Patent Description:
An active pixel sensor (pixel) includes a photoelectric conversion element and an active pixel circuit. The photoelectric conversion element converts electromagnetic radiation impinging onto a detection area into an electronic sensor signal, e.g. a photocurrent.

The active pixel circuit sets the operation mode for the photoelectric conversion element and determines which information conveyed by the incoming radiation is exploited and transmitted to a target device receiving and processing a pixel signal output by the active pixel sensor. For example, the active pixel circuit may be capable of facilitating radiation intensity processing, detection of radiation intensity changes, and/or detection of single events, e.g. for time-of-flight distance measurements. Accordingly, the active pixel circuit outputs a pixel signal that may contain information about the intensity of the incoming radiation and/or about the degree to which the incoming radiation changes. Alternatively or in addition, the active pixel circuit may simply indicate whether or not radiation has been received or when radiation has been received.

A light receiving apparatus such as a solid-state imaging device or a distance measuring apparatus may include a pixel substrate and a logic substrate. The pixel substrate integrates a plurality of active photoelectric conversion elements and, if applicable, at least some elements of the active pixel circuits. The logic substrate may include logic circuits that receive and process the electric signals output by the active pixel circuit and, if applicable, further elements of the active pixel circuits.

It is desirable to increase reliability of pixel substrates and light receiving apparatuses and to simplify the integration of a pixel substrate and a logic substrate in a light receiving apparatus.

<CIT> relates to an image sensor pixel among an array of pixels in an image sensor, comprising a charge multiplying photoconversion element, and a charge storage element electrically connected to the charge multiplying photoconversion element, and a protection circuit electrically connected to the charge storage element for limiting a voltage which accumulates at the charge storage element.

<CIT> relates to a solid-state imaging element comprising a plurality of photoelectric conversion elements each of which photoelectrically converts incident light to generate a first electric signal, and a detection unit that detects whether or not a change amount of the first electric signal of each of the plurality of photoelectric conversion elements exceeds a predetermined threshold and outputs a detection signal indicating a result of the detection.

A pixel substrate includes one or more photoelectric conversion elements, at least some elements of one or more active pixel modules, and at least two electric terminals as electric interface to a logic substrate. Through a first supply terminal the pixel substrate may receive a positive supply voltage for the elements of the active pixel modules formed on the pixel substrate. A reference voltage terminal may pass a reference voltage between the pixel substrate and the logic substrate. A signal output terminal passes an output signal from the pixel substrate to the logic substrate. When the pixel substrate is powered on, a positive supply voltage is supplied from the logic substrate to the pixel substrate through the first supply terminal.

When the logic substrate does not supply the positive supply voltage, the pixel substrate is powered off. When the pixel substrate is powered off and radiation impinges on detection areas of the photoelectric conversion elements, electric potential differences may occur between terminals of the pixel substrate. The present embodiments mitigate shortcomings of conventional pixel substrates in that a protection circuit limits a voltage appearing between the first supply terminal and the reference voltage terminal when the pixel substrate is powered off and at the same time radiation impinges on the detection area.

Accordingly, a pixel substrate and a light receiving apparatus according to the main embodiments of the invention are defined by the appended independent claims. The appended dependent claims define further embodiments.

In particular, the first supply line may be electrically connected to a first supply terminal, the substrate region may be electrically connected to a voltage reference terminal, and a voltage between the first supply line and the voltage reference terminal may fall below the negative threshold voltage when the pixel substrate is powered off and at the same time radiation impinges onto the photoelectric conversion element.

The photocurrent through the photoelectric conversion element and/or the charge transfer induced by the photocurrent may have the effect that at least one circuit element electrically connected in series between the first supply line and the photoelectric conversion element at least partly turns on and a negative quiescent voltage is present between the first supply terminal and the voltage reference terminal. The negative voltage may damage circuit elements formed on the logic substrate and/or may complicate the adaption of the logic substrate to the pixel substrate.

In the pixel circuit of the present disclosure, when the pixel substrate is powered off and at the same time radiation impinges onto the photoelectric conversion element, the protection circuit short-circuits the first supply line and the substrate region when the voltage between the first supply line and the substrate region falls below a negative threshold voltage. The protection circuit may be self-powered.

Embodiments for implementing techniques of the present disclosure (hereinafter referred to as "embodiments") will be described below in detail using the drawings. The techniques of the present disclosure are not limited to the embodiments, and various numerical values and the like in the embodiments are illustrative. In the following description, the same elements or elements with the same functions are denoted by the same reference signs, and duplicate descriptions are omitted.

Electrically connected electronic elements may be electrically connected through a direct, permanent low-resistive connection, e.g., through a conductive line. The term "electrically connected" may also include a connection through other electronic elements provided and suitable for permanent and/or temporary signal transmission and/or transmission of energy. For example, electronic elements may also be electrically connected through electronic switches such as transistors or transistor circuits, e.g. MOSFETs, transmission gates, and others.

<FIG> illustrates a configuration example of an image sensor assembly <NUM> of a light receiving apparatus <NUM> according to an embodiment of the present technology. The light receiving apparatus <NUM> may be or may include a solid-state imaging device and/or a distance measuring apparatus. The image sensor assembly <NUM> may include a pixel substrate <NUM> and a logic substrate <NUM>.

The image sensor assembly <NUM> includes a pixel array <NUM> with one or more active pixels <NUM>, wherein each active pixel <NUM> includes a photoelectric conversion element PD and an active pixel module <NUM> electrically connected to at least one of the photoelectric conversion elements PD. Each active pixel <NUM> has a detection area that receives radiation, e.g. visible light, infrared radiation or ultraviolet radiation. Each active pixel <NUM> outputs a pixel output signal pix_out indicative for the incoming radiation.

The pixel array <NUM> may include one single active pixel <NUM> or may be a one-dimensional pixel array with the photoelectric conversion elements PD of all active pixels <NUM> arranged along a straight or meandering line (line sensor) in the pixel substrate <NUM>. In particular, the pixel array <NUM> may be a two-dimensional array, wherein the photoelectric conversion elements PDs of the active pixels <NUM> may be arranged along straight or meandering rows and along straight or meandering lines in a horizontal plane of the pixel substrate <NUM>. The illustrated embodiment shows a two dimensional array of photoelectric conversion elements PD arranged along straight rows and along straight columns running orthogonal to the rows.

The photoelectric conversion elements PD may be photodiodes capable of being operated in a proportional mode or PADs capable of being operated in an avalanche mode. Each active pixel module <NUM> may be capable of operating the photoelectric conversion element PD as intensity output pixel, as DVS (dynamic vision sensor) pixel or as PAD, e.g. as SPAD pixel for event detection.

