TDC array section. [Figure 13] FIG. 1 is a diagram illustrating a schematic diagram of an oscillator of a high time resolution TDC. [Figure 14] 10 is a table showing changes in a buffer output signal and an oscillator internal signal. [Figure 15] 10A and 10B are diagrams for explaining the operation of the light source unit after light emission. [Figure 16] FIG. 10 is a diagram for explaining the operation after a pixel receives a photon. [Figure 17] FIG. 1 is a diagram illustrating a schematic diagram of an oscillator of a low time resolution TDC. [Figure 18] FIG. 2 is a diagram illustrating a configuration example of an oscillation voltage adjustment circuit. [Figure 19] 10 is a flowchart illustrating a distance measurement process. [Figure 20] 10 is an example of a histogram of the TDC measurement results for pixel H. [Figure 21] 10 is an example of a histogram in an environment where the intensity of noise light is high. [Figure 22] 10 is an example of a histogram of the TDC measurement results for pixel L. [Figure 23]10 is an example of a histogram of the measurement results of pixel H. [Figure 24] 10 is an example of a histogram of the measurement results of pixel L. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Embodiment> Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] [Configuration of distance measuring device] 1 is a diagram illustrating an example of the configuration of a distance measuring device 100. The distance measuring device 100 includes a light projecting unit 110, a measurement unit 120, a light receiving lens 132, and a control unit 140. The light projecting unit 110 includes a light source unit 111, a light source unit driving unit 112, a light source control unit 113, and a light projecting lens 131. The measurement unit 120 includes a light receiving unit 121, a TDC (Time-to-Digital Converter) array unit 122, a signal processing unit 123, and a light receiving control unit 124. The light receiving lens 132 and the light receiving unit 121 are also referred to as a light receiving unit 133. The light projecting unit 110 and the light receiving unit 133 form a telecentric afocal optical system in which a parallel light beam enters the lens via the light projecting lens 131.

[0012] The light projecting unit 110 will now be described. As shown in FIGS. 2(A) and 2(B), the light source unit 111 of the light projecting unit 110 includes a light source array 210 in which a plurality of light-emitting elements 211 are arranged in a two-dimensional array. A light source unit drive unit 112 drives the light source unit 111. A light source control unit 113 controls light emission by the light source unit 111. A light projecting lens 131 projects pulsed light (short optical pulses) generated by pulsed emission of each light-emitting element 211 into space. The pulsed light emitted from the different light-emitting elements 211 is projected in different directions in space. The projected pulsed light is irradiated onto an object (subject).

[0013] The measurement unit 120 and the light-receiving lens 132 will now be described. The light-receiving unit 121 receives, via the light-receiving lens 132, a portion of the reflected light that is produced when the light projected by the light-projecting unit 110 reaches an object and is reflected therefrom. The distance measuring device 100 may also include a beam splitter (light beam splitting means) (not shown). The beam splitter can split the reflected light that travels the same optical path as the light projected by the light-projecting unit 110, and guide it to the light-receiving unit 121.

[0014] The TDC array unit 122 measures the time of flight ToF of light, which is the time from when the light-emitting element 211 emits light to when the light-receiving unit 121 receives the light. However, a single measurement does not eliminate noise components due to ambient light and dark counts, resulting in a small S / N ratio (signal to noise ratio). Furthermore, there is a risk of large ranging errors due to the influence of noise in the measurement circuit, etc. For this reason, the TDC array unit 122 repeatedly measures the time from when light is emitted to when it is received.

[0015] The signal processing unit 123 creates a histogram of the time-of-flight measurement results obtained by the TDC array unit 122. The signal processing unit 123 removes noise components from the histogram and averages the measurement results. The signal processing unit 123 can calculate the distance D to the object with high accuracy by substituting the time-of-flight ToF obtained by averaging into the following equation (1). In equation (1), c is the speed of light. D=ToF / 2 / c (1)

[0016] The light receiving control unit 124 controls the light receiving unit 121, the TDC array unit 122, and the signal processing unit 123 to measure the light reflected from the object. The control unit 140 controls the light projecting unit 110 and the measurement unit 120, thereby controlling the entire distance measuring device 100.

[0017] [Light source unit 111] 2(A) to 2(C) are diagrams illustrating the light source unit 111 included in the light projection unit 110. Fig. 3 is a diagram schematically illustrating the intensity distribution when light emitted from the light source unit 111 is irradiated onto a surface with a certain reflectance via a light projection lens 131.

[0018] 2A is a diagram showing a schematic configuration of the light projection unit 110. The light projection unit 110 includes a light projection lens 131, a light source unit 111, and a light source unit drive section 112. The light source unit 111 includes a light source array 210 and a collimator lens array 220.

[0019] Fig. 2(B) is a diagram showing a schematic configuration of the light source array 210. The light source array 210 is a light source in which light emitting elements 211 are arranged in a two-dimensional array on a substrate. Fig. 2(C) is a diagram showing a schematic configuration of the collimator lens array 220. In the collimator lens array 220, collimator lenses 221 are arranged in a two-dimensional array.

[0020] The light emitting elements 211 of the light source array 210 are, for example, VCSELs (Vertical Cavity Surface Emitting Lasers). The light emitting elements 211 are not limited to VCSELs, but are preferably capable of being integrated in a one-dimensional or two-dimensional array.

[0021] The light emitting element 211 may be, for example, an edge-emitting laser or an LED (light emitting diode). When an edge-emitting laser is used as the light emitting element 211, the light source array 210 may be a laser bar in which edge-emitting lasers are arranged one-dimensionally on a substrate, or a laser bar stack in which the laser bars are stacked to form a two-dimensional light emitting element array configuration. When an LED is used as the light emitting element, the light source array 210 may be a light source in which LEDs are arranged in a two-dimensional array on a substrate.

[0022] In the distance measuring device 100, the wavelength of the light emitted by the light emitting element 211 is preferably in the near-infrared band to suppress the influence of ambient light. However, the wavelength of the light emitted by the light emitting element 211 is not limited to the near-infrared band.

[0023] VCSELs are fabricated using semiconductor processes using materials used in conventional edge-emitting lasers and surface-emitting lasers. The main material used for VCSELs that emit light in the near-infrared wavelength range is a GaAs-based semiconductor material. The DBR (Distributed Bragg Reflector) reflector that makes up a VCSEL can be a dielectric multilayer film (GaAs / AlGaAs) in which two thin films made of materials with different refractive indices are alternately and periodically stacked. The wavelength of the emitted light can be changed by adjusting the elemental combination and composition of the compound semiconductor.

