WO2021184634A1 - 光电传感器、像素电路、图像传感器及光电感测方法 - Google Patents

光电传感器、像素电路、图像传感器及光电感测方法 Download PDF

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Publication number
WO2021184634A1
WO2021184634A1 PCT/CN2020/105152 CN2020105152W WO2021184634A1 WO 2021184634 A1 WO2021184634 A1 WO 2021184634A1 CN 2020105152 W CN2020105152 W CN 2020105152W WO 2021184634 A1 WO2021184634 A1 WO 2021184634A1
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Prior art keywords
photo
coupled
integration
unit
photoelectric sensor
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PCT/CN2020/105152
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English (en)
French (fr)
Inventor
张盛东
廖聪维
周晓梁
彭志超
梁键
安军军
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北京大学深圳研究生院
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/70—Circuitry for compensating brightness variation in the scene
    • H04N23/73—Circuitry for compensating brightness variation in the scene by influencing the exposure time
    • 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
    • H04N25/53—Control of the integration time

Definitions

  • This application relates to an image sensor, in particular to a photoelectric sensor, a pixel circuit, an image sensor and a corresponding photoelectric sensing method of a photosensitive unit with a light memory function.
  • Photoelectric sensors and image sensors play an extremely important role in many medical electronics, consumer electronics, and military electronic equipment.
  • X-ray images are the golden criteria for the diagnosis of various diseases such as orthopedics, lung diseases, and cardiovascular and cerebrovascular diseases; fingerprint recognition has become the standard security lock for smartphones; hyperspectral and multispectral cameras are important modern military detection methods.
  • high-sensitivity, high-resolution photoelectric sensors and image sensors for weak light signals and transient photoelectric signals have always been the focus of research.
  • the image sensor is the core component since the discovery of X-rays for more than 100 years.
  • Low-dose, high-resolution, and dynamic imaging are the main development directions of modern X-ray imaging.
  • the requirements for image sensors are high sensitivity, high signal-to-noise ratio, and fast response speed.
  • Imaging technologies can be divided into the following categories: imaging technologies based on charge coupled devices (CCD) and complementary metal oxide (CMOS) transistors, and flat panels based on hydrogenated amorphous silicon (a-Si:H) photodiodes Detection imaging technology.
  • CCD charge coupled devices
  • CMOS complementary metal oxide
  • a-Si:H photodiode technology a-Si:H photodiode technology.
  • One of the most important research directions in the application of X-ray medical imaging today is to improve the sensitivity of the image sensor to reduce the X-ray radiation dose and reduce the harm to the human body.
  • the long detection distance results in extremely weak photoelectric signals that can be used for imaging, and the rapid change of events requires the response speed of photoelectric imaging to be extremely fast.
  • the present application proposes a photoelectric sensor, including a photosensitive unit, configured to receive incident light and generate a photo-generated current during the exposure stage, which has a light memory function, that is, it remains in the photosensitive unit after the incident light is removed. And a storage unit, coupled to the photosensitive unit, configured to convert the photo-generated current into a photo-generated charge or a photo-generated voltage and store or maintain it during the integration phase, wherein the integration phase includes at least after the exposure phase is over The preset time period.
  • the photosensitive unit with optical memory function includes a metal oxide semiconductor device or an organic semiconductor device with optical memory function.
  • the photosensitive unit at least includes a phototransistor, a photodiode or a photoresistor.
  • the storage unit includes a storage capacitor coupled to the photosensitive unit, and the storage capacitor is configured to perform an integration operation that converts the photo-generated current into the photo-generated charge or photo-generated voltage.
  • the storage unit further includes an integration control unit, which is coupled between the photosensitive unit and the storage capacitor, and is configured to control the time for performing the integration operation under the influence of an integration control signal.
  • an integration control unit which is coupled between the photosensitive unit and the storage capacitor, and is configured to control the time for performing the integration operation under the influence of an integration control signal.
  • the integration control unit includes an integration transistor, the first pole and the second pole of which are respectively coupled to the storage capacitor and the photosensitive unit, or to the photosensitive unit and the power supply, and the control pole is configured to receive the integration control. Signal.
  • the storage unit further includes an amplifying unit coupled to the storage capacitor and configured to amplify the photo-generated charge or voltage.
  • the time of the integration phase is longer than the time of the exposure phase.
  • the integration stage also includes a time period coincident with the exposure stage.
  • the present application also provides a pixel circuit, including the photoelectric sensor as described in any one of the foregoing, and a scanning unit, which is coupled to the storage unit of the photoelectric sensor, and is configured to convert the photo-generated current signal or the scanning unit under the control of the scanning signal.
  • the voltage signal or the corresponding electrical signal is output to the outside of the pixel circuit.
  • the amplifying unit includes an N-type amplifying transistor, the first pole of which is coupled to the scanning unit, and the control pole and the second pole of which are respectively coupled to the storage capacitor The first and second plates.
  • the amplifying unit includes a P-type amplifying transistor, the control electrode of which is coupled to the first plate of the storage capacitor, and the second plate of the capacitor is coupled to A first reference potential, a first pole of which is coupled to a second reference potential, and a second pole of which is coupled to the scanning unit, wherein the second reference potential is higher than the first reference potential and the power supply voltage.
  • the present application also provides an image sensor, including a pixel array, and a scanning control circuit and a readout circuit coupled therewith; wherein the pixel array includes one or more pixel circuits as described above.
  • the devices in the scan control circuit and the readout circuit are made of metal oxide semiconductor or organic semiconductor technology.
  • the present application also provides an electronic device, which includes the photoelectric sensor as described in any one of the foregoing or the image sensor as described in any one of the foregoing.
  • the present application also provides a photoelectric sensing method, which includes sensing incident light and generating a photogenerated current by a photosensitive unit with a photomemory function in the exposure stage; and converting the photogenerated current into a photogenerated charge or voltage in the integration stage , And store or maintain the photo-generated charge or voltage, wherein the integration phase at least includes a preset time period after the exposure phase ends.
  • the time of the integration phase is longer than the time of the exposure phase.
  • the integration stage also includes a time period coincident with the exposure stage.
  • FIG. 1 is a schematic diagram of the working mode of a phototransistor with optical memory function according to an embodiment of the present application
  • Figure 2(a) shows a modular schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to an embodiment of the present application
  • Figure 2(b) shows a working sequence diagram including the photoelectric sensor and image sensor shown in Figure 2(a);
  • Fig. 3(a) shows a schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to an embodiment of the present application
  • Figure 3(b) shows a schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to another embodiment of the present application
  • Fig. 3(c) shows a schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to another embodiment of the present application
  • Fig. 4 shows a schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to another embodiment of the present application
  • FIG. 5 is a schematic diagram showing the working sequence of the image sensor including the photoelectric sensor and the pixel circuit in FIG. 4;
  • FIG. 6 shows a schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to another embodiment of the present application
  • FIG. 7 shows a schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to another embodiment of the present application.
  • FIG. 8 is a schematic diagram showing the structure of an image sensor according to an embodiment of the present application.
  • Fig. 9 shows an image sensing method according to an embodiment of the present application.
