WO2020061883A1 - 像素单元和图像传感器 - Google Patents

像素单元和图像传感器 Download PDF

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Publication number
WO2020061883A1
WO2020061883A1 PCT/CN2018/107863 CN2018107863W WO2020061883A1 WO 2020061883 A1 WO2020061883 A1 WO 2020061883A1 CN 2018107863 W CN2018107863 W CN 2018107863W WO 2020061883 A1 WO2020061883 A1 WO 2020061883A1
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WO
WIPO (PCT)
Prior art keywords
tube
source follower
switching device
floating diffusion
pixel unit
Prior art date
Application number
PCT/CN2018/107863
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English (en)
French (fr)
Inventor
徐泽
Original Assignee
深圳市大疆创新科技有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by 深圳市大疆创新科技有限公司 filed Critical 深圳市大疆创新科技有限公司
Priority to CN201880036761.9A priority Critical patent/CN110741629A/zh
Priority to PCT/CN2018/107863 priority patent/WO2020061883A1/zh
Publication of WO2020061883A1 publication Critical patent/WO2020061883A1/zh
Priority to US17/214,565 priority patent/US20210235026A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14641—Electronic components shared by two or more pixel-elements, e.g. one amplifier shared by two pixel elements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/70—SSIS architectures; Circuits associated therewith
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/70—SSIS architectures; Circuits associated therewith
    • H04N25/76—Addressed sensors, e.g. MOS or CMOS sensors
    • H04N25/77—Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
    • H04N25/70—SSIS architectures; Circuits associated therewith
    • H04N25/76—Addressed sensors, e.g. MOS or CMOS sensors
    • H04N25/77—Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
    • H04N25/771—Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components comprising storage means other than floating diffusion
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14603—Special geometry or disposition of pixel-elements, address-lines or gate-electrodes

Definitions

  • the present application relates to the field of image signal processing, and more particularly, to a pixel unit and an image sensor.
  • image sensors are widely used in various fields.
  • An image sensor usually consists of multiple pixel units.
  • the signal-to-noise ratio of the image signal output by the pixel unit is an important index of the pixel unit.
  • the signal-to-noise ratio of the image signal output by the pixel unit is not stable, and may change with factors such as the environment and is difficult to control.
  • the present application provides a pixel unit and an image sensor, which can effectively control the signal-to-noise ratio of an image signal output by the pixel unit.
  • a pixel unit including: a photoelectric conversion device; a transmission tube; a reset tube; a first source follower and a second source follower, the first source follower and the second source
  • the gates of the electrode followers are electrically connected to the floating diffusion region between the transmission tube and the reset tube, and the sources of the first source follower and the second source follower are selected by
  • the pass tube is connected to the row selection line.
  • a switching device is connected to the second source follower. When the switching device is turned on, the second source follower and the first source follower work simultaneously. ; When the switching device is turned off, the first source follower works, and the second source follower does not work.
  • an image sensor including: a pixel unit array. At least one pixel unit in the pixel unit array includes: a photoelectric conversion device; a transmission tube; a reset tube; a first source follower and a second source Followers, the gates of the first source follower and the second source follower are electrically connected to a floating diffusion region between the transmission tube and the reset tube, and the first source electrode
  • the follower and the source of the second source follower are both connected to a row selection line through a gate; a switching device is connected to the second source follower, and when the switching device is turned on, the A second source follower works simultaneously with the first source follower; when the switching device is turned off, the first source follower works, and the second source follower does not work;
  • a control circuit And is connected to a switching device in the pixel unit, and is configured to control whether the second source follower and the first source follower work at the same time.
  • a pixel unit including: a photoelectric conversion device; a first transmission tube; a reset tube; a source follower, a gate of the source follower, the first transmission tube, and the reset tube.
  • the floating diffusion between the two is electrically connected, and the source of the source follower is connected to the row selection line through a gate tube; a second transmission tube, the first and second electrodes of the second transmission tube are respectively connected to
  • the output end of the photoelectric conversion device is electrically connected to the floating diffusion region, wherein the first pole source and the second pole drain; or the first pole drain and the second pole source Pole; a switching device connected to the second transmission tube, when the switching device is on, the second transmission tube and the first transmission tube work simultaneously; when the switching device is off, the The first transfer tube works, and the second transfer tube does not work.
  • an image sensor including: a pixel unit array. At least one pixel unit in the pixel unit array includes: a photoelectric conversion device; a first transmission tube; a reset tube; a source follower, and the source electrode.
  • the gate of the follower is electrically connected to the floating diffusion region between the first transmission tube and the reset tube, and the source of the source follower is connected to the row selection line through a gate tube; a second transmission tube A first pole and a second pole of the second transmission tube are electrically connected to an output end of the photoelectric conversion device and the floating diffusion region, respectively, wherein the first pole is a source and the second pole is leaking Or the first pole drain and the second pole source; a switching device connected to the second transmission tube, and when the switching device is turned on, the second transmission tube is connected to the first transmission tube; A transmission tube works at the same time; when the switching device is turned off, the first transmission tube works and the second transmission tube does not work; a control circuit is connected to the switching device in the pixel unit for controlling all Whether the second transmission pipe is related to the first Transfer tubes simultaneously.
  • a trade-off can be made between the size of the source follower of the pixel unit and the charge / voltage gain of the floating diffusion region, so as to effectively control the signal-to-noise ratio of the image signal output by the pixel unit.
  • FIG. 1 is a schematic structural diagram of a conventional pixel unit.
  • FIG. 2 is a schematic structural diagram of a pixel unit provided by an embodiment of the present application.
  • FIG. 3 is an exemplary diagram of an actual layout of a pixel unit in FIG. 2.
  • FIG. 4 is a schematic structural diagram of an image sensor according to an embodiment of the present application.
  • FIG. 5 is an example diagram of an actual layout of the image sensor in FIG. 4.
  • FIG. 6 is a schematic structural diagram of a pixel unit according to another embodiment of the present application.
  • FIG. 7 is an exemplary diagram of an actual layout of a pixel unit in FIG. 6.
  • FIG. 8 is a schematic structural diagram of an image sensor according to another embodiment of the present application.
  • FIG. 9 is an example diagram of an actual layout of the image sensor in FIG. 8.
  • the image sensor may include a pixel unit (pixel) array and a signal processing circuit.
  • the area where the pixel unit array is located may be referred to as a photosensitive circuit area of the image sensor.
  • the pixel unit array may be composed of multiple pixel units, for example, it may be composed of tens or even hundreds of millions of pixel units.
  • the pixel unit may also be referred to as a photosensitive unit.
  • the pixel unit can be used to convert the received light signal into an analog signal.
  • the area where the signal processing circuit is located may also be referred to as the peripheral circuit area of the image sensor.
  • the signal processing circuit is electrically connected to the pixel unit array, and can be used to convert an analog signal output by the pixel unit array into a digital signal for representing image information collected by the pixel unit.
  • the conventional pixel unit 10 may generally include a photodiode PD, a transmission tube TX, a source follower SF, a reset tube RST, and a gate tube SEL.
  • the photodiode PD can be used to convert the received photons into electrons (ie, output photo-generated electrons). It should be understood that the photodiode PD in FIG. 1 may also be replaced with other devices having a photoelectric conversion function, such as a phototransistor, a photomultiplier, and the like.