Each active pixel module <NUM> may include at least one amplifying circuit and may generate one or more pixel output signals pix_out. A pixel output signal pix_out may contain a voltage signal indicating the intensity of the radiation received by the photoelectric conversion element PD of the active pixel <NUM>. Alternatively or in addition, the pixel output signal pix_out may indicate a change of the radiation intensity detected by the active pixel <NUM>. Alternatively or in addition, the pixel output signal pix_out may indicate an event detected by the active pixel <NUM>. For example, the pixel array <NUM> may also be configured to be operated as the sensor side of a ToF (time-of-flight) sensor.

The pixel substrate <NUM> includes at least the photoelectric conversion elements PD. In addition to the photoelectric conversion elements PD, the pixel substrate <NUM> may include a pixel circuit. Each pixel circuit includes one or more circuit elements of an active pixel module <NUM> or may include the complete active pixel module <NUM>. In particular, the pixel circuit on the pixel substrate <NUM> may include at least one circuit element of each active pixel module <NUM>, e.g. an MOSFET, wherein the circuit element is electrically connected between a first supply line and the photoelectric conversion element PD.

According to another example, the pixel circuit on the pixel substrate <NUM> may include only the photoelectric conversion element PD and a logic substrate combined with the pixel substrate <NUM> may include the pixel circuit, wherein the pixel circuit includes at least one circuit element, e.g. an MOSFET, that is electrically connected between a first supply line and the photoelectric conversion element PD.

The image sensor assembly <NUM> further includes an address/driver unit <NUM> that generates and drives control signals for the active pixel modules <NUM>. Each control signal may be applied to a single active pixel module <NUM>, to a group of active pixel modules <NUM>, e.g. to all active pixel modules <NUM> in the same row or in the same column, or to all active pixel modules <NUM> of the image sensor assembly <NUM>.

A readout circuit <NUM> integrated in the image sensor assembly <NUM> may receive the pixel output signals pix_out output by the pixel array <NUM>. The image sensor assembly <NUM> may further include a controller <NUM> for controlling the address/driver unit <NUM> and/or the readout circuit <NUM> according to a process-controlled and/or time-controlled sequential control. The controller <NUM> may pre-process the pixel output signals pix_out and may pass image information img_data based on the pixel output signals pix_out to an external image data processing unit <NUM>.

In addition, the image sensor assembly <NUM> includes a protection circuit as described in more detail below.

<FIG> schematically shows functional blocks of a pixel substrate <NUM> in combination with a vertical cross-section of a detector portion <NUM> of the pixel substrate <NUM>. The pixel substrate <NUM> may be or may include a semiconductor portion, e.g. a thin slice or layer of monocrystalline silicon.

The pixel substrate <NUM> includes a photoelectric conversion element PD with a doped region <NUM> and a substrate region <NUM>. The doped region <NUM> and the substrate region <NUM> form a pn junction <NUM>.

The substrate region <NUM> may be p-conductive. The doped region <NUM> may be n-conductive. Radiation <NUM> entering through a detection area <NUM> of the pixel substrate <NUM> induces charge-carrier separation in a depletion region on both sides of the pn junction <NUM>, wherein holes move toward the p-conductive substrate region (anode region) and electrons move toward the n-conductive doped region <NUM> (cathode region).

The pixel substrate <NUM> further includes a pixel circuit <NUM> electrically connected to a first supply line <NUM> and to the photoelectric conversion element PD.

The first supply line <NUM> electrically connects the pixel circuit <NUM> with one or more first supply terminals <NUM>. Through the one or more first supply terminals <NUM> a first supply voltage is passed to the pixel substrate <NUM>. The first supply voltage may be a positive supply voltage VDD.

The pixel circuit <NUM> may include at least one circuit element of an active pixel module that converts the charge accumulated in the doped region <NUM> and/or a photocurrent induced by the photoelectric conversion element PD into a pixel output signal pix_out.

For example, the active pixel module may include an intensity read-out circuit converting at predetermined points in time charge accumulated in the doped region <NUM> into a pixel output signal pix_out with a voltage level proportional to the amount of charge stored in the doped region <NUM> at the predetermined points in time.

Alternatively or in addition, the active pixel module may include an intensity change detection circuit that outputs a pixel output signal pix_out indicating a change of a photocurrent through the photoelectric conversion element PD by at least a threshold value.

Alternatively or in addition, the active pixel module may include an event detection circuit that outputs a pixel output signal pix_out indicating whether or not the photoelectric conversion element PD detects radiation. For example, the active pixel module may apply a bias voltage across the photoelectric conversion device PD and indicates an avalanche breakdown in the photoelectric conversion device PD.

The pixel circuit <NUM> may include at least one amplifying element electrically connected between the first supply line <NUM> and the photoelectric conversion element PD. For example, the pixel circuit <NUM> may include an MOSFET with a source/drain path electrically connected between the first supply line <NUM> and the photoelectric conversion element PD.

The pixel substrate <NUM> may further include a protection circuit <NUM> that short-circuits the first supply line <NUM> and the substrate region <NUM> when a voltage between the first supply line <NUM> and the substrate region <NUM> falls below a negative threshold voltage.

When a positive supply voltage VDD is externally applied between the first supply terminal <NUM> and the substrate region <NUM>, the pixel substrate <NUM> is powered on and the pixel circuit <NUM> is operative. When radiation <NUM> enters the pixel substrate <NUM> through the detection area <NUM>, the pixel circuit <NUM> processes the charge stored in the doped region <NUM> and/or a photocurrent driven by the photoelectric conversion device PD.

When no supply voltage is externally applied between the first supply terminal <NUM> and the substrate region <NUM>, the pixel substrate <NUM> is powered off. The pixel circuit <NUM> is not operative. Instead, the pixel circuit <NUM> may pass charge carriers (electrons) generated by the radiation <NUM> entering in the detection area <NUM> through an off-state charge carrier path <NUM> to the first supply line <NUM> and to the first supply terminal <NUM>. The off-state charge carrier path <NUM> may include leakage paths, e.g. through the source/drain path of an MOSFET of the pixel circuit <NUM>.

As a result, a quiescent voltage of several 100mV may drop between the substrate region and the first supply terminal <NUM> in the power-off state of the pixel substrate <NUM>. The quiescent voltage may damage other circuit elements inside and/or outside the pixel substrate <NUM>.

The protection circuit <NUM>, which short-circuits the first supply line <NUM> and the substrate region <NUM> when a voltage between the first supply line <NUM> and the substrate region <NUM> falls below a negative threshold voltage, limits the quiescent voltage, e.g. to a voltage smaller than 100mV. The protection circuit <NUM> reduces the risk for damaging electronic circuits electrically connected to the first supply terminal <NUM>.

