Imaging device and camera system

Abstract

This imaging device comprises: a photoelectric conversion unit, a first voltage supply circuit, a signal detection circuit, at least one current measurement circuit, and a current change detection circuit. The photoelectric conversion unit includes a first electrode, a second electrode which faces the first electrode, and a photoelectric conversion layer which is positioned between the first electrode and the second electrode. The first voltage supply circuit applies a voltage between the first electrode and the second electrode. The signal detection circuit detects a signal based on charges generated in the photoelectric conversion unit. The at least one current measurement circuit measures a current flowing in the photoelectric conversion unit. The current change detection circuit detects a change in current flowing in the photoelectric conversion unit measured by the at least one current measurement circuit.

Description

Imaging device and camera system

[0001] The present disclosure relates to an imaging device and a camera system.

[0002] Conventionally, image sensors using photoelectric conversion have been known. For example, CMOS (Complementary Metal Oxide Semiconductor) image sensors having photodiodes are widely used as image sensors. CMOS image sensors are characterized by low power consumption and the ability to access each pixel individually. CMOS image sensors generally employ a so-called rolling shutter method as a signal readout method, in which exposure and signal charge readout are performed sequentially for each row of the pixel array.

[0003] In the rolling shutter method, the start and end of exposure is different for each row of the pixel array, which can result in distorted images of fast-moving objects and brightness differences within the image when using a flash.

[0004] Under these circumstances, there is a demand for a so-called global shutter function in which the start and end of exposure is common to all pixels in a pixel array.

[0005] For example, Patent Document 1 discloses a method for realizing a global shutter function in an image sensor with a stacked structure in which the circuit section and the photoelectric conversion section are separated, by changing the voltage supplied to the photoelectric conversion section to control the movement of signal charge from the photoelectric conversion section to the charge accumulation region.

[0006] Furthermore, Patent Document 2 proposes an asynchronous solid-state imaging device called an event-driven sensor and a dynamic vision sensor, which detects an event for each pixel when the amount of received light exceeds a threshold value.

[0007] Japanese Patent No. 6799784 Japanese Patent Application Laid-Open No. 2020-57949 Japanese Patent Application Laid-Open No. 2010-232410 Japanese Patent No. 5553727

[0008] It would be useful for an imaging device to be able to detect changes in a subject, such as the movement of an object, in addition to capturing normal images.

[0009] The present disclosure provides an imaging device and a camera system that can detect changes in a subject.

[0010] An imaging device according to one embodiment of the present disclosure includes a photoelectric conversion unit including a first electrode, a second electrode opposite the first electrode, and a photoelectric conversion layer located between the first electrode and the second electrode, a first voltage supply circuit that applies a voltage between the first electrode and the second electrode, a signal detection circuit that detects a signal based on charges generated in the photoelectric conversion unit, at least one current measurement circuit that measures a current flowing in the photoelectric conversion unit, and a current change detection circuit that detects a change in the current flowing in the photoelectric conversion unit measured by the at least one current measurement circuit.

[0011] A camera system according to one aspect of the present disclosure includes the imaging device described above and an illumination device that emits light including near-infrared rays.

[0012] According to the present disclosure, it is possible to provide an imaging device and a camera system that can detect changes in a subject.

[0013] FIG. 1 is a block diagram illustrating an example of a camera system according to an embodiment. FIG. 2 is a schematic diagram illustrating an exemplary circuit configuration of an image sensor according to an embodiment. FIG. 3 is a schematic cross-sectional diagram illustrating an exemplary device structure of a pixel according to an embodiment. FIG. 4 is a plan view illustrating an exemplary planar layout of a pixel electrode and a shield electrode according to an embodiment. FIG. 5 is a diagram illustrating an example of an absorption spectrum in a photoelectric conversion layer including tin phthalocyanine. FIG. 6 is a schematic cross-sectional diagram illustrating an exemplary configuration of a photoelectric conversion layer according to an embodiment. FIG. 7 is a diagram illustrating exemplary photocurrent characteristics of a photoelectric conversion unit according to an embodiment. FIG. 8 is a diagram illustrating an example of an operation of normal imaging drive in an image pickup device according to an embodiment. FIG. 9 is a schematic diagram illustrating the arrangement of a current measurement circuit according to an embodiment. FIG. 10A is a diagram illustrating an example of an operation and output result of current change detection drive in an image pickup device according to an embodiment. FIG. 10B is a diagram illustrating an example of an operation and output result of current change detection drive in an image pickup device according to an embodiment. FIG. 11 is a diagram illustrating a first example of drive mode control in an image pickup device according to an embodiment. 12 and 13 are diagrams illustrating a second and a third example of drive mode control in the imaging device according to the embodiment.

[0014] (Summary of the Present Disclosure) As an overview of the present disclosure, examples of an imaging device and a camera system according to the present disclosure are described below.

[0015] An imaging device according to a first aspect of the present disclosure comprises a photoelectric conversion unit including a first electrode, a second electrode opposite the first electrode, and a photoelectric conversion layer located between the first electrode and the second electrode, a first voltage supply circuit that applies a voltage between the first electrode and the second electrode, a signal detection circuit that detects a signal based on charges generated in the photoelectric conversion unit, at least one current measurement circuit that measures a current flowing in the photoelectric conversion unit, and a current change detection circuit that detects a change in the current flowing in the photoelectric conversion unit measured by the at least one current measurement circuit.

[0016] As a result, when the subject changes within the imaging range of the imaging device, the amount of light incident on the photoelectric conversion unit also changes, causing a change in the current flowing through the photoelectric conversion unit. Therefore, in the imaging device according to this aspect, the current change detection circuit detects a change in the current flowing through the photoelectric conversion unit measured by the current measurement circuit, thereby enabling detection of a change in the subject.

[0017] For example, an imaging device according to a second aspect of the present disclosure may be the imaging device according to the first aspect, further comprising a charge storage unit connected to the first electrode and configured to store the charge generated by the photoelectric conversion unit, the first voltage supply circuit applying the voltage between the first electrode and the second electrode by supplying a predetermined voltage to the second electrode, and the at least one current measurement circuit may include a first current measurement circuit connected to the second electrode.

[0018] This makes it possible to measure the current in the wiring connected to the second electrode to which a predetermined voltage is supplied from the first voltage supply circuit and detect changes in the current, thereby preventing the circuitry of the imaging device from becoming too complicated.

[0019] Also, for example, an imaging device according to a third aspect of the present disclosure may be an imaging device according to the second aspect, wherein the second electrode is divided into a plurality of sub-second electrodes, the at least one current measurement circuit may include a plurality of current measurement circuits, the plurality of current measurement circuits may be a plurality of the first current measurement circuits, and each of the plurality of sub-second electrodes may be connected to a corresponding first current measurement circuit among the plurality of first current measurement circuits.

[0020] This makes it possible to detect changes in the subject by dividing the area imaged by the imaging device.

[0021] For example, an imaging device according to a fourth aspect of the present disclosure may be the imaging device according to any one of the first to third aspects, further including a charge storage unit connected to the first electrode and configured to store the charges generated by the photoelectric conversion unit. The photoelectric conversion unit may further include a third electrode facing the second electrode across the photoelectric conversion layer, and the at least one current measurement circuit may include a second current measurement circuit connected to the third electrode.

[0022] This allows current changes to be detected by measuring the current using wiring connected to a third electrode that is different from the first electrode connected to the charge storage section, thereby reducing the complexity of the circuitry of the imaging device.

[0023] Also, for example, an imaging device according to a fifth aspect of the present disclosure may be an imaging device according to the fourth aspect, wherein the third electrode is divided into a plurality of sub-third electrodes, the at least one current measurement circuit may include a plurality of current measurement circuits, the plurality of current measurement circuits may be a plurality of the second current measurement circuits, and each of the plurality of sub-third electrodes may be connected to a corresponding second current measurement circuit among the plurality of second current measurement circuits.

[0024] This makes it possible to detect changes in the subject by dividing the area imaged by the imaging device.

[0025] For example, an imaging device according to a sixth aspect of the present disclosure may be the imaging device according to any one of the first to fifth aspects, further comprising: a charge accumulation unit connected to the first electrode and configured to accumulate the charges generated by the photoelectric conversion unit; and a second voltage supply circuit configured to supply a predetermined voltage to the charge accumulation unit. The at least one current measurement circuit may include at least one third current measurement circuit connected to the second voltage supply circuit.

[0026] This makes it possible to measure the current in the wiring connected to the second voltage supply circuit that supplies voltage to the charge accumulation unit and detect changes in the current, thereby preventing the circuitry of the imaging device from becoming too complicated.

[0027] Furthermore, for example, an imaging device according to a seventh aspect of the present disclosure may be the imaging device according to the sixth aspect, further including a plurality of pixels, each of which may include the photoelectric conversion unit, the signal detection circuit, and the charge accumulation unit. The at least one third current measurement circuit may include a plurality of the third current measurement circuits. The plurality of pixels may include a first pixel and a second pixel different from the first pixel. Corresponding third current measurement circuits may be located at a portion of a first wiring path connecting the charge accumulation unit included in the first pixel to the second voltage supply circuit that does not overlap with a second wiring path connecting the charge accumulation unit included in the second pixel to the second voltage supply circuit, and at a portion of the second wiring path that does not overlap with the first wiring path.

[0028] This makes it possible to detect changes in the subject by dividing the area imaged by the imaging device.

[0029] Also, for example, an imaging device according to an eighth aspect of the present disclosure may be an imaging device according to any one of the first to seventh aspects, wherein the at least one current measurement circuit includes a plurality of current measurement circuits.

[0030] This makes it possible to detect changes in the subject by dividing the area imaged by the imaging device.

[0031] For example, an imaging device according to a ninth aspect of the present disclosure is the imaging device according to any one of the first to eighth aspects, and may further include a plurality of pixels, each of which may include the photoelectric conversion unit and the signal detection circuit. The number of the at least one current measurement circuit may be less than the number of the pixels.

[0032] This allows for driving with low power consumption.

[0033] Furthermore, for example, an imaging device according to a tenth aspect of the present disclosure may be the imaging device according to any one of the first to ninth aspects, further including a drive control circuit that controls driving of the imaging device. The drive control circuit may control the imaging device to perform (i) a current change detection drive in which the current change detection circuit detects the change in the current flowing in the photoelectric conversion unit, and (ii) a normal imaging drive in which the signal detection circuit detects the signal based on the charge generated in the photoelectric conversion unit.

[0034] This allows the imaging device to detect changes in the subject through current change detection driving, while in normal imaging driving it can detect signals for image generation based on the charges generated in the photoelectric conversion unit and output detailed images.

[0035] Also, for example, an imaging device according to an eleventh aspect of the present disclosure is the imaging device according to the tenth aspect, wherein the drive control circuit may switch the drive of the imaging device from the current change detection drive to the normal imaging drive when the current change detection circuit detects the change in the current flowing in the photoelectric conversion unit while the imaging device is performing the current change detection drive.

[0036] This allows the imaging device to output image data that allows the user or the like to easily recognize the subject when a change in the subject is detected.

[0037] Furthermore, for example, an imaging device according to a twelfth aspect of the present disclosure may be the imaging device according to the eleventh aspect, wherein the drive control circuit switches the drive of the imaging device from the normal imaging drive to the current change detection drive after a predetermined time has elapsed since the imaging device started the normal imaging drive.

[0038] This allows normal imaging to be performed for a predetermined time after a change in the subject is detected, thereby reducing the power consumption of the imaging device.

[0039] Furthermore, for example, an imaging device according to a thirteenth aspect of the present disclosure is an imaging device according to any one of the tenth to twelfth aspects, and the drive control circuit may set the signal detection circuit and at least some of the circuits connected to the signal detection circuit to an off state or a standby state while controlling the imaging device to perform the current change detection drive.

[0040] This makes it possible to reduce the power consumption of the imaging device in current change detection driving.

[0041] Also, for example, an imaging device according to a fourteenth aspect of the present disclosure may be the imaging device according to the tenth aspect, wherein the drive control circuit controls the imaging device to perform the current change detection drive and the normal imaging drive simultaneously.

[0042] This makes it possible to capture normal images while detecting changes in the subject.

[0043] A camera system according to a fifteenth aspect of the present disclosure includes the imaging device according to any one of the first to fourteenth aspects and an illumination device that emits light including near-infrared rays.

[0044] This makes it possible to detect changes in the subject and acquire images even in conditions that are invisible to the human eye, such as in darkness at night.

[0045] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0046] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components not recited in independent claims are described as optional components. Furthermore, the drawings are not necessarily strict illustrations. In the drawings, substantially identical components are denoted by the same reference numerals, and redundant descriptions may be omitted or simplified.

[0047] Furthermore, in this specification, terms indicating the relationship between elements, terms indicating the shape of elements, and numerical ranges are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about a few percent.

[0048] Furthermore, in this specification, the terms "upper" and "lower" do not refer to the upper direction (vertically upper) and lower direction (vertically lower) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in the stacked structure. Specifically, the light-receiving side of the imaging device is referred to as "upper," and the side opposite the light-receiving side is referred to as "lower." Note that terms such as "upper" and "lower" are used solely to specify the relative arrangement of components and are not intended to limit the orientation of the imaging device during use. Furthermore, the terms "upper" and "lower" are used not only when two components are arranged with a gap between them and another component is present between them, but also when two components are arranged closely together and the two components are in contact with each other.

[0049] (Embodiments) An imaging device and a camera system according to embodiments will be described below.

[0050] [Camera System] First, a camera system according to the present embodiment will be described. Fig. 1 is a block diagram showing an example of a camera system 1 according to the present embodiment.

