JP7532451B2 - Photoelectric conversion device - Google Patents

Description

The present invention relates to a photoelectric conversion device.

Patent document 1 discloses a photoelectric conversion device in which pixels each including a plurality of avalanche photodiodes (hereinafter, APDs) are arranged.

JP 2020-123847 A

In such photoelectric conversion devices, optical black pixels (hereinafter referred to as OB pixels) may be provided to detect signals that are not dependent on external light. Specifically, OB pixels are pixels that have a light-shielding portion provided on the top of the APD and detect signals that are not dependent on external light.

When light is incident on an effective pixel and photoelectric conversion is performed, avalanche emission occurs due to the transfer of charge to an adjacent pixel and the recombination of electrons and holes. In this case, if the area in which the effective pixels are arranged is adjacent to the area in which the OB pixels are arranged, the avalanche emission from the effective pixel may induce avalanche multiplication in the OB pixel, resulting in a decrease in image quality.

A photoelectric conversion device having a pixel region including a plurality of pixels, each having an avalanche photodiode including an anode and a cathode, the plurality of pixels including effective pixels that output a photon detection signal in response to detection of a photon, dummy pixels that do not output the photon detection signal, and optical black pixels having a light-shielding portion, the effective pixels are connected to a counter circuit that counts the photon detection signal, and the dummy pixels are not connected to the counter circuit, the pixel region has a first region having the effective pixels, a second region having the dummy pixels, and a third region having the optical black pixels, the second region has a first portion and a second portion that are in contact with an end of the pixel region, the first portion, the first region, the second portion, and the third region are arranged in this order in a first direction, and in the first direction, a width of the second portion is wider than a width of the first portion.

The present invention provides a photoelectric conversion device that reduces degradation of image quality.

1 is a schematic diagram of a photoelectric conversion device according to an embodiment. 2 is a schematic diagram of a PD substrate of a photoelectric conversion device according to an embodiment. FIG. 2 is a schematic diagram of a circuit board of a photoelectric conversion device according to an embodiment. FIG. 1 is a schematic diagram of a photoelectric conversion device according to a first embodiment. 1 is a cross-sectional view of a photoelectric conversion device according to a first embodiment. 2 is a configuration example of a pixel circuit of a photoelectric conversion device according to a first embodiment. 3 is a schematic diagram showing driving of a pixel circuit of the photoelectric conversion device according to the first embodiment. FIG. 2 is a configuration example of a pixel circuit of a photoelectric conversion device according to a first embodiment. 3 is a schematic diagram showing driving of a pixel circuit of the photoelectric conversion device according to the first embodiment. FIG. 13 is a configuration example of a pixel circuit of a photoelectric conversion device according to a second embodiment. FIG. 11 is a schematic diagram showing driving of a pixel circuit of a photoelectric conversion device according to a second embodiment. FIG. 13 is a schematic diagram of a photoelectric conversion device according to a third embodiment. 13 is a configuration example of a pixel circuit of a photoelectric conversion device according to a third embodiment. 13 is a configuration example of a pixel circuit of a photoelectric conversion device according to a fourth embodiment. FIG. 13 is a functional block diagram of a photoelectric conversion system according to a fifth embodiment. FIG. 13 is a functional block diagram of a photoelectric conversion system according to a sixth embodiment. FIG. 13 is a functional block diagram of a photoelectric conversion system according to a seventh embodiment. FIG. 13 is a functional block diagram of a photoelectric conversion system according to an eighth embodiment. FIG. 13 is a functional block diagram of a photoelectric conversion system according to a ninth embodiment.

The embodiments shown below are intended to embody the technical ideas of the present invention, but are not intended to limit the present invention. The sizes and positional relationships of the components shown in each drawing may be exaggerated to clarify the explanation. In the following explanation, the same configurations may be assigned the same numbers and explanations may be omitted.

Below, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, terms indicating specific directions or positions (for example, "up," "down," "right," "left," and other terms that include these terms) will be used as necessary. The use of these terms is intended to facilitate understanding of the embodiment with reference to the drawings, and the technical scope of the present invention is not limited by the meaning of these terms.

In this specification, a planar view refers to a view from a direction perpendicular to the light incidence surface of the semiconductor layer. A cross-sectional view refers to a surface in a direction perpendicular to the light incidence surface of the semiconductor layer. If the light incidence surface of the semiconductor layer is rough when viewed microscopically, the planar view is defined based on the light incidence surface of the semiconductor layer when viewed macroscopically.

In the following description, the anode of the avalanche photodiode (APD) is set to a fixed potential, and the signal is taken from the cathode side. Therefore, the first conductive type semiconductor region in which charges of the same polarity as the signal charge are the majority carriers is an N-type semiconductor region, and the second conductive type semiconductor region in which charges of a different polarity than the signal charge are the majority carriers is a P-type semiconductor region. Note that the present invention also applies when the cathode of the APD is set to a fixed potential, and the signal is taken from the anode side. In this case, the first conductive type semiconductor region in which charges of the same polarity as the signal charge are the majority carriers is a P-type semiconductor region, and the second conductive type semiconductor region in which charges of a different polarity than the signal charge are the majority carriers is an N-type semiconductor region. In the following, a case in which one node of the APD is set to a fixed potential is described, but the potentials of both nodes may fluctuate.

In this specification, when the term "impurity concentration" is used simply, it means the net impurity concentration minus the amount compensated for by impurities of the opposite conductivity type. In other words, "impurity concentration" refers to the NET doping concentration. A region where the P-type added impurity concentration is higher than the N-type added impurity concentration is a P-type semiconductor region. Conversely, a region where the N-type added impurity concentration is higher than the P-type added impurity concentration is an N-type semiconductor region.

First Embodiment
A photoelectric conversion device and a driving method thereof according to the present invention will be described with reference to FIGS.

Figure 1 is a diagram showing the configuration of a stacked photoelectric conversion device 100. The photoelectric conversion device 100 is configured by stacking and electrically connecting two substrates, a sensor substrate 11 and a circuit substrate 21. The sensor substrate 11 has a first semiconductor layer having a photoelectric conversion element 102 described later, and a first wiring structure. The circuit substrate 21 has a second semiconductor layer having circuits such as a signal processing portion 103 described later, and a second wiring structure. The photoelectric conversion device 100 is configured by stacking the second semiconductor layer, the second wiring structure, the first wiring structure, and the first semiconductor layer in this order. The photoelectric conversion device described in each embodiment is a back-illuminated photoelectric conversion device in which light is incident from the second surface and a circuit substrate is disposed on the first surface.

In the following, the sensor substrate 11 and the circuit substrate 21 are described as diced chips, but are not limited to chips. For example, each substrate may be a wafer. Also, each substrate may be stacked in the wafer state and then diced, or each chip may be stacked and bonded after being chipped from the wafer state.

A pixel region 12 is arranged on the sensor substrate 11, and a circuit region 22 that processes signals detected in the pixel region 12 is arranged on the circuit substrate 21.

Figure 2 is a diagram showing an example of the arrangement of the sensor substrate 11. Pixels 101 each having a photoelectric conversion element 102 including an APD are arranged in a two-dimensional array in a plan view to form a pixel region 12.

Pixel 101 is typically a pixel for forming an image, but when used for TOF (Time of Flight), it does not necessarily have to form an image. In other words, pixel 101 may be a pixel for measuring the time when light arrives and the amount of light.

Figure 3 is a diagram showing the configuration of the circuit board 21. It has a signal processing unit 103 that processes the electric charges photoelectrically converted by the photoelectric conversion element 102 in Figure 2, a readout circuit 112, a control pulse generation unit 115, a horizontal scanning circuit unit 111, a signal line 113, and a vertical scanning circuit unit 110.

The photoelectric conversion element 102 in FIG. 2 and the signal processing unit 103 in FIG. 3 are electrically connected via connection wiring provided for each pixel.

The vertical scanning circuit unit 110 receives a control pulse supplied from the control pulse generating unit 115 and supplies a control pulse to each pixel. The vertical scanning circuit unit 110 uses logic circuits such as a shift register and an address decoder.

The signal output from the photoelectric conversion element 102 of the pixel is processed by the signal processing unit 103. The signal processing unit 103 is provided with a counter, memory, etc., and digital values are stored in the memory.

The horizontal scanning circuit unit 111 inputs a control pulse to the signal processing unit 103 to sequentially select each column in order to read out the signal from the memory of each pixel in which the digital signal is stored.

A signal is output from the signal processing unit 103 of the pixel selected by the vertical scanning circuit unit 110 to the signal line 113 for the selected column.

The signal output to the signal line 113 is output to a recording unit or signal processing unit external to the photoelectric conversion device 100 via the output circuit 114.

