JP2022109556A - Imaging device and imaging method - Google Patents

Abstract

To provide a new imaging device using a nondestructive readout.SOLUTION: An imaging device 20 is configured to supply a first voltage V1 to a first electrode 101A in a first period Te1 within an accumulation period Te; to supply a second voltage V2 different from the first voltage V1 to the first electrode 101A in a second period Te2 within the accumulation period Te. At least some pixels 101 in multiple pixels 101 are configured to sequentially output signals corresponding to the amount of the signals charge accumulated in a charge accumulation unit 22 to the first period Te1 in a non-destructive manner, and the multiple pixels 101 are configured to sequentially output signals corresponding to the amount of signals charge accumulated in the charge accumulation unit 22 in a non-accumulation period Tr after accumulation period Te in non-accumulation period Tr after the accumulation period Te.SELECTED DRAWING: Figure 5

Description

The present invention relates to an imaging apparatus and an imaging method capable of nondestructive readout.

In general, readout of pixel signals of an imaging device is performed by destructive readout. Destructive readout involves a reset operation that empties the signal charge stored in the pixels. On the other hand, non-destructive readout is known in which signal charges accumulated in pixels are not reset and are read out in an exposed state. Pixel information during exposure can be obtained by performing non-destructive readout. Japanese Patent Application Laid-Open No. 2002-200001 discloses an imaging device that achieves a high dynamic range by performing non-destructive readout.

JP 2007-194687 A

A novel imaging device and imaging method using non-destructive readout are provided.

In order to solve the above problems, an imaging device according to one aspect of the present disclosure includes a plurality of pixels capable of nondestructive readout and a voltage supply circuit, and each of the plurality of pixels includes a first electrode, a a photoelectric conversion portion including two electrodes and a photoelectric conversion layer that is positioned between the first electrode and the second electrode and generates a signal charge by photoelectric conversion; and electrically connected to the second electrode, a charge accumulating portion for accumulating the signal charge; an accumulation period, which is a period during which the signal charge is generated and accumulated, includes a first period and a second period; a first voltage is supplied to the first electrode during the second period, and a second voltage different from the first voltage is supplied to the first electrode during the second period; A signal corresponding to the amount of the signal charge accumulated in the charge accumulation section is sequentially output in the first period in a non-destructive manner, and the plurality of pixels are configured to output the amount of the signal charge accumulated in the charge accumulation section. are sequentially output during the non-accumulation period following the accumulation period.

According to the present disclosure, it is possible to provide a novel imaging device and imaging method using nondestructive readout.

FIG. 1 is a block diagram showing a configuration example of a camera system including an imaging device according to the first embodiment. FIG. 2 is a block diagram showing a configuration example of an imaging device according to the first embodiment. 3 is a circuit diagram showing a configuration example of a pixel in FIG. 2. FIG. FIG. 4 is a cross-sectional view schematically showing the structure of the photoelectric conversion portion and the FD in FIG. FIG. 5 is a timing chart corresponding to a first imaging operation example in the imaging apparatus according to the first embodiment. FIG. 6 is a timing chart showing a second imaging operation example in the imaging apparatus according to the first embodiment. FIG. 7 is a timing chart showing a third imaging operation example in the imaging apparatus according to the first embodiment. FIG. 8 is a diagram showing an example of spectral characteristics of a photoelectric conversion layer in an imaging device according to the second embodiment. FIG. 9 is a timing chart showing an example of imaging operation in the imaging apparatus according to the second embodiment. FIG. 10 is a timing chart showing an example of imaging operation in the imaging device according to the third embodiment. FIG. 11 is a diagram showing an example of a captured image in the imaging device according to the third embodiment.

First, an outline of the present disclosure will be described.

An imaging device according to an aspect of the present disclosure includes a plurality of pixels capable of nondestructive readout and a voltage supply circuit, and each of the plurality of pixels includes a first electrode, a second electrode, and the first electrode. a photoelectric conversion portion located between one electrode and the second electrode and including a photoelectric conversion layer that generates signal charges by photoelectric conversion; and a charge that is electrically connected to the second electrode and accumulates the signal charges. an accumulating portion, and an accumulating period, which is a period in which the signal charge is generated and accumulated, includes a first period and a second period, and the voltage supply circuit applies a first voltage during the first period. a second voltage different from the first voltage is supplied to the first electrode during the second period, and at least some of the plurality of pixels are accumulated in the charge accumulation unit; A signal corresponding to the amount of the signal charge is sequentially output during the first period in a non-destructive manner, and the plurality of pixels output the signal corresponding to the amount of the signal charge accumulated in the charge accumulation unit. They are sequentially output during the non-accumulation period after the accumulation period.

According to this, for example, the sensitivity of the pixel can be made different between the first period and the second period. In this specification, the sensitivity of a pixel means the photoelectric conversion efficiency of a photoelectric conversion unit, and is a concept including sensitivity to a plurality of wavelengths, that is, spectral sensitivity.

Compared to the second image based on the signal read out during the non-accumulation period, the first image based on the signal read out non-destructively during the first period has a short exposure time for accumulating the signal charges. It is difficult to saturate even a high-brightness subject. Further, by making the sensitivity of the pixels in the first period and the sensitivity of the pixels in the second period different from each other, the sensitivity of the first image and the sensitivity of the second image can be improved compared to the case where the sensitivity of the pixels in the accumulation period is constant. You can also make the difference larger. Therefore, for example, by synthesizing the first image and the second image, it is possible to obtain an image with a wider dynamic range than when the sensitivity of the pixels is constant during the accumulation period.