  • the transistors in this application may be bipolar transistors or field effect transistors.
  • the transistor includes a control electrode, a first electrode and a second electrode.
  • the control electrode is coupled to the control metal layer.
  • the first electrode and the second electrode are coupled to the active layer with optical memory function. Medium layer.
  • the electrical conductivity characteristics of the active layer with the optical memory function of the phototransistor are modulated by the input light and change.
  • the control pole refers to the base of the bipolar transistor
  • the first pole refers to the collector or emitter of the bipolar transistor
  • the corresponding second pole refers to the emitter or collector of the bipolar transistor.
  • the control electrode refers to the gate of the field-effect transistor
  • the first electrode can be the drain or source of the field-effect transistor
  • the corresponding second electrode can be the source or drain of the field-effect transistor pole.
  • the voltage of the drain should be greater than or equal to the voltage of the source, so the position of the source and the drain will vary with the bias state of the transistor.
  • the transistors used in the display are usually thin film transistors (TFT)
  • the embodiments of the present application may be illustrated with thin film transistors as an example, and the drain and source of the transistors in the embodiments of the present application can be based on different bias states of the transistors. And change.
  • the photoelectric sensor, the pixel circuit and the image sensor are based on a photosensitive unit with a light memory function to improve the imaging quality under transient and low-dose light input conditions.
  • the so-called light memory function of the photosensitive unit means that after the exposure, the photosensitive unit receives the input light and generates a photogenerated current; after the exposure, even if the incident light is removed, the photosensitive unit still maintains the photogenerated current for a preset period of time.
  • materials that have optical memory function and can be used as active or photosensitive functional layers include metal oxide semiconductors in inorganic semiconductors (for example, due to the narrow band gap and high oxygen vacancy concentration, indium zinc oxide IZO The photoelectric response intensity is higher, and has a better optical memory function), and some organic semiconductors.
  • the photosensitive unit with light memory function like other types of photosensitive units, can generate photo-generated carriers, and then have the input light-modulated conductance or current. But the difference is that due to the lattice relaxation process, the photosensitive cell based on this material has significant optical memory.
  • the photo-generated current can be maintained for a long time in such a photosensitive cell.
  • the value of the photo-generated current can last for more than several hours, far exceeding the length of time required for photoelectric readout detection.
  • the resistance value of the metal oxide semiconductor photoresistor will change, and it has the ability to continuously maintain this resistance state.
  • the optical memory properties of materials such as metal oxide semiconductors and organic semiconductors are used to enhance the photoelectric conversion capability of the photosensitive unit and improve the signal-to-noise ratio and sensitivity of the photoelectric sensor or image sensor.
  • the use of the light memory characteristics of the metal oxide semiconductor photosensitive unit can reduce the X-ray exposure time to avoid harm to the human body while still Ensure that you get a clear image.
  • FIG. 1 is a schematic diagram of the working mode of a phototransistor with optical memory function according to an embodiment of the present application.
  • photosensitive cells with optical memory functions such as photodiodes or photoresistors.
  • Idk the output current of the phototransistor
  • Iph0 the output current of the phototransistor
  • Iph1 the output current of the phototransistor
  • Fig. 2(a) shows a modular schematic diagram of a photoelectric sensor and image sensor pixels according to an embodiment of the present application.
  • the photosensor 102 may include a photosensitive unit 1022 with a light memory function, and a storage unit 1024 coupled to the photosensitive unit 1022.
  • the photoelectric sensor can be used in different devices.
  • the sensed photoelectric signal can be used for image capture, and it can also be used for photoelectric switch, light intensity detection, touch recognition, time of flight and so on.
  • the image sensor pixel circuit 104 may include the photosensor 102 and the scanning unit 1042 coupled thereto.
  • an image sensor including such a pixel circuit may include a column/row readout amplifier circuit.
  • the positive phase input terminal of the sense amplifier circuit can be coupled to the reference voltage, and the negative phase input terminal can be coupled to the output terminal through the charge amplification capacitor and the reset switch.
  • the pixel may also include a signal amplification unit, and/or a reset unit and other functional units before the readout signal is output to the pixel.
  • Fig. 2(b) shows a working timing chart including the photoelectric sensor and the image sensor shown in Fig. 2(a).
  • the incident light is irradiated, and the photosensitive unit 1022 with light memory function can detect the input light and generate a corresponding photocurrent.
  • the integration phase/photo-generated signal accumulation phase t2 the incident light stops irradiating, but due to the light memory effect, the photo-generated current still continues to exist in the photosensitive cell.
  • the duration of the photo-generated current (which can be on the order of milliseconds) is much greater than the duration of the incident light (which can be on the order of microseconds).
  • the photo-generated current can be converted into a photo-generated voltage or charge, which is updated and retained in the storage unit 1024.
  • the integration phase t2 may also start before the exposure phase t1 has ended.
  • the so-called integration means the operation of accumulating the light-generated signal, and is not limited to any specific operation mode or circuit structure.
  • the image sensor as shown in Figure 2(b), it also includes a readout stage, during which the scanning unit can be turned on line by line, so the charge/voltage held by the memory cell can be transferred line by line to the readout amplifier. Circuit and do further filtering, noise reduction, digital processing and so on.
  • the readout method and the change of the position where the readout amplifier circuit is set belong to a well-known solution, and any changes fall within the scope of protection of the present application.
  • the integration time is less than or equal to the exposure time, or in other words, the integration operation is performed synchronously with the exposure. This is because the photo-generated current of the traditional phototransistor only exists during the exposure period, so the integration operation must also be performed during the exposure period. It is worth noting that in this application, regardless of whether the integration operation starts within the exposure time period or at a certain time point after the exposure time period, the integration operation will continue after the exposure ends. In this application, the integration time will be much longer than the exposure time, for example, the integration time length is on the order of milliseconds, and the exposure time can be on the order of microseconds.
  • the pixel circuit can obtain a longer time for the integration operation, which will significantly increase the effective photoelectric signal strength, suppress the influence of dark-state current and other noise, and thus obtain clear image data.
  • Fig. 3(a) shows a schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to an embodiment of the present application.
  • the photosensor 302 may include a photosensitive unit 3022, which is connected in series between the power supply and the node P, and also includes a storage unit.
  • the storage unit may include a storage capacitor C px , the upper plate of which is coupled to the node P, and the lower The plates receive the reference potential or are coupled to other nodes.
  • the image sensor 304 may include a photo sensor 302, and may also include a scanning unit 3042 coupled between the node P and the readout line.
  • the working principle of the photoelectric sensor and the pixel circuit in Fig. 3(a) is similar to that shown in Fig. 2(a), and will not be repeated here.
  • the capacitor C px plays two roles: (1) During the integration period, the photo-generated current is converted into the internal node voltage by using the light memory effect of the photosensitive cell; (2) In the subsequent readout process In, the photovoltaic voltage is maintained, and the influence of leakage current and voltage feedthrough effect on the readout voltage is suppressed.
  • Fig. 3(b) shows a schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to another embodiment of the present application.
  • the storage unit in the photosensor 302 may include a storage capacitor C px and an amplifying transistor M1.