  • the transmission tube TX (also referred to as an electron transmission tube TX or a transmission transistor TX) can be used to transmit the photo-generated electrons output by the photoelectric conversion device to the floating diffusion region FD located between the transmission tube TX and the reset tube RST.
  • the floating diffusion region FD can perform a charge-voltage conversion function.
  • the floating diffusion region FD can be understood as a parasitic capacitance of a transistor, and can be used to induce a corresponding voltage signal according to the amount of charge output from the transmission tube TX.
  • the reset tube RST (also referred to as a reset transistor RST) is used to reset the pixel unit so that the next signal acquisition.
  • the reset transistor is sometimes called a reset transistor.
  • the gate of the source follower SF is connected to the floating diffusion FD, and the source of the source follower SF may be connected to a row selection line (not shown in FIG. 1).
  • the source follower SF may be used to receive the voltage signal of the floating diffusion FD and generate a follow-up signal (or an output signal of the source follower SF) of the voltage signal of the floating diffusion FD.
  • the following signal can be understood as a voltage signal obtained by performing a potential shift on the voltage signal of the floating diffusion FD.
  • the gate SEL (or gate transistor SEL) can be used to receive a control signal input from an external control circuit.
  • the control circuit may be, for example, a signal processing circuit in an image sensor in which the pixel unit 10 is located.
  • the source follower SF can output a corresponding follow signal to the row selection line.
  • the transistor noise of the source follower is an important part of the overall noise of the pixel unit.
  • the source follower noise is related to the size of the source follower. Generally speaking, the larger the size of the source follower, the smaller its noise. Therefore, in order to improve the signal-to-noise ratio of the image signal, one possible implementation is to connect multiple source followers in the pixel unit in parallel to increase the size of the source follower and reduce the noise of the source follower.
  • the gate of the source follower SF is electrically interconnected with the floating diffusion FD, which means that the gate capacitance of the source follower SF is a part of the total capacitance of the floating diffusion FD.
  • the multi-source follower parallel implementation method reduces the noise of the source follower and increases the total capacitance of the floating diffusion region, thereby reducing the charge / voltage gain of the floating diffusion region. If the signal received by the photoelectric conversion device is relatively strong (such as working in a bright scene), parallel connection of multiple source followers can usually improve the signal-to-noise ratio of the image signal; however, if the signal received by the photoelectric conversion device is weak (Such as working in a dark environment), the increase in the total capacitance of the floating diffusion region caused by the parallel connection of multiple source followers may decrease the signal-to-noise ratio of the image signal output by the pixel unit.
  • the pixel unit 20 may include a photodiode PD, a transmission tube TX, a reset tube RST, a first source follower SF1, a second source follower SF2, a switching tube DCG, and a first gate tube SEL1. Second gate transistor SEL2.
  • the actual layout of the pixel unit 20 in FIG. 2 can be arranged with reference to FIG. 3.
  • the photodiode PD can also be replaced with other types of photoelectric conversion devices, such as a phototransistor or a photomultiplier tube.
  • One end of the switching tube DCG (or double gain switching tube) is connected to the transmission tube TX, and the other end of the switching tube DCG is connected to the reset tube RST, so that the floating diffusion between the transmission tube TX and the reset tube RST can be distinguished into A first floating diffusion region FD1 between the transmission tube TX and the switching tube DCG, and a second floating diffusion region FD2 between the switching tube DCG and the reset tube RST.
  • the first source follower SF1 and the second source follower SF2 are source followers connected in parallel with each other. It should be noted that the embodiment of the present application is only described by taking the pixel unit 20 including two source followers as an example. In fact, the pixel unit 20 may include more source followers.
  • the gate of the first source follower SF1 is connected to the first floating diffusion FD1 (the connections between circuit devices in this application refer to electrical connections), and the gate of the second source follower SF2 is connected to the second floating The diffusion area FD2 is connected.
  • the source of the first source follower SF1 may be connected to the row selection line through the gate SEL1, and the source of the second source follower SF2 may be connected to the row selection line through the gate SEL2.
  • the switching device DCG when the switching device DCG is turned on, the second source follower SF2 and the first source follower SF1 can work simultaneously; when the switching device DCG is turned off, the first source follower SF1 works, The second source follower SF2 does not work.
  • the switching tube DCG can also be replaced with another type of switching device, as long as it can control the line where the switching device is located to turn on and off.
  • the switching device (switching tube DCG) is located in a floating diffusion region between the transmission tube TX and the reset tube RST.
  • the specific position of the switching device is not limited in the embodiment of the present application, as long as it can control whether the second source follower SF2 and the first source follower SF1 work at the same time.
  • the switching device may be located between the floating diffusion region and the gate of the second source follower SF2.
  • the embodiment of the present application introduces a first source follower SF1 and a second source follower SF2, and uses a switching device to control whether the first source follower SF1 and the second source follower SF2 work at the same time.
  • the first source When the electrode follower SF1 and the second source follower SF2 work at the same time, it is equivalent to increasing the size of the source follower in the pixel unit 20, so that the noise of the pixel unit 20 can be reduced; when the first source follower SF1 When working, and the second source follower SF2 is not working, the gate capacitance of the first source follower SF1 will be smaller, and the capacitance of the floating diffusion region will be smaller, which can increase the charge / Voltage gain.
  • a trade-off can be made between the size of the source follower of the pixel unit and the charge / voltage gain of the floating diffusion region according to actual needs, thereby effectively controlling the signal-to-noise ratio of the image signal output by the pixel unit.
  • a dark scene and a bright scene are taken as examples to describe the control method of the pixel unit 20 in detail.
  • the transmission tube TX is turned off, and the gates of the reset tube RST and the switching tube DCG are connected to a high potential, so that the reset tube RST and the switching tube DCG are both on.
  • the drain of the reset tube RST is connected to a high potential, so that the gates SEL1 and SEL2 are both in an off state.
  • the signal is read.
  • the gate of the switching tube DCG is set to a low potential, and the switching tube DCG is turned off. At this time, the floating diffusion region FD1 is floated to a high potential. Then, the gate of the gate SEL1 is set to a high potential.
  • the source of the gate SEL1 will be at a potential value V ref with the potential of the first floating diffusion FD1 as a reference potential.
  • the transmission tube TX is then set to a high potential, thereby turning on the transmission tube TX.
  • the transmission tube TX is turned off.
  • the potential of the first floating diffusion region FD1 will decrease due to the photo-generated electrons input from the photodiode PD.
  • the source of the first source follower SF1 will fall and follow the potential of the first floating diffusion region FD1.
  • the falling potential of the first floating diffusion FD1 is V sig .
  • the voltage difference between the potential V ref and the potential V sig can be regarded as the signal value corresponding to the incident light signal, and the voltage difference can be processed by the subsequent circuit to convert the brightness and color information collected by the pixel unit. . Since only the first source follower SF1 participates in the work at this time, the total capacitance of the floating diffusion region of the pixel unit 20 is small and the charge voltage gain of the floating diffusion region is large. Therefore, even in a dark scene, the floating diffusion region The voltage signal (V ref -V sig ) is still relatively large, and the signal to noise of the image signal output by the pixel unit 20 is relatively high.
  • the transmission tube TX is turned off, and the gates of the reset tube RST and the switching tube DCG are connected to a high potential, so that both are turned on.