[0024] The VCSELs included in the VCSEL array are provided with electrodes for injecting current and holes into the active layer. By controlling the timing of the current and hole injection, the VCSELs can emit any pulsed light or modulated light. The light source control unit 113 can, for example, drive the VCSELs serving as light-emitting elements 211 independently, or drive them by row, column, or specific area of ​​the VCSEL array.

[0025] Light emitted from a VCSEL serving as the light-emitting element 211 typically becomes divergent light due to diffraction at the aperture of the VCSEL. The light source unit 111 has a collimator lens array 220 in which collimator lenses 221 are arranged in a two-dimensional array in order to control the divergence of the divergent light from the light-emitting element 211 and to convert it into parallel light. The collimator lenses 221 included in the collimator lens array 220 are arranged in one-to-one correspondence with the light-emitting elements 211 of the light source array 210.

[0026] The light emitted from the VCSEL array (light source array 210) is collimated by the collimator lens array 220, and converted into parallel light in a direction perpendicular to the VCSEL array substrate (substrate of the light source array 210), for example.

[0027] The light projecting unit 110 of the distance measuring device 100 includes a light projecting lens 131 for dispersing the converted parallel light into a desired space and projecting the light. In the example of Fig. 2(A), the light projecting lens 131 is a concave lens, but it is not limited to a concave lens and can be various optical systems such as a convex lens or an aspherical lens with specific radiation characteristics.

[0028] The light projecting lens 131 may be, for example, a concave lens that sets the projection angle of the light projected from the light projecting unit 110 at ±45 degrees. The light projecting unit 110 may also be provided with a collimator lens array 220 that changes the direction of the light emitted from the VCSEL array, without using the light projecting lens 131.

[0029] FIG. 3 shows a projection area 311 of light projected onto an object plane 310 when the VCSEL array is configured with a 3×3 arrangement of VCSELs. The projection area 311 indicates an area whose diameter is approximately the full width at half maximum (FWHM) of the intensity distribution of the projected light on the object plane 310 through which the projected light passes. The light emitted from the VCSEL, which has been collimated by the collimator lens array 220, passes through the projector lens 131 to become a group of projected lights that are projected into space as projected light with a slight divergence angle. Therefore, the object plane 310 through which the projected light passes is a finite area. The spatial resolution of the group of projected lights is a 3×3 area per area of ​​the object plane shown in FIG. 3.

[0030] The light projecting unit 110 may change the output of the VCSEL based on the distance to the object to be measured. When the object is in a short distance (a distance shorter than a predetermined distance threshold), Since the signal strength becomes stronger, it is effective from the viewpoint of power to drive the light projecting unit 110 with a lower output of the VCSEL. On the other hand, when the object is at a long distance (longer than a predetermined distance threshold), the signal strength becomes weaker, so it is effective to drive the light projecting unit 110 with an increased output of the VCSEL.

[0031] Whether an object is in a close range or a long range may be set in advance depending on the object to be measured. Alternatively, whether an object is in a close range or a long range may be determined by measuring the distance to the object to be measured and comparing the measured distance with a predetermined distance threshold.

[0032] The light projecting unit 110 may also control the distance between the VCSEL and SPAD (pixel 411) and the main lens (such as the light projecting lens 131). The spatial distance between the VCSEL / SPAD and the main lens can be controlled using, for example, a piezoelectric element. When the object to be measured is located at a long distance, the laser beam per element, which is projected into space while expanding, can be focused at a distance close to the object by changing the distance between the VCSEL and the main lens. The density of the projected light increases at the distance where the object is located, and therefore the amount of signal received increases. The light projecting unit 110 can improve distance measurement accuracy by changing the distance between the VCSEL and the main lens based on the distance to the object.

[0033] [Measuring Unit 120] Fig. 4 is a schematic diagram of the measurement unit 120. The measurement unit 120 has a configuration in which a light receiving element substrate 410 and a logic substrate 420 are stacked. For the sake of explanation, Fig. 4 shows the light receiving element substrate 410 and the logic substrate 420 separately.

[0034] The light receiving element substrate 410 includes a light receiving section 121 in which pixels 411 (light receiving pixels) are arranged in a two-dimensional array. The light receiving section 121 has a plurality of pixels 411 (light receiving pixels) corresponding to the plurality of light emitting elements 211 of the light source array 210. The pixels 411 may be back-illuminated elements.

[0035] The logic board 420 includes a TDC array section 122, a signal processing section 123, and a light receiving control section 124. The functions mounted on each board are not limited to the example shown in Fig. 4. For example, all of the functions of the measurement unit 120 may be mounted on a single board.

[0036] The light receiving element substrate 410 and the logic substrate 420 are connected by inter-substrate connections 430. The inter-substrate connections 430 are, for example, Cu-Cu connections. One inter-substrate connection 430 may be provided for each column of pixels 411, multiple inter-substrate connections 430 may be provided for each column of pixels 411, or one may be provided for each pixel 411.

[0037] The pixel 411 included in the light receiving unit 121 has two types of sub-pixels: a low-sensitivity sub-pixel 501 (pixel L) that is a sub-pixel having a first sensitivity, and a high-sensitivity sub-pixel 502 (pixel H) that is a sub-pixel having a second sensitivity higher than the first sensitivity. The low-sensitivity sub-pixel 501 and the high-sensitivity sub-pixel 502 can be SPADs.

[0038] 5, the low-sensitivity sub-pixel 501 is disposed at the center of the pixel 411 (light-receiving pixel). The four high-sensitivity sub-pixels 502 are disposed around the low-sensitivity sub-pixel 501 in rotational symmetry with the low-sensitivity sub-pixel 501 at the center. Because light of higher intensity enters the center of the pixel 411 than the surrounding areas, the high-sensitivity sub-pixels 502 are disposed around the low-sensitivity sub-pixel 501 to prevent the SPAD from quickly becoming saturated. In particular, when the object to be measured is located at a short distance, the high-sensitivity sub-pixels 502 are disposed around the pixel 411, thereby reducing the time until saturation.

[0039] The charge collection regions in the photoelectric conversion units of the four high-sensitivity sub-pixels 502 also have the same shape and are arranged rotationally symmetrically around the low-sensitivity sub-pixel 501, so the time difference until charge collection for light entering the different high-sensitivity sub-pixels 502 is small. Therefore, the distance measuring device 100 can improve distance measurement accuracy by adopting the pixel configuration shown in Fig. 5. Any configuration in which the high-sensitivity sub-pixels 502 are equally distant from the charge collection regions, not limited to the configuration shown in this embodiment, will be sufficient because it reduces the time difference until charge collection.

