Patent ID: 12203807

MODE FOR CARRYING OUT THE INVENTION

Embodiments for implementing the present technology (hereinafter, referred to as embodiments) will be described below. Note that description will be provided in the following order.1. Configuration example of ranging system2. Configuration example of light receiving element3. First pixel circuit configuration example4. Setting example of active pixels and non-active pixels5. First wiring example of detection signal lines6. Second wiring example of detection signal lines7. Second pixel circuit configuration example8. Use example of ranging system9. Application example to mobile object
<1. Configuration Example of Ranging System>

FIG.1is a block diagram illustrating a configuration example of an embodiment of a ranging system to which the present technology is applied.

A ranging system11is, for example, a system which captures a range image using a ToF method. Here, the range image is an image which is obtained by detecting a range in a depth direction from the ranging system11to a subject for each pixel and which includes range pixel signals based on the detected ranges.

The ranging system11includes an illumination apparatus21and an imaging apparatus22.

The illumination apparatus21includes an illumination control unit31and a light source32.

The illumination control unit31controls a light irradiation pattern by the light source32under control by a control unit42of the imaging apparatus22. Specifically, the illumination control unit31controls the light irradiation pattern by the light source32in accordance with an irradiation code included in an irradiation signal supplied from the control unit42. For example, the irradiation code is a binary code of 1 (high) and 0 (low), and the illumination control unit31turns on the light source32when a value of the irradiation code is 1 and turns off the light source32when the value of the irradiation code is 0.

The light source32emits light of a predetermined wavelength range under control by the illumination control unit31. The light source32includes, for example, an infrared laser diode. Note that a type of the light source32and a wavelength range of irradiation light can be arbitrarily set in accordance with uses, and the like, of the ranging system11.

The imaging apparatus22is an apparatus which receives reflected light which is light (irradiation light) radiated from the illumination apparatus21and reflected on a subject12, a subject13, and the like. The imaging apparatus22includes an imaging unit41, the control unit42, a display unit43and a storage unit44.

The imaging unit41includes a lens51, a light receiving element52and a signal processing circuit53.

The lens51forms an image of incident light on a light receiving surface of the light receiving element52. Note that the lens51has an arbitrary configuration, and, for example, the lens51may include a plurality of lenses.

The light receiving element52includes, for example, a sensor in which single photon avalanche diodes (SPADs) are used in respective pixels. The light receiving element52receives reflected light from the subject12, the subject13, and the like, under control by the control unit42and supplies a pixel signal obtained as a result to the signal processing circuit53. This pixel signal represents a digital count value obtained by counting a time from when the illumination apparatus21radiates irradiation light until when the light receiving element52receives the light. A light emission timing signal indicating a timing for the light source32to emit light is also supplied from the control unit42to the light receiving element52.

The signal processing circuit53performs processing on the pixel signal supplied from the light receiving element52under control by the control unit42. For example, the signal processing circuit53detects a range to the subject for each pixel on the basis of the pixel signal supplied from the light receiving element52and generates a range image indicating the range to the subject for each pixel. Specifically, the signal processing circuit53acquires a time (count value) from when the light source32emits light until when each pixel of the light receiving element52receives light, for each pixel a plurality of times (for example, several thousands to several tens of thousands of times). The signal processing circuit53creates a histogram corresponding to the acquired time. The signal processing circuit53then determines a time it takes light radiated from the light source32to return after being reflected on the subject12or the subject13by detecting a peak of the histogram. The signal processing circuit53further performs computation of obtaining a range to an object on the basis of the determined time and speed of light. The signal processing circuit53supplies the generated range image to the control unit42.

The control unit42includes, for example, a control circuit such as a field programmable gate array (FPGA) and a digital signal processor (DSP), a processor, and the like. The control unit42controls the illumination control unit31and the light receiving element52. Specifically, the control unit42supplies an irradiation signal to the illumination control unit31and supplies a light emission timing signal to the light receiving element52. The light source32emits irradiation light in accordance with the irradiation signal. The light emission timing signal may be the irradiation signal supplied to the illumination control unit31. Further, the control unit42supplies the range image acquired from the imaging unit41to the display unit43and causes the range image to be displayed at the display unit43. Still further, the control unit42causes the range image acquired from the imaging unit41to be stored in the storage unit44. Further, the control unit42outputs the range image acquired from the imaging unit41to outside.

The display unit43includes, for example, a panel display apparatus such as a liquid crystal display apparatus and an organic electro luminescence (EL) display apparatus.

The storage unit44can include an arbitrary storage apparatus, storage medium, or the like, and stores the range image, and the like.

<2. Configuration Example of Light Receiving Element>

FIG.2is a block diagram illustrating a configuration example of the light receiving element52.

The light receiving element52includes a pixel driving unit111, a pixel array112, a multiplexer (MUX)113, a time measuring unit114and an input/output unit115.

The pixel array112has a configuration in which pixels121which detect incidence of photons and output detection signals indicating detection results as pixel signals are arranged in two dimensions in a matrix in a row direction and in a column direction. Here, the row direction refers to an arrangement direction of the pixels121in a row of pixels, that is, a horizontal direction, and the column direction refers to an arrangement direction of the pixels121in a column of pixels, that is, a vertical direction. WhileFIG.2illustrates the pixel array112having a configuration of pixel arrangement of 10 rows and 12 columns due to space limitation, the number of rows and the number of columns of the pixel array112are not limited to these, and the pixel array112may have any number of rows and columns.

Pixel drive lines122are wired for each row of pixels along a horizontal direction on matrix pixel arrangement of the pixel array112. The pixel drive line122transmits a drive signal for driving the pixel121. The pixel driving unit111drives each pixel121by supplying a predetermined drive signal to each pixel121via the pixel drive line122. Specifically, the pixel driving unit111performs control to set part of the pixels121among a plurality of pixels121arranged in two dimensions in a matrix as active pixels and set the remaining pixels121as non-active pixels at a predetermined timing in accordance with a light emission timing signal supplied from outside via the input/output unit115. The active pixels are pixels which detect incidence of photons, and the non-active pixels are pixels which do not detect incidence of photons. A detailed configuration of the pixel121will be described later.

