JP6748979B2 - Imaging device and control method thereof - Google Patents

Description

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

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

JP, 2008-042180, A

In the image pickup apparatus, processing for correcting a change in black level due to dark current is performed. Specifically, the imaging device reduces the influence of dark current by subtracting the light-shielded image captured in the light-shielded state from the main image.

However, the dark current amount may change due to, for example, a temperature change between when the main image is captured and when the light-shielded image is captured. In this case, the effect of dark current cannot be completely eliminated by the above correction.

Therefore, it is an object of the present disclosure to provide an imaging device or a control method thereof that can reduce the influence of the dark current amount.

An imaging device according to an aspect of the present disclosure includes an imaging device capable of nondestructive readout, an imaging system that collects light on the imaging device, a light blocking unit that blocks light of the imaging system, and the imaging device. A correction unit that generates a corrected image by subtracting the correction image from the obtained main image, the correction unit being obtained by the image pickup device by one exposure in a light-shielded state, and the exposure times are different from each other. A plurality of light-shielded images is acquired using nondestructive readout, and the correction image is generated using at least one of the plurality of light-shielded images.

The present disclosure can provide an imaging device or a control method thereof that can reduce the influence of the dark current amount.

FIG. 1 is a block diagram of the image pickup apparatus according to the first embodiment. FIG. 2A is a diagram illustrating an external appearance example of the image pickup apparatus according to the first embodiment. FIG. 2B is a diagram illustrating an external appearance example of the image pickup apparatus according to the first embodiment. FIG. 3 is a diagram showing the configuration of the image sensor according to the first embodiment. FIG. 4 is a circuit diagram showing the configuration of the pixel according to the first embodiment. FIG. 5 is a flowchart showing the operation of the image pickup apparatus according to the first embodiment. FIG. 6 is a diagram showing the operation of the imaging device according to the first embodiment. FIG. 7 is a diagram showing an example of a main image according to the first embodiment. FIG. 8 is a diagram showing an example of a plurality of light-shielded images according to the first embodiment. FIG. 9 is a diagram showing a process of calculating a corrected image according to the first embodiment. FIG. 10 is a flowchart showing the operation of the imaging device according to the second embodiment. FIG. 11 is a diagram showing the operation of the imaging device according to the second embodiment. FIG. 12 is a flowchart showing the operation of the imaging device according to the modification of the second embodiment. FIG. 13 is a diagram showing an operation of the image pickup apparatus according to the modification of the second embodiment. FIG. 14 is a flowchart showing the operation of the imaging device according to the third embodiment. FIG. 15 is a diagram showing an operation of the imaging device according to the third embodiment. FIG. 16 is a flowchart showing the operation of the imaging device according to the modification of the third embodiment. FIG. 17 is a diagram showing the operation of the imaging device according to the modification of the third embodiment.

An imaging device according to an aspect of the present disclosure includes an imaging device capable of nondestructive readout, an imaging system that collects light on the imaging device, a light blocking unit that blocks light of the imaging system, and the imaging device. A correction unit that generates a corrected image by subtracting the correction image from the obtained main image, the correction unit being obtained by the image pickup device by one exposure in a light-shielded state, and the exposure times are different from each other. A plurality of light-shielded images is acquired using nondestructive readout, and the correction image is generated using at least one of the plurality of light-shielded images.

According to this, it is possible to reduce the difference in the amount of dark current between the main exposure and the light-shielding exposure, which is caused by a temperature change or the like. Therefore, the influence of the dark current amount can be reduced and the image quality of the corrected image can be improved.

For example, the correction unit generates the correction image from the light-shielded image in which the difference between the pixel value of the light-shielded image and the pixel value of the light-shielded area included in the main image is less than a threshold value among the plurality of light-shielded images. You may.

According to this, since the correction image can be generated using the light-shielded image having a small difference in dark current amount from the main image, it is possible to reduce the difference in dark current amount between the main image and the correction image.