In FIG. 2, the photoelectric conversion elements in the pixel region may be arranged one-dimensionally. The function of the signal processing unit does not necessarily need to be provided for each photoelectric conversion element. For example, one signal processing unit may be shared by multiple photoelectric conversion elements, and signal processing may be performed sequentially.

2 and 3, a plurality of signal processing units 103 are arranged in a region overlapping the pixel region 12 in a planar view. Then, in a planar view, the vertical scanning circuit unit 110, the horizontal scanning circuit unit 111, the readout circuit 112, the output circuit 114, and the control pulse generating unit 115 are arranged so as to overlap between the end of the sensor substrate 11 and the end of the pixel region 12. In other words, the sensor substrate 11 has the pixel region 12 and a non-pixel region arranged around the pixel region 12. Then, in a planar view, the vertical scanning circuit unit 110, the horizontal scanning circuit unit 111, the readout circuit 112, the output circuit 114, and the control pulse generating unit 115 are arranged in a region overlapping the non-pixel region.

The configuration of the pixel region 12 shown in Figure 4 will be described. The pixel region 12 is a region in which pixels capable of photoelectric conversion are arranged. In Figure 4, the pixel region 12 includes a first region 10a, a second region 10b, and a third region 10c, and the pixel 101 includes an effective pixel 13, a dummy pixel 14, and an optical black pixel (OB pixel) 15.

The first region 10a is configured by arranging effective pixels 13 having photoelectric conversion elements 10 including APDs in a two-dimensional array in a planar view. The effective pixels 13 are pixels that output photon detection signals in response to the detection of photons, and are typically pixels for forming an image. The number of rows and columns of pixels included in the first region 10a is not particularly limited.

The second region 10b is composed of multiple dummy pixels 14 arranged in a two-dimensional array in a plan view. In the planar configuration shown in FIG. 1, the dummy pixels 14 are arranged in the pixel region 12 in a range other than the first region 10a and the third region 10c, forming the second region 10b. In addition, since the dummy pixels 14 are arranged on the outermost periphery of the pixel region 12, the outer periphery of the second region 10b is the end of the pixel region 12. The dummy pixels 14 are photoelectric conversion elements including APDs, but the dummy pixels 14 do not output photon detection signals to the external signal POUT.

The third region 10c is composed of a plurality of OB pixels 15 arranged in a two-dimensional array in a plan view. The number of rows and columns of the OB pixels 15 included in the third region 10c is not particularly limited. At least a part of the outer periphery of the third region 10c is in contact with the second region 10b. The OB pixels 15 are light-shielded pixels for outputting signals that are not dependent on external light. There may be a plurality of third regions 10c in one pixel region 12. In the pixel region 12 shown in FIG. 4, independent island-shaped third regions 10c are provided in two locations, one perpendicular to the first region 10a and one horizontal to the first region 10a.

The configuration of the photoelectric conversion element will be explained using the range A-F of the cross section of the photoelectric conversion device shown in Figure 5. The reference characters A to F in the cross section shown in Figure 5 correspond to the reference characters A to F in Figure 1.

The photoelectric conversion device shown in FIG. 5 is a stacked type photoelectric conversion device in which two substrates, a sensor substrate 11 and a circuit substrate 21, are stacked and electrically connected. The sensor substrate 11 has a first semiconductor layer 302 having a photoelectric conversion element 102 described later, and a first wiring structure 303. The circuit substrate 21 has a second semiconductor layer 402 having circuits such as a signal processing unit 103 described later, and a second wiring structure 403. The photoelectric conversion device 100 is configured by stacking the second semiconductor layer 402, the second wiring structure 403, the first wiring structure 303, and the first semiconductor layer 302 in this order.

The range A-B in FIG. 5 corresponds to one pixel of the photoelectric conversion element 102 of the photoelectric conversion device. Note that the range A-B is the range from one of the pixel separation sections 324 described below to the pixel separation section 324 of an adjacent pixel. Alternatively, it can be said to be the range of one pixel covered by one microlens described below.

The structure and function of the photoelectric conversion element 102 will be described. The photoelectric conversion element 102 has a first semiconductor region 311 of N type, a fourth semiconductor region 314, a sixth semiconductor region 316, and a seventh semiconductor region 317. The photoelectric conversion element 102 further includes a second semiconductor region 312, a third semiconductor region 313, and a fifth semiconductor region 315 of P type.

In this embodiment, in the cross section shown in FIG. 5, an N-type first semiconductor region 311 is formed near the surface facing the light incident surface, and an N-type seventh semiconductor region 317 is formed around it. A P-type second semiconductor region 312 is formed at a position overlapping the first semiconductor region and the second semiconductor region in a planar view. An N-type fourth semiconductor region 314 is further disposed at a position overlapping the second semiconductor region 312 in a planar view, and an N-type sixth semiconductor region 316 is formed around it.

The first semiconductor region 311 has a higher N-type impurity concentration than the fourth semiconductor region 314 and the seventh semiconductor region 317. A PN junction is formed between the P-type second semiconductor region 312 and the N-type first semiconductor region 311, but by making the impurity concentration of the second semiconductor region 312 lower than the impurity concentration of the first semiconductor region 311, the entire region of the second semiconductor region 312 becomes a depletion layer region. Furthermore, this depletion layer region extends to a portion of the first semiconductor region 311, and a strong electric field is induced in the extended depletion layer region. This strong electric field causes avalanche multiplication in the depletion layer region that extends to a portion of the first semiconductor region 311, and a current based on the amplified charge is output as a signal charge. When light incident on the photoelectric conversion device 102 is photoelectrically converted and avalanche multiplication occurs in this depletion layer region (avalanche multiplication region), the generated first conductivity type charge is collected in the first semiconductor region 311.

A trench-based uneven structure 325 is formed on the surface of the semiconductor layer on the light incident side. The uneven structure 325 is surrounded by a P-type third semiconductor region 313, and scatters light incident on the photoelectric conversion element 102. Since the incident light travels diagonally inside the photoelectric conversion element, an optical path length equal to or greater than the thickness of the semiconductor layer can be ensured, and light with longer wavelengths can be photoelectrically converted compared to a case in which the uneven structure 325 is not present. In addition, the uneven structure 325 prevents the incident light from being reflected within the substrate, which has the effect of improving the photoelectric conversion efficiency of the incident light.

The fourth semiconductor region 314 and the uneven structure 325 are formed so as to overlap in a planar view. The area where the fourth semiconductor region 314 and the uneven structure 325 overlap in a planar view is larger than the area of the portion of the fourth semiconductor region 314 that does not overlap with the uneven structure 325. Charges generated at a position far from the avalanche multiplication region formed between the first semiconductor region 311 and the fourth semiconductor region 314 take a longer time to travel to the avalanche multiplication region than charges generated at a position close to the avalanche multiplication region. This may increase timing jitter. By arranging the fourth semiconductor region 314 and the uneven structure 325 at a position where they overlap in a planar view, the electric field deep in the photodiode can be increased, and the collection time of charges generated at a position far from the avalanche multiplication region can be shortened, thereby reducing timing jitter.

In addition, the third semiconductor region 313 covers the uneven structure three-dimensionally, which suppresses the generation of thermally excited charges at the interface of the uneven structure. This suppresses the DCR (Dark Count Rate) of the photoelectric conversion element.

Pixels are separated by a pixel separation section 324 having a trench structure, and a P-type fifth semiconductor region 315 formed around the pixel separation section separates adjacent photoelectric conversion elements by a potential barrier. Since the photoelectric conversion elements are also separated by the potential of the fifth semiconductor region 315, a trench structure such as the pixel separation section 324 is not essential as a pixel separation section. In addition, when the pixel separation section 324 is provided, its depth and position are not limited to the configuration in FIG. 5. The pixel separation section 324 may be a DTI (deep trench isolation) that penetrates the semiconductor layer, or a DTI that does not penetrate the semiconductor layer. Metal may be embedded in the DTI to improve light blocking performance. The pixel separation section 324 may be configured to surround the entire periphery of the photoelectric conversion element in a plan view, or may be configured only on the opposite side of the photoelectric conversion element, for example.

The distance from the pixel separation section to the pixel separation section of an adjacent pixel or the pixel located at the nearest position can also be considered to be the size of one photoelectric conversion element 102. When the size of one photoelectric conversion element 102 is L, the distance d from the light incident surface to the avalanche multiplication region satisfies L√2/4<d<L×√2. When the size and depth of the photoelectric conversion element satisfy this relational expression, the strength of the electric field in the depth direction near the first semiconductor region 311 and the strength of the electric field in the planar direction are approximately the same. Since the variation in the time required for charge collection is suppressed, the occurrence of timing jitter can be reduced.