Note that whileFIG.2illustrates the pixel drive line122as one wiring, the pixel drive line122may include a plurality of wirings. One end of the pixel drive line122is connected to an output end corresponding to each row of pixels of the pixel driving unit111.

The MUX113selects output from the active pixel in accordance with switching between the active pixel and the non-active pixel within the pixel array112. The MUX113then outputs a pixel signal input from the selected active pixel to the time measuring unit114.

The time measuring unit114generates a count value corresponding to a time from when the light source32emits light until when the active pixel receives light on the basis of the pixel signal of the active pixel supplied from the MUX113and the light emission timing signal indicating the light emission timing of the light source32. The light emission timing signal is supplied from outside (the control unit42of the imaging apparatus22) via the input/output unit115.

The input/output unit115outputs the count value of the active pixel supplied from the time measuring unit114to outside (the signal processing circuit53) as the pixel signal. Further, the input/output unit115supplies the light emission timing signal supplied from the control unit42to the pixel driving unit111and the time measuring unit114.

<3. First Pixel Circuit Configuration Example>

FIG.3illustrates a configuration example of a first pixel circuit of the pixel121arranged in the pixel array112.

The pixel121illustrated inFIG.3includes an SPAD211, a transistor212, a transistor213, an inverter214, a voltage conversion circuit215, and an output buffer216. The transistor212includes a P-type MOS transistor, and the transistor213includes an N-type MOS transistor.

A cathode of the SPAD211is connected to a drain of the transistor212and is connected to an input terminal of the inverter214and a drain of the transistor213. An anode of the SPAD211is connected to a power supply VSPAD.

The SPAD211is a photodiode (single photon avalanche photodiode) which avalanche amplifies a generated electron upon incidence of incident light to output a signal of a cathode voltage VS. The power supply VSPAD to be supplied to the anode of the SPAD211is, for example, set at a negative bias (negative potential) of −20 V.

The transistor212which is a constant current source which operates in a saturation region, performs passive quench by functioning as a quenching resistor. A source of the transistor212is connected to a power supply voltage VE, and a drain is connected to the cathode of the SPAD211, the input terminal of the inverter214, and the drain of the transistor213. This allows the power supply voltage VE to be also supplied to the cathode of the SPAD211. A pull-up resistor can be also used in place of the transistor212connected to the SPAD211in series.

A voltage (hereinafter referred to as an excess bias) higher than a breakdown voltage VBD of the SPAD211is applied to the SPAD211to detect light (photon) with sufficient efficiency. For example, assuming that the breakdown voltage VBD of the SPAD211is 20 V, and a voltage higher than the breakdown voltage VBD by 3 V is applied, the power supply voltage VE to be supplied to the source of the transistor212is set at 3 V.

A drain of the transistor213is connected to the cathode of the SPAD211, the input terminal of the inverter214and the drain of the transistor212, and a source of the transistor213is connected to ground (GND). A gating control signal VG is supplied to a gate of the transistor213from the pixel driving unit111.

In a case where the pixel121is set as an active pixel, a Lo (Low) gating control signal VG is supplied to the gate of the transistor213from the pixel driving unit111. Meanwhile, in a case where the pixel121is set as a non-active pixel, a Hi (High) gating control signal VG is supplied to the gate of the transistor213from the pixel driving unit111.

The inverter214outputs a Hi signal VSINVwhen the cathode voltage VS as an input signal is Lo, and outputs a Lo signal VSINVwhen the cathode voltage VS is Hi. Hereinafter, the signal VSINVto be output by the inverter214will be also referred to as an inversion signal VSINV.

The voltage conversion circuit215converts the inversion signal VSINVinput from the inverter214into a low-voltage signal VSLOWand outputs the low-voltage signal VSLOWto the output buffer216. The inversion signal VSINVbecomes a signal having a voltage amplitude from 0 V to 3 V, and the voltage conversion circuit215converts this signal VSINVhaving a voltage amplitude from 0 V to 3 V into a signal VSLOWhaving a voltage amplitude from 0 V to 1 V. The output buffer216is an output unit which outputs the signal VSLOWinput from the voltage conversion circuit215as a detection signal PFout indicating incidence of a photon on the SPAD211.

InFIG.3, the transistor212, the transistor213, the inverter214and the voltage conversion circuit215included in a dashed region221are elements (group) which operate at a power supply voltage VE which is a first power supply voltage. Meanwhile, the output buffer216included in a dashed-dotted region222is an element (group) which operates at a power supply voltage VDD which is a second power supply voltage lower than the first power supply voltage. The power supply voltage VDD is, for example, set at 1 V.

Operation in a case where the pixel121is set as the active pixel will be described next with reference toFIG.4.FIG.4is a graph indicating change of the cathode voltage VS of the SPAD211in accordance with incidence of a photon and the detection signal PFout.

First, in a case where the pixel121is an active pixel, the transistor213is switched off by the Lo gating control signal VG.

At time before time t0inFIG.4, the power supply voltage VE (for example, 3 V) is supplied to the cathode of the SPAD211, and the power supply VSPAD (for example, −20 V) is supplied to the anode, and a reverse voltage higher than the breakdown voltage VBD (=20 V) is thereby applied to the SPAD211, so that the SPAD211is put into a Geiger mode. In this state, the cathode voltage VS of the SPAD211is the same as the power supply voltage VE.

If a photon is incident on the SPAD211which is put into the Geiger mode, avalanche multiplication occurs, and a current flows to the SPAD211.

If avalanche multiplication occurs at time t0, and a current flows to the SPAD211, at and after time t0, a current also flows to the transistor212by a current flowing to the SPAD211, thereby voltage drop occurs by a resistance component of the transistor212.