[0051] As shown in FIG. 1, the camera system 1 includes an imaging device 100, an illumination device 200, an image processing unit 300, and a system controller 400.

[0052] In the camera system 1, ambient light and illumination light emitted by the lighting device 200 are reflected by the subject, and the reflected light is converted into an electric charge by the photoelectric conversion unit of the image capturing device 100, and is extracted as an electric signal for capturing an image. When ambient light such as sunlight or external lighting is used for capturing an image, the camera system 1 does not need to include the lighting device 200.

[0053] The imaging device 100 includes an imaging element 110, a current change detection circuit 130, and a drive control circuit 140. The imaging element 110 has a photoelectric conversion unit 13 and outputs a signal based on light incident on the photoelectric conversion unit 13. The imaging element 110 also has a current measurement circuit 19 connected to the photoelectric conversion unit 13. The current measurement circuit 19 measures the current flowing in the photoelectric conversion unit 13. Note that at least some of the circuit elements of the current measurement circuit 19 may be provided outside the imaging element 110.

[0054] The current change detection circuit 130 detects changes in the current measured by the current measurement circuit 19. The current change detection circuit 130 can detect the presence of a moving object, for example, based on the detected changes in current. The drive control circuit 140 controls the operation of the imaging device 100 (mainly the image sensor 110). The current change detection circuit 130 and the drive control circuit 140 are each implemented by one or more microcomputers or processors that incorporate programs for performing processing in the current change detection circuit 130 and the drive control circuit 140. The current change detection circuit 130 and the drive control circuit 140 may also be implemented by separate microcomputers or processors, or by a single microcomputer or processor. The current change detection circuit 130 and the drive control circuit 140 may each include dedicated logic circuits for performing processing in the current change detection circuit 130 and the drive control circuit 140. Details of the imaging device 100 will be described later.

[0055] The illumination device 200 emits light containing, for example, near-infrared light as illumination light. In this case, an electrical signal generated by photoelectric conversion in a photoelectric conversion unit of the imaging device 100, which is sensitive to near-infrared wavelengths, is extracted and an image is captured. The wavelength range of the near-infrared light contained in the illumination light is, for example, 680 nm to 3000 nm. The wavelength range of the near-infrared light contained in the illumination light may be 700 nm to 2000 nm or 700 nm to 1600 nm. Note that the illumination light does not have to contain near-infrared light, and may contain at least one of visible light and ultraviolet light.

[0056] The type of light source used in lighting device 200 is not particularly limited as long as it is a light source that can emit light of a desired wavelength. Examples of light sources used in lighting device 200 include a halogen light source, an LED (Light Emitting Diode) light source, an organic EL (Electro Luminescence) light source, and a laser diode light source. Furthermore, the light source used in lighting device 200 may be a combination of multiple light sources with different emission wavelengths. Furthermore, an inexpensive LED with a peak wavelength of 820 nm or more and 980 nm or less can be used as a light source that emits light including near-infrared rays.

[0057] The image processing unit 300 is a processing circuit that performs various processes on output signals including image data output from the imaging device 100. The image processing unit 300 performs processes such as gamma correction, color interpolation, spatial interpolation, auto white balance, distance measurement calculation, and wavelength information separation. The image processing unit 300 processes the output signal from the imaging device 100 and outputs the processed signal to the outside as an image. The image processing unit 300 is realized by one or more microcomputers or processors that incorporate a program for performing the processing in the image processing unit 300. The image processing unit 300 may include a dedicated logic circuit for performing the processing in the image processing unit 300. A specific example of the image processing unit 300 is an ISP (Image Signal Processor).

[0058] The system controller 400 controls the entire camera system 1. The system controller 400 controls, for example, the timing of image capture by the image capture device 100 and the timing of illumination light irradiation by the illumination device 200. The system controller 400 is realized by one or more microcomputers or processors that incorporate programs for performing processing in the system controller 400. The system controller 400 may include a dedicated logic circuit for performing processing in the system controller 400.

[0059] 1, the imaging device 100, lighting device 200, image processing unit 300, and system controller 400 are shown as separate functional blocks, but two or more of the imaging device 100, lighting device 200, image processing unit 300, and system controller 400 may be integrated by being provided in the same housing, etc. Furthermore, the image processing unit 300 and the system controller 400 may each be realized by individual microcomputers or processors, etc., or may be realized by a single microcomputer or processor, etc.

[0060] Furthermore, at least some of the functions of the image processing unit 300 and the system controller 400 may be possessed by the imaging device 100. For example, at least one of the image processing unit 300 and the system controller 400 may be provided in the imaging device 100. In this case, the current change detection circuit 130, the drive control circuit 140, the image processing unit 300, and the system controller 400 may each be realized by an individual microcomputer or processor, or two or more of these functions may be realized by a single microcomputer or processor.

[0061] [Image Sensor] Next, the image sensor 110 included in the image capturing apparatus 100 according to this embodiment will be described in detail.

[0062] 2 is a schematic diagram showing an exemplary circuit configuration of the image sensor 110 according to this embodiment. Note that the current measurement circuit 19 is not shown in FIG. Here, first, a configuration related to capturing a normal image in the image sensor 110 will be described. Details of the current measurement circuit 19 will be described later.

[0063] As shown in Fig. 2, the image sensor 110 has a pixel array PA including a plurality of pixels 10 arranged two-dimensionally, and peripheral circuits connected to each pixel 10. The peripheral circuits include, for example, a shield voltage supply circuit 18, a voltage supply circuit 32, a reset voltage source 34, a vertical scanning circuit 36, a column signal processing circuit 37, and a horizontal signal readout circuit 38. Fig. 2 schematically shows an example in which the pixels 10 are arranged in a matrix of two rows and two columns. The number and arrangement of the pixels 10 in the image sensor 110 are not limited to the example shown in Fig. 2.

[0064] Each pixel 10 has a photoelectric conversion unit 13 and a signal detection circuit 14. As will be described later with reference to the drawings, the photoelectric conversion unit 13 has a photoelectric conversion layer sandwiched between two opposing electrodes, and receives incident light to generate signal charges. The entire photoelectric conversion unit 13 does not need to be an independent element for each pixel 10, and for example, a portion of the photoelectric conversion unit 13 may span multiple pixels 10.

[0065] The signal detection circuit 14 is a circuit that detects a pixel signal, which is an example of a signal based on the charge generated by the photoelectric conversion unit 13. In the example shown in FIG. 2 , the signal detection circuit 14 includes a signal detection transistor 24 and an address transistor 26. The signal detection transistor 24 and the address transistor 26 are, for example, field effect transistors (FETs). Here, N-channel MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) are used as the signal detection transistor 24 and the address transistor 26. Each transistor, such as the signal detection transistor 24, the address transistor 26, and a reset transistor 28 (described later), has a control terminal, an input terminal, and an output terminal. The control terminal is, for example, a gate. The input terminal is one of a drain and a source, for example, the drain. The output terminal is the other of the drain and the source, for example, the source.

[0066] As shown schematically in FIG. 2 , the control terminal of the signal detection transistor 24 is electrically connected to the photoelectric conversion unit 13. Signal charges generated by the photoelectric conversion unit 13 are accumulated in a charge accumulation region including a charge accumulation node 41 between the gate of the signal detection transistor 24 and the photoelectric conversion unit 13. Here, the signal charges are holes and electrons. The charge accumulation node 41 is also called a "floating diffusion node." The charge accumulation node 41 is an example of a charge accumulation unit. Charges are accumulated in the charge accumulation region including the charge accumulation node 41. Details of the structure of the photoelectric conversion unit 13 will be described later.

[0067] The photoelectric conversion unit 13 of each pixel 10 is further connected to a sensitivity control line 42. In the configuration illustrated in FIG. 2 , the sensitivity control line 42 is connected to a voltage supply circuit 32. The voltage supply circuit 32 is an example of a first voltage supply circuit and is also referred to as a sensitivity control voltage supply circuit. The voltage supply circuit 32 is configured to be able to supply at least two types of voltages. During operation of the image sensor 110, the voltage supply circuit 32 supplies a predetermined voltage to the photoelectric conversion unit 13, specifically, to a counter electrode (described later), via the sensitivity control line 42. The voltage supply circuit 32 is not limited to a specific power supply circuit, and may be a circuit that generates a predetermined voltage or a circuit that converts a voltage supplied from another power source to a predetermined voltage. As will be described in detail later, the voltage supplied from the voltage supply circuit 32 to the photoelectric conversion unit 13 is switched between multiple different voltages, thereby controlling the start and end of accumulation of signal charge from the photoelectric conversion unit 13 to the charge accumulation node 41. In other words, in this embodiment, the electronic shutter operation is performed by switching the voltage supplied from the voltage supply circuit 32 to the photoelectric conversion unit 13. An example of the operation of the image sensor 110 will be described later.

[0068] The photoelectric conversion unit 13 of each pixel 10 is further connected to a shielding line 17. In the configuration illustrated in FIG. 2 , the shielding line 17 is connected to a shielding voltage supply circuit 18. During operation of the image sensor 110, the shielding voltage supply circuit 18 supplies a predetermined voltage to the photoelectric conversion unit 13, specifically, to a shield electrode (described later), via the shielding line 17. The shielding voltage supply circuit 18 may be a circuit configured to supply multiple voltages. The shielding voltage supply circuit 18 is not limited to a specific power supply circuit, and may be a circuit that generates a predetermined voltage or a circuit that converts a voltage supplied from another power source into a predetermined voltage. Note that the image sensor 110 does not necessarily have to include the shielding voltage supply circuit 18, and the shielding voltage supply circuit 18 may be a circuit external to the image sensor 110. The shielding line 17 may also be connected to ground instead of the shielding voltage supply circuit 18.

[0069] Each pixel 10 is connected to a power supply line 40 that supplies a power supply voltage VDD. As shown in Fig. 2, an input terminal of a signal detection transistor 24 is connected to the power supply line 40. The power supply line 40 functions as a source follower power supply, so that the signal detection transistor 24 amplifies and outputs a signal corresponding to the charge generated by the photoelectric conversion unit 13.

[0070] An input terminal of an address transistor 26 is connected to an output terminal of the signal detection transistor 24. The output terminal of the address transistor 26 is connected to one of a plurality of vertical signal lines 47 arranged for each column of the pixel array PA. A control terminal of the address transistor 26 is connected to an address control line 46, and by controlling the potential of the address control line 46, the output of the signal detection transistor 24 can be selectively read out to the corresponding vertical signal line 47.

[0071] 2 , the address control lines 46 are connected to the vertical scanning circuit 36. The vertical scanning circuit 36 ​​is also called a "row scanning circuit." The vertical scanning circuit 36 ​​applies a predetermined voltage to the address control lines 46 to select a plurality of pixels 10 arranged in each row on a row-by-row basis. This reads out the signals from the selected pixels 10 and resets the charge storage nodes 41 of the selected pixels 10 and the pixel electrodes, which will be described later.

[0072] The vertical signal lines 47 are main signal lines that transmit pixel signals from the pixel array PA to peripheral circuits. Column signal processing circuits 37 are connected to the vertical signal lines 47. The column signal processing circuits 37 are also called "row signal accumulation circuits." The column signal processing circuits 37 perform noise suppression signal processing, such as correlated double sampling, and analog-to-digital conversion (AD conversion). As shown in FIG. 2 , a column signal processing circuit 37 is provided corresponding to each column of pixels 10 in the pixel array PA. Horizontal signal readout circuits 38 are connected to these column signal processing circuits 37. The horizontal signal readout circuits 38 are also called "column scanning circuits." The horizontal signal readout circuits 38 sequentially read out signals from the multiple column signal processing circuits 37 to horizontal common signal lines 49.

[0073] 2, the pixel 10 has a reset transistor 28. The reset transistor 28 may be, for example, a field effect transistor, similar to the signal detection transistor 24 and the address transistor 26. Unless otherwise specified, the following describes an example in which an N-channel MOSFET is used as the reset transistor 28.

[0074] 2 , the reset transistor 28 is connected between a reset voltage line 44 that supplies a reset voltage Vr and the charge storage node 41. A control terminal of the reset transistor 28 is connected to a reset control line 48, and the potential of the charge storage node 41 can be reset to the reset voltage Vr by controlling the potential of the reset control line 48. In this example, the reset control line 48 is connected to the vertical scanning circuit 36. Therefore, by the vertical scanning circuit 36 ​​applying a predetermined voltage to the reset control line 48, it is possible to reset the multiple pixels 10 arranged in each row on a row-by-row basis.

[0075] In this example, a reset voltage line 44 that supplies a reset voltage Vr to the reset transistor 28 is connected to the reset voltage source 34. The reset voltage source 34 is an example of a second voltage supply circuit and is also referred to as a "reset voltage supply circuit." The reset voltage source 34 is not limited to a specific power supply circuit as long as it has a configuration that allows it to supply a predetermined reset voltage Vr to the reset voltage line 44 when the image sensor 110 is in operation. Similar to the voltage supply circuit 32 and the shield voltage supply circuit 18 described above, the reset voltage source 34 is not limited to a specific power supply circuit. Each of the voltage supply circuit 32, the shield voltage supply circuit 18, and the reset voltage source 34 may be part of a single voltage supply circuit or may be an independent, separate voltage supply circuit. At least one of the voltage supply circuit 32, the shield voltage supply circuit 18, and the reset voltage source 34 may be part of the vertical scanning circuit 36. Alternatively, at least one of the sensitivity control voltage from the voltage supply circuit 32, the shield voltage from the shield voltage supply circuit 18, and the reset voltage Vr from the reset voltage source 34 may be supplied to each pixel 10 via the vertical scanning circuit 36.