[0040] The two types of sub-pixels included in the pixel 411 arranged on the light-receiving element substrate 410 only need to have relatively different sensitivities. As a method for making the sensitivities of the two types of sub-pixels different, for example, a light-absorbing film (neutral density filter, ND filter) is arranged on the side of the low-sensitivity sub-pixel 501 that receives reflected light from an object. In contrast, a material with a higher transmittance than the light-absorbing film is arranged on the side of the high-sensitivity sub-pixel 502 that receives reflected light, thereby creating a difference in sensitivity between the high-sensitivity sub-pixel 502 and the low-sensitivity sub-pixel 501. The neutral density filter arranged for the low-sensitivity sub-pixel 501 is a variable transmittance filter, and may be controlled so that its transmittance increases as the distance to the object increases.

[0041] Furthermore, the method of differentiating the sensitivities of the two types of subpixels is not limited to the method of arranging a light-absorbing film. As another method, a multilayer bandpass filter that passes light with a narrower band width than the spectral width of light incident on the high-sensitivity subpixel 502 may be arranged on the low-sensitivity subpixel 501. As another method, the area of ​​the low-sensitivity subpixel 501 in the XY plane may be made smaller than the area of ​​the high-sensitivity subpixel 502.

[0042] In distance measurement using the ToF method, the signal strength for distance measurement (the signal strength of the received reflected light) increases as the distance to the object decreases, and decreases as the distance to the object increases.Furthermore, the signal strength for distance measurement increases as the object's reflectivity increases, and decreases as the object's reflectivity decreases.

[0043] When a pixel 411 is configured with a low-sensitivity sub-pixel 501 and a high-sensitivity sub-pixel 502, the ranging device 100 may select which sub-pixel's signal received from which light is to be used for ranging, based on the signal strength of the reflected light. For example, when the signal strength of the reflected light is stronger than a predetermined threshold, the ranging device 100 uses the signal from the low-sensitivity sub-pixel 501 for ranging. On the other hand, when the signal strength of the reflected light is weaker than the predetermined threshold, the ranging device 100 uses the signal from the high-sensitivity sub-pixel 502 for ranging. By selectively switching which sub-pixel's signal received from which light is to be used for ranging, the ranging device 100 can achieve high-precision ranging with a wider distance dynamic range.

[0044] The principle of distance measurement using the low-sensitivity sub-pixel 501 and the high-sensitivity sub-pixel 502 by the measurement unit 120 will be described with reference to Fig. 6. Fig. 6 shows an example of a histogram (light-reception time histogram) showing the relationship between the light-reception time and the number of received photons. The light-reception time histogram 603 is a true histogram of pulsed light (short optical pulse). The true histogram is a histogram obtained when reflected light is detected at a light intensity that does not cause the sub-pixels to reach saturation.

[0045] The light-receiving time histogram 601 is a histogram of the number of photons received by the high-sensitivity sub-pixel 502, and the closer the distance to the object and the higher the light-receiving signal level, the earlier the peak occurs than in the light-receiving time histogram 603. When a SPAD is used, a recovery time (dead time) is required after light reception until the next light reception becomes possible. The higher the light-receiving signal strength, the sooner the pixel becomes saturated, and no light-receiving signal is generated during the recovery time.

[0046] The light-receiving time histogram 602 is a histogram of the number of photons received by the low-sensitivity sub-pixel 501. The low-sensitivity sub-pixel 501 does not saturate as early as the high-sensitivity sub-pixel 502, and therefore can receive light for a longer period of time than the high-sensitivity sub-pixel 502.

[0047] The peak time 604 in the light-reception time histogram 601 for the high-sensitivity sub-pixel 502 and the peak time 605 in the light-reception time histogram 602 for the low-sensitivity sub-pixel 501 deviate from the peak time 606 in the light-reception time histogram 603. Because the SPAD is prone to saturation, the peak time tends to be brought forward due to the influence of dead time.

[0048] The time at the intersection of the light-receiving time histogram 601 of the high-sensitivity sub-pixel 502 and the light-receiving time histogram 602 of the low-sensitivity sub-pixel 501 is approximately equal to the peak time 606 of the light-receiving time histogram 603. In this way, the measurement unit 120 can acquire the time at the intersection of the two histograms as the peak time 606 (the time at which reflected light is received) of the light-receiving time histogram 603. Therefore, even in situations where the signal strength is strong or the distance to the object is short, the distance measuring device 100 can measure the distance with high accuracy.

[0049] The measurement unit 120 may weight the light-receiving time histogram 601 of the high-sensitivity sub-pixel 502 and the light-receiving time histogram 602 of the low-sensitivity sub-pixel 501. For example, the measurement unit 120 may weight based on the signal strength of the reflected light. In this case, if the signal strength of the reflected light is stronger than a predetermined intensity threshold, the measurement unit 120 assigns a greater weight to the light-receiving time histogram 602 of the low-sensitivity sub-pixel 501. On the other hand, if the signal strength of the reflected light is weaker than the predetermined intensity threshold, the measurement unit 120 assigns a greater weight to the light-receiving time histogram 601 of the high-sensitivity sub-pixel 502.

[0050] The measurement unit 120 may assign weights based on the distance from the distance measuring device 100 to an object to be measured. In this case, if the distance to the object is shorter than a predetermined distance threshold, the measurement unit 120 assigns a larger weight to the light-reception time histogram 602 of the low-sensitivity sub-pixel 501. On the other hand, if the distance to the object is longer than the predetermined distance threshold, the measurement unit 120 assigns a larger weight to the light-reception time histogram 601 of the high-sensitivity sub-pixel 502.

[0051] The measurement unit 120 may set the degree of weighting by combining the signal strength of the reflected light and the distance to the object. Even when weighting is performed, the measurement unit 120 can obtain the time of intersection of the two histograms as the peak time 606 (the time of reception of the reflected light) of the light-reception time histogram 603. Note that the measurement unit 120 may calculate the peak time 606 of the light-reception time histogram 603 by adjusting the time of intersection of the two histograms according to the degree of weighting.

[0052] 7 is a cross-sectional view of a subpixel including a semiconductor layer 705 of a light-receiving element substrate. The light-receiving element substrate includes a semiconductor layer 705 and a wiring layer 706. The wiring layer 706 of the light-receiving element substrate is bonded to and faces a logic substrate wiring layer 707. The semiconductor layer 705 of the light-receiving element substrate includes a light-receiving region 701 that photoelectrically converts light, and an avalanche region 702 that generates an avalanche current using signal charges.

[0053] The light-shielding wall 703 is disposed between adjacent subpixels to prevent light that is obliquely incident on the light-receiving region 701 from reaching the light-receiving region 701 of the adjacent subpixel. The light-shielding wall 703 is formed of metal. The insulator region 704 is disposed to prevent the light-shielding wall 703 and the light-receiving region 701 from coming into direct contact with each other.