  • the drain of the reset tube RST is connected to a high potential, and the gates SEL1 and SEL2 are both in an off state.
  • a reading signal is started, and the gate of the reset tube RST is set to a low potential, so that the reset tube RST is turned off.
  • the floating diffusion regions FD1 and FD2 are electrically connected, the potentials are the same, and both are floated to a high potential.
  • the gates SEL1 and SEL2 are set to a high potential at the same time.
  • the sources of the gates SEL1 and SEL2 will follow the potentials of the floating diffusion regions FD1 and FD2 to be at a potential value V ref as a reference potential. Then, the transmission tube TX is set to a high potential, thereby turning on the transmission tube TX. After the photo-generated electrons output from the photodiode PD enter the floating diffusion regions FD1 and FD2, the transmission tube TX is closed, and the potentials of the floating diffusion regions FD1 and FD2 will decrease due to the photo-generated electrons output from the photodiode PD.
  • the source The sources of the followers SF1 and SF2 will follow the drop of the potentials of the floating diffusion regions FD1 and FD2 and fall, and the reduced potentiometer will be V sig .
  • the voltage difference between V ref and V sig can be used to characterize the signal value corresponding to the incident light signal.
  • the image information collected by the pixel unit can be converted.
  • the source followers SF1 and SF2 participate in the work at the same time, which is equivalent to the size of the source follower becoming larger, so the noise of the source follower is smaller, so that the signal-to-noise ratio of the image signal output by the pixel unit in a bright scene is maintained at Higher standards.
  • An embodiment of the present application further provides an image sensor.
  • the image sensor may be an image sensor based on a complementary metal oxide semiconductor (CMOS) image sensor.
  • CMOS complementary metal oxide semiconductor
  • the image sensor (or chip) can be widely used in consumer electronics, security monitoring, industrial automation, artificial intelligence, the Internet of Things and other fields.
  • the image sensor can be used to collect and organize image information and provide an information source for subsequent processing and applications.
  • the image sensor 40 may include a pixel unit array 42 and a control circuit 44.
  • One or more pixel units in the pixel unit array 42 are the pixel units 20 described above.
  • the control circuit 44 may be a signal processing circuit inside the image sensor 40.
  • the control circuit 44 may be connected to a switching device in the pixel unit 20, and is configured to control whether the second source follower SF2 and the first source follower SF1 work simultaneously through the switching device.
  • each pixel unit in the pixel unit array 42 is a pixel unit 20 as shown in FIG. 2, its actual layout can be performed with reference to the manner shown in FIG. 5. Layout.
  • a large-sized pixel unit has a large photosensitive area and a sufficient amount of light, and generally requires its photodiode PD (or other type of photoelectric conversion device) to have a larger Full well electrons.
  • a large-sized transmission tube TX needs to be designed between the photodiode PD and the floating diffusion region FD.
  • the larger transmission tube TX introduces a larger parasitic capacitance between the floating diffusion region FD and the transmission tube TX, which results in a larger total capacitance of the floating diffusion region FD and a smaller charge / voltage gain.
  • the number of electrons induced by the photodiode PD is small.
  • the voltage signal generated by the floating diffusion region FD will be smaller, thereby reducing the signal-to-noise ratio of the image signal output by the pixel unit in a dark scene.
  • an embodiment of the present application further provides a pixel unit 60.
  • the pixel unit 60 may include a photodiode PD, a first transmission tube TX1, a second transmission tube TX2, a reset tube RST, a source follower SF, a switching tube DCG, and a gate tube SEL.
  • the photodiode PD can be used to convert the received photons into electrons (ie, output photo-generated electrons).
  • the photodiode PD can also be replaced with other types of photoelectric conversion devices, such as a phototransistor or a photomultiplier tube.
  • the first pole and the second pole of the second transmission tube TX2 are electrically connected to the output end of the photodiode PD and the floating diffusion region, respectively.
  • the first pole can be the source of the second transmission tube TX2, and the second pole can be the drain of the second transmission tube TX2; or the first pole can be the drain of the second transmission tube TX2, and the second pole can be the second Source of TX2.
  • One end of the switching tube DCG (or double gain switching tube) is connected to the first transmission tube TX1, and the other end of the switching tube DCG is connected to the reset tube RST, so that the floating between the first transmission tube TX1 and the reset tube RST is floating.
  • Diffusion is divided into a first floating diffusion region FD1 located between the first transmission tube TX1 and the switching tube DCG, and a second floating diffusion region FD2 located between the switching tube DCG and the reset tube RST.
  • the second pole of the second transmission tube TX2 is connected to the second floating diffusion region FD2.
  • the switching tube DCG can also be replaced with another type of switching device, as long as it can control the line where the switching device is located to turn on and off.
  • the switching tube DCG can also be located between the second pole of the second transmission tube TX2 and the floating diffusion region (between the first transmission tube TX and RST). This can also control whether the second transmission tube TX2 is connected to the first Whether the transmission tube TX1 works at the same time.
  • the actual layout of the pixel unit 60 shown in FIG. 6 can be arranged with reference to FIG. 7. As shown in FIG. 7, the overlapping portion of the first transmission tube TX1 and the silicon of the first floating diffusion FD1 is small, and the area of the corresponding first floating diffusion FD1 is also small. The total capacitance of a floating diffusion FD1 is also small.
  • the embodiments of the present application do not specifically limit the sizes of the first transmission tube TX1 and the second transmission tube TX2.
  • the size of the second transmission tube TX2 can be set larger than the size of the first transmission tube TX1, so that When the second transmission tube TX2 is working, it can transfer as much electrons as possible to the floating diffusion area, and when the second transmission tube TX2 is not working, the effect of the first transmission tube TX1 on the total capacitance of the floating diffusion area is as small as possible. some.
  • the embodiment of the present application does not specifically limit conditions for the first transmission tube TX1 and the second transmission tube TX2 to work simultaneously, and may be selected according to actual needs. For example, when the current scene is a bright scene, the number of electrons generated by the photodiode PD is large, and the first transmission tube TX1 and the second transmission tube TX2 can be controlled to work at the same time; when the current scene is a dark scene, the photodiode PD The number of generated electrons is large, and the second transmission tube TX2 can be controlled to not work.
  • the above control operation may be performed by a control circuit other than the pixel unit 60.
  • the control circuit may be, for example, a signal processing circuit in an image sensor in which the pixel unit 60 is located.
  • a dark scene and a bright scene are taken as examples to describe the control method of the pixel unit 60 in detail.
  • the first transmission tube TX1, the second transmission tube TX2, and the gate tube SEL are controlled to be turned off.
  • the switching tube DCG and the reset tube RST are in an open state, and the drain of the reset tube RST is in a high voltage state.
  • the control switch DCG When the exposure is over, the control switch DCG is turned off and the gate SEL is turned on. At this time, the first floating diffusion FD1 is in a floating high voltage state, and the first reference voltage V is read at the source of the gate SEL. ref1 . Then, the first transmission tube TX1 can be turned on, and the electrons of the photodiode PD are transmitted to the first floating diffusion region FD1. The voltage of the first floating diffusion region FD1 will drop. At this time, the first signal voltage V sig1 is read at the source of the gate SEL, and V ref1 -V sig1 is a voltage signal corresponding to the intensity of the incident light.