A pinning film 321, a planarization film 322, and a microlens 323 are further formed on the light incident surface side of the semiconductor layer. A filter layer (not shown) may also be disposed on the light incident surface side. The filter layer may be a variety of optical filters such as a color filter, an infrared light cut filter, or a monochrome filter. The color filter may be an RGB color filter, an RGBW color filter, or the like.

The photoelectric conversion elements arranged in the ranges B-E have the same basic configuration. Note that in the ranges A-C and D-F corresponding to the second and third regions 10b and 10c, a light shielding portion 326 is provided on the light incident surface side.

The correspondence between the plan view of pixel region 12 shown in FIG. 4 and the cross-sectional view of pixel region 12 shown in FIG. 5 will be explained.

The range A-B in the cross sections of Figures 4 and 5 corresponds to the third region 10c. A light-shielding portion 326 is formed on the light-incident surface side of the semiconductor layer to provide light shielding.

The range B-C in the cross section of Figures 4 and 5 corresponds to the second region 10b. As with the OB pixels, a light shielding portion 326 is formed on the light incident surface side of the semiconductor layer to provide light shielding, but light shielding of the dummy pixels 14 arranged in the second region 10b is not essential. Also, each of the dummy pixels 14 arranged in the second region 10b is configured not to output a signal based on light detection. The shortest distance from the end of the second region 10b at the boundary with the third region 10c to the end of the second region 10b at the boundary with the first region 10a is defined as 601.

The area C-D in the cross sections of Figures 4 and 5 corresponds to the first region 10a.

The range D-E in the cross sections of Figures 4 and 5 corresponds to the second region 10b. By disposing dummy pixels 14 on the outermost periphery of the pixel region 12, the shape of the pixel region can be stabilized. The shortest distance from the end of the second region 10b, which is the boundary with the first region 10a, to the end of the second region 10b, which is the outer periphery of the pixel region 12, is defined as 602.

The area E-F in the cross sections of Figures 4 and 5 is a non-pixel region on the sensor substrate 11.

Of the light incident on the first region 10a, obliquely incident light may leak into the third region 10c. Because the third region 10c is a light-shielded pixel for outputting a signal that is not dependent on external light, light leakage makes it impossible to obtain a correct signal. Also, avalanche emission may occur due to avalanche multiplication in the first region 10a. Avalanche emission is a phenomenon in which a large number of electrons or holes generated by avalanche multiplication recombine with charges of opposite polarity to generate photons. When photons generated by avalanche emission leak into adjacent pixels, a false signal is generated, leading to a decrease in image quality.

In this embodiment, therefore, a third region 10b in which dummy pixels 14 are arranged is provided between the third region 10a in which effective pixels are arranged and the third region 10c in which OB pixels are arranged, and the third region 10a and the third region 10c are sufficiently separated from each other. This reduces the intrusion of light and photons into the OB pixels, and prevents degradation of image quality.

In addition, by disposing dummy pixels 14 between the first region 10a and the third region 10c or on the outer periphery of the pixel region 12, the pixel arrangement in the pixel region 12 can be stabilized.

At least a few dummy pixels 14 may be arranged along the edge of the pixel region 12, but the number of dummy pixels 14 arranged between the first region 10a and the third region 10c is greater than the number of dummy pixels arranged between the first region and the edge of the pixel region 12. Between the first region 10a and the third region 10c, ten times more dummy pixels 14 than the dummy pixels 14 arranged at the edge of the pixel region 12 may be arranged. Specifically, it is preferable to arrange 20 or more pixels between the first region 10a and the third region 10c, but the number of dummy pixels 14 is not limited to this. Therefore, the shortest distance 601 between the outer periphery of the first region 10a and the outer periphery of the third region 10c is longer than the shortest distance 602 between the outer periphery of the first region 10a and the outer periphery of the second region 10b. In other words, when a shortest distance 601 is determined, the number of pixels arranged on the shortest distance in a planar view is greater than the number of pixels arranged on the shortest distance 602 in a planar view. In this embodiment, the shortest distance 601 between the outer periphery of the first region 10a and the outer periphery of the third region 10c is ten times greater than the shortest distance 602 between the outer periphery of the first region 10a and the outer periphery of the second region 10b. This relationship holds true for the first region 10a and each third region 10c even when multiple third regions 10c are formed within the pixel region 12.

In other words, the second region 10b has a first portion and a second portion that contact the end of the pixel region 12. For example, the first portion of the second region 10b, the first region 10a, the second portion of the second region 10b, and the third region 10c are arranged vertically from the end of the pixel region 12. At this time, the vertical width of the second portion of the second region 10b is wider than the vertical width of the first portion of the second region 10b. Furthermore, when the second region 10b has a third portion that contacts the end of the pixel region 12, for example, the first region 10a and the third portion of the second region 10b are arranged horizontally intersecting the vertical direction in which the first and second portions of the second region 10b are arranged. At this time, the vertical width of the second portion of the second region 10b is wider than the horizontal width of the third portion of the second region 10b.

In FIG. 1, the first region 10a, the second region 10b, and the third region 10c are each represented as a rectangle, but the shape of each region is not limited to this and may be, for example, a circle or a polygon.

Figure 6 is an example of a block diagram including an equivalent circuit of an effective pixel 13.

The APD201 generates pairs of charges according to the incident light through photoelectric conversion. A voltage VL (first voltage) is supplied to the anode of the APD201. A voltage VH (second voltage) higher than the voltage VL supplied to the anode is supplied to the cathode of the APD201. A reverse bias voltage is supplied to the anode and cathode such that the APD201 performs avalanche multiplication. By supplying such a voltage, the charges generated by the incident light undergo avalanche multiplication, generating an avalanche current.

When a reverse bias voltage is supplied, there is a Geiger mode in which the anode and cathode are operated at a potential difference greater than the breakdown voltage, and a linear mode in which the anode and cathode are operated at a potential difference close to or less than the breakdown voltage.

An APD operated in Geiger mode is called a SPAD. For example, the voltage VL (first voltage) is -30 V, and the voltage VH (second voltage) is 1 V. The APD 201 may be operated in either linear mode or Geiger mode. A SPAD is preferable because the potential difference is larger than that of a linear mode APD, making the effect of withstanding voltage more pronounced.

The quench element 202 is connected to the APD 201 and a power supply that supplies a voltage VH, which is a drive voltage. The quench element 202 functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication, suppressing the voltage supplied to the APD 201 and suppressing avalanche multiplication (quench operation). The quench element 202 also has the function of returning the voltage supplied to the APD 201 to voltage VH by passing a current equivalent to the voltage drop caused by the quench operation (recharge operation).

The signal processing unit 103 has a waveform shaping unit 210, a counter circuit 211, and a selection circuit 212. In this specification, the signal processing unit 103 may have any one of the waveform shaping unit 210, the counter circuit 211, and the selection circuit 212.

The waveform shaping unit 210 shapes the potential change of the cathode of the APD 201 obtained when a photon is detected, and outputs a pulse signal. For example, an inverter circuit is used as the waveform shaping unit 210. In FIG. 7, an example in which one inverter is used as the waveform shaping unit 210 is shown, but a circuit in which multiple inverters are connected in series may be used, or other circuits that have a waveform shaping effect may be used.

The counter circuit 211 counts the pulse signal output from the waveform shaping unit 210 and holds the count value. When a control pulse pRES is supplied via the drive line 213, the signal held in the counter circuit 211 is reset.

The selection circuit 212 receives a control pulse pSEL from the vertical scanning circuit unit 110 in FIG. 6 via a drive line 214 (not shown in FIG. 6) in FIG. 7, and switches between electrical connection and non-connection between the counter circuit 211 and the signal line 113. The selection circuit 212 includes, for example, a buffer circuit for outputting a signal.

A switch such as a transistor may be disposed between the quench element 202 and the APD 201, or between the photoelectric conversion element 102 and the signal processing unit 103, to switch the electrical connection. Similarly, the supply of the voltage VH or voltage VL supplied to the photoelectric conversion element 102 may be electrically switched using a switch such as a transistor.

In this embodiment, a configuration using the counter circuit 211 is shown. However, instead of the counter circuit 211, the photoelectric conversion device 100 may be configured to acquire the pulse detection timing using a time-to-digital converter (TDC) and a memory. In this case, the generation timing of the pulse signal output from the waveform shaping unit 210 is converted into a digital signal by the TDC. To measure the timing of the pulse signal, the TDC is supplied with a control pulse pREF (reference signal) from the vertical scanning circuit unit 110 in FIG. 1 via a drive line. The TDC acquires, as a digital signal, a signal when the input timing of the signal output from each pixel via the waveform shaping unit 210 is set as a relative time based on the control pulse pREF.