[0054] Fig. 8 is a diagram showing potential distribution in the a-a' cross section of the semiconductor layer 705 in Fig. 7. Fig. 9 is a diagram showing potential distribution in the bb' cross section of the semiconductor layer 705 in Fig. 7. Fig. 10 is a diagram showing potential distribution in the cc' cross section of the semiconductor layer 705 in Fig. 7.

[0055] Light incident on the semiconductor layer 705 of the light-receiving element substrate is photoelectrically converted in the light-receiving region 701, generating electrons and holes. The positively charged holes are discharged via the anode electrode Vbd (FIG. 11). The negatively charged electrons are transported as signal charges to the avalanche region 702 by an electric field set so that the potential decreases toward the avalanche region 702, as shown in FIGS. 8, 9, and 10.

[0056] The signal charge that reaches the avalanche region 702 causes avalanche breakdown due to the strong electric field in the avalanche region 702, generating an avalanche current. This phenomenon occurs not only due to signal light (reflected light emitted by the light source unit 111) but also due to the incidence of ambient light, which is noise light, and the incidence of ambient light becomes a noise component. Even in the absence of signal light or ambient light, avalanche current can be generated by thermally excited electrons. Avalanche current caused by thermally excited electrons is called dark count and becomes a noise component.

[0057] 11 is an equivalent circuit diagram of a pixel 411. The pixel 411 includes a SPAD element 1101, a load transistor 1102, an inverter 1103, a pixel selection switch 1104, and a pixel output line 1105. The SPAD element 1101 is a region that combines the light receiving region 701 and the avalanche region 702.

[0058] When the pixel selection switch 1104 is turned on, the output signal of the inverter 1103 is output as a pixel output signal to a pixel output line 1105. When no avalanche current is flowing, the voltage of the anode electrode Vbd is set so that a reverse bias equal to or greater than the breakdown voltage is applied to the SPAD element 1101. In this case, no current flows through the load transistor 1102, so the cathode potential Vc is close to the power supply voltage Vdd, and the pixel output signal is "0."

[0059] When an avalanche current is generated in the SPAD element by the arrival of a photon, the voltage of the cathode potential Vc drops and the output of the inverter 1103 is inverted. That is, the pixel output signal changes from "0" to "1." When the potential of the cathode potential Vc drops, the reverse bias applied to the SPAD element 1101 decreases, and when the reverse bias becomes equal to or lower than the breakdown voltage, the generation of the avalanche current stops.

[0060] After the generation of the avalanche current stops, a hole current flows from the power supply voltage Vdd to the cathode potential Vc via the load transistor 1102, causing the cathode potential Vc to rise. The output of the inverter 1103 is inverted again, and the pixel output signal returns from "1" to "0," returning to the state before the photon arrived. The signal output from the pixel in this way is input to the TDC array unit 122 via a relay buffer.

[0061] The TDC array section 122 of the measurement unit 120 will be described with reference to Fig. 12. Fig. 12 is a diagram schematically illustrating the TDC array section 122. The TDC array section 122 measures the time from when the light source unit 111 emits light until the pixel output signal changes from "0" to "1" as the ToF time.

[0062] The TDC array unit 122 has a high time resolution TDC 1201 and a low time resolution TDC 1202, each of which corresponds to half the number of pixels in the horizontal direction of the pixel array. The TDC array unit 122 can measure pixel outputs for one row at a time.

[0063] The output signals of the high-sensitivity sub-pixels 502 are controlled by a relay buffer so as to be input to a high-temporal resolution TDC 1201. The output signals of the low-sensitivity sub-pixels 501 are controlled by a relay buffer so as to be input to a low-temporal resolution TDC 1202. In Fig. 12, the odd-numbered pixel outputs are the outputs of the high-sensitivity sub-pixels 502, and the even-numbered pixel outputs are the outputs of the low-sensitivity sub-pixels 501. To make the delay times in the relay buffers approximately equal, the high-temporal resolution TDC 1201 and the low-temporal resolution TDC 1202 are arranged alternately.

[0064] The high time resolution TDC 1201 includes an oscillator 1211, an oscillation count circuit 1221, and a synchronous clock count circuit 1231. The low time resolution TDC 1202 includes an oscillator 1212, an oscillation count circuit 1222, and a synchronous clock count circuit 1232. The oscillation count circuits 1221 and 1222 count changes in the output values ​​of the corresponding oscillators 1211 and 1212. The synchronous clock count circuits 1231 and 1232 count the synchronous clocks.

[0065] The count results of the synchronous clock count circuits 1231 and 1232 constitute the upper bits, the internal signals of the oscillators 1211 and 1212 constitute the lower bits, and the count results of the oscillation count circuits 1221 and 1222 constitute the intermediate bits. In other words, the synchronous clock count circuits 1231 and 1232 perform rough measurements, the internal signals of the oscillators 1211 and 1212 perform fine measurements, and the oscillation count circuit measures the interval between them. Furthermore, each count result and internal signal may include redundant bits.

[0066] 13 is a diagram schematically illustrating the oscillator 1211 of the high time resolution TDC 1201. The oscillator 1211 includes an oscillation start / stop signal generation circuit 1340, buffers 1311 to 1318, an oscillation switch 1330, and a delay adjustment current source 1320. In the oscillator 1211, the eight stages of buffers 1311 to 1318 and the oscillation switch 1330 are alternately connected in series in a loop. The delay adjustment current source 1320 is provided for each of the buffers 1311 to 1318, and adjusts the delay time of the corresponding buffer according to the adjustment voltage.

[0067] 14 shows the values ​​of the output signals of the buffers 1311 to 1318 and the internal signal of the oscillator 1211 at the time of reset. The table in FIG. 14 also shows the delay time t buff 13 shows the changes in the output signals of buffers 1311 to 1318 and the internal signal of oscillator 1211 as time passes. WI11 output to WI18 output correspond to the output signals of buffers 1311 to 1318, respectively.

[0068] At the time of reset, the outputs of the buffers 1311 to 1317 are "0" and the output of the buffer 1318 is "1." After the oscillation switch 1330 is turned on, the delay time t buff After the time has elapsed (1×t buff After this, the outputs of the buffers 1312 to 1318, whose inputs and outputs are matched, do not change. On the other hand, the output of the buffer 1311, whose inputs and outputs are not matched, changes from "0" to "1" (the signal advances by one stage).

[0069] Furthermore, the delay time t buff After the time has elapsed (2×t buff After that, the outputs of the buffers 1311, 1313 to 1318, whose inputs and outputs are matched, do not change. On the other hand, the output of the buffer 1312, whose inputs and outputs are not matched, changes from "0" to "1" (the signal advances by another stage).