The pixel substrate <NUM> may include a plurality of doped regions <NUM> and pixel circuits <NUM>, wherein for each pixel circuit <NUM>, the pixel substrate <NUM> may include a signal output terminal <NUM> electrically connected to the pixel circuit <NUM>. The signal output terminal <NUM> passes a pixel signal Vpix to the logic substrate. The pixel signal Vpix may be identical with the pixel output signal pix_out, for example if the pixel circuit <NUM> includes a complete active pixel module.

The pixel substrate <NUM> may include one or more voltage reference terminals <NUM> electrically connected to the substrate region <NUM> through one or more low-resistive ohmic connections. For example, the pixel substrate <NUM> may include a heavily doped substrate contact region <NUM>. The substrate region <NUM> and the substrate contact region <NUM> are in direct contact with each other and form a unipolar junction. The dopant concentration in the substrate contact region <NUM> is sufficiently high such that the substrate contact region <NUM> and the voltage reference terminal <NUM> or the substrate contact region <NUM> and a metal line in contact with the voltage reference terminal <NUM> form an ohmic contact.

When a positive supply voltage VDD is externally applied between the first supply terminal <NUM> and the voltage reference terminal <NUM> and/or between the first supply terminal <NUM> and a second supply terminal <NUM>, the pixel substrate <NUM> is powered on and the pixel circuit <NUM> is operative.

When no supply voltage is externally applied between the first supply terminal <NUM> and the voltage reference terminal <NUM> and/or between the first supply terminal <NUM> and a second supply terminal <NUM>, the pixel substrate <NUM> is powered off and the pixel circuit <NUM> is not operative.

The protection circuit <NUM> short-circuits the first supply terminal <NUM> and the voltage reference terminal <NUM> when a voltage between the first supply terminal <NUM> and the voltage reference terminal <NUM> falls below a negative threshold voltage. The protection circuit <NUM> limits a quiescent voltage between the first supply terminal <NUM> and the voltage reference terminal <NUM> to a voltage smaller than 100mV. The protection circuit <NUM> reduces the risk for damaging electronic circuits electrically connected to the first supply terminal <NUM> and the voltage reference terminal <NUM>.

The pixel circuit <NUM> may also be electrically connected to a second supply line <NUM>, wherein the second supply line <NUM> and the substrate region <NUM> may be electrically disconnected. The second supply line <NUM> may electrically connect the pixel circuits <NUM> with one or more second supply terminals <NUM>.

The terminals <NUM>, <NUM>, <NUM>, <NUM> may include metallic structures, e.g. contact pads formed on at least one surface of the pixel substrate <NUM> and/or through via contacts extending from one side of the pixel substrate <NUM> to the opposite side.

<FIG> shows a circuit diagram for the electronic parts of the pixel substrate <NUM> in <FIG>. The photoelectric conversion element PD is represented by a photodiode. The photodiode cathode is electrically connected with the pixel circuit <NUM>. The photodiode anode is electrically connected with the substrate region <NUM>. When powered on, a positive supply voltage VDD may be externally applied to the first supply terminals <NUM>. An analog ground potential AGND may be passed through the voltage reference terminals <NUM>. A negative supply voltage VSS may be externally applied through optional second supply terminals <NUM>.

<FIG>, <FIG> refer to embodiments of protection circuits <NUM> completely or partly formed in a pixel substrate.

The protection circuit <NUM> includes a photoelectric current source <NUM> and a main transistor circuit <NUM> with a switchable current path <NUM> between the first supply line <NUM> and the substrate region <NUM>. A positive supply voltage VDD supplied to the first supply line <NUM> and analog ground potential AGND applied to the substrate region <NUM> power on the pixel substrate. The photoelectric current source <NUM> is capable of switching on the switchable current path <NUM> when the pixel substrate is powered off and a voltage difference between the first supply line <NUM> and the substrate region <NUM> falls below a negative threshold voltage.

The main transistor circuit <NUM> may include one single n-channel MOSFET or one single p-channel MOSFET, e.g., MOSFETs of the enhancement type. Alternatively, the main transistor circuit <NUM> may include more than one MOSFET, e.g. two or more MOSFETs electrically connected with the source/drain paths in parallel or MOSFETs in a cascode configuration.

The main transistor circuit <NUM> may be capable of draining the total quiescent current of all photoelectric conversion elements PD formed in the pixel substrate <NUM> when illuminated with <NUM> lux without being damaged. For example, the main transistor circuit <NUM> may permanently drain at least 1mA, for example at least 5mA or at least 10mA.

The photoelectric current source <NUM> may include a photodiode element <NUM>. The amount of energy harvested by the photodiode element <NUM> may be sufficient to turn on the main transistor circuit <NUM> such that the protection circuit <NUM> may be fully self-powered.

The photodiode element <NUM> may have the same configuration as the photoelectric conversion element PD of the active pixel or may have a different configuration. For example, a vertical dopant profile through a cathode region of the photoelectric conversion element PD of the active pixel may be the same as or may be similar to a vertical dopant profile through a cathode region of the photodiode element <NUM>. The photodiode element <NUM> may be a one part element with one continuous cathode region or may include several laterally separated parts with laterally separated cathode sections.

A total horizontal area of the photodiode element <NUM> may be smaller than a total horizontal area of one single photoelectric conversion element PD in the same pixel substrate <NUM>.

For example, a total horizontal area of the photodiode element <NUM> may be at most <NUM>%, at most <NUM>%, at most <NUM>, at most <NUM>% or at most <NUM>% of the horizontal area of the photoelectric conversion element PD. The photodiode element <NUM> may be capable of supplying a current of <NUM> to <NUM> nA at an illumination with <NUM> klux.

The protection circuit <NUM> may further include an auxiliary transistor circuit <NUM> configured to switch off the switchable current path <NUM> when a voltage difference between the first supply line <NUM> and the substrate region <NUM> is above the negative threshold voltage, e.g. positive, irrespective of any amount of charge accumulated in the cathode region of the photodiode element <NUM>. In particular, the auxiliary transistor circuit <NUM> turns off the switchable current path <NUM> when the positive supply voltage VDD is supplied to the first supply line <NUM> and the substrate region <NUM> is connected to the analog ground potential AGND.

The auxiliary transistor circuit <NUM> may include one single n-channel MOSFET or one single p-channel MOSFET, e.g., MOSFETs of the enhancement type. Alternatively, the auxiliary transistor circuit <NUM> may include more than one MOSFET, e.g. two or more MOSFETs electrically connected with the source/drain paths in parallel or MOSFETs in a cascode configuration.