In addition, the difference in sensitivity between the first image and the second image can be made smaller than when the sensitivity of the pixels is constant during the accumulation period. Thereby, the sensitivity difference between the first image and the second image can be adjusted in a wide range according to the subject.

Further, for example, when the spectral sensitivity characteristic of the photoelectric conversion unit changes depending on the bias voltage, it is possible to obtain a plurality of images having different wavelength ranges of the captured light.

For example, the first period may precede the second period.

According to this, the signal charges accumulated at the time of non-destructive readout do not include the signal charges generated and accumulated during the second period. Therefore, for example, even if the intensity of light incident on the photoelectric conversion layer is such that it is saturated in the second period, an image before saturation can be obtained by nondestructive readout.

For example, the first period may be later than the second period.

According to this, the signal charges accumulated at the time of non-destructive readout include all the signal charges generated and accumulated during the second period. Therefore, an image obtained by nondestructive readout can include image information whose exposure time is the entire second period.

For example, at least some of the plurality of pixels may sequentially output a signal corresponding to the amount of the signal charge accumulated in the charge accumulation section during the second period in a non-destructive manner. .

According to this, in addition to the first image obtained by the nondestructive readout during the first period, the third image obtained by the nondestructive readout during the second period can also be obtained. The exposure amount of the third image is greater than the exposure amount of the first image and less than the exposure amount of the second image. In general, when expanding the dynamic range by combining images, a plurality of images with different exposure amounts are used. By obtaining the third image in addition to the first and second images, a sufficient amount of signal can be secured according to the amount of light of each subject, so that the image quality of the synthesized image can be improved.

For example, the first voltage may be less than the second voltage.

According to this, when the signal charge is a hole, for example, the sensitivity of the pixel in the first period can be made lower than the sensitivity of the pixel in the second period. Further, when the signal charges are electrons, for example, the sensitivity of the pixels in the first period can be made higher than the sensitivity of the pixels in the second period.

For example, the first voltage may be greater than the second voltage.

According to this, when the signal charge is a hole, for example, the sensitivity of the pixel in the first period can be made higher than the sensitivity of the pixel in the second period. Further, when the signal charges are electrons, for example, the sensitivity of the pixel in the first period can be made lower than the sensitivity of the pixel in the second period.

For example, the accumulation period may further include a third period, and the voltage supply circuit may supply a third voltage different from the first voltage and the second voltage to the first electrode during the third period. good.

According to this, the sensitivity of the pixel can be made different in the first period, the second period, and the third period. Further, for example, when nondestructive signal readout is performed in at least one of the second period and the third period, the number of images used for image synthesis can be increased. This makes it possible to more finely control the exposure amount of each image used for image synthesis. Further, when the spectral sensitivity characteristic of the photoelectric conversion unit changes depending on the bias voltage, it is possible to obtain more images in which the wavelength ranges of the captured light are different from each other. As a result, the wavelength range of the imaged light can be more finely controlled.

For example, the imaging device further includes a signal processing unit, the plurality of pixels are arranged in a matrix, and the signal processing unit processes the signal output non-destructively during the first period, A process of multiplying a coefficient according to the row to which the corresponding pixel belongs may be performed.

When non-destructive readout is sequentially performed on a row-by-row basis, exposure is started simultaneously for all pixels, whereas the readout timing differs depending on the row to which each pixel belongs. Therefore, the length of exposure time differs depending on the row to which each pixel belongs. Therefore, by multiplying the obtained signal by a coefficient corresponding to the row to which each pixel belongs, correction can be made so that the length of exposure time is the same for all pixels.

For example, at least some of the plurality of pixels perform an operation of sequentially outputting a signal corresponding to the amount of the signal charge accumulated in the charge accumulation portion in a non-destructive manner at least twice during the first period. You can go back and forth.

According to this, two images having different lengths of exposure time can be obtained by non-destructive readout. Further, by obtaining the difference between the two obtained images, it is possible to obtain an image in which the length of the exposure time is the same for all pixels. Furthermore, noise can be reduced by taking the difference between the two images obtained.

For example, only some pixels among the plurality of pixels may sequentially output a signal corresponding to the amount of the signal charge accumulated in the charge accumulation unit during the first period in a non-destructive manner. .

According to this, the time required for non-destructive reading can be shortened.

An imaging method according to an aspect of the present disclosure is an imaging method using a plurality of pixels each including a photoelectric conversion unit that generates signal charges by photoelectric conversion and a charge accumulation unit that accumulates the signal charges, An accumulation period, which is a period in which the signal charges are generated and accumulated, includes a first period and a second period, the sensitivities of the plurality of pixels in the first period are set to the first sensitivity, and the sensitivities in the second period are setting the sensitivities of the plurality of pixels to a second sensitivity different from the first sensitivity, and the signal accumulated in the charge accumulation unit from at least some of the plurality of pixels in the first period; A signal corresponding to the amount of charge is sequentially read in a non-destructive manner, and in a non-accumulation period after the accumulation period, signals corresponding to the amount of signal charge accumulated in the charge accumulation section are sequentially read out from the plurality of pixels. read out to

According to this, the first image including the subject image captured with the first sensitivity and the second image including both the subject image captured with the first sensitivity and the subject image captured with the second sensitivity are It can be obtained in one frame period. Moreover, compared to the case where the sensitivity of the pixels is constant during the accumulation period, the difference in sensitivity between the first image and the second image can be made larger. Therefore, for example, by synthesizing the first image and the second image, it is possible to obtain an image with a wider dynamic range than when the sensitivity of the pixels is constant during the accumulation period.

