WO2018124057A1 - Imaging device and control method therefor - Google Patents

Abstract

This imaging device (100) is provided with: an imaging element (101) which can be non-destructively read; and a correction unit (105) which uses non-destructive reading, and generates a corrected image using a plurality of images obtained by the imaging element (101) as a result of one exposure. The correction unit (105) may acquire the plurality of images using non-destructive reading after exposure is stopped. The correction unit (105) may generate the corrected image by averaging the plurality of images.

Description

Imaging apparatus and control method thereof

The present disclosure relates to an imaging apparatus and a control method thereof.

A technique described in Patent Document 1 is known as an image sensor using an organic photoelectric conversion element.

JP 2008-042180 A

In the imaging apparatus, processing for reducing random noise is performed. Specifically, the imaging device captures a plurality of images continuously and calculates an average of the obtained plurality of images to obtain a corrected image.

However, this method has a problem that the image quality of a moving image is deteriorated because shooting times of a plurality of images are strictly different.

Therefore, an object of the present disclosure is to provide an imaging apparatus or a control method thereof that can suppress a decrease in image quality.

An imaging apparatus according to one embodiment of the present disclosure uses a non-destructive readout image sensor and a non-destructive readout to obtain a corrected image using a plurality of images obtained by the imaging device by one exposure. A correction unit to be generated.

The present disclosure can provide an imaging apparatus or a control method thereof that can suppress a decrease in image quality.

FIG. 1 is a block diagram of an imaging apparatus according to an embodiment. FIG. 2A is a diagram illustrating an appearance example of the imaging apparatus according to the embodiment. FIG. 2B is a diagram illustrating an appearance example of the imaging apparatus according to the embodiment. FIG. 3 is a diagram illustrating a configuration of the image sensor according to the embodiment. FIG. 4 is a circuit diagram illustrating a configuration of a pixel according to the embodiment. FIG. 5 is a flowchart illustrating the operation of the imaging apparatus according to the embodiment. FIG. 6 is a diagram illustrating the operation of the imaging apparatus according to the embodiment. FIG. 7 is a diagram illustrating a modified example of the operation of the imaging apparatus according to the embodiment.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Each of the embodiments described below shows a preferred specific example of the present disclosure. Therefore, the numerical values, shapes, materials, components, component arrangement positions, connection forms, and the like shown in the following embodiments are merely examples, and are not intended to limit the present disclosure. Therefore, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept of the present disclosure are described as arbitrary constituent elements.

Each figure is a schematic diagram and is not necessarily shown strictly. Moreover, in each figure, the same code | symbol is attached | subjected to the substantially same structure, The overlapping description is abbreviate | omitted or simplified.

(Embodiment)
[Configuration of imaging device]
First, the configuration of the imaging device according to the embodiment of the present disclosure will be described. FIG. 1 is a block diagram illustrating a configuration of an imaging apparatus 100 according to the present embodiment. 2A and 2B are diagrams illustrating an example of the appearance of the imaging apparatus 100. FIG. For example, as illustrated in FIGS. 2A and 2B, the imaging apparatus 100 is a camera such as a digital still camera or a digital video camera.

1 includes an imaging element 101, a control unit 102, a display unit 103, and a storage unit 104. The imaging device 101 is a solid-state imaging device (solid-state imaging device) that converts incident light into an electrical signal (image) and outputs the obtained electrical signal. For example, the imaging device 101 is an organic sensor using an organic photoelectric conversion device.

The control unit 102 controls the image sensor 101. In addition, the control unit 102 performs various signal processing on the image obtained by the imaging element 101, and displays the obtained image on the display unit 103 or stores it in the storage unit 104. Note that the image output from the control unit 102 may be output to the outside of the imaging apparatus 100 via an input / output interface (not shown).

In addition, the control unit 102 includes a correction unit 105 that corrects an image obtained by the image sensor 101.

[Configuration of image sensor]
Next, the configuration of the image sensor 101 will be described. FIG. 3 is a block diagram illustrating a configuration of the image sensor 101.

3 includes a plurality of pixels (unit pixel cells) 201 arranged in a matrix, a vertical scanning unit 202, a column signal processing unit 203, a horizontal readout unit 204, and a row. A plurality of reset control lines 205, a plurality of address control lines 206 provided for each row, a plurality of vertical signal lines 207 provided for each column, and a horizontal output terminal 208.