The auxiliary transistor circuit <NUM> is electrically connected between a first power rail A and a control input of the main transistor circuit <NUM>. The photoelectric current source <NUM> is electrically connected between a second power rail B and the control input of the main transistor circuit <NUM>. To a first one of the first and second power rails A, B the positive supply voltage VDD is supplied. A second one of the first and second power rails A, B may be connected to analog ground potential AGND or a negative supply voltage.

The pixel substrate <NUM> may include one single protection circuit <NUM> or a plurality of protection circuits <NUM> with the switchable current paths <NUM> electrically connected in parallel to each other.

The main transistor circuit <NUM> may include one single first field effect transistor <NUM>. The auxiliary transistor circuit <NUM> may include a second field effect transistor <NUM>. The first field effect transistor <NUM> and the second field effect transistor <NUM> may have the same channel type.

Each of <FIG> shows a protection circuit <NUM> with the first field effect transistor <NUM> and the second field effect transistor <NUM> formed as p-channel MOSFETs. The photoelectric current source <NUM> is electrically connected between the gate of the first field effect transistor <NUM> and the substrate region <NUM>. A source/drain path of the second field effect transistor <NUM> is electrically connected between the first supply line <NUM> and the gate of the first field effect transistor <NUM>. A gate of the second field effect transistor <NUM> is electrically connected to the substrate region <NUM>.

The photoelectric current source includes a photodiode element <NUM>. The photodiode anode is electrically connected to the substrate region <NUM>. The photodiode cathode is electrically connected with the gate of the first field effect transistor <NUM>.

When the pixel substrate <NUM> is powered on, the positive supply voltage VDD is externally supplied to the first supply line <NUM> through a first supply terminal. In this case, the analog ground potential AGND at the gate turns on the second p-channel MOSFET <NUM> such that the second p-channel MOSFET <NUM> supplies a positive voltage to the gate of the first p-channel MOSFET <NUM>. The positive gate voltage safely turns off the first p-channel MOSFET <NUM>.

When the pixel substrate <NUM> is powered off, no positive supply voltage is applied externally to the first supply line <NUM>. In this case, the analog ground potential AGND at the gate does not turn on the second p-channel MOSFET <NUM>. When radiation impinges on the photodiode element <NUM>, electrons accumulate at the cathode side and negatively bias the gate of the p-channel MOSFET <NUM>. When the gate bias falls below the negative threshold voltage of the p-channel MOSFET <NUM>, the p-channel MOSFET <NUM> turns on and switches the first supply line <NUM> to the analog ground potential AGND. In this way, the protection circuit <NUM> limits the quiescent voltage between the first supply line <NUM> and the substrate region <NUM>.

In <FIG>, the protection circuit <NUM> is formed completely on the pixel substrate <NUM>. In other words, the pixel substrate <NUM> includes the complete protection circuit <NUM>.

In <FIG> only the photodiode element <NUM> is formed on the pixel substrate <NUM>. The first and second p-channel MOSFETS <NUM>, <NUM> are formed on a logic substrate <NUM>. One or more through contact vias <NUM> may pass the charge accumulated on the cathode of the photodiode element <NUM> to the logic substrate <NUM>.

The logic substrate <NUM> may include a first supply rail <NUM>, to which the positive supply voltage VDD is applicable, and a reference voltage rail <NUM>, to which the analog ground potential AGND is applicable. The logic substrate <NUM> may pass the positive supply voltage VDD on the first supply rail <NUM> to the first supply line of the pixel substrate <NUM> through a further through contact via. Another through contact via may pass the analog ground potential AGND between the pixel substrate <NUM> and the reference voltage rail <NUM> of the logic substrate <NUM>.

In the alternative to the example shown in <FIG>, the protection circuit <NUM> may include n channel MOSFETs in appropriate electrical connection, instead of the p channel MOSFETs in <FIG>. In such case, the photodiode element <NUM> may be or may include a hole accumulation diode with the cathode connected to the first supply line <NUM>.

The pixel substrate <NUM> may include a plurality of photoelectric conversion elements PD and pixel circuits <NUM>, wherein each pixel circuit <NUM> may be electrically connected with one, two or more of the photoelectric conversion elements PD. The pixel substrate <NUM> may include one single protection circuit <NUM> or more than one protection circuit <NUM>.

<FIG> refer to active pixel modules providing a photoelectric conversion element PD and a pixel circuit <NUM> configured for an analog intensity read-out of the photoelectric conversion element PD.

The pixel circuit <NUM> includes an amplification transistor <NUM> and a transfer transistor <NUM>, wherein a source/drain path of the amplification transistor <NUM> is electrically connected between the first supply line <NUM> and a vertical signal line VSL. A source/drain path of the transfer transistor <NUM> is electrically connected between the photoelectric conversion element PD and a gate of the amplification transistor <NUM>.

The photoelectric conversion element PD photoelectrically converts incident radiation into electric charges (here, electrons). The amount of electric charge generated in the photoelectric conversion element PD corresponds to the amount of the incident radiation.

The transfer transistor <NUM> is connected between the photoelectric conversion element PD and a floating diffusion region FD. The transfer transistor <NUM> serves as a transfer element for transferring charge from the photoelectric conversion element PD to the floating diffusion region FD. The floating diffusion region FD serves as temporary local charge storage. A transfer signal TGL serving as a control signal is supplied to the gate of the transfer transistor <NUM> through a transfer control line.

Thus, the transfer transistor <NUM> may transfer electrons photoelectrically converted by the photoelectric conversion element PD to the floating diffusion FD.

A reset transistor <NUM> may be electrically connected between the floating diffusion FD and the first supply line <NUM> to which the positive supply voltage VDD is supplied. A reset signal RST serving as a control signal is supplied to the gate of the reset transistor <NUM> through a reset control line.

Thus, the reset transistor <NUM> serving as a reset element resets a potential of the floating diffusion FD to that of the first supply line <NUM>.

The floating diffusion FD is connected to the gate of the amplification transistor <NUM> serving as an amplification element. That is, the floating diffusion FD functions as the input node of the amplification transistor <NUM>.

The amplification transistor <NUM> and a selection transistor <NUM> may be electrically connected in series between the first supply line <NUM> and a vertical signal line VSL.

Thus, the amplification transistor <NUM> is connected to the signal line VSL through the selection transistor <NUM> and constitutes a source-follower circuit with a constant current source between the selection transistor <NUM> and a second supply line.

Then, a selection signal SEL serving as a control signal corresponding to an address signal is supplied to the gate of the selection transistor <NUM> through a selection control line, and the selection transistor <NUM> is turned on.

