Patent Description:
In recent years, distance measurement sensors that perform distance measurement using a Time-of-Flight (ToF) method have attracted attention. Some of such distance measurement sensors use a single photon avalanche diode (SPAD) as a pixel, for example. In the SPAD, if one photon enters a high-field PN junction region in a state in which a voltage larger than a breakdown voltage is applied, avalanche amplification occurs. By detecting a timing at which current instantaneously flows at the time, it is possible to accurately measure a distance.

For example, Patent Document <NUM> discloses a technology of providing measurement pixels and reference pixels in a distance measurement sensor that uses the SPAD, measuring background light intensity by the reference pixels, and changing a bias voltage of the SPAD.

<CIT> describes an optical sensor module for time-of-flight measurement comprising an optical emitter, a main detector and a reference detector which are arranged in or on a carrier. An opaque housing of the optical sensor module has a first chamber and a second chamber which are separated by a light barrier. The housing has a cover section and is arranged on the carrier such that the optical emitter is located inside the first chamber, the main detector is located inside the second chamber and the reference detector is located outside the first chamber. Furthermore, a main surface of the cover section is positioned opposite the carrier. The optical emitter is arranged and configured to emit light through a first aperture in the cover section, and the main detector is arranged and configured to detect light entering the second chamber through a second aperture in the cover section. A reference path is established between the optical emitter and the reference detector inside the optical sensor module, and confined by the main surface of the cover section and the carrier.

<CIT> describes a substrate which supports optical and electrical integration of a high quantum efficiency silicon APD with a gallium nitride (GaN) -VCSEL diode in each pixel to form a compact emitter-detector pixel for passive and active <NUM>-D and <NUM>-D high resolution imaging focal plane arrays.

However, in the technology of Patent Document <NUM>, because background light is used as light to be detected by the reference pixels, uncertainty has remained.

The present technology has been devised in view of such situations, and enables light to be surely received by a reference pixel.

A light receiving device according to the first aspect of the present technology includes a plurality of pixels each including a light receiving element having a light receiving surface, and a light emission source provided on an opposite side of the light receiving surface with respect to the light receiving element, in which the plurality of pixels includes a first pixel including a light shielding member provided between the light receiving element and the light emission source, and a second pixel including a light guiding unit that is configured to propagate a photon and is provided between the light receiving element and the light emission source.

A distance measurement system according to the second aspect of the present technology includes an illumination device configured to emit illumination light, and a light receiving device configured to receive reflected light of the illumination light, in which the light receiving device include a plurality of pixels each including a light receiving element having a light receiving surface, and a light emission source provided on an opposite side of the light receiving surface with respect to the light receiving element, and the plurality of pixels includes a first pixel including a light shielding member provided between the light receiving element and the light emission source, and a second pixel including a light guiding unit that is configured to propagate a photon and is provided between the light receiving element and the light emission source.

In the first to third aspects of the present technology, a plurality of pixels each including a light receiving element having a light receiving surface, and a light emission source provided on an opposite side of the light receiving surface with respect to the light receiving element is provided. The plurality of pixels includes a first pixel including a light shielding member provided between the light receiving element and the light emission source, and a second pixel including a light guiding unit that is configured to propagate a photon and is provided between the light receiving element and the light emission source.

The light receiving device and the distance measurement system may be independent devices, or may be modules incorporated in other devices.

Hereinafter, a mode for carrying out the present technology (hereinafter, referred to as an embodiment) will be described. Note that the description will be given in the following order.

<FIG> is a block diagram illustrating a configuration example of an embodiment of a distance measurement system to which the present technology is applied.

A distance measurement system <NUM> is a system that captures a distance image using a ToF method, for example. Here, the distance image is an image obtained by detecting a distance in a depth direction from the distance measurement system <NUM> to a subject for each pixel. A signal of each pixel includes a distance pixel signal that is based on the detected distance.

The distance measurement system <NUM> includes an illumination device <NUM> and an imaging device <NUM>.

The illumination device <NUM> includes an illumination control unit <NUM> and a light source <NUM>.

Under the control of a control unit <NUM> of the imaging device <NUM>, the illumination control unit <NUM> controls a pattern in which the light source <NUM> emits light. Specifically, in accordance with an emission code included in an emission signal supplied from the control unit <NUM>, the illumination control unit <NUM> controls a pattern in which the light source <NUM> emits light. For example, the emission code includes two values corresponding to <NUM> (High) and <NUM> (Low). When the value of the emission code is <NUM>, the illumination control unit <NUM> turns on the light source <NUM>, and when the value of the emission code is <NUM>, the illumination control unit <NUM> turns off the light source <NUM>.

Under the control of the illumination control unit <NUM>, the light source <NUM> emits light in a predetermined wavelength band. The light source <NUM> includes an infrared laser diode, for example. Note that the type of the light source <NUM> and the wavelength band of illumination light can be arbitrarily set in accordance with a use application or the like of the distance measurement system <NUM>.

The imaging device <NUM> is a device that receives reflected light of light (illumination light) that has been emitted from the illumination device <NUM> and reflected by a subject <NUM>, a subject <NUM>, and the like. The imaging device <NUM> includes an imaging unit <NUM>, the control unit <NUM>, a display unit <NUM>, and a storage unit <NUM>.

The imaging unit <NUM> includes a lens <NUM> and a light receiving device <NUM>.

The lens <NUM> forms an image of incident light on a light receiving surface of the light receiving device <NUM>. Note that a configuration of the lens <NUM> is an arbitrary, and the lens <NUM> may include a plurality of lens units, for example.

The light receiving device <NUM> includes a sensor that uses a single photon avalanche diode (SPAD) as each pixel, for example. Under the control of the control unit <NUM>, the light receiving device <NUM> receives reflected light from the subject <NUM>, the subject <NUM>, and the like, converts a resultant pixel signal into distance information, and outputs the distance information to the control unit <NUM>. The light receiving device <NUM> supplies, to the control unit <NUM> as a pixel value (distance pixel signal) of each pixel of a pixel array in which pixels are two-dimensionally arrayed in a matrix in a row direction and a column direction, a distance image storing a digital count value obtained by counting a time from when the illumination device <NUM> emits illumination light to when the light receiving device <NUM> receives the light. A light emission timing signal indicating a timing at which the light source <NUM> emits light is supplied also to the light receiving device <NUM> from the control unit <NUM>.

Note that, by the distance measurement system <NUM> repeating light emission of the light source <NUM> and reception of the reflected light a plurality of times (for example, several thousands to several tens of thousands of times), the imaging unit <NUM> generates a distance image from which influence of ambient light, multipath, or the like has been removed, and supplies the distance image to the control unit <NUM>.

