WO2024254826A1 - 固体拍摄元件、以及具备固体拍摄元件的拍摄装置 - Google Patents

固体拍摄元件、以及具备固体拍摄元件的拍摄装置 Download PDF

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Publication number
WO2024254826A1
WO2024254826A1 PCT/CN2023/100434 CN2023100434W WO2024254826A1 WO 2024254826 A1 WO2024254826 A1 WO 2024254826A1 CN 2023100434 W CN2023100434 W CN 2023100434W WO 2024254826 A1 WO2024254826 A1 WO 2024254826A1
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Prior art keywords
reading
solid
state imaging
imaging element
gain
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English (en)
French (fr)
Inventor
山下雄一郎
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Beijing Xiaomi Mobile Software Co Ltd
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Beijing Xiaomi Mobile Software Co Ltd
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Priority to PCT/CN2023/100434 priority Critical patent/WO2024254826A1/zh
Priority to JP2023541320A priority patent/JP7861001B2/ja
Priority to CN202380009552.6A priority patent/CN119605189A/zh
Publication of WO2024254826A1 publication Critical patent/WO2024254826A1/zh
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/50—Control of the SSIS exposure
    • H04N25/57—Control of the dynamic range
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
    • H04N25/63—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to dark current

Definitions

  • the present invention relates to a solid-state imaging element and an imaging device including the solid-state imaging element.
  • solid-state imaging elements such as CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor) image sensors used in digital cameras, digital video cameras, smartphones and other imaging devices with imaging functions
  • CCD Charge Coupled Device
  • CMOS Complementary Metal Oxide Semiconductor
  • US7075049B2 dual conversion gain method
  • an SNR dip (SNR dip) is generated at the boundary between the signal obtained by reading at the high read gain and the signal obtained by reading at the low read gain (the boundary of the illumination from the subject) (refer to FIG5 ).
  • SNR dip SNR dip
  • Patent document 1 US7075049B2.
  • an object of the present invention is to provide a solid-state imaging element and an imaging device having the solid-state imaging element, wherein the solid-state imaging element can read the same exposure signal multiple times with different read gains, thereby achieving a wider dynamic range while suppressing image degradation.
  • the solid-state imaging element of the present invention reads the same exposure signal multiple times using different read gains.
  • the different read gains include the minimum read gain and a read gain higher than the minimum read gain, namely, a high read gain.
  • the solid-state imaging element may be configured as follows:
  • the correlated multi-sampling reading can be performed by switching between reading at the lowest read gain and reading at a high read gain, the high read gain being a read gain sampling higher than the lowest read gain.
  • the reading under the same gain includes the reading of reset voltage and the reading of signal voltage.
  • the number of samplings for reading the reset voltage and the number of samplings for reading the signal voltage may be the same.
  • the reading under the same gain includes the reading of reset voltage and the reading of signal voltage.
  • the number of samplings for reading the signal voltage is greater than the number of samplings for reading the reset voltage.
  • the solid-state imaging element of the present invention reads the same exposure signal multiple times using different read gains.
  • correlated multi-sampling is performed.
  • the correlated multi-sampling may be performed in each of the plurality of reads except for the read at the highest read gain.
  • the solid-state imaging element of the present invention reads the same exposure signal multiple times using different read gains.
  • correlated multi-sampling is performed.
  • the photographing device of the present invention comprises:
  • the imaging device includes an exposure control unit connected to the solid-state imaging element.
  • the solid-state imaging element is provided with a plurality of combinations for performing the above-mentioned correlated multi-sampling reading.
  • the exposure control unit may instruct the solid-state imaging element, during imaging, the best combination among the plurality of combinations.
  • FIG. 1 is a functional block diagram of an imaging device according to this embodiment.
  • FIG. 2 is a diagram showing a configuration of a solid-state imaging element included in the imaging device.
  • FIG. 3 is a circuit diagram of a pixel included in the solid-state imaging element.
  • FIG. 4 is a diagram for explaining the reading of the voltage signal in the above-mentioned pixel.
  • FIG. 5 is a diagram showing the relationship between the illumination from the object and SN when a voltage signal is read by a solid-state imaging element that does not perform correlated multisampling.
  • FIG. 6 is a diagram showing the relationship between the illumination from the object and the SN when the voltage signal is read from the solid-state imaging element by correlated multi-sampling with the sampling number of 2 by reading at the lowest read gain.
  • FIG. 7 is a diagram for explaining the reading of the voltage signal in the above-mentioned pixel.
  • FIG. 8 is a diagram for explaining the reading of a voltage signal under a pixel according to another embodiment.
  • FIG. 9 is a diagram showing the relationship between the illumination from the object and the SN when the voltage signal is read from the solid-state imaging element in which correlated multi-sampling is performed with the sampling number of 4 times by reading at the lowest read gain.
  • FIG. 10 is a diagram for explaining the reading of a voltage signal under a pixel according to another embodiment.
  • FIG. 11 is a diagram for explaining the reading of a voltage signal under a pixel according to another embodiment.
  • the solid-state imaging element of the present invention reads the same exposure signal multiple times using different read gains.
  • correlated multi-sampling is performed on at least the reading at the lowest reading gain, so that the SNR difference at the boundary (boundary of the illumination from the subject) between the signal obtained by reading at the lowest reading gain and the signal obtained by reading at a reading gain one level lower than the lowest reading gain is suppressed (for example, refer to Figures 6 and 9), thereby ensuring a wider dynamic range while suppressing the degradation of the image quality of the captured image.
  • the different read gains include the minimum read gain and a read gain higher than the minimum read gain, namely, a high read gain.
  • the influence of noise (random noise, etc.) in the signal read out with a high read gain is suppressed, and the image quality of the captured image is improved.
  • the solid-state imaging element may be configured as follows:
  • the correlated multi-sampling reading can be performed by switching between reading at the lowest read gain and reading at a high read gain, the high read gain being a read gain sampling higher than the lowest read gain.
  • the method in a scene requiring a high dynamic range during shooting, is switched to correlated multiple sampling during reading at the lowest reading gain, thereby suppressing the SNR difference at the boundary (boundary of the illumination from the object) between the signal obtained by reading at the lowest reading gain and the signal obtained by reading at a high reading gain, thereby ensuring a wider dynamic range while suppressing degradation of the captured image quality.
  • the correlated multiple sampling is switched to reading at a high read gain, thereby suppressing the influence of noise (random noise, etc.) in the signal read by the high read gain, thereby improving the image quality of the captured image (image quality on the low illumination side).
  • the total reading time of reading at the lowest reading gain and reading at a high reading gain is the same or approximately the same, thereby making it possible to make the frame rate of video shooting before and after the above-mentioned switching constant or approximately constant.
  • the reading under the same gain includes the reading of reset voltage and the reading of signal voltage.
  • the number of samplings for reading the reset voltage and the number of samplings for reading the signal voltage may be the same.
  • the number of sampling times for reading the reset voltage is made the same as the number of sampling times for reading the signal voltage, thereby appropriately suppressing the influence of noise (random noise, etc.) in the read signal, thereby further improving the quality of the captured image.