For example, the correction unit may repeat the non-destructive reading until the difference becomes less than the threshold value and select a light-shielded image having the difference less than the threshold value as the correction image.

According to this, it is possible to suppress unnecessary non-destructive reading.

For example, the correction unit repeats the non-destructive read until the difference between the pixel value of the read light-shielded image and the pixel value of the light-shielded area included in the main image is less than a threshold value, and the difference is the threshold value. If it is less than the above, a light-shielded image may be acquired from the image sensor by destructive reading, and the light-shielded image acquired by the destructive reading may be selected as the correction image.

According to this, since it is possible to obtain a correction image that more accurately indicates the amount of dark current, it is possible to improve the image quality of the corrected image.

For example, the correction unit may generate the correction image by averaging a plurality of light-shielded images in which the difference is less than the threshold value among the plurality of light-shielded images.

According to this, for example, random noise generated in the signal reading path or the like can be reduced.

For example, the correction unit repeats the nondestructive read at a first interval until the difference becomes less than the threshold value, and when the difference becomes less than the threshold value, the correction unit makes a second interval shorter than the first interval. The correction image may be generated by repeating non-destructive reading and averaging a plurality of light-shielded images acquired by the destructive reading at the second interval.

According to this, since the correction image can be generated using a plurality of light-shielded images having a small difference in dark current amount from the main image, the difference in dark current amount between the main image and the correction image can be reduced.

For example, the correction unit is a light-shielded image in which the difference between the pixel value of the light-shielded area of the light-shielded image and the pixel value of the light-shielded area included in the main image is less than the threshold value among the plurality of light-shielded images. The correction image may be generated from

According to this, it is possible to accurately select the light-shielded images having similar dark current amounts.

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

A control method according to an aspect of the present disclosure relates to an imaging device including an image sensor capable of nondestructive readout, an image capturing system that collects light on the image capturing element, and a light blocking unit that blocks light of the image capturing system. A control method, which includes a correction step of generating a corrected image by subtracting a correction image from a main image obtained by the image sensor, wherein the correction step is performed by one exposure in a light-shielded state. The non-destructive readout is used to obtain a plurality of light-shielded images each having a different exposure time, and the correction image is generated using at least one of the plurality of light-shielded images.

According to this, it is possible to reduce the difference in the amount of dark current between the main exposure and the light-shielding exposure, which is caused by a temperature change or the like. Therefore, the influence of the dark current amount can be reduced and the image quality of the corrected image can be improved.

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

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, constituent elements, arrangement positions of constituent elements, connection forms, and the like shown in the following embodiments are examples and are not intended to limit the present disclosure. Therefore, among the constituent elements in the following embodiments, the constituent elements that are not described in the independent claims showing the highest concept of the present disclosure will be described as arbitrary constituent elements.

It should be noted that each drawing is a schematic diagram and is not necessarily strictly illustrated. Further, in each of the drawings, substantially the same components are denoted by the same reference numerals, and overlapping description will be omitted or simplified.

(Embodiment 1)
[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 showing the configuration of the image pickup apparatus 100 according to the present embodiment. 2A and 2B are diagrams showing an example of the external appearance of the image pickup apparatus 100. For example, as shown in FIGS. 2A and 2B, the imaging device 100 is a camera such as a digital still camera or a digital video camera.

The image pickup apparatus 100 shown in FIG. 1 includes an image pickup element 101, a control unit 102, a display unit 103, a storage unit 104, an image pickup system 106, and a light shielding unit 107. The image pickup device 101 is a solid-state image pickup device (solid-state image pickup device) that converts incident light into an electric signal (image) and outputs the obtained electric signal, and is, for example, an organic sensor using an organic photoelectric conversion element.

The control unit 102 controls the image sensor 101. The control unit 102 also performs various kinds of signal processing on the image obtained by the image sensor 101, and displays the obtained image on the display unit 103 or the storage unit 104. The image output from the control unit 102 may be output to the outside of the image pickup apparatus 100 via an input/output interface (not shown).