[0076] It is also possible to use the power supply voltage VDD of the signal detection circuit 14 as the reset voltage Vr. In this case, the voltage supply circuit (not shown in FIG. 2 ) that supplies the power supply voltage to each pixel 10 and the reset voltage source 34 can be shared. Furthermore, since the power supply line 40 and the reset voltage line 44 can be shared, the wiring in the pixel array PA can be simplified. However, using different voltages for the reset voltage Vr and the power supply voltage VDD of the signal detection circuit 14 allows for more flexible control of the image sensor 110.

[0077] [Device Structure of Pixel] Next, the cross-sectional structure of the pixel 10 of the image sensor 110 according to this embodiment will be described.

[0078] 3 is a cross-sectional view schematically illustrating an exemplary device structure of a pixel 10 according to the present embodiment. In the configuration illustrated in FIG. 3, the signal detection transistor 24, address transistor 26, and reset transistor 28 described above are formed on a semiconductor substrate 20. The semiconductor substrate 20 is not limited to a substrate made entirely of semiconductor. The semiconductor substrate 20 may be an insulating substrate having a semiconductor layer provided on the surface on which the photosensitive region is formed. Here, an example will be described in which a P-type silicon (Si) substrate is used as the semiconductor substrate 20.

[0079] The semiconductor substrate 20 has impurity regions 26s, 24s, 24d, 28d, and 28s, and an element isolation region 20t for electrical isolation between the pixels 10. Here, the impurity regions 26s, 24s, 24d, 28d, and 28s are N-type regions. The element isolation region 20t is also provided between the impurity region 24d and the impurity region 28d. The element isolation region 20t is formed, for example, by implanting acceptor ions under predetermined implantation conditions.

[0080] The impurity regions 26s, 24s, 24d, 28d, and 28s are, for example, diffusion layers formed in the semiconductor substrate 20. As schematically shown in FIG. 3, the signal detection transistor 24 includes impurity regions 24s and 24d and a gate electrode 24g. The impurity region 24s functions as, for example, a source region of the signal detection transistor 24. The impurity region 24d functions as, for example, a drain region of the signal detection transistor 24. A channel region of the signal detection transistor 24 is formed between the impurity region 24s and the impurity region 24d.

[0081] Similarly, the address transistor 26 includes impurity regions 26s and 24s and a gate electrode 26g connected to an address control line 46 (see FIG. 2). In this example, the signal detection transistor 24 and the address transistor 26 are electrically connected to each other by sharing the impurity region 24s. The impurity region 26s functions as, for example, the source region of the address transistor 26. The impurity region 26s is connected to a vertical signal line 47 (see FIG. 2), not shown in FIG. 3.

[0082] The reset transistor 28 includes impurity regions 28d and 28s and a gate electrode 28g connected to a reset control line 48 (see FIG. 2). The impurity region 28s functions as, for example, a source region of the reset transistor 28. The impurity region 28s is connected to a reset voltage line 44 (see FIG. 2), not shown in FIG. 3. The impurity region 28d functions as, for example, a drain region of the reset transistor 28.

[0083] The gate electrodes 24g, 26g, and 28g are each formed using a conductive material, such as polysilicon that has been doped with impurities to make it conductive, but may also be a metal material.

[0084] An interlayer insulating layer 50 is disposed on the semiconductor substrate 20 so as to cover the signal detection transistor 24, the address transistor 26, and the reset transistor 28. The interlayer insulating layer 50 is formed of an insulating material such as silicon oxide. As shown in FIG. 3 , a wiring layer 56 may be disposed in the interlayer insulating layer 50. The wiring layer 56 is formed of a metal such as copper. The wiring layer 56 may include, for example, wiring such as the vertical signal line 47 described above. The number of insulating layers in the interlayer insulating layer 50 and the number of layers included in the wiring layer 56 disposed in the interlayer insulating layer 50 can be set arbitrarily and are not limited to the example shown in FIG. 3 .

[0085] The above-described photoelectric conversion unit 13 is disposed on the interlayer insulating layer 50. In other words, in this embodiment, a plurality of pixels 10 constituting a pixel array PA (see FIG. 2) are formed on a semiconductor substrate 20. The plurality of pixels 10 arranged two-dimensionally on the semiconductor substrate 20 form a pixel region, which is a photosensitive region. The distance between two adjacent pixels 10 can be, for example, about 2 μm. The distance between two adjacent pixels 10 is also called the "pixel pitch."

[0086] The photoelectric conversion unit 13 includes a pixel electrode 11, a counter electrode 12, and a photoelectric conversion layer 15 disposed therebetween. In this embodiment, the photoelectric conversion unit 13 further includes a shield electrode 16. The pixel electrode 11 is an example of a first electrode, the counter electrode 12 is an example of a second electrode, and the shield electrode 16 is an example of a third electrode. In this example, the counter electrode 12, the photoelectric conversion layer 15, and the shield electrode 16 are formed across multiple pixels 10. On the other hand, the pixel electrode 11 is provided for each pixel 10, and is spatially separated from the pixel electrodes 11 of adjacent pixels 10, thereby electrically separating them from the pixel electrodes 11 of the other pixels 10.

[0087] The counter electrode 12 is disposed opposite the pixel electrode 11 with the photoelectric conversion layer 15 interposed therebetween. The counter electrode 12 is, for example, a transparent electrode formed from a transparent conductive material. The counter electrode 12 is disposed on the light-incident side of the photoelectric conversion layer 15. Therefore, light transmitted through the counter electrode 12 is incident on the photoelectric conversion layer 15. Note that the light detected by the imaging element 110 is not limited to light within the wavelength range of visible light (e.g., 380 nm to 780 nm). In this specification, "transparent" means transmitting at least a portion of the light within the wavelength range to be detected, but does not necessarily mean transmitting light across the entire wavelength range of visible light. For convenience, the term "light" is used in this specification to refer to electromagnetic waves in general, including infrared and ultraviolet light. The counter electrode 12 may be formed of, for example, ITO, IZO, AZO, FTO, SnO, etc. ２ , TiO ２ , ZnO ２ Transparent conducting oxides (TCOs) such as the above can be used.

[0088] The photoelectric conversion layer 15 receives incident light and generates hole-electron pairs, which are pairs of electric charges. The photoelectric conversion layer 15 is made of, for example, an organic material. Specific examples of materials that constitute the photoelectric conversion layer 15 will be described later.

[0089] As described with reference to FIG. 2 , the counter electrode 12 is connected to a sensitivity control line 42 connected to the voltage supply circuit 32. Here, the counter electrode 12 is formed across multiple pixels 10. Therefore, a sensitivity control voltage of a desired magnitude can be applied collectively from the voltage supply circuit 32 to multiple pixels 10 via the sensitivity control line 42. Note that, as long as a sensitivity control voltage of a desired magnitude can be applied from the voltage supply circuit 32, the counter electrode 12 may be provided separately for each pixel 10, or separately for each pixel block consisting of two or more pixels 10, which is a portion of the multiple pixels 10. In other words, the counter electrode 12 may be divided into multiple parts. In the example shown in FIG. 2 , the sensitivity control line 42 connected to the counter electrode 12 is connected to a single voltage supply circuit 32, but this is not limiting. If the counter electrode 12 is divided into multiple parts, each of the multiple parts of the counter electrode 12 may be connected to a corresponding one of the multiple voltage supply circuits 32 via the sensitivity control line 42.

[0090] Similarly, the photoelectric conversion layer 15 may be provided separately for each pixel 10, or may be provided separately for each pixel block consisting of two or more pixels 10, which is a portion of the plurality of pixels 10. In other words, the photoelectric conversion layer 15 may be divided into a plurality of layers.

[0091] The voltage supply circuit 32 applies a voltage between the pixel electrode 11 and the counter electrode 12 by supplying a voltage to the counter electrode 12. As will be described in detail later, the voltage supply circuit 32 supplies different voltages to the counter electrode 12 between an exposure period and a non-exposure period, for example. In this specification, the term "exposure period" refers to a period for accumulating signal charges, which are either positive or negative charges generated by photoelectric conversion, in a charge accumulation region, and may also be referred to as a "charge accumulation period."

[0092] In this specification, a period other than an exposure period during operation of the imaging device is referred to as a "non-exposure period." Note that the "non-exposure period" is not limited to a period during which light is blocked from entering the photoelectric conversion unit 13, but may also include a period during which light is irradiated onto the photoelectric conversion unit 13. The "non-exposure period" also includes a period during which signal charge is unintentionally accumulated in the charge accumulation region due to the occurrence of parasitic sensitivity.

[0093] By controlling the potential of the counter electrode 12 relative to the potential of the pixel electrode 11, i.e., the voltage applied between the pixel electrode 11 and the counter electrode 12, the pixel electrode 11 can collect either the holes or the electrons of the hole-electron pairs generated in the photoelectric conversion layer 15 by photoelectric conversion. The voltage applied between the pixel electrode 11 and the counter electrode 12 is also referred to as the "bias voltage." The signal charge collected by the pixel electrode 11 is accumulated in a charge accumulation region. For example, when holes are used as signal charges, the pixel electrode 11 can selectively collect the holes by setting the potential of the counter electrode 12 higher than that of the pixel electrode 11. Furthermore, when electrons are used as signal charges, the pixel electrode 11 can selectively collect the electrons by setting the potential of the counter electrode 12 lower than that of the pixel electrode 11. The following describes an example in which holes are used as signal charges. Of course, electrons can also be used as signal charges.

[0094] The counter electrode 12 is connected to the sensitivity control line 42 in the peripheral region of the pixel array PA, for example, and is supplied with a voltage from the voltage supply circuit 32. Note that the counter electrode 12 may be supplied with a voltage from the voltage supply circuit 32 through a via contact that penetrates the photoelectric conversion layer 15 and a wiring layer 56.

[0095] The pixel electrode 11 facing the counter electrode 12 collects one of the positive and negative charges generated by photoelectric conversion in the photoelectric conversion layer 15 by applying an appropriate bias voltage between the counter electrode 12 and the pixel electrode 11 as described above. The pixel electrode 11 is formed from, for example, a metal such as aluminum or copper, a metal nitride, or polysilicon that has been doped with impurities to make it conductive.

[0096] The pixel electrode 11 may be a light-shielding electrode. For example, forming the pixel electrode 11 as a TaN electrode with a thickness of 100 nm can achieve sufficient light-shielding properties. By using the pixel electrode 11 as a light-shielding electrode, it is possible to suppress the incidence of light passing through the photoelectric conversion layer 15 into the channel regions or impurity regions of at least one of the transistors formed on the semiconductor substrate 20, in this example, the signal detection transistor 24, the address transistor 26, and the reset transistor 28. A light-shielding film may be formed in the interlayer insulating layer 50 using the above-mentioned wiring layer 56. By suppressing the incidence of light into the channel regions of the transistors formed on the semiconductor substrate 20, it is possible to suppress shifts in transistor characteristics, such as fluctuations in threshold voltage. Furthermore, by suppressing the incidence of light into the impurity regions formed on the semiconductor substrate 20, it is possible to suppress the introduction of noise due to unintended photoelectric conversion in the impurity regions. In this way, suppressing the incidence of light into the semiconductor substrate 20 contributes to improving the reliability of the image sensor 110.

[0097] As schematically shown in FIG. 3 , the pixel electrode 11 is connected to the gate electrode 24g of the signal detection transistor 24 via a plug 52, a wiring 53, and a contact plug 54. In other words, the gate of the signal detection transistor 24 is electrically connected to the pixel electrode 11. The plug 52 and the wiring 53 are formed of a metal such as copper. The plug 52, the wiring 53, and the contact plug 54 constitute at least a part of the charge storage node 41 (see FIG. 2 ) between the signal detection transistor 24 and the photoelectric conversion unit 13. The wiring 53 may be part of a wiring layer 56. The pixel electrode 11 is also connected to the impurity region 28d via the plug 52, the wiring 53, and a contact plug 55. In the configuration illustrated in FIG. 2 , the gate electrode 24g of the signal detection transistor 24, the plug 52, the wiring 53, the contact plugs 54 and 55, and the impurity region 28d, which is one of the source and drain regions of the reset transistor 28, function as a charge storage region that stores signal charges collected by the pixel electrode 11.

[0098] As the signal charge is collected by the pixel electrode 11, a voltage corresponding to the amount of signal charge accumulated in the charge accumulation region is applied to the gate of the signal detection transistor 24. The voltage applied to the gate of the signal detection transistor 24 corresponds to the potential of the charge accumulation node 41. The signal detection transistor 24 amplifies this voltage. The voltage amplified by the signal detection transistor 24 is selectively read out as a signal voltage via the address transistor 26.

[0099] The shield electrode 16 is disposed opposite the counter electrode 12 with the photoelectric conversion layer 15 interposed therebetween. Although not shown in FIG. 3 , as described above, the shield electrode 16 is connected to the shield wire 17, and a voltage is applied from the shield voltage supply circuit 18 via the shield wire 17. A portion of the shield wire 17 may be included in the wiring layer 56. Although not shown in FIG. 3 , the shield electrode 16 may be connected to the wiring layer 56 via a contact or the like.

[0100] The shield electrode 16 and the pixel electrode 11 are disposed, for example, at the same level in the interlayer insulating layer 50 and are separated from each other via a portion of the interlayer insulating layer 50. Fig. 4 is a plan view showing an example of the planar layout of the pixel electrode 11 and the shield electrode 16. Note that Fig. 4 omits illustrations of components other than the pixel electrode 11 and the shield electrode 16. For ease of viewing, Fig. 4 uses the same hatching for the pixel electrode 11 and the shield electrode 16 as the hatching for the pixel electrode 11 and the shield electrode 16 shown in the cross section of Fig. 3 .