When the selection transistor <NUM> is turned on, the amplification transistor <NUM> amplifies the potential of the floating diffusion FD and outputs a voltage corresponding to the potential of the floating diffusion FD to the vertical signal line VSL. The vertical signal line VSL may transfer the analog pixel output signal pix_out from the pixel circuit <NUM> to an analog-to-digital converter circuit in the readout circuit <NUM> of <FIG>.

Since the respective gates of the transfer transistor <NUM>, the reset transistor <NUM>, and the selection transistor <NUM> are, for example, connected in units of rows, these operations are simultaneously performed for each of the pixel circuits <NUM> of one row.

The analog pixel output signal pix_out on the vertical signal line VSL is a representation of the pixel output signals pix_out in <FIG>. The pixel circuit <NUM> represents a complete active pixel module <NUM> as illustrated in <FIG>.

In <FIG> the pixel circuit <NUM> represents an active pixel module formed completely on the pixel substrate <NUM>. In other words, the pixel substrate <NUM> includes the active pixel modules <NUM> of <FIG>. One through contact via <NUM> per pixel may pass the pixel output signal pix_out to a logic substrate <NUM>.

The pixel circuit <NUM> of <FIG> may be combined with any of the protection circuits <NUM> as illustrated in <FIG>, <FIG> in the same light receiving apparatus, e.g., on the same pixel substrate <NUM>.

In <FIG> only the photoelectric conversion element PD is formed on the pixel substrate <NUM>. The pixel circuit <NUM> with the transfer transistor <NUM>, the amplifier transistor <NUM>, the reset transistor <NUM> and the selection transistor <NUM> may be completely formed on the logic substrate <NUM>. One through contact via <NUM> may pass the charge accumulated on the cathode of the photoelectric conversion element PD to the logic substrate <NUM>.

The logic substrate <NUM> may include a first supply rail <NUM>, to which the positive supply voltage VDD is applied. One or more further through contact vias may pass the analog ground potential AGND between the substrate region <NUM> and a reference voltage rail of the logic substrate <NUM>.

<FIG> shows a pixel substrate <NUM> and a logic substrate <NUM> of a light receiving apparatus. The light receiving apparatus may be a solid-state imaging device or distance measuring apparatus, by way of example. The pixel substrate <NUM> includes a protection circuit <NUM> as described above and a pixel circuit <NUM> for intensity read-out with five transistors. In particular, the pixel circuit <NUM> includes a floating diffusion gate transistor <NUM> electrically connected between the reset transistor <NUM> and the floating diffusion FD.

The logic substrate <NUM> includes a voltage supply circuit <NUM> that generates a positive supply voltage VDD between a first supply rail <NUM> and a reference voltage rail <NUM>. One or more first supply terminals <NUM> pass the positive supply voltage VDD from the logic substrate <NUM> to the pixel substrate <NUM>. One or more reference voltage terminals <NUM> pass the analog ground potential AGND between the reference voltage rail <NUM> on the logic substrate <NUM> and the substrate region <NUM> of the pixel substrate <NUM>.

The off-state charge carrier path <NUM> includes the source/drain paths of the reset transistor <NUM> and the floating diffusion gate transistor <NUM>.

<FIG> refer to active pixel modules configured for detecting intensity changes of the radiation impinging onto a photoelectric conversion element PD.

The pixel circuit <NUM> includes an amplifier portion <NUM> and a feedback portion <NUM>, wherein a controllable current path of the feedback portion <NUM> is electrically connected between the first supply line <NUM> and the photoelectric conversion element PD. A controllable current path of the amplifier portion <NUM> is electrically connected between a control input of the feedback portion <NUM> and the substrate region <NUM>. A load element <NUM> is electrically connected between the first supply line <NUM> and the controllable current path of the amplifier portion <NUM>.

The amplifier portion <NUM> may include or consist of an inverting amplifier element, e.g. an n-channel MOSFET. Alternatively, the amplifier portion <NUM> may include an amplifier circuit with more than one transistor. In particular, the amplifier portion <NUM> may be configured as common source amplifier circuit.

An output of the amplifier portion <NUM> supplies a photoreceptor signal Vpr and feeds back to the input of the amplifier portion <NUM> through the feedback portion <NUM>. The feedback portion <NUM> may include or consist of an amplifier element, e.g. an n-channel MOSFET in source-follower configuration. Alternatively, the feedback portion <NUM> may include a p-channel MOSFET with fixed gate bias or a feedback circuit with more than one element.

The feedback portion <NUM> includes a controlled path, wherein a current through the controlled path is controlled in response to the feedback signal. The amplifier portion <NUM> and the feedback portion <NUM> define a predetermined current-to-voltage transfer characteristic. According to an example, the predetermined current-to-voltage transfer characteristic may be a logarithmic current-to-voltage transfer characteristic.

An input of the pixel circuit <NUM> is electrically connected to the photoelectric conversion element PD. For example, the controlled path of the feedback portion <NUM> and the photoelectric conversion element PD may be electrically connected in series between the first supply line <NUM> and the analog ground potential AGND.

In particular, the feedback portion <NUM> may include an n-channel feedback MOSFET. A source of the feedback MOSFET is connected to a cathode of the photoelectric conversion element PD. An anode of the photoelectric conversion element PD is electrically connected to analog ground potential AGND and may be formed by a substrate region <NUM>. The amplifier portion <NUM> may include a common source amplifier including a n-channel amplifier MOSET and a load element <NUM>. The source of the amplifier MOSFET is electrically connected to analog ground potential AGND. The load element <NUM> is electrically connected between the first supply potential VDD and the drain of the amplifier MOSFET. The load element <NUM> may include the controlled path of a p-channel load MOSFET with the gate electrically connected to a bias potential Vbias. The bias potential Vbias may be fixed.

A pixel back-end <NUM> of the pixel circuit <NUM> detects when a change of the photoreceptor signal Vpr with respect to a previously indicated state exceeds an upper threshold and/or falls below a lower threshold. The pixel back-end <NUM> outputs a digital pixel output signal pix_out indicating whether or not a voltage level of the photoreceptor signal Vpr has changed to a degree that the difference between the current voltage level of the photoreceptor signal Vpr and the previously indicated voltage level of the photoreceptor signal Vpr falls below a predefined lower threshold or exceeds an upper threshold.

In <FIG> the pixel substrate <NUM> includes the photoelectric conversion element PD and the n-channel MOSFETs of the active pixel module. A pixel circuit <NUM> on the pixel substrate <NUM> includes the n-channel feedback MOSFET and the n-channel amplifier MOSFET. The logic substrate <NUM> includes the p-channel load MOSFET and the pixel back-end <NUM>. One through contact via <NUM> per pixel passes the photoreceptor signal Vpr from the pixel substrate <NUM> to the logic substrate <NUM>.