  • the photo-generated current is still converted into voltage through C px , and controls the transconductance of the amplifying transistor M1. Therefore, the photo-generated current is converted into the drain-source current of M1 through C px and M1.
  • the larger the value of the photo-generated current the larger the value of the drain-source current converted to M1.
  • the photo-generated current continues to act on C px for a much longer time than the exposure time period. Therefore , the M1 drain-source current obtained by the conversion of C px and M1 will increase significantly, thereby realizing the amplification of the photo-generated current.
  • the image sensor 304 may include a photo sensor 302, and a scanning unit 3042.
  • the scanning unit 3042 (such as a scanning transistor) is in the off state, C px only modulates the transconductance of M1, and the drain-source current of M1 is almost 0; when the scanning unit 3042 is turned on, M1 controlled by C px The output current is output to an external amplifying circuit through the scanning unit 3042.
  • Fig. 3(c) shows a schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to another embodiment of the present application.
  • the amplifying transistor M2 included in the storage unit of the photosensor 302 is P-type.
  • the image sensor 304 may include a photo sensor 302 and may also include a scanning unit 3042.
  • the photo-generated current is converted into the voltage on the node P through C px , so the transconductance of the P-type transistor M2 is modulated.
  • the scanning unit 306 When the scanning unit 306 is turned on, the transistor M2 outputs a signal current to the external amplifying circuit.
  • the upper plate of the capacitor C px is coupled to the internal node P, and its lower plate receives the reference potential 1; the gate of the transistor M2 is coupled to the internal node P, and its source receives the reference potential 2. Its drain is coupled to the scanning unit 306.
  • both the reference potential 1 and the power supply voltage should be less than the value of the reference potential 2.
  • Fig. 4 shows a schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to another embodiment of the present application.
  • the photosensitive unit of the photosensor 402 may include at least a phototransistor T ph with a light memory function, and the storage unit may include an integral control transistor T int and a storage capacitor C px .
  • the image sensor pixel circuit 404 may include a photosensor 402, and may also include a scanning unit such as a scanning transistor T s .
  • the drain of the phototransistor T ph is coupled to the power source, the gate thereof is configured to receive the control signal V B , and the source thereof is coupled to the drain of the integrating control transistor T int.
  • the gate of the integral control transistor T int is configured to receive the integral control signal Int, and the source of T int is coupled to the internal node P.
  • the upper plate of the storage capacitor C px is also coupled to the internal node P, and the lower plate of C px receives the reference potential or is coupled to other nodes.
  • the gate of the scanning transistor T s in the image sensor pixel circuit 404 is configured to receive the scanning signal Scan, the drain is coupled to the internal node P, and the source is coupled to the readout line.
  • the storage unit is not limited to being implemented by C px .
  • Various circuit changes can be implemented with reference to the different memory cell structures shown in FIGS. 3(a)-(c). I won't repeat it here.
  • FIG. 4 only uses N-type transistor technology as an example to illustrate the implementation method of the image sensor pixel, but the pixel circuit can also be implemented entirely with P-type transistors, or both N-type transistors and P-type transistors are included. accomplish. Since these different circuit changes do not require creative work for those skilled in the art, they also fall into the protection scope of this application.
  • FIG. 5 is a schematic diagram showing the working sequence of the photoelectric sensor and the image sensor including the pixel circuit in FIG. 4.
  • the phototransistor T ph generates photo-generated carriers due to the irradiation of incident light, and the value of the photo-generated current I ph increases.
  • the integration control transistor T int is turned on, so the photo-generated current of the phototransistor T ph charges the storage capacitor C px through T int.
  • the Int signal becomes a low level, and the integral control transistor T int is turned off. The voltage converted from the photogenerated current is maintained by the storage capacitor C px.
  • the voltage value corresponding to the photo-generated current will be maintained by C px until the scan signals Scan1, Scan2, Scan3, etc. jump to a high level line by line, then the charge of the storage capacitor C px is transferred to the outside of the pixel circuit .
  • the integral control signal Int in FIG. 5 is shared by the entire panel. When the integral control signal Int jumps to a high level, the integral control transistors T int of all pixel circuits of the image sensor are turned on. Therefore, the global integration time is shorter than that of the line-by-line readout process.
  • the scanning transistor T s of each pixel of the image sensor is turned off during the integration period, so the integration and readout process of each pixel is performed in a time-sharing manner.
  • This readout process can effectively expand the application range of the image sensor.
  • image sensors such as touch, fingerprint recognition, and palmprint recognition often rely on flat-panel display platforms, and the actual products are highly integrated and feature-rich.
  • signal crosstalk between different functional modules such as display and sensing.
  • the driving sequence of the image sensor of the present application is not only conducive to picking up images under weak and instantaneous input light conditions, but also can be flexibly coordinated with the driving of flat panel displays and other optoelectronic devices.
  • the photoelectric sensor and image sensing pixel circuit provided by this application have high reliability.
  • the amount of charge accumulated on the capacitor C px is proportional to the amount of photo-generated current of the phototransistor T ph and the integration time, and the length of the integration time is exclusively determined by the conduction of the integration control transistor T int.
  • the amount of charge obtained by the external amplifying circuit is also uniquely determined by the amount of accumulated charge on the storage capacitor C px and the ratio of the capacitance C px to the capacitance value of the external amplifying circuit. Therefore, the photoelectric conversion relationship between the photoelectric sensor and the pixel circuit in the present application has almost nothing to do with the electrical performance of the transistor. Even if the electrical properties of the transistors T int and T s are uneven or drifted, the output voltage value of the pixel circuit remains constant.
  • the photoelectric sensor and the image sensor pixel circuit provided by the present application have high output signal strength, and can respond well to weak input light signals. Due to the light memory effect of the photosensitive unit such as the phototransistor T ph , even if the incident light has a short duration and the input photoelectric signal strength is weak, the photosensitive unit can still provide a constant photo-generated current after the incident light is removed. Therefore, the actual integrated intensity of the photo-generated current can be greatly improved by adjusting the pulse length of the integrated control signal Int signal.
  • the photoelectric sensor and the image sensing pixel circuit provided by the present application are less affected by the dark-state current.
  • the integration stage, in the photo-generated charge stored on the capacitor C px and the leakage current may be, the path may include the impact leakage branch T int, T s C px and the branch itself.
  • the leakage current value is small; for the pixel circuit, the T s branch can suppress its leakage by adjusting the low level value of the Scan signal (ie the value of the turn-off voltage) ; C px itself has a small leakage current and other factors, the dark-state noise of the pixel circuit in the embodiment of the present application is low, which is conducive to the detection of weak light signals.
  • the photosensitive cells of the photosensors and image sensor pixels are not limited to phototransistors with optical memory functions.
  • Other devices such as photodiodes and photoresistors with optical memory function can also be used to construct the photosensitive unit in this application.
  • image sensing pixel circuit embodiments are described below.
  • Fig. 6 shows a schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to another embodiment of the present application.
  • the photosensitive photosensor unit 602 may include a drain D ph such as a photodiode having a light memory function, which the cathode receives a supply voltage, is coupled to the anode of the control transistor T int of the integration.