  • Peripheral circuits (such as signal processing circuits) of the image sensor can be read and processed through a certain conversion to form an image. At this time, since the capacitance of the first floating diffusion region FD1 is small, the charge / voltage gain of the first floating diffusion region FD1 is high. Even in a dark scene, the image signal output by the pixel unit 60 still remains relatively stable. Good signal-to-noise ratio.
  • the first transmission tube TX1, the second transmission tube TX2, and the gate tube SEL are all turned off, the switching tube DCG and the reset tube RST are turned on, and the drain of the reset tube RST is always at a high voltage status.
  • the control reset tube RST is turned off and the gate tube SEL is turned on.
  • the first floating diffusion FD1 and the second floating diffusion area FD2 are in communication and both are in a floating high voltage state.
  • the second reference voltage V ref2 is read at the source of the gate SEL, and then the first transmission tube TX1 and the second transmission tube TX2 are turned on at the same time.
  • the electrons of the photodiode PD are transferred to the first floating diffusion region FD1 and the second floating diffusion region FD2.
  • the voltages of the first floating diffusion region FD1 and the second floating diffusion region FD2 will drop, and the second signal voltage V sig2 can be read at the source of the gate SEL.
  • V ref2 -V sig2 is the voltage signal corresponding to the intensity of the incident light.
  • Peripheral circuits (such as signal processing circuits) of the image sensor can be read and processed through a certain conversion to form an image. Due to the large number of electrons in the photodiode PD in a bright scene, turning on the first transmission tube TX1 and the second transmission tube TX2 at the same time is beneficial to quickly and completely transfer the photo-generated electrons output from the photodiode PD to the floating diffusion region.
  • the pixel structure provided in Figure 6 can achieve high charge / voltage gain and high signal-to-noise ratio in dark scenes and small signals; and also, when the signal is strong, try to fully transfer the charges, so that the final output image
  • the signal has a large dynamic range.
  • An embodiment of the present application further provides an image sensor.
  • the image sensor provided in the embodiment of the present application may be a CMOS-based image sensor.
  • the image sensor (or chip) can be widely used in consumer electronics, security monitoring, industrial automation, artificial intelligence, the Internet of Things and other fields.
  • the image sensor can be used to collect and organize image information and provide an information source for subsequent processing and applications.
  • the image sensor 80 may include a pixel unit array 82 and a control circuit 84.
  • One or more pixel units in the pixel unit array 82 are the pixel units 60 described above.
  • the control circuit 84 may be a signal processing circuit inside the image sensor 80.
  • the control circuit 84 may be connected to a switching device in the pixel unit 60, and is configured to control whether the second transmission tube TX2 and the first transmission tube TX1 work simultaneously through the switching device.
  • each pixel unit in the pixel unit array 82 is a pixel unit as shown in FIG. 7, its actual layout can be arranged with reference to the manner shown in FIG. 9. .
  • the switching tube DCG can be used to control whether the second transmission tube TX2 and the second source follower SF2 work simultaneously with the first transmission tube TX1 and the first source follower SF1.