If the cathode voltage VS of the SPAD211becomes lower than 0 V at time t2, avalanche amplification stops because the voltage is lower than the breakdown voltage VBD. Here, operation of stopping avalanche amplification as a result of voltage drop being occurred by a current generated by the avalanche amplification flowing to the transistor212, and the cathode voltage VS becoming lower than the breakdown voltage VBD in association with occurrence of the voltage drop, is quench operation.

If the avalanche amplification stops, a current flowing through the resistor of the transistor212gradually decreases, the cathode voltage VS returns to the original power supply voltage VE again at time t4, and the pixel is put into a state where the pixel can detect a next new photon (recharge operation).

The inverter214outputs a Lo inversion signal VSINVwhen the cathode voltage VS which is an input voltage is equal to or higher than a predetermined threshold voltage Vth (=VE/2) and outputs a Hi inversion signal VSINVwhen the cathode voltage VS is lower than the predetermined threshold voltage Vth. The output buffer216also outputs a Lo detection signal PFout when the cathode voltage VS is equal to or higher than the predetermined threshold voltage Vth (=VE/2) and outputs a Hi detection signal PFout when the cathode voltage VS is lower than the predetermined threshold voltage Vth. In the example inFIG.4, the output buffer216outputs the Hi detection signal PFout during a period from time t1to time t3.

Note that in a case where the pixel121is set as a non-active pixel, a Hi gating control signal VG is supplied to the gate of the transistor213from the pixel driving unit111to switch on the transistor213. This makes the cathode voltage VS of the SPAD2110 V (GND), and makes a voltage between the anode and the cathode of the SPAD211equal to or lower than the breakdown voltage VBD, so that the SPAD211does not react even if a photon is incident on the SPAD211.

<4. Setting Example of Active Pixels and Non-Active Pixels>

A setting example of active pixels and non-active pixels will be described next.

The pixel driving unit111determines a predetermined number of spots SP determined in advance within the pixel array112assuming a plurality of adjacent pixels121as one spot (cluster) SP and sets active pixels. In the present embodiment, the pixel driving unit111, for example, sets four pixels of 2×2 as one spot SP and sets 9 spots SP within the pixel array112.

The pixel array112inFIG.5includes 256 pixels121of 16 rows and 16 columns. Among 256 pixels121, hatched pixels121represent active pixels, and the pixels121which are not hatched represent non-active pixels.

The pixel driving unit111, for example, sets predetermined spots SP1to SP9within the pixel array112as active pixels assuming four pixels of 2×2 as one spot SP. Note that hereinafter, respective pixels of 2×2 constituting one spot SP will be also referred to as SP constituent pixels. Further, in a case where respective SP constituent pixels which constitute one spot SP are distinguished, as illustrated inFIG.5, the respective SP constituent pixels will be referred to as an SP constituent pixel A, an SP constituent pixel B, an SP constituent pixel C and an SP constituent pixel D in accordance with positions of the SP constituent pixels within the spot SP.

Note that while an example will be described in the present embodiment where one spot SP includes four pixels of 2×2, and the number of spots SP is nine, a configuration of pixels which constitute the spot SP is not limited to four pixels of 2×2. Further, the number of spots SP to be set for the pixel array112is not limited to nine. For example, the spot SP may be set as two pixels of 2×1, nine pixels of 3×3, or the like, and the number of spots SP to be set for the pixel array112may be set as four, six, or the like.

The pixel driving unit111further keeps resolution of an area of ranging as the imaging apparatus22at equal to or higher than a predetermined value by moving the position of each spot SP set as illustrated inFIG.5for each period.

By setting only part of pixels within the pixel array112as active pixels in this manner, it is possible to prevent a power supply from fluctuating as a result of an instantaneous operating current becoming too large and prevent the power supply fluctuation from affecting range accuracy. Additionally, spots are set as a target which is irradiated with laser light, and thus, by limiting the active pixels to part of spots SP in accordance with laser irradiation, it is possible to reduce power consumption.

<5. First Wiring Example of Detection Signal Lines>

Wiring layout of signal lines which transmit the detection signal PFout output by each pixel121of the pixel array112as a pixel signal will be described.

FIG.6is a view illustrating a first wiring example of the signal lines which transmit the detection signal PFout.

The first wiring example is an arrangement example of the signal lines in a case where the signal lines which transmit the detection signal PFout are individually provided for each pixel.

In a case where the signal lines are individually provided for each pixel, 256 signal lines241which are 16 signal lines in each row are required for the whole pixel array112because the pixel array112includes 256 pixels121of 16 rows and 16 columns.FIG.6illustrates 16 signal lines241arranged in one row with one signal line due to space limitation.

The MUX113selects signal lines241of pixels121set as the active pixels among 256 pixels121and acquires the detection signals PFout from the active pixels. The number of the active pixels is 36 of 4 pixels (the number of pixels in one spot SP)×9 (the number of spots SP), and thus, the number of signal lines242to be output to the time measuring unit114from the MUX113becomes 36.FIG.6illustrates four signal lines242with one signal line due to space limitation.

The time measuring unit114includes time to digital converter (TDC) circuits corresponding to the detection signals PFout output from 36 active pixels. Specifically, the time measuring unit114includes TDC circuits (TDC_SP1_PixA to TDC_SP1_PixD) of SP constituent pixels A to D of a spot SP1, TDC circuits (TDC_SP2_PixA to TDC_SP2_PixD) of SP constituent pixels A to D of a spot SP2, TDC circuits (TDC_SP3_PixA to TDC_SP3_PixD) of SP constituent pixels A to D of a spot SP3, . . . , TDC circuits (TDC_SP9_PixA to TDC_SP9_PixD) of SP constituent pixels A to D of a spot SP9. Each TDC circuit generates a count value corresponding to a time from when the light source32emits light until when the active pixel receives the light from the detection signal PFout of the active pixel and the light emission timing signal which are input.