Moreover, when the wavelength range corresponding to the first sensitivity and the wavelength range corresponding to the second sensitivity are different, it is possible to obtain a plurality of images in which the wavelength ranges of the captured light are different from each other.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. It should be noted that the embodiments described below are all comprehensive or specific examples. Numerical values, shapes, materials, components, arrangement and connection forms of components, processing details, processing order, and the like shown in the following embodiments are examples, and are not intended to limit the present disclosure. The various aspects described herein are combinable with each other unless inconsistent. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in independent claims representing the highest concept will be described as optional constituent elements. In the following description, constituent elements having substantially the same functions are denoted by common reference numerals, and their description may be omitted.

Each figure is a schematic diagram and is not necessarily strictly illustrated. Therefore, for example, scales and the like do not necessarily match in each drawing.

(First embodiment)
[Configuration of imaging device]
FIG. 1 is a block diagram showing a configuration example of a camera system including an imaging device according to this embodiment. In FIG. 1 , the camera system 10 includes an optical system 60 , an imaging device 20 , a signal processing section 30 , a system controller 40 and a display section 50 .

The optical system 60 has a lens group and converges light input from the outside of the camera system 10 onto the imaging device 20 . The lens group may include a focus lens. The focus lens may adjust the focus position of the subject image in the imaging device 20 by moving in the optical axis direction of the light input from the outside.

The imaging device 20 receives light incident through the optical system 60 and outputs pixel signals. The imaging device 20 may be, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor. Details of the imaging device 20 will be described later.

The signal processing unit 30 processes signals input from the imaging device 20 . The signal processing unit 30 performs processing such as gamma correction, color interpolation processing, spatial interpolation processing, auto white balance, distance measurement calculation, and wavelength information separation, for example. The signal processing unit 30 can be implemented by, for example, a DSP (Digital Signal Processor).

A system controller 40 controls the entire camera system 10 . The system controller 40 can be realized by a microcomputer, for example.

The display unit 50 displays images generated by the signal processing unit 30 . The display unit 50 is, for example, a liquid crystal display or an organic EL display. The display unit 50 may have an input interface such as a touch panel. Thereby, the user can use the touch pen to select and control the processing content of the signal processing unit 30 and set the imaging conditions via the input interface.

FIG. 2 is a block diagram showing a configuration example of the imaging device 20 according to the first embodiment. The figure shows a circuit configuration example of the imaging device 20 when the imaging device 20 is a CMOS image sensor. As shown in FIG. 2, the imaging device 20 includes a plurality of pixels 101, a vertical scanning circuit 102, a horizontal scanning circuit 103, a current source 104, an AD conversion circuit 105, and a voltage supply circuit 111.

A plurality of pixels 101 are arranged in a matrix. Each of the plurality of pixels 101 generates signal charges according to incident light and outputs pixel signals according to the amount of signal charges.

The vertical scanning circuit 102 scans and drives the plurality of pixels 101 row by row via horizontal signal lines 107 provided for each row. In FIG. 2, only one horizontal signal line 107 is shown for each row for easy viewing. However, each row may include multiple horizontal signal lines 107, for example, to control the select transistors 24 and reset transistors 25 of the pixels 101, as will be described below.

Pixel signals output from the plurality of pixels 101 are input to the horizontal scanning circuit 103 via the vertical signal line 108 and the AD conversion circuit 105 provided for each column. The horizontal scanning circuit 103 sequentially outputs the input signals to the output signal line 109 .

A current source 104 is provided for each column and constitutes a source follower circuit together with an amplifying transistor in the pixel 101 .

The AD conversion circuit 105 is provided for each vertical signal line 108 and converts an analog pixel signal input from the vertical signal line 108 into a digital signal. The AD conversion circuit 105 may include a circuit that performs noise suppression signal processing typified by correlated double sampling.

The voltage supply circuit 111 supplies multiple different voltages to the multiple pixels 101 . By changing the voltage supplied to the pixel 101, the sensitivity of the pixel 101 can be changed. Each pixel 101 is connected to a power line 106 . A power supply voltage VDD is supplied to each pixel 101 through a power supply line 106 .

Note that the imaging apparatus 20 according to the present embodiment may be configured such that the pixel signal output from each pixel 101 is output from the horizontal scanning circuit 103 as an analog signal without providing the AD conversion circuit 105 . Further, the horizontal scanning circuit 103 may include a circuit for adding or subtracting the signals from each pixel 101 and output the operation result to the output signal line 109 .

FIG. 3 is a circuit diagram showing a configuration example of the pixel 101 in FIG. As shown in FIG. 3 , the pixel 101 includes a photoelectric converter 21 , a floating diffusion (hereinafter referred to as “FD”) 22 , an amplification transistor 23 , a selection transistor 24 and a reset transistor 25 . The photoelectric conversion unit 21 converts incident light into signal charges. The FD 22 accumulates signal charges generated by the photoelectric conversion section 21 . FD22 is an example of a charge storage unit.