Figure 7 is a diagram showing the relationship between the operation of APD201 and the output signal.

Figure 7(a) is a diagram of the APD 201, quench element 202, and waveform shaping unit 210 of Figure 7. Here, the input side of the waveform shaping unit 210 is nodeA, and the output side is nodeB. Figure 7(b) shows the waveform change of nodeA in Figure 7(a), and Figure 7(c) shows the waveform change of nodeB in Figure 7(a).

Between time t0 and time t1, a potential difference of VH-VL is applied to APD201 in Figure 7(a). When a photon is incident on APD201 at time t1, avalanche multiplication occurs in APD201, an avalanche multiplication current flows through quench element 202, and the voltage of nodeA drops. When the amount of voltage drop becomes even larger and the potential difference applied to APD201 becomes smaller, avalanche multiplication of APD201 stops as at time t2, and the voltage level of nodeA does not drop more than a certain value. After that, between time t2 and time t3, a current that compensates for the voltage drop from voltage VL flows through nodeA, and at time t3, nodeA settles to its original potential level. At this time, the part of the output waveform at node A that exceeds a certain threshold is shaped by the waveform shaping unit 210 and output as a signal at node B.

Figures 8(a) to (c) are diagrams showing an image of the circuit configuration of the photoelectric conversion device according to this embodiment. Figure 8(a) shows the connection relationship between the effective pixels 13 or OB pixels 15, the signal processing unit 103, and the signal line 113. Figures 8(b) and (c) show an example of the connection relationship between the dummy pixels 14, the signal processing unit 103, and the signal line 113. The effective pixels 13 are pixels that output a photon detection signal to the signal line 113. In other words, they are pixels used for the purpose of light detection. The dummy pixels 14 are pixels that do not output a photon detection signal to the signal line 113. In other words, they are pixels used for purposes other than light detection.

The operation of the effective pixel 13 will be explained using Figures 8(a) and 9.

The effective pixel 13 is composed of the APD 201, the recharge circuit 301, and the processing circuit 302. When the clock signal pCLK becomes Low, it drives the recharge circuit 301 and can recharge the APD 201 to a bias voltage that can perform avalanche multiplication in Geiger mode. The recharge circuit 301 may be any circuit that can switch the resistance value between the APD 201 and the power supply, such as a P-type MOS transistor. In addition, when the clock signal pCLK becomes High after recharging to a bias voltage that can perform avalanche multiplication, the cathode terminal and the power supply voltage VH are disconnected and the cathode terminal is in a floating state. When avalanche multiplication occurs due to the photocharge generated by the incidence of photons on the APD 201, the cathode voltage VC drops and the difference between the anode voltage and the cathode voltage drops below the breakdown voltage of the APD 201. The change in the cathode voltage VC is detected by the processing circuit 302, and the photons are detected as a signal. The effective pixel 13 can read out the photon detection result of the pixel by outputting the result of photon detection during the exposure period from the processing circuit 302 to the signal line 113.

Figure 9 is a timing diagram showing an example of driving the effective pixels 13 during the exposure period. Using Figure 9, we will explain the change in the cathode voltage VC under the control of the clock signal pCLK, and the basic photon counting operation. We will also explain clock recharge driving, which controls the number of photons detected during the exposure period by periodically setting the clock signal pCLK to Low during the exposure period.

At time T1, when the clock signal pCLK goes low, the cathode voltage VC is recharged from potential V1 to potential VH. At this time, the voltage applied to APD201 is potential VH - potential VL. If the breakdown voltage of APD201 is potential V1 - potential VL, then the voltage applied is in excess of the breakdown voltage by the potential difference of potential VH - potential V1, and avalanche multiplication is possible in Geiger mode.

When a photon is incident on APD201 at time T2, avalanche multiplication occurs in APD201, and the cathode voltage VC drops from potential VH to potential V1. At this time, the bias voltage of APD201 is potential V1-potential VL, which drops to a voltage below the breakdown voltage. The processing circuit 302 detects that the cathode voltage VC has changed to a voltage below the threshold voltage Vth, and counts up the counter value from n to n+1.

Next, when a photon is incident at time T3, a bias voltage less than the breakdown voltage is applied to the APD 201, so avalanche multiplication due to Geiger mode does not occur. However, the potential difference between potential VL and potential V1 is a reverse bias voltage less than the breakdown voltage, and a reverse current is generated due to the photocharge, so the cathode voltage VC drops to potential V2, which is lower than potential V1. This voltage drop in the cathode voltage VC below the breakdown voltage due to the reverse current does not contribute to the count-up of the counter, but is a voltage drop that must be taken care of in the inactive pixel 320, as described below.

At time T4, the clock signal pCLK goes low, and the cathode voltage VC is recharged to the potential VH again. At time T5, the clock signal pCLK goes low, but the cathode voltage VC does not change because it has been recharged to the potential VH.

When a photon is incident at time T6, avalanche multiplication occurs, the cathode voltage VC drops, and the counter count is incremented to n+2. This periodic recharge operation is called clock recharge drive, and the number of photon detections within the exposure period is controlled with the number of recharges as an upper limit.

On the other hand, the dummy pixel 14 differs from the effective pixel 13 in that the APD 201, the processing circuit 302, and the signal line 113 are not connected, as shown in Figures 8(b) and (c). Therefore, when the APD 201 is in a state where avalanche multiplication is possible due to the clock signal pCLK, even if a photon is incident and the cathode voltage VC changes, the result of the photon detection cannot be output to the signal line 113.

8(b) and (c), the APD 201 of the dummy pixel 14 is not connected to the signal line 113, and there is no need to recharge it for photon detection. However, if the cathode terminal is left floating for a long period of time, a voltage drop phenomenon such as that at time T3 in FIG. 9 may occur multiple times, causing the cathode voltage VC to continue to drop. Therefore, in this embodiment, the dummy pixel 14 also performs a recharge operation to suppress the drop in the cathode voltage VC. If the input of the dummy pixel 14 is kept in a High state, the cathode terminal of the APD 201 is maintained in a floating state. As described in the explanation of FIG. 9, if the cathode terminal is left floating after avalanche multiplication occurs once, avalanche multiplication in the Geiger mode will not occur, but a reverse current caused by seed charges such as photocharges may flow. In the example of FIG. 9, the potential of the cathode terminal drops from potential V1 to potential V2, but if the state of not recharging continues after that, the cathode terminal will continue to drop every time a seed charge is generated. Eventually, a potential exceeding the withstand voltage of the circuit element to which the potential of the cathode voltage VC is supplied, such as the processing circuit 302, will be applied, which may damage the circuit element.

In this way, in the first embodiment of the present invention, the third region 10a in which the effective pixels 13 are arranged and the third region 10c in which the OB pixels 15 are arranged are sufficiently separated by the third region 10b in which the dummy pixels 14 are arranged. This reduces the intrusion of light and the leakage of photons into the OB pixels, and prevents degradation of image quality. Furthermore, by periodically recharging the dummy pixels 14, there is an effect of preventing potential changes at the APD terminals in the dummy pixels 14.

Second Embodiment
The photoelectric conversion device according to this embodiment will be described with reference to Fig. 10 and Fig. 11. Parts common to Fig. 1 to Fig. 9 are given the same numbers, and differences from the first embodiment will be mainly described. The photoelectric conversion device according to this embodiment differs from the first embodiment in the driving of the dummy pixels 14.

Figure 10(a) shows the configuration of an effective pixel 13, which is the same configuration as Figure 8(a).

Figure 10 (b) shows the circuit configuration of the dummy pixel 14 of the photoelectric conversion device according to this embodiment. In the first embodiment, the timing of recharging the APD was controlled by a control signal pCLK common to the effective pixels 13 and the dummy pixels 14. In the second embodiment, the dummy pixels 14 are recharged at any timing, regardless of the timing of recharging the effective pixels 13. For example, the dummy pixels 14 are controlled by a second control signal pCLK2 that has a different phase from the control signal pCLK of the effective pixels 13.

As shown in FIG. 11, the effective pixels 13 are periodically recharged with a pulse width τ during the exposure period Tex by the clock signal pCLK, and the recharge period is Tp1. The recharge period of the clock signal pCLK2 of the dummy pixels 14 is Tp2, and the pixels are recharged with a constant pulse width τ' without distinguishing between inside and outside the exposure period Tex.