The control unit <NUM> includes, for example, a control circuit or a processor such as a field programmable gate array (FPGA) or a digital signal processor (DSP), and the like. The control unit <NUM> performs control of the illumination control unit <NUM> and the light receiving device <NUM>. Specifically, the control unit <NUM> supplies an emission signal to the illumination control unit <NUM>, and supplies a light emission timing signal to the light receiving device <NUM>. The light source <NUM> emits illumination light in accordance with the emission signal. The light emission timing signal may be an emission signal supplied to the illumination control unit <NUM>. Furthermore, the control unit <NUM> supplies the distance image acquired from the imaging unit <NUM>, to the display unit <NUM>, and causes the display unit <NUM> to display the distance image. Moreover, the control unit <NUM> causes the storage unit <NUM> to store the distance image acquired from the imaging unit <NUM>. Furthermore, the control unit <NUM> outputs the distance image acquired from the imaging unit <NUM>, to the outside.

The display unit <NUM> includes a panel-shaped display device such as a liquid crystal display device or an organic Electro Luminescence (EL) display device, for example.

The storage unit <NUM> can include an arbitrary storage device or storage medium, or the like, and stores a distance image or the like.

<FIG> is a block diagram illustrating a configuration example of the light receiving device <NUM>.

The light receiving device <NUM> includes a pixel drive unit <NUM>, a pixel array <NUM>, a multiplexer (MUX) <NUM>, a time measurement unit <NUM>, a signal processing unit <NUM>, and an input-output unit <NUM>.

The pixel array <NUM> has a configuration in which pixels <NUM> are two-dimensionally arrayed in a matrix in the row direction and the column direction. Each of the pixels <NUM> detects the entry of a photon, and outputs a detection signal indicating a detection result, as a pixel signal. Here, the row direction refers to an array direction of the pixels <NUM> in a horizontal direction, and the column direction refers to an array direction of the pixels <NUM> in a vertical direction. Due to limitations of space, a pixel array configuration of the pixel array <NUM> that is illustrated in <FIG> includes ten rows and twelve columns, but the number of rows and the number of columns of the pixel array <NUM> are not limited to these, and can be arbitrary set.

For each pixel row, a pixel drive line <NUM> is wired in the horizontal direction to the matrix pixel array of the pixel array <NUM>. The pixel drive line <NUM> transmits a drive signal for driving the pixels <NUM>. The pixel drive unit <NUM> drives each of the pixels <NUM> by supplying a predetermined drive signal to each of the pixels <NUM> via the pixel drive lines <NUM>. Specifically, the pixel drive unit <NUM> performs control in such a manner as to set at least a part of the plurality of pixels <NUM> two-dimensionally arrayed in a matrix, as active pixels, and set the remaining pixels <NUM> as inactive pixels, at a predetermined timing synchronized with a light emission timing signal supplied from the outside via the input-output unit <NUM>. The active pixel is a pixel that detects the entry of a photon, and the inactive pixel is a pixel that does not detect the entry of a photon. As a matter of course, all of the pixels <NUM> of the pixel array <NUM> may be set as active pixels The detailed configuration of the pixels <NUM> will be described later.

Note that <FIG> illustrates the pixel drive line <NUM> as one wire, but the pixel drive line <NUM> may include a plurality of wires. One end of the pixel drive line <NUM> is connected to an output end of the pixel drive unit <NUM> that corresponds to each pixel row.

The MUX <NUM> selects an output from the active pixels in accordance with switching between active pixels and inactive pixels in the pixel array <NUM>. Then, the MUX <NUM> outputs pixel signals input from the selected active pixels, to the time measurement unit <NUM>.

On the basis of pixel signals of active pixels that are supplied from the MUX <NUM>, and a light emission timing signal indicating a light emission timing of the light source <NUM>, the time measurement unit <NUM> generates a count value corresponding to a time from when the light source <NUM> emits light to when active pixels receive the light. The time measurement unit <NUM> is also referred to as a time to digital converter (TDC). The light emission timing signal is supplied from the outside (the control unit <NUM> of the imaging device <NUM>) via the input-output unit <NUM>.

On the basis of the light emission of the light source <NUM> and the reception of the reflected light that are repeatedly executed a predetermined times (for example, several thousands to several tens of thousands of times), the signal processing unit <NUM> creates a histogram indicating a time (count value) until reception of reflected light, for each pixel. Then, by detecting a peak of the histogram, the signal processing unit <NUM> determines a time until light emitted from the light source <NUM> returns by being reflected on the subject <NUM> or the subject <NUM>. The signal processing unit <NUM> generates a distance image storing a digital count value obtained by counting a time until the light receiving device <NUM> receives light, in each pixel, and supplies the distance image to the input-output unit <NUM>. Alternatively, furthermore, the signal processing unit <NUM> may perform calculation for obtaining a distance to an object on the basis of the determined time and a light speed, generate a distance image storing the calculation result in each pixel, and supply the distance image to the input-output unit <NUM>.

The input-output unit <NUM> outputs a signal (distance image signal) of the distance image that is supplied from the signal processing unit <NUM>, to the outside (the control unit <NUM>). Furthermore, the input-output unit <NUM> acquires a light emission timing signal supplied from the control unit <NUM>, and supplies the light emission timing signal to the pixel drive unit <NUM> and the time measurement unit <NUM>.

<FIG> illustrates a circuit configuration example of each of the plurality of pixels <NUM> arrayed in a matrix in the pixel array <NUM>.

The pixel <NUM> in <FIG> includes an SPAD <NUM>, a transistor <NUM>, a switch <NUM>, and an inverter <NUM>. Furthermore, the pixel <NUM> also includes a latch circuit <NUM> and an inverter <NUM>. The transistor <NUM> is formed by a P-type MOS transistor.

A cathode of the SPAD <NUM> is connected to a drain of the transistor <NUM>, and also connected to an input terminal of the inverter <NUM> and one end of the switch <NUM>. An anode of the SPAD <NUM> is connected to a source voltage VA (hereinafter, will also be referred to as an anode voltage VA.

The SPAD <NUM> is a photodiode (single photon avalanche photodiode) that causes avalanche amplification of generated electrons and outputs a signal of a cathode voltage VS, when incident light enters. The source voltage VA supplied to the anode of the SPAD <NUM> is set to a negative bias (negative potential) of about -<NUM> V, for example.

The transistor <NUM> is a constant current source operating in a saturation region, and performs passive quench by functioning as a quenching resistor. A source of the transistor <NUM> is connected to a source voltage VE, and a drain is connected to the cathode of the SPAD <NUM>, the input terminal of the inverter <NUM>, and one end of the switch <NUM>. Therefore, the source voltage VE is supplied also to the cathode of the SPAD <NUM>. A pull-up resistor can also be used in place of the transistor <NUM> connected in series with the SPAD <NUM>.