The amplification transistor 23 has a gate connected to the FD 22 , a drain connected to the power supply line 106 to which the power supply voltage VDD is supplied, and a source connected to the drain of the selection transistor 24 . Thereby, the amplification transistor 23 forms a source follower circuit together with the current source 104 shown in FIG. 1 when the selection transistor 24 is in a conducting state. At this time, the source of the amplification transistor 23 outputs a signal corresponding to the amount of signal charge accumulated in the FD 22 to the vertical signal line 108 via the selection transistor 24 .

The selection transistor 24 has a drain connected to the source of the amplification transistor 213 , a source connected to the vertical signal line 108 , and a gate connected to a selection control signal line among the horizontal signal lines 107 . A selection control signal Vsel is supplied to the gate of the selection transistor 24 from a selection control signal line. The selection transistor 24 becomes conductive when the selection control signal Vsel is at high level, and outputs the pixel signal from the amplification transistor 23 to the vertical signal line 108 . Also, the selection transistor 24 becomes non-conductive when the selection control signal Vsel is at low level, and isolates the amplification transistor 23 from the vertical signal line 108 .

The reset transistor 25 has a drain supplied with a reset voltage VR, a source connected to the FD 22 , and a gate connected to a reset control signal line among the horizontal signal lines 107 . A reset control signal Vrst is supplied to the gate of the reset transistor 25 from a reset control signal line. The reset transistor 25 becomes conductive when the reset control signal Vrst is at high level, and resets the potential of the FD 22 to the reset voltage VR.

The pixel 101 outputs a pixel signal non-destructively without a reset operation. That is, the pixel 101 outputs a pixel signal corresponding to the amount of signal charge accumulated at that time without resetting the accumulated signal charge in the middle of the accumulation period. Such a read operation without reset operation is called non-destructive read. Non-destructive readout can also be performed multiple times within one frame period. After the accumulation period has elapsed, the pixel 101 outputs a pixel signal corresponding to the amount of signal charge accumulated during the entire accumulation period. After that, the accumulated signal charge is reset to the reset voltage VR, and the pixel 101 outputs a signal corresponding to the reset voltage VR. Such a read operation accompanied by a reset operation is called destructive read. In this specification, the accumulation period means a period during which signal charges are generated in the photoelectric conversion section 21 and accumulated in the charge accumulation section. On the other hand, the non-storage period substantially means a period during which signal charges are not newly accumulated in the charge accumulation section. Typically, the sensitivity of pixel 101 is set to substantially zero during non-integration periods.

FIG. 4 is a cross-sectional view schematically showing the structures of the photoelectric conversion section 21 and the FD 22 in FIG. As shown in FIG. 4, an insulating layer 101F and a photoelectric conversion section 21 are stacked on a semiconductor substrate 101D.

The photoelectric conversion section 21 includes a counter electrode 101A, a pixel electrode 101B, and a photoelectric conversion layer 101C located between the counter electrode 101A and the pixel electrode 101B.

The counter electrode 101A may be formed across multiple pixels 101 . 101 A of counter electrodes are formed using transparent conductive oxide (TCO:Transparent Conducting Oxide), such as ITO (Indium Tin Oxide), for example.

The pixel electrode 101B collects signal charges generated in the photoelectric conversion layer 101C. The pixel electrode 101B is connected to the FD 22 provided in the semiconductor substrate 101D through the contact plug 101E in the insulating layer 101F.

The photoelectric conversion layer 101C receives incident light and generates hole-electron pairs. As a material of the photoelectric conversion layer 101C, for example, a semiconducting inorganic material or a semiconducting organic material is used. The photoelectric conversion layer 101C is, for example, an organic photoelectric conversion film. In a state where a voltage is applied between the counter electrode 101A and the pixel electrode 101B to apply an electric field, one of the holes and electrons generated in the photoelectric conversion layer 101C is collected by the pixel electrode 101B and stored in the charge storage portion FD. accumulated.

The counter electrode 101 A is electrically connected to the voltage supply circuit 111 . The voltage supply circuit 111 is provided on the semiconductor substrate 111D. The voltage supply circuit 111 may be provided on a substrate different from the semiconductor substrate 101D. The voltage supply circuit 111 applies the sensitivity adjustment voltage VITO to the counter electrode 101A based on the control signal.

The FD 22 is, for example, a diffusion layer containing impurities, and accumulates signal charges collected by the pixel electrode 101B.

By changing the sensitivity adjustment voltage VITO applied to the counter electrode 101A, the sensitivity of the photoelectric conversion section 21 can be changed. For example, when the signal charges are holes, the sensitivity can be increased by setting the sensitivity adjustment voltage VITO to a relatively high positive voltage with reference to the voltage of the pixel electrode 101B. Further, the sensitivity can be lowered by setting the sensitivity adjustment voltage VITO to a relatively low positive voltage with reference to the potential of the pixel electrode 101B. Furthermore, by setting the sensitivity adjustment voltage VITO to a voltage lower than a predetermined threshold value, the sensitivity of the photoelectric conversion section 21 can be substantially zero. This threshold is hereinafter referred to as an exposure threshold.