Each of the plurality of pixels 201 outputs a signal corresponding to the incident light to the vertical signal line 207 provided in the corresponding column.

The vertical scanning unit 202 resets the plurality of pixels 201 via the plurality of reset control lines 205. The vertical scanning unit 202 sequentially selects the plurality of pixels 201 in units of rows via the plurality of address control lines 206.

The column signal processing unit 203 performs signal processing on the signals output to the plurality of vertical signal lines 207, and outputs the plurality of signals obtained by the signal processing to the horizontal reading unit 204. For example, the column signal processing unit 203 performs noise suppression signal processing represented by correlated double sampling, analog / digital conversion processing, and the like.

The horizontal readout unit 204 sequentially outputs a plurality of signals after the signal processing by the plurality of column signal processing units 203 to the horizontal output terminal 208.

Hereinafter, the configuration of the pixel 201 will be described. FIG. 4 is a circuit diagram illustrating a configuration of the pixel 201.

As shown in FIG. 4, the pixel 201 includes a photoelectric conversion unit 211, a charge storage unit 212, a reset transistor 213, an amplification transistor 214 (source follower transistor), and a selection transistor 215.

The photoelectric conversion unit 211 generates signal charges by photoelectrically converting incident light. A voltage Voe is applied to one end of the photoelectric conversion unit 211. Specifically, the photoelectric conversion unit 211 includes a photoelectric conversion layer made of an organic material. The photoelectric conversion layer may include a layer made of an organic material and a layer made of an inorganic material.

The charge storage unit 212 is connected to the photoelectric conversion unit 211 and stores the signal charge generated by the photoelectric conversion unit 211. Note that the charge storage unit 212 may be configured with a parasitic capacitance such as a wiring capacitance instead of a dedicated capacitance element.

The reset transistor 213 is used to reset the potential of the signal charge. The gate of the reset transistor 213 is connected to the reset control line 205, the source is connected to the charge storage unit 212, and the reset voltage Vreset is applied to the drain.

Note that the definitions of drain and source generally depend on circuit operation, and are often not specified from the element structure. In this embodiment, for convenience, one of the source and the drain is referred to as a source and the other of the source and the drain is referred to as a drain. However, in this embodiment, the drain may be replaced with the source and the source may be replaced with the drain.

The amplification transistor 214 amplifies the voltage of the charge storage unit 212 and outputs a signal corresponding to the voltage to the vertical signal line 207. The gate of the amplification transistor 214 is connected to the charge storage unit 212, and the power supply voltage Vdd or the ground voltage Vss is applied to the drain.

The selection transistor 215 is connected in series with the amplification transistor 214, and switches whether to output the signal amplified by the amplification transistor 214 to the vertical signal line 207. The selection transistor 215 has a gate connected to the address control line 206, a drain connected to the source of the amplification transistor 214, and a source connected to the vertical signal line 207.

Further, for example, the voltage Voe, the reset voltage Vreset, and the power supply voltage Vdd are voltages commonly used in all the pixels 201.

The characteristics of the organic sensor include non-destructive readout and electronic ND (Neutral Density) control. Non-destructive reading is a process of reading image data during an exposure period and continuing exposure. In conventional readout (hereinafter referred to as destructive readout), it is necessary to end exposure when performing readout. That is, only one image could be obtained by one exposure. On the other hand, by using nondestructive reading, it is possible to read the image data exposed up to that time during the exposure period and continue the exposure. Thereby, a plurality of images having different exposure times can be obtained by one exposure.

The electronic ND control is a process for electrically controlling the transmittance of the image sensor. Here, the transmittance means the proportion of light that is converted into an electrical signal in the incident light. That is, by setting the transmittance to 0%, it is possible to electrically shield the light. Specifically, the transmittance is controlled by controlling the voltage Voe shown in FIG. Thereby, exposure can be electrically terminated without using a mechanical shutter.

Note that the image sensor 101 includes a mechanical shutter and may use both electronic ND control and light shielding by the mechanical shutter, or may use light shielding by the mechanical shutter without using the electronic ND control.

In addition, here, an example in which the image sensor 101 is an organic sensor will be described. However, the image sensor 101 only needs to realize nondestructive reading or electronic ND control, and may be other than an organic sensor. That is, the photoelectric conversion layer included in the photoelectric conversion unit 211 may be made of an inorganic material. For example, the photoelectric conversion layer may be made of amorphous silicon or chalcopyrite semiconductor.