The control unit 102 also includes a correction unit 105 that corrects the image obtained by the image sensor 101.

The image pickup system 106 includes, for example, one or a plurality of lenses, and collects light from the outside of the image pickup apparatus 100 on the image pickup element 101.

The light blocking unit 107 is, for example, a mechanical shutter, and blocks the light of the imaging system 106.

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

The image sensor 101 shown in FIG. 3 is provided with 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 reading unit 204, and each 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 pixels 201 via the reset control lines 205. In addition, 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 the 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 showing the 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. The 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 section 212 may be configured by a parasitic capacitance such as a wiring capacitance instead of a dedicated capacitive 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 the drain and the source generally depend on the circuit operation, and in many cases cannot be 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, the drain in this embodiment 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 section 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 section 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 gate of the selection transistor 215 is connected to the address control line 206, the drain thereof is connected to the source of the amplification transistor 214, and the source thereof is 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 by all the pixels 201.

Further, as a feature of the organic sensor, there are nondestructive readout and electronic ND (Neutral Density) control. Non-destructive reading is a process of reading image data during the exposure period and continuing exposure. In the conventional reading (hereinafter, referred to as destructive reading), it is necessary to end the exposure when reading. That is, only one image could be obtained by one exposure. On the other hand, by using the non-destructive reading, it is possible to read the image data exposed by that time and continue the exposure during the exposure period. This makes it possible to obtain a plurality of images with different exposure times with one exposure.

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

The image pickup device 101 may include a mesher and may use both electronic ND control and light blocking by a mechanical shutter, or may use only light blocking by a mechanical shutter.

Although an example in which the image sensor 101 is an organic sensor will be described here, the image sensor 101 may be anything other than an organic sensor as long as non-destructive reading or electronic ND control can be realized. 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 image pickup apparatus 100 according to the present embodiment will be described. FIG. 5 is a flowchart showing a flow of operations of the image pickup apparatus 100. FIG. 6 is a diagram for explaining the operation of the image pickup apparatus 100. For example, this operation is used when a night sky or a night view is exposed for a long time.

As shown in FIG. 5, the imaging device 100 first shoots the main image 121 (S101). Specifically, as shown in FIG. 6, normal exposure is performed from time t1, and thereafter, the main image 121 is read by destructive reading.

Next, the imaging device 100 starts light-shielding exposure for generating the correction image 141 at time t2 (S102). Specifically, the light-shielding exposure is to perform exposure in a light-shielded state, and the light is shielded by, for example, the electronic ND control described above or a mechanical shutter. Further, the light-shielded image 131 captured in such a light-shielded state shows a pixel value (luminance value) corresponding to the amount of dark current.

Next, the image pickup apparatus 100 performs a non-destructive reading a predetermined number of times during the light-shielding exposure period to generate a plurality of light-shielding images 131 (S103). Specifically, the imaging apparatus 100 repeats nondestructive read-out at a predetermined cycle T4 after a predetermined time T3 has elapsed after the start of exposure.

The exposure time T2 for the light-shielding exposure is predetermined and is longer than the main exposure time T1, for example.

FIG. 7 is a diagram showing an example of the main image 121. FIG. 8 is a diagram showing an example of a plurality of light-shielded images 131. As shown in FIG. 7, the main image 121 includes an effective area 122 for outputting an electric signal according to incident light and an OB (optical black) area (also referred to as a light shielding area) 123 that is always shielded. Including. Similarly, the shaded image 131 also includes an effective area 132 and an OB area 133. Further, the plurality of light-shielded images 131 have different brightness values indicating the dark current amount (black level) because the exposure times are different from each other.