For detecting light (photon) with sufficient efficiency, a voltage (hereinafter, will be referred to as an excess bias. ) larger than a breakdown voltage VBD of the SPAD <NUM> is applied to the SPAD <NUM>. For example, if the breakdown voltage VBD of the SPAD <NUM> is set to <NUM> V, and a voltage larger to be than the breakdown voltage VBD by <NUM> V is applied, the source voltage VE to be supplied to the source of the transistor <NUM> is set to <NUM> V.

Note that the breakdown voltage VBD of the SPAD <NUM> drastically changes in accordance with a temperature or the like. Therefore, an applied voltage to be applied to the SPAD <NUM> is controlled (adjusted) in accordance with a change of the breakdown voltage VBD. For example, if the source voltage VE is set to a fixed voltage, the anode voltage VA is controlled (adjusted).

One end of both ends of the switch <NUM> is connected to the cathode of the SPAD <NUM>, the input terminal of the inverter <NUM>, and the drain of the transistor <NUM>, and another end is connected to a ground connection line <NUM> connected to a ground (GND). The switch <NUM> can be formed by an N-type MOS transistor, for example, and turns on/off a gating control signal VG being an output of the latch circuit <NUM>, in accordance with a gating inverted signal VG_I inverted by the inverter <NUM>.

On the basis of a trigger signal SET and address data DEC that are supplied from the pixel drive unit <NUM>, the latch circuit <NUM> supplies the gating control signal VG for controlling the pixel <NUM> to become an active pixel or an inactive pixel, to the inverter <NUM>. The inverter <NUM> generates the gating inverted signal VG_I obtained by inverting the gating control signal VG, and supplies the gating inverted signal VG_I to the switch <NUM>.

The trigger signal SET is a timing signal indicating a switching timing of the gating control signal VG, and the address data DEC is data indicating an address of a pixel to be set as an active pixel among the plurality of pixels <NUM> arrayed in the matrix in the pixel array <NUM>. The trigger signal SET and the address data DEC are supplied from the pixel drive unit <NUM> via the pixel drive line <NUM>.

The latch circuit <NUM> reads the address data DEC at a predetermined timing indicated by the trigger signal SET. Then, in a case where pixel addresses indicated by the address data DEC include a pixel address of itself (corresponding pixel <NUM>), the latch circuit <NUM> outputs the gating control signal VG indicating Hi (<NUM>) for setting the corresponding pixel <NUM> as an active pixel. On the other hand, in a case where pixel addresses indicated by the address data DEC do not include a pixel address of itself (corresponding pixel <NUM>), the latch circuit <NUM> outputs the gating control signal VG indicating Lo (<NUM>) for setting the corresponding pixel <NUM> as an inactive pixel. Therefore, in a case where the pixel <NUM> is set as an active pixel, the gating inverted signal VG_I inverted by the inverter <NUM> and indicating Lo (<NUM>) is supplied to the switch <NUM>. On the other hand, in a case where the pixel <NUM> is set as an inactive pixel, the gating inverted signal VG_I indicating Hi (<NUM>) is supplied to the switch <NUM>. Accordingly, in a case where the pixel <NUM> is set as an active pixel, the switch <NUM> is turned off (unconnected), and in a case where the pixel <NUM> is set as an inactive pixel, the switch <NUM> is turned on (connected).

When the cathode voltage VS serving as an input signal indicates Lo, the inverter <NUM> outputs a detection signal PFout indicating Hi, and when the cathode voltage VS indicates Hi, the inverter <NUM> outputs the detection signal PFout indicating Lo. The inverter <NUM> is an output unit that outputs the entry of a photon to the SPAD <NUM>, as the detection signal PFout.

Next, an operation to be performed in a case where the pixel <NUM> is set as an active pixel will be described with reference to <FIG>.

<FIG> is a graph indicating a change of the cathode voltage VS of the SPAD <NUM> and the detection signal PFout that change in accordance with the entry of a photon.

First of all, in a case where the pixel <NUM> is set as an active pixel, the switch <NUM> is turned off as described above.

Because the source voltage VE (for example, <NUM> V) is supplied to the cathode of the SPAD <NUM>, and the source voltage VA (for example, -<NUM> V) is supplied to the anode, an inverse voltage larger than the breakdown voltage VBD (= <NUM> V) is applied to the SPAD <NUM>. The SPAD <NUM> is thereby set to a Geiger mode. In this state, the cathode voltage VS of the SPAD <NUM> is the same as the source voltage VE like the cathode voltage VS at a time t0 in <FIG>, for example.

If a photon enters the SPAD <NUM> set to the Geiger mode, avalanche amplification occurs, and current flows in the SPAD <NUM>.

If avalanche amplification occurs and current flows in the SPAD <NUM> at a time t1 in <FIG>, after the time t1, by current flowing in the SPAD <NUM>, current flows also in the transistor <NUM>, and a voltage drop is caused by resistance components of the transistor <NUM>.

If the cathode voltage VS of the SPAD <NUM> becomes lower than <NUM> V at a time t2, because an anode to cathode voltage of the SPAD <NUM> enters a state of being lower than the breakdown voltage VBD, avalanche amplification stops. Here, an operation of causing a voltage drop by flowing current generated by avalanche amplification, in the transistor <NUM>, and stopping avalanche amplification by causing a state in which the cathode voltage VS is lower than the breakdown voltage VBD, in accordance with the caused voltage drop corresponds to a quench operation.

If avalanche amplification stops, current flowing in the resistor of the transistor <NUM> gradually decreases, and at a time t4, the cathode voltage VS returns to the original source voltage VE again, and a state in which a next new photon can be detected is caused (recharge operation).

The inverter <NUM> outputs the detection signal PFout indicating Lo, when the cathode voltage VS being an input voltage is equal to or larger than a predetermined threshold voltage Vth, and outputs the detection signal PFout indicating Hi, when the cathode voltage VS is smaller than the predetermined threshold voltage Vth. Accordingly, if a photon enters the SPAD <NUM>, avalanche amplification occurs, and the cathode voltage VS drops to fall below the threshold voltage Vth, the detection signal PFout is inverted from a low level to a high level. On the other hand, if avalanche amplification of the SPAD <NUM> converges, and the cathode voltage VS rises to reach the threshold voltage Vth or more, the detection signal PFout is inverted from the high level to the low level.