[Operation of imaging device]
Next, the operation of the imaging apparatus 100 according to the present embodiment will be described. FIG. 5 is a flowchart showing an operation flow of the imaging apparatus 100. FIG. 6 is a diagram for explaining the operation of the imaging apparatus 100.

As shown in FIG. 5, the imaging apparatus 100 first performs exposure (S101). Specifically, after the exposure is started, the exposure is terminated by performing light shielding by the above-described electronic ND control or the mechanical shutter.

Next, the imaging apparatus 100 performs nondestructive reading a predetermined number of times (S102), and then generates an image by performing destructive reading (S103).

Next, the imaging apparatus 100 generates a corrected image in which random noise is reduced using the plurality of images obtained in steps S102 and S103 (S104). Here, reducing the random noise means reducing the increase / decrease in the luminance value caused by the random noise included in each pixel. Specifically, the imaging apparatus 100 generates a corrected image by averaging the obtained plurality of images.

Here, the random noise is, for example, noise generated in the signal readout path, and the position (pixel) where the noise is generated and the strength of the noise are random. Therefore, since random noise cannot be grasped in advance, correction cannot be performed based on the amount of noise grasped in advance. On the other hand, by performing the averaging of a plurality of images, the pixel values of pixels in which random noise is generated can be averaged with the pixel values of normal pixels in other images, so that the influence of random noise can be reduced. .

Note that the imaging apparatus 100 may determine the presence or absence of noise in each pixel included in each of a plurality of images, and generate a corrected image using pixels without noise, instead of addition averaging. Note that the presence of noise means that there is more noise than a predetermined value, and that there is no noise means that the noise is less than a predetermined value.

The pixel value of a pixel in which random noise is generated is a value that is distant from the pixel value of the pixel at the same position in another plurality of images. Therefore, the imaging apparatus 100 determines whether or not random noise is generated in each pixel of each image based on the variation in the pixel value of each pixel between images, and a pixel in which random noise is not generated. May be combined to generate a correction image.

Specifically, the imaging device 100 calculates, for each pixel, an average value of the pixel values of the pixels included in the plurality of images, and randomly selects a pixel having a value separated from the average value by a predetermined value or more. It is determined that the pixel is generated, and other pixels are determined as normal pixels without random noise. Next, the imaging apparatus 100 generates a corrected image by combining normal pixels. For example, the imaging apparatus 100 may use the average value of the pixel values of normal pixels as the pixel value of the pixel of the corrected image, or use one of the pixel values of the normal pixel of the corrected image. You may use as a pixel value of the pixel concerned.

Alternatively, the imaging apparatus 100 uses the image obtained by destructive readout as a basic image, and calculates the pixel value or average of the pixels in which noise included in the basic image is generated by nondestructive readout. It may be replaced with a value. Here, in general, in non-destructive reading, some processing such as noise removal processing performed at the time of destructive reading is not performed. That is, an image obtained by destructive readout has higher image quality than an image obtained by nondestructive readout. Therefore, the image quality of the correction image can be improved by using the image obtained by destructive readout as the basic image.

Although an example in which nondestructive reading is performed after the exposure period ends is described here, nondestructive reading may be performed during the exposure period as shown in FIG.

Further, the number of nondestructive readings is arbitrary and is not limited to the number shown in FIGS. Further, destructive reading may not be performed.

As described above, the imaging apparatus 100 according to the present embodiment uses the imaging element 101 capable of non-destructive readout and the non-destructive readout to obtain a plurality of images obtained by the imaging element by one exposure. And a correction unit 105 that generates a corrected image with reduced random noise.

Thereby, since the imaging apparatus 100 can use a plurality of images obtained by single exposure using nondestructive readout, it is possible to suppress deterioration in image quality (for example, subject blur) in a moving image. In addition, since a plurality of images can be obtained by a single exposure, the photographing time can be shortened compared to a case where a plurality of exposures are performed.

Further, the correction unit 105 acquires a plurality of images using nondestructive reading after stopping the exposure. Thereby, since the imaging device 100 can use a plurality of images obtained with the same exposure time, it is possible to further suppress deterioration in image quality in a moving image.

An imaging apparatus 100 according to an aspect of the present disclosure uses an imaging element 101 capable of nondestructive readout and a plurality of images obtained by the imaging element 101 by a single exposure using nondestructive readout. And a correction unit 105 that generates an image.