By switching the sensitivity adjustment voltage VITO between a voltage higher than the exposure threshold and a voltage lower than the exposure threshold, the accumulation period can be freely set. Thereby, the imaging device 20 can implement a global shutter function that simultaneously starts and ends exposure for all pixels. The global shutter function is disclosed in Japanese Patent No. 6202512, for example. Japanese Patent No. 6202512 is incorporated herein by reference.

In this embodiment, the counter electrode 101A exemplifies the first electrode. The pixel electrode 101B exemplifies a second electrode.

Returning to FIG. 3 again, the description of the pixel 101 is continued. By turning on the reset transistor 25 with the reset control signal Vrst, the potential of the FD 22 is reset to the reset potential VR. The amplification transistor 23 outputs a signal corresponding to the amount of charge accumulated in the FD22. Whether or not to output the signal output from the amplification transistor 23 to the vertical signal line 108 is selected by switching the selection transistor 24 between the ON state and the OFF state using the selection control signal Vsel.

As long as the reset transistor 25 is not turned on, the pixel 101 can nondestructively and repeatedly output a signal corresponding to the amount of signal charge accumulated in the charge accumulation portion.

Details of the imaging operation performed by the imaging device 20 will be described below.

[First example of imaging operation of imaging device]
FIG. 5 is a timing chart showing a first imaging operation example. FIG. 5 shows, from top to bottom, the timing of the vertical synchronization signal VD, the temporal change of the sensitivity adjustment voltage VITO, and the timing of signal readout in each row of the plurality of pixels 101 arranged in a matrix. It is assumed that the plurality of pixels 101 are arranged in n rows from the first row to the n-th row. The sensitivity adjustment voltage VITO is a voltage applied to the counter electrode 101A. A solid line R0 schematically indicates a row in which normal signal readout is performed. A dashed line R1 schematically indicates a row in which signal readout is performed nondestructively. A first imaging operation example will be described below with reference to FIG.

First, at time t0, the sensitivity adjustment voltage VITO switches from V0 to V1. Thereby, the accumulation period Te is started. The accumulation period Te includes a first period Te1 and a second period Te2. In the first period Te1, the sensitivity adjustment voltage VITO is V1, and the sensitivities of the plurality of pixels 101 are set to the first sensitivity. That is, in the first period Te1, the plurality of pixels 101 generate and accumulate signal charges with the first sensitivity.

Next, at time t1, non-destructive signal readout is sequentially started for the plurality of pixels 101 row by row. At this time, the signals output by the plurality of pixels 101 are signals corresponding to the amount of signal charge accumulated in the charge accumulation unit from time t0 to the time when signal readout is performed.

Next, at time t2, the sensitivity adjustment voltage VITO switches from V1 to V2. Here, V2 is a voltage higher than V1. Therefore, the sensitivity of the plurality of pixels 101 in the second period Te2 is higher than the sensitivity in the first period Te1. Therefore, in the second period Te, the plurality of pixels 101 generate and accumulate signal charges with the second sensitivity higher than the first sensitivity in the first period Te1.

Next, at time t3, the sensitivity adjustment voltage VITO switches from V2 to V0. As a result, the accumulation period Te ends and the non-accumulation period Tr starts. Here, V0 is a voltage lower than V1, for example 0V. As a result, the sensitivities of the plurality of pixels 101 are substantially set to zero during the non-accumulation period Tr. It should be noted that other forms are possible as long as no signal charge is substantially generated and accumulated in the non-accumulation period Tr. For example, a separate mechanical shutter may be provided and closed in synchronization with the non-storage period Tr.

Next, at time t4 when the vertical synchronizing signal VD rises, signal readout is sequentially started for each row from the first row to the n-th row for the plurality of pixels 101 . The signal readout here is destructive readout. However, non-destructive reading may be used.

Next, at time t5, the sensitivity adjustment voltage VITO switches from V0 to V1 again, and the next accumulation period Te starts. After that, the above operation is repeated.

It should be noted that in the above-described example of the imaging operation, in the signal readout operation, the signals are read out sequentially for each row. However, a plurality of vertical signal lines 108 may be provided for each column, and the data may be read out sequentially for every plurality of rows. As a result, signal reading can be performed at high speed. Alternatively, signals may be collectively read from pixels 101 in a plurality of rows or columns at the same time. Such a reading method is also called pixel synthesis.

Further, in the above-described imaging operation example, non-destructive signal readout is performed during the accumulation period Te. Therefore, the length of the period (that is, the exposure time) from the time t0 at which the accumulation period Te starts to the time at which the non-destructive signal readout is performed differs depending on the row to which the pixel 101 belongs. Therefore, in order to correct the difference in exposure time between rows, the obtained signal may be multiplied by a correction coefficient corresponding to the row to which the pixel 101 belongs. Specifically, for example, the reciprocal of the exposure time of each row may be multiplied.

Further, in the above-described imaging operation example, the non-destructive signal readout may be performed only for at least some of the pixels 101 among the plurality of pixels 101 . For example, signal readout may be sequentially performed non-destructively for the pixels 101 in the even-numbered rows, and signal readout may not be performed for the pixels 101 in the odd-numbered rows. Further, when the image 101 for imaging each color of RGB is arranged in a Bayer array, for example, the pixels 101 in the row corresponding to the even-numbered unit pixel group from the top are sequentially non-destructively read out. However, the signal readout may not be performed for the pixels 101 in the row corresponding to the odd-numbered unit pixel group from the top. Alternatively, signal readout may be performed only for the pixels 101 in a specific area. As a result, nondestructive signal readout can be performed at high speed, and the difference in length of exposure time between rows can be reduced. Note that the resolution of an image obtained by non-destructive signal readout only for some pixels 101 is lower than the resolution of an image obtained by normal signal readout for all pixels. However, even if the resolutions are different, it is possible to synthesize these images.