[0070] In this way, the delay time of one buffer stage t buff As time passes, the output of one of the buffers 1311 to 1318 that does not have input / output matching changes from "0" to "1" in order. buff After that, the output of all the buffers changes (the signal goes around once). After the oscillation switch 1330 is turned on, 16×t buff After that, the output of all buffers changes again (signal (two revolutions) and returns to its original state.

[0071] Then the output of each buffer is 16 × t buuf In this way, the time resolution of the high time resolution TDC1201 is t buff The time resolution is t buff is adjusted to 1 / 2 of the period of the synchronous clock by the oscillation voltage adjustment circuit 1241 described later. 7 is adjusted to be

[0072] The output of the oscillator 1211 (oscillator output), which is the output of the buffer 1318, is input to an oscillation count circuit 1221. The oscillation count circuit 1221 counts the rising edges of the oscillator output, thereby achieving a time resolution of 16×t buff The time measurement is carried out.

[0073] The operation of the light source unit after it emits light will be described with reference to Fig. 15. Fig. 15 is a timing chart showing the period from when the light emitting element 211 emits light until the SPAD element 1101 receives reflected light and the counting operation of the TDC ends. The timing chart shows changes in the cathode potential Vc of the SPAD element 1101, the pixel output signal, the synchronous clock, the count value of the synchronous clock count circuit, the output of the oscillator start / stop signal generation circuit, the oscillator output, and the count value of the oscillation count circuit.

[0074] The cathode potential Vc of the SPAD element 1101 is an analog voltage, with the voltage increasing toward the top of the drawing. The pixel output signal, synchronous clock, oscillator start / stop signal generation circuit output, and oscillator output are digital signals, with the top of the drawing indicating an on state ("1") and the bottom indicating an off state ("0"). The count values ​​of the synchronous clock count circuit and oscillator count circuit are digital values ​​expressed in decimal.

[0075] The operation after a pixel receives a photon will be described with reference to Figure 16. Figure 16 is an enlarged view of the oscillator start / stop signal generation circuit output, oscillator output, count value of the oscillator count circuit, and oscillator internal signal from time 1503 to time 1505 in Figure 15. The oscillator internal signal is a digital value expressed in decimal.

[0076] 15 and 16, the operation of measuring the time from time 1501 when the light-emitting element 211 emits light to time 1503 when a photon enters the SPAD element 1101 of the pixel and the pixel output signal changes from "0" to "1" using the high time resolution TDC 1201 will be described.

[0077] The light source control unit 113 controls the light source unit 111 so that the light emitting element 211 emits light at time 1501 synchronized with the rising edge of the synchronous clock supplied via the control unit 140. The synchronous clock counting circuit 1231 starts counting the rising edges of the synchronous clock from time 1501 when the light emitting element 211 emits light.

[0078] When a photon that is irradiated at time 1501 and reflected by an object enters a pixel at time 1503, the cathode potential Vc of the SPAD element 1101 drops, and the pixel output signal changes from "0" to "1." When the pixel output signal becomes "1," the output of the oscillation start / stop signal generation circuit 1340 changes from "0" to "1," and the oscillation switch 1330 turns on.

[0079] When the oscillation switch 1330 is turned on, the oscillation operation starts, and a signal loop starts inside the oscillator as shown in Fig. 16. After the oscillation switch 1330 is turned on, 16 × t buff After the time lapses and the signal makes two cycles in the oscillator, a rising edge appears in the oscillator output, and the oscillation count circuit 1221 counts the number of rising edges. Also, at time 1503, the synchronous clock count circuit 1231 stops counting and holds the count value.

[0080] After the oscillator 1211 is turned on at time 1503, the synchronous clock first rises at time 1505. When the synchronous clock rises, the output of the oscillation start / stop signal generation circuit 1340 becomes "0" and the oscillation switch 1330 turns off ("0"). When the oscillation switch 1330 becomes "0", the oscillation of the oscillator 1211 ends and the internal signal of the oscillation circuit is held as is. As the oscillation ends, the oscillation count circuit 1221 stops counting.

[0081] Count result D of the synchronous clock count circuit Gclk The time from time 1501 to time 1502 is 2 7 ×t buff The count result of the oscillator count circuit is D.ROclk The time from time 1503 to time 1504 is 2 4 ×t buff The value measured (counted) in units. Oscillator internal signal D ROin The time from time 1504 to time 1505 is t buff The high time resolution TDC 1201 performs the following processing on these values ​​and outputs them to the signal processing unit 123, thereby completing one measurement operation.

[0082] Count result D of oscillator count circuit ROclk and oscillator internal signal D ROin is added using the following formula (2). D RO =2 4 ×D ROclk +D ROin (2)

[0083] D obtained from equation (2) RO The time from time 1503 to time 1505 is t buff The time from time 1502 to time 1505 is equal to one cycle of the synchronous clock, and is measured in 2 7 ×t buff In the following equation (3), D RO By subtracting this, the time from time 1502 to time 1503 is obtained. Add this to the obtained time and add D, which is the time from time 1501 to time 1502. Gclk By adding these, the time of flight of light D ToF (The time from time 1501 to time 1503 is t buff The value measured in units is obtained. D ToF =2 7 ×D Gclk +(2 7 -D RO ) =2 7 ×D Gclk +(2 7 -2 4 ×D ROclk -D ROin ) (3)

[0084] 17 is a diagram schematically illustrating the oscillator 1212 of the low time resolution TDC 1202. In the oscillator 1212, four stages of buffers 1711 to 1714 and an oscillation switch 1730 are alternately connected in series in a loop. A delay adjustment current source 1720 is provided for each of the buffers 1711 to 1714, and adjusts the delay time of the corresponding buffer according to the adjustment voltage.

[0085] The oscillation voltage adjusting circuit 1242 adjusts the delay time t buff (the delay time of one buffer stage of the low time resolution TDC1202) is the delay time t buff The number of bits of the internal signal of oscillator 1212 can be adjusted to be two times the number of bits of the internal signal of oscillator 1211. As a result, the count period of oscillation count circuit 1222 becomes equal to the count period of oscillation count circuit 1221. Therefore, the number of bits of the output of oscillation count circuit 1222 becomes equal to the number of bits of the output of oscillation count circuit 1221. In addition, the number of bits of the internal signal of oscillator 1212 can be made one bit less than the number of bits of the internal signal of oscillator 1211.

[0086] Delay time for one buffer stage t buff The delay time t varies depending on factors resulting from the manufacturing process such as manufacturing errors of transistors, fluctuations in the voltage applied to the TDC circuit, and temperature. buff To suppress variations in the TDC, they are placed every eight TDCs.