  • the computer program product includes one or more computer instructions.
  • the computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices.
  • the computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions may be from a website site, computer, server, or data center Transmission by wire (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.) to another website site, computer, server, or data center.
  • the computer-readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server, a data center, and the like that includes one or more available medium integration.
  • the usable medium may be a magnetic medium (for example, a floppy disk, a hard disk, a magnetic tape), an optical medium (for example, a digital video disc (DVD)), or a semiconductor medium (for example, a solid state disk (SSD)), etc. .
  • a magnetic medium for example, a floppy disk, a hard disk, a magnetic tape
  • an optical medium for example, a digital video disc (DVD)
  • DVD digital video disc
  • SSD solid state disk
  • the disclosed systems, devices, and methods may be implemented in other ways.
  • the device embodiments described above are only schematic.
  • the division of the unit is only a logical function division.
  • multiple units or components may be combined or Can be integrated into another system, or some features can be ignored or not implemented.
  • the displayed or discussed mutual coupling or direct coupling or communication connection may be indirect coupling or communication connection through some interfaces, devices or units, which may be electrical, mechanical or other forms.
  • the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, may be located in one place, or may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the objective of the solution of this embodiment.
  • each functional unit in each embodiment of the present application may be integrated into one processing unit, or each of the units may exist separately physically, or two or more units may be integrated into one unit.

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Abstract

提供一种像素单元和图像传感器。该像素单元包括光电转换器件；传输管；复位管；第一源极跟随器和第二源极跟随器，第一源极跟随器和第二源极跟随器的栅极均与传输管和复位管之间的浮置扩散区电连接，第一源极跟随器和第二源极跟随器的源极均通过选通管与行选择线相连；开关器件，与第二源极跟随器相连，当开关器件导通时，第二源极跟随器与第一源极跟随器同时工作；当开关器件断开时，第一源极跟随器工作，第二源极跟随器不工作。本申请可以根据实际需要，在像素单元的源极跟随器的尺寸和浮置扩散区的电荷/电压增益之间进行权衡，从而有效控制像素单元输出的图像信号的信噪比。

Description

像素单元和图像传感器
版权申明
本专利文件披露的内容包含受版权保护的材料。该版权为版权所有人所有。版权所有人不反对任何人复制专利与商标局的官方记录和档案中所存在的该专利文件或者该专利披露。
技术领域
本申请涉及图像信号处理领域，并且更为具体地，涉及一种像素单元和图像传感器。
背景技术
目前，很多领域都需要采集图像信息，如消费电子领域，安防监控领域，工业自动化领域，人工智能领域以及物联网领域。因此，图像传感器被广泛应用于各个领域。
图像传感器通常由多个像素单元组成。像素单元输出的图像信号的信噪比是像素单元的一项重要指标。像素单元输出的图像信号的信噪比并不稳定，可能会随着环境等因素的变化而变化，难以控制。
发明内容
本申请提供一种像素单元和图像传感器，可以有效控制像素单元输出的图像信号的信噪比。
第一方面，提供一种像素单元，包括：光电转换器件；传输管；复位管；第一源极跟随器和第二源极跟随器，所述第一源极跟随器和所述第二源极跟随器的栅极均与所述传输管和所述复位管之间的浮置扩散区电连接，所述第一源极跟随器和所述第二源极跟随器的源极均通过选通管与行选择线相连；开关器件，与所述第二源极跟随器相连，当所述开关器件导通时，所述第二源极跟随器与所述第一源极跟随器同时工作；当所述开关器件断开时，所述第一源极跟随器工作，所述第二源极跟随器不工作。
第二方面，提供一种图像传感器，包括：像素单元阵列，所述像素单元阵列中的至少一个像素单元包括：光电转换器件；传输管；复位管；第一源 极跟随器和第二源极跟随器，所述第一源极跟随器和所述第二源极跟随器的栅极均与所述传输管和所述复位管之间的浮置扩散区电连接，所述第一源极跟随器和所述第二源极跟随器的源极均通过选通管与行选择线相连；开关器件，与所述第二源极跟随器相连，当所述开关器件导通时，所述第二源极跟随器与所述第一源极跟随器同时工作；当所述开关器件断开时，所述第一源极跟随器工作，所述第二源极跟随器不工作；控制电路，与所述像素单元中的开关器件相连，用于控制所述第二源极跟随器是否与所述第一源极跟随器同时工作。
第三方面，提供一种像素单元，包括：光电转换器件；第一传输管；复位管；源极跟随器，所述源极跟随器的栅极与所述第一传输管和所述复位管之间的浮置扩散区电连接，所述源极跟随器的源极通过选通管与行选择线相连；第二传输管，所述第二传输管的第一极和第二极分别与所述光电转换器件的输出端和所述浮置扩散区电连接，其中所述第一极为源极，所述第二极为漏极；或者所述第一极为漏极，所述第二极为源极；开关器件，与所述第二传输管相连，当所述开关器件导通时，所述第二传输管与所述第一传输管同时工作；当所述开关器件断开时，所述第一传输管工作，所述第二传输管不工作。
第四方面，提供一种图像传感器，包括：像素单元阵列，所述像素单元阵列中的至少一个像素单元包括：光电转换器件；第一传输管；复位管；源极跟随器，所述源极跟随器的栅极与所述第一传输管和所述复位管之间的浮置扩散区电连接，所述源极跟随器的源极通过选通管与行选择线相连；第二传输管，所述第二传输管的第一极和第二极分别与所述光电转换器件的输出端和所述浮置扩散区电连接，其中所述第一极为源极，所述第二极为漏极；或者所述第一极为漏极，所述第二极为源极；开关器件，与所述第二传输管相连，当所述开关器件导通时，所述第二传输管与所述第一传输管同时工作；当所述开关器件断开时，所述第一传输管工作，所述第二传输管不工作；控制电路，与所述像素单元中的开关器件相连，用于控制所述第二传输管是否与所述第一传输管同时工作。