As described above, by individually providing the signal lines241for each pixel, it is possible to deal with arbitrary nine spots SP1to SP9set within the pixel array112. However, it is not realistic to individually provide the signal lines241for each pixel because the number of wirings becomes extremely large. Further, there is a concern that crosstalk between pixels and skew, signal delay, and the like, of the detection signals PFout may occur if the signal lines241are dense.

<6. Second Wiring Example of Detection Signal Lines>

To address this concern, a second wiring example for reducing signal lines which transmit the detection signals PFout will be described.

In the second wiring example, a plurality of adjacent pixels within the pixel array112is set as one unit U.

FIG.7is a view illustrating one unit U in a case where 16 pixels of 4×4 are set as one unit U.

In a case where one unit U includes 16 pixels of 4×4, one unit U includes four spots SP each including 4 pixels of 2×2, and thus, one unit U includes four sets of SP constituent pixels A to D.

Output terminals of four SP constituent pixels A included in one unit U are connected using vertical wirings261A, and a signal line271A which transmits detection signals PFout of four SP constituent pixels A included in one unit U is disposed in a row of pixels of predetermined SP constituent pixels A within the unit U.

Output terminals of four SP constituent pixels B included in one unit U are connected using vertical wirings261B, and a signal line271B which transmits detection signals PFout of four SP constituent pixels B included in one unit U is disposed in a row of pixels of predetermined SP constituent pixels B within the unit U.

Output terminals of four SP constituent pixels C included in one unit U are connected using vertical wirings261C, and a signal line271C which transmits detection signals PFout of four SP constituent pixels C included in one unit U is disposed in a row of pixels of predetermined SP constituent pixels C within the unit U.

Output terminals of four SP constituent pixels D included in one unit U are connected using vertical wirings261D, and a signal line271D which transmits detection signals PFout of four SP constituent pixels D included in one unit U is disposed in a row of pixels of predetermined SP constituent pixels D within the unit U.

Further, signal lines271A to271D included in one unit U are disposed in rows of pixels which are different from each other.

By putting output of the SP constituent pixels of the same type within one unit U together with one signal line271using the vertical wirings261in this manner, it is possible to achieve connection to the MUX113with one signal line271for each row of pixels in one unit U. The number of signal lines271per one unit U becomes four.

FIG.8illustrates a wiring example of the signal lines271in a case where the signal lines271are put together for each of the SP constituent pixels A to D within the unit U as illustrated inFIG.7.

FIG.8is a second wiring example in which signal lines which transmit the detection signals PFout are reduced.

In a case where the signal lines271are put together for each of the SP constituent pixels A to D within the unit U as illustrated inFIG.7, the number of the signal lines271to the MUX113becomes 64 in the whole of the pixel array112as illustrated inFIG.8. It is therefore possible to substantially reduce the number of the signal lines271to the MUX113according to the second wiring example compared to the first wiring example illustrated inFIG.6. This can improve crosstalk and skew of the detection signal PFout at each pixel121, signal delay, and the like.

In the second wiring example, a plurality of SP constituent pixels of the same type (one of the SP constituent pixels A to D) within the unit U utilizes one common signal line271, and thus cannot be set as active pixels at the same time.

The pixel driving unit111therefore sets a plurality of spots SP for the pixel array112in accordance with the following spacing rule. In a case where one unit U includes 16 pixels of 4×4, the pixel driving unit111determines an adjacent spot SP so that the same type of the respective SP constituent pixels (SP constituent pixels A to D) of the spot SP comes fourth or any later in other adjacent spots SP both in a horizontal direction and in a vertical direction. In other words, the pixel driving unit111determines each spot SP so that a predetermined SP constituent pixel (for example, the SP constituent pixel A) in a first spot SP within the pixel array112is separate from the same type of the SP constituent pixel (for example, the SP constituent pixel A) of a second spot SP adjacent to the first spot SP by three or more pixels.

Setting of the spots SP in accordance with the spacing rule will be described with reference toFIG.9.

For example, an SP constituent pixel D of the spot SP1is separate from the same type of the SP constituent pixel D of the spot SP2which is adjacent to the spot SP1in a horizontal direction by three pixels. In other words, the SP constituent pixel D of the spot SP2is the fourth pixel in a horizontal direction from the same type of the SP constituent pixel D of the adjacent spot SP1.

Further, the SP constituent pixel D of the spot SP1is separate from the same type of the SP constituent pixel D of the spot SP4which is adjacent to the spot SP1in a vertical direction by three pixels. In other words, the SP constituent pixel D of the spot SP4is the fourth pixel in a vertical direction from the same type of the SP constituent pixel D of the adjacent spot SP1.

For example, an SP constituent pixel B of the spot SP5is separate from the same type of the SP constituent pixel B of the spot SP6which is adjacent to the spot SP5in a horizontal direction by three pixels. In other words, the SP constituent pixel B of the spot SP6is the fourth pixel in a horizontal direction from the same type of the SP constituent pixel B of the adjacent spot SP5.

Further, the SP constituent pixel B of the spot SP5is separate from the same type of the SP constituent pixel B of the spot SP8which is adjacent to the spot SP5in a vertical direction by three pixels. In other words, the SP constituent pixel B of the spot SP5is the fourth pixel in a vertical direction from the same type of the SP constituent pixel B of the adjacent spot SP5.

In a case where a plurality of spots SP is set for the pixel array112in accordance with such a spacing rule, as can be clear fromFIG.9, the number of the SP constituent pixels A to D selected as active pixels within each unit U always becomes equal to or less than one. It is therefore possible to use a common signal line271for each of the SP constituent pixels of the same type (SP constituent pixels A to D) within the unit U as illustrated inFIG.7.