  • the reading under the same gain includes the reading of reset voltage and the reading of signal voltage.
  • the number of samplings for reading the signal voltage may be greater than the number of samplings for reading the reset voltage.
  • the solid-state imaging element of the present invention reads the same exposure signal multiple times using different read gains.
  • correlated multi-sampling is performed.
  • the difference in SNR level at at least one point is suppressed, thereby making it possible to suppress degradation in the quality of a captured image while ensuring a wider dynamic range.
  • the solid-state imaging element of the present invention reads the same exposure signal multiple times using different read gains.
  • correlated multi-sampling is performed.
  • the difference in SNR level at at least one point is suppressed, or the influence of noise (random noise, etc.) in the signal read by the highest read gain is suppressed, so that degradation of the image quality of the captured image can be suppressed while ensuring a wider dynamic range.
  • the photographing device of the present invention comprises:
  • any of the above-mentioned solid-state imaging elements is arranged at an imaging position of the above-mentioned optical system.
  • the imaging device includes an exposure control unit connected to the solid-state imaging element.
  • the solid-state imaging element is provided with a plurality of combinations for performing the above-mentioned correlated multi-sampling reading.
  • the exposure control unit may instruct the solid-state imaging element, during imaging, the best combination among the plurality of combinations.
  • the exposure control unit automatically selects the correlated multi-sampling reading.
  • solid-state imaging element and imaging device including the solid-state imaging element it is possible to suppress image degradation while realizing a wider dynamic range in a solid-state imaging element that reads the same exposure signal multiple times with different read gains.
  • the imaging device includes an optical system 101 a and a solid-state imaging element 1 disposed at an imaging position of the optical system 101 a .
  • the imaging device can capture images of objects such as digital cameras, smartphones, and tablet devices.
  • the imaging device 100 of this embodiment is, for example, a smartphone.
  • the imaging device 100 includes an imaging unit 101 and a control unit 102.
  • the imaging device 100 also includes a nonvolatile memory 103, an operation memory 104, an operation unit 105, a display unit 106, a storage medium 107, a connection unit 108, a short-range wireless communication unit 109, a public network connection unit 110, a microphone 111, and a speaker 112.
  • the imaging unit 101 converts the image of the object formed by the optical system 101a of the imaging unit 101 into an electrical signal, performs noise reduction processing, etc., and outputs digital data as image data of an output image under the control of the control unit 102.
  • the imaging unit 101 includes an optical system 101a composed of at least one optical element such as a lens, and a solid-state imaging element 1 that converts the image of the object (photographing object) formed by the optical system 101a into an electrical signal.
  • the solid-state imaging element 1 is embedded in a smartphone, a digital camera, etc., and is an element for photographing an object.
  • the solid-state imaging element 1 of the present embodiment is, for example, a CMOS image sensor.
  • the same exposure signal is read multiple times with different read gains (voltage conversion gains), and correlated multiple sampling (CMS) is performed in the reading at the lowest read gain among the multiple readings.
  • CMS correlated multiple sampling
  • the different read gains include a minimum read gain and a high read gain which is a read gain higher than the minimum read gain.
  • the solid-state imaging element 1 of this embodiment is configured to be able to switch between reading at the minimum read gain and reading at the high read gain to perform correlated multi-sampling reading.
  • the solid-state imaging element 1 has: a plurality of pixels (pixels) 2 arranged in a matrix, a plurality of row signal lines 3 arranged in each row relative to the matrix-shaped pixel group and extending in the row direction (left-right direction in FIG. 2 ), a plurality of column signal lines 4 arranged in each column and extending in the column direction (up-down direction in FIG. 2 ), and a signal processing unit 5 connecting these plurality of row signal lines 3 with the plurality of column signal lines 4.
  • a plurality of pixels (pixels) 2 arranged in a matrix
  • a plurality of row signal lines 3 arranged in each row relative to the matrix-shaped pixel group and extending in the row direction (left-right direction in FIG. 2 )
  • a plurality of column signal lines 4 arranged in each column and extending in the column direction (up-down direction in FIG. 2 )
  • a signal processing unit 5 connecting these plurality of row signal lines 3 with the plurality of column signal lines 4.
  • a plurality of pixels 2 arranged in a matrix form respectively include: a photoelectric conversion element 21 such as a photodiode, a floating point 22 for transmitting a signal charge generated by the photoelectric conversion element 21, a holding capacity 23 capable of holding the signal charge, a transfer transistor 24 connecting the photoelectric conversion element 21 and the floating point 22, a holding switch transistor 25 connecting the floating point 22 and the holding capacity 23, a reset transistor 26 connecting the holding capacity 23 and a reset power supply VDD1, a source follower SF having an amplifier transistor 27 and amplifying the voltage signal of the floating point 22, and a selection transistor 28 connecting the amplifier transistor 27 and the column signal line 4.
  • a photoelectric conversion element 21 such as a photodiode
  • a floating point 22 for transmitting a signal charge generated by the photoelectric conversion element 21
  • a holding capacity 23 capable of holding the signal charge
  • a transfer transistor 24 connecting the photoelectric conversion element 21 and the floating point 22
  • a holding switch transistor 25 connecting the floating point 22 and the holding capacity 23
  • the solid-state imaging element 1 of the present embodiment is a so-called dual conversion gain (DCG) type solid-state imaging element 1 that switches the read gain (voltage conversion gain/conversion gain) between a minimum read gain and a read gain higher than the minimum read gain, i.e., a high read gain, by switching the switch transistor 25 ON and OFF.
  • the above read gain is a read gain when the signal charge transferred from the photoelectric conversion element 21 to the floating point 22 in each pixel 2 is read as a voltage signal by the source follower SF.
  • the ratio of the lowest read gain (Low conversion gain: LCG) to the high read gain (High conversion gain: HCG) in the solid-state imaging element 1 of the present embodiment (Gain ratio) is, for example, 1: 64.
  • “reading” in the solid-state imaging element 1 of the present embodiment may be either analog reading or reading after AD conversion.
  • the solid-state imaging element 1 performs reading of a reset voltage and reading of a signal voltage separately in reading at the same gain (LCG or HCG).
  • a reset voltage is read as a voltage signal in a state where the floating point 22 is reset
  • a signal voltage is read as a voltage signal in a state where the floating point 22 transfers signal charge from the photoelectric conversion element 21 after reading the reset voltage, and the difference signal between these signal voltages and the reset voltage is generated respectively. That is, the solid-state imaging element 1 performs so-called correlated double sampling (CDS) in the reading from each pixel 2.
  • CDS correlated double sampling
  • the above solid-state imaging element 1 reads the voltage signal under HCG and the voltage signal under LCG in each pixel 2 arranged in a matrix for each row. Then, in the reading of the voltage signal of each row, based on the instruction from the control unit 102, correlated multiple sampling (CMS) is performed by either reading under HCG or reading under LCG.
  • CMS is a signal sampling method that removes correlated noise components and reduces low-frequency noise and random noise caused by the averaging effect by sampling the reset level voltage and the signal level voltage multiple times, performing weighted averaging, and taking differences.