本申请可以根据实际需要，在像素单元的源极跟随器的尺寸和浮置扩散区的电荷/电压增益之间进行权衡，从而有效控制像素单元输出的图像信号的信噪比。
附图说明
图1是传统像素单元的结构示意图。
图2是本申请一个实施例提供的像素单元的结构示意图。
图3是图2中的像素单元的实际版图的示例图。
图4是本申请一个实施例提供的图像传感器的示意性结构图。
图5是图4中的图像传感器的实际版图的示例图。
图6是本申请另一实施例提供的像素单元的结构示意图。
图7是图6中的像素单元的实际版图的示例图。
图8是本申请另一实施例提供的图像传感器的示意性结构图。
图9是图8中的图像传感器的实际版图的示例图。
具体实施方式
图像传感器可以包括像素单元(pixel)阵列和信号处理电路。像素单元阵列所在的区域可以称为图像传感器的感光电路区。像素单元阵列可以由多个像素单元组成，例如可以由几万甚至几亿个像素单元组成。像素单元有时也可称为感光单元。像素单元可用于将接收到的光信号转换成模拟信号。
信号处理电路所在的区域也可称为图像传感器的外围电路区。信号处理电路与像素单元阵列电连接，可用于将像素单元阵列输出的模拟信号转换成用于表示像素单元采集到的图像信息的数字信号。
如图1所示，传统的像素单元10通常可以包括光电二极管PD、传输管TX、源极跟随器SF、复位管RST以及选通管SEL。
光电二极管PD可用于将接收到的光子转换成电子(即输出光生电子)。应理解，图1中的光电二极管PD也可以采用其他具有光电转换功能的器件替换，如光电三极管、光电倍增管等。
传输管TX(或称电子传输管TX或传输晶体管TX)可用于将光电转换器件输出的光生电子传输至位于传输管TX与复位管RST之间的浮置扩散区FD。
浮置扩散区FD可以起到电荷-电压转换作用。浮置扩散区FD可以理解为一个晶体管寄生电容，可用于根据传输管TX输出的电荷量，感生出一个相应的电压信号。
复位管RST(或称复位晶体管RST)用于将像素单元进行重置，以便下次信号采集。复位管有时也可称为重置晶体管。
源极跟随器SF的栅极与浮置扩散区FD相连，源极跟随器SF的源极可以与行选择线(图1未示出)相连。源极跟随器SF可用于接收浮置扩散区FD的电压信号，并生成浮置扩散区FD的电压信号的跟随信号(或者源极跟随器SF的输出信号)。该跟随信号可以理解为将浮置扩散区FD的电压信号进行电位平移之后得到的电压信号。
选通管SEL(或称选通晶体管SEL)，可用于接收外部的控制电路输入的控制信号。该控制电路例如可以是像素单元10所在的图像传感器中的信号处理电路。当控制电路控制选通管SEL导通时，源极跟随器SF可以向行选择线输出相应的跟随信号。
源极跟随器的晶体管噪声是像素单元整体噪声的重要组成部分。源极跟随器的噪声与源极跟随器的尺寸有关。一般来讲，源极跟随器的尺寸越大，其噪声越小。因此，为了提升图像信号的信噪比，一种可能的实现方式是将像素单元内的多个源极跟随器并联起来，以增大源极跟随器的尺寸，降低源极跟随器的噪声。但是，如图1所示，源极跟随器SF的栅极与浮置扩散区FD电性互联，意味着源极跟随器SF的栅极电容是浮置扩散区FD的总电容的一部分。因此，多源极跟随器并联的实现方式在降低源极跟随器的噪声的同时，也会增大浮置扩散区的总电容，从而降低浮置扩散区的电荷/电压增益。如果光电转换器件接收到的信号比较强(比如工作在明亮场景)，多源极跟随器并联通常可以起到提升图像信号的信噪比的作用；但是，如果光电转换器件接收到的信号比较微弱(比如工作在阴暗环境)，则多源极跟随器并联导致的浮置扩散区的总电容的增大反而可能降低像素单元输出的图像信号的信噪比。
从以上论述可以看出，源极跟随器的尺寸和浮置扩散区的总电容是相互矛盾的。这样会导致像素单元输出的图像信号的信噪比并不稳定，难以控制。
为了解决上述问题，下面结合图2，对本申请实施例提供的像素单元进行详细描述。
如图2所示，像素单元20可以包括光电二极管PD，传输管TX，复位管RST，第一源极跟随器SF1，第二源极跟随器SF2，开关管DCG，第一选通管SEL1，第二选通管SEL2。图2中的像素单元20的实际版图可以参照 图3布置。
光电二极管PD也可以替换成其他类型的光电转换器件，如光电三极管或光电倍增管。
光电二极管PD、传输管TX和复位管RST的位置和功能可以参见图1的描述，此处不再赘述。
开关管DCG(或称为双增益开关管)的一端与传输管TX相连，开关管DCG的另一端与复位管RST相连，从而可以将传输管TX和复位管RST之间的浮置扩散区分成位于传输管TX和开关管DCG之间的第一浮置扩散区FD1，以及位于开关管DCG和复位管RST之间的第二浮置扩散区FD2。
第一源极跟随器SF1和第二源极跟随器SF2为相互并联的源极跟随器。需要说明的是，本申请实施例仅是以像素单元20包含两个源极跟随器为例进行说明，实际上，像素单元20可以包更多的源极跟随器。
第一源极跟随器SF1的栅极与第一浮置扩散区FD1相连(本申请中的电路器件之间的相连均指电连接)，第二源极跟随器SF2的栅极与第二浮置扩散区FD2相连。第一源极跟随器SF1的源极可以通过选通管SEL1与行选择线相连，第二源极跟随器SF2的源极均可通过选通管SEL2与行选择线相连。
如图2所示，当开关器件DCG导通时，第二源极跟随器SF2与第一源极跟随器SF1可以同时工作；当开关器件DCG断开时，第一源极跟随器SF1工作，第二源极跟随器SF2不工作。
开关管DCG还可以替换为其他类型的开关器件，只要能够控制开关器件所在线路导通和关断即可。
图2中，开关器件(开关管DCG)位于传输管TX和复位管RST之间的浮置扩散区。实际上，本申请实施例对开关器件的具体位置不做限定，只要能够控制第二源极跟随器SF2是否与第一源极跟随器SF1同时工作即可。例如，该开关器件也可以位于浮置扩散区和第二源极跟随器SF2的栅极之间。
本申请实施例引入了第一源极跟随器SF1和第二源极跟随器SF2，并利用开关器件控制第一源极跟随器SF1和第二源极跟随器SF2是否同时工作，当第一源极跟随器SF1和第二源极跟随器SF2同时工作时，相当于增大了像素单元20中的源极跟随器的尺寸，从而能够降低像素单元20的噪声；当第 一源极跟随器件SF1工作，而第二源极跟随器SF2不工作时，第一源极跟随器SF1的栅极电容会比较小，浮置扩散区的电容也会比较小，从而可以提升浮置扩散区的电荷/电压增益。
因此，本申请实施例可以根据实际需要，在像素单元的源极跟随器的尺寸和浮置扩散区的电荷/电压增益之间进行权衡，从而有效控制像素单元输出的图像信号的信噪比。
下面以阴暗场景和明亮场景为例，对像素单元20的控制方式进行详细说明。
在阴暗场景下，像素单元20在曝光时，传输管TX处于关闭状态，复位管RST和开关管DCG的栅极均接高电位，使得复位管RST和开关管DCG均处于开启状态。复位管RST的漏极接高电位，使得选通管SEL1，SEL2都处于关闭状态。曝光结束后，开始读取信号，开关管DCG的栅极置为低电位，开关管DCG关闭，此时浮置扩散区FD1被浮置于一个高电位。然后，将选通管SEL1的栅极置于高电位，此时在选通管SEL1的源极会随第一浮置扩散区FD1的电位处于一个电位值V ref,作为参考电位。然后将传输管TX置于高电位，从而开启传输管TX。等光电二极管PD输出的光生电子传入第一浮置扩散区FD1之后，关闭传输管TX。第一浮置扩散区FD1的电位会由于光电二极管PD输入的光生电子而下降，此时第一源极跟随器SF1的源极会跟随第一浮置扩散区FD1电位下降而下降。将第一浮置扩散区FD1的下降后的电位计为V sig。电位V ref与电位V sig之间的电压差值即可视为与入射光信号对应的信号值，将该电压差值交由后续电路处理，即可转换出像素单元采集到的亮度和颜色信息。由于此时只有第一源极跟随器SF1参与工作，像素单元20的浮置扩散区的总电容较小，浮置扩散区的电荷电压增益较大，因此即使在阴暗场景下，浮置扩散区的电压信号(V ref-V sig)仍然比较大，像素单元20输出的图像信号的信噪比较高。