Note that, in a case where the pixel <NUM> is set as an inactive pixel, the gating inverted signal VG_I indicating Hi (<NUM>) is supplied to the switch <NUM>, and the switch <NUM> is turned on. If the switch <NUM> is turned on, the cathode voltage VS of the SPAD <NUM> is set to <NUM> V. Consequently, because the anode to cathode voltage of the SPAD <NUM> becomes equal to or smaller than the breakdown voltage VBD, a state in which the SPAD <NUM> does not react even if a photon enters the SPAD <NUM> is caused.

In <FIG>, "A" illustrates a plan view of the light source <NUM>.

The light source <NUM> includes a plurality of light emission units <NUM> arrayed in a matrix. The light emission unit <NUM> includes a vertical cavity surface emitting laser (VCSEL), for example. The illumination control unit <NUM> can individually turn on and off the light emission units <NUM> arrayed in a matrix, in accordance with an emission code included in an emission signal supplied from the control unit <NUM>.

In <FIG>, "B" illustrates a plan view of the pixel array <NUM>.

The pixel array <NUM> includes the pixels <NUM> two-dimensionally arrayed in a matrix as described above. Each of the pixels <NUM> is functionally classified into a pixel <NUM>, a pixel 81R, or a pixel 81D.

The pixel <NUM> is a pixel that receives reflected light of light that has been emitted from (the light emission units <NUM> of) the light source <NUM> and reflected by the subject <NUM>, the subject <NUM>, and the like, and is a measurement (distance measurement) pixel for measuring a distance to a subject.

The pixel 81R is a reference pixel used for checking an adequate applied voltage to the SPAD <NUM>, and correcting distance data.

The pixel 81D is a dummy pixel for separating the measurement pixel <NUM> and the reference pixel 81R. The dummy pixel 81D can be a pixel having the same pixel structure as the measurement pixel <NUM>, for example, and being different only in that the dummy pixel 81D is merely not driven. Alternatively, furthermore, the dummy pixel 81D may have the same pixel structure as the measurement pixel <NUM>, and is driven for monitoring an internal voltage.

The numbers of pixels <NUM>, pixels 81R, and pixels 81D are not specifically limited as long as a plurality of measurement pixels <NUM> is arrayed in a matrix, and the dummy pixel 81D is arrayed between the measurement pixels <NUM> and the reference pixel 81R. The measurement pixels <NUM> can be arrayed in N1 x N2 (N1 and N2 are integers equal to or larger than <NUM>), the reference pixels 81R can be arrayed in M1 x M2 (M1 and M2 are integers equal to or larger than <NUM>), and the dummy pixels 81D can be arrayed in L1 x L2 (L1 and L2 are integers equal to or larger than <NUM>).

Furthermore, in the example in <FIG>, a plurality of reference pixels 81R is adjacently arrayed, but the reference pixels 81R may be separately arrayed among the dummy pixels 81D, and the dummy pixel 81D may be arrayed between a pixel 81R and another pixel 81R.

In <FIG>, "A" illustrates a cross-sectional view of the measurement pixel <NUM>.

The pixel <NUM> includes a first substrate <NUM> and a second substrate <NUM> that are bonded to each other. The first substrate <NUM> includes a semiconductor substrate <NUM> containing silicon or the like, and a wiring layer <NUM>. Hereinafter, for clearly distinguishing from a wiring layer <NUM> on the second substrate <NUM> side, which will be described later, the wiring layer <NUM> will be referred to as the sensor side wiring layer <NUM>. The wiring layer <NUM> on the second substrate <NUM> side will be referred to as the logic side wiring layer <NUM>. A surface of the semiconductor substrate <NUM> on which the sensor side wiring layer <NUM> is formed is a front surface, and the back surface on which the sensor side wiring layer <NUM> is not formed, and which is located on the upper side in the drawing corresponds to a light receiving surface that reflected light enters.

A pixel region of the semiconductor substrate <NUM> includes an N well <NUM>, a P-type diffusion layer <NUM>, an N-type diffusion layer <NUM>, a hole storage layer <NUM>, and a high-concentration P-type diffusion layer <NUM>. Then, an avalanche amplification region <NUM> is formed by a depletion layer formed in a region in which the P-type diffusion layer <NUM> and the N-type diffusion layer <NUM> are connected.

The N well <NUM> is formed by impurity concentration of the semiconductor substrate <NUM> being controlled to an n-type, and forms an electric field for transferring electrons generated by photoelectric conversion in the pixel <NUM>, to the avalanche amplification region <NUM>. At the central part of the N well <NUM>, an n-type region <NUM> having higher concentration than the N well <NUM> is formed in contact with the P-type diffusion layer <NUM>, and a potential gradient for causing carriers (electrons) generated in the N well <NUM>, to easily drift from the periphery to the center is formed. Note that, in place of the N well <NUM>, a P well may be formed by controlling impurity concentration of the semiconductor substrate <NUM> to a p-type.

The P-type diffusion layer <NUM> is a high-concentration P-type diffusion layer (P+) formed over the entire surface of the pixel region in a planar direction. The N-type diffusion layer <NUM> is a high-concentration N-type diffusion layer (N+) existing near the front surface of the semiconductor substrate <NUM>, and formed over the entire surface of the pixel region similarly to the P-type diffusion layer <NUM>. The N-type diffusion layer <NUM> is a contact layer connecting with a contact electrode <NUM> serving as a cathode electrode for supplying a negative voltage for forming the avalanche amplification region <NUM>, and has a protruding shape partially formed up to the contact electrode <NUM> on the front surface of the semiconductor substrate <NUM>.

The hole storage layer <NUM> is a P-type diffusion layer (P) formed in such a manner as to surround the side surfaces and the bottom surface of the N well <NUM>, and stores holes. Furthermore, the hole storage layer <NUM> is connected with the high-concentration P-type diffusion layer <NUM> electrically connected with a contact electrode <NUM> serving as an anode electrode of the SPAD <NUM>.

The high-concentration P-type diffusion layer <NUM> is a high-concentration P-type diffusion layer (P++) existing near the front surface of the semiconductor substrate <NUM> and formed in such a manner as to surround the outer periphery of the N well <NUM>, and forms a contact layer for electrically connecting the hole storage layer <NUM> with the contact electrode <NUM> of the SPAD <NUM>.

In a pixel boundary portion of the semiconductor substrate <NUM> that serves as a boundary with a neighboring pixel, a pixel separation unit <NUM> for separating pixels is formed. The pixel separation unit <NUM> may include only an insulation layer, for example, or may have a double structure in which an insulation layer containing SiO2 or the like covers the outer side (the N well <NUM> side) of a metal layer containing tungsten or the like.

In the sensor side wiring layer <NUM>, the contact electrodes <NUM> and <NUM>, metal wires <NUM> and <NUM>, contact electrodes <NUM> and <NUM>, and metal wires <NUM> and <NUM> are formed.