According to this imaging operation example, an image with a short exposure time can be obtained by non-destructive signal readout R1. Furthermore, the sensitivity of the pixel 101 in the first period is set low. Therefore, in addition to a short exposure time, an image is captured with low sensitivity, so even a high-brightness subject can be captured without saturation. Further, according to this imaging operation example, an image with a long exposure time can be obtained by normal signal readout R0. Furthermore, the sensitivity of the pixel 101 in the second period is set higher than in the first period. Therefore, in addition to a long exposure time, an image is captured with high sensitivity, so even a low-brightness subject can be captured without blackening. Therefore, for example, by synthesizing an image obtained by nondestructive signal readout and an image obtained by normal signal readout, an image with a wide dynamic range can be obtained.

[Second imaging operation example of imaging device]
FIG. 6 is a timing chart showing a second imaging operation example. This imaging operation example differs from the first imaging operation example in that non-destructive signal readout is performed at least twice in the first period Te1. In the following, the different points will be mainly described.

In FIG. 6, the dashed line R2 schematically indicates a row in which non-destructive signal readout is performed, like the dashed line R1. In this imaging operation example, the plurality of pixels 101 performs non-destructive signal readout twice following the first period Te1. Thereby, a plurality of images with different exposure times can be obtained.

Alternatively, the difference between the two signals obtained by nondestructive readout during the first period Te1 may be taken. Specifically, the signal processing unit 30 or the AD conversion circuit 105 may obtain the difference between the signal obtained by the nondestructive signal readout R2 and the signal obtained by the nondestructive signal readout R1. . This makes it possible to equalize the exposure times of the plurality of pixels 101 regardless of the row to which the pixels 101 belong. Therefore, the above-described correction according to the row to which the pixel 101 belongs becomes unnecessary. Furthermore, fixed pattern noise can also be removed by taking the difference. Therefore, a high-quality image with reduced noise can be obtained. Further, as in the first imaging operation example, for example, an image corresponding to the difference between the signals obtained by two nondestructive readouts and an image corresponding to the signal obtained by normal signal readout may be synthesized. Therefore, an image with a wide dynamic range can be obtained.

In this imaging operation example, non-destructive signal readout is performed twice in the first period Te, but it may be performed three times or more. Also, a plurality of images may be acquired by nondestructive readout by taking the difference between the signals by these nondestructive readouts.

[Third Imaging Operation Example of Imaging Apparatus]
FIG. 7 is a timing chart showing a third imaging operation example. This imaging operation example differs from the first imaging operation example in that the accumulation period Te includes a third period Te3 in addition to the first period Te1 and the second period Te2. Further, this imaging operation example differs from the first imaging operation example in that non-destructive signal readout is performed also in the second period Te2 and the third period Te3. In the following, the different points will be mainly described.

In FIG. 7, the accumulation period Te further includes a third period Te3. Also, in the third period Te3, the sensitivity adjustment voltage VITO is set to V3. Here, V3 is a voltage higher than V2. Therefore, the sensitivity of the plurality of pixels 101 in the third period Te3 is higher than the sensitivity in the second period Te2. Therefore, in the third period Te, the plurality of pixels 101 generate and accumulate signal charges with the third sensitivity higher than the second sensitivity in the second period Te2.

Further, in the second period Te, the signal readout R2 is sequentially performed on the plurality of pixels 101 row by row in a non-destructive manner. At this time, the signals output by the plurality of pixels 101 are signals corresponding to the amount of signal charge accumulated in the charge accumulation unit from time t0 to the time when signal readout is performed. Similarly, in the third period Te, signal readout R3 is sequentially performed on the plurality of pixels 101 row by row in a non-destructive manner. At this time, the signals output by the plurality of pixels 101 are signals corresponding to the amount of signal charge accumulated in the charge accumulation unit from time t0 to the time when signal readout is performed.

According to this imaging operation example, in addition to an image obtained by nondestructive signal readout R1, an image obtained by nondestructive signal readout R2 and an image obtained by nondestructive signal readout R3 can be obtained. These images differ in sensitivity as well as exposure time. Therefore, an image with a wide dynamic range can be obtained by synthesizing these images with an image obtained by normal signal readout R0. Also, by increasing the number of images used for synthesis, it is possible to secure a sufficient amount of signal according to the amount of light of each subject, so that the image quality of the synthesized image can be improved.

For each of the nondestructive signal readouts R1, R2, and R3, arithmetic processing may be performed according to the row to which the pixel 101 belongs in order to correct the exposure time difference for each row to which the pixel 101 belongs.

Further, in this imaging operation example, as in the second imaging operation example, non-destructive signal readout is performed twice in each of the first period Te1, the second period Te2, and the third period Te3, and the difference may be taken. Alternatively, image synthesis may be performed using an image based on the difference.

(Second embodiment)
The imaging device according to this embodiment is the same as the imaging device 20 according to the first embodiment except for the photoelectric conversion layer 101C. In the following, the different points will be mainly described.