在明亮场景下，曝光时，传输管TX关闭，复位管RST和开关管DCG的栅极均接高电位，使二者均处于开启状态。复位管RST的漏极接高电位，且选通管SEL1，SEL2均处于关闭状态。曝光结束后，开始读取信号，复位管RST的栅极置为低电位，使得复位管RST处于关闭状态。此时，浮置扩散区FD1、FD2电性联通，电位相同，且均被浮置于一个高电位。然后，选通管SEL1、SEL2同时置于高电位，此时，选通管SEL1、SEL2的源极会跟 随浮置扩散区FD1、FD2的电位而处于电位值V ref,作为参考电位。然后，将传输管TX置于高电位，从而开启传输管TX。等光电二极管PD输出的光生电子传入浮置扩散区FD1、FD2之后，关闭传输管TX，浮置扩散区FD1、FD2的电位会由于光电二极管PD输出的光生电子而下降，此时，源极跟随器SF1、SF2的源极会跟随浮置扩散区FD1、FD2的电位下降而下降，将下降后的电位计为V sig。V ref与V sig之间的电压差值即可用于表征入射光信号对应的信号值，将该电压差值交由后续电路处理之后，即可转换出像素单元采集到的图像信息。由于此时源极跟随器SF1、SF2同时参与工作，等效于源跟随器的尺寸变大，因此源跟随器的噪声较小，使明亮场景下像素单元输出的图像信号的信噪比维持在较高水准。
本申请实施例还提供一种图像传感器。该图像传感器可以是基于互补金属氧化物半导体(complementary metal oxide semiconductor image sensor，CMOS)的图像传感器。该图像传感器(或芯片)可广泛用于消费电子，安防监控，工业自动化，人工智能，物联网等领域。该图像传感器可用于图像信息的采集和整理，为后续处理和应用提供信息源。
如图4所示，该图像传感器40可包括像素单元阵列42和控制电路44。像素单元阵列42中的一个或多个像素单元为前文描述的像素单元20。
该控制电路44可以是图像传感器40内部的信号处理电路。控制电路44可以与像素单元20中的开关器件相连，用于通过开关器件控制第二源极跟随器SF2是否与第一源极跟随器SF1同时工作。
假设像素单元阵列62为2×2的像素单元阵列，且像素单元阵列42中的每个像素单元均为如图2所示的像素单元20，则其实际版图可以参照图5所示的方式进行布置。
再次参见图1所示的传统像素单元，一般而言，较大尺寸的像素单元，由于感光面积大，进光量足，一般需要其光电二极管PD(或其他类型的光电转换器件)有较大的满阱电子数。
因此，在设计大尺寸像素单元时，为了把大量的光生电子传输到浮置扩散区FD，需要在光电二极管PD和浮置扩散区FD之间设计一个尺寸较大的传输管TX。
但是尺寸较大的传输管TX会在浮置扩散区FD和传输管TX之间引入较大的寄生电容，从而导致浮置扩散区FD的总电容较大，电荷/电压增益偏 小。当光线较弱或者曝光时间较短时，光电二极管PD感生的电子数目很少。此时，如果浮置扩散区FD的总电容较大，会使浮置扩散区FD产生的电压信号较小，进而降低了阴暗场景下像素单元输出的图像信号的信噪比。
针对上述问题，如图6所示，本申请实施例还提供一种像素单元60。像素单元60可以包括光电二极管PD，第一传输管TX1，第二传输管TX2，复位管RST，源极跟随器SF，开关管DCG，选通管SEL。
光电二极管PD可用于将接收到的光子转换成电子(即输出光生电子)。光电二极管PD也可以替换成其他类型的光电转换器件，如光电三极管或光电倍增管。
光电二极管PD、第一传输管TX1、复位管RST、源极跟随器SF和选通管SEL的位置和功能可以参见图1中的关于光电二极管PD、传输管TX、复位管RST、源极跟随器SF和选通管SEL的描述，此处不再赘述。
第二传输管TX2的第一极和第二极分别与光电二极管PD的输出端和浮置扩散区电连接。第一极可以为第二传输管TX2的源极，第二极可以为第二传输管TX2的漏极；或者第一极可以为第二传输管TX2的漏极，第二极可以为第二传输管TX2的源极。
开关管DCG(或称为双增益开关管)的一端与第一传输管TX1相连，开关管DCG的另一端与复位管RST相连，从而将第一传输管TX1和复位管RST之间的浮置扩散区分成位于第一传输管TX1和开关管DCG之间的第一浮置扩散区FD1，以及位于开关管DCG和复位管RST之间的第二浮置扩散区FD2。第二传输管TX2的第二极与第二浮置扩散区FD2相连。
开关管DCG还可以替换为其他类型的开关器件，只要能够控制开关器件所在线路导通和关断即可。
开关管DCG也可以位于第二传输管TX2的第二极与浮置扩散区(位于第一传输管TX和RST之间)之间，这样也可以起到控制第二传输管TX2是否与第一传输管TX1是否同时工作的作用。
图6所示的像素单元60的实际版图可以参照图7布置。如图7所示，第一传输管TX1与第一浮置扩散区FD1的硅晶(silicon)的重叠部分较小，且其对应的第一浮置扩散区FD1的面积也较小，因此第一浮置扩散区FD1的总电容也较小。
本申请实施例对第一传输管TX1和第二传输管TX2的尺寸不做具体限 定，在有些实施例中，可以将第二传输管TX2的尺寸设置为大于第一传输管TX1的尺寸，使得第二传输管TX2工作时，能够尽量将更多的电子传输至浮置扩散区，且第二传输管TX2不工作时，第一传输管TX1对浮置扩散区的总电容的影响尽可能小一些。
本申请实施例对第一传输管TX1和第二传输管TX2同时工作的条件不做具体限定，可以根据实际需要选取。例如，当前场景为明亮场景的情况下，光电二极管PD产生的电子数目较多，可以控制第一传输管TX1和第二传输管TX2同时工作；在当前场景为阴暗场景的情况下，光电二极管PD产生的电子数目较多，可以控制第二传输管TX2不工作。上述控制操作可以由像素单元60之外的控制电路执行。该控制电路例如可以是像素单元60所在的图像传感器中的信号处理电路。
下面以阴暗场景和明亮场景为例，对像素单元60的控制方式进行详细说明。
工作时，在阴暗场景下，曝光时，控制第一传输管TX1、第二传输管TX2和选通管SEL都处于关闭状态。开关管DCG和复位管RST处于打开状态，且复位管RST的漏极处于高电压状态。
当曝光结束时，控制开关管DCG关闭，选通管SEL打开，此时第一浮置扩散区FD1处于一个浮置的高电压状态，在选通管SEL的源极读取第一参考电压V ref1。然后，可以开启第一传输管TX1，光电二极管PD的电子被传输到第一浮置扩散区FD1。第一浮置扩散区FD1的电压会下降，此时在选通管SEL的源极读取第一信号电压V sig1,V ref1-V sig1即为与入射光强度对应的电压信号。
图像传感器的外围电路(如信号处理电路)可以通过一定的转换读取处理，即可成像。此时，由于第一浮置扩散区FD1的电容较小，因此第一浮置扩散区FD1的电荷/电压增益较高，即使在阴暗场景下，像素单元60输出的图像信号仍然保持了相对较好的信噪比。
在明亮场景下，曝光时，第一传输管TX1、第二传输管TX2以及选通管SEL都处于关闭状态，开关管DCG和复位管RST处于打开状态，复位管RST的漏极一直处于高电压状态。
当曝光结束时，控制复位管RST关闭，选通管SEL打开，此时第一浮置扩散去FD1和第二浮置扩散区FD2连通且均处于一个浮置的高电压状 态。在选通管SEL的源极读取第二参考电压V ref2,然后同时开启第一传输管TX1和第二传输管TX2。光电二极管PD的电子被传输到第一浮置扩散区FD1和第二浮置扩散区FD2。此时，第一浮置扩散区FD1和第二浮置扩散区FD2的电压会下降，可以在选通管SEL的源极读取第二信号电压V sig2。V ref2-V sig2即为与入射光强度对应的电压信号。
图像传感器的外围电路(如信号处理电路)可以通过一定的转换读取处理，即可成像。由于明亮场景下光电二极管PD内的电子数目较多，第一传输管TX1和第二传输管TX2同时开启有利于快速且完整地将光电二极管PD输出的光生电子传到浮置扩散区。
由此可见，图6提供的像素结构能够在阴暗场景、信号较小时实现高电荷/电压增益，高信噪比；又能在信号很强时，尽量实现电荷的完全传输，使得最终输出的图像信号具有较大的动态范围。
本申请实施例还提供一种图像传感器。本申请实施例提供的图像传感器可以是基于CMOS的图像传感器。该图像传感器(或芯片)可广泛用于消费电子，安防监控，工业自动化，人工智能，物联网等领域。该图像传感器可用于图像信息的采集和整理，为后续处理和应用提供信息源。
如图8所示，该图像传感器80可包括像素单元阵列82和控制电路84。像素单元阵列82中的一个或多个像素单元为前文描述的像素单元60。
该控制电路84可以是图像传感器80内部的信号处理电路。控制电路84可以与像素单元60中的开关器件相连，用于通过开关器件控制第二传输管TX2是否与第一传输管TX1同时工作。
假设像素单元阵列82为2×2的像素单元阵列，且像素单元阵列82中的每个像素单元均为如图7所示的像素单元，则其实际版图可以参照图9所示的方式进行布置。
应理解，图6的实施例与图2的实施例可以相互结合。例如，开关管DCG可用于同时控制第二传输管TX2和第二源极跟随器SF2是否与第一传输管TX1和第一源极跟随器SF1同时工作。