  • the solid-state imaging element 1 switches the object of correlated multiple sampling to reading under LCG according to the instruction of the control unit (exposure control unit) 102.
  • the number of samplings of reading the reset voltage under LCG in the correlated multiple sampling is the same as the number of samplings of reading the signal voltage under LCG.
  • the number of samplings of reading the reset voltage under LCG in the correlated multiple sampling and the number of samplings of reading the signal voltage under LCG are respectively 2 times.
  • FIG. 4 is a diagram schematically showing the steps of reading each row, and the length in the left-right direction in each step corresponds to the length of the reading time. The same is true for FIGS. 7, 8, 10, and 11.
  • the solid-state imaging element 1 averages the reset voltage and signal voltage of the LCG that have been correlated with multiple sampling, i.e., sampled multiple times (twice in the example of the present embodiment), and then generates a difference signal between the average reset voltage and the average signal voltage (i.e., correlated double sampling), and generates a difference signal between the reset voltage and the signal voltage of the HCG (correlated double sampling).
  • the reading gain is low, so the influence of random noise and the like becomes larger.
  • the influence of noise such as random noise in the reading under LCG is suppressed compared to the case where correlated multisampling is not performed, thereby reducing the SNR dip (SNR dip) ⁇ at the boundary (boundary from the illumination of the subject) between the signal obtained by reading under LCG and the signal obtained by reading under HCG (refer to FIG. 6).
  • SNR dip SNR dip
  • the solid-state imaging element 1 of this embodiment suppresses the SNR high-low difference ⁇ from 6 dB to 4 dB compared to the case where correlated multi-sampling is not performed (refer to FIG5 ).
  • FIG5 and FIG6 are graphs in which the vertical axis is set to SNR [dB] and the horizontal axis is set to the illuminance [lux] from the object being photographed. The same is true for FIG9 .
  • the solid-state imaging element 1 switches the object of correlated multiple sampling to reading under HCG according to the instruction from the control unit (exposure control unit) 102.
  • the solid-state imaging element 1 is the same as when correlated multiple sampling is performed in reading under LCG, and the number of samplings of the reset voltage reading under HCG in the correlated multiple sampling is the same as the number of samplings of the signal voltage reading under HCG.
  • the number of samplings of the reset voltage reading under HCG and the number of samplings of the signal voltage reading under HCG in the correlated multiple sampling are respectively 2 times.
  • the reset voltage is read under LCG once for each row, the reset voltage is read and sampled under HCG twice (i.e., the reset voltage is sampled twice in the correlated multiple sampling), the signal voltage is read and sampled twice under HCG (i.e., the signal voltage is sampled twice in the correlated multiple sampling), and the signal voltage is read under LCG once (refer to FIG. 7 ).
  • the solid-state imaging element 1 performs correlated double sampling of the reset voltage and signal voltage of LCG, averages the reset voltage and signal voltage of HCG that have been correlated multi-sampled, i.e., sampled multiple times (twice in the example of this embodiment), and then performs correlated double sampling of the average reset voltage and the average signal voltage.
  • the image signal is generated using the signal obtained by multiple sampling and averaging through correlated multi-sampling. Therefore, in the reading under HCG, the influence of noise such as random noise in the reading under HCG is suppressed compared to the case where correlated multi-sampling is not performed. Therefore, the image quality on the side with smaller illumination in the reading signal under HCG of Figure 6 is improved.
  • control unit 102 controls each unit of the imaging device 100 according to the input signal and program.
  • control unit 102 generates a captured image (image data) from the signal output from the solid-state imaging element 1, and outputs it to the display unit 106.
  • control unit 102 of this embodiment has an exposure control unit 102A, which instructs the solid-state imaging element 1 to perform correlated multi-sampling by which of the reading under LCG and the reading under HCG.
  • the nonvolatile memory 103 is an electrically erasable and storable nonvolatile memory.
  • the nonvolatile memory 103 of this embodiment stores an OS (Operating System) as basic software executed by the control unit 102 and an application program that realizes application functions in cooperation with the OS.
  • OS Operating System
  • the operation memory 104 is used as an image display memory for the display unit 106 , an operation area for the control unit 102 , and the like.
  • the operation unit 105 is used by a user or the like to input instructions to the imaging device 100.
  • the operation unit 105 of this embodiment includes a power button for instructing ON/OFF of the power of the imaging device 100, a touch panel formed on the display unit 106, and the like.
  • the display unit 106 displays (outputs to the outside) a captured image (image data), displays characters for operation, and the like.
  • the storage medium 107 stores image data output from the imaging unit 101 .
  • connection unit 108 is an interface for connecting to an external device.
  • the imaging device 100 exchanges data with the external device through the connection unit 108 .
  • the short-distance wireless communication unit 109 is a communication unit for performing short-distance wireless communication and is composed of an antenna for wireless communication, a modulation and demodulation circuit for processing wireless signals, and a communication controller.
  • the public network connection unit 110 is an interface for public wireless communication.
  • the camera 100 communicates with other devices for a call through the public network connection unit 110.
  • the control unit 102 inputs and outputs sound signals through the microphone 111 and the speaker 112, thereby realizing the above-mentioned call.
  • the public network connection unit 110 of this embodiment is an antenna, and the control unit 102 is connected to the public network through the antenna.
  • the solid-state imaging element 1 of the imaging device 100 described above reads the same exposure signal multiple times with different read gains, and performs correlated multi-sampling (CMS) in the reading at the lowest read gain (LCG) among the multiple readings.
  • CMS correlated multi-sampling
  • the different read gains include a minimum read gain (LCG) and a high read gain (HCG) which is a read gain higher than the LCG, and correlated multi sampling (CMS) is performed in reading under the HCG.
  • LCG minimum read gain
  • HCG high read gain
  • CMS correlated multi sampling
  • the solid-state imaging device 1 of the present embodiment is configured to be able to switch between reading at the lowest read gain (LCG) and reading at a high read gain (HCG) having a read gain higher than LCG to perform correlated multi sampling (CMS) reading.
  • LCG lowest read gain
  • HCG high read gain
  • CMS correlated multi sampling
  • the method switches to correlated multiple sampling during reading under LCG, thereby suppressing the SNR height difference ⁇ at the boundary (boundary of illumination from the object) between the signal obtained by reading under LCG and the signal obtained by reading under HCG, thereby ensuring a wider dynamic range while suppressing degradation of the captured image quality.
  • the total reading time of reading under LCG and reading under HCG is the same or approximately the same, and therefore, the frame rate during video shooting before and after the above-mentioned switching can be made constant or approximately constant.
  • reading at the same gain includes reading the reset voltage and reading the signal voltage, and in correlated multi-sampling (CMS), the number of sampling times for reading the reset voltage is the same as the number of sampling times for reading the signal voltage.
  • CMS correlated multi-sampling
  • the number of sampling times for reading the reset voltage is made the same as the number of sampling times for reading the signal voltage, thereby appropriately suppressing the influence of noise (random noise, etc.) in the read signal, thereby further improving the quality of the captured image.
  • the imaging device 100 of the present embodiment includes an optical system 101 a and a solid-state imaging element 1 disposed at an image forming position of the optical system 101 a .