  • Other circuit connection methods are similar to the pixel circuit shown in FIG. 4, and will not be repeated here.
  • the image sensor pixel circuit 604 may include a photoelectric 602, and may also include a scanning unit.
  • the above circuit mainly uses the effect that the reverse leakage current of the photodiode D ph is modulated by the incident light.
  • the anode or cathode metal material can be appropriately selected so that the anode metal and the active layer of the metal oxide/organic semiconductor layer or the active layer of the metal oxide/organic semiconductor layer and the cathode metal A Schottky junction diode is formed between the layers.
  • the series relationship between the photodiode D ph and the integral control tube T int may also have other configurations (not shown in the figure).
  • the gate of the integral control tube T int can receive the Int signal
  • its drain can receive the power supply voltage
  • its source can be coupled to the cathode of the photodiode D ph
  • the anode of D ph is coupled to the internal node P.
  • Other connections can be It is similar to the embodiment shown in FIG. 6.
  • FIG. 7 shows a schematic diagram of a photoelectric sensor and an image sensor pixel circuit according to another embodiment of the present application.
  • the photosensitive unit of the photosensor 702 may include a photosensitive resistor R ph with a light memory function.
  • the image sensor pixel circuit 604 may include a photoelectric 602, and may also include a scanning unit.
  • R ph photoresistor first terminal may receive a supply voltage, a second terminal coupled to the drain of R ph control transistor T int of the integration.
  • the connection mode of the photoresistor R ph and the integral control transistor T int may also have other changes (not shown in the figure).
  • a gate receiving the control transistor T int Points Points control signal Int, a drain receiving a power supply voltage, its source coupled to a first terminal of the photoresistor R ph, a second terminal coupled to the R ph photoresistor inside the pixel circuits Node P.
  • Other circuit connection methods are similar to the pixel circuit shown in FIG. 4, and will not be repeated here.
  • FIG. 8 shows a schematic diagram of the structure of an image sensor according to an embodiment of the present application.
  • the image sensor may include a pixel array, a scanning control circuit, and a readout circuit.
  • the scanning circuit can be used to provide the corresponding progressive scanning control signal, integral control signal, the bias voltage required by the photosensitive unit, and so on.
  • the readout circuit may not only include the operational amplifier circuit, reset transistor, coupling capacitor, etc., as illustrated in the foregoing embodiments, but may also include an analog-to-digital conversion module, a filter module, and the like.
  • part or all of the scan control circuit and the readout circuit may also be implemented by metal oxide semiconductor transistors or organic semiconductor devices.
  • the peripheral driving circuit and the pixel array can be prepared by the same process as the photosensitive unit, so as to reduce the number of connection lines around the image sensor module and improve the integration and reliability of the image sensor.
  • i is an integer greater than or equal to 1 and less than or equal to N.