[0087] 18 is a diagram showing an example of the configuration of the oscillation voltage adjustment circuits 1241 and 1242. The oscillation voltage adjustment circuits 1241 and 1242 have the same configuration. The oscillation voltage adjustment circuits 1241 and 1242 include a dummy oscillator 1801 and a 1 / 2 oscillator 1802, respectively. 3It has a frequency divider 1802 and a phase comparator 1803. The dummy oscillator 1801 has the same configuration as the oscillator of the connected TDC. Therefore, the dummy oscillator 1801 of the oscillation voltage adjustment circuit 1241 has the same configuration as the oscillator 1211. The dummy oscillator 1801 of the oscillation voltage adjustment circuit 1242 has the same configuration as the oscillator 1212.

[0088] The output of the dummy oscillator 1801 is 1 / 2 3 Input to divider 1802. 3 The frequency divider 1802 divides the frequency of the input clock signal by 2. 3 The phase comparator 1803 outputs a clock signal that is 1 / 2 the synchronous clock. 3 The output of the frequency divider 1802 is input to the phase comparator 1803. The phase comparator 1803 divides the frequency of the synchronous clock by 1 / 2. 3 The frequency is compared with the frequency of the clock signal output by the frequency divider 1802 .

[0089] The phase comparator 1803 is 1 / 2 3 When the frequency of the synchronous clock is higher than the frequency of the clock signal output by the frequency divider 1802, the output voltage is increased, and when the frequency of the synchronous clock is lower, the output voltage is decreased. The output voltage of the phase comparator 1803 is input to the delay adjustment current source 1320 of the oscillator 1211, and the oscillation frequency of the oscillator 1211 is set to 2 times the frequency of the synchronous clock. 3 Similarly, the output voltage of the phase comparator 1803 is input to the delay adjustment current source 1720 of the oscillator 1212, and the oscillation frequency of the oscillator 1212 is adjusted to twice the synchronous clock frequency. 3 The voltage is adjusted to double that of the

[0090] In this way, the oscillator's oscillation frequency is determined based on the synchronous clock frequency. Therefore, by generating the synchronous clock signal using an external IC that can output a constant frequency regardless of changes in the process, voltage, or temperature, it is possible to suppress variations in the oscillator's oscillation frequency due to changes in the process, voltage, or temperature.

[0091] For example, by inputting a 160MHz clock signal as the synchronous clock signal, the oscillation frequency becomes 1.28GHz, which is eight times the synchronous clock frequency, for both the high time resolution TDC1201 and the low time resolution TDC1202. The delay time t buff is 48.8 ps for the high time resolution TDC1201 and 97.7 ps for the low time resolution TDC1202.

[0092] [Distance measurement processing] 19 is a flowchart illustrating the distance measurement process. In the distance measurement process, a histogram of measurement time is generated for each of the low-sensitivity sub-pixel 501 and the high-sensitivity sub-pixel 502. The measurement unit 120 generates each histogram by measuring the time from when pulsed light is generated by the light-emitting element 211 to when the light is detected by the low-sensitivity sub-pixel 501 and the high-sensitivity sub-pixel 502.

[0093] In step S1901, the control unit 140 resets the histogram circuit and the measurement number counter i of the signal processing unit 123. In addition, the control unit 140 changes the connection of the relay buffer so that the output of the pixel 411 (ranging pixel) optically corresponding to the light emitting element 211 that is caused to emit light in step S1902 is input to the TDC array unit 122.

[0094] In step S1902, the control unit 140 causes some of the light emitting elements 211 that constitute the light source array 210 of the light source unit 111 to emit light, and at the same time causes the TDC array unit 122 to start measuring time.

[0095] In step S1903, the high time resolution TDC 1201 and The low time resolution TDC 1202 measures the time until the first charge is detected. The high time resolution TDC 1201 and low time resolution TDC 1202 can measure the time from light emission to light reception by receiving light reflected by the object and detecting that the output has changed from "0" to "1" at their corresponding sub-pixels. When the time corresponding to the maximum distance measurement range has elapsed since the light emission in step S1902, the process proceeds to step S1904.

[0096] In step S1904, the signal processing unit 123 adds the measurement result in step S1903 to the histogram for each subpixel. In step S1905, the signal processing unit 123 increments the value of the measurement number counter i by 1. In step S1906, the signal processing unit 123 increments the value of the measurement number counter i by a preset number N total It is determined whether the value of the measurement count counter i is greater than the set count N total If the value of the measurement number counter i is greater than the set number N, the process proceeds to step S1907. total If so, the process returns to step S1902.

[0097] In step S1907, the signal processing unit 123 removes noise components from the histogram for each subpixel. In step S1908, the signal processing unit 123 averages the valid measurement results that remain after being removed in step S1907, outputs the average value as the measured time of flight ToF, and ends one ranging sequence.

[0098] [Noise light suppression effect] The noise light suppression effect achieved by using pixels with different sensitivities as HDR (High Dynamic Range) pixels will now be described. First, the noise component removal process in step S1907 and the averaging process in step S1908 will be described, followed by the noise light reduction effect achieved by the pixel H (high-sensitivity sub-pixel 502) and pixel L (low-sensitivity sub-pixel 501) with different sensitivities.

[0099] FIG. 20 shows the Ntotal 20 shows an example of a histogram of TDC measurement results. The horizontal axis represents the TDC measurement result (measurement time), and the vertical axis represents frequency. The measurement results included in section 2002 form a frequency peak, and are therefore considered to be correct measurement results of the time from light emission to light reception. On the other hand, the measurement results included in section 2004 are sparsely distributed, and are considered to be noise light such as randomly occurring ambient light, or noise components due to dark counts. Therefore, the signal processing unit 123 removes the measurement results included in section 2004, and outputs the average value 2003 of the measurement results included in section 2002 as the distance measurement result.

[0100] FIG. 21 shows the N at pixel H when measuring the distance to an object placed at the same distance as in FIG. 20 under an environment where the intensity of noise light is stronger (there is more noise light) than in the situation in FIG. 20. total This is an example of a histogram of the TDC measurement results. The randomly generated noise light is strong (a lot of it), and before the reflected light from the object arrives, the noise light included in section 2004 total Once the TDC measurement is completed, no TDC distance measurement results are available for the light reflected from the object.

[0101] FIG. 22 shows the N at pixel L when measuring the distance to an object placed at the same distance as in FIG. 20 under the same environment as in FIG. 21. total 22 is an example of a histogram of TDC measurement results. Because pixel L has lower sensitivity than pixel H, the number of times TDC measurement is performed on noise light decreases. Therefore, the number of measurement results included in section 2002 increases, and a peak due to reflected light is formed. In the histogram of pixel L shown in FIG. 22, the signal processing unit 123 can calculate the average value of the measurement results included in section 2002 as the distance measurement result, just like the histogram in FIG. 20. In this way, low-sensitivity pixel L is more tolerant to situations where there is a lot of noise due to ambient light than high-sensitivity pixel H.