The contact electrode <NUM> connects the N-type diffusion layer <NUM> and the metal wire <NUM>, and the contact electrode <NUM> connects the high-concentration P-type diffusion layer <NUM> and the metal wire <NUM>.

The metal wire <NUM> is formed to be wider than the avalanche amplification region <NUM> in such a manner as to cover at least the avalanche amplification region <NUM> in a planar region. Furthermore, the metal wire <NUM> may have a structure for causing light having passed through the pixel region of the semiconductor substrate <NUM>, to be reflected toward the semiconductor substrate <NUM> side.

The metal wire <NUM> is formed in such a manner as to overlap with the high-concentration P-type diffusion layer <NUM> and surround the outer periphery of the metal wire <NUM> in the planar region.

The contact electrode <NUM> connects the metal wire <NUM> and the metal wire <NUM>, and the contact electrode <NUM> connects the metal wire <NUM> and the metal wire <NUM>.

On the other hand, the second substrate <NUM> includes a semiconductor substrate <NUM> containing silicon or the like, and the wiring layer <NUM> (the logic side wiring layer <NUM>).

On the front surface side of the semiconductor substrate <NUM> that corresponds to the upper side in the drawing, a plurality of MOS transistors Tr (Tr1, Tr2, etc.) is formed, and the logic side wiring layer <NUM> is formed.

The logic side wiring layer <NUM> includes metal wires <NUM> and <NUM>, metal wires <NUM> and <NUM>, and contact electrodes <NUM> and <NUM>.

The metal wire <NUM> is electrically and physically connected with the metal wire <NUM> of the sensor side wiring layer <NUM> by metal bonding of Cu-Cu or the like. The metal wire <NUM> is electrically and physically connected with the metal wire <NUM> of the sensor side wiring layer <NUM> by metal bonding of Cu-Cu or the like.

The logic side wiring layer <NUM> further includes a multilayer metal wire <NUM> between the layer of the metal wires <NUM> and <NUM>, and the semiconductor substrate <NUM>.

A logic circuit corresponding to the pixel drive unit <NUM>, the MUX <NUM>, the time measurement unit <NUM>, the signal processing unit <NUM>, and the like is formed in the second substrate <NUM> by the plurality of MOS transistors Tr formed on the semiconductor substrate <NUM>, and the multilayer metal wire <NUM>.

For example, via the logic circuit formed on the second substrate <NUM>, the source voltage VE to be applied the N-type diffusion layer <NUM> is supplied to the N-type diffusion layer <NUM> via the metal wires <NUM>, the contact electrode <NUM>, the metal wires <NUM> and <NUM>, the contact electrode <NUM>, the metal wire <NUM>, and the contact electrode <NUM>. Furthermore, the source voltage VA is supplied to the high-concentration P-type diffusion layer <NUM> via the metal wire <NUM>, the contact electrode <NUM>, the metal wires <NUM> and <NUM>, the contact electrode <NUM>, the metal wire <NUM>, and the contact electrode <NUM>. Note that, in a case where a P well obtained by controlling impurity concentration of the semiconductor substrate <NUM> to a p-type is formed in place of the N well <NUM>, a voltage to be applied to the N-type diffusion layer <NUM> becomes the source voltage VA, and a voltage to be applied to the high-concentration P-type diffusion layer <NUM> becomes the source voltage VE.

The cross-sectional structure of the measurement pixel <NUM> has the above-described configuration, and the SPAD <NUM> serving as a light receiving element includes the N well <NUM> of the semiconductor substrate <NUM>, the P-type diffusion layer <NUM>, the N-type diffusion layer <NUM>, the hole storage layer <NUM>, and the high-concentration P-type diffusion layer <NUM>, and the hole storage layer <NUM> is connected with the contact electrode <NUM> serving as an anode electrode, and the N-type diffusion layer <NUM> is connected with the contact electrode <NUM> serving as a cathode electrode.

At least one layer of the metal wires <NUM>, <NUM>, <NUM>, <NUM>, <NUM> to <NUM>, or <NUM> serving as a light shielding member is disposed between the semiconductor substrate <NUM> of the first substrate <NUM> and the semiconductor substrate <NUM> of the second substrate <NUM> in all regions in the planar direction of the pixel <NUM>. Therefore, even in a case where light is emitted by hot carries of the MOS transistor Tr of the semiconductor substrate <NUM> of the second substrate <NUM>, the light is configured not to reach the N well <NUM> and the n-type region <NUM> of the semiconductor substrate <NUM> serving as a photoelectric conversion region.

In the pixel <NUM>, the SPAD <NUM> serving as a light receiving element has a light receiving surface including planes of the N well <NUM> and the hole storage layer <NUM>, and the MOS transistor Tr serving as a light emission source that performs hot carrier light emission is provided on the opposite side of the light receiving surface of the SPAD <NUM>. Then, the metal wire <NUM> and the metal wire <NUM> serving as a light shielding member are provided between the SPAD <NUM> serving as a light receiving element, and the MOS transistor Tr serving as a light emission source, and hot carrier light emission is configured not to reach the N well <NUM> and the n-type region <NUM> of the semiconductor substrate <NUM> serving as a photoelectric conversion region.

A pixel structure of the dummy pixel 81D is formed by the same structure as the measurement pixel <NUM>.

In <FIG>, "B" illustrates a cross-sectional view of the reference pixel 81R.

Note that, in "B" of <FIG>, parts corresponding to "A" of <FIG> are assigned the same reference numerals, and the description thereof will be appropriately omitted.

The cross-sectional structure of the reference pixel 81R illustrated in "B" of <FIG> is different from that of the measurement pixel <NUM> illustrated in "A" of <FIG> in that a light guiding unit <NUM> that propagates light (photon) generated by hot carrier light emission is provided between the SPAD <NUM> serving as a light receiving element and the MOS transistor Tr serving as a light emission source that performs hot carrier light emission.

More specifically, in a part of regions of all regions in the planar direction between the semiconductor substrate <NUM> of the first substrate <NUM> and the semiconductor substrate <NUM> of the second substrate <NUM> of the pixel 81R, a region in which none of the metal wires <NUM>, <NUM>, <NUM>, <NUM>, <NUM> to <NUM>, and <NUM> that shield light is formed is provided, and the light guiding unit <NUM> that propagates light is formed in a stack direction of metal wires.