Next, the image capturing apparatus 100 selects, from the plurality of light-shielded images 131, the light-shielded image 131 in which the pixel value (luminance value) of the OB region 123 included in the main image 121 and the pixel value of the OB region 133 are close to each other, the correction image 141. (S104). That is, the imaging device 100 selects a light-shielded image in which the difference between the pixel value of the light-shielded image 131 and the pixel value of the OB area 123 included in the main image 121 is less than a predetermined threshold value among the plurality of light-shielded images 131. Select 131. For example, the imaging device 100 selects the light-shielded image 131 with the smallest difference.

The difference is, for example, the difference between the average value of the pixel values of the OB area 123 and the average value of the pixel values of the OB area 133. The maximum value, the minimum value, the median value, or the like may be used instead of the average value. The area used for comparison may be the entire OB area, only a part of the OB area, or one specific pixel included in the OB area. The areas used for comparison are preferably the same area.

Next, as shown in FIG. 9, the imaging apparatus 100 subtracts the correction image 141 from the main image 121 to generate the corrected image 142 (S105). Specifically, the pixel value of the pixel at the same position of the correction image 141 is subtracted from the pixel value of each pixel of the main image 121. As a result, the influence of dark current during long-time exposure is reduced.

In addition, during long-time exposure or the like, the environment (for example, temperature) may change between the main exposure and the light-shielding exposure. As a result, even when the exposure times of the main exposure and the light-shielding exposure are the same, the detected dark current amount may differ. On the other hand, as in the present embodiment, by selecting, as the correction image 141, the light-shielded image 131 in which the pixel values of the OB region are close to each other from the plurality of light-shielded images 131 obtained by the non-destructive reading and having different exposure times. It is possible to suppress a difference in dark current amount between the main exposure and the light-shielding exposure.

Although FIG. 6 shows an example in which the non-destructive read cycle T4 is constant, it does not have to be constant. For example, the nondestructive read interval at the time when the exposure time approaches the exposure time T1 of the main exposure may be shortened.

Further, in FIG. 6, the nondestructive read is performed after a predetermined time has passed, but the nondestructive read may be periodically performed from the start of the exposure.

Further, in FIG. 6, all of the plurality of light-shielded images 131 are obtained by nondestructive reading, but the last one reading may be destructive reading.

As described above, the image pickup apparatus 100 according to the present embodiment includes the image pickup element 101 capable of nondestructive readout, the image pickup system 106 that collects light on the image pickup element 101, and the light shield that blocks the light of the image pickup system 106. The unit 107 and the correction unit 105 that generates the corrected image 142 by subtracting the correction image 141 from the main image 121 obtained by the image sensor 101. The correction unit 105 acquires a plurality of light-shielded images 131 obtained by the image sensor 101 by one exposure in a light-shielded state and having different exposure times by using nondestructive readout, and acquires at least one of the plurality of light-shielded images 131. The correction image 141 is generated by using the correction image 141.

As a result, it is possible to reduce the difference in dark current amount between the main exposure and the light-shielding exposure, which is caused by a temperature change or the like. Therefore, the influence of dark current can be reduced, and the image quality of the corrected image 142 can be improved.

The function of blocking the light of the imaging system 106 is not limited to the method using the mesher, and may be a method using another mechanism such as electronic ND control. That is, the light blocking unit that blocks the light of the imaging system 106 is not limited to the light blocking unit 107 (mechanical shutter or the like) shown in FIG. 1, but may be a mechanism for performing electronic ND control or the like.

In addition, the correction unit 105, among the plurality of light-shielded images 131, the light-shielded image 131 in which the difference between the pixel value of the light-shielded image 131 and the pixel value of the light-shielded region (OB region 123) included in the main image 121 is less than the threshold value. From this, a correction image 141 is generated. As a result, the correction image 141 can be generated using the light-shielded image 131 having a small difference in dark current amount from the main image 121, and thus the difference in dark current amount between the main image 121 and the correction image 141 can be reduced.

Further, the correction unit 105 sets the pixel value of the light-shielded area (OB area 133) of the light-shielded image 131 among the plurality of light-shielded images 131 and the pixel value of the light-shielded area (OB area 123) included in the main image 121. The correction image 141 is generated from the light-shielded image whose difference is less than the threshold value. That is, the pixel values in the same area are compared. As a result, it is possible to accurately select the shaded images 131 having similar dark current amounts.