  • the parasitic capacitance of the transistors of these scanning units contributes to the parasitic capacitance C P of the j-th read-out line; and there may be overlaps between the j-th read-out line and the N scan lines.
  • the overlap capacitance contributes to the parasitic capacitance C P Also contributed.
  • the parasitic capacitance C P reduces the value of the readout voltage of the pixel circuit of the conventional image sensor.
  • the light output current can be continuously and stably provided in the case of weaker light/shorter light input, so the memory unit is programmed , Stores a strong photo-generated charge/photo-generated voltage signal, which can reduce the impact of parasitic capacitance C P on the image sensor.
  • Fig. 9 shows a photoelectric sensing method according to an embodiment of the present application.
  • a photosensitive unit with a light memory function senses incident light and generates a photo-generated current during the exposure stage.
  • the photosensitive cell with optical memory function may include a metal oxide semiconductor or organic semiconductor photosensitive cell with optical memory function.
  • the photo-generated current is converted into a photo-generated charge or voltage in an integration phase, and the photo-generated charge or voltage is stored or maintained, wherein the integration phase includes at least a preset time period after the exposure phase ends.
  • a storage unit may also be used to amplify the photo-generated charge or voltage.
  • the integration phase may also include a time period overlapping with the exposure phase.
  • the time of the integration phase is longer than the time of the exposure phase.
  • the integration phase also includes a time period coincident with the exposure phase.

Abstract

本申请提供了一种光电传感器，包括光敏单元，配置为在曝光阶段接收入射光并产生光生电流，其具有光记忆功能，即入射光撤除后仍然在所述光敏单元内保持光生电流；以及存储单元，耦合到所述光敏单元，配置为在积分阶段将所述光生电流转化为光生电荷或光生电压并进行存储或保持，其中所述积分阶段至少包括曝光阶段结束后的预设时间段。本申请还提供了包括这种光电传感器的像素电路、包含这种像素阵列的图像传感器和电子设备以及相应的光电感测方法。

Description

光电传感器、像素电路、图像传感器及光电感测方法 技术领域
本申请涉及一种图像传感器，特别地涉及一种具有光记忆功能的光敏单元的光电传感器、像素电路、图像传感器以及相应的光电感测方法。
背景技术
光电传感器和图像传感器在众多医疗电子、消费电子、军用电子设备中起到极端重要的作用。例如，X射线影像是骨科、肺病、心脑血管等各类疾病诊断的黄金判据；指纹识别已经成为智慧手机的标准安全锁；高光谱、多光谱摄像是重要的现代军事侦测手段。在这些应用中，面向微弱光信号、瞬态光电信号的高灵敏度、高分辨率的光电传感器和图像传感器一直是研究的重点。
以现代医疗不可或缺的X射线影像设备为例，自X射线发现至今的100多年以来，借助X射线的穿透能力摄取人体内组织图像的医用X射线成像系统中，图像传感器是核心部件。低剂量、高分辨、动态成像是现代X射线成像的主要发展方向，其中对图像传感器的要求是灵敏度高、信噪比高、响应速度快等。现有的图像传感器技术可以分为如下几类：基于电荷耦合器件(CCD)和互补金属氧化物(CMOS)晶体管的成像技术，和基于氢化非晶硅(a-Si:H)光电二极管的平板探测成像技术。目前，最主流的X射线图像传感器是基于a-Si:H光电二极管技术。虽然该技术在不断地进步之中，但是仍然存在很多问题。当今X射线医学成像的应用中最重要的研究方向之一是提高图像传感器灵敏度以减小X射线辐照剂量，降低对人体的伤害。又比如导弹尾焰探测等军事应用中，探测距离远造成可用于成像的光电信号强度极其微弱，而事件的变化 速度快则要求光电成像的响应速度极快。
如何对微弱的、瞬态光电信号实施侦测是光敏传感器和图像传感器设计的难题。随着入射光电信号强度的减少，传统图像传感器读出阵列的输出信号强度极大地减少，因此成像质量会受到暗态电流、信号噪声的影响而急剧下降。进一步地，当图像传感器的分辨率提高时，像素面积也相应地减小，成像单元的信噪比和灵敏度会大大下降，这也是传统图像传感器实现高分辨率的限制因素。
发明内容
针对现有技术的问题，本申请提出了一种光电传感器，包括光敏单元，配置为在曝光阶段接收入射光并产生光生电流，其具有光记忆功能，即入射光撤除后仍然在所述光敏单元内保持光生电流；以及存储单元，耦合到所述光敏单元，配置为在积分阶段将所述光生电流转化为光生电荷或光生电压并进行存储或保持，其中所述积分阶段至少包括曝光阶段结束后的预设时间段。
特别的，所述具有光记忆功能的光敏单元包括具有光记忆功能的金属氧化物半导体器件或有机半导体器件。
特别的，所述光敏单元至少包括光电晶体管，光电二极管或光敏电阻。
特别的，所述存储单元包括存储电容，其耦合到所述光敏单元，所述存储电容配置为执行将所述光生电流转化为所述光生电荷或光生电压的积分操作。
特别的，所述存储单元还包括积分控制单元，其耦合在所述光敏单元和所述存储电容之间，配置为在积分控制信号的影响下控制进行所述积分操作的时间。
特别的，积分控制单元包括积分晶体管，其第一极和第二极分别耦合到所述存储电容与所述光敏单元，或者分别耦合到所述光敏单元与电源，其控制极配置为接收积分控制信号。
特别的，所述存储单元还包括放大单元，其耦合到所述存储电容，配置为对所述光生电荷或者电压进行放大。
特别的，所述积分阶段的时间比所述曝光阶段时间长。
特别的，所述积分阶段还包括与所述曝光阶段重合的时间段。
本申请还提供了一种像素电路，包括如前任一所述的光电传感器，以及扫描单元，其耦合到所述光电传感器的存储单元，配置为在扫描信号的控制下将所述光生电流信号或电压信号或相应的电学信号输出到像素电路外。
特别的，在所述光电传感器包括放大单元的情况下，所述放大单元包括N型放大晶体管，其第一极耦合到所述扫描单元，其控制极和第二极分别耦合到所述存储电容的第一和第二极板。