  • the imaging device 100 it is possible to suppress degradation in the quality of the captured image while ensuring a wider dynamic range in the captured image.
  • the solid-state imaging element 1 and the imaging device 100 including the solid-state imaging element 1 of the present invention are not limited to the above-described embodiments.
  • Various changes can be made within the scope of the present invention.
  • the structure of another embodiment can be added to the structure of a certain embodiment, and a part of the structure of a certain embodiment can be replaced with the structure of another embodiment.
  • a part of the structure of a certain embodiment can be deleted.
  • the number of samplings of the correlated multi-sampling in the solid-state imaging element 1 of the above embodiment is 2 for each of the reset voltage reading and the signal voltage reading, but the present invention is not limited to this configuration.
  • the number of samplings of the reset voltage reading under LCG and the number of samplings of the signal voltage reading under LCG may be 3 or more.
  • the SNR height difference ⁇ at the boundary between the signal obtained by reading under LCG and the signal obtained by reading under HCG is suppressed to 2 dB.
  • the sampling number of the reset voltage reading at the same gain is the same as the sampling number of the signal voltage reading, but the present invention is not limited to this configuration.
  • the sampling number of the reset voltage reading at the same gain and the sampling number of the signal voltage reading may be different.
  • the number of samplings for reading the signal voltage at the same gain is greater than the number of samplings for reading the reset voltage. In this way, by making the number of samplings for reading the signal voltage greater than the number of samplings for reading the reset voltage in the correlated multi-sampling, it is possible to improve the image quality of the captured image (to a certain extent) while suppressing the reading time in the solid-state imaging element 1.
  • correlated multi-sampling is performed in the reading under any one of the gains of LCG and HCG, but the present invention is not limited to this configuration. Correlated multi-sampling may also be performed in the reading under each gain. For example, as shown in FIG. 11 , correlated multi-sampling may also be performed in the reading under LCG and the reading under HCG.
  • the correlated multi-sampling reading is switched between readings at different gains, but the present invention is not limited to this configuration.
  • the correlated multi-sampling reading may be fixed to, for example, reading at LCG.
  • the read gain when reading the voltage signal is two types (LCG and HCG), but it may be three or more types.
  • correlated multi-sampling can be performed in the reading at the lowest reading gain among the multiple readings.
  • correlated multi-sampling is performed at least for the reading at the lowest reading gain, so that the SNR difference at the boundary (boundary of illumination from the object) between the signal obtained by reading at the lowest reading gain and the signal obtained by reading at a reading gain one level lower than the lowest reading gain is suppressed, thereby ensuring a wider dynamic range while suppressing the degradation of image quality.