While an example has been described in the above-described example where one spot SP includes four pixels (SP constituent pixels) of 2×2, the above-described example can be similarly applied also in a case where the number of constituent pixels of the spot SP is different. For example, also in a case where one spot SP includes two pixels (the SP constituent pixel A and the SP constituent pixel B) of 2×1, or in a case where one spot SP includes six pixels (the SP constituent pixel A, the SP constituent pixel B, the SP constituent pixel C, the SP constituent pixel D, the SP constituent pixel E and the SP constituent pixel F) of 2×3, the number of the same type of the SP constituent pixels selected as active pixels within each unit U of 4×4 always becomes equal to or less than one by a plurality of spots SP being set in accordance with the above-described spacing rule.

A case where the number of pixels included in one unit U is not 16 pixels of 4×4 will be described next.

For example, a case where one unit U includes 25 pixels of 5×5 will be described. It is assumed that one spot SP includes four pixels (the SP constituent pixels A to D) of 2×2 in a similar manner to the above-described example.

In a case where one unit U includes 25 pixels of 5×5, the pixel driving unit111determines an adjacent spot SP so that the same type of the respective SP constituent pixels A to D of the spot SP comes fifth or any later in other adjacent spots SP both in a horizontal direction and in a vertical direction. In other words, the pixel driving unit111determines each spot SP so that a predetermined SP constituent pixel (for example, the SP constituent pixel A) in a first spot SP within the pixel array112is separate from the same type of the SP constituent pixel (for example, the SP constituent pixel A) of a second spot SP adjacent to the first spot SP by four or more pixels. The number of the same type of the SP constituent pixels selected as active pixels within each unit U of 5×5 always becomes equal to or less than one by a plurality of spots SP being set in accordance with this spacing rule.

Next, a case where one unit U includes 36 pixels of 6×6 will be described. It is assumed that one spot SP includes four pixels (the SP constituent pixels A to D) of 2×2 in a similar manner to the above-described example.

In a case where one unit U includes 36 pixels of 6×6, the pixel driving unit111determines an adjacent spot SP so that the same type of the respective SP constituent pixels A to D of the spot SP comes sixth or any later in other adjacent spots SP both in a horizontal direction and in a vertical direction. In other words, the pixel driving unit111determines each spot SP so that a predetermined SP constituent pixel (for example, the SP constituent pixel A) in a first spot SP within the pixel array112is separate from the same type of the SP constituent pixel (for example, the SP constituent pixel A) of a second spot SP adjacent to the first spot SP by five or more pixels. The number of the same type of the SP constituent pixels selected as active pixels within each unit U of 6×6 always becomes equal to or less than one by a plurality of spots SP being set in accordance with this spacing rule.

Relationship between the signal lines271which are used in common within the unit U and the spacing rule can be described as follows. In the pixel array112, in a case where one spot SP includes N×M pixels (N>0, M>0, where N and M do not become 1 at the same time), and one unit U includes L×L (L>1), output of the same type of the plurality of SP constituent pixels within one unit U is put together with one signal line271using one or more vertical wirings261. The pixel driving unit111determines a plurality of spots SP within the pixel array112so that the same type of the respective SP constituent pixels of the spot SP comes L-th or any later in other adjacent spots SP both in a horizontal direction and in a vertical direction. This can substantially reduce the number of the signal lines271from the pixel array112to the MUX113, so that it is possible to improve crosstalk and skew of the detection signal PFout, signal delay, and the like.

Note that it is also possible to use one or more elements included in the respective SP constituent pixels in common among the same type of the SP constituent pixels within the unit U as well as using the signal lines271in common among the same type of SP constituent pixels within the unit U.

For example, it is possible to use the output buffer216provided in a final stage in the first pixel circuit of the pixel121illustrated inFIG.3in common among the same type of the SP constituent pixels within the unit U.

FIG.10illustrates a circuit configuration of the unit U in which the output buffer216is used in common among the same type of the SP constituent pixels within the unit U.

InFIG.10, in place of the output buffers216provided for each pixel, one output buffer216′ to be used in common among four SP constituent pixels A within one unit U are provided.

Further, while illustration of circuits within pixels of the SP constituent pixels B to D is omitted, one output buffer216′ is provided for the same type of four SP constituent pixels for each of the SP constituent pixels B to D in a similar manner.

Note that whileFIG.10illustrates the output buffers216′ outside the unit U to facilitate understanding, the output buffers216′ can be provided within a predetermined SP constituent pixel inside the unit U.

WhileFIG.10illustrates an example where the output buffers216of the respective pixels121are integrated, in a case where each pixel includes other elements such as, for example, computation circuits such as an MUX, a register and an OR circuit, these elements may be used in common among the same type of the SP constituent pixels. In other words, elements to be used in common among the same type of the SP constituent pixels within the unit U are not limited to the output buffer.

<7. Second Pixel Circuit Configuration Example>

FIG.11illustrates a configuration example of a second pixel circuit of the pixel121.

Note that, inFIG.11, the same reference numerals are assigned to parts which are in common with the first pixel circuit illustrated inFIG.3, and description of the parts will be omitted as appropriate.

The pixel121illustrated inFIG.11includes the SPAD211, the transistor212, the transistor213, the inverter214and a transistor311. The transistor213includes an N-type MOS transistor, and the transistors212and311include a P-type MOS transistor.

The second pixel circuit inFIG.11is in common with the first pixel circuit inFIG.3in that the second pixel circuit includes the SPAD211, the transistor212, the transistor213and the inverter214. The second pixel circuit is different from the first pixel circuit in a power supply voltage to be supplied to each element.

More specifically, while the source of the transistor213is connected to the ground in the first pixel circuit, the source of the transistor213is connected to a power supply VNEG1which is a negative bias in the second pixel circuit. The power supply VNEG1is, for example, set at −2 V. Further, the second pixel circuit is constituted so that a voltage between the anode and the cathode of the SPAD211becomes equal to or lower than the breakdown voltage VBD when the transistor213is switched on by the Hi gating control signal VG, and thus, a power supply VSPAD to be supplied to the anode of the SPAD211is set at −22 V which is lower than the potential of the first pixel circuit (in the above-described example, −20 V).