(Embodiment 2)
In this embodiment, a modification of the first embodiment will be described. In the following, differences from the previous embodiment will be mainly described, and redundant description will be omitted.

The first embodiment has described the example in which the exposure period T2 of the light-shielding exposure and the number of the light-shielding images 131 to be nondestructively read are predetermined. In the present embodiment, the dark current amount of the light-shielded image 131 is dynamically determined, and the exposure is ended at the timing when the light-shielded image 131 having a dark current amount similar to the main image 121 is obtained. As a result, it is possible to suppress unnecessary nondestructive reading as compared with the first embodiment.

FIG. 10 is a flowchart showing a flow of operations of the image pickup apparatus 100 according to this embodiment. FIG. 11 is a diagram for explaining this operation. First, as in the first embodiment, the imaging device 100 captures the main image 121 and starts light-shielding exposure at time t2 (S112).

Next, the imaging device 100 performs nondestructive read during the light-shielding exposure period (S113). Next, the imaging apparatus 100 determines whether the pixel value of the OB area 133 of the light-shielded image 131 obtained by the nondestructive read is close to the pixel value of the OB area 123 of the main image 121 (S114). Specifically, the imaging device 100 determines whether the difference between the pixel value of the OB area 133 of the light-shielded image 131 and the pixel value of the OB area 123 of the main image 121 is less than a predetermined threshold value.

If the difference is not less than the threshold value (No in S114), nondestructive read is performed again (S113), and the same determination process is performed again (S114).

On the other hand, when the difference is less than the threshold value (Yes in S114), the imaging apparatus 100 ends the light-shielding exposure (S115) and selects the light-shielding image 131 read by the nondestructive read last as the correction image 141. Yes (S116). For example, in the example shown in FIG. 11, the difference is determined to be less than the threshold value at time t3, and the light-shielded image 131 is selected as the correction image 141.

Next, the imaging device 100 subtracts the correction image 141 from the main image 121 to generate the corrected image 142 (S117).

In this way, the correction unit 105 repeats nondestructive read until the difference between the pixel value of the light-shielded image 131 and the pixel value of the OB area 123 included in the main image 121 becomes less than the threshold value, and the difference is less than the threshold value. The light-shielded image 131 that has changed to is selected as the correction image 141.

As a result, it is possible to suppress unnecessary nondestructive reading as compared with the first embodiment.

It should be noted that the imaging apparatus 100 may perform destructive reading when the difference becomes less than the threshold value and use the obtained image as the correction image 141. FIG. 12 is a flowchart showing the operation of the image pickup apparatus 100 in this case. FIG. 13 is a diagram for explaining this operation.

The process shown in FIG. 12 includes step S116A instead of step S116 in the process shown in FIG. That is, when the difference is less than the threshold value (Yes in S114), the imaging apparatus 100 ends the light-shielding exposure (S115) and acquires the correction image 141 by destructive reading (S116A).

For example, in the example shown in FIG. 13, it is determined that the difference is less than the threshold value at time t3. Then, the imaging device 100 acquires the correction image 141 by destructive reading. Note that in FIG. 13, destructive read is performed immediately after the determination, but it does not have to be performed immediately after.

In this way, the correction unit 105 repeats nondestructive read until the difference between the pixel value of the light-shielded image 131 and the pixel value of the OB area 123 included in the main image 121 becomes less than the threshold value, and the difference is less than the threshold value. In such a case, a light-shielded image is acquired from the image sensor 101 by destructive reading and the light-shielded image acquired by the destructive reading is selected as the correction image 141.

Here, in general, in nondestructive reading, some processing such as noise removal processing performed during destructive reading is not performed. That is, the image obtained by the destructive read has higher image quality than the image obtained by the non-destructive read. Therefore, by using the image obtained by the non-destructive read only for the determination process and using the image obtained by the destructive read as the correction image 141, the correction image 141 showing the dark current amount more accurately can be obtained. it can. Thereby, the image quality of the corrected image 142 can be improved.