Therefore, as for a position in the planar direction, if hot carrier light emission occurs in the MOS transistor Tr1 formed at a position overlapping the light guiding unit <NUM> at least partially, the SPAD <NUM> of the pixel 81R can receive light generated by hot carrier light emission and having passed through the light guiding unit <NUM>, and output a detection signal (pixel signal). Note that all the metal wires <NUM>, <NUM>, and the like need not be completely opened as described above, and the light guiding unit <NUM> is only required to be opened to such an extent that light passes through.

Furthermore, on the top surface of the hole storage layer <NUM> being the light receiving surface side of the pixel 81R, a light shielding member (light shielding layer) <NUM> is formed in such a manner as to surround the light receiving surface of the hole storage layer <NUM>. The light shielding member <NUM> shields ambient light or the like that enters from the light receiving surface side. Note that, because the influence of ambient light or the like can be removed by generation processing of a histogram as described above, the light shielding member <NUM> is not essential and can be omitted.

The MOS transistor Tr1 that emits light propagating through the light guiding unit <NUM> and reaching the photoelectric conversion region of the pixel 81R may be a MOS transistor provided as a light emission source as a circuit element not provided in the measurement pixel <NUM>, or may be a MOS transistor formed also in the measurement pixel <NUM>.

Accordingly, in a case where the MOS transistor Tr1 is provided as a light emission source peculiarly in the reference pixel 81R, a circuit in the pixel region formed in the second substrate <NUM> is different between the reference pixel <NUM> and the measurement pixel <NUM>. In this case, the MOS transistor Tr1 peculiarly provided as a light emission source corresponds to a circuit that controls the light emission source, for example.

A light emission timing at which the MOS transistor Tr1 peculiarly provided as a light emission source is caused to emit light can be set to the same timing as a timing at which the light emission units <NUM> of the light source <NUM> emit light, for example. In this case, for example, by setting a timing at which the reference pixel 81R receives light from the light emission source (MOS transistor Tr1), as a reference of a distance zero, it is possible to correct a distance to be calculated from a timing at which the measurement pixel <NUM> receives light. In other words, the reference pixel 81R can be used for correcting distance data.

Furthermore, for example, the reference pixel 81R can be used for checking adequateness of an applied voltage to the SPAD <NUM>. In this case, in the pixel 81R, the MOS transistor Tr1 peculiarly provided as a light emission source is caused to emit light, and the cathode voltage VS of the SPAD <NUM> at the time of a quench operation, that is to say, the cathode voltage VS at the time t2 in <FIG> can be checked and used for adjusting the anode voltage VA.

On the other hand, in a case where the MOS transistor Tr1 serving as a light emission source is a MOS transistor formed also in the measurement pixel <NUM>, a circuit in the pixel region formed in the second substrate <NUM> can be made the same between the reference pixel <NUM> and the measurement pixel <NUM>.

Note that the light emission source of the reference pixel 81R is not limited to a MOS transistor, and may be another circuit element such as a diode or a resistor element.

Furthermore, the light receiving device <NUM> has a stack structure in which the first substrate <NUM> and the second substrate <NUM> are bonded to each other as described above, but may include a single substrate (semiconductor substrate), or may have a stack structure of three or more substrates. Moreover, a back side light receiving sensor structure in which the back surface side of the first substrate <NUM> that is opposite to the front surface on which the sensor side wiring layer <NUM> is formed is regarded as a light receiving surface is employed, but a front side light receiving sensor structure may be employed.

<FIG> illustrates a configuration example of a light source and a pixel array in another distance measurement system according to a comparative example to be compared with the structures of the light source <NUM> and the pixel array <NUM> of the distance measurement system <NUM>.

A light source <NUM> in <FIG> includes a plurality of light emission units <NUM> arrayed in a matrix, and a plurality of light emission units 411R. The light emission units <NUM> and the light emission units 411R each include a vertical cavity surface emitting laser (VCSEL), for example, similarly to the light emission units <NUM> of the light source <NUM>.

As compared with the configuration of the light source <NUM> of the distance measurement system <NUM> illustrated in <FIG>, the light emission units <NUM> correspond to the light emission units <NUM>, and the light source <NUM> further includes the light emission units 411R in addition to the light emission units <NUM>. The light emission units 411R are reference light emission units <NUM> provided for emitting light onto reference pixels 412R of a pixel array <NUM>.

In the pixel array <NUM> in <FIG>, measurement pixels <NUM>, reference pixels 412R, and dummy pixels 412D are arrayed in an alignment similar to that of the pixel array <NUM> in <FIG>. Nevertheless, all of the pixel structures of the pixels <NUM>, the pixels 412R, and the pixels 412D have the same structure as the structure of the measurement pixel <NUM> illustrated in "A" of <FIG>.

More specifically, similarly to the measurement pixel <NUM>, the reference pixel 412R has a configuration in which the reference pixel 412R includes a light shielding member that shields light emitted by hot carrier, in such a manner as not to reach a photoelectric conversion region, between the SPAD <NUM> and the MOS transistor Tr serving as a light emission source, and light emitted from the reference light emission units 411R is received from the light receiving surface side.

In such a configuration, as compared with the distance measurement system <NUM> illustrated in <FIG>, because the light emission units 411R for the reference pixels 412R are additionally required, a mounting area of the light emission units 411R is required, and power for driving the light emission units 411R increases. Power consumption accordingly increases as well. Furthermore, an optical axis needs to be adjusted in such a manner that light emitted from the light emission units 411R is received by the reference pixels 412R, and such a configuration is susceptible to an optical axis deviation.

In contrast to this, according to the structures of the light source <NUM> and the pixel array <NUM> of the distance measurement system <NUM>, because the light emission units 411R for the reference pixels 412R become unnecessary, not only power saving can be achieved but also adjustment of an optical axis deviation becomes unnecessary. Then, because a light emission source is provided in the pixel region of the reference pixel 81R, specifically, provided on the opposite side of the light receiving surface of the SPAD <NUM>, and the light guiding unit <NUM> that propagates light is provided, light can be surely received.

<FIG> is a cross-sectional view illustrating another array example of pixels in the pixel array <NUM>.

In the cross-sectional view of <FIG>, parts corresponding to <FIG> are assigned the same reference numerals. The structure illustrated in <FIG> is further simplified, and a part of the reference numerals is omitted.

In the array example of the pixel array <NUM> illustrated in <FIG>, the reference pixels 81R are arranged on a pixel row or a pixel column separated from the measurement pixels <NUM> over the dummy pixels 81D, but the reference pixels 81R and the measurement pixels <NUM> may be arranged on the same pixel row or pixel column.

The cross-sectional view of <FIG> illustrates a cross-sectional view of the pixels <NUM> arranged on one pixel row or pixel column.