  • correlated multi-sampling can be performed in at least one reading except for the reading at the highest reading gain among the multiple readings. According to the above configuration, the SNR difference at at least one point is suppressed, thereby suppressing the degradation of image quality while ensuring a wider dynamic range.
  • correlated multi-sampling can be performed in at least one of the multiple readings.
  • the difference in SNR at at least one point can be suppressed, or the influence of noise (random noise, etc.) in the signal read by the highest reading gain can be suppressed, so that it is possible to suppress the degradation of image quality while ensuring a wider dynamic range.
  • the ratio (gain ratio) of LCG to HCG in the solid-state imaging element 1 of the above embodiment is, for example, 1:64, but is not limited to this configuration.
  • the gain ratio may also be other gain ratios such as 1:4 or 1:8.
  • the larger the gain ratio the larger the SNR difference ⁇ . Therefore, by performing correlated multisampling, a significant effect is obtained from the aspect of suppressing the SNR difference ⁇ .
  • the imaging device 100 can be configured as follows: it has an exposure control unit 102A connected to the solid-state imaging element 1, and the solid-state imaging element 1 is provided with multiple combinations of readings for performing correlated multiple sampling. When shooting, the exposure control unit 102A indicates the best combination among the above multiple combinations to the solid-state imaging element 1.
  • the exposure control unit 102A selects the combination with the best image quality as the best combination from the set multiple combinations from the viewpoint of being able to suppress the degradation of the image quality of the captured image while ensuring a wider dynamic range.
  • the exposure control unit 102A automatically selects the correlated multi-sampling reading.

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Abstract

本发明涉及一种固体拍摄元件，其特征在于，通过不同的读取增益对同一曝光的信号进行多次读取，在多次读取中的最低读取增益下的读取中，进行相关多重采样。

Description

固体拍摄元件、以及具备固体拍摄元件的拍摄装置 技术领域
本发明涉及固体拍摄元件、以及具备固体拍摄元件的拍摄装置。
背景技术
以往以来，在数码相机、数码摄像机、智能手机等具备拍摄功能的拍摄装置中使用的CCD(Charge Coupled Device)、CMOS(Complementary Metal Oxide Semiconductor)图像传感器等固体拍摄元件中，已知有通过对同一曝光的信号进行高读取增益下的读取和低读取增益下的读取从而实现了高动态范围的所谓的双转换增益方式的固体拍摄元件(US7075049B2)。
近年，要求更宽的动态范围(高动态范围)，因此，考虑了在上述的双转换增益方式的固体拍摄元件中进一步增大高读取增益与低读取增益之比(增益比)。
然而，如果进一步增大高读取增益与低读取增益之比，则在通过高读取增益下的读取得到的信号与通过低读取增益下的读取得到的信号的边界部(来自被拍摄物的照度的边界部)产生SNR高低差(SNR dip)(参照图5)，例如，拍摄亮度平缓地变化的被拍摄物(无色的墙壁、天空)时，由于信号的分散量不同而导致在拍摄图像中的与上述SNR高低差对应的区域产生假的分界线等，拍摄图像的品质劣化。
现有技术文献
专利文献
专利文献1：US7075049B2。
发明内容
发明要解决的问题
因此，本发明的课题在于，提供一种固体拍摄元件、以及具备固体拍摄元件的拍摄装置，该固体拍摄元件通过不同的读取增益对同一曝光的信号进行多次读取、能够在实现更宽的动态范围的同时抑制图像的劣化。
用于解决问题的方案
本发明的固体拍摄元件通过不同的读取增益对同一曝光的信号进行多次读取，
在上述多次读取中的最低读取增益下的读取中，进行相关多重采样。
另外，在上述固体拍摄元件中，
上述不同的读取增益包含上述最低读取增益和比该最低读取增益高的读取增益即高读取增益，
在上述高读取增益下的读取中，可以进行上述相关多重采样。
另外，上述固体拍摄元件可以构成为：
能够在上述最低读取增益下的读取与高读取增益下的读取之间切换进行上述相关多重采样的读取，该高读取增益是比上述最低读取增益高的读取增益采样。
另外，在上述固体拍摄元件中，
同一增益下的读取包含复位电压的读取和信号电压的读取，
在上述相关多重采样中，上述复位电压的读取的采样次数与上述信号电压的读取的采样次数可以相同。
另外，在上述固体拍摄元件中，
同一增益下的读取包含复位电压的读取和信号电压的读取，
在上述相关多重采样中，上述信号电压的读取的采样次数比上述复位电压的读取的采样次数多。
另外，本发明的固体拍摄元件通过不同的读取增益对同一曝光的信号进行多次读取，
在上述多次读取中除最高读取增益下的读取以外的至少一次读取中，进行相关多重采样。
另外，在上述固体拍摄元件中，
可以在上述多次读取中的除上述最高读取增益下的读取以外的各读取中进行上述相关多重采样。
另外，本发明的固体拍摄元件通过不同的读取增益对同一曝光的信号进行多次读取，
在上述多次读取中的至少一次读取中，进行相关多重采样。
另外，本发明的拍摄装置具备：
光学系统、以及
配置于上述光学系统的成像位置的上述任意固体拍摄元件，
另外，上述拍摄装置具备与上述固体拍摄元件连接的曝光控制单元，
上述固体拍摄元件中，设有多个进行上述相关多重采样的读取的组合，
上述曝光控制单元可以在拍摄时，对上述固体拍摄元件指示上述多个组合中的最佳的上述组合。
附图说明
图1是本实施方式的拍摄装置的功能块图。
图2是示出上述拍摄装置所具备的固体拍摄元件的构成的图。
图3是上述固体拍摄元件所具备的像素的电路图。
图4是用于对上述像素下的电压信号的读取进行说明的图。
图5是示出在不进行相关多重采样的固体拍摄元件中读取电压信号时的来自被拍摄物的照度与SN的关系的图。