[0101] 4, the pixel electrodes 11 are arranged, for example, in an array. The shield electrode 16 is disposed between adjacent pixel electrodes 11 in a plan view. In the illustrated example, the shield electrode 16 surrounds the pixel electrodes 11 in a plan view. Specifically, the shield electrodes 16 are disposed in a grid pattern in a plan view, with a pixel electrode 11 disposed within each grid. As described above, the shield electrode 16 is formed, for example, collectively across a plurality of pixels 10, and all the pixels 10 have the same potential.

[0102] The shield electrode 16 may be provided separately for each pixel 10, or for each pixel block consisting of two or more pixels 10, which is a portion of the plurality of pixels 10. That is, the shield electrode 16 may be divided into multiple parts. In the example shown in FIG. 2 , the shield wire 17 connected to the shield electrode 16 is connected to one shield voltage supply circuit 18, but this is not limiting. When the shield electrode 16 is divided into multiple parts, each of the multiple parts of the shield electrode 16 may be connected to a corresponding one of the multiple shield voltage supply circuits 18 via the shield wire 17.

[0103] The voltage applied to the shield electrode 16 can be used to suppress the movement of signal charges between pixels 10, or so-called crosstalk. Therefore, color mixing can be suppressed even if the photoelectric conversion layer 15 is not physically separated. The voltage applied to the shield electrode 16 is set, for example, so that the potential of the shield electrode 16 is higher than the potential of the pixel electrodes 11. For example, a voltage higher than the reset voltage Vr is applied to the shield electrode 16. This facilitates the movement of holes to the pixel electrodes 11 surrounded by the shield electrode 16 in a planar view, thereby suppressing the movement of holes beyond the shield electrode 16 to the pixel electrodes 11 of adjacent pixels 10. Furthermore, the voltage applied to the shield electrode 16 may be set so that the potential of the shield electrode 16 is lower than the potential of the pixel electrodes 11. For example, a voltage lower than the reset voltage Vr is applied to the shield electrode 16. As a result, when viewed in a plane, holes that attempt to move beyond the shield electrode 16 to the pixel electrode 11 of an adjacent pixel 10 are captured by the shield electrode 16, thereby preventing holes from moving beyond the shield electrode 16 to the pixel electrode 11 of an adjacent pixel 10.

[0104] The shield electrode 16 is formed of, for example, a metal such as aluminum or copper, a metal nitride, or polysilicon doped with impurities to provide conductivity. The shield electrode 16 may be a light-shielding electrode. The shield electrode 16 may also be formed of the same material as the pixel electrode 11. The shield electrode 16 and the pixel electrode 11 may also be formed simultaneously in the same process.

[0105] At least one of the peripheral circuits of the image sensor 110 , the current change detection circuit 130 , and the drive control circuit 140 may be formed on the same semiconductor substrate 20 as the image sensor 110 .

[0106] [Example of the Configuration of the Photoelectric Conversion Layer] Next, the photoelectric conversion layer 15 will be described in detail.

[0107] As described above, by irradiating the photoelectric conversion layer 15 with light and applying a bias voltage between the pixel electrode 11 and the counter electrode 12, one of the positive and negative charges generated by photoelectric conversion can be collected by the pixel electrode 11 and stored in the charge accumulation region. By using a photoelectric conversion unit 13 having a photoelectric conversion layer 15 exhibiting the photocurrent characteristics described below and reducing the potential difference between the pixel electrode 11 and the counter electrode 12 to a certain extent, it is possible to prevent signal charges already accumulated in the charge accumulation region from migrating to the counter electrode 12 via the photoelectric conversion layer 15. Furthermore, it is possible to prevent further accumulation of signal charges in the charge accumulation region after reducing the potential difference. In other words, by controlling the magnitude of the bias voltage applied to the photoelectric conversion unit 13, a global shutter function can be realized without providing separate elements such as transfer transistors for each of the multiple pixels 10, as in the technology described in Patent Document 1. An example of the operation of the imaging device 100 will be described later. Of course, normal rolling shutter driving is also possible by keeping the magnitude of the bias voltage applied to the photoelectric conversion unit 13 constant and setting the completion of resetting the pixel 10 as the start of the exposure period.

[0108] An example of the configuration of the photoelectric conversion layer 15 will be described below.

[0109] The photoelectric conversion layer 15 includes, for example, a semiconductor material. In this embodiment, the semiconductor material is, for example, an organic semiconductor material.

[0110] The photoelectric conversion layer 15 contains, for example, tin phthalocyanine represented by the following general formula (1): Hereinafter, the tin phthalocyanine represented by the following general formula (1) may be simply referred to as "tin phthalocyanine".

[0111]

[0112] In general formula (1), R １ From R ２４ are independently a hydrogen atom or a substituent. The substituent is not limited to a specific substituent. Examples of the substituent include a deuterium atom, a halogen atom, an alkyl group (including a cycloalkyl group, a bicycloalkyl group, and a tricycloalkyl group), an alkenyl group (including a cycloalkenyl group and a bicycloalkenyl group), an alkynyl group, an aryl group, a heterocyclic group (which may also be called a heterocyclic group), a cyano group, a hydroxy group, a nitro group, a carboxy group, an alkoxy group, an aryloxy group, a silyloxy group, a heterocyclic oxy group, an acyloxy group, a carbamoyloxy group, an alkoxycarbonyloxy group, an aryloxycarbonyloxy group, an amino group (including an anilino group), an ammonio group, an acylamino group, an aminocarbonylamino group, an alkoxycarbonylamino group, an alkoxycarbonylamino group, an aryloxycarbonyloxy group, an amino group (including an anilino group), an aryloxycarbonylamino group, ... amino group, aryloxycarbonylamino group, sulfamoylamino group, alkylsulfonylamino group, arylsulfonylamino group, mercapto group, alkylthio group, arylthio group, heterocyclic thio group, sulfamoyl group, sulfo group, alkylsulfinyl group, arylsulfinyl group, alkylsulfonyl group, arylsulfonyl group, acyl group, aryloxycarbonyl group, alkoxycarbonyl group, carbamoyl group, arylazo group, heterocyclic azo group, imido group, phosphino group, phosphinyl group, phosphinyloxy group, phosphinylamino group, phosphono group, silyl group, hydrazino group, ureido group, boronic acid group (-B(OH) ２ ), phosphato group (—OPO(OH) ２ ), sulfato group (—OSO ３ H), or other known substituents.

[0113] As the tin phthalocyanine represented by the above general formula (1), commercially available products can be used. Alternatively, the tin phthalocyanine represented by the above general formula (1) can be synthesized using a naphthalene derivative represented by the following general formula (2) as a starting material, as shown in, for example, Patent Document 3. R in general formula (2) ２５ From R ３０ represents R in general formula (1). １ From R ２４ The substituents may be the same as those shown in the above.

[0114]

[0115] In the tin phthalocyanine represented by the above general formula (1), from the viewpoint of ease of control of the aggregation state of the molecules, R １ From R ２４ eight or more of the atoms may be hydrogen atoms or deuterium atoms, and R １ From R ２４ Among these, 16 or more may be hydrogen atoms or deuterium atoms, or all may be hydrogen atoms or deuterium atoms. Furthermore, tin phthalocyanine represented by the following formula (3) is advantageous in terms of ease of synthesis.

[0116]

[0117] The tin phthalocyanine represented by the general formula (1) has absorption in the wavelength range of approximately 200 nm to 1100 nm. For example, the tin phthalocyanine represented by the formula (3) has an absorption peak at a wavelength of approximately 870 nm, as shown in FIG. 5. FIG. 5 is a diagram showing an example of the absorption spectrum of a photoelectric conversion layer containing the tin phthalocyanine represented by the formula (3). Note that the absorption spectrum was measured using a sample in which a photoelectric conversion layer having a thickness of 30 nm was laminated on a quartz substrate.

[0118] As can be seen from Figure 5, a photoelectric conversion layer formed from a material containing tin naphthalocyanine has absorption in the visible light wavelength region and the near-infrared wavelength region. By selecting a material containing tin naphthalocyanine as the material constituting the photoelectric conversion layer 15, for example, an optical sensor capable of detecting near-infrared light can be realized. Also, instead of tin naphthalocyanine, a naphthalocyanine derivative in which the central metal is not tin but another metal such as silicon or germanium may be used. Furthermore, an axial ligand may be coordinated to the central metal of the naphthalocyanine derivative.

[0119] Fig. 6 is a cross-sectional view schematically showing an example of the configuration of the photoelectric conversion layer 15. In the configuration shown in Fig. 6, the photoelectric conversion layer 15 has a hole blocking layer 15h, a photoelectric conversion structure 15A, and an electron blocking layer 15e. The hole blocking layer 15h is disposed between the photoelectric conversion structure 15A and the counter electrode 12, and the electron blocking layer 15e is disposed between the photoelectric conversion structure 15A and the pixel electrode 11. Note that the photoelectric conversion layer 15 does not necessarily have to have at least one of the hole blocking layer 15h and the electron blocking layer 15e.

[0120] The photoelectric conversion structure 15A shown in FIG. 6 includes, for example, at least one of a p-type semiconductor and an n-type semiconductor. In the configuration illustrated in FIG. 6, the photoelectric conversion structure 15A includes a p-type semiconductor layer 150p, an n-type semiconductor layer 150n, and a mixed layer 150m sandwiched between the p-type semiconductor layer 150p and the n-type semiconductor layer 150n. The p-type semiconductor layer 150p is disposed between the electron blocking layer 15e and the mixed layer 150m and has the function of photoelectric conversion and / or hole transport. The n-type semiconductor layer 150n is disposed between the hole blocking layer 15h and the mixed layer 150m and has the function of photoelectric conversion and / or electron transport. As described below, the mixed layer 150m may include at least one of a p-type semiconductor and an n-type semiconductor.

[0121] The p-type semiconductor layer 150p includes an organic p-type semiconductor, and the n-type semiconductor layer 150n includes an organic n-type semiconductor. That is, the photoelectric conversion structure 15A includes an organic photoelectric conversion material containing tin phthalocyanine represented by the above-mentioned general formula (1), an organic p-type semiconductor, and an organic n-type semiconductor.

[0122] An organic p-type semiconductor is a donor organic semiconductor, and is mainly represented by a hole-transporting organic compound, and refers to an organic compound that has the property of easily donating electrons. More specifically, an organic p-type semiconductor is a donor organic compound, and refers to the organic compound that has a smaller ionization potential when two organic materials are used in contact. Therefore, any organic compound that has electron-donating properties can be used as the donor organic compound. For example, donor organic compounds include triarylamine compounds, benzidine compounds, pyrazoline compounds, styrylamine compounds, hydrazone compounds, triphenylmethane compounds, carbazole compounds, polysilane compounds, thiophene compounds, phthalocyanine compounds, naphthalocyanine compounds, subphthalocyanine compounds, cyanine compounds, merocyanine compounds, oxonol compounds, polyamine compounds, indole compounds, pyrrole compounds, pyrazole compounds, polyarylene compounds, fused aromatic carbocyclic compounds (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives), and metal complexes having nitrogen-containing heterocyclic compounds as ligands. The donor organic semiconductor is not limited to these, and any organic compound with a smaller ionization potential than the organic compound used as the acceptor organic semiconductor described below can be used as the donor organic semiconductor. The above-mentioned tin naphthalocyanine is an example of an organic p-type semiconductor material.

[0123] An organic n-type semiconductor is an acceptor organic semiconductor, and is mainly represented by an electron-transporting organic compound, and refers to an organic compound that has a tendency to accept electrons. More specifically, an organic n-type semiconductor is an acceptor organic compound, and refers to the organic compound that has a larger electron affinity when two organic compounds are used in contact with each other. Therefore, any organic compound that has electron-accepting properties can be used as the acceptor organic compound. For example, examples of the acceptor organic compound include fullerene, fullerene derivatives, condensed aromatic carbon ring compounds (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, and fluoranthene derivatives), 5- to 7-membered heterocyclic compounds containing nitrogen atoms, oxygen atoms, and sulfur atoms (e.g., pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxaline, quinazoline, phthalazine, cinnoline, isoquinoline, pteridine, acridine, phenazine, phenanthroline, tetrazole, and pyrazoline). Examples of compounds that can be used include metal complexes having a ligand such as tetraazoindene, imidazole, thiazole, oxazole, indazole, benzimidazole, benzotriazole, benzoxazole, benzothiazole, carbazole, purine, triazolopyridazine, triazolopyrimidine, tetrazaindene, oxadiazole, imidazopyridine, pyrrolidine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine, tribenzazepine, etc.), polyarylene compounds, fluorene compounds, cyclopentadiene compounds, silyl compounds, and nitrogen-containing heterocyclic compounds. The acceptor organic semiconductor is not limited to these compounds, and any organic compound having a larger electron affinity than the organic compound used as the donor organic compound can be used as the acceptor organic semiconductor, as described above.

[0124] The mixed layer 150m may be, for example, a bulk heterojunction structure layer including a p-type semiconductor and an n-type semiconductor. When the mixed layer 150m is formed as a layer having a bulk heterojunction structure, tin phthalocyanine represented by the above-described general formula (1) may be used as the p-type semiconductor material. For example, fullerene and / or a fullerene derivative may be used as the n-type semiconductor material.

[0125] From the viewpoint of improving photoelectric conversion efficiency, the material constituting the p-type semiconductor layer 150p may be the same as the p-type semiconductor material contained in the mixed layer 150m. Similarly, the material constituting the n-type semiconductor layer 150n may be the same as the n-type semiconductor material contained in the mixed layer 150m. The bulk heterojunction structure is described in detail in Patent Document 4 (Japanese Patent No. 5,553,727). The entire disclosure of Japanese Patent No. 5,553,727 is incorporated herein by reference.