The photoelectric conversion layer 101C according to this embodiment includes a first photoelectric conversion layer and a second photoelectric conversion layer having different spectral sensitivity characteristics. The first photoelectric conversion layer has sensitivity in the visible light wavelength range when a bias voltage greater than the first bias voltage is applied. The second photoelectric conversion layer has sensitivity in the wavelength range of infrared light when a bias voltage higher than the second bias voltage is applied. Here, it is assumed that the second bias voltage is higher than the first bias voltage. At this time, when a bias voltage higher than the first bias voltage and lower than the second bias voltage is applied, the photoelectric conversion layer 101C has sensitivity in the visible light wavelength range. Further, when a bias voltage higher than the second bias voltage is applied, the photoelectric conversion layer 101C has sensitivity in the wavelength range of visible light and infrared light.

FIG. 8 is a diagram showing an example of spectral sensitivity characteristics of the photoelectric conversion layer 101C. In (a) and (b) of FIG. 8, the horizontal axis indicates the wavelength, and the vertical axis indicates the intensity of the absorption spectrum. FIG. 8A shows an example of spectral sensitivity characteristics of the photoelectric conversion layer 101C when the bias voltage between the counter electrode 101A and the pixel electrode 101B is higher than the first bias and lower than the second bias voltage. be. (b) of FIG. 8 is an example of spectral sensitivity characteristics of the photoelectric conversion layer 101C when the bias voltage between the counter electrode 101A and the pixel electrode 101B is higher than the second bias voltage. A technique for changing spectral sensitivity characteristics by bias voltage is disclosed in detail in International Publication WO2018/025544. This International Publication is incorporated herein by reference.

Next, an example of imaging operation in the imaging apparatus according to the second embodiment will be described.

FIG. 9 is a timing chart showing an example of imaging operation in the imaging apparatus according to this embodiment.

In the imaging operation example of the present embodiment, the wavelength range to which the photoelectric conversion unit 21 is sensitive is made different between the first period Te1 and the second period Te2. Specifically, in the first period Te1, the sensitivity adjustment voltage VITO is set to V1 so that a bias voltage higher than the first bias voltage and lower than the second bias voltage is applied to the photoelectric conversion layer 101C. set to At this time, the plurality of pixels 101 have sensitivity in the wavelength range of visible light. That is, in the first period Te1, the plurality of pixels 101 absorb light in the wavelength range of visible light to generate and accumulate signal charges. Further, in the first period Te1, signal readout is sequentially performed for each row in a non-destructive manner with respect to the plurality of pixels 101 . At this time, the signals output by the plurality of pixels 101 are signals corresponding to the amount of signal charge accumulated in the charge accumulation unit from the start of the accumulation period Te to the time of signal readout. Therefore, this signal is a signal corresponding to light in the wavelength range of visible light.

Next, in the second period Te2, the sensitivity adjustment voltage VITO is set to V2 so that a bias voltage higher than the above-described second bias voltage is applied to the photoelectric conversion layer 101C. At this time, the plurality of pixels 101 has sensitivity to the wavelength ranges of visible light and infrared light. That is, in the second period Te2, the plurality of pixels 101 absorb light in the wavelength range of visible light and infrared light to generate and accumulate signal charges.

Next, in the non-accumulation period Tr, normal signal readout is sequentially performed for each row of the plurality of pixels 101 . At this time, the signals output by the plurality of pixels 101 are signals corresponding to the amount of signal charges generated and accumulated during the accumulation period Te. Therefore, this signal is a signal corresponding to light in the wavelength range of visible light and infrared light.

According to this embodiment, an image obtained by imaging light in the visible light wavelength range is obtained by non-destructive signal readout R1. Further, an image obtained by imaging light in the wavelength range of visible light and infrared light is obtained by normal signal readout R0. That is, it is possible to obtain a plurality of images in which the wavelength ranges of the captured light are different from each other in one frame period.

(Third embodiment)
The imaging device according to this embodiment is the same as the imaging device 20 according to the first embodiment. However, the sensitivity adjustment voltage VITO and the non-destructive signal readout timing are different from those in the first embodiment. In the following, the different points will be mainly described.

FIG. 10 is a timing chart showing an example of imaging operation in the imaging apparatus according to this embodiment. In the imaging operation example of the present embodiment, the sensitivity adjustment voltage VITO is set to V2 in the second period Te2, and the sensitivity adjustment voltage VITO is set to V1, which is lower than V2, in the first period Te1. Further, nondestructive signal readout is performed in the first period. As described above, the present embodiment differs from the first embodiment in that the first period Te1 in which non-destructive signal readout is performed is set after the second period Te2.

According to the present embodiment, for example, when an object in motion is captured, it is possible to obtain an image of the object with little blurring and an image of the object with a moving trajectory and a sense of dynamism. Specifically, the signal obtained by the nondestructive signal readout R1 corresponds to the amount of signal charge generated and accumulated from the start of the second period Te2 to the time when the signal readout is performed. Here, since the sensitivity of the plurality of pixels 101 in the first period Te1 is set low, the influence of the signal charges generated and accumulated in the first period Te1 is small. Therefore, the signal obtained by the nondestructive signal readout R1 mainly corresponds to the amount of signal charge accumulated in the second period Te2. Therefore, by setting the length of the second period Te2 to be relatively short, it is possible to obtain an image of the subject with little blur by the non-destructive signal readout R1.