特别的，在所述光电传感器包括放大单元的情况下，所述放大单元包括P型放大晶体管，其控制极耦合到所述存储电容的第一极板，所述电容的第二极板耦合到第一参考电位，其第一极耦合到第二参考电位，其第二极耦合到所述扫描单元，其中所述第二参考电位高于所述第一参考电位和电源电压。
本申请还提供了一种图像传感器，包括像素阵列，和与其耦合的扫描控制电路和读出电路；其中所述像素阵列包括一个或多个如前任一所述的像素电路。
特别的，所述扫描控制电路和所述读出电路中的器件由金属氧化物半导体或有机半导体工艺制成。
本申请还提供了一种电子设备，其包括如前任一所述的光电传感器或如前任一所述的图像传感器。
本申请还提供了一种光电感测方法，包括在曝光阶段内由具有光记忆功能的光敏单元感测入射光并产生光生电流；以及在积分阶段内将所述光生电流转化为光生电荷或电压，并对所述光生电荷或电压进行存储或保持，其中所述积分阶段至少包括曝光阶段结束后的预设时间段。
特别的，所述积分阶段的时间比所述曝光阶段时间长。
特别的，所述积分阶段还包括与所述曝光阶段重合的时间段。
附图说明
下面，将结合附图对本申请的实施方式进行进一步详细的说明，其中：
图1所示为根据本申请一个实施例的具有光记忆功能的光电晶体管的工作模式示意图；
图2(a)所示为根据本申请一个实施例的光电传感器和图像传感器像素电路的模块化示意图；
图2(b)所示为包括图2(a)所示光电传感器和图像传感器工作时序图；
图3(a)所示为根据本申请一个实施例的光电传感器和图像传感器像素电路示意图；
图3(b)所示为根据本申请另一个实施例的光电传感器和图像传感器像素电路示意图；
图3(c)所示为根据本申请又一实施例的光电传感器和图像传感器像素电路示意图；
图4所示为根据本申请另一个实施例的光电传感器和图像传感器像素电路示意图；
图5所示为包括图4中光电传感器和像素电路的图像传感器工作时序示意图；
图6所示为根据本申请另一个实施例的光电传感器和图像传感器像素电路示意图；
图7所示为根据本申请又一实施例的光电传感器和图像传感器像素电路示意图；
图8所示为根据本申请一个实施例的图像传感器结构示意图；以及
图9所示为根据本申请一个实施例的图像感测方法。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
本申请中的晶体管可以为双极型晶体管或者场效应晶体管。所述晶体管包括控制极、第一极及第二极，控制极耦合到控制金属层，第一极及第二极耦合到具有光记忆功能的有源层，控制金属层及半导体层之间具有介质层。所述光电晶体管的具有光记忆功能的有源层的电导特性受到输入光的调制而发生变化。当晶体管为双极型晶体管时，控制极指双极型晶体管的基极，第一极指双极型晶体管的集电极或者发射极，对应的第二极为双极型晶体管的发射极或者集电极；当晶体管为场效应晶体管时，控制极是指场效应晶体管的栅极，第一极可以为场效应晶体管的漏极或源极，对应的第二极可以为场效应晶体管的源极或漏极。通常在N型晶体管中，漏极的电压应该大于或等于源极的电压，因此源极漏极的位置会随晶体管偏置状态的不同而变化。由于在显示器中使用的晶体管通常为薄膜晶体管(TFT)，因此本申请实施例不妨以薄膜晶体管为例进行说明，且本申请实施例中晶体管的漏极和源极可以根据晶体管偏置状态的不同而变化。
本申请提出光电传感器、像素电路及图像传感器是基于具有光记忆功能的光敏单元来提升瞬态、低剂量光输入情况下的成像质量。所谓光敏单元的光记忆功能是指，在曝光结束，光敏单元接收输入光并产生光生电流；而曝光结束后，即使入射光撤除，光敏单元仍然在预设时间段内保持所述光生电流。
有研究表明，具有光记忆功能并且可以作为有源层或者说光敏功能层的材料包括无机半导体中的金属氧化物半导体(例如，由于禁带宽度较窄和氧空位浓度较高，氧化铟锌IZO的光电响应强度较高，且具有较好的光记忆功能)，和一些有机半导体等。具体来说，在外界光照作用下，具有光记忆功能的光敏单元与其他类型的光敏单元一样，可以产生出光生载流子，进而具有输入光调制的电导或者电流。但不同的是，由于晶格弛豫过程，使得基于这种材料的光敏单元具有显著的光记忆性。例如，金属氧化物半导体光电晶体管中的光生载流子的复合消失需要极长时间，因此在这种光敏单元中光生电流可维持较长的时间。又例如，反向偏置的金属氧化物半导体光电二极管，光生电流的值可持续数小时以上，远超过光电读出侦测所需要的时间长度。在例如金属氧化物半导体光敏电阻在光照作用下，其电阻值会发生改变，且具有持续保持这种电阻状态的能力。
在本申请中的方案中，利用了例如金属氧化物半导体和有机半导体材料的光记忆特性，以增强光敏单元的光电转换能力，提高光电传感器或图像传感器的信噪比和灵敏度。在入射光电信号微弱或者照射时间短的应用中，例如在X射线医学影像设备中，利用金属氧化物半导体光敏单元的光记忆特性，可以在降低X射线曝光时间避免对人体造成伤害的同时还能保证获得清晰的图像。
图1所示为根据本申请一个实施例的具有光记忆功能的光电晶体管的工作模式示意图。当然，除了光电晶体管外，还可以有其他形式的具有光记忆功能的光敏单元，例如光电二极管或者光敏电阻等等。这里仅仅是以光电晶体管为例来进一步介绍具有光记忆功能的光敏单元的特点。在暗态时，光电晶体管的输出电流为Idk；在曝光时间段，由于入射光输入，光电晶体管的输出电流上升到Iph0。后续在入射光停止后的时间段，光电晶体管的输出电流为Iph1，与Iph0相比有所下降，但是下降幅度有限，基本可以认为光生电流在曝光阶段前后保持不变。因此，在以下的介绍中在曝光阶段和积分阶段或者光电信号 累积阶段中光敏单元中的电流都是光生电流。
图2(a)所示为根据本申请一个实施例的光电传感器和图像传感器像素的模块化示意图。
如图2(a)所示，光电传感器102可以包括，具有光记忆功能的光敏单元1022、以及耦合到光敏单元1022的存储单元1024。光电传感器可以应用在不同的设备中，例如可以将所感测到的光电信号用于图像捕捉，也可以用于光电开关、光强检测、触控识别、飞行时间测距(Time of flight)等。
根据一个实施例，如图2(a)所示，当光电传感器用于图像捕捉时，图像传感器像素电路104可以包括光电传感器102以及与其耦合的扫描单元1042。根据其他实施例，包含这种像素电路的图像传感器可以包括列/行读出放大电路。根据一个实施例，读出放大电路的正相输入端可以耦合到参考电压，负相输入端通可过电荷放大电容和复位开关耦合到输出端子。根据其他的实施例，该像素内部在读出信号被输出像素以前也可以包括信号放大单元，和/或重置单元等等功能单元。
图2(b)所示为包括图2(a)所示的光电传感器和图像传感器的工作时序图。
对于光电传感器或图像传感器来说都存在曝光阶段和积分阶段/光生信号累积阶段。
在曝光阶段t1，入射光照射，具有光记忆功能的光敏单元1022可以侦测到输入光，并产生出相应的光电流。
在积分阶段/光生信号累积阶段t2，入射光停止照射，但是由于光记忆效应，光敏单元中仍然持续存在光生电流。根据一个实施例，光生电流持续时间(可以是毫秒量级)远大于入射光持续时间(可以是微秒量级)。在此阶段，光生电流可以被转化为光生电压或者电荷，并更新后保持于存储单元1024中。根据其他实施例，积分阶段t2也可以在曝光阶段t1还未结束时就已经开始。所谓积分的含义即对光生信号进行累积的操作，并不局限于任何一种具体的操 作方式或者电路结构。
针对图像传感器来说，如图2(b)所示，还包括读出阶段，在这个阶段扫描单元可以被逐行打开，于是存储单元保持的电荷/电压可以被逐行地传输到读出放大电路并做进一步的滤波、降噪、数字化处理等。当然，读出方式和设置读出放大电路的位置的变换属于公知的方案，无论如何变化都属于本申请保护的范围。
在现有的光电传感器或图像传感器中，积分时间小于等于曝光时间，或者说，积分操作与曝光同步进行。这是因为传统的光电晶体管的光生电流只在曝光时间段内存在，因此积分操作也必须在曝光阶段进行。值得注意的是，本申请中无论积分操作是在曝光时间段内就开始还是在曝光时间段之后的某一时间点开始，积分操作都会在曝光结束后继续进行。本申请中积分时间会远长于曝光时间，例如积分时间长度为毫秒量级，而曝光时间可以是微秒量级。这恰恰是因为，对于具有光记忆功能的光敏单元来说，光生电流可以在入射光撤除之后仍然被保持或者说被记忆。因此像素电路可以获得较长的时间来进行积分操作，这将显著提升有效光电信号强度、抑制暗态电流及其他噪声量的影响，从而获得清晰的图像数据。