Here, the exposure period Tex>pulse width τ'. By not making the pulse width τ' unnecessarily long, the frequency with which current flows through the APD 201 of the dummy pixel 14 is reduced compared to the effective pixel 13, thereby reducing the power consumption of the dummy pixel 14.

The pulse width τ and the pulse width τ' may be equal or different. In the effective pixel 13, it is desirable that the pulse width τ is as narrow as possible to shorten the recharge time, but in the dummy pixel 14, the pulse width τ' may be wider than the pulse width τ. On the other hand, the pulse width τ of the effective pixel 13 requires a pulse width τ corresponding to a period sufficient for the cathode voltage VC to be recharged to a predetermined voltage, but the dummy pixel 14 does not need to consider the variation in the cathode voltage VC after recharge. Therefore, τ' can be shortened within a range in which the effect of recharging can be obtained, and power consumption can be reduced. By making the pulse width τ and the pulse width τ' equal, it is possible to share part of the wiring used for generating and transmitting the pulses of the clock signal pCLK and the clock signal pCLK2.

Furthermore, the recharge period Tp1 of the effective pixel 13 is equal to or less than the recharge period Tp2 of the dummy pixel 14. This relationship prevents damage to the circuit elements caused by a voltage drop in the cathode voltage VC, while reducing the number of pulses per unit time of the recharge signal of the dummy pixel 14 and suppressing the power consumption of the dummy pixel 14.

Third Embodiment
The arrangement of each region within the pixel region is not limited to that shown in FIG.

12 shows an example of a planar layout of the pixel region 12. In the arrangement shown in FIG. 12, the second region 10b is further divided into three types: second region 10b-1, second region 10b-2, and second region 10b-3. The second region 10b-1 is a dummy pixel 14 configured so as not to output a signal as described in the first and second embodiments. The second region 10b-2 is a dummy pixel 16 with a different configuration from the first and second embodiments. In other words, it is a dummy pixel controlled so as not to output a signal. The second region 10b-3 is a test pixel 17 used to check the normality of the circuit. In other words, the pixels arranged in the second region 10b may be pixels used for purposes other than light detection.

The dummy pixels 16 may be configured to be controlled so as not to output a signal based on photon detection even when electrically connected to the signal line 113. Such dummy pixels 16 can output a signal based on photon detection depending on the control situation, and can be used to check, for example, how light leaks from the effective pixels 13 to the OB pixels 15 and the effects of avalanche light emission.

Figures 13(a) to (c) show a schematic configuration of the test pixel 17. The test pixel 17 differs from the dummy pixel 14 in that it is connected to an external signal POUT. The test pixel 17 includes a test processing circuit 303 instead of the processing circuit 302 of the dummy pixel 14. Even if the test processing circuit 303 receives the output of the cathode voltage VC of the APD 201, it does not output information regarding changes in the cathode voltage VC, i.e., photon detection information, to the signal line 113. In other words, it is a pixel used for purposes other than light detection.

The test processing circuit 303 includes a test circuit 304, and outputs a signal for checking the normality of the circuit. A test signal TEST is input to the test processing circuit 303. In other words, the test processing circuit 303 is a circuit that outputs a signal based on an input from an input node different from the output node of the avalanche photodiode. Here, TEST may be a time-varying signal or a fixed value. It may also be generated either inside or outside the test pixel 17. For example, by having the test circuit 304 output a fixed value, the normality of the output path in FIG. 13(a) from the test processing circuit 303 to the external signal POUT can be checked.

Also, as shown in Figures 13(b) and (c), a function may be provided in which a control signal pCLK is input to a test processing circuit 303, and the test circuit 304 counts the number of pulses of the control signal pCLK to check the normality of the control signal pCLK. In this case, the signal input to the recharge circuit 301 of the test pixel 17 may be pCLK as shown in Figure 13(b), or may be a signal other than pCLK as shown in Figure 13(c). Although a ground voltage is shown in Figure 13(c) as an example of a fixed value other than pCLK, it may be, for example, a clock signal having a different phase from pCLK.

Fourth Embodiment
The photoelectric conversion device according to this embodiment is different from the photoelectric conversion device according to the first embodiment in the configuration of the dummy pixels 14. Configuration examples of the dummy pixels in the photoelectric conversion device according to the first embodiment are as shown in Figures 8(b) and (c). The configuration of the dummy pixels 13 in this embodiment is shown in Figures 14(a) to (c).

The dummy pixels 14 shown in Figs. 14(a) and (b) each have a feature that multiple APDs 201 are connected in parallel to one recharge circuit 301. Although three APDs 201 are connected as an example in Figs. 14(a) and (b), the number of APDs 201 connected in parallel is not limited to this. In addition, the dummy pixel 14 shown in Fig. 14(a) has the APD 201 and the waveform generating unit 210 connected, but as shown in Fig. 14(b), the APD 201 and the waveform generating unit 210 may not be connected. The dummy pixel 14 is a pixel that does not output a signal based on the charge generated by the APD 201 to the signal line 113. In other words, it is a pixel that is used for purposes other than light detection.

The recharge timing of the recharge circuit 301 of the dummy pixel 14 may be controlled by a control signal pCLK common to the effective pixel 13 and the dummy pixel 14 as shown in the first embodiment. As shown in the second embodiment, the recharge circuit 301 of the dummy pixel 14 may be configured to be recharged at any timing regardless of the recharge timing of the recharge circuit 301 of the effective pixel 13.

In this embodiment, by connecting one recharge circuit 301 to multiple dummy pixels 14, the total number of recharge circuits 301 in the entire pixel area can be reduced, leading to reduced power consumption.

In addition, the frequency of recharge required is reduced for dummy pixels 14 that receive a small amount of light. For example, at the boundary between the first and second regions, even if the second region is shielded, light is likely to leak from the first region into the second region. Therefore, the frequency of photoelectric conversion in the dummy pixels 14 due to the leaked light is relatively high, and the frequency of recharging the recharge circuit 301 is also high. For example, the dummy pixels 14 located at C or D in FIG. 5 are located at the boundary between the light-shielded region and the effective pixel region. Therefore, it is desirable that the number of APDs 201 connected in parallel to one recharge circuit 301 in these dummy pixels 14 is about two or three. On the other hand, the amount of light received by the dummy pixels 14 located farther from the unshielded first region is attenuated, so the number of APDs 201 that can be connected in parallel to one recharge circuit 301 may be increased compared to the dummy pixels 14 near the boundary. For example, the number of APDs 201 that can be connected in parallel to one recharge circuit 301 in the dummy pixel 14 located at B in FIG. 4 is greater than that in the dummy pixel 14 located at C or D. By varying the number of APDs 201 connected in parallel according to the arrangement of the dummy pixels 14, it is possible to further reduce the number of recharge circuits 301 in the entire pixel region, leading to further reduction in power consumption. In other words, the number of avalanche photodiodes in the first dummy pixel that is located a long distance from the boundary between the first region and the second region is greater than the number of avalanche photodiodes in the second dummy pixel that is located a short distance from the boundary between the first region and the second region.

In order to suppress the decrease in the cathode voltage VC over time, it is sufficient that avalanche multiplication does not occur in the dummy pixel 14. In other words, it is sufficient that a reverse bias voltage is not applied to the dummy pixel 14. Therefore, it is possible to achieve further reduction in power consumption by not providing a recharge circuit 301 in the dummy pixel 14 and instead inputting a fixed voltage. For example, as shown in FIG. 14(c), wiring may be provided so that the voltage VL is supplied to both the cathode terminal and the anode terminal of the APD 201.

Fifth Embodiment
The photoelectric conversion system according to this embodiment will be described with reference to Fig. 15. Fig. 15 is a block diagram showing a schematic configuration of the photoelectric conversion system according to this embodiment.

The photoelectric conversion devices described in the first to third embodiments above can be applied to various photoelectric conversion systems. Examples of applicable photoelectric conversion systems include digital still cameras, digital camcorders, surveillance cameras, copiers, fax machines, mobile phones, vehicle-mounted cameras, and observation satellites. Camera modules equipped with an optical system such as a lens and an imaging device are also included in photoelectric conversion systems. Figure 15 shows a block diagram of a digital still camera as an example of these.

The photoelectric conversion system illustrated in FIG. 15 includes an image capture device 1004, which is an example of a photoelectric conversion device, and a lens 1002 that forms an optical image of a subject on the image capture device 1004. It also includes an aperture 1003 for varying the amount of light passing through the lens 1002, and a barrier 1001 for protecting the lens 1002. The lens 1002 and the aperture 1003 are an optical system that focuses light on the image capture device 1004. The image capture device 1004 is a photoelectric conversion device according to any of the above embodiments, and converts the optical image formed by the lens 1002 into an electrical signal.