As illustrated in <FIG>, the reference pixels 81R and the measurement pixels <NUM> can be arranged on the same pixel row or pixel column. Also in this case, it is desirable that the dummy pixel 81D is arranged between the reference pixel 81R and the measurement pixel <NUM>. Therefore, even in a case where light from the MOS transistor Tr serving as a light emission source of the reference pixel 81R leaks to a neighboring pixel <NUM>, the influence on the measurement pixel <NUM> can be suppressed. Note that the dummy pixel 81D between the reference pixel 81R and the measurement pixel <NUM> may be omitted.

The application of the present technology is not limited to application to a distance measurement system. More specifically, the present technology can be applied to general electronic devices such as a smartphone, a tablet terminal, a mobile phone, a personal computer, a game machine, a television receiver, a wearable terminal, a digital still camera, or a digital video camera, for example. The above-described imaging unit <NUM> may have a module configuration in which the lens <NUM> and the light receiving device <NUM> are collectively packaged, or may have a configuration in which the lens <NUM> and the light receiving device <NUM> are separately formed, and only the light receiving device <NUM> is formed as one chip.

<FIG> is a diagram illustrating a usage example of the above-described distance measurement system <NUM> or the light receiving device <NUM>.

The above-described distance measurement system <NUM> can be used in various cases of sensing light such as visible light, infrared light, ultraviolet, or an X-ray, for example, as described below.

The technology according to the present disclosure (present technology) can be applied to various products. For example, the technology according to the present disclosure can be implemented as a device mounted on a movable body of any type of an automobile, an electric car, a hybrid electric car, a motorbike, a bicycle, a personal mobility, a plane, a drone, a ship, a robot, and the like.

<FIG> is a block diagram illustrating a schematic configuration example of a vehicle control system being an example of a movable body control system to which the technology according to the present disclosure can be applied.

A vehicle control system <NUM> includes a plurality of electronic control units connected via a communication network <NUM>. In the example illustrated in <FIG>, the vehicle control system <NUM> includes a drive system control unit <NUM>, a body system control unit <NUM>, a vehicle exterior information detection unit <NUM>, a vehicle interior information detection unit <NUM>, and an integrated control unit <NUM>. Furthermore, as functional configurations of the integrated control unit <NUM>, a microcomputer <NUM>, a voice/image output unit <NUM>, and an in-vehicle network interface (I/F) <NUM> are illustrated.

The drive system control unit <NUM> controls operations of a device related to a drive system of a vehicle in accordance with various programs. For example, the drive system control unit <NUM> functions as a control device of a drive force generation device for generating drive force of a vehicle, such as an internal-combustion engine or a driving motor, a drive force transmission mechanism for transmitting drive force to wheels, a steering mechanism for adjusting a steering angle of the vehicle, a braking device for generating braking force of the vehicle, and the like.

The body system control unit <NUM> controls operations of various devices provided in a vehicle body, in accordance with various programs. For example, the body system control unit <NUM> functions as a control device of a keyless entry system, a smart key system, a powered window device, or various lamps such as a headlamp, a back lamp, a brake lamp, a blinker, or a fog lamp. In this case, radio waves transmitted from a mobile device substituting for a key, or signals of various switches can be input to the body system control unit <NUM>. The body system control unit <NUM> receives input of these radio waves or signals, and controls a door lock device of the vehicle, the powered window device, lamps, and the like.

The vehicle exterior information detection unit <NUM> detects information regarding the outside of the vehicle on which the vehicle control system <NUM> is mounted. For example, an imaging unit <NUM> is connected to the vehicle exterior information detection unit <NUM>. The vehicle exterior information detection unit <NUM> causes the imaging unit <NUM> to capture an image of the outside of the vehicle, and receives the captured image. On the basis of the received image, the vehicle exterior information detection unit <NUM> may perform object detection processing or distance detection processing of a human, a car, an obstacle, a road sign, characters on a road, and the like.

The imaging unit <NUM> is an optical sensor that receives light and outputs an electrical signal corresponding to a light reception amount of the light. The imaging unit <NUM> can output an electrical signal as an image, and output an electrical signal as information regarding distance measurement. Furthermore, light to be received by the imaging unit <NUM> may be visible light, or may be invisible light such as infrared light.

The vehicle interior information detection unit <NUM> detects information regarding the vehicle interior. For example, a driver state detection unit <NUM> that detects a state of a driver is connected to the vehicle interior information detection unit <NUM>. The driver state detection unit <NUM> includes a camera for capturing an image of a driver, for example. On the basis of detection information input from the driver state detection unit <NUM>, the vehicle interior information detection unit <NUM> may calculate a fatigue degree or a concentration degree of the driver, or may determine whether or not the driver dozes off.

On the basis of information regarding the vehicle interior or vehicle exterior that is acquired by the vehicle exterior information detection unit <NUM> or the vehicle interior information detection unit <NUM>, the microcomputer <NUM> can calculate control target values of the drive force generation device, the steering mechanism, or the braking device, and output a control command to the drive system control unit <NUM>. For example, the microcomputer <NUM> can perform cooperative control intended to implement functions of an advanced driver assistance system (ADAS) including collision avoidance or shock mitigation of the vehicle, follow-up driving that is based on an inter-vehicular distance, maintained vehicle speed driving, collision warning of the vehicle, lane deviation warning of the vehicle, or the like.

Furthermore, the microcomputer <NUM> can perform cooperative control intended for automated driving of autonomously driving without depending on the operation of a driver, or the like, by controlling the drive force generation device, the steering mechanism, the braking device, or the like on the basis of information regarding the periphery of the vehicle that is acquired by the vehicle exterior information detection unit <NUM> or the vehicle interior information detection unit <NUM>.

Furthermore, the microcomputer <NUM> can output a control command to the body system control unit <NUM> on the basis of information regarding the vehicle exterior that is acquired by the vehicle exterior information detection unit <NUM>. For example, the microcomputer <NUM> can perform cooperative control intended to achieve antidazzle by controlling a headlamp in accordance with a position of a leading vehicle or an oncoming vehicle that has been detected by the vehicle exterior information detection unit <NUM>, and switching high beam to low beam, or the like.

The voice/image output unit <NUM> transmits an output signal of at least one of voice or an image to an output device that can visually or aurally notify an occupant of the vehicle or the vehicle exterior of information. In the example in <FIG>, an audio speaker <NUM>, a display unit <NUM>, and an instrument panel <NUM> are exemplified as output devices. The display unit <NUM> may include at least one of an onboard display or a headup display, for example.

<FIG> is a diagram illustrating an example of an installation position of the imaging unit <NUM>.

In <FIG>, a vehicle <NUM> includes imaging units <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> as the imaging unit <NUM>.