图3(a)所示为根据本申请一个实施例的光电传感器和图像传感器像素电路示意图。其中，光电传感器302可以包括光敏单元3022，其串接在电源和节点P之间；还包括存储单元，根据一个实施例存储单元可以包括存储电容C px，其上极板耦合到节点P，下极板接收参考电位或者耦合到其他节点。根据一个实施例，图像传感器304可以包括光电传感器302，此外还可以包括扫描单元3042耦合在节点P及读出线之间。图3(a)光电传感器和像素电路的工作原理与图2(a)所示的类似，在此不做赘述。
在这个实施例中，电容C px起到了两个作用：(1)在积分时间段内，利用光敏单元的光记忆效应，将光生电流转化为内部节点电压；(2)在后续的读出 过程中，保持光生电压，抑制泄漏电流及电压馈通效应等对读出电压的影响。
图3(b)所示为根据本申请另一个实施例的光电传感器和图像传感器像素电路示意图。其中，光电传感器302中的存储单元可以包括存储电容C px和放大晶体管M1。这里光生电流仍然通过C px被转化为电压，且控制着放大晶体管M1的跨导。因此，光生电流通过C px及M1被转化为M1的漏源电流。光生电流的值越大，对应地转化到M1的漏源电流的值就越大。并且由于光记忆效应，光生电流持续作用于C px的时间比曝光时间段要长很多，因此通过C px和M1转化得到的M1漏源电流将显著增大，从而实现对光生电流的放大。
根据一个实施例，图像传感器304可以包括光电传感器302，以及扫描单元3042。当扫描单元3042(例如扫描晶体管)处在断开状态时，C px只是调制了M1的跨导，M1的漏源电流几乎为0；当扫描单元3042被开启之后，被C px控制着的M1输出电流，通过扫描单元3042输出到外部的放大电路。
图3(c)所示为根据本申请又一实施例的光电传感器和图像传感器像素电路示意图。在这个实施例中，光电传感器302的存储单元中包括的放大晶体管M2为P型。根据一个实施例，图像传感器304可以包括光电传感器302，还可以包括扫描单元3042。
在积分阶段内，光生电流通过C px被转化为节点P上的电压，于是对P型晶体管M2的跨导进行调制。当扫描单元306被打开时，晶体管M2输出信号电流到外部放大电路。图3(c)所示意的结构中，电容C px的上极板耦合到内部节点P，其下极板接收参考电位1；晶体管M2的栅极耦合到内部节点P，其源极接收参考电位2，其漏极耦合到扫描单元306。为了使得晶体管M2可被正常地打开，参考电位1和电源电压都应该小于参考电位2的值。
根据不同的实施例，除了图3(b)和图3(c)所示的晶体管M1和M2以外，还可以包括其他类型的内部放大单元。但是无论采用什么放大手段或者方式来放大与光生电荷或光生电压相应的信号，都属于常规的手段，仍然落入本 申请的保护范围内。
图4所示为根据本申请另一个实施例的光电传感器和图像传感器像素电路示意图。该光电传感器402的光敏单元可以至少包括具有光记忆功能的光电晶体管T ph，存储单元可以包括积分控制晶体管T int和存储电容C px。根据一个实施例，图像传感器像素电路404可以包括光电传感器402，还可以包括扫描单元例如扫描晶体管T s。
具体来说，光电晶体管T ph的漏极耦合到电源，其栅极配置为接收控制信号V B，其源极耦合到积分控制晶体管T int的漏极。
如图4所示，积分控制晶体管T int的栅极配置为接收积分控制信号Int，T int的源极耦合到内部节点P。存储电容C px的上极板也耦合到内部节点P，C px的下极板接收参考电位或耦合到其他节点。
如图4所示，图像传感器像素电路404中的扫描晶体管T s的栅极配置为接收扫描信号Scan，其漏极耦合到内部节点P，其源极耦合到读出线。
图4所示意的光电传感器或图像传感像素电路中，存储单元并不局限为采用C px实现。可参照图3(a)-(c)所示意的不同存储单元结构，实现各种电路变化。这里不再赘述。此外，图4仅仅用N型的晶体管技术作为例子说明该图像传感像素的实现方法，但是该像素电路也可以全部用P型晶体管来实现，或者是既包括N型晶体管，又包括P型晶体管实现。由于这些不同电路变化对于本领域技术人员来说不需要付出创造性劳动，因此也落入本申请保护范围。
图5所示为包括图4中像素电路的光电传感器和图像传感器工作时序示意图。在曝光阶段t1，光电晶体管T ph因入射光的照射而产生光生载流子，光生电流I ph的值增加。当Int信号为高电平的阶段对应积分阶段t2，积分控制晶体管T int被打开，于是光电晶体管T ph的光生电流通过T int给存储电容C px充电。之后，Int信号变成低电平，积分控制晶体管T int被关断。光生电流转化所得的电压被存储电容C px保持。在读出阶段，光生电流对应的电压值将一直被C px 保持，直到扫描信号Scan1、Scan2、Scan3等逐行跳变到高电平，则存储电容C px的电荷被转移到像素电路之外。
由图5可见，积分时间t2与曝光时间t1之间可以是存在时间间隔的。在实际应用中，光敏单元中产生的光生电流的上升时需要一定的时间，因此，可以在曝光时间后设置特定的时间间隔再开始进行积分，这也是为了让光生电流在足够的响应时间之后上升到较稳定的值，从而提高积分操作的精度。对于图像传感器来说，图5中积分控制信号Int是整个面板共用的，当积分控制信号Int跳变到高电平后，图像传感器所有像素电路的积分控制晶体管T int均为开启状态。故该全局积分时间相对于逐行读出过程来说，所占的时间是较短的。
根据一个实施例，图像传感器各像素的扫描晶体管T s在积分时间段都被关断，因此各像素的积分以及读出过程是分时进行的。这种读出过程可以有效地拓展图像传感器的使用范围。例如，在消费电子产品中，触控、指纹识别、掌纹识别等图像传感器经常依托于平板显示平台，实际成品的集成度高、功能丰富。然而由于集成度的提高、物理距离越来越小，显示及传感等不同功能模块之间不可避免地存在信号串扰现象。为了抑制显示驱动信号与图像传感器之间的串扰，一般需要显示和图像传感读出过程分时进行。于是，在图像传感器的积分阶段，可进行显示驱动；而图像传感器的读出阶段，可停止显示驱动。因此，本申请的图像传感器的驱动时序不仅有利于拾取微弱、瞬时输入光情况下的图像，而且可灵活地与平板显示器的驱动等其他光电设备的协同操作。
本申请所提供的光电传感器和图像传感像素电路具有较高的可靠性。电容C px上积累电荷的量，正比于光电晶体管T ph的光生电流量以及积分时间，而积分时间的长度则由积分控制晶体管T int的导通唯一决定。对于图像传感器像素来说，外部放大电路得到的电荷量也唯一地由存储电容C px上的累积电荷量、以及电容C px和外部放大电路的电容值的比例决定。因此，本申请中的光电传感器和像素电路的光电转化关系几乎与晶体管的电学性能无关。即使晶体管 T int和T s的电学性能存在不均匀或者漂移的情况，像素电路的输出电压值仍然保持恒定。
另外，本申请所提供的光电传感器和图像传感像素电路的输出信号强度较高，可对微弱输入光信号有较好的响应。由于光敏单元例如光电晶体管T ph的光记忆效应，即使入射光持续时间短、输入光电信号强度弱，在入射光撤走后，光敏单元仍然能够恒定地提供出光生电流。因此实际光生电流积分强度可以通过调整积分控制信号Int信号的脉冲长度而极大地被提高。
并且，本申请所提供的光电传感器和图像传感像素电路受暗态电流的影响较小。在积分阶段，存储于电容C px上的光生电荷可能受到泄漏电流影响，可能造成影响的路径包括T int支路、T s支路及C px本身的泄漏。考虑到T int支路串联晶体管数量较多，泄漏电流值较小；对于像素电路来说，T s支路可通过调整Scan信号的低电平值(即关断电压的值)，抑制其漏电；C px本身泄漏电流较小等因素，本申请实施例中的像素电路的暗态噪声较低，有利于对微弱光信号的侦测。
根据不同的实施例，光电传感器和图像传感器像素的光敏单元所包含的并不局限于具有光记忆功能的光电晶体管。具有光记忆功能的光电二极管、光敏电阻等其他器件也都可以用来构造本申请中的光敏单元。以下介绍另外几种图像传感像素电路实施例。