Still further, while the source of the transistor212is connected to the power supply voltage VE (3 V) which is the first power supply voltage in the first pixel circuit, the source of the transistor212is connected to the power supply voltage VDD (1 V) which is the second power supply voltage lower than the first power supply voltage in the second pixel circuit. In a case where the pixel121is controlled to be an active pixel, as a result of the power supply voltage VDD (1 V) being supplied to the cathode of the SPAD211via the transistor311and the transistor212, the voltage between the anode and the cathode of the SPAD211becomes a reverse voltage of 23 V which is the same as that in the first pixel circuit.

Further, the second pixel circuit inFIG.11is different from the first pixel circuit in that the transistor311which includes a P-type MOS transistor is newly added between the SPAD211and the inverter214. More specifically, a drain of the transistor311is connected to the cathode of the SPAD211and the drain of the transistor213, and a source of the transistor311is connected to the drain of the transistor212and the input terminal of the inverter214. A gain of the transistor311is connected to a power supply VNEG2which is a negative bias. The power supply VNEG2is, for example, set at −1 V.

The transistor311which functions as a voltage conversion circuit, converts a signal having the cathode voltage VS of the SPAD211to be supplied to the drain into a signal having a voltage VINin a positive range and outputs the signal to the inverter214. The power supply VNEG2(−1 V) which is the same negative bias (−Vgs) as a transistor threshold of the transistor311is applied to a gate of the transistor311. The transistor311interrupts if the voltage VINwhich is a signal input to the inverter214reaches a voltage value (0 V) which is a value increased from the power supply VNEG2(−1 V) by the transistor threshold. The transistor311therefore also functions as a voltage clamp circuit.

The inverter214outputs a Hi detection signal PFout in a case where the voltage VINinput to the inverter214is Lo, and outputs a Lo detection signal PFout in a case where the voltage VINis Hi. The inverter214is an output unit which outputs a detection signal PFout indicating incidence of a photon on the SPAD211.

FIG.12is a graph illustrating potential change in a case where the pixel121inFIG.11is set as an active pixel, and light is incident.

In a case where light is incident, as illustrated inFIG.12, the cathode voltage VS of the SPAD211fluctuates in a range from the VDD (1 V) to −2 V, but the voltage VINto be input to the inverter214falls within a positive range from the VDD (1 V) to 0 V.

The inverter214outputs an Lo detection signal PFout in a case where the voltage VINto be input is equal to or higher than a predetermined threshold voltage Vth (=VDD/2) and outputs a Hi detection signal PFout in a case where the voltage VINis lower than the predetermined threshold voltage Vth. In the example inFIG.12, a Hi detection signal PFout is output during a period from time t11to time t12.

From the above, the transistor213and the transistor311included in a dashed region321among the second pixel circuit inFIG.11are elements (group) which apply an excess bias higher than the breakdown voltage VBD of the SPAD211by 3 V in a similar manner to the first pixel circuit. Meanwhile, the transistor212and the inverter214included in a dashed-dotted region322are elements (group) which operate at the power supply voltage VDD.

Consequently, in the second pixel circuit, it is possible to eliminate the power supply voltage VE which is a power supply voltage higher than the power supply voltage VDD, and it is possible to reduce the number of elements which require to operate with a high-voltage power supply from four within the region221of the first pixel circuit to two within the region321. Reduction of elements operating with a high-voltage power supply can lead to reduction in the number of parts, reduction in a circuit area, and reduction of power consumption. Reduction of circuits can improve signal characteristics (such as delay and skew) until when the detection signal PFout reaches the time measuring unit114.

<8. Use Example of Ranging System>

FIG.13is a view illustrating a use example of the above-described ranging system11.

The above-described ranging system11can be used in various cases of sensing light such as, for example, visible light, infrared light, ultraviolet light and X-ray as described below.an apparatus which captures an image to be provided for viewing, such as a digital camera and a mobile device with a camera functionan apparatus to be provided for traffic, such as an in-vehicle sensor which captures images of portions in front of, behind, around, interior of, and the like, a monitoring camera which monitors traveling vehicles and roads, and a range sensor which measures a distance between vehicles, and the like for safe driving such as automatic stop, and to recognize a state of a driveran apparatus to be provided for electric appliances such as a TV, a refrigerator and an air conditioner to capture an image of gesture of a user to operate equipment in accordance with the gesturean apparatus to be provided for medical care and health care, such as an endoscope and an apparatus which captures images of vessels by receiving infrared lightan apparatus to be provided for security, such as a security camera for crime prevention and a camera for personal authenticationan apparatus to be provided for beauty care, such as a skin checker which captures an image of skin and a microscope which captures an image of scalpan apparatus to be provided for sports, such as an action camera and a wearable camera for sports usean apparatus to be provided for agriculture, such as a camera for monitoring states of fields and crops
<9. Application Example to Mobile Objects>

The technology (present technology) according to the present disclosure is applicable to a variety of products. For example, the technology according to the present disclosure is implemented as devices mounted on any type of mobile objects such as automobiles, electric vehicles, hybrid electric vehicles, motorcycles, bicycles, personal mobilities, airplanes, drones, ships, and robots.

FIG.14is a block diagram illustrating a schematic configuration example of a vehicle control system which is an example of a mobile object control system to which a technology according to the present disclosure is applicable.

The vehicle control system12000includes a plurality of electronic control units connected to each other via a communication network12001. In the example illustrated inFIG.14, the vehicle control system12000includes a driving system control unit12010, a body system control unit12020, an outside-vehicle information detecting unit12030, an in-vehicle information detecting unit12040, and an integrated control unit12050. In addition, as functional configurations of the integrated control unit12050, a microcomputer12051, a sound/image output section12052, and a vehicle-mounted network interface (I/F)12053are illustrated.