图6是示出在通过最低读取增益下的读取进行采样次数为2次的相关多重采样的固体拍摄元件中读取电压信号时的来自被拍摄物的照度与SN的关系的图。
图7是用于对上述像素下的电压信号的读取进行说明的图。
图8是用于对另一个实施方式的像素下的电压信号的读取进行说明的图。
图9是示出在通过最低读取增益下的读取进行采样次数为4次的相关多重采样的固体拍摄元件中读取电压信号时的来自被拍摄物的照度与SN的关系的图。
图10是用于对另一个实施方式的像素下的电压信号的读取进行说明的图。
图11是用于对另一个实施方式的像素下的电压信号的读取进行说明的图。
具体实施方式
本发明的固体拍摄元件通过不同的读取增益对同一曝光的信号进行多次读取，
在上述多次读取中的最低读取增益下的读取中，进行相关多重采样。
根据上述构成，至少对最低读取增益下的读取进行相关多重采样，因此，通过最低读取增益下的读取得到的信号与通过比该最低读取增益低一级的读取增益下的读取得到的信号的边界部(来自被拍摄物的照度的边界部)处的SNR高低差得以抑制(例如，参照图6、图9)，由此，能够在确保更宽的动态范围的同时抑制拍摄图像的画质劣化。
另外，在上述固体拍摄元件中，
上述不同的读取增益包含上述最低读取增益和比该最低读取增益高的读取增益即高读取增益，
在上述高读取增益下的读取中，可以进行上述相关多重采样。
根据上述构成，通过高读取增益读取的信号中的噪声(随机噪声等)的影响得以抑制，拍摄图像的画质提高。
另外，上述固体拍摄元件可以构成为：
能够在上述最低读取增益下的读取与高读取增益下的读取之间切换进行上述相关多重采样的读取，该高读取增益是比上述最低读取增益高的读取增益采样。
根据上述构成，在拍摄中需要高动态范围的场景中，切换成在最低读取增益下的读取中进行相关多重采样，由此，通过最低读取增益下的读取得到的信号与通过高读取增益下的读取得到的信号的边界部(来自被拍摄物的照度的边界部)处的SNR高低差得以抑制，由此，能够在确保更宽的动态范围的同时抑制拍摄图像的画质劣化。
另一方面，在拍摄中不需要高动态范围的场景中，切换成在高读取增益下的读取中进行相关多重采样，由此，通过高读取增益读取的信号中的噪声(随机噪声等)的影响得以抑制，由此，拍摄图像的画质(低照度侧的画质)提高。
而且，通过设为切换进行相关多重采样的读取的构成，即使在任一增益下的读取中进行相关多重采样，最低读取增益下的读取与高读取增益下的读取的读取时间的合计均相同或大致相同，因此，能够使上述切换前后的视频拍摄时的帧率一定或大致一定。
另外，在上述固体拍摄元件中，
同一增益下的读取包含复位电压的读取和信号电压的读取，
在上述相关多重采样中，上述复位电压的读取的采样次数与上述信号电压的读取的采样次数可以相同。
如此地，在相关多重采样中，使复位电压的读取的采样次数与信号电压的读取采样次数相同，由此，读取的信号中的噪声(随机噪声等)的影响得以适当地抑制，由此，拍摄图像的画质进一步提高。
另外，在上述固体拍摄元件中，
同一增益下的读取包含复位电压的读取和信号电压的读取，
在上述相关多重采样中，上述信号电压的读取的采样次数可以比上述复位电压的读取的采样次数多。
如此地，通过在相关多重采样中，使信号电压的读取的采样次数比复位电压的读取的采样次数多，能够在谋求拍摄图像的画质提高的同时抑制读取时间。
另外，本发明的固体拍摄元件通过不同的读取增益对同一曝光的信号进行多次读取，
在上述多次读取中除最高读取增益下的读取以外的至少一次读取中，进行相关多重采样。
根据上述构成，至少一处的SNR高低差得以抑制，由此，能够在确保更宽的动态范围的同时抑制拍摄图像的画质劣化。
另外，本发明的固体拍摄元件通过不同的读取增益对同一曝光的信号进行多次读取，
在上述多次读取中的至少一次读取中，进行相关多重采样。
根据上述构成，至少一处的SNR高低差得以抑制，或者通过最高读取增益读取的信号中的噪声(随机噪声等)的影响得以抑制，因此，能够在确保更宽的动态范围的同时抑制拍摄图像的画质劣化。
另外，本发明的拍摄装置具备：
光学系统、以及
配置于上述光学系统的成像位置的上述任意固体拍摄元件。
根据上述构成，能够在得到的拍摄图像中，在确保更宽的动态范围的同时抑制画质的劣化。
另外，上述拍摄装置具备与上述固体拍摄元件连接的曝光控制单元，
上述固体拍摄元件中，设有多个进行上述相关多重采样的读取的组合，
上述曝光控制单元可以在拍摄时，对上述固体拍摄元件指示上述多个组合中的最佳的上述组合。
根据上述构成，通过曝光控制单元自动选择进行相关多重采样的读取。
根据以上的固体拍摄元件、具备固体拍摄元件的拍摄装置，能够在通过不同的读取增益对同一曝光的信号进行多次读取的固体拍摄元件中，在实现更宽的动态范围的同时抑制图像的劣化。
以下，参照附图对本发明的一个实施方式进行说明。
如图1所示，拍摄装置具备：光学系统101a、和配置于光学系统101a的成像位置的固体拍摄元件1，该拍摄装置能够对数码相机、智能手机、平板设备等对象物进行拍摄，本实施方式的拍摄装置100例如为智能手机。
该拍摄装置100具备：拍摄部101、和控制部102。另外，拍摄装置100还具备：非易失性存储器103、操作用存储器104、操作部105、显示部106、存储介质107、连接部108、近距离无线通信部109、公共网络连接部110、麦克风111以及扬声器112。
拍摄部101在控制部102的控制下，在将由拍摄部101所具有的光学系统101a成像的被拍摄物的像转换成电信号后，进行噪声降低处理等，将数字数据作为输出图像的图像数据输出。具体而言，拍摄部101具有：由透镜等至少一个光学元件构成的光学系统101a、和将通过该光学系统101a成像的被拍摄物(拍摄对象物)的像转换成电信号的固体拍摄元件1。
固体拍摄元件1例如嵌入智能手机、数码相机等，是用于拍摄被拍摄物的元件，本实施方式的固体拍摄元件1例如为CMOS图像传感器。在该固体拍摄元件1中，通过不同的读取增益(电压转换增益)对同一曝光的信号进行多次读取，在上述多次读取中的最低读取增益下的读取中，进行相关多重采样(CMS)。
上述不同的读取增益包含最低读取增益和比该最低读取增益高的读取增益即高读取增益，本实施方式的固体拍摄元件1构成为：能够在最低读取增益下的读取与高读取增益下的读取之间切换进行相关多重采样的读取。
具体而言，如图2所示，固体拍摄元件1具有：配置成矩阵状的多个像素(pixel)2、相对于矩阵状的像素组配置于每行并且分别在行方向(图2中的左右方向)上延伸的多个行信号线3、配置于每列并且分别在列方向(图2中的上下方向)上延伸的多个列信号线4、以及将这些多个行信号线3与多个列信号线4连接的信号处理部5。
如图3所示，配置成矩阵状的多个像素2分别具备：光电二极管等的光电转换元件21、传送通过光电转换元件21生成的信号电荷的浮动点22、能够保持信号电荷的保持容量23、将光电转换元件21与浮动点22连接的传送晶体管24、将浮动点22与保持容量23连接的保持开关晶体管25、将保持容量23与复位电源VDD1连接的复位晶体管26、具有放大晶体管27并且将浮动点22的电压信号放大的源极跟随器SF、以及将放大晶体管27与列信号线4连接的选择晶体管28。
本实施方式的固体拍摄元件1是通过保持开关晶体管25的ON·OFF的切换将读取增益(电压转换增益/变换增益)在最低读取增益与比该最低读取增益高的读取增益即高读取增益之间切换的所谓的双转换增益(DCG)方式的固体拍摄元件1，上述读取增益是通过源极跟随器SF将在各像素2中从光电转换元件21传送至浮动点22的信号电荷作为电压信号读取时的读取增益。本实施方式的固体拍摄元件1中的最低读取增益(Low conversion gain：LCG)与高读取增益(High conversion gain：HCG)之比 (增益比)例如为1：64。另外，本实施方式的固体拍摄元件1中的“读取”可以是模拟的读取和AD转换后的读取中的任一种。
该固体拍摄元件1在同一增益(LCG或HCG)下的读取中分别进行复位电压的读取和信号电压的读取。
具体而言，对于固体拍摄元件1的一次曝光(拍摄)，在各像素2中，进行作为浮动点22被复位的状态下的电压信号的复位电压的读取、和作为在读取该复位电压之后浮动点22从光电转换元件21传送了信号电荷的状态下的电压信号的信号电压的读取作为同一增益(LCG或HCG)下的读取，分别生成这些信号电压与复位电压的差值信号。即，固体拍摄元件1在来自各像素2的读取中进行所谓的相关双重采样(CDS)。