图6所示为根据本申请另一个实施例的光电传感器和图像传感器像素电路示意图。其中光电传感器602的光敏单元可以包括例如具有光记忆功能的光电二极管D ph，其阴极接收电源电压，阳极耦合到积分控制晶体管T int的漏极。其他的电路连接方式与图4所示的像素电路类似，这里不再赘述。根据一个实施例，图像传感器像素电路604可以包括光电602，还可以包括扫描单元。
上述电路主要用到光电二极管D ph的反向泄漏电流受到入射光调制的效应。为了增强光电二极管的光记忆效应，可以适当地选取其阳极或者阴极金属材 料，使得其阳极金属与例如金属氧化物/有机半导体层有源层或者金属氧化物/有机半导体层有源层与阴极金属层之间形成肖特基结二极管。
根据另一个实施例，光电二极管D ph和积分控制管T int的串联关系也可能有其他的配置方式(图中未示出)。例如，积分控制管T int的栅极可以接收Int信号，其漏极可以接收电源电压,其源极可以耦合到光电二极管D ph的阴极，D ph的阳极耦合到内部节点P，其他连接关系可和图6所示的实施例类似。
图7所示为根据本申请又一实施例的光电传感器和图像传感器像素电路示意图。其中，光电传感器702的光敏单元可以包括具有光记忆功能的光敏电阻R ph。根据一个实施例，图像传感器像素电路604可以包括光电602，还可以包括扫描单元。光敏电阻R ph的第一端子可以接收电源电压，R ph的第二端子耦合到积分控制晶体管T int的漏极。此外，光敏电阻R ph和积分控制晶体管T int的连接方式也可能有其他的变化(图中未示出)。例如，积分控制晶体管T int的栅极接收积分控制信号Int，其漏极接收电源电压,其源极耦合到光敏电阻R ph的第一端子，光敏电阻R ph的第二端子耦合到像素电路内部节点P。其他的电路连接方式与图4所示的像素电路类似，这里不再赘述。
图8所示为根据本申请一个实施例的图像传感器结构示意图。该图像传感器可以包括，像素阵列，扫描控制电路，以及读出电路。扫描电路可以用于提供相应的逐行扫描控制信号、积分控制信号、光敏单元所需要的偏置电压等。读出电路不仅可以包括前述实施例中示意的运算放大电路、复位晶体管、耦合电容等，还可以包括模数转化模块、滤波模块等。
根据一个实施例，扫描控制电路以及读出电路的部分或全部，也可由金属氧化物半导体晶体管或者有机半导体器件实现。换言之，周边驱动电路与像素阵列可以用与光敏单元相同的工艺制备得到，以减少图像传感器模组周边的连接线数量，提高图像传感器的集成度及可靠性。
对于例如包括N行*M列像素阵列的传统图像传感器来说，第i行像素的扫 描单元被打开时，第i行的M个像素中的图像传感数据可以分别被相应列的读出放大电路拾取并转化为输出电压信号。其中，i为大于等于1并且小于等于N的整数。对于第j条读出线，其中j为大于等于1并且小于等于M的整数，其上具有不可忽略的寄生电容C P，这是因为第j条读出线耦合到N个像素电路的扫描单元，这些扫描单元的晶体管寄生电容对第j条读出线的寄生电容C P有贡献；并且第j条读出线与N根扫描线都可能存在交叠，该交叠电容对寄生电容C P也有贡献。寄生电容C P降低了传统图像传感器像素电路读出电压的值。
但是在采用本申请提出的具有光记忆功能的图像传感器或者包括这样图像传感器的电子设备时，在较弱光照/较短光输入情况下，可持续、稳定提供出光输出电流，因此存储单元被编程、存储着较强的光生电荷/光生电压信号，可降低寄生电容C P对图像传感器的影响。
图9所示为根据本申请一个实施例的光电感测方法。
在902，在曝光阶段内由具有光记忆功能的光敏单元感测入射光并产生光生电流。根据一个实施例，具有光记忆功能的光敏单元可以包括具有光记忆功能的金属氧化物半导体或者有机半导体光敏单元。
在904，在积分阶段内将所述光生电流转化为光生电荷或电压，并对所述光生电荷或电压进行存储或保持，其中所述积分阶段至少包括曝光阶段结束后的预设时间段。根据一个实施例，也可以利用存储单元对所述光生电荷或电压进行放大。根据一个实施例，积分阶段也可以包括与曝光阶段重叠的时间段。
其中，积分阶段的时间比所述曝光阶段时间长。特别的，积分阶段还包括与曝光阶段重合的时间段。
利用本申请所提供的光电传感器、图像传感器和相应的方法，可以在曝光时间短、入射光强度比较弱的应用场景中仍然可以可靠地获得清晰的图像，同时还降低了暗电流、寄生电容等等负面因素对所捕捉的光电信号质量的影响。
上述实施例仅供说明本申请之用，而并非是对本申请的限制，有关技术领域的普通技术人员，在不脱离本申请范围的情况下，还可以做出各种变化和变型，因此所有等同的技术方案也应属于本申请公开的范畴。

Claims (18)

  1. 一种光电传感器，包括：
    光敏单元，配置为在曝光阶段接收入射光并产生光生电流，其具有光记忆功能，即入射光撤除后仍然在所述光敏单元内保持光生电流；以及
    存储单元，耦合到所述光敏单元，配置为在积分阶段将所述光生电流转化为光生电荷或光生电压并进行存储或保持，其中所述积分阶段至少包括曝光阶段结束后的预设时间段。
  2. 如权利要求1所述的光电传感器，其中所述具有光记忆功能的光敏单元包括具有光记忆功能的金属氧化物半导体器件或有机半导体器件。
  3. 如权利要求2所述的光电传感器，其中所述光敏单元至少包括光电晶体管，光电二极管或光敏电阻。
  4. 如权利要求1所述的光电传感器，其中所述存储单元包括存储电容，其耦合到所述光敏单元，所述存储电容配置为执行将所述光生电流转化为所述光生电荷或光生电压的积分操作。
  5. 如权利要求4所述的光电传感器，其中所述存储单元还包括积分控制单元，其耦合在所述光敏单元和所述存储电容之间，配置为在积分控制信号的影响下控制进行所述积分操作的时间。
  6. 如权利要求5所述的光电传感器，其中积分控制单元包括积分晶体管，其第一极和第二极分别耦合到所述存储电容与所述光敏单元，或者分别耦合到所述光敏单元与电源，其控制极配置为接收积分控制信号。
  7. 如权利要求4所述的光电传感器，其中所述存储单元还包括放大单元，其耦合到所述存储电容，配置为对所述光生电荷或者电压进行放大。
  8. 如权利要求1-7中任一所述的光电传感器，其中所述积分阶段的时间比所述曝光阶段时间长。
  9. 如权利要求8所述的光电传感器，其中所述积分阶段还包括与所述曝光 阶段重合的时间段。
  10. 一种像素电路，包括如权利要求1-9任一所述的光电传感器，以及扫描单元，其耦合到所述光电传感器的存储单元，配置为在扫描信号的控制下将所述光生电流信号或电压信号或相应的电学信号输出到像素电路外。
  11. 如权利要求10所述的像素电路，其中在所述光电传感器包括放大单元的情况下，所述放大单元包括N型放大晶体管，其第一极耦合到所述扫描单元，其控制极和第二极分别耦合到所述存储电容的第一极板和第二极板。
  12. 如权利要求10所述的像素电路，其中在所述光电传感器包括放大单元的情况下，所述放大单元包括P型放大晶体管，其控制极耦合到所述存储电容的第一极板，所述电容的第二极板耦合到第一参考电位，其第一极耦合到第二参考电位，其第二极耦合到所述扫描单元，其中所述第二参考电位高于所述第一参考电位和电源电压。
  13. 一种图像传感器，包括像素阵列，和与其耦合的扫描控制电路和读出电路；其中所述像素阵列包括一个或多个如权利要求1-12中任一所述的像素电路。
  14. 如权利要求13所述的图像传感器，其中所述扫描控制电路和所述读出电路中的器件由金属氧化物半导体或有机半导体工艺制成。
  15. 一种电子设备，包括如权利要求1-12中任一所述的光电传感器或权利要求13-14中任一所述的图像传感器。
  16. 一种光电感测方法，包括
    在曝光阶段内由具有光记忆功能的光敏单元感测入射光并产生光生电流；以及
    在积分阶段内将所述光生电流转化为光生电荷或电压，并对所述光生电荷或电压进行存储或保持，其中所述积分阶段至少包括曝光阶段结束后的预设时间段。
  17. 如权利要求16所述的方法，其中所述积分阶段的时间比所述曝光阶段 时间长。
  18. 如权利要求17所述的方法，其中所述积分阶段还包括与所述曝光阶段重合的时间段。
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