[0126] By using an appropriate material depending on the wavelength range to be detected, an imaging element 110 having sensitivity in a desired wavelength range can be realized. The photoelectric conversion layer 15 may contain an inorganic semiconductor material such as amorphous silicon or a compound semiconductor. The photoelectric conversion layer 15 may include a layer composed of an organic material and a layer composed of an inorganic material. Below, an example will be described in which a bulk heterojunction structure obtained by co-evaporating tin phthalocyanine and fullerene C60 is applied to the photoelectric conversion layer 15.

[0127] Although the photoelectric conversion layer 15 sensitive to near-infrared light using tin phthalocyanine has been described above, the material contained in the photoelectric conversion layer 15 is not limited to photoelectric conversion materials sensitive to near-infrared light. For example, the photoelectric conversion layer 15 can be made sensitive to visible light by using subphthalocyanine as a p-type semiconductor and fullerene and / or a fullerene derivative as an n-type semiconductor.

[0128] [Photocurrent Characteristics of Photoelectric Conversion Section] Next, the photocurrent characteristics of the photoelectric conversion section 13 will be described.

[0129] Fig. 7 is a diagram showing exemplary photocurrent characteristics of the photoelectric conversion unit 13. In Fig. 7, the solid line graph shows exemplary current-voltage characteristics (IV characteristics) of the photoelectric conversion unit 13 in a state where light is irradiated, i.e., in the bright state. Note that Fig. 7 also shows, by a dashed line, an example of the IV characteristics of the photoelectric conversion unit 13 in a state where light is not irradiated, i.e., in the dark.

[0130] FIG. 7 shows the change in current density between the major surfaces of the photoelectric conversion layer 15 when the bias voltage applied between the pixel electrode 11 and the counter electrode 12 of the photoelectric conversion unit 13 is changed under a constant illuminance. In this specification, the forward and reverse directions of the bias voltage are defined as follows: When the photoelectric conversion layer 15 has a junction structure of layered p-type semiconductors and layered n-type semiconductors, a bias voltage that causes the potential of the p-type semiconductor layer to be higher than that of the n-type semiconductor layer is defined as a forward bias voltage. On the other hand, a bias voltage that causes the potential of the p-type semiconductor layer to be lower than that of the n-type semiconductor layer is defined as a reverse bias voltage. When the photoelectric conversion layer 15 has a bulk heterojunction structure, as schematically shown in FIG. 1 of the aforementioned Japanese Patent Publication No. 5,553,727, one of the two major surfaces of the bulk heterojunction structure facing the electrodes contains more p-type semiconductor than n-type semiconductor, and the other surface contains more n-type semiconductor than p-type semiconductor. Therefore, a bias voltage that makes the potential of the main surface side where more p-type semiconductors than n-type semiconductors appear higher than the potential of the main surface side where more n-type semiconductors appear than p-type semiconductors is defined as a forward bias voltage. In this embodiment, for example, a voltage that makes the potential of the counter electrode 12 higher than the potential of the pixel electrode 11 is a reverse bias voltage, and a voltage that makes the potential of the counter electrode 12 lower than the potential of the pixel electrode 11 is a forward bias voltage.

[0131] As shown in FIG. 7 , the photocurrent characteristics of the photoelectric conversion unit 13 are roughly characterized by three voltage ranges, from the first voltage range to the third voltage range. The first voltage range is a reverse bias voltage range in which the absolute value of the output current density increases as the reverse bias voltage increases. The first voltage range can also be said to be a voltage range in which the photocurrent increases as the bias voltage applied between the pixel electrode 11 and the counter electrode 12 increases. The second voltage range is a forward bias voltage range in which the output current density increases as the forward bias voltage increases. In other words, the second voltage range is a voltage range in which the photocurrent in the opposite direction to that in the first voltage range increases as the bias voltage applied between the pixel electrode 11 and the counter electrode 12 increases. The third voltage range is a voltage range between the first and second voltage ranges.

[0132] The first to third voltage ranges can also be distinguished by the slope of the graph of the photocurrent characteristics when linear vertical and horizontal axes are used. For reference, FIG. 7 shows the average slopes of the graphs in the first and second voltage ranges, respectively, indicated by dashed-dotted lines L1 and L2. As illustrated in FIG. 7 , the first, second, and third voltage ranges have different rates of change in output current density with increasing bias voltage. The third voltage range is also defined as a voltage range in which the rate of change in output current density with respect to bias voltage is smaller than the rates in the first and second voltage ranges. Alternatively, the third voltage range may be determined based on the position of a rising or falling edge in the graph showing the IV characteristics. The third voltage range is, for example, greater than −1 V and less than +1 V. In the third voltage range, the current density between the principal surfaces of the photoelectric conversion layer 15 hardly changes even when the bias voltage is changed. As illustrated in FIG. 7, in the third voltage range, the absolute value of the current density is, for example, 100 μA / cm ２ The following is the result.

[0133] Furthermore, when compared under the same illuminance conditions, the difference between the dark current and the light current in the third voltage range is smaller than the difference between the dark current and the light current in the first voltage range and the difference between the dark current and the light current in the second voltage range. Here, the dark current is the current that flows through the photoelectric conversion layer 15 in a state where no light is irradiated, and the light current is the current that flows through the photoelectric conversion layer 15 in a state where light is irradiated.

[0134] The IV characteristics of the photoelectric conversion section 13 shown in FIG. 7 are just an example, and the desired IV characteristics can be achieved by adjusting the configuration and materials of the photoelectric conversion layer 15 described above.

[0135] [Normal Imaging Operation of Imaging Device] Next, an operation for capturing a normal image will be described as an operation of the imaging device 100. In this specification, driving in a mode in which the imaging device 100 captures a normal image as described below may be referred to as normal imaging drive.

[0136] 8 is a diagram for explaining an example of the operation of normal imaging drive in the imaging device 100 according to the present embodiment. Fig. 8 shows the timing of the falling or rising edge of the synchronization signal, the temporal change in the magnitude of the bias voltage applied to the photoelectric conversion unit 13, and the timing of reset and exposure in each row of the pixel array PA (see Fig. 2).

[0137] More specifically, the top graph (a) in FIG. 8 shows the timing of the rising or falling edge of the vertical synchronization signal Vss. Graph (b) in FIG. 8 shows the timing of the rising or falling edge of the horizontal synchronization signal Hss. Graph (c) in FIG. 8 shows an example of the temporal change in the voltage Vb applied to the counter electrode 12 from the voltage supply circuit 32 via the sensitivity control line 42. Graph (d) in FIG. 8 shows the temporal change in the potential φ of the counter electrode 12, i.e., the bias voltage, relative to the potential of the pixel electrode 11. The double-headed arrow G3 in graph (d) of the potential φ in FIG. 8 indicates the third voltage range. In this example, the area above the double-headed arrow G3 corresponds to the first voltage range, and the area below the double-headed arrow G3 corresponds to the second voltage range. Chart (e) in FIG. 8 schematically shows the timing of resetting and exposing each row of the pixel array PA.

[0138] An example of the operation of normal imaging drive in the imaging device 100 will be described below with reference to Figures 2, 3, and 8. For simplicity, an example of operation will be described here in which the number of rows of pixels 10 included in the pixel array PA is eight, from row R0 to row R7. Note that the arrangement of pixel rows shown in chart (e) of Figure 8 does not need to match the actual arrangement of pixel rows, and the actual pixel arrangement is not particularly limited.

[0139] When acquiring an image, first, the charge accumulation region of each pixel 10 in the pixel array PA is reset, and the pixel signal after reset is read out. For example, as shown in FIG. 8 , resetting of the pixels 10 belonging to row R0 is started based on the vertical synchronization signal Vss (time t0). Note that the rectangles with sparse halftone dots in chart (e) of FIG. 8 schematically represent the signal readout period. This readout period may include a reset period for resetting the potential of the charge accumulation region of the pixel 10.

[0140] To reset the pixels 10 in the R0th row, the address transistor 26, whose gate is connected to the address control line 46, is turned ON by controlling the potential of the address control line 46 in the R0th row. Furthermore, the reset transistor 28, whose gate is connected to the reset control line 48, is turned ON by controlling the potential of the reset control line 48 in the R0th row. This connects the charge storage node 41 to the reset voltage line 44, and supplies the reset voltage Vr to the charge storage region. That is, the potentials of the charge storage node 41, the gate electrode 24g of the signal detection transistor 24, and the pixel electrode 11 of the photoelectric conversion unit 13 are reset to the reset voltage Vr. Then, a pixel signal corresponding to the potential of the charge storage region after reset is read from the pixels 10 in the R0th row via the vertical signal line 47. The pixel signal obtained at this time corresponds to the magnitude of the reset voltage Vr. After the pixel signal is read, the reset transistor 28 and the address transistor 26 are turned OFF. When reading out a pixel signal corresponding to the amount of charge accumulated in the charge accumulation region of the pixel 10 in the previous frame, the pixel signal may be read out before resetting.

[0141] In this example, as shown in FIG. 8 , the pixels 10 in each row, from row R0 to row R7, are reset sequentially row by row in accordance with the horizontal synchronization signal Hss. Hereinafter, the interval between pulses of the horizontal synchronization signal Hss, in other words, the period from when a row is selected to when the next row is selected, may be referred to as a "1H period." In this example, the period from time t0 to time t1 corresponds to the 1H period.

[0142] 8 , during the period from the start of image acquisition to the end of resetting all rows of the pixel array PA and the end of reading out pixel signals (time t0 to t9), the voltage supply circuit 32 applies to the counter electrode 12 a voltage V3 such that the voltage applied between the pixel electrodes 11 and the counter electrode 12 falls within the third voltage range. That is, during the period from the start of image acquisition to the start of the exposure period (time t9), a bias voltage within the third voltage range is applied between the pixel electrodes 11 and the counter electrode 12.

[0143] When a bias voltage within the third voltage range is applied between the pixel electrode 11 and the counter electrode 12, almost no signal charge is transferred from the photoelectric conversion layer 15 to the charge accumulation region. This is because, when a bias voltage within the third voltage range is applied between the pixel electrode 11 and the counter electrode 12, most of the positive and negative charges generated by light irradiation quickly recombine and disappear before being collected by the pixel electrode 11. Therefore, when a bias voltage within the third voltage range is applied between the pixel electrode 11 and the counter electrode 12, almost no charge is accumulated in the charge accumulation region even when light is incident on the photoelectric conversion layer 15. This suppresses the occurrence of unintended sensitivity during periods other than the exposure period. Such unintended sensitivity is also called "parasitic sensitivity."

[0144] In chart (e) of Fig. 8 , when focusing on a certain row (e.g., row R0), the period indicated by a rectangle with low density halftone dots and a rectangle with high density halftone dots represents a non-exposure period. In the example shown in Fig. 8 , a bias voltage within a third voltage range is applied between the pixel electrode 11 and the counter electrode 12 during the non-exposure period. Note that the voltage V3 for applying the bias voltage within the third voltage range between the pixel electrode 11 and the counter electrode 12 is not limited to 0 V. The voltage V3 is set, for example, in accordance with the reset voltage Vr so that the bias voltage is within the third voltage range.

[0145] Next, after resetting all rows of the pixel array PA and reading out pixel signals, an exposure period begins (time t9) based on the horizontal synchronization signal Hss. In the chart (e) of FIG. 8 , white rectangles schematically represent the exposure period for each row. The exposure period begins when the voltage supply circuit 32 switches the voltage applied to the counter electrode 12 to a voltage Ve, which is different from voltage V3. The voltage Ve is, for example, a voltage, such that the bias voltage applied between the pixel electrode 11 and the counter electrode 12 falls within the first voltage range, e.g., approximately 10 V. By applying the voltage Ve to the counter electrode 12, signal charges (holes in this example) in the photoelectric conversion layer 15 are collected by the pixel electrode 11 and stored in a charge accumulation region including the charge accumulation node 41. The voltage Ve is set, for example, in response to the reset voltage Vr so that the bias voltage falls within the first voltage range.

[0146] Next, the voltage supply circuit 32 switches the voltage applied to the counter electrode 12 back to voltage V3, thereby ending the exposure period (time t13). In this manner, in the imaging device 100, the voltage applied to the counter electrode 12 is switched between voltage V3 and voltage Ve, thereby switching between an exposure period and a non-exposure period. As can be seen from FIG. 8 , the start (time t9) and end (time t13) of the exposure period in this example are common to all pixels 10 included in the pixel array PA. In other words, the operation described here is an example in which the global shutter system is applied to the imaging element 110, and the imaging device 100 is driven by the global shutter system in which the exposure period is determined by changing the voltage applied by the voltage supply circuit 32 between the pixel electrodes 11 and the counter electrode 12.

[0147] Next, pixel signals are read out from the pixels 10 belonging to each row of the pixel array PA based on the horizontal synchronization signal Hss. In this example, starting from time t15, signal charges are read out from the pixels 10 belonging to each of rows R0 to R7, sequentially row by row. Hereinafter, the period from when a pixel 10 belonging to a certain row is selected until when a pixel 10 belonging to that row is selected again may be referred to as a "1V period." In this example, the period from time t0 to time t15 corresponds to the 1V period. The 1V period is, for example, one frame period.