(Embodiment 3)
In this embodiment, a modification of the first and second embodiments will be described. In the first and second embodiments, an example in which one light-shielded image 131 obtained by nondestructive reading or destructive reading is directly used as the correction image 141 has been described. In this embodiment, an example in which the correction image 141 is generated using a plurality of light-shielded images 131 will be described.

FIG. 14 is a flowchart showing the operation of the modification of the first embodiment. The process shown in FIG. 14 includes step S104A instead of step S104 in the process shown in FIG. FIG. 15 is a diagram for explaining this operation.

In step S104A, the imaging apparatus 100, from the plurality of light-shielded images 131 obtained by non-destructive reading, has a plurality of light-shielded images 131 in which the pixel value of the OB area 123 included in the main image 121 is close to the pixel value of the OB area 133. The correction image 141 is generated by using (S104A).

For example, the image capturing apparatus 100 includes a plurality of shaded images 131 in which the difference between the pixel value of the shaded image 131 and the pixel value of the OB area 123 included in the main image 121 is less than a predetermined threshold value. The shading image 131 is used to generate the correction image 141. For example, the correction unit 105 generates the correction image 141 by averaging the plurality of light-shielded images 131 having the difference less than the threshold value among the plurality of light-shielded images 131.

For example, in the example shown in FIG. 15, the difference is determined to be less than the threshold for the light-shielded image 131 read at the times t3 and t4. Then, the correction image 141 is generated using the two light-shielded images 131.

By performing the averaging in this way, for example, random noise generated in the signal reading path can be reduced. Note that the method of reducing random noise using a plurality of images is not limited to arithmetic averaging. For example, the pixel value of a pixel in which random noise is generated is a value distant from the pixel values of pixels at the same position in other plural images. Therefore, the imaging apparatus 100 determines whether or not random noise is generated in each pixel of each image based on such a variation in pixel value of each pixel between images, and a pixel in which random noise is not generated is determined. The correction image 141 may be generated by combining only these. Alternatively, the imaging apparatus 100 may generate the correction image 141 by averaging the plurality of light-shielded images 131 excluding the pixels in which random noise has occurred.

Further, as in the modified example of the first embodiment, the plurality of light-shielded images 131 may include images that have been destructively read.

Next, a case where the same modification is applied to the second embodiment will be described. FIG. 16 is a flowchart showing the operation of the image pickup apparatus 100 in this case. FIG. 17 is a diagram for explaining this operation.

The process shown in FIG. 16 includes steps S116B and S116C instead of step S116A in the process shown in FIG.

When the difference is less than the threshold value (Yes in S114), the imaging apparatus 100 ends the light-shielding exposure (S115), and continuously performs nondestructive reading, and then performs destructive reading, thereby performing a plurality of The shaded image 131 is acquired (S116B). Next, the imaging device 100 generates the correction image 141 using the plurality of light-shielded images 131 obtained in step S116B. The method of generating the correction image 141 is the same as, for example, step S104A described above.

Further, as shown in FIG. 15, the nondestructive read interval T5 after the difference is determined to be less than the threshold value (after time t3) is shorter than the nondestructive read interval T4 before that. That is, the correction unit 105 repeats the non-destructive read at the first interval T4 until the difference becomes less than the threshold value, and when the difference becomes less than the threshold value, the non-destructive read at the second interval T5 shorter than the first interval. The correction image 141 may be generated by repeating the above and averaging the plurality of light-shielded images 131 acquired by the destructive reading at the second interval T5.

Accordingly, the correction image 141 can be generated using the plurality of light-shielded images 131 having a small difference in dark current amount from the main image 121, and thus the difference in dark current amount between the main image 121 and the correction image 141 can be reduced. ..