The driving system control unit12010controls the operation of devices related to the driving system of the vehicle in accordance with various kinds of programs. For example, the driving system control unit12010functions as a control device for a driving force generating device for generating the driving force of the vehicle, such as an internal combustion engine, a driving motor, or the like, a driving force transmitting mechanism for transmitting the driving force to wheels, a steering mechanism for adjusting the steering angle of the vehicle, a braking device for generating the braking force of the vehicle, and the like.

The body system control unit12020controls the operation of various kinds of devices provided to a vehicle body in accordance with various kinds of programs. For example, the body system control unit12020functions as a control device for a keyless entry system, a smart key system, a power window device, or various kinds of lamps such as a headlamp, a backup lamp, a brake lamp, a turn signal, a fog lamp, or the like. In this case, radio waves transmitted from a mobile device as an alternative to a key or signals of various kinds of switches can be input to the body system control unit12020. The body system control unit12020receives these input radio waves or signals, and controls a door lock device, the power window device, the lamps, or the like of the vehicle.

The outside-vehicle information detecting unit12030detects information about the outside of the vehicle including the vehicle control system12000. For example, the outside-vehicle information detecting unit12030is connected with an imaging unit12031. The outside-vehicle information detecting unit12030makes the imaging unit12031image an image of the outside of the vehicle, and receives the imaged image. On the basis of the received image, the outside-vehicle information detecting unit12030may perform processing of detecting an object such as a human, a vehicle, an obstacle, a sign, a character on a road surface, or the like, or processing of detecting a distance thereto.

The imaging unit12031is an optical sensor that receives light, and which outputs an electric signal corresponding to a received light amount of the light. The imaging unit12031can output the electric signal as an image, or can output the electric signal as information about a measured distance. In addition, the light received by the imaging unit12031may be visible light, or may be invisible light such as infrared rays or the like.

The in-vehicle information detecting unit12040detects information about the inside of the vehicle. The in-vehicle information detecting unit12040is, for example, connected with a driver state detecting section12041that detects the state of a driver. The driver state detecting section12041, for example, includes a camera that images the driver. On the basis of detection information input from the driver state detecting section12041, the in-vehicle information detecting unit12040may calculate a degree of fatigue of the driver or a degree of concentration of the driver, or may determine whether the driver is dozing.

The microcomputer12051can calculate a control target value for the driving force generating device, the steering mechanism, or the braking device on the basis of the information about the inside or outside of the vehicle which information is obtained by the outside-vehicle information detecting unit12030or the in-vehicle information detecting unit12040, and output a control command to the driving system control unit12010. For example, the microcomputer12051can perform cooperative control intended to implement functions of an advanced driver assistance system (ADAS) which functions include collision avoidance or shock mitigation for the vehicle, following driving based on a following distance, vehicle speed maintaining driving, a warning of collision of the vehicle, a warning of deviation of the vehicle from a lane, or the like.

In addition, the microcomputer12051can perform cooperative control intended for automatic driving, which makes the vehicle to travel autonomously without depending on the operation of the driver, or the like, by controlling the driving force generating device, the steering mechanism, the braking device, or the like on the basis of the information about the outside or inside of the vehicle which information is obtained by the outside-vehicle information detecting unit12030or the in-vehicle information detecting unit12040.

In addition, the microcomputer12051can output a control command to the body system control unit12020on the basis of the information about the outside of the vehicle which information is obtained by the outside-vehicle information detecting unit12030. For example, the microcomputer12051can perform cooperative control intended to prevent a glare by controlling the headlamp so as to change from a high beam to a low beam, for example, in accordance with the position of a preceding vehicle or an oncoming vehicle detected by the outside-vehicle information detecting unit12030.

The sound/image output section12052transmits an output signal of at least one of a sound or an image to an output device capable of visually or auditorily notifying an occupant of the vehicle or the outside of the vehicle of information. In the example ofFIG.14, an audio speaker12061, a display unit12062, and an instrument panel12063are exemplified as the output device. The display unit12062may, for example, include at least one of an on-board display or a head-up display.

FIG.15is a diagram illustrating an example of an installation position of the imaging unit12031.

InFIG.15, a vehicle12100includes imaging units12101,12102,12103,12104, and12105as the imaging unit12031.

imaging units12101,12102,12103,12104, and12105are positioned, for example, at the front nose, a side mirror, the rear bumper, the back door, and the upper part, or the like, of the windshield in the vehicle compartment of the vehicle12100. The imaging unit12101provided to the front nose and the imaging unit12105provided to the upper part of the windshield in the vehicle compartment obtain mainly an image of the front of the vehicle12100. The imaging units12102and12103attached to the side mirrors obtain mainly images of the areas on the sides of the vehicle12100. The imaging unit12104provided to the rear bumper or the back door obtains mainly an image of the rear of the vehicle12100. The image of the front of the vehicle obtained by the imaging units12101and12105is used mainly to detect a preceding vehicle, a pedestrian, an obstacle, a signal, a traffic sign, a lane, or the like.

Additionally,FIG.15illustrates an example of the imaging ranges of the imaging units12101to12104. An imaging range12111represents the imaging range of the imaging unit12101provided to the front nose. Imaging ranges12112and12113respectively represent the imaging ranges of the imaging units12102and12103provided to the side mirrors. An imaging range12114represents the imaging range of the imaging unit12104provided to the rear bumper or the back door. A bird's-eye image of the vehicle12100as viewed from above is obtained by superimposing image data imaged by the imaging units12101to12104, for example.

At least one of the imaging units12101to12104may have a function of obtaining distance information. For example, at least one of the imaging units12101to12104may be a stereo camera constituted of a plurality of imaging elements, or may be an imaging element having pixels for phase difference detection.