On the other hand, the signal obtained by normal signal readout R0 corresponds to the amount of signal charges generated and accumulated in the second period Te2 and the first period Te2. Therefore, an image including a subject image with little blur corresponding to the second period Te2 and a subject image with relatively large blur corresponding to the first period Te1 can be obtained by the normal signal readout R0. Note that the sensitivity of the plurality of pixels 101 in the first period Te1 is set to be lower than the sensitivity in the second period Te2, so the subject image with large blurring has low luminance. As a result, a dynamic subject image with a moving locus is obtained.

FIG. 11 is a diagram showing an example of an image captured by the imaging device according to this embodiment. FIG. 11(a) shows an image d1 obtained by nondestructive signal readout R1. FIG. 11(b) shows an image d2 obtained by normal signal readout R0. The image d1 includes a subject image with a small blur of the moving object. The image d2 includes, in addition to the subject image with little blurring, a dynamic subject image to which a movement trajectory with low luminance is given. As described above, according to the present embodiment, for example, when capturing an image of a moving subject, it is possible to obtain an image of the subject with little blurring and an image of the subject with a sense of dynamism to which a moving trajectory is added. .

Note that the length of the second period Te2 may be longer than the length of the first period Te1. Also, the sensitivity adjustment voltage VITO in the second period Te2 may be lower than the sensitivity adjustment voltage VITO in the first period Te1. A plurality of images including subject images captured with different sensitivities can also be obtained by each of these modifications.

The imaging device according to the present disclosure is useful as various imaging devices. It can also be applied to applications such as digital cameras, digital video cameras, mobile phones with cameras, medical cameras such as electronic endoscopes, in-vehicle cameras, and robot cameras.

10 camera system 20 imaging device 22 FD
23 amplification transistor 24 selection transistor 25 reset transistor 30 signal processing unit 40 system controller 50 display unit 60 optical system 101 pixel 102 vertical scanning circuit 101A counter electrode 101B pixel electrode 101C photoelectric conversion layer 101D semiconductor substrate 101E contact plug 103 horizontal scanning circuit 104 current Source 105 AD conversion circuit 106 Power line 107 Horizontal signal line 108 Vertical signal line 109 Output signal line

Claims (11)

a plurality of pixels capable of non-destructive readout;
a voltage supply circuit;
with
each of the plurality of pixels,
a photoelectric conversion portion including a first electrode, a second electrode, and a photoelectric conversion layer positioned between the first electrode and the second electrode for generating a signal charge by photoelectric conversion;
a charge storage unit electrically connected to the second electrode and configured to store the signal charge;
including
an accumulation period, which is a period in which the signal charge is generated and accumulated, includes a first period and a second period;
the voltage supply circuit supplies a first voltage to the first electrode during the first period, and supplies a second voltage different from the first voltage to the first electrode during the second period;
at least some of the plurality of pixels sequentially output a signal corresponding to the amount of the signal charge accumulated in the charge accumulation unit during the first period in a non-destructive manner;
The plurality of pixels sequentially output a signal corresponding to the amount of the signal charge accumulated in the charge accumulation unit during a non-accumulation period after the accumulation period.
Imaging device. The first period is before the second period,
The imaging device according to claim 1 . The first period is later than the second period,
The imaging device according to claim 1 . At least some of the plurality of pixels sequentially output a signal corresponding to the amount of the signal charge accumulated in the charge accumulation unit during the second period in a non-destructive manner.
The imaging device according to any one of claims 1 to 3. the first voltage is less than the second voltage;
The imaging device according to any one of claims 1 to 4. the first voltage is greater than the second voltage;
The imaging device according to any one of claims 1 to 4. the accumulation period further includes a third period,
wherein the voltage supply circuit supplies a third voltage different from the first voltage and the second voltage to the first electrode during the third period;
The imaging device according to any one of claims 1 to 6. further equipped with a signal processing unit,
The plurality of pixels are arranged in a matrix,
The signal processing unit multiplies the signal output in a non-destructive manner during the first period by a coefficient corresponding to the row to which the corresponding pixel belongs,
The imaging device according to any one of claims 1 to 7. At least some of the plurality of pixels perform an operation of sequentially outputting a signal corresponding to the amount of the signal charge accumulated in the charge accumulation portion in a non-destructive manner at least twice during the first period. ,
The imaging device according to any one of claims 1 to 8. Only some of the plurality of pixels sequentially output a signal corresponding to the amount of the signal charge accumulated in the charge accumulation unit during the first period in a non-destructive manner;
The imaging device according to any one of claims 1 to 9. An imaging method using a plurality of pixels each including a photoelectric conversion unit that generates signal charges by photoelectric conversion and a charge storage unit that stores the signal charges,
an accumulation period, which is a period in which the signal charge is generated and accumulated, includes a first period and a second period;
setting the sensitivity of the plurality of pixels in the first period to a first sensitivity;
setting the sensitivity of the plurality of pixels in the second period to a second sensitivity different from the first sensitivity;
In the first period, signals corresponding to the amount of the signal charge accumulated in the charge accumulation unit are sequentially and nondestructively read out from at least some of the plurality of pixels,
In a non-accumulation period after the accumulation period, signals corresponding to the amount of signal charges accumulated in the charge accumulation unit are sequentially read out from the plurality of pixels;
Imaging method.

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