在上述实施例中，可以全部或部分地通过软件、硬件、固件或者其他任意组合来实现。当使用软件实现时，可以全部或部分地以计算机程序产品的形式实现。所述计算机程序产品包括一个或多个计算机指令。在计算机上加载和执行所述计算机程序指令时，全部或部分地产生按照本发明实施例所述 的流程或功能。所述计算机可以是通用计算机、专用计算机、计算机网络、或者其他可编程装置。所述计算机指令可以存储在计算机可读存储介质中，或者从一个计算机可读存储介质向另一个计算机可读存储介质传输，例如，所述计算机指令可以从一个网站站点、计算机、服务器或数据中心通过有线(例如同轴电缆、光纤、数字用户线(digital subscriber line，DSL))或无线(例如红外、无线、微波等)方式向另一个网站站点、计算机、服务器或数据中心进行传输。所述计算机可读存储介质可以是计算机能够存取的任何可用介质或者是包含一个或多个可用介质集成的服务器、数据中心等数据存储设备。所述可用介质可以是磁性介质(例如，软盘、硬盘、磁带)、光介质(例如数字视频光盘(digital video disc，DVD))、或者半导体介质(例如固态硬盘(solid state disk，SSD))等。
需要说明的是，在不冲突的前提下，本申请描述的各个实施例和/或各个实施例中的技术特征可以任意的相互组合，组合之后得到的技术方案也应落入本申请的保护范围。
本领域普通技术人员可以意识到，结合本文中所公开的实施例描述的各示例的单元及算法步骤，能够以电子硬件、或者计算机软件和电子硬件的结合来实现。这些功能究竟以硬件还是软件方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本申请的范围。
在本申请所提供的几个实施例中，应该理解到，所揭露的系统、装置和方法，可以通过其它的方式实现。例如，以上所描述的装置实施例仅仅是示意性的，例如，所述单元的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另一点，所显示或讨论的相互之间的耦合或直接耦合或通信连接可以是通过一些接口，装置或单元的间接耦合或通信连接，可以是电性，机械或其它的形式。
所述作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部单元来实现本实施例方案的目的。
另外，在本申请各个实施例中的各功能单元可以集成在一个处理单元 中，也可以是各个单元单独物理存在，也可以两个或两个以上单元集成在一个单元中。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以所述权利要求的保护范围为准。

Claims (19)

  1. 一种像素单元，其特征在于，包括：
    光电转换器件；
    传输管；
    复位管；
    第一源极跟随器和第二源极跟随器，所述第一源极跟随器和所述第二源极跟随器的栅极均与所述传输管和所述复位管之间的浮置扩散区电连接，所述第一源极跟随器和所述第二源极跟随器的源极均通过选通管与行选择线相连；
    开关器件，与所述第二源极跟随器相连，当所述开关器件导通时，所述第二源极跟随器与所述第一源极跟随器同时工作；当所述开关器件断开时，所述第一源极跟随器工作，所述第二源极跟随器不工作。
  2. 根据权利要求1所述的像素单元，其特征在于，所述开关器件的一端与所述传输管相连，所述开关器件的另一端与所述复位管相连，从而将所述传输管和所述复位管之间的浮置扩散区分成位于所述传输管和所述开关器件之间的第一浮置扩散区，以及位于所述开关器件和所述复位管之间的第二浮置扩散区；所述第一源极跟随器的栅极与所述第一浮置扩散区相连，所述第二源极跟随器的栅极与所述第二浮置扩散区相连。
  3. 根据权利要求1或2所述的像素单元，其特征在于，所述开关器件为开关管。
  4. 根据权利要求1-3中任一项所述的像素单元，其特征在于，所述光电转换器件为光电二极管、光电三极管或光电倍增管。
  5. 一种图像传感器，其特征在于，包括：
    像素单元阵列，所述像素单元阵列中的至少一个像素单元包括：光电转换器件；传输管；复位管；第一源极跟随器和第二源极跟随器，所述第一源极跟随器和所述第二源极跟随器的栅极均与所述传输管和所述复位管之间的浮置扩散区电连接，所述第一源极跟随器和所述第二源极跟随器的源极均通过选通管与行选择线相连；开关器件，与所述第二源极跟随器相连，当所述开关器件导通时，所述第二源极跟随器与所述第一源极跟随器同时工作；当所述开关器件断开时，所述第一源极跟随器工作，所述第二源极跟随器不工作；
    控制电路，与所述像素单元中的开关器件相连，用于控制所述第二源极跟随器是否与所述第一源极跟随器同时工作。
  6. 根据权利要求5所述的图像传感器，其特征在于，所述控制电路用于在当前场景为明亮场景的情况下，控制所述开关器件导通；在当前场景为阴暗场景的情况下，控制所述开关器件关断。
  7. 根据权利要求5或6所述的图像传感器，其特征在于，所述开关器件的一端与所述传输管相连，所述开关器件的另一端与所述复位管相连，从而将所述传输管和所述复位管之间的浮置扩散区分成位于所述传输管和所述开关器件之间的第一浮置扩散区，以及位于所述开关器件和所述复位管之间的第二浮置扩散区；所述第一源极跟随器的栅极与所述第一浮置扩散区相连，所述第二源极跟随器的栅极与所述第二浮置扩散区相连。
  8. 根据权利要求5-7中任一项所述的图像传感器，其特征在于，所述开关器件为开关管。
  9. 根据权利要求5-8中任一项所述的图像传感器，其特征在于，所述光电转换器件为光电二极管、光电三极管或光电倍增管。
  10. 一种像素单元，其特征在于，包括：
    光电转换器件；
    第一传输管；
    复位管；
    源极跟随器，所述源极跟随器的栅极与所述第一传输管和所述复位管之间的浮置扩散区电连接，所述源极跟随器的源极通过选通管与行选择线相连；
    第二传输管，所述第二传输管的第一极和第二极分别与所述光电转换器件的输出端和所述浮置扩散区电连接，其中所述第一极为源极，所述第二极为漏极；或者所述第一极为漏极，所述第二极为源极；
    开关器件，与所述第二传输管相连，当所述开关器件导通时，所述第二传输管与所述第一传输管同时工作；当所述开关器件断开时，所述第一传输管工作，所述第二传输管不工作。
  11. 根据权利要求10所述的像素单元，其特征在于，所述开关器件的一端与所述第一传输管相连，所述开关器件的另一端与所述复位管相连，从而将所述第一传输管和所述复位管之间的浮置扩散区分成位于所述第一传 输管和所述开关器件之间的第一浮置扩散区，以及位于所述开关器件和所述复位管之间的第二浮置扩散区；所述第二传输管的第二极与所述第二浮置扩散区相连。
  12. 根据权利要求10或11所述的像素单元，其特征在于，所述第二传输管的尺寸大于所述第一传输管的尺寸。
  13. 根据权利要求10-12中任一项所述的像素单元，其特征在于，所述开关器件为开关管。
  14. 根据权利要求10-13中任一项所述的像素单元，其特征在于，所述光电转换器件为光电二极管、光电三极管或光电倍增管。
  15. 一种图像传感器，其特征在于，包括：
    像素单元阵列，所述像素单元阵列中的至少一个像素单元包括：光电转换器件；第一传输管；复位管；源极跟随器，所述源极跟随器的栅极与所述第一传输管和所述复位管之间的浮置扩散区电连接，所述源极跟随器的源极通过选通管与行选择线相连；第二传输管，所述第二传输管的第一极和第二极分别与所述光电转换器件的输出端和所述浮置扩散区电连接，其中所述第一极为源极，所述第二极为漏极；或者所述第一极为漏极，所述第二极为源极；开关器件，与所述第二传输管相连，当所述开关器件导通时，所述第二传输管与所述第一传输管同时工作；当所述开关器件断开时，所述第一传输管工作，所述第二传输管不工作；
    控制电路，与所述像素单元中的开关器件相连，用于控制所述第二传输管是否与所述第一传输管同时工作。
  16. 根据权利要求15所述的图像传感器，其特征在于，所述控制电路用于在当前场景为明亮场景的情况下，控制所述开关器件导通；在当前场景为阴暗场景的情况下，控制所述开关器件关断。
  17. 根据权利要求15或16所述的图像传感器，其特征在于，所述开关器件的一端与所述第一传输管相连，所述开关器件的另一端与所述复位管相连，从而将所述第一传输管和所述复位管之间的浮置扩散区分成位于所述第一传输管和所述开关器件之间的第一浮置扩散区，以及位于所述开关器件和所述复位管之间的第二浮置扩散区；所述第二传输管的第二极与所述第二浮置扩散区相连。
  18. 根据权利要求15-17中任一项所述的图像传感器，其特征在于，所 述开关器件为开关管。
  19. 根据权利要求15-18中任一项所述的图像传感器，其特征在于，所述光电转换器件为光电二极管、光电三极管或光电倍增管。
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