The photoelectric conversion system also has a signal processing unit 1007, which is an image generating unit that generates an image by processing the output signal output from the imaging device 1004. The signal processing unit 1007 performs various corrections and compression as necessary to output image data. The signal processing unit 1007 may be formed on a semiconductor substrate on which the imaging device 1004 is provided, or may be formed on a semiconductor substrate separate from the imaging device 1004.

The photoelectric conversion system further has a memory unit 1010 for temporarily storing image data, and an external interface unit (external I/F unit) 1013 for communicating with an external computer or the like. The photoelectric conversion system further has a recording medium 1012 such as a semiconductor memory for recording or reading out imaging data, and a recording medium control interface unit (recording medium control I/F unit) 1011 for recording or reading out data on the recording medium 1012. The recording medium 1012 may be built into the photoelectric conversion system, or may be removable.

The photoelectric conversion system further includes an overall control/calculation unit 1009 that performs various calculations and controls the entire digital still camera, and a timing generation unit 1008 that outputs various timing signals to the image capture device 1004 and the signal processing unit 1007. Here, timing signals and the like may be input from the outside, and the photoelectric conversion system only needs to include at least the image capture device 1004 and the signal processing unit 1007 that processes the output signal output from the image capture device 1004.

The imaging device 1004 outputs an imaging signal to the signal processing unit 1007. The signal processing unit 1007 performs a predetermined signal processing on the imaging signal output from the imaging device 1004 and outputs image data. The signal processing unit 1007 generates an image using the imaging signal.

In this way, according to this embodiment, it is possible to realize a photoelectric conversion system that applies the photoelectric conversion device (imaging device) of any of the above embodiments.

Sixth Embodiment
The photoelectric conversion system and the moving object of this embodiment will be described with reference to Fig. 16. Fig. 16 is a diagram showing the configuration of the photoelectric conversion system and the moving object of this embodiment.

Figure 16 (a) shows an example of a photoelectric conversion system related to an in-vehicle camera. The photoelectric conversion system 2300 has an image capture device 2310. The image capture device 2310 is a photoelectric conversion device described in any of the above embodiments. The photoelectric conversion system 2300 has an image processing unit 2312 that performs image processing on multiple image data acquired by the image capture device 2310, and a parallax acquisition unit 2314 that calculates parallax (phase difference of parallax images) from multiple image data acquired by the photoelectric conversion system 2300. The photoelectric conversion system 2300 also has a distance acquisition unit 2316 that calculates the distance to an object based on the calculated parallax, and a collision determination unit 2318 that determines whether or not there is a possibility of collision based on the calculated distance. Here, the parallax acquisition unit 2314 and the distance acquisition unit 2316 are examples of distance information acquisition means that acquire distance information to the object. In other words, the distance information is information on the parallax, the defocus amount, the distance to the object, etc. The collision determination unit 1318 may use any of these distance information to determine the possibility of a collision. The distance information acquisition means may be realized by dedicated hardware or by a software module. It may also be realized by an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or the like, or may be realized by a combination of these.

The photoelectric conversion system 2300 is connected to a vehicle information acquisition device 2320, and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The photoelectric conversion system 2300 is also connected to a control ECU 2330, which is a control unit that outputs a control signal to generate a braking force for the vehicle based on the judgment result of the collision judgment unit 2318. The photoelectric conversion system 2300 is also connected to an alarm device 2340 that issues an alarm to the driver based on the judgment result of the collision judgment unit 2318. For example, if the judgment result of the collision judgment unit 2318 indicates that there is a high possibility of a collision, the control ECU 2330 applies the brakes, releases the accelerator, suppresses engine output, etc., to avoid the collision and reduce damage by performing vehicle control. The alarm device 2340 warns the user by sounding an alarm, displaying alarm information on the screen of a car navigation system, etc., or vibrating the seat belt or steering wheel.

In this embodiment, the surroundings of the vehicle, for example the front or rear, are imaged by the photoelectric conversion system 2300. FIG. 16(b) shows a photoelectric conversion system for imaging the area in front of the vehicle (imaging range 2350). The vehicle information acquisition device 2320 sends instructions to the photoelectric conversion system 2300 or the imaging device 2310. This configuration can further improve the accuracy of distance measurement.

Although the above describes an example of control to prevent collisions with other vehicles, the system can also be applied to automatic driving control to follow other vehicles and automatic driving control to prevent vehicles from going outside their lanes. Furthermore, the photoelectric conversion system is not limited to vehicles such as automobiles, but can be applied to moving bodies (moving devices) such as ships, aircraft, and industrial robots. In addition, the system can be applied not only to moving bodies, but also to a wide range of equipment that uses object recognition, such as intelligent transport systems (ITS).

Seventh Embodiment
The photoelectric conversion system of this embodiment will be described with reference to Fig. 17. Fig. 17 is a block diagram showing an example of the configuration of a range image sensor which is the photoelectric conversion system of this embodiment.

As shown in FIG. 17, the distance image sensor 401 is configured to include an optical system 407, a photoelectric conversion device 408, an image processing circuit 404, a monitor 405, and a memory 406. The distance image sensor 401 can obtain a distance image according to the distance to the subject by receiving light (modulated light or pulsed light) that is projected from a light source device 409 toward the subject and reflected by the surface of the subject.

The optical system 407 is composed of one or more lenses, and guides image light (incident light) from the subject to the photoelectric conversion device 408, forming an image on the light receiving surface (sensor section) of the photoelectric conversion device 408.

The photoelectric conversion device 408 is one of the photoelectric conversion devices according to the above-mentioned embodiments, and a distance signal indicating the distance determined from the light receiving signal output from the photoelectric conversion device 408 is supplied to the image processing circuit 404.

The image processing circuit 404 performs image processing to construct a distance image based on the distance signal supplied from the photoelectric conversion device 408. The distance image (image data) obtained by this image processing is then supplied to the monitor 405 for display, or supplied to the memory 406 for storage (recording).

In the distance image sensor 401 configured in this manner, by applying the photoelectric conversion device described above, it is possible to obtain, for example, a more accurate distance image as the pixel characteristics improve.

Eighth embodiment
The photoelectric conversion system of this embodiment will be described with reference to Fig. 18. Fig. 18 is a diagram showing an example of a schematic configuration of an endoscopic surgery system which is the photoelectric conversion system of this embodiment.

Figure 18 shows an operator (doctor) 1131 performing surgery on a patient 1132 on a patient bed 1133 using an endoscopic surgery system 1150. As shown in the figure, the endoscopic surgery system 1150 is composed of an endoscope 1100, a surgical tool 1110, and a cart 1134 on which various devices for endoscopic surgery are mounted.

The endoscope 1100 is composed of a lens barrel 1101, the tip of which is inserted into the body cavity of the patient 1132 at a predetermined length, and a camera head 1102 connected to the base end of the lens barrel 1101. In the illustrated example, the endoscope 1100 is configured as a so-called rigid lens barrel having a rigid lens barrel 1101, but the endoscope 1100 may also be configured as a so-called flexible lens barrel having a flexible lens barrel.

The endoscope 1100 is provided at its tip with an opening into which an objective lens is fitted. A light source device 1203 is connected to the endoscope 1100, and light generated by the light source device 1203 is guided to the tip of the tube by a light guide extending inside the tube 1101, and is irradiated via the objective lens toward an observation target in the body cavity of the patient 1132. The endoscope 1100 may be a direct-viewing endoscope, an oblique-viewing endoscope, or a side-viewing endoscope.

An optical system and a photoelectric conversion device are provided inside the camera head 1102, and reflected light (observation light) from the observation object is focused on the photoelectric conversion device by the optical system. The observation light is photoelectrically converted by the photoelectric conversion device to generate an electrical signal corresponding to the observation light, i.e., an image signal corresponding to the observation image. The photoelectric conversion device may be any of the photoelectric conversion devices described in the above-mentioned embodiments. The image signal is sent to a camera control unit (CCU: Camera Control Unit) 1135 as RAW data.

The CCU 1135 is configured with a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), etc., and controls the overall operation of the endoscope 1100 and the display device 1136. Furthermore, the CCU 1135 receives an image signal from the camera head 1102, and performs various image processing on the image signal, such as development processing (demosaic processing), to display an image based on the image signal.

The display device 1136, under the control of the CCU 1135, displays an image based on the image signal that has been subjected to image processing by the CCU 1135.

The light source device 1203 is composed of a light source such as an LED (Light Emitting Diode) and supplies the endoscope 1100 with illumination light when photographing the surgical site, etc.

The input device 1137 is an input interface for the endoscopic surgery system 1150. A user can input various information and instructions to the endoscopic surgery system 1150 via the input device 1137.