以上的固体拍摄元件1对每行进行配置成矩阵状的各像素2中的HCG下的电压信号的读取和LCG下的电压信号的读取。然后，在该每行的电压信号的读取中，基于来自控制部102的指示，通过HCG下的读取和LCG下的读取中的任一种进行相关多重采样(Correlated Multiple Sampling，CMS)，该CMS是信号采样方式的一种，通过对复位电平电压和信号电平电压进行多次采样、加权平均、取差分，从而能够去除相关噪声成分、降低通过平均化效果导致的低频噪声、随机噪声。
具体而言，控制部102在拍摄中进行自动曝光时，例如，判定为拍摄结果图像上的一定面积暗部缺失、高光溢出，判断需要高动态范围的场景时，固体拍摄元件1根据控制部(曝光控制单元)102的指示将相关多重采样的对象切换为LCG下的读取。此时，在固体拍摄元件1中，相关多重采样中的LCG下的复位电压的读取的采样次数与LCG下的信号电压的读取的采样次数相同。在本实施方式的固体拍摄元件1中，相关多重采样中的LCG下的复位电压的读取的采样次数与LCG下的信号电压的读取的采样次数分别为2次。
更具体而言，对于各像素2的通过光电转换元件21生成的同一曝光的信号，在配置成矩阵状的多个像素2中，对每行进行2次(即，相关多重采样中的复位电压的采样为2次)LCG下的复位电压的读取(图4的LCG Ref ADC1、2)采样，进行1次HCG下的复位电压的读取(图4的HCG Ref ADC)，进行1次HCG下的信号电压的读取(图4的HCG Sig ADC)，进行)2次(即，相关多重采样中的信号电压的采样为2次)LCG下的信号电压的读取(图4的LCG Sig ADC1、2采样。另外，图4是示意性地示出每行的读取的步骤的图，各步骤中的左右方向的长度相当于读取时间的长度。图7、图8、图10、及图11也同样。
然而，固体拍摄元件1对经相关多重采样的、即经多次(在本实施方式的实例中为2次)采样的LCG的复位电压和信号电压分别进行了平均后，进行平均的复位电压与平均的信号电压的差值信号的生成(即，相关双重采样)，并且进行HCG的复位电压与信号电压的差值信号的生成(相关双重采样)。
此时，在LCG下的读取中，读取增益低，因此，随机噪声等影响变大，但是通过使用通过相关多重采样进行多次采样并进行了平均的信号来生成图像信号，在LCG下的读取中，与不进行相关多重采样的情况相比，LCG下的读取中的随机噪声等噪声的影响得以抑制，由此，能够减小通过LCG下的读取得到的信号与通过HCG下的读取得到的信号的边界部(来自被拍摄物的照度的边界部)处的SNR高低差(SNR dip)α(参照图6)。另外，在图6中，SNR高低差α的右侧的图表示出LCG下的读取信号，SNR高低差α的左侧的图表示出HCG下的读取信号。
例如，本实施方式的固体拍摄元件1(LCG下的复位电压和信号电压的各采样次数分别为2次的情况：参照图6)与不进行相关多重采样的情况(参照图5)相比，将SNR高低差α从6dB抑制为4dB。另外，图5及图6是将纵轴设为SNR[dB]、并将横轴设为来自被拍摄物的照度[lux]的图表。图9也同样。
另一方面，控制部102在拍摄中判断为不需要高动态范围的场景时，固体拍摄元件1根据来自控制部(曝光控制单元)102的指示将相关多重采样的对象切换成HCG下的读取。此时，固体拍摄元件1与在LCG下的读取中进行相关多重采样时相同，相关多重采样中的HCG下的复位电压的读取的采样次数与HCG下的信号电压的读取的采样次数相同。在本实施方式的固体拍摄元件1中，相关多重采样中的HCG下的复位电压的读取的采样次数与HCG下的信号电压的读取的采样次数分别为2次。
更具体而言，对各像素2的通过光电转换元件21生成的同一曝光的信号，在配置成矩阵状的多个像素2中，对每行进行1次LCG下的复位电压的读取，进行2次(即，相关多重采样中的复位电压的采样为2次)HCG下的复位电压的读取采样，进行2次(即，相关多重采样中的信号电压的采样为2次)HCG下的信号电压的读取采样，进行1次LCG下的信号电压的读取(参照图7)。
然后，固体拍摄元件1进行LCG的复位电压和信号电压的相关双重采样，将经相关多重采样的、即经多次(在本实施方式的实例中为2次)采样的HCG的复位电压和信号电压分别进行了平均后，进行平均的复位电压和平均的信号电压的相关双重采样。
此时，在HCG下的读取中，使用通过相关多重采样进行多次采样并进行平均而得到的信号来生成图像信号，由此，在HCG下的读取中，与不进行相关多重采样的情况相比，HCG下的读取中的随机噪声等噪声的影响得以抑制，由此，图6的HCG下的读取信号中的照度小的一侧的画质提高。
返回至图1，控制部102按照输入的信号、程序来控制拍摄装置100的各部。另外，控制部102由从固体拍摄元件1输出的信号生成拍摄图像(图像数据)，并向显示部106输出。另外，本实施方式的控制部102具有曝光控制单元102A，该曝光控制单元102A对固体拍摄元件1指示通过LCG下的读取和HCG下的读取中的哪一种读取进行相关多重采样。
非易失性存储器103是电可擦/可存储的非易失性存储器。本实施方式的非易失性存储器103存储作为控制部102执行的基本软件的OS(操作系统)、以及与该OS协作地实现应用功能的应用程序。
操作用存储器104被用作显示部106的图像显示用存储器、及控制部102的操作区域等。
操作部105用于供用户等输入对拍摄装置100的指示。本实施方式的操作部105具有用于指示拍摄装置100的电源的ON/OFF的电源按钮、及形成于显示部106的触摸面板等。
显示部106进行拍摄图像(图像数据)的显示(向外部的输出)、以及用于操作的文字显示等。
存储介质107存储从拍摄部101输出的图像数据。
连接部108是用于与外部设备连接的接口。拍摄装置100通过该连接部108与外部设备交换数据。
近距离无线通信部109是用于进行近距离无线通信的通信单元。近距离无线通信部109由用于对用于无线通信的天线和无线信号进行处理的调制解调电路、通信控制器构成。
公共网络连接部110是用于进行公共无线通信的接口。拍摄装置100通过该公共网络连接部110与其他设备进行用于通话的通信。此时，控制部102通过麦克风111及扬声器112进行声音信号的输入输出，由此实现上述通话。本实施方式的公共网络连接部110是天线，控制部102通过该天线与公共网络连接。
以上的拍摄装置100的固体拍摄元件1通过不同的读取增益对同一曝光的信号进行多次读取，在多次读取中的最低读取增益(LCG)下的读取中，进行相关多重采样(CMS)。
如此地，至少对LCG下的读取进行相关多重采样，因此，通过LCG下的读取得到的信号与通过该LCG的低一级的读取增益(在本实施方式的实例中为HCG)下的读取得到的信号的边界部(来自被拍摄物的照度的边界部)处的SNR高低差α得以抑制(例如，参照图5及图6的符号α)。由此，能够在确保更宽的动态范围(HDR)的同时抑制拍摄图像的画质劣化。
另外，在本实施方式的固体拍摄元件1中，上述不同的读取增益包含最低读取增益(LCG)和比该LCG高的读取增益即高读取增益(HCG)，在HCG下的读取中，进行相关多重采样(CMS)。
根据上述构成，HCG下读取的信号中的噪声(随机噪声等)的影响得以抑制，画质提高。
另外，本实施方式的固体拍摄元件1构成为：能够在最低读取增益(LCG)下的读取与比LCG高的读取增益即高读取增益(HCG)下的读取之间切换进行相关多重采样(CMS)的读取。
根据上述构成，在拍摄中需要高动态范围的场景中，切换成在LCG下的读取中进行相关多重采样，由此，通过LCG下的读取得到的信号与通过HCG下的读取得到的信号的边界部(来自被拍摄物的照度的边界部)处的SNR高低差α得以抑制，由此，能够在确保更宽的动态范围的同时抑制拍摄图像的画质劣化。
另一方面，在拍摄中不需要高动态范围的场景中，切换成HCG下的读取中进行相关多重采样，由此，HCG下读取的信号中的噪声(随机噪声等)的影响得以抑制，由此，拍摄图像的画质(照度小的一侧的画质)提高。
而且，通过设为切换进行相关多重采样的读取的构成，即使在任意读取增益(电压转换增益)下的读取中进行相关多重采样，LCG下的读取与HCG下的读取的读取时间的合计相同或大致相同，因此，能够使上述切换前后的视频拍摄时的帧率一定或大致一定。
另外，在本实施方式的固体拍摄元件1中，同一增益(同一读取增益)下的读取包含复位电压的读取和信号电压的读取，在相关多重采样(CMS)中，复位电压的读取的采样次数与信号电压的读取的采样次数相同。