For example, the pixel substrate <NUM> may include a p-type substrate and formation of p-channel MOSFETs may imply the formation of n-doped wells separating the p-type source and drain regions of the p-channel MOSFETs from each other and from further p-type regions. Avoiding the formation of p-channel MOSFETs may therefore simplify the manufacturing process of the pixel substrate <NUM>.

In <FIG> the pixel substrate <NUM> includes the photoelectric conversion element PD. The logic substrate <NUM> includes the n-channel MOSFETs, the p-channel load MOSFET and the pixel back-end <NUM>. For each pixel, one single through contact via <NUM> passes the photocurrent Iphoto from the pixel substrate <NUM> to the logic substrate <NUM>.

<FIG> refers to an active pixel module configured to detect single events, in particular for measuring a time period between a starting event and reception of radiation in the photoelectric conversion element PD.

The photoelectric conversion element PD may be an element generating a signal in response to reception of photons, for example, an SPAD (Single Photon Avalanche Diode) element. Specifically, a light receiving apparatus according to the present embodiment is configured such that the photoelectric conversion element PD of each pixel includes an SPAD element. Note that the light receiving element is not limited to the SPAD element and may be any of various elements such as an APD (Avalanche Photo Diode) and a CAPD (Current Assisted Photonic Demodulator).

The pixel circuit <NUM> may include a complete active pixel module for event detection with the source/drain path of a p-channel quenching MOSFET <NUM> and the photoelectric conversion element PD electrically connected in this order in series between the first supply line <NUM> and the substrate region <NUM> that forms the anode of the photoelectric conversion element PD.

The node <NUM> between the quenching MOSFET <NUM> and the cathode of the photoelectric conversion element PD is electrically connected to the input of an inverting amplifier stage <NUM>. The inverting amplifier stage <NUM> may be a CMOS inverter with the source/drain path of a p-channel inverter stage MOSFET <NUM> and the source/drain path of an n-channel inverter stage MOSFET <NUM> electrically connected in this order in series between the first supply line <NUM> and a second supply line <NUM>. The inverting amplifier stage <NUM> outputs a digital pixel output signal pix_out. The raising edge of the pixel output signal pix_out indicates the start of receiving radiation.

A capacitive element C may be connected between the input of the inverting amplifier stage <NUM> and the second supply line <NUM>.

A positive first supply voltage VDD applied to the first supply line <NUM>, a second supply voltage VSS (0V) applied to the second supply line <NUM> and a (negative) anode voltage applied to the substrate region <NUM> of the photoelectric conversion element PD power on the pixel circuit <NUM>.

The anode voltage is selected such that a resulting reverse bias voltage across the photoelectric conversion element PD may be nearly as high as, equal to or slightly higher than a breakdown voltage of the photoelectric conversion element PD. For example, the reverse bias voltage may exceed the breakdown voltage by an excess voltage of approximately <NUM> V to <NUM> V such that the photoelectric conversion element PD operates in a region referred to as a Geiger mode in a region with no DC stability point.

A fixed voltage biases the gate of the p-channel quenching MOSFET <NUM> which is operated as passive load for the photoelectric conversion element PD. For example, the gate of the quenching MOSFET <NUM> may be electrically connected to the second supply line <NUM> (VSS).

In the absence of radiation, no current flows through the photoelectric conversion element PD and the p-channel quenching MOSFET <NUM> acting as passive high resistive load sets the potential at the node <NUM> to the supply voltage VDD and the inverting amplifier stage <NUM> outputs a low-level pixel output signal pix_out.

A single photon received in the photoelectric conversion element PD generates an electron/hole pair that triggers avalanche multiplication in the photoelectric conversion element PD. With the rapidly increasing avalanche current through the photoelectric conversion element PD, the electric potential at the node <NUM> rapidly decreases to below the threshold of the inverting amplifier stage <NUM>. The level of the pixel output signal pix_out changes from close to 0V to close to VDD. With further increasing avalanche current the voltage drop across the quenching MOSFET <NUM> gets high enough such that the reverse bias voltage across the photoelectric conversion element PD drops to below the reverse voltage required for maintaining the avalanche breakdown. The avalanche current through the photoelectric conversion element PD ceases. The photoelectric conversion element PD returns to the initial state, the potential at node <NUM> rises to above the threshold of the inverting amplifier circuit <NUM> and the level of the pixel output signal pix_out returns to close to 0V.

A light receiving apparatus may combine a plurality of pixel circuits <NUM> as illustrated in <FIG> with any of the protection circuits <NUM> of <FIG>, <FIG>.

The protection circuit <NUM> may include at least two laterally separated parts <NUM> electrically arranged in parallel.

<FIG> are top views onto planar main surfaces of pixel substrates <NUM>. Each main surface includes a plurality of detection areas <NUM> of active pixels arranged in a matrix. A first supply terminal <NUM> and a voltage reference terminal <NUM> are formed along an edge of the main surface. A protection circuit <NUM> includes a photodiode element with a photosensitive area <NUM>. The photosensitive area <NUM> may be smaller than a detection area <NUM>.

In <FIG> the photodiode element <NUM> with the photosensitive area <NUM> is formed outside a smallest rectangular area including all detection areas <NUM>. The protection circuit <NUM> is formed in the vicinity of the first supply terminal <NUM> and the voltage reference terminal <NUM>.

In <FIG> the protection circuit <NUM> includes a plurality of laterally separated photodiode elements <NUM> with the photosensitive areas <NUM> formed between the detection areas <NUM> and within a smallest rectangular area including all detection areas <NUM>.

<FIG> is a perspective view showing an example of a laminated structure of a light receiving apparatus, e.g. a solid-state imaging device <NUM> with a plurality of active pixels arranged matrix-like in array form. Each pixel has at least one photoelectric conversion element.

The solid-state imaging device <NUM> has the laminated structure of a pixel substrate (upper chip) <NUM> and a logic substrate (lower chip) <NUM>.

The laminated pixel and logic substrates <NUM> and <NUM> may be electrically connected to each other through TC(S)Vs (Through Contact (Silicon) Vias) formed in the pixel substrate <NUM>.

The solid-state imaging device <NUM> may be formed to have the laminated structure in such a manner that the pixel substrate <NUM> and the logic substrate <NUM> are bonded together at a wafer level and cut out by dicing.

In the laminated structure of the upper and lower two chips, the pixel substrate <NUM> may be an analog chip (sensor chip) including at least one analog component of each pixel, e.g., the photoelectric conversion elements arranged in array form. For example, the pixel substrate <NUM> may include only the photoelectric conversion elements. Alternatively, the pixel substrate <NUM> may include, in addition to the photoelectric conversion element one, two, three or four of the active elements (transfer transistor TG, reset transistor RST, amplification transistor AMO, and selection transistor SEL) of each active pixel.