For example, the microcomputer12051can determine a distance to each three-dimensional object within the imaging ranges12111to12114and a temporal change in the distance (relative speed with respect to the vehicle12100) on the basis of the distance information obtained from the imaging units12101to12104, and thereby extract, as a preceding vehicle, a nearest three-dimensional object in particular that is present on a traveling path of the vehicle12100and which travels in substantially the same direction as the vehicle12100at a predetermined speed (for example, equal to or more than 0 km/hour). Further, the microcomputer12051can set a following distance to be maintained in front of a preceding vehicle in advance, and perform automatic brake control (including following stop control), automatic acceleration control (including following start control), or the like. It is thus possible to perform cooperative control intended for automatic driving that makes the vehicle travel autonomously without depending on the operation of the driver or the like.

For example, the microcomputer12051can classify three-dimensional object data on three-dimensional objects into three-dimensional object data of a two-wheeled vehicle, a standard-sized vehicle, a large-sized vehicle, a pedestrian, a utility pole, etc., and other three-dimensional objects on the basis of the distance information obtained from the imaging units12101to12104, extract the classified three-dimensional object data, and use the extracted three-dimensional object data for automatic avoidance of an obstacle. For example, the microcomputer12051identifies obstacles around the vehicle12100as obstacles that the driver of the vehicle12100can recognize visually and obstacles that are difficult for the driver of the vehicle12100to recognize visually. Then, the microcomputer12051determines a collision risk indicating a risk of collision with each obstacle. In a situation in which the collision risk is equal to or higher than a set value and there is thus a possibility of collision, the microcomputer12051outputs a warning to the driver via the audio speaker12061or the display unit12062, and performs forced deceleration or avoidance steering via the driving system control unit12010. The microcomputer12051can thereby assist in driving to avoid collision.

At least one of the imaging units12101to12104may be an infrared camera that detects infrared rays. The microcomputer12051can, for example, recognize a pedestrian by determining whether or not there is a pedestrian in imaged images of the imaging units12101to12104. Such recognition of a pedestrian is, for example, performed by a procedure of extracting characteristic points in the imaged images of the imaging units12101to12104as infrared cameras and a procedure of determining whether or not it is the pedestrian by performing pattern matching processing on a series of characteristic points representing the contour of the object. When the microcomputer12051determines that there is a pedestrian in the imaged images of the imaging units12101to12104, and thus recognizes the pedestrian, the sound/image output section12052controls the display unit12062so that a square contour line for emphasis is displayed so as to be superimposed on the recognized pedestrian. Further, the sound/image output section12052may also control the display unit12062so that an icon or the like representing the pedestrian is displayed at a desired position.

In the above, an example of the vehicle control system to which the technology related to the present disclosure can be applied is described. The technology according to the present disclosure can be applied to the imaging unit12031or the like within the above-described configuration. Specifically, for example, the ranging system11illustrated inFIG.1can be applied to the Imaging unit12031. The Imaging unit12031is a LIDAR, for example, and is used for detecting a distance to an object around the vehicle12100and the object. By applying the technology of the present disclosure to the imaging unit12031, the accuracy of detecting the distance to the object around the vehicle12100and the object will be improved. As a result, for example, it becomes possible to issue a warning of collision of the vehicle at an appropriate timing so as to prevent a traffic accident.

Further, in the present specification, a system has the meaning of a set of a plurality of structural elements (such as an apparatus or a module (part)), and does not take into account whether or not all the structural elements are in the same casing. Therefore, the system may be either a plurality of apparatuses stored in separate casings and connected through a network, or an apparatus in which a plurality of modules is stored within a single casing.

Further, an embodiment of the present technology is not limited to the embodiments described above, and various changes and modifications may be made without departing from the scope of the present technology.

Note that the effects described in the present specification are not limiting but are merely examples, and there may be additional effects other than the description in the present specification.

Further, the present technology may also be configured as below.

(1)

A light receiving element including:a pixel array in which a plurality of pixels including SPADs in units of pixel is arranged in a matrix; anda pixel driving unit configured to control respective pixels of the pixel array to be active pixels or non-active pixels,in which the pixel driving unit controls the pixels to be the active pixels in units of spot including N×M pixels (N>0, M>0, where N and M do not become 1 at a same time), andone signal line which outputs a detection signal is disposed at the pixel array for a plurality of spot constituent pixels of a same type within one unit where the one unit includes L×L pixels (L>1).

(2)

The light receiving element according to (1), further including:a wiring which connects a plurality of the spot constituent pixels of a same type within the one unit.

(3)The light receiving element according to (1) or (2), further including:at least one element to be utilized in common among a plurality of the spot constituent pixels of a same type within the one unit.

(4)

The light receiving element according to any one of (1) to (3),in which, in a case where the plurality of spots is set at the pixel array, the pixel driving unit determines a plurality of the spots so that a same type of respective spot constituent pixels included in the spot comes L-th or any later in other adjacent spots both in a horizontal direction and in a vertical direction.

(5)

The light receiving element according to any one of (1) to (4),in which the one unit includes 4×4 pixels, andthe unit of the spot includes 2×2 pixels.

(6)

A ranging system including:an illumination apparatus configured to radiate irradiation light; anda light receiving element configured to receive reflected light of the irradiation light,in which the light receiving element includes:a pixel array in which a plurality of pixels including SPADs in units of pixel is arranged in a matrix; anda pixel driving unit configured to control respective pixels of the pixel array to be active pixels or non-active pixels,the pixel driving unit controls the pixels to be the active pixels in units of spot including N×M pixels (N>0, M>0, where N and M do not become 1 at a same time), andone signal line which outputs a detection signal is disposed at the pixel array for a plurality of spot constituent pixels of a same type within one unit where the one unit includes L×L pixels (L>1).

REFERENCE SIGNS LIST

11Ranging system21Illumination apparatus22Imaging apparatus31Illumination control unit32Light source41Imaging unit42Control unit52Light receiving element53Signal processing circuit111Pixel driving unit112Pixel arrayU (U1to U16) UnitSP (SP1to SP9) Spot121Pixel122Pixel drive line211SPAD212,213Transistor214Inverter215Voltage conversion circuit216,216′ Output buffer241,242Signal line261Vertical wiring271(271A to271D) Signal line311Transistor