According to this, since a plurality of images obtained by a single exposure using nondestructive readout can be used, it is possible to suppress a decrease in image quality in a moving image.

For example, the correction unit 105 may acquire a plurality of images using nondestructive reading after stopping the exposure.

According to this, since a plurality of images obtained with the same exposure time can be used, it is possible to suppress a decrease in image quality in a moving image.

For example, the correction unit 105 may generate a corrected image by averaging a plurality of images.

For example, the correction unit 105 may determine the presence or absence of noise in each pixel included in each of the plurality of images, and generate a corrected image using pixels without noise.

For example, the correction unit 105 may generate a corrected image using a plurality of images and an image acquired by destructive reading.

For example, the image sensor 101 may be an organic sensor.

The control method according to an aspect of the present disclosure is a control method of the imaging apparatus 100 including the imaging element 101 capable of nondestructive readout, and is obtained by the imaging element 101 by one exposure using nondestructive readout. And a correction step (S104) for generating a corrected image using the plurality of images.

According to this, since a plurality of images obtained by a single exposure using nondestructive readout can be used, it is possible to suppress a decrease in image quality in a moving image.

Note that these comprehensive or specific modes may be realized by a system, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable CD-ROM, and the system, method, integrated circuit, and computer program. Also, any combination of recording media may be realized.

The imaging device according to the embodiment of the present disclosure has been described above, but the present disclosure is not limited to this embodiment.

For example, each processing unit included in the imaging apparatus according to the above embodiment is typically realized as an LSI that is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them.

Further, the integration of circuits is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

Further, in each of the above embodiments, each component may be configured by dedicated hardware or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

Also, the present disclosure may be realized as a control method executed by the imaging apparatus.

The circuit configuration shown in the circuit diagram is an example, and the present disclosure is not limited to the circuit configuration. That is, similar to the circuit configuration described above, a circuit that can realize the characteristic function of the present disclosure is also included in the present disclosure. Moreover, all the numbers used above are illustrated for specifically explaining the present disclosure, and the present disclosure is not limited to the illustrated numbers.

In addition, division of functional blocks in the block diagram is an example, and a plurality of functional blocks can be realized as one functional block, a single functional block can be divided into a plurality of functions, or some functions can be transferred to other functional blocks. May be. In addition, functions of a plurality of functional blocks having similar functions may be processed in parallel or time-division by a single hardware or software.

In addition, the order in which the steps in the flowchart are executed is for illustration in order to specifically describe the present disclosure, and may be in an order other than the above. Also, some of the above steps may be executed simultaneously (in parallel) with other steps.

As described above, the imaging device according to one or more aspects has been described based on the embodiment, but the present disclosure is not limited to this embodiment. Unless it deviates from the gist of the present disclosure, various modifications conceived by those skilled in the art have been made in this embodiment, and forms constructed by combining components in different embodiments are also within the scope of one or more aspects. May be included.

The present disclosure can be applied to an imaging apparatus such as a digital still camera or a digital video camera.

DESCRIPTION OF SYMBOLS 100 Imaging device 101 Image pick-up element 102 Control part 103 Display part 104 Memory | storage part 105 Correction | amendment part 201 Pixel 202 Vertical scanning part 203 Column signal processing part 204 Horizontal read-out part 205 Reset control line 206 Address control line 207 Vertical signal line 208 Horizontal output terminal 211 Photoelectric conversion unit 212 Charge storage unit 213 Reset transistor 214 Amplification transistor 215 Selection transistor

Claims (7)

An image sensor capable of non-destructive readout;
An image pickup apparatus comprising: a correction unit that generates a corrected image using a plurality of images obtained by the image pickup device by one exposure using nondestructive readout. The imaging device according to claim 1, wherein the correction unit acquires the plurality of images using the non-destructive readout after stopping exposure. The imaging apparatus according to claim 1, wherein the correction unit generates the corrected image by averaging the plurality of images. The imaging device according to claim 1, wherein the correction unit determines the presence or absence of noise in each pixel included in each of the plurality of images, and generates the corrected image using pixels without noise. The imaging apparatus according to claim 1, wherein the correction unit generates the corrected image using the plurality of images and an image acquired by destructive readout. The imaging device according to any one of claims 1 to 5, wherein the imaging element is an organic sensor. A method for controlling an imaging apparatus including an imaging element capable of nondestructive readout,
A control method including a correction step of generating a corrected image using a plurality of images obtained by the imaging device by one exposure using non-destructive readout.

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