The imaging units <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are provided at positions such as a front nose of the vehicle <NUM>, side mirrors, a rear bumper, a backdoor, and an upper part of a front window inside a vehicle room, for example. The imaging unit <NUM> provided at the front nose and the imaging unit <NUM> provided at the upper part of the front window inside the vehicle room mainly acquire images of a front side of the vehicle <NUM>. The imaging units <NUM> and <NUM> provided at the side mirrors mainly acquire images of the sides of the vehicle <NUM>. The imaging unit <NUM> provided at the rear bumper or the backdoor mainly acquires images of the back side of the vehicle <NUM>. The images of the front side that are acquired by the imaging units and <NUM> and <NUM> are mainly used for the detection of a leading vehicle, a pedestrian, an obstacle, a traffic light, a traffic sign, a traffic lane, or the like.

Note that <FIG> illustrates an example of image capturing ranges of the imaging units <NUM> to <NUM>. An image capturing range <NUM> indicates an image capturing range of the imaging unit <NUM> provided at the front nose, image capturing ranges <NUM> and <NUM> respectively indicate image capturing ranges of the imaging units <NUM> and <NUM> provided at the side mirrors, and an image capturing range <NUM> indicates an image capturing range of the imaging unit <NUM> provided at the rear bumper or the backdoor. For example, a birds-eye image of the vehicle <NUM> viewed from above is obtained by overlapping image data captured by the imaging units <NUM> to <NUM>.

At least one of the imaging units <NUM> to <NUM> may have a function of acquiring distance information. For example, at least one of the imaging units <NUM> to <NUM> may be a stereo camera including a plurality of image sensors, or may be an image sensor including pixels for phase difference detection.

For example, by obtaining a distance to each three-dimensional object in the image capturing ranges <NUM> to <NUM>, and a temporal variation (relative speed with respect to the vehicle <NUM>) of the distance, on the basis of distance information acquired from the imaging units <NUM> to <NUM>, the microcomputer <NUM> can especially extract, as a leading vehicle, a three-dimensional object that is the closest three-dimensional object existing on a travelling path of the vehicle <NUM>, and is running at a predetermined speed (for example, equal to or larger than <NUM>/h) in substantially the same direction as the vehicle <NUM>. Moreover, the microcomputer <NUM> can preliminarily set an inter-vehicular distance to be ensured in front of a leading vehicle, and perform automatic brake control (including follow-up stop control), automatic acceleration control (including follow-up departure control), and the like. In this manner, cooperative control intended for automated driving of autonomously driving without depending on the operation of a driver, or the like can be performed.

For example, on the basis of distance information acquired from the imaging units <NUM> to <NUM>, the microcomputer <NUM> can extract three-dimensional object data regarding a three-dimensional object, while classifying three-dimensional objects into other three-dimensional objects such as a two-wheeled vehicle, a standard-sized vehicle, a large-sized vehicle, a pedestrian, and a telephone pole, and use the extracted three-dimensional object data for automatic avoidance of an obstacle. For example, the microcomputer <NUM> identifies obstacles near the vehicle <NUM>, as an obstacle visible by a driver of the vehicle <NUM>, and an obstacle less-visible by the driver. Then, the microcomputer <NUM> determines collision risk indicating a degree of risk of collision with each obstacle, and when the collision risk is equal to or larger than a setting value and there is a possibility of collision, the microcomputer <NUM> can perform drive assist for collision avoidance by outputting a warning to the driver via the audio speaker <NUM> or the display unit <NUM>, and performing forced deceleration or avoidance steering via the drive system control unit <NUM>.

At least one of the imaging units <NUM> to <NUM> may be an infrared camera that detects infrared light. For example, the microcomputer <NUM> can recognize a pedestrian by determining whether or not a pedestrian exists in captured images of the imaging units <NUM> to <NUM>. The recognition of a pedestrian is performed by a procedure of extracting feature points in captured images of the imaging units <NUM> to <NUM> serving as infrared cameras, and a procedure of determining whether or not a detected object is a pedestrian, by performing pattern matching processing on a series of feature points indicating an outline of the object, for example. If the microcomputer <NUM> determines that a pedestrian exists in captured images of the imaging units <NUM> to <NUM>, and recognizes the pedestrian, the voice/image output unit <NUM> controls the display unit <NUM> to display a rectangular profile line for enhancement, with being superimposed on the recognized pedestrian. Furthermore, the voice/image output unit <NUM> may control the display unit <NUM> to display an icon indicating the pedestrian, or the like at a desired position.

Heretofore, an example of the vehicle control system to which the technology according to the present disclosure can be applied has been described. The technology according to the present disclosure can be applied to the imaging unit <NUM> or the like among the configurations described above. Specifically, for example, the distance measurement system <NUM> in <FIG> can be applied to the imaging unit <NUM>. The imaging unit <NUM> is a LIDAR, for example, and is used for detecting an object near the vehicle <NUM> and a distance to the object. By applying the technology according to the present disclosure to the imaging unit <NUM>, detection accuracy of an object near the vehicle <NUM> and a distance to the object enhances. Consequently, for example, it becomes possible to perform collision warning of a vehicle at an appropriate timing, and prevent a traffic accident.

Note that, in this specification, a system means a set of a plurality of constituent elements (apparatuses, modules (parts), and the like), and it does not matter whether or not all the constituent elements are provided in the same casing. Thus, a plurality of apparatuses stored in separate casings and connected via a network, and a single apparatus in which a plurality of modules is stored in a single casing are both regarded as systems.

Claim 1:
A light receiving device (<NUM>) for a distance measurement system (<NUM>) configured to capture a distance image of a subject (<NUM>, <NUM>) by emitting light from an illumination device (<NUM>) comprising a light source (<NUM>), and receiving reflected light from the subject (<NUM>, <NUM>), the light receiving device (<NUM>) comprising:
a plurality of pixels (<NUM>) each including
a semiconductor substrate (<NUM>, <NUM>), the semiconductor substrate (<NUM>, <NUM>) including
a light receiving surface (<NUM>) configured to receive light reflected by the subject (<NUM>, <NUM>),
a light receiving element (<NUM>) formed on the light receiving surface (<NUM>) of the semiconductor substrate (<NUM>, <NUM>), and
a light emission source (Tr) provided on an opposite surface side of the semiconductor substrate (<NUM>, <NUM>) with respect to the light receiving surface,
characterised in that
the plurality of pixels (<NUM>) includes
a first pixel (<NUM>) including a light shielding member (<NUM>, <NUM>) provided between the light receiving element (<NUM>) and the light emission source (Tr), and
a second pixel (81R) including a light guiding unit (<NUM>) that is configured to propagate a photon and is provided between the light receiving element (<NUM>) and the light emission source (Tr).