[0148] When pixel signals are read from the pixels 10 belonging to row R0, starting at time t15 after the end of the exposure period, the address transistor 26 of row R0 is first turned ON. This causes a pixel signal corresponding to the amount of charge accumulated in the charge accumulation region during the exposure period, i.e., the potential of the charge accumulation region after the exposure period, to be output to the vertical signal line 47. Following the readout of the pixel signals, the reset transistor 28 may be turned ON to reset the pixels 10. Furthermore, if necessary, pixel signals may also be read out after this reset. After the readout of the pixel signals, the address transistor 26 is turned OFF, and if the pixels 10 are reset, the reset transistor 28 is also turned OFF.

[0149] After pixel signals are read from the pixels 10 belonging to each row of the pixel array PA, a difference is taken between the read pixel signals after reset and the pixel signals read between time t0 and time t9, thereby obtaining a signal from which fixed noise has been removed. This fixed noise removal is performed, for example, by the column signal processing circuit 37. Furthermore, the fixed noise removal may be performed before or after AD conversion of the pixel signals. The signals are read from the column signal processing circuit 37 by the horizontal signal readout circuit 38, and, for example, are processed by a signal processing circuit (not shown) or the like as necessary, and output to the outside of the imaging device 100. Note that, when resetting is performed after the readout of pixel signals after the exposure period, a signal from which fixed noise has been removed may be obtained by taking a difference between the readout of the pixel signals after the reset and the readout of the pixel signals before the reset.

[0150] During the non-exposure period, voltage V3 is applied to the counter electrode 12, and therefore a bias voltage within the third voltage range is applied to the photoelectric conversion unit 13. Therefore, even when light is incident on the photoelectric conversion layer 15, there is almost no further accumulation of signal charge in the charge accumulation region. This suppresses the generation of noise due to unintended charge mixing.

[0151] In this example, after the exposure period ends, the voltage applied to the counter electrode 12 is changed back to voltage V3, so that after the accumulation of signal charge in the charge accumulation region is completed, the photoelectric conversion unit 13 is in a state in which a bias voltage within the third voltage range is applied. With a bias voltage within the third voltage range applied, it is possible to suppress the movement of signal charge already accumulated in the charge accumulation region to the counter electrode 12 via the photoelectric conversion layer 15. In other words, by applying a bias voltage within the third voltage range to the photoelectric conversion unit 13, it is possible to retain the signal charge accumulated during the exposure period in the charge accumulation region. In other words, it is possible to suppress the occurrence of negative parasitic sensitivity due to the loss of signal charge from the charge accumulation region.

[0152] As described above, in this embodiment, the start and end of the exposure period are controlled by the voltage Vb applied to the counter electrode 12. That is, according to this embodiment, a global shutter function can be realized without providing a transfer transistor or the like in each pixel 10. In this embodiment, the electronic shutter is executed by controlling the voltage Vb without transferring signal charges via a transfer transistor, and therefore higher speed operation is possible. Furthermore, since there is no need to provide a separate transfer transistor or the like in each pixel 10, this is also advantageous for miniaturizing pixels.

[0153] Although the above description has been given of a case where the imaging device 100 is driven by the global shutter method as normal imaging drive, the imaging device 100 may also be driven by the rolling shutter method in normal imaging drive. In this case, for example, the voltage applied to the counter electrode 12 is constant at voltage Ve. Furthermore, for each pixel 10, the end of the reset operation marks the start of the exposure period, and the start of the subsequent readout operation marks the end of the exposure period. For example, when the reset operation and readout operation are performed at the timing shown in FIG. 8, the exposure period of the pixels 10 belonging to row R0 is from time t1 to time t15.

[0154] [Current Measurement Circuit] Next, we will explain the current measurement circuit 19 that measures the current flowing in the photoelectric conversion unit 13. In the imaging device 100, in addition to capturing normal images as described above, the current change detection circuit 130 detects changes in the current flowing in the photoelectric conversion unit 13 measured by the current measurement circuit 19, and it is possible to detect a moving object based on the detected changes in current.

[0155] FIG. 9 is a schematic diagram illustrating the arrangement of current measurement circuits 19 according to the present embodiment. For clarity, FIG. 9 illustrates only some of the components of the image sensor 110. Although FIG. 9 illustrates multiple current measurement circuits 19, this is for illustrative purposes only; the image pickup device 100 may include at least one current measurement circuit 19. In the description of FIG. 9 , the current measurement circuits 19 may be distinguished as current measurement circuits 19a, 19b, and 19c based on their arrangement. The image pickup device 100 may include at least one of the current measurement circuits 19a, 19b, and 19c. In FIG. 9 , a diagram corresponding to three pixels 10 is illustrated, with the photoelectric conversion units 13 and charge accumulation nodes 41 corresponding to each pixel 10 enclosed by dashed lines. In the description of FIG. 9 , the three pixels 10 may be distinguished as pixels 10a, 10b, and 10c, starting from the right.

[0156] The current measurement circuit 19 is disposed on wiring connected to the photoelectric conversion unit 13 and measures the current flowing through the photoelectric conversion unit 13. In this embodiment, the photoelectric conversion unit 13 has a counter electrode 12, a shield electrode 16, and a pixel electrode 11 as electrodes connected to the wiring, and therefore the current measurement circuits 19a, 19b, and 19c are connected to any of these electrodes. The current measurement circuit 19a is an example of a first current measurement circuit and is a current measurement circuit connected to the counter electrode 12. The current measurement circuit 19b is an example of a second current measurement circuit and is a current measurement circuit connected to the shield electrode 16. The current measurement circuit 19c is an example of a third current measurement circuit and is a current measurement circuit connected to the pixel electrode 11.

[0157] The current measurement circuit 19a is connected to the counter electrode 12. In the example shown in FIG. 9 , the current measurement circuit 19a is also connected to the voltage supply circuit 32 and is provided along the wiring path connecting the voltage supply circuit 32 and the counter electrode 12, i.e., along the sensitivity control line 42. Therefore, the current measurement circuit 19a measures the current flowing between the counter electrode 12 and the voltage supply circuit 32, thereby measuring the current flowing in the photoelectric conversion unit 13. This allows the current flowing in the photoelectric conversion unit 13 to be measured using existing wiring, thereby reducing the complexity of the pixel circuit and enabling miniaturization of the pixel 10. Furthermore, since the current measurement circuit 19a is connected to a common counter electrode 12 for, for example, two or more pixels 10, it can measure the current in the photoelectric conversion unit 13 across two or more pixels 10. This increases the measured current and improves the accuracy of detecting changes in current. The current measurement circuit 19a may be disposed within the voltage supply circuit 32. In other words, the current measurement circuit 19a may be part of the voltage supply circuit 32.

[0158] 9, the counter electrode 12 is divided into two parts, and a separate current measurement circuit 19a is connected to each of the two parts of the counter electrode 12. In other words, the imaging device 100 includes multiple current measurement circuits 19a that measure the currents flowing through the photoelectric conversion units 13 of different pixels 10. This allows the currents flowing through the photoelectric conversion units 13 to be measured for each region of the pixel 10 corresponding to the two parts of the counter electrode 12. In the example shown in FIG. 9, the currents flowing through the photoelectric conversion units 13 of pixels 10a and 10b and the current flowing through the photoelectric conversion unit 13 of pixel 10c can be measured separately. Note that the counter electrode 12 does not have to be divided, and in this case, a single current measurement circuit 19a may be used.

[0159] The current measurement circuit 19b is connected to the shield electrode 16 as described above. In the example shown in FIG. 9 , the current measurement circuit 19b is also connected to the shield voltage supply circuit 18 and is provided along the wiring path connecting the shield voltage supply circuit 18 and the shield electrode 16, i.e., along the shield wire 17. Therefore, the current measurement circuit 19b measures the current flowing in the photoelectric conversion unit 13 by measuring the current flowing between the shield electrode 16 and the shield voltage supply circuit 18. This allows the current flowing in the photoelectric conversion unit 13 to be measured using existing wiring, thereby reducing the complexity of the pixel circuit and enabling miniaturization of the pixel 10. Furthermore, since the current measurement circuit 19b is connected to a common shield electrode 16 for, for example, two or more pixels 10, it can measure the current in the photoelectric conversion unit 13 across two or more pixels 10. This increases the measured current and improves the accuracy of detecting changes in current. The current measurement circuit 19b may also be provided within the shield voltage supply circuit 18. In other words, the current measurement circuit 19 b may be a part of the shield voltage supply circuit 18 .

[0160] 9 includes only one current measurement circuit 19b, but similarly to the counter electrode 12, the shield electrode 16 may be divided into multiple portions, and a separate current measurement circuit 19b may be connected to each of the multiple portions of the shield electrode 16. When multiple current measurement circuits 19b are provided, a corresponding current measurement circuit 19b may be provided at each of the portions of the first wiring path connecting the shield electrode 16 of the pixel 10a and the shield voltage supply circuit 18 that do not overlap with the second wiring path connecting the shield electrode 16 of a pixel 10c different from the pixel 10a and the shield voltage supply circuit 18, and at each of the portions of the second wiring path that do not overlap with the first wiring path. For example, the shield line 17 may branch into multiple portions from the shield voltage supply circuit 18 toward the shield electrodes 16 of two or more pixels 10, and a corresponding current measurement circuit 19b may be provided for each of the multiple portions of the shield line 17. The individual current measurement circuit 19b individually measures the current flowing in, for example, two or more divided pixel regions, for example, a pixel region including the pixel 10a and a pixel region including the pixel 10c.

[0161] The current measurement circuit 19c is connected to the pixel electrode 11 via the reset transistor 28 and the charge storage node 41. The current measurement circuit 19c is also connected to the reset voltage source 34 and is located midway along the wiring path connecting the reset voltage source 34 and the pixel electrode 11, i.e., the reset voltage line 44. Therefore, the current measurement circuit 19c measures the current flowing in the photoelectric conversion unit 13 by measuring the current flowing between the pixel electrode 11 and the reset voltage source 34. This allows the current flowing in the photoelectric conversion unit 13 to be measured using existing wiring, thereby reducing the complexity of the pixel circuit and enabling miniaturization of the pixel 10. Furthermore, the current in the photoelectric conversion unit 13 can be measured across two or more pixels 10, increasing the measured current and improving the accuracy of detecting current changes. Furthermore, because the pixel electrode 11 is connected to the reset transistor 28 via the charge storage node 41, the current flowing in the photoelectric conversion unit 13 is detected by turning on the reset transistor 28 and allowing a current to flow through the current measurement circuit 19c. The current measurement circuit 19c may be disposed within the reset voltage source 34. In other words, the current measurement circuit 19c may be a part of the reset voltage source 34.

[0162] 9 , there is only one current measurement circuit 19c, but multiple current measurement circuits 19c may be provided. In this case, a corresponding current measurement circuit 19c may be provided in a portion of the first wiring path connecting the charge storage node 41 of the pixel 10a and the reset voltage source 34 that does not overlap with a second wiring path connecting the charge storage node 41 of a pixel 10c different from the pixel 10a and the reset voltage source 34, and in a portion of the second wiring path that does not overlap with the first wiring path. For example, the reset voltage line 44 may branch into multiple portions from the reset voltage source 34 toward the charge storage nodes 41 of two or more pixels 10, and a current measurement circuit 19c may be provided corresponding to each of the multiple portions of the reset voltage line 44. The individual current measurement circuits 19c individually measure the current flowing in, for example, two or more divided pixel regions, such as a pixel region including the pixel 10a and a pixel region including the pixel 10c.

[0163] Furthermore, since the reset transistor 28 can be switched ON and OFF, for example, by turning ON the reset transistor 28 for each row or column, the current measurement circuit 19c can detect the current flowing through the photoelectric conversion unit 13 of only the pixel 10 corresponding to the reset transistor 28 that has been turned ON.

[0164] The current measurement circuit 19 can be a measurement circuit used in known ammeters, such as a measurement circuit using a shunt resistor or a measurement circuit using a magnetic field, and is not particularly limited. Specifically, the current measurement circuit 19 includes, for example, a shunt resistor, an amplifier circuit that amplifies the potential difference generated by the shunt resistor, and an AD conversion circuit that AD converts the output of the amplifier circuit, outputting the AD-converted value at a predetermined sampling interval. The current measurement circuit 19 may also include an integrator for peak-holding the output of the amplifier circuit. In this case, the AD conversion circuit AD converts the output of the amplifier circuit integrated by the integrator and resets the integrator at a predetermined interval. This allows the current change to be retained and output even if the current change occurs only between AD conversion sampling periods. Therefore, current changes can be easily detected even if the AD conversion sampling interval is extended. Furthermore, current changes that occur over a short period of time, such as a period shorter than one frame period, can also be detected.

[0165] Furthermore, the number of current measurement circuits 19 is, for example, smaller than the number of pixels 10. In other words, the current measurement circuit 19 is provided in common for two or more pixels 10 and can measure the current flowing in the photoelectric conversion unit 13 of a pixel region including two or more pixels 10. This makes it possible to miniaturize the circuitry of the imaging device 100 and reduce power consumption in the operation of detecting changes in the current flowing in the photoelectric conversion unit 13. Furthermore, the amount of current measured by the current measurement circuit 19 increases, making it easier to detect changes in current.

[0166] [Current Change Detection Operation of Imaging Device] Next, as an operation of the imaging device 100, an operation in which a moving object is detected by detecting a change in the current flowing in the photoelectric conversion unit 13 will be described with reference to FIG. 9 and FIGS. 10A and 10B described below. In this specification, driving in a mode in which the current change detection circuit 130 described below detects a change in the current flowing in the photoelectric conversion unit 13 may be referred to as current change detection driving. Furthermore, because the current change detection circuit 130 can detect a moving object based on a change in the detected current, current change detection driving may also be referred to as moving object detection driving.