[0102] The problem of pixel H not being able to obtain measurement results is not limited to when noise light is stronger (more abundant), but can also occur when the object being measured is at a long distance. When the object is at a long distance, the period from when light is emitted until the reflected light returns (i.e., the period during which noise light is detected) becomes longer, and the TDC measurement at pixel H is completed before the reflected light from the object arrives.

[0103] By using pixel H and pixel L, the distance measuring device 100 according to this embodiment is capable of stable distance measurement with the influence of noise light suppressed, even when the intensity of noise light is high, the amount of noise light is large, or when measuring the distance to a distant object. Furthermore, the configuration of the light receiving element (SPAD) (light receiving area, thickness of the light receiving portion) and the voltage applied to the light receiving element are common to pixel H and pixel L. Therefore, there is little variation between the distance measurement results obtained by pixel H and those obtained by pixel L, and the distance measuring device 100 can obtain accurate distance measurement results with the influence of noise light suppressed.

[0104] [HDR driving method] 23 and 24, HDR driving of pixel H (high-sensitivity sub-pixel 502) and pixel L (low-sensitivity sub-pixel 501) will be described. FIG. 23 shows an example of a histogram of the measurement results of pixel H. FIG. 24 shows an example of a histogram of the measurement results of pixel L adjacent to pixel H.

[0105] 23 and 24 is the light emission period of the light emitting element 211 corresponding to pixel H. Light emission period 2402 in FIG. 24 is the light emission period of the light emitting element 211 corresponding to pixel L. The length of the light emission period 2402 is four times the length of the light emission period 2302. In this case, it is possible to perform distance measurement for pixel H four times as many times as for pixel L within the same time period. Since the number of distance measurement results to be averaged for pixel H is greater than that for pixel L and measurement is performed by the high time resolution TDC 1201, the distance measurement accuracy for pixel H is higher than that for pixel L, which is measured by the low time resolution TDC 1202.

[0106] When the object to be measured is far away, the time from the time of light emission to the time of light reception becomes long, increasing the possibility of measuring noise light. Therefore, the light-emitting element 211 corresponding to pixel L, which has a large noise light suppression effect, does not emit light again until reflected light is detected. On the other hand, the light-emitting element 211 corresponding to pixel H, which has a small noise light suppression effect, repeatedly emits light at a cycle shorter than the time from the time of light emission to the time of light reception for the object to be measured, and emits the next light before the emitted light is received. This shortens the time from the start of measurement by TDC to the detection of reflected light, thereby reducing the possibility of measuring noise light between the time of light emission and the time of receiving reflected light. Therefore, pixel H can perform accurate time measurement even in an environment with a large amount of noise light.

[0107] The signal processing unit 123 performs offset correction on the measurement result for pixel H based on the measurement result for adjacent pixel L. The offset correction is performed by adding a constant multiple of the light emission period 2302 (measurement period) of pixel H to the measurement result 2311 for pixel H based on the measurement result 2411 for adjacent pixel L.

[0108] From the measurement result 2411 for pixel L adjacent to pixel H, it is found that the time until the reflected light of the emitted light is received for pixel H is also approximately equal to the measurement result 2411. In the example of FIGS. 23 and 24, the measurement result 2411 for pixel L is greater than twice but less than three times the light emission period 2302 for pixel H. For this reason, the signal processing unit 123 adds twice the time of 2302 to the measurement result 2311 for pixel H in the offset correction.

[0109] The amount of time to be added in the offset correction may be determined based on the measurement results for pixel L adjacent to pixel H. The amount of offset correction may be determined based on the measurement results for four adjacent pixels L, or may be determined based on the measurement results for two adjacent pixels L in the horizontal or vertical direction. Furthermore, the amount of offset correction may be determined based on the measurement results of image sensors arranged in parallel.

[0110] According to the above embodiment, the distance measuring device 100 can perform distance measurement using pixel H without changing the characteristics of the SPAD element by arranging pixel H (high-sensitivity sub-pixel 502) and pixel L (low-sensitivity sub-pixel 501). Furthermore, by arranging pixel H and pixel L, the distance measuring device 100 can perform distance measurement with high accuracy even in an environment affected by noise light.

[0111] Although the embodiments of the present invention have been described in detail, the present invention is not limited to these specific embodiments, and various forms within the scope of the gist of the present invention are also included in the present invention. Furthermore, each of the above-described embodiments merely represents one embodiment of the present invention, and each embodiment can be combined as appropriate.