The pixel substrate <NUM> may further include one or more protection circuits as described above. For example, the pixel substrate <NUM> may include, from the protection circuit, only the photoelectric current source. Alternatively, the pixel substrate <NUM> may include, in addition to the photoelectric current source one, two, three or four of the further active elements of the protection circuit.

The pixel substrate <NUM> may also include logic circuits. For example, the pixel substrate <NUM> may include portions of an analog-to-digital converter (ADC), e.g. at least one of a comparator, a counter, a current source and a DAC (digital-to-analog converter), may include parts of the comparator, or may include the complete ADC for each column of pixel circuits. The pixel substrate <NUM> may also include at least portions of the address/driver unit <NUM>, the readout circuit <NUM> and the controller <NUM> and/or at least portions of the data processing circuit <NUM> as illustrated in <FIG>.

The logic substrate <NUM> may be mainly a logic chip (digital chip) that includes the elements complementing the circuits on the pixel substrate <NUM> to the solid-state imaging device <NUM>. The logic substrate <NUM> may also include analog circuits, for example circuits that quantize analog signals transferred from the pixel substrate <NUM> through the TCVs and to a signal processing circuit.

The logic substrate <NUM> may have one or more bonding pads BPD and the pixel substrate <NUM> may have openings OPN for use in wire-bonding to the logic substrate <NUM>.

The solid-state imaging device <NUM> with the laminated structure of the pixel substrate <NUM> and the logic substrate <NUM> may have the following characteristic configuration.

The electrical connection between the pixel substrate <NUM> and the logic substrate <NUM> is performed through, for example, the TCVs. The TCVs may be arranged at chip ends or between a pad region and a circuit region. The TCVs for transmitting control signals and supplying power are mainly concentrated at, for example, the four corners of the solid-state imaging device <NUM>, by which a signal wiring area of the pixel substrate <NUM> can be reduced.

<FIG> is a view depicting an example of a schematic configuration of an endoscopic surgery system to which the technology according to an embodiment of the present disclosure (present technology) can be applied.

In <FIG>, a state is illustrated in which a surgeon (medical doctor) <NUM> is using an endoscopic surgery system <NUM> to perform surgery for a patient <NUM> on a patient bed <NUM>. As depicted, the endoscopic surgery system <NUM> includes an endoscope <NUM>, other surgical tools <NUM> such as a pneumoperitoneum tube <NUM> and an energy device <NUM>, a supporting arm apparatus <NUM> which supports the endoscope <NUM> thereon, and a cart <NUM> on which various apparatus for endoscopic surgery are mounted.

The endoscope <NUM> includes a lens barrel <NUM> having a region of a predetermined length from a distal end thereof to be inserted into a body cavity of the patient <NUM>, and a camera head <NUM> connected to a proximal end of the lens barrel <NUM>. In the example depicted, the endoscope <NUM> is depicted which includes as a rigid endoscope having the lens barrel <NUM> of the hard type. However, the endoscope <NUM> may otherwise be included as a flexible endoscope having the lens barrel <NUM> of the flexible type.

The lens barrel <NUM> has, at a distal end thereof, an opening in which an objective lens is fitted. A light source apparatus <NUM> is connected to the endoscope <NUM> such that light generated by the light source apparatus <NUM> is introduced to a distal end of the lens barrel <NUM> by a light guide extending in the inside of the lens barrel <NUM> and is irradiated toward an observation target in a body cavity of the patient <NUM> through the objective lens. It is to be noted that the endoscope <NUM> may be a forward-viewing endoscope or may be an oblique-viewing endoscope or a side-viewing endoscope.

An optical system and an image pickup element (solid-state imaging device) are provided in the inside of the camera head <NUM> such that reflected light (observation light) from the observation target is condensed on the image pickup element by the optical system. The observation light is photo-electrically converted by the image pickup element to generate an electric signal corresponding to the observation light, namely, an image signal corresponding to an observation image. The image signal is transmitted as RAW data to a CCU <NUM>.

The CCU <NUM> includes a central processing unit (CPU), a graphics processing unit (GPU) or the like and integrally controls operation of the endoscope <NUM> and a display apparatus <NUM>. Further, the CCU <NUM> receives an image signal from the camera head <NUM> and performs, for the image signal, various image processes for displaying an image based on the image signal such as, for example, a development process (demosaic process).

The display apparatus <NUM> displays thereon an image based on an image signal, for which the image processes have been performed by the CCU <NUM>, under the control of the CCU <NUM>.

The light source apparatus <NUM> includes a light source such as, for example, a light emitting diode (LED) and supplies irradiation light upon imaging of a surgical region to the endoscope <NUM>.

An inputting apparatus <NUM> is an input interface for the endoscopic surgery system <NUM>. A user can perform inputting of various kinds of information or instruction inputting to the endoscopic surgery system <NUM> through the inputting apparatus <NUM>. For example, the user would input an instruction or a like to change an image pickup condition (type of irradiation light, magnification, focal distance or the like) by the endoscope <NUM>.

A treatment tool controlling apparatus <NUM> controls driving of the energy device <NUM> for cautery or incision of a tissue, sealing of a blood vessel or the like. A pneumoperitoneum apparatus <NUM> feeds gas into a body cavity of the patient <NUM> through the pneumoperitoneum tube <NUM> to inflate the body cavity in order to secure the field of view of the endoscope <NUM> and secure the working space for the surgeon. A recorder <NUM> is an apparatus capable of recording various kinds of information relating to surgery. A printer <NUM> is an apparatus capable of printing various kinds of information relating to surgery in various forms such as a text, an image or a graph.

It is to be noted that the light source apparatus <NUM> which supplies irradiation light when a surgical region is to be imaged to the endoscope <NUM> may include a white light source which includes, for example, an LED, a laser light source or a combination of them. Where a white light source includes a combination of red, green, and blue (RGB) laser light sources, since the output intensity and the output timing can be controlled with a high degree of accuracy for each color (each wavelength), adjustment of the white balance of a picked up image can be performed by the light source apparatus <NUM>. Further, in this case, if laser beams from the respective RGB laser light sources are irradiated time-divisionally on an observation target and driving of the image pickup elements of the camera head <NUM> are controlled in synchronism with the irradiation timings. Then images individually corresponding to the R, G and B colors can be also picked up time-divisionally. According to this method, a color image can be obtained even if color filters are not provided for the image pickup element.

Further, the light source apparatus <NUM> may be controlled such that the intensity of light to be outputted is changed for each predetermined time. By controlling driving of the image pickup element of the camera head <NUM> in synchronism with the timing of the change of the intensity of light to acquire images time-divisionally and synthesizing the images, an image of a high dynamic range free from underexposed blocked up shadows and overexposed highlights can be created.