[0167] First, in the current change detection drive, for example, the voltage Vb supplied from the voltage supply circuit 32 is supplied so as to be lower or higher than the shield voltage Vs supplied from the shield voltage supply circuit 18 and the reset voltage Vr supplied from the reset voltage source 34. In other words, voltages are supplied from each voltage supply circuit so as to generate a potential difference between the two electrodes facing each other across the photoelectric conversion layer 15. Specifically, the voltages Vb, Vs, and Vr are set to 10 V, 0 V, and 1 V, respectively. As a result, when light enters the photoelectric conversion unit 13, photoelectric conversion occurs in the photoelectric conversion unit 13, causing a current to flow through the photoelectric conversion unit 13. The current measurement circuit 19, connected to each electrode, measures the current flowing through the photoelectric conversion unit 13. The current measurement circuit 19 outputs the current measurement result, for example, an AD-converted digital value, to the current change detection circuit 130. At this time, in order to increase the sensitivity of the current change detection circuit 130 in detecting changes in current, the difference between the voltage Vb and the shield voltage Vs and the difference between the voltage Vb and the reset voltage Vr may be set to voltages that are larger than those in normal imaging drive.

[0168] When the current measurement circuit 19a measures the current, it does not matter which is larger: the difference between the voltage Vb and the shield voltage Vs, or the difference between the voltage Vb and the reset voltage Vr. Furthermore, when the current measurement circuit 19b measures the current, the difference between the voltage Vb and the shield voltage Vs may be larger than the difference between the voltage Vb and the reset voltage Vr. This makes it easier for current to flow through the shield electrode 16. A specific example of this case is when the voltage Vb is 10 V, the shield voltage Vs is 0 V, and the reset voltage Vr is 3 V. Furthermore, when the current measurement circuit 19c measures the current, the difference between the voltage Vb and the reset voltage Vr may be larger than the difference between the voltage Vb and the shield voltage Vs. This makes it easier for current to flow through the pixel electrode 11. A specific example of this case is when the voltage Vb is 10 V, the shield voltage Vs is 4 V, and the reset voltage Vr is 0.5 V.

[0169] Next, the current change detection circuit 130 acquires the output from the current measurement circuit 19 and detects a change in the current flowing through the photoelectric conversion unit 13 measured by the current measurement circuit 19. When the amount of light incident on the photoelectric conversion unit 13 changes, the amount of charge generated by the photoelectric conversion unit 13 changes, causing a change in the current flowing through the photoelectric conversion unit 13. The current change detection circuit 130 detects a change in the current flowing through the photoelectric conversion unit 13 measured by the current measurement circuit 19, for example, by detecting whether a change equal to or greater than a predetermined threshold occurs in the output from the current measurement circuit 19. In this specification, a change in current detected by the current change detection circuit 130 refers to a change that satisfies a predetermined condition, such as a change equal to or greater than a certain threshold, and means a substantial change. Furthermore, the change in current detected by the current change detection circuit 130 does not include a change in current caused by a change in the voltage supplied to the photoelectric conversion unit 13, such as when the voltage supplied by various voltage supply circuits that supply voltage to the photoelectric conversion unit 13 changes. That is, the current change detection circuit 130 detects a change in current caused by a change in the amount of light incident on the photoelectric conversion unit 13 over time.

[0170] Furthermore, detection of a change in current by the current change detection circuit 130 may be performed by comparing the output value of the current measurement circuit 19 with the previous output value for each AD conversion sampling, or by comparing the output value with the average value of a predetermined number of sampled output values. Furthermore, if the current measurement circuit 19 includes an integrator, the current change detection circuit 130 detects a change in current by comparing the difference between the output values ​​from the current measurement circuit 19. Furthermore, in applications where the background is fixed, such as monitoring applications, the current change detection circuit 130 may detect a change in current by determining whether the output from the current measurement circuit 19 falls outside a predetermined range.

[0171] An analog signal may be output from the current measurement circuit 19 to the current change detection circuit 130. In this case, the current change detection circuit 130 may have an AD conversion circuit that performs AD conversion on the analog signal, or may have a comparator that temporarily holds the analog signal and compares the previous and subsequent analog signals.

[0172] 10A and 10B are diagrams for explaining an example of the operation and output results of current change detection driving in the imaging device 100 according to the present embodiment.

[0173] 10A and 10B show, as an example, a scene in which a background exists within the imaging range of imaging device 100 and a ball coming from outside the imaging range crosses the imaging range. Fig. 10A shows the state in which the ball enters the imaging range from outside, and Fig. 10B shows the state in which the ball is in the middle of crossing the imaging range.

[0174] 10A , when a ball enters the imaging range and is brighter than the background, the current flowing in photoelectric conversion unit 13 due to photoelectric conversion of light from the ball is greater than the current flowing in photoelectric conversion unit 13 due to photoelectric conversion of light from the background in the same range as the ball. As a result, the current flowing in photoelectric conversion unit 13 after the ball enters the imaging range increases compared to the current flowing in photoelectric conversion unit 13 before the ball crosses the imaging range, and the current flowing in photoelectric conversion unit 13 changes. Therefore, current change detection circuit 130 can detect the presence of a moving object, such as a ball, that has entered the imaging range by detecting a change in the current measured by current measurement circuit 19.

[0175] 10B , when a ball moves within the imaging range, the light from the background is blocked by the ball, changing the amount of light incident on the photoelectric conversion unit 13 from the background, and therefore changing the current flowing through the photoelectric conversion unit 13. For example, when a gray ball passes over a background part with high light reflectivity, such as a cloud, the current flowing through the photoelectric conversion unit 13 decreases compared to before the ball passed over the cloud. Therefore, the current change detection circuit 130 can detect the presence of a moving object within the imaging range by detecting a change in the current measured by the current measurement circuit 19.

[0176] The current change detection circuit 130 generates a detection signal related to a moving object moving within the imaging range based on, for example, a change in the detected current. The detection signal is, for example, a signal indicating whether or not a moving object is present. The detection signal may include information related to the amount of change in current detected by the current change detection circuit 130. The detection signal generated by the current change detection circuit 130 is output to, for example, the drive control circuit 140 and used to control the driving of the imaging device 100 in the drive control circuit 140. The detection signal may also be output to the outside of the imaging device 100.

[0177] 10A and 10B , this means that, for example, even if one current measurement circuit 19a is connected to an undivided counter electrode 12, a moving object can be detected by the current change detection circuit 130. Furthermore, if the counter electrode 12 or the like is divided into pixel regions each consisting of several pixels 10, and a change in current can be detected in a plurality of pixel regions, moving objects can be detected with higher accuracy.

[0178] In this way, when a moving object comes into the imaging range of the imaging device 100 from outside the range, or when a moving object moves within the imaging range of the imaging device 100, light from the background is blocked by the moving object, causing a change in the amount of light incident on the photoelectric conversion unit 13, resulting in a change in the current flowing in the photoelectric conversion unit 13. Therefore, by having the current change detection circuit 130 detect a change in the current measured by the current measurement circuit 19, it is possible to detect both bright and dark moving objects.

[0179] Furthermore, when the current measurement circuit 19c measures the current, the reset transistor 28 is turned ON and the current measurement circuit 19c measures the current flowing through the wiring connecting the reset voltage source 34 and the reset transistor 28, thereby enabling the current change detection circuit 130 to detect a moving object. In this case, it is possible to detect a moving object in any region within the imaging range by determining which of the pixels 10's reset transistors 28 are turned ON. Furthermore, by changing the region of the pixels 10 whose reset transistors 28 are turned ON over time, it is possible to detect moving objects in any region within the imaging range while also detecting moving objects in the entire imaging range.

[0180] Furthermore, even when the current measurement circuits 19 a and 19 b measure current, the counter electrode 12 and the shield electrode 16 may be divided into sections to define the imaging range in advance. This allows the current change detection circuit 130 to detect a moving object for each section. For example, if the counter electrode 12 is divided into four sections, upper left, upper right, lower right, and lower left, it is possible to detect in which of the four sections a moving object is present.

[0181] Furthermore, since changes in brightness due to ambient light such as sunlight can generally occur outdoors during the day, the current change detection circuit 130 may be configured to detect changes in current flowing through the photoelectric conversion unit 13, taking into account such changes in brightness. Specifically, this may involve increasing the detection threshold, analyzing the frequency components of changes in current corresponding to changes in brightness of ambient light, and extracting and detecting only changes in current due to the moving object, or using multiple current measurement circuits 19 to extract and detect changes in current due to the moving object while canceling out changes in current due to ambient light from the current measured by each current measurement circuit 19.

[0182] On the other hand, the accuracy of moving object detection by the current change detection circuit 130 is high at night and indoors. This is because normal indoor lighting has small changes in brightness and is less susceptible to the influence of ambient light, such as sunlight, which has large changes in brightness. The same is true at night. Furthermore, at night, the accuracy of moving object detection can be further improved by using a lighting device 200 that emits light including near-infrared rays.

[0183] [Control of Drive Mode] Next, control of drive mode by the drive control circuit 140 will be described. The drive control circuit 140 controls, for example, the image capture device 100 to perform current change detection drive and normal image capture drive. As described above, current change detection drive is a drive mode in which the current change detection circuit 130 detects changes in the current flowing in the photoelectric conversion unit 13, and normal image capture drive is a drive mode in which the signal detection circuit 14 detects pixel signals based on the charges generated in the photoelectric conversion unit 13. The drive control circuit 140 may cause the image capture device 100 to perform current change detection drive and normal image capture drive by switching between them, or may cause the image capture device 100 to perform current change detection drive and normal image capture drive simultaneously.

[0184] For example, if the current change detection circuit 130 detects a change in the current flowing through the photoelectric conversion unit 13 while the imaging device 100 is operating in current change detection drive, the drive control circuit 140 switches the drive mode from current change detection drive to normal imaging drive. At this time, the current change detection circuit 130 may detect a moving object by detecting a change in current. This allows the imaging device 100 to operate in current change detection drive without operating circuits used for normal imaging, such as in normal imaging drive, thereby reducing power consumption. Furthermore, privacy considerations can be maintained even when the imaging device 100 is used for surveillance purposes.

[0185] For example, while the drive control circuit 140 controls the imaging device 100 to perform current change detection drive, the drive control circuit 140 may place at least some of the signal detection circuit 14 and the circuits connected to the signal detection circuit 14 in an off state or standby state. The circuits connected to the signal detection circuit 14 are circuits involved in outputting pixel signals, including circuits that drive the signal detection circuit 14, such as the vertical scanning circuit 36, and circuits that process pixel signals output from the signal detection circuit 14, such as the column signal processing circuit 37 and the horizontal signal readout circuit 38. The off state of a circuit refers to a state in which the power supply is cut off by a switch or the like provided in each circuit. The standby state of a circuit refers to a state in which at least some of the circuit does not operate or operates at lower power than normal, even though power is supplied. The standby state is, for example, a state in which power consumption is lower than normal imaging drive. Therefore, in current change detection drive, for example, at least some circuit elements of the signal detection circuit 14 do not operate, or signal processing is not performed on pixel signals detected by the signal detection circuit 14. As a result, in the current change detection driving, the signal derived from the pixel signal is not output to the outside of the imaging device 100 .

[0186] On the other hand, once the current change detection circuit 130 detects a change in current, that is, once a moving object is detected, the imaging device 100 switches to normal imaging drive and can output an image containing more detailed information about the subject.

[0187] FIG. 11 is a diagram illustrating a first example of drive mode control in the imaging device 100 according to the present embodiment. As shown in FIG. 11 , in the first example, the drive control circuit 140 first causes the imaging device 100 to perform current change detection drive. In this current change detection drive, no signal is output to the outside of the imaging device 100. Therefore, the image processing unit 300 and other units that perform post-processing of the output from the imaging device 100 do not need to perform image processing, and are in a standby state, for example. This reduces power consumption in post-processing. It also reduces the amount of image storage required. In this case, the image processing unit 300 and other units that perform post-processing of the output from the imaging device 100 may be in an off state.

[0188] Furthermore, in the current change detection drive, the current change detection circuit 130 generates a detection signal indicating whether or not a moving object is present within the imaging range, depending on whether or not the current measured by the current measurement circuit 19 flowing in the photoelectric conversion unit 13 has changed, and outputs the detection signal to the drive control circuit 140. Furthermore, the current change detection circuit 130 may generate a detection signal only when it detects a change in the current flowing in the photoelectric conversion unit 13, and may not generate a detection signal when it does not detect a change in the current. Note that in the current change detection drive, the detection signal may be output to an external device of the imaging device 100, such as the image processing unit 300.

[0189] The drive control circuit 140 continues the current change detection drive when the current change detection circuit 130 does not detect a change in the current flowing in the photoelectric conversion unit 13. On the other hand, the drive control circuit 140 switches the drive mode from the current change detection drive to the normal imaging drive when the current change detection circuit 130 detects a change in the current flowing in the photoelectric conversion unit 13. In the normal imaging drive, a signal including image data is output to the outside of the imaging device 100. For example, in the normal imaging drive, the image processing unit 300, which performs post-processing of the output from the imaging device 100, performs image processing and storage on the image data output from the imaging device 100. In other words, in the normal imaging drive, detailed images can be acquired.

[0190] The drive control circuit 140 switches the drive mode from normal imaging drive to current change detection drive after a predetermined time has elapsed since the imaging device 100 started normal imaging drive. This enables the imaging device 100 to be driven with low power consumption. After switching to current change detection drive, the above operation is performed again.