The treatment tool control device 1138 controls the operation of the energy treatment tool 1112 for cauterizing tissue, incising, sealing blood vessels, etc.

The light source device 1203 that supplies irradiation light to the endoscope 1100 when photographing the surgical site can be composed of a white light source composed of, for example, an LED, a laser light source, or a combination of these. When the white light source is composed of a combination of RGB laser light sources, the output intensity and output timing of each color (each wavelength) can be controlled with high precision, so that the white balance of the captured image can be adjusted in the light source device 1203. In this case, it is also possible to capture images corresponding to each of the RGB colors in a time-division manner by irradiating the observation object with laser light from each of the RGB laser light sources in a time-division manner and controlling the drive of the image sensor of the camera head 1102 in synchronization with the irradiation timing. According to this method, a color image can be obtained without providing a color filter to the image sensor.

The light source device 1203 may be controlled to change the intensity of the light it outputs at predetermined time intervals. The driving of the image sensor of the camera head 1102 may be controlled in synchronization with the timing of the change in the light intensity to acquire images in a time-division manner, and the images may be synthesized to generate an image with a high dynamic range that is free of so-called blackout and whiteout.

The light source device 1203 may also be configured to supply light of a predetermined wavelength band corresponding to special light observation. In special light observation, for example, the wavelength dependency of light absorption in body tissue is utilized. Specifically, a specific tissue such as blood vessels on the mucosal surface is photographed with high contrast by irradiating light of a narrower band than the irradiation light (i.e., white light) during normal observation. Alternatively, in special light observation, fluorescence observation may be performed in which an image is obtained by fluorescence generated by irradiating excitation light. In fluorescence observation, excitation light is irradiated to the body tissue and the fluorescence from the body tissue is observed, or a reagent such as indocyanine green (ICG) is locally injected into the body tissue and excitation light corresponding to the fluorescence wavelength of the reagent is irradiated to the body tissue to obtain a fluorescent image. The light source device 1203 may be configured to supply narrow band light and/or excitation light corresponding to such special light observation.

Ninth embodiment
The photoelectric conversion system of this embodiment will be described with reference to Figs. 19(a) and (b). Fig. 19(a) describes glasses 1600 (smart glasses) which are the photoelectric conversion system of this embodiment. The glasses 1600 have a photoelectric conversion device 1602. The photoelectric conversion device 1602 is the photoelectric conversion device described in each of the above embodiments. In addition, a display device including a light-emitting device such as an OLED or LED may be provided on the back side of the lens 1601. The photoelectric conversion device 1602 may be one or more. In addition, a combination of multiple types of photoelectric conversion devices may be used. The arrangement position of the photoelectric conversion device 1602 is not limited to that shown in Fig. 19(a).

The glasses 1600 further include a control device 1603. The control device 1603 functions as a power source that supplies power to the photoelectric conversion device 1602 and the display device. The control device 1603 also controls the operation of the photoelectric conversion device 1602 and the display device. The lens 1601 is formed with an optical system for focusing light on the photoelectric conversion device 1602.

Figure 19 (b) explains glasses 1610 (smart glasses) according to one application example. The glasses 1610 have a control device 1612, and the control device 1612 is equipped with a photoelectric conversion device corresponding to the photoelectric conversion device 1602 and a display device. The lens 1611 is formed with an optical system for projecting light emitted from the photoelectric conversion device in the control device 1612 and the display device, and an image is projected onto the lens 1611. The control device 1612 functions as a power source that supplies power to the photoelectric conversion device and the display device, and controls the operation of the photoelectric conversion device and the display device. The control device may have a line of sight detection unit that detects the line of sight of the wearer. Infrared light may be used to detect the line of sight. The infrared light emission unit emits infrared light to the eyeball of a user who is gazing at a displayed image. An imaging unit having a light receiving element detects the reflected light of the emitted infrared light from the eyeball, thereby obtaining an image of the eyeball. By having a reduction means for reducing light from the infrared light emission unit to the display unit in a planar view, deterioration of image quality is reduced.

The user's line of sight with respect to the displayed image is detected from an image of the eyeball obtained by capturing infrared light. Any known method can be applied to gaze detection using an image of the eyeball. As an example, a gaze detection method based on the Purkinje image formed by reflection of irradiated light on the cornea can be used.

More specifically, gaze detection processing is performed based on the pupil-corneal reflex method. Using the pupil-corneal reflex method, a gaze vector that represents the direction (rotation angle) of the eyeball is calculated based on the pupil image and Purkinje image contained in the captured image of the eyeball, thereby detecting the user's gaze.

The display device of this embodiment may have a photoelectric conversion device having a light receiving element, and may control the display image of the display device based on user line-of-sight information from the photoelectric conversion device.

Specifically, the display device determines a first field of view area on which the user gazes and a second field of view area other than the first field of view area based on the line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be received from an external control device. In the display area of the display device, the display resolution of the first field of view area may be controlled to be higher than the display resolution of the second field of view area. In other words, the resolution of the second field of view area may be lower than the first field of view area.

The display area may have a first display area and a second display area different from the first display area, and an area having a high priority may be determined from the first display area and the second display area based on line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be received from an external control device. The resolution of the high priority area may be controlled to be higher than the resolution of areas other than the high priority area. In other words, the resolution of an area having a relatively low priority may be lowered.

AI may be used to determine the first field of view area and areas with high priority. The AI may be a model configured to estimate the angle of gaze and the distance to an object in the line of sight from the image of the eyeball, using as teacher data an image of the eyeball and the direction in which the eyeball in the image was actually looking. The AI program may be possessed by the display device, the photoelectric conversion device, or an external device. If possessed by an external device, it is transmitted to the display device via communication.

When display control is based on visual detection, it is preferably applicable to smart glasses that further include a photoelectric conversion device that captures images of the outside world. The smart glasses can display captured external information in real time.

[Modified embodiment]
The present invention is not limited to the above-described embodiment, and various modifications are possible.

For example, the embodiments of the present invention also include examples in which some configuration of one embodiment is added to another embodiment, or examples in which some configuration of another embodiment is replaced with another embodiment.

The photoelectric conversion systems shown in the fourth and fifth embodiments are merely examples of photoelectric conversion systems to which a photoelectric conversion device can be applied, and photoelectric conversion systems to which the photoelectric conversion device of the present invention can be applied are not limited to the configurations shown in Figures 15 and 16. The same applies to the ToF system shown in the sixth embodiment, the endoscope shown in the seventh embodiment, and the smart glasses shown in the eighth embodiment.

The photoelectric conversion device of each of the above-mentioned embodiments can also be applied to sensors inside an automobile. For example, it can be applied to sensors used to detect the driver's face, facial expression, and line of sight. The output of this sensor can be used to detect the driver's lack of attention, drowsiness, fainting, etc. It can also be used to identify the driver.

The above embodiments are merely examples of how the present invention can be implemented, and the technical scope of the present invention should not be interpreted in a limiting manner. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features.

This disclosure also includes the following configuration:

(Configuration 1) A photoelectric conversion device having a pixel region including a plurality of pixels each having an avalanche photodiode including an anode and a cathode, the plurality of pixels including effective pixels that output a photon detection signal in response to detection of a photon, dummy pixels that do not output the photon detection signal, and optical black pixels having a light-shielding portion, the pixel region having a first region including the effective pixels, a second region including the dummy pixels, and a third region including the optical black pixels, the second region having a first portion and a second portion that are in contact with an end of the pixel region, the first portion, the first region, the second portion, and the third region are arranged in this order in a first direction, and in the first direction, the width of the second portion is wider than the width of the first portion.

(Configuration 2) The photoelectric conversion device according to configuration 1, characterized in that the second region has a third portion that contacts an end of the pixel region, the first region and the third portion are aligned along a second direction that intersects with the first direction, and the width of the second portion in the first direction is wider than the width of the third portion in the second direction.

(Configuration 3) The photoelectric conversion device according to configuration 1 or 2, characterized in that the number of dummy pixels arranged along the width of the second portion in the first direction is greater than the number of dummy pixels arranged along the width of the first portion in the first direction.

(Configuration 4) The photoelectric conversion device according to any one of configurations 1 to 3, characterized in that the effective pixels are connected to a counter circuit that counts the photon detection signals, and the dummy pixels are not connected to the counter circuit.

(Configuration 5) The photoelectric conversion device according to configuration 4, wherein the second region includes a test pixel in which a node different from the anode and the cathode is connected to an input node of the counter circuit.

(Configuration 6) A photoelectric conversion device according to any one of configurations 1 to 5, characterized in that each of the plurality of pixels has a pixel separation section between adjacent pixels.