In the example shown in FIG. 17, the destructive read is performed last, but it may not be performed. Further, in the example shown in FIG. 17, continuous nondestructive reading is performed after the exposure is completed, but nondestructive reading may be performed during the exposure.

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

For example, each processing unit included in the imaging device according to the above-described 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 some or all of them.

Further, the integrated circuit is not limited to the 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 the LSI is manufactured, 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-described embodiments, each component may be realized by dedicated hardware or 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 in a recording medium such as a hard disk or a semiconductor memory.

In addition, the present disclosure may be realized as a control method executed by the imaging device.

Further, the circuit configuration shown in the above circuit diagram is an example, and the present disclosure is not limited to the above circuit configuration. That is, similarly to the above circuit configuration, a circuit capable of realizing the characteristic function of the present disclosure is also included in the present disclosure. Moreover, all the numbers used above are examples for specifically explaining the present disclosure, and the present disclosure is not limited to the exemplified numbers.

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

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

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

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

100 image pickup device 101 image pickup device 102 control unit 103 display unit 104 storage unit 105 correction unit 106 image pickup system 107 light-shielding unit 121 main image 122, 132 effective region 123, 133 OB region 131 light-shielded image 141 correction image 142 corrected image 201 pixels 202 vertical scanning unit 203 column signal processing unit 204 horizontal reading unit 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 (9)

An image sensor capable of non-destructive readout,
An image pickup system that collects light on the image pickup element,
A light blocking portion for blocking the light of the imaging system,
A correction unit that generates a corrected image by subtracting the correction image from the main image obtained by the image sensor,
The correction unit is
A plurality of light-shielded images obtained by the image pickup device by exposure in a light-shielded state and having different exposure times are acquired by using nondestructive readout,
An imaging device that generates the correction image using at least one of the plurality of light-shielded images. The correction unit is
The image for correction is generated from a light-shielded image in which a difference between a pixel value of the light-shielded image and a pixel value of a light-shielded area included in the main image is less than a threshold value among the plurality of light-shielded images. apparatus. The correction unit is
Repeating the non-destructive read until the difference is less than the threshold,
The imaging device according to claim 2, wherein a light-shielded image in which the difference is less than the threshold value is selected as the correction image. The correction unit is
The non-destructive reading is repeated until the difference between the pixel value of the read light-shielded image and the pixel value of the light-shielded area included in the main image is less than a threshold value,
If the difference is less than the threshold, to obtain a light-shielded image from the image sensor by destructive readout,
The image pickup apparatus according to claim 1, wherein the light-shielded image acquired by the destructive reading is selected as the correction image. The correction unit is
The image pickup apparatus according to claim 2, wherein the correction image is generated by averaging a plurality of light-shielded images in which the difference is less than the threshold value among the plurality of light-shielded images. The correction unit is
Repeating the non-destructive read at a first interval until the difference is less than the threshold,
When the difference is less than the threshold value, the nondestructive read is repeated at a second interval shorter than the first interval,
Imaging device according to claim 5, wherein generating the correction image by averaging a plurality of dark frame obtained by the non-destructive readout in the second interval. The correction unit is
Of the plurality of light-shielded images, the correction image is generated from the light-shielded image in which the difference between the pixel value of the light-shielded area of the light-shielded image and the pixel value of the light-shielded area included in the main image is less than the threshold value. The image pickup apparatus according to claim 2. The imaging device, the serial placement of the imaging device any one of claims 1 to 7 is an organic sensor. A control method for an image pickup device, comprising: an image pickup device capable of nondestructive readout; an image pickup system that collects light on the image pickup device; and a light blocking unit that blocks light of the image pickup system,
Including a correction step of generating a corrected image by subtracting the correction image from the main image obtained by the image sensor,
In the correction step,
A plurality of light-shielded images obtained by the image sensor by light exposure in a light-shielded state and having different exposure times are acquired by using nondestructive readout,
A control method for generating the correction image using at least one of the plurality of light-shielded images.

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