Further, the light source apparatus <NUM> may be configured to supply light of a predetermined wavelength band ready for special light observation. In special light observation, for example, by utilizing the wavelength dependency of absorption of light in a body tissue to irradiate light of a narrow band in comparison with irradiation light upon ordinary observation (namely, white light), narrow band observation (narrow band imaging) of imaging a predetermined tissue such as a blood vessel of a superficial portion of the mucous membrane or the like in a high contrast is performed. Alternatively, in special light observation, fluorescent observation for obtaining an image from fluorescent light generated by irradiation of excitation light may be performed. In fluorescent observation, it is possible to perform observation of fluorescent light from a body tissue by irradiating excitation light on the body tissue (autofluorescence observation) or to obtain a fluorescent light image by locally injecting a reagent such as indocyanine green (ICG) into a body tissue and irradiating excitation light corresponding to a fluorescent light wavelength of the reagent upon the body tissue. The light source apparatus <NUM> can be configured to supply such narrow-band light and/or excitation light suitable for special light observation as described above.

The example of the endoscopic surgery system to which the technology according to an embodiment of the present disclosure is applied has been described above.

The technology according to the present disclosure may also be realized as a light receiving device mounted in a mobile body of any type such as automobile, electric vehicle, hybrid electric vehicle, motorcycle, bicycle, personal mobility, airplane, drone, ship, or robot.

The vehicle control system <NUM> includes a plurality of electronic control units connected to each other via a communication network <NUM>. In the example depicted in <FIG>, the vehicle control system <NUM> includes a driving system control unit <NUM>, a body system control unit <NUM>, an outside-vehicle information detecting unit <NUM>, an in-vehicle information detecting unit <NUM>, and an integrated control unit <NUM>. In addition, a microcomputer <NUM>, a sound/image output section <NUM>, and a vehicle-mounted network interface (I/F) <NUM> are illustrated as a functional configuration of the integrated control unit <NUM>.

The outside-vehicle information detecting unit <NUM> detects information about the outside of the vehicle including the vehicle control system <NUM>. For example, the outside-vehicle information detecting unit <NUM> is connected with an imaging section <NUM>. The outside-vehicle information detecting unit <NUM> makes the imaging section <NUM> imaging 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 unit <NUM> may 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 section <NUM> may include a light receiving apparatus according to the embodiments of the present disclosure. The imaging section <NUM> receives light, and outputs an electric signal corresponding to a received light amount of the light. The imaging section <NUM> can 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 section <NUM> may be visible light, or may be invisible light such as infrared rays or the like.

In addition, the microcomputer <NUM> can output a control command to the body system control unit <NUM> on the basis of the information about the outside of the vehicle which information is obtained by the outside-vehicle information detecting unit <NUM>. For example, the microcomputer <NUM> can 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 unit <NUM>.

The sound/image output section <NUM> transmits an output signal of at least one of a sound or an image to an output device capable of visually or audible notifying information to an occupant of the vehicle or the outside of the vehicle. In the example of <FIG>, an audio speaker <NUM>, a display section <NUM>, and an instrument panel <NUM> are illustrated as the output device. The display section <NUM> may, for example, include at least one of an on-board display or a head-up display.

The imaging sections <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are, for example, disposed at positions on a front nose, side-view mirrors, a rear bumper, and a back door of the vehicle <NUM> as well as a position on an upper portion of a windshield within the interior of the vehicle. The imaging section <NUM> provided to the front nose and the imaging section <NUM> provided to the upper portion of the windshield within the interior of the vehicle obtain mainly an image of the front of the vehicle <NUM>. The imaging sections <NUM> and <NUM> provided to the side view mirrors obtain mainly an image of the sides of the vehicle <NUM>. The imaging section <NUM> provided to the rear bumper or the back door obtains mainly an image of the rear of the vehicle <NUM>. The imaging section <NUM> provided to the upper portion of the windshield within the interior of the vehicle is used mainly to detect a preceding vehicle, a pedestrian, an obstacle, a signal, a traffic sign, a lane, or the like.

Incidentally, <FIG> depicts an example of photographing ranges of the imaging sections <NUM> to <NUM>. An imaging range <NUM> represents the imaging range of the imaging section <NUM> provided to the front nose. Imaging ranges <NUM> and <NUM> respectively represent the imaging ranges of the imaging sections <NUM> and <NUM> provided to the side view mirrors. An imaging range <NUM> represents the imaging range of the imaging section <NUM> provided to the rear bumper or the back door. A bird's-eye image of the vehicle <NUM> as viewed from above is obtained by superimposing image data imaged by the imaging sections <NUM> to <NUM>, for example.

At least one of the imaging sections <NUM> to <NUM> may have a function of obtaining distance information. For example, at least one of the imaging sections <NUM> to <NUM> may be a stereo camera constituted of a plurality of imaging elements, or may be an imaging element having pixels for phase difference detection or event detection as described with reference to <FIG>.

For example, the microcomputer <NUM> can determine a distance to each three-dimensional object within the imaging ranges <NUM> to <NUM> and a temporal change in the distance (relative speed with respect to the vehicle <NUM>) on the basis of the distance information obtained from the imaging sections <NUM> to <NUM>, and thereby extract, as a preceding vehicle, a nearest three-dimensional object in particular that is present on a traveling path of the vehicle <NUM> and which travels in substantially the same direction as the vehicle <NUM> at a predetermined speed (for example, equal to or more than <NUM>/hour). Further, the microcomputer <NUM> can 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.

The example of the vehicle control system to which the technology according to an embodiment of the present disclosure is applicable has been described above.

Claim 1:
A pixel substrate (<NUM>), comprising:
a photoelectric conversion element (PD) comprising a doped region (<NUM>) and a substrate region (<NUM>), wherein the doped region (<NUM>) and the substrate region (<NUM>) form a pn junction (<NUM>);
a pixel circuit (<NUM>) electrically connected to a first supply line (<NUM>) and the photoelectric conversion element (PD), and
a protection circuit (<NUM>) configured to short-circuit the first supply line (<NUM>) and the substrate region (<NUM>) when a voltage difference between the first supply line (<NUM>) and the substrate region (<NUM>) falls below a negative threshold voltage,
wherein the protection circuit (<NUM>) comprises a photoelectric current source (<NUM>) and a main transistor circuit (<NUM>) with a switchable current path (<NUM>) between the first supply line (<NUM>) and the substrate region (<NUM>), and wherein the photoelectric current source (<NUM>) is configured to switch on the switchable current path (<NUM>) when a voltage difference between the first supply line (<NUM>) and the substrate region (<NUM>) falls below the negative threshold voltage.