[0191] Furthermore, the drive control circuit 140 may also cause the imaging device 100 to perform current change detection drive while simultaneously performing normal imaging drive. FIG. 12 is a diagram for explaining a second example of drive mode control in the imaging device 100 according to this embodiment. The second example shown in FIG. 12 is the same as the first example in that the drive control circuit 140 first causes the imaging device 100 to perform only current change detection drive, and then switches to normal imaging drive when the current change detection circuit 130 detects a change in the current flowing in the photoelectric conversion unit 13. As shown in FIG. 12 , in the second example, while the drive control circuit 140 causes the imaging device 100 to perform normal imaging drive, the drive control circuit 140 also causes the imaging device 100 to perform current change detection drive in parallel. If the current change detection circuit 130 detects a change in the current flowing in the photoelectric conversion unit 13 during current change detection drive during normal imaging drive, the drive control circuit 140 continues normal imaging drive. On the other hand, if the current change detection circuit 130 does not detect a change in the current flowing in the photoelectric conversion unit 13 during current change detection drive during normal imaging drive, the drive control circuit 140 switches from simultaneous drive of normal imaging drive and current change detection drive to drive only with current change detection drive. In this case, because changes in the current flowing in the photoelectric conversion unit 13 are detected even during normal imaging drive, if a moving object is no longer present, the drive mode switches to one in which only current change detection drive is performed, making it possible to reduce power consumption and the image storage capacity. On the other hand, since images can be acquired at all times while a moving object is present, moving objects can be captured without interruption.

[0192] In the second example, since the signal charge accumulated in the charge accumulation node 41 connected to the pixel electrode 11 is used to detect a pixel signal, measuring the current using the current measurement circuit 19c connected to the charge accumulation node 41 does not allow the current flowing in the photoelectric conversion unit 13 to be measured. Therefore, the current change detection circuit 130 detects changes in the current measured by the current measurement circuit 19a connected to the counter electrode 12 or the current measurement circuit 19b connected to the shield electrode 16. In this case, from the viewpoint of easily detecting changes in the current flowing in the photoelectric conversion unit 13 for detecting a moving object, the drive control circuit 140 may drive the imaging device 100 using a rolling shutter method in which the voltages supplied by the voltage supply circuit 32 and the shield voltage supply circuit 18 do not change during normal imaging drive. In addition, when the imaging device 100 is driven using a global shutter method, the current change detection circuit 130 detects changes in the current measured by the current measurement circuit 19, for example, by avoiding timing when the voltage supplied to the photoelectric conversion unit 13 by the voltage supply circuit 32 or the like changes.

[0193] Furthermore, the drive control circuit 140 may cause the imaging device 100 to always simultaneously perform the current change detection drive and the normal imaging drive, regardless of whether the current change detection circuit 130 detects a change in the current flowing through the photoelectric conversion unit 13. FIG. 13 is a diagram illustrating a third example of drive mode control in the imaging device 100 according to this embodiment. As shown in FIG. 13 , in the third example, the drive control circuit 140 controls the imaging device 100 to always simultaneously perform the current change detection drive and the normal imaging drive. That is, in the third example, the operation performed after the change in the current flowing through the photoelectric conversion unit 13 in the second example is always performed. This allows moving object detection and normal image capture to always be performed simultaneously. In this case, in the current change detection drive, the imaging device 100 outputs a signal including image data generated by the normal imaging drive to the outside of the imaging device 100 only if the current change detection circuit 130 detects a change in the current flowing through the photoelectric conversion unit 13. An image processing unit 300 and the like that perform post-stage processing of the output from the imaging device 100 perform image processing and storage on the image data output from the imaging device 100 .

[0194] On the other hand, in the current change detection drive, if the current change detection circuit 130 does not detect a change in the current flowing through the photoelectric conversion unit 13, the imaging device 100 does not output a signal to the outside of the imaging device 100. Therefore, the image processing unit 300 and the like that perform post-processing of the output from the imaging device 100 do not need to perform image processing, and are in a standby state, for example. This makes it possible to reduce power consumption in post-processing and also reduces the amount of image storage capacity.

[0195] Furthermore, in the third example, the detection signal generated by the current change detection circuit 130 and indicating whether a moving object has been detected (or whether a change in current has been detected) may be output to an external device of the imaging device 100, such as the image processing unit 300. This makes it possible, when a moving object is detected, to add data indicating that a moving object has been detected to an image to be saved in a subsequent process. Furthermore, when a moving object is not detected, the imaging device 100 may output a signal including image data or the like to an external device of the imaging device 100 together with the detection signal. The image processing unit 300 or the like that receives the output from the imaging device 100 thins out and saves images, for example, one every 10 seconds, when a moving object is not detected, and constantly saves images when a moving object is detected.

[0196] Furthermore, in cases where the pixel area measuring the current flowing through the photoelectric conversion unit 13 is divided, such as when the counter electrode 12 is divided, the current change detection circuit 130 may limit the pixel area for detecting a moving object during current change detection driving. For example, when an object with varying brightness, such as a light source or a flag moving in the wind, is captured, the current flowing through the photoelectric conversion unit 13 may change in the same way as a moving object, potentially resulting in a constant state of a moving object being detected. In this case, pixel areas for detecting moving objects may be set in advance, excluding pixel areas where objects with varying brightness, such as a light source or a flag moving in the wind, are present. By doing so, during current change detection driving, the current change detection circuit 130 can detect an object that is actually moving, without detecting an object that is not actually moving, and generate a detection signal related to the moving object. This prevents unintended detection of a moving object, which is expected to reduce power consumption of the imaging device 100 and the camera system 1. The current change detection circuit 130 may, for example, exclude pixel areas in which a change in current continues for a predetermined period of time from pixel areas that are the target of moving object detection, and detect whether or not a moving object is present.

[0197] Other Embodiments Although the imaging device and camera system according to the present disclosure have been described above based on the embodiments, the present disclosure is not limited to these embodiments.

[0198] For example, in the above embodiment, the signal detection transistor 24, the address transistor 26, and the reset transistor 28 are each an N-channel MOSFET, but this is not limiting. The signal detection transistor 24, the address transistor 26, and the reset transistor 28 may each be a P-channel MOSFET. All of these do not have to be unified as either an N-channel MOSFET or a P-channel MOSFET. Furthermore, the signal detection transistor 24 and / or the address transistor 26 may be other transistors such as bipolar transistors instead of field-effect transistors.

[0199] Furthermore, in the above embodiment, an example in which the current change detection circuit 130 detects a moving object has been described, but the current change detection circuit 130 can perform similar detection not only when there is a moving object that simply moves significantly, but also when the object vibrates, when an object flutters like a flag, when an object changes in brightness in the imaging range, etc. In other words, the current change detection circuit 130 may generate a detection signal related to the change in the object by detecting a change in the current measured by the current measurement circuit 19.

[0200] Furthermore, the camera system 1 and the imaging device 100 do not need to include all of the components described in the above embodiments, and may be configured with only the components required to perform the intended operation.

[0201] For example, the imaging device 100 does not need to include the shield electrode 16 , the shield line 17 , and the shield voltage supply circuit 18 .

[0202] In the above embodiment, the processes performed by specific processing units such as the current change detection circuit 130 and the drive control circuit 140 may be performed by other processing units. The order of multiple processes may be changed, or multiple processes may be performed in parallel.

[0203] Furthermore, the general or specific aspects of the present disclosure may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0204] For example, the present disclosure may be realized as a camera system or imaging device according to the above embodiments, as a processing circuit for an imaging device having the functions of the current change detection circuit and drive control circuit of the above embodiments, as an imaging method for an imaging device performed by the current change detection circuit and drive control circuit of the above embodiments, as a program for causing a computer to execute such an imaging method, or as a computer-readable non-transitory recording medium on which such a program is recorded.

[0205] In addition, various modifications that would occur to those skilled in the art without departing from the spirit of the present disclosure are also included within the scope of the present disclosure. Furthermore, the components of multiple embodiments may be combined in any manner without departing from the spirit of the present disclosure.

[0206] The imaging device etc. according to the present disclosure can be applied to, for example, an image sensor, etc. Furthermore, the imaging device etc. according to the present disclosure can be used in a medical camera, a robot camera, a security camera, a camera mounted on a vehicle, etc.

[0207] 1 Camera system 10, 10a, 10b, 10c Pixel 11 Pixel electrode 12 Counter electrode 13 Photoelectric conversion section 14 Signal detection circuit 15 Photoelectric conversion layer 15A Photoelectric conversion structure 15e Electron blocking layer 15h Hole blocking layer 16 Shield electrode 17 Shield wire 18 Shield voltage supply circuit 19, 19a, 19b, 19c Current measurement circuit 20 Semiconductor substrate 20t Element isolation region 24 Signal detection transistor 24d, 24s, 26s, 28d, 28s Impurity region 24g, 26g, 28g Gate electrode 26 Address transistor 28 Reset transistor 32 Voltage supply circuit 34 Reset voltage source 36 Vertical scanning circuit 37 Column signal processing circuit 38 Horizontal signal readout circuit 40 Power line 41 Charge storage node 42 Sensitivity control line 44 Reset voltage line 46 Address control line 47 Vertical signal line 48 Reset control line 49 Horizontal common signal line 50 Interlayer insulating layer 52 Plug 53 Wiring 54, 55 Contact plug 56 Wiring layer 100 Imaging device 110 Imaging element 130 Current change detection circuit 140 Drive control circuit 150m Mixed layer 150n n-type semiconductor layer 150p p-type semiconductor layer 200 Lighting device 300 Image processing unit 400 System controller

Claims

1. a photoelectric conversion unit including a first electrode, a second electrode facing the first electrode, and a photoelectric conversion layer located between the first electrode and the second electrode; a first voltage supply circuit that applies a voltage between the first electrode and the second electrode; a charge accumulation unit connected to the first electrode and configured to accumulate charges generated by the photoelectric conversion unit; a signal detection circuit that detects a signal based on the charge accumulated in the charge accumulation unit; at least one current measurement circuit that measures a current flowing in the photoelectric conversion unit; a current change detection circuit that detects a change in the current flowing in the photoelectric conversion unit measured by the at least one current measurement circuit, Imaging device.

2. a charge accumulation unit connected to the first electrode and configured to accumulate the charges generated by the photoelectric conversion unit; the first voltage supply circuit applies the voltage between the first electrode and the second electrode by supplying a predetermined voltage to the second electrode; the at least one current measurement circuit includes a first current measurement circuit connected to the second electrode; The imaging device according to claim 1 .

3. the second electrode is divided into a plurality of sub-second electrodes, the at least one current measurement circuit includes a plurality of current measurement circuits; the plurality of current measurement circuits are a plurality of the first current measurement circuits, each of the plurality of auxiliary second electrodes is connected to a corresponding one of the plurality of first current measurement circuits; The imaging device according to claim 2 .

4. The photoelectric conversion unit further includes a third electrode facing the second electrode with the photoelectric conversion layer sandwiched therebetween; the at least one current measurement circuit includes a second current measurement circuit connected to the third electrode; The imaging device according to claim 1 .

5. the third electrode is divided into a plurality of sub-third electrodes, the at least one current measurement circuit includes a plurality of current measurement circuits; the plurality of current measurement circuits are a plurality of second current measurement circuits, each of the plurality of auxiliary third electrodes is connected to a corresponding one of the plurality of second current measurement circuits; The imaging device according to claim 4 .

6. Further comprising: a second voltage supply circuit that supplies a predetermined voltage to the charge storage unit; the at least one current measurement circuit includes at least one third current measurement circuit connected to the second voltage supply circuit; The imaging device according to claim 1 .

7. further comprising a plurality of pixels; each of the plurality of pixels includes the photoelectric conversion unit, the signal detection circuit, and the charge accumulation unit; the at least one third current measurement circuit includes a plurality of third current measurement circuits; the plurality of pixels include a first pixel and a second pixel different from the first pixel, a third current measurement circuit corresponding to the first wiring path connecting the charge accumulation portion included in the first pixel and the second voltage supply circuit is located at a location that does not overlap with a second wiring path connecting the charge accumulation portion included in the second pixel and the second voltage supply circuit, and a location that does not overlap with the first wiring path of the second wiring path; The imaging device according to claim 6 .

8. the at least one current measurement circuit includes a plurality of current measurement circuits; The imaging device according to claim 1 .

9. further comprising a plurality of pixels; each of the plurality of pixels includes the photoelectric conversion unit and the signal detection circuit; the number of the at least one current measurement circuits is less than the number of the plurality of pixels; The imaging device according to claim 1 .

10. a drive control circuit for controlling the drive of the imaging device; The drive control circuit controls the imaging device to perform (i) a current change detection drive in which the current change detection circuit detects the change in the current flowing in the photoelectric conversion unit, and (ii) a normal imaging drive in which the signal detection circuit detects the signal based on the charge generated in the photoelectric conversion unit. The imaging device according to claim 1 .

11. the drive control circuit switches the drive of the imaging device from the current change detection drive to the normal imaging drive when the current change detection circuit detects the change in the current flowing in the photoelectric conversion unit while the imaging device is performing the current change detection drive. The imaging device according to claim 10.

12. the drive control circuit switches the drive of the imaging device from the normal imaging drive to the current change detection drive after a predetermined time has elapsed since the imaging device started the normal imaging drive. The imaging device according to claim 11.

13. the drive control circuit places the signal detection circuit and at least some of the circuits connected to the signal detection circuit in an off state or a standby state while controlling the imaging device to perform the current change detection drive; The imaging device according to claim 10.

14. the drive control circuit controls the imaging device to simultaneously perform the current change detection drive and the normal imaging drive. The imaging device according to claim 10.

15. An imaging device according to any one of claims 1 to 14; and a lighting device that emits light including near-infrared rays. Camera system.