如此地，在相关多重采样中，使复位电压的读取的采样次数与信号电压的读取采样次数相同，由此，读取的信号中的噪声(随机噪声等)的影响得以适当地抑制，由此，拍摄图像的画质进一步提高。
另外，本实施方式的拍摄装置100具备：光学系统101a、和配置于光学系统101a的成像位置的固体拍摄元件1。
根据该拍摄装置100，能够在所得到的拍摄图像中，在确保更宽的动态范围的同时抑制拍摄图像的画质劣化。
另外，本发明的固体拍摄元件1及具备固体拍摄元件1的拍摄装置100不限于上述实施方式，当然 可以在不脱离本发明主旨的范围内施加各种变更。例如，能够在某一个实施方式的构成上追加另一个实施方式的构成，另外，能够将某一个实施方式的构成的一部分替换为另一个实施方式的构成。进一步的，能够删除某一个实施方式的一部分构成。
上述实施方式的固体拍摄元件1中的相关多重采样的采样次数在复位电压的读取和信号电压的读取中分别为2次，但不限定于该构成。LCG下的复位电压的读取的采样次数和LCG下的信号电压的读取的采样次数也可以为3次以上。
LCG下的复位电压的读取的采样次数和LCG下的信号电压的读取的采样次数越多，越能够减小通过LCG下的读取得到的信号与通过HCG下的读取得到的信号的边界部(来自被拍摄物的照度的边界部)处的SNR高低差α。例如，如图8所示，在LCG下的复位电压的读取的采样次数和LCG下的信号电压的读取的采样次数分别为4次的情况下，如图9所示，通过LCG下的读取得到的信号与通过HCG下的读取得到的信号的边界部处的SNR高低差α被抑制为2dB。
另外，在上述实施方式的固体拍摄元件1中，在相关多重采样中，同一增益下的复位电压的读取的采样次数与信号电压的读取的采样次数相同，但不限定于该构成。在相关多重采样中，同一增益下的复位电压的读取的采样次数与信号电压的读取的采样次数也可以不同。
在该情况下，如图10所示，在相关多重采样中，优选同一增益下的信号电压的读取的采样次数比复位电压的读取的采样次数多。如此地，通过在相关多重采样中，使信号电压的读取的采样次数比复位电压的读取的采样次数多，能够在实现拍摄图像的画质的提高(某种程度的提高)的同时抑制固体拍摄元件1中的读取时间。
另外，在上述实施方式的固体拍摄元件1中，在LCG和HCG中的任一种增益下的读取中，进行相关多重采样，但不限定于该构成。也可以在各增益下的读取中分别进行相关多重采样。例如，如图11所示，也可以在LCG下的读取和HCG下的读取中分别进行相关多重采样。
另外，在上述实施方式的固体拍摄元件1中，在不同的增益下的读取之间切换进行相关多重采样的读取，但不限定于该构成。进行相关多重采样的读取例如也可以固定为LCG下的读取等。
另外，在上述实施方式的固体拍摄元件1中，电压信号的读取时的读取增益为两种(LCG和HCG)，但也可以为三种以上。
在该情况下，可以多次读取中的最低读取增益下的读取中进行相关多重采样。根据上述构成，至少对最低读取增益下的读取进行相关多重采样，因此，通过最低读取增益下的读取得到的信号与通过比该最低读取增益低一级的读取增益下的读取得到的信号的边界部(来自被拍摄物的照度的边界部)处的SNR高低差得以抑制，由此，能够在确保更宽的动态范围的同时抑制画质的劣化。
另外，可以在多次读取中除最高读取增益下的读取以外的至少一次读取中进行相关多重采样。根据上述构成，至少一处的SNR高低差得以抑制，由此，能够在确保更宽的动态范围的同时抑制画质的劣化。
另外，可以在多次读取中的至少一次读取中进行相关多重采样。根据上述构成，至少一处的SNR高低差得以抑制，或者通过最高读取增益读取的信号中的噪声(随机噪声等)的影响得以抑制，因此，能够在确保更宽的动态范围的同时抑制画质的劣化。
另外，上述实施方式的固体拍摄元件1中的LCG与HCG之比(增益比)例如为1：64，但不限定于该构成。例如，上述增益比也可以为1：4、1：8等其他增益比。另外，上述增益比越大，SNR高低差α越大，因此，通过进行相关多重采样，从抑制SNR高低差α的方面考虑，得到了显著的效果。
另外，拍摄装置100可以是如下构成：具备与固体拍摄元件1连接的曝光控制单元102A，固体拍摄元件1中设有多个进行相关多重采样的读取的组合，曝光控制单元102A在拍摄时，对固体拍摄元件1指示上述多个组合中的最佳的组合。
作为读取的组合的切换的例子，在LCG的增益的绝对值小、LCG与HCG的增益比大(例如为1：32以上)时这样的SNR高低差变大的条件下，基于指示进行切换下述两种的组合：使LCG的相关多重采样的采样次数比HCG多的组合、另外在LCG的增益的绝对值大(例如为4倍以上这样的)的暗场景中进行高动态范围拍摄这样的想要提高暗处的SNR的情况下使HCG的相关多重采样的采样次数比LCG大这样的组合。即，曝光控制单元102A是以能够在确保更宽的动态范围的同时抑制拍摄图像的画质劣化的观点来看，由从所设定的多个组合中，选择画质最好的组合作为最佳组合。
根据上述构成，通过曝光控制单元102A自动地选择进行相关多重采样的读取。
为了表现本发明，以上参照附图通过实施方式对本发明进行了适当且充分的说明，但是本领域的技术人员应该认识到，变更和/或改良上述的实施方式是容易实现的。因此，只要本领域技术人员实施的变更方式或改良方式不脱离权利要求书所记载的权利要求书的范围的水平，则该变更方式或该改良方式可以解释为包含于该权利要求书的范围中。
附图标记说明：
1…固体拍摄元件、2…像素、21…光电转换元件、22…浮动点、23…保持容量、24…传送晶体管、
25…保持开关晶体管、26…复位晶体管、27…放大晶体管、28…选择晶体管、3…行信号线、4…列信号线、5…信号处理部、100…拍摄装置、101…拍摄部、101a…光学系统、102…控制部、102A…曝光控制单元、103…非易失性存储器、104…操作用存储器、105…操作部、106…显示部、107…存储介质、108…连接部、109…近距离无线通信部、110…公共网络连接部、111…麦克风、112…扬声器、SF…源极跟随器、α…SNR高低差(SNR dip)。

Claims (10)

  1. 一种固体拍摄元件，其通过不同的读取增益对同一曝光的信号进行多次读取，
    在所述多次读取中的最低读取增益下的读取中，进行相关多重采样。
  2. 根据权利要求1所述的固体拍摄元件，其中，
    所述不同的读取增益包含所述最低读取增益和比该最低读取增益高的读取增益即高读取增益，
    在所述高读取增益下的读取中，进行所述相关多重采样。
  3. 根据权利要求1或2所述的固体拍摄元件，其构成为：
    能够在所述最低读取增益下的读取与高读取增益下的读取之间切换进行所述相关多重采样的读取，所述高读取增益为比所述最低读取增益高的读取增益。
  4. 根据权利要求1～3中任一项所述的固体拍摄元件，其中，
    同一增益下的读取包含复位电压的读取和信号电压的读取，
    在所述相关多重采样中，所述复位电压的读取的采样次数与所述信号电压的读取的采样次数相同。
  5. 根据权利要求1～3中任一项所述的固体拍摄元件，其中，
    同一增益下的读取包含复位电压的读取和信号电压的读取，
    在所述相关多重采样中，所述信号电压的读取的采样次数比所述复位电压的读取的采样次数多。
  6. 一种固体拍摄元件，其通过不同的读取增益对同一曝光的信号进行多次读取，
    在所述多次读取中除最高读取增益下的读取以外的至少一次读取中，进行相关多重采样。
  7. 根据权利要求6所述的固体拍摄元件，其中，
    在所述多次读取中除所述最高读取增益下的读取以外的各读取中，进行所述相关多重采样。
  8. 一种固体拍摄元件，其通过不同的读取增益对同一曝光的信号进行多次读取，
    在所述多次读取中的至少一次读取中，进行相关多重采样。
  9. 一种拍摄装置，其具备：
    光学系统、以及
    配置于所述光学系统的成像位置的权利要求1～8中任一项所述的固体拍摄元件。
  10. 根据权利要求9所述的拍摄装置，其具备与所述固体拍摄元件连接的曝光控制单元。
    所述固体拍摄元件中，设有多个进行所述相关多重采样的读取的组合，
    所述曝光控制单元在拍摄时，对所述固体拍摄元件指示所述多个组合中的最佳的所述组合。
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