[0112] The disclosure of this embodiment includes the following configuration. (Configuration 1) Light emitting means; a light projecting means for projecting light from the light emitting means; a light receiving means including a light receiving pixel for receiving reflected light that is generated when the light projected by the light projecting means reaches an object and is reflected; and a first sub-pixel having a first sensitivity is disposed at the center of the light-receiving pixel; A plurality of second sub-pixels having a second sensitivity higher than the first sensitivity are arranged around the first sub-pixel in rotational symmetry with the first sub-pixel as the center. A distance measuring device characterized by: (Configuration 2) a beam splitter for splitting the reflected light that passes through the same optical path as the light projected by the light projecting means and guiding the split light to the light receiving means; 2. The distance measuring device according to configuration 1, (Configuration 3) the light emitting means has a plurality of light emitting elements arranged in a two-dimensional array, The light receiving means has a plurality of the light receiving pixels corresponding to the plurality of light emitting elements, respectively. 3. The distance measuring device according to configuration 1 or 2. (Configuration 4) The light emitting means and the light receiving means constitute an afocal optical system via the optical system of the light projecting means. 4. The distance measuring device according to any one of configurations 1 to 3. (Configuration 5) the light emitting means generates pulsed light; The first sub-pixel and the second sub-pixel are SPADs (Single Photon Avalanche Photo Diodes). 5. The distance measuring device according to any one of configurations 1 to 4. (Configuration 6) a measuring means for measuring a time from a timing at which pulsed light is generated by the light emitting means to a timing at which the light is detected by the first sub-pixel and the second sub-pixel, and for generating a histogram of the measured time for each of the first sub-pixel and the second sub-pixel; have 6. The distance measuring device according to any one of configurations 1 to 5. (Configuration 7) The area of ​​the first sub-pixel is smaller than the area of ​​the second sub-pixel. 7. The distance measuring device according to any one of configurations 1 to 6. (Configuration 8) a neutral density filter disposed on the side of the first sub-pixel that receives the reflected light; 8. The distance measuring device according to any one of configurations 1 to 7, wherein: (Configuration 9) The light-reducing filter is a variable transmittance filter, and is controlled so that the transmittance increases as the distance to the object increases. 9. The distance measuring device according to configuration 8. (Configuration 10) A bandpass filter that passes light having a narrower band than the spectral width of light incident on the second subpixel is disposed for the first subpixel. 10. The distance measuring device according to any one of configurations 1 to 9, wherein: (Configuration 11) Whether the signal received by the first sub-pixel or the signal received by the second sub-pixel is used for distance measurement is selected based on the signal intensity of the reflected light. 11. The distance measuring device according to any one of configurations 1 to 10. (Configuration 12) When the signal strength of the reflected light is stronger than a predetermined threshold, the signal of the first sub-pixel is used for distance measurement, and when the signal strength of the reflected light is weaker than the predetermined threshold, the signal of the second sub-pixel is used for distance measurement. 12. The distance measuring device according to configuration 11. (Configuration 13) The image sensor further includes an acquisition unit that acquires the light-receiving time of the reflected light based on a light-receiving time histogram that indicates the relationship between the light-receiving time of the reflected light and the number of received photons for each of the first sub-pixel and the second sub-pixel. 13. The distance measuring device according to any one of configurations 1 to 12. (Configuration 14) The acquisition means weights the light-receiving time histogram of the first sub-pixel and the light-receiving time histogram of the second sub-pixel based on at least one of the signal intensity of the reflected light and the distance to the object. 14. The distance measuring device according to configuration 13. (Configuration 15) The light-receiving pixel is a back-illuminated element. 15. A distance measuring device according to any one of configurations 1 to 14. (Configuration 16) The output of the light emitting means is changed based on the distance to the object. 16. A distance measuring device according to any one of configurations 1 to 15. (Configuration 17) The distance between the light emitting element of the light emitting means and the light projection lens that projects the pulsed light generated by the light emitting element is changed based on the distance to the object. 17. The distance measuring device according to any one of configurations 1 to 16. (Configuration 18) Light emitting means; a light projecting means for projecting light from the light emitting means; a light receiving means including a light receiving pixel for receiving reflected light that is generated when the light projected by the light projecting means reaches an object and is reflected; and The light-receiving pixel includes a first sub-pixel having a first sensitivity and a plurality of second sub-pixels having a second sensitivity higher than the first sensitivity, and the distances from the charge collecting regions of the second sub-pixels to the first sub-pixels are equal among the plurality of second sub-pixels. A distance measuring device characterized by: [Explanation of symbols]

[0113] 100: distance measuring device, 111: light source unit, 131: light projecting lens, 121: light receiving section, 501: low sensitivity sub-pixel, 502: high sensitivity sub-pixel

Claims

1. Light emitting means; a light projecting means for projecting light from the light emitting means; a light receiving means including a light receiving pixel for receiving reflected light that is generated when the light projected by the light projecting means reaches an object and is reflected; and a first sub-pixel having a first sensitivity is disposed at the center of the light-receiving pixel; A plurality of second sub-pixels having a second sensitivity higher than the first sensitivity are arranged around the first sub-pixel in rotational symmetry with the first sub-pixel as the center. A distance measuring device characterized by:

2. a beam splitter for splitting the reflected light that passes through the same optical path as the light projected by the light projecting means and guiding the split light to the light receiving means; 2. The distance measuring device according to claim 1.

3. the light emitting means has a plurality of light emitting elements arranged in a two-dimensional array, The light receiving means has a plurality of the light receiving pixels corresponding to the plurality of light emitting elements, respectively.

3. A distance measuring device according to claim 1 or 2.

4. The light emitting means and the light receiving means constitute an afocal optical system via the optical system of the light projecting means.

3. A distance measuring device according to claim 1 or 2.

5. the light emitting means generates pulsed light; The first sub-pixel and the second sub-pixel are SPADs (Single Photon Avalanche Photo Diodes).

3. A distance measuring device according to claim 1 or 2.

6. The image sensor further includes a measuring unit that measures the time from when the pulsed light is generated by the light emitting unit to when the light is detected by the first sub-pixel and the second sub-pixel, and generates a histogram of the measured time for each of the first sub-pixel and the second sub-pixel.

3. A distance measuring device according to claim 1 or 2.

7. The area of ​​the first sub-pixel is smaller than the area of ​​the second sub-pixel.

3. A distance measuring device according to claim 1 or 2.

8. a neutral density filter disposed on the side of the first sub-pixel that receives the reflected light; 3. A distance measuring device according to claim 1 or 2.

9. The neutral density filter is a variable transmittance filter, and is controlled so that the transmittance increases as the distance to the object increases.

9. The distance measuring device according to claim 8.

10. A bandpass filter that passes light of a band narrower than the spectral width of light incident on the second subpixel is disposed for the first subpixel.

3. A distance measuring device according to claim 1 or 2.

11. Whether the signal received by the first sub-pixel or the signal received by the second sub-pixel is used for distance measurement is selected based on the signal intensity of the reflected light.

3. A distance measuring device according to claim 1 or 2.

12. When the signal strength of the reflected light is stronger than a predetermined threshold, the signal of the first sub-pixel is used for distance measurement, and when the signal strength of the reflected light is weaker than the predetermined threshold, the signal of the second sub-pixel is used for distance measurement.

12. The distance measuring device according to claim 11.

13. The image sensor further includes an acquisition unit that acquires the light-receiving time of the reflected light based on a light-receiving time histogram that indicates the relationship between the light-receiving time of the reflected light and the number of received photons for each of the first sub-pixel and the second sub-pixel.

3. A distance measuring device according to claim 1 or 2.

14. The acquisition means weights the light-receiving time histogram of the first sub-pixel and the light-receiving time histogram of the second sub-pixel based on at least one of the signal intensity of the reflected light and the distance to the object.

14. The distance measuring device according to claim 13.

15. The light-receiving pixel is a back-illuminated element.

3. A distance measuring device according to claim 1 or 2.

16. The output of the light emitting means is changed based on the distance to the object.

3. A distance measuring device according to claim 1 or 2.

17. The distance between the light emitting element of the light emitting means and the light projection lens that projects the pulsed light generated by the light emitting element is changed based on the distance to the object.

3. A distance measuring device according to claim 1 or 2.

18. Light emitting means; a light projecting means for projecting light from the light emitting means; a light receiving means including a light receiving pixel for receiving reflected light that is generated when the light projected by the light projecting means reaches an object and is reflected; and The light-receiving pixel includes a first sub-pixel having a first sensitivity and a plurality of second sub-pixels having a second sensitivity higher than the first sensitivity, and the distances from the charge collecting regions of the second sub-pixels to the first sub-pixels are equal among the plurality of second sub-pixels. A distance measuring device characterized by:

Images