(Configuration 7) The photoelectric conversion device according to configuration 6, characterized in that it has a pixel separation section that separates the first region in which the effective pixels are arranged from the second region in which the dummy pixels are arranged.

(Configuration 8) The photoelectric conversion device according to Configuration 6 or 7, characterized in that it has a pixel separation section that separates the third region in which the effective pixels are arranged from the second region in which the dummy pixels are arranged.

(Configuration 9) A photoelectric conversion device according to any one of configurations 1 to 8, characterized in that it has a fourth region having the optical black pixel, the second region has a fourth portion, the fourth region and the fourth portion are aligned in a third direction intersecting the first direction, and the width of the fourth portion in the third direction is wider than the width of the first portion in the first direction.

(Configuration 10) The photoelectric conversion device described in Configuration 9, characterized in that the number of dummy pixels arranged along the width of the fourth portion in the third direction is greater than the number of dummy pixels arranged along the width of the first portion in the first direction.

(Configuration 11) The photoelectric conversion device described in configuration 2, characterized in that the width of the second portion in the first direction is more than ten times the width of the third portion in the second direction.

(Configuration 12) A photoelectric conversion device according to any one of configurations 1 to 11, characterized in that the number of dummy pixels arranged along the width of the second portion in the first direction is more than ten times the number of dummy pixels arranged along the width of the first portion in the first direction.

(Configuration 13) A photoelectric conversion device according to any one of configurations 1 to 12, characterized in that one of the nodes of the anode and the cathode is connected to a power source to which a drive voltage is applied, and has a switch for switching the resistance value between the one node and the power source.

(Configuration 14) The photoelectric conversion device according to configuration 13, wherein each of the dummy pixels has multiple avalanche photodiodes for one of the switches.

(Configuration 15) A photoelectric conversion device according to any one of configurations 1 to 14, characterized in that the number of avalanche photodiodes in the first dummy pixel among the dummy pixels is greater than the number of avalanche photodiodes in the second dummy pixel.

(Configuration 16) The photoelectric conversion device described in configuration 15, characterized in that the distance from the boundary between the first region and the second region to the first dummy pixel is longer than the distance from the boundary to the second dummy pixel.

(Configuration 17) The photoelectric conversion device according to any one of configurations 13 to 16, characterized in that the switch is a transistor.

(Configuration 18) The photoelectric conversion device according to any one of configurations 1 to 17, wherein the avalanche photodiode of the effective pixel is recharged in a first period.

(Configuration 19) The photoelectric conversion device described in configuration 18, wherein the avalanche photodiode of the dummy pixel is recharged at a second period different from the first period.

(Configuration 20) The photoelectric conversion device described in configuration 19, characterized in that the second period is longer than the first period.

(Configuration 21) A system comprising a photoelectric conversion device according to any one of configurations 1 to 20, and a signal processing unit that processes a signal output from the photoelectric conversion device.

(Configuration 22) A moving body comprising a photoelectric conversion device according to any one of configurations 1 to 20, an information acquisition means for acquiring distance information to an object from a parallax image based on a signal from the photoelectric conversion device, and a control means for controlling the moving body based on the distance information.

100 Photoelectric conversion device 12 Pixel region 10 First region 10b Second region 10c Third region

Claims (22)

a pixel region including a plurality of pixels each having an avalanche photodiode including an anode and a cathode;
the plurality of pixels include effective pixels that output a photon detection signal in response to detection of a photon, dummy pixels that do not output the photon detection signal, and optical black pixels that have a light-shielding portion;
The effective pixels are connected to a counter circuit that counts the photon detection signals,
the dummy pixel is not connected to the counter circuit;
the pixel region includes a first region having the effective pixels, a second region having the dummy pixels, and a third region having the optical black pixels;
the second region has a first portion in contact with an end of the pixel region and a second portion;
the first portion, the first region, the second portion, and the third region are arranged in this order in a first direction,
A photoelectric conversion device, characterized in that, in the first direction, the width of the second portion is wider than the width of the first portion. the second region has a third portion in contact with an edge of the pixel region,
the first region and the third portion are aligned along a second direction intersecting the first direction,
2. The photoelectric conversion device according to claim 1, wherein the width of the second portion in the first direction is greater than the width of the third portion in the second direction. The photoelectric conversion device according to claim 1, characterized in that the number of dummy pixels arranged along the width of the second portion in the first direction is greater than the number of dummy pixels arranged along the width of the first portion in the first direction. 2 . The photoelectric conversion device according to claim 1 , wherein the second region includes a test pixel having a node different from the anode and the cathode connected to an input node of the counter circuit. The photoelectric conversion device according to claim 1, characterized in that each of the plurality of pixels has a pixel separation portion between adjacent pixels. 6. The photoelectric conversion device according to claim 5 , further comprising a pixel separating portion that separates the first region in which the effective pixels are arranged from the second region in which the dummy pixels are arranged. 6. The photoelectric conversion device according to claim 5 , further comprising a pixel separating portion that separates the third region in which the effective pixels are arranged from the second region in which the dummy pixels are arranged. a fourth region having the optical black pixels;
the second region has a fourth portion;
the fourth region and the fourth portion are aligned in a third direction intersecting the first direction,
2 . The photoelectric conversion device according to claim 1 , wherein the width of the fourth portion in the third direction is greater than the width of the first portion in the first direction. The photoelectric conversion device according to claim 8, characterized in that the number of dummy pixels arranged along the width of the fourth portion in the third direction is greater than the number of dummy pixels arranged along the width of the first portion in the first direction. The photoelectric conversion device according to claim 2, characterized in that the width of the second portion in the first direction is more than ten times the width of the third portion in the second direction. The photoelectric conversion device according to claim 1, characterized in that the number of dummy pixels arranged along the width of the second portion in the first direction is more than ten times the number of dummy pixels arranged along the width of the first portion in the first direction. a node of one of the anode and the cathode and a power supply to which a driving voltage is applied;
2. The photoelectric conversion device according to claim 1, further comprising a switch for switching a resistance value between the one node and the power supply. 13. The photoelectric conversion device according to claim 12, wherein the switch is a transistor. a pixel region including a plurality of pixels each having an avalanche photodiode including an anode and a cathode;
the plurality of pixels include effective pixels that output a photon detection signal in response to detection of a photon, dummy pixels that do not output the photon detection signal, and optical black pixels that have a light-shielding portion;
a switch connected to one of the nodes of the anode and the cathode and a power supply to which a drive voltage is applied, for switching a resistance value between the one node and the power supply;
the pixel region includes a first region having the effective pixels, a second region having the dummy pixels, and a third region having the optical black pixels;
the second region has a first portion in contact with an end of the pixel region and a second portion;
the first portion, the first region, the second portion, and the third region are arranged in this order in a first direction,
In the first direction, a width of the second portion is greater than a width of the first portion;
A photoelectric conversion device, wherein each of the dummy pixels has a plurality of avalanche photodiodes for one of the switches. The photoelectric conversion device according to claim 14, characterized in that the number of avalanche photodiodes in the first dummy pixel is greater than the number of avalanche photodiodes in the second dummy pixel. The photoelectric conversion device according to claim 15, characterized in that the distance from the boundary between the first region and the second region to the first dummy pixel is longer than the distance from the boundary to the second dummy pixel. 15. The photoelectric conversion device according to claim 14, wherein the switch is a transistor. The photoelectric conversion device according to claim 1, characterized in that the avalanche photodiode of the effective pixel is recharged in a first period. a pixel region including a plurality of pixels each having an avalanche photodiode including an anode and a cathode;
the plurality of pixels include effective pixels that output a photon detection signal in response to detection of a photon, dummy pixels that do not output the photon detection signal, and optical black pixels that have a light-shielding portion;
the pixel region includes a first region having the effective pixels, a second region having the dummy pixels, and a third region having the optical black pixels;
the second region has a first portion in contact with an end of the pixel region and a second portion;
the first portion, the first region, the second portion, and the third region are arranged in this order in a first direction,
In the first direction, a width of the second portion is greater than a width of the first portion;
The avalanche photodiode of the effective pixel is recharged in a first period;
The avalanche photodiode of the dummy pixel is recharged at a second period different from the first period. The photoelectric conversion device according to claim 19, characterized in that the second period is longer than the first period. The photoelectric conversion device according to claim 1 ;
and a signal processing unit that processes a signal output from the photoelectric conversion device. A mobile object,
The photoelectric conversion device according to claim 1 ;
A moving body comprising: an information acquisition means for acquiring distance information to an object from a parallax image based on a signal from the photoelectric conversion device; and a control means for controlling the moving body based on the distance information.

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