Active pixel sensor and flat panel detector

Abstract

The application provides an active pixel sensor and a flat panel detector. The active pixel sensor provided by the embodiment of the present application comprises a photosensitive device, a follower transistor, an adjusting sub-circuit and a reading transistor. The control electrode of the follower transistor is connected with the first electrode of the photosensitive device, and the first electrode is connected with a first power supply voltage terminal; wherein the first power supply voltage terminal is used for providing a first power supply voltage; the adjusting sub-circuit is configured to adjust the amplification sensitivity of the follower transistor in response to a first control signal; the control electrode of the reading transistor is connected with a scanning line, the first electrode is connected with the second electrode of the follower transistor, and the second electrode is connected with a reading line; wherein the scanning line is used for providing a scanning signal. The active pixel sensor provided by the embodiment can adjust its detection sensitivity and adapt to various types of detection.

Description

Technical Field

[0001] This invention belongs to the field of biochip technology, specifically relating to an active pixel sensor and a flat panel detector. Background Technology

[0002] Flat panel detectors are used for indirect digital X-ray imaging. Their basic structure includes an X-ray conversion layer and a photoelectric conversion layer beneath it. The photoelectric conversion layer comprises multiple arrays of passive or active pixel sensors that convert optical signals into electrical signals and read them out. Due to their high signal-to-noise ratio, active pixel sensors are widely used in flat panel detectors. The active pixel sensor includes a photosensitive element and its readout circuitry. The X-ray conversion layer converts attenuated X-rays into visible light. The photosensitive element detects the visible light, converts it into an electrical signal, and the readout circuitry reads it out, transmitting the signal to a computer for image processing to perform digital X-ray imaging.

[0003] In medical flat panel detectors, industrial detectors, and low-dose detection, the intensity of the signal read by the readout circuit decreases significantly due to smaller pixels or reduced doses, leading to a deterioration in the signal-to-noise ratio. Active pixel sensors can amplify the readout signal, but their gain factor (i.e., amplification sensitivity) is typically fixed, limiting their applicability to a limited range of detection scenarios. For example, if the amplification sensitivity is high, the electrical signal will saturate rapidly in some detection scenarios, making it difficult to further increase the detected signal without improving image quality, thus hindering detection with a wide range of signal variations. Conversely, if the amplification sensitivity is low, changes in visible light intensity may be difficult to detect in other detection scenarios, making it hard to detect changes in the electrical signal. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art, and provide an active pixel sensor that can adjust its detection sensitivity to adapt to various types of detection.

[0005] In a first aspect, embodiments of this disclosure provide an active pixel sensor, including: a photosensitive device;

[0006] The control electrode of the follow transistor is connected to the first electrode of the photosensitive device, and the first electrode is connected to the first power supply voltage terminal; wherein, the first power supply voltage terminal is used to provide the first power supply voltage;

[0007] A regulating sub-circuit is configured to adjust the amplification sensitivity of the follower transistor in response to a first control signal;

[0008] A read transistor has its control electrode connected to a scan line, its first electrode connected to the second electrode of the follower transistor, and the second electrode connected to the read line; wherein the scan line is used to provide a scan signal.

[0009] The active pixel sensor provided in this embodiment incorporates an adjustment sub-circuit. This sub-circuit can adjust the amplification sensitivity of the follower transistor. Therefore, by adjusting the amplification sensitivity of the follower transistor, the active pixel sensor can adapt to various types of detection. For example, if the signal change of the photosensitive device is small, the adjustment sub-circuit can make the follower transistor have a high amplification sensitivity, so that the active pixel sensor can detect minute changes in the signal of the photosensitive device. If the signal change of the photosensitive device is large and the detection range is large, the adjustment sub-circuit can reduce the amplification sensitivity of the follower transistor, thereby avoiding rapid signal saturation and giving the active pixel sensor a larger detection range.

[0010] In some examples, the regulating sub-circuit is configured to adjust the potential between the control electrode of the follower transistor and the first electrode of the follower transistor in response to a first control signal.

[0011] In some examples, the regulating sub-circuit includes a first capacitor, a second capacitor, and a switching transistor;

[0012] The first terminal of the first capacitor is connected to the first terminal of the switching transistor; the first terminal of the second capacitor is connected to the second terminal of the switching transistor; and the second terminals of both the first and second capacitors are connected to the control terminal of the follower transistor.

[0013] In some examples, the regulating sub-circuit is a voltage-controlled liquid crystal capacitor.

[0014] In some examples, the regulating sub-circuit includes a varactor diode.

[0015] In some examples, the varactor diode is a PIN diode or a PN diode.

[0016] In some examples, the regulating circuit is an amorphous metal nonlinear resistor.

[0017] In some examples, the regulating sub-circuit includes a regulating transistor, the first terminal of which is connected to a second power supply voltage terminal, the second terminal of which is connected to the control terminal of the follower transistor, and the control terminal is connected to the first control signal terminal; wherein the second power supply voltage terminal is used to provide a second power supply voltage; and the first control signal terminal is used to provide a first control signal.

[0018] In some examples, the photosensitive device is a photodiode, which is divided into a photosensitive part and a varactor part. The photosensitive part is connected to the control electrode of the follower transistor and is used to convert visible light into an electrical signal and transmit it to the follower transistor. The varactor part serves as the regulating sub-circuit and is connected to the control electrode of the follower transistor.

[0019] In some examples, it also includes: a reset transistor, whose control terminal is connected to a reset signal terminal, its first terminal is connected to an initialization signal terminal, and its second terminal is connected to the first terminal of the photosensitive device and the control terminal of the follower transistor; wherein the initialization signal terminal is used to provide the initialization signal; and the reset signal terminal is used to provide the reset control signal.

[0020] Secondly, embodiments of this disclosure also provide a flat panel detector, including a plurality of active pixel sensors.

[0021] In some examples, the active pixel sensor includes:

[0022] A substrate on which multiple active pixel sensor arrays are arranged;

[0023] An X-ray conversion layer is disposed on the side of the plurality of active pixel sensors facing away from the substrate.

[0024] In some examples, the flat panel detector further includes an active semiconductor layer disposed on the substrate, which includes the active layer of the follower transistor and the readout transistor;

[0025] A gate insulating layer is disposed on the side of the active semiconductor layer opposite to the substrate;

[0026] A first conductive layer is disposed on the side of the gate insulating layer opposite to the substrate; the first conductive layer includes the follower transistor and the control electrode of the read transistor;

[0027] A first insulating layer is disposed on the side of the first conductive layer that faces away from the substrate;

[0028] A source / drain metal layer is disposed on the side of the first insulating layer away from the substrate, and includes the follower transistor, the first electrode of the read transistor, and the second electrode of the read transistor;

[0029] A planarization layer is disposed on the side of the source / drain metal layer opposite to the substrate.

[0030] In some examples, the modulation sub-circuit of the active pixel sensor includes a first capacitor, a second capacitor, and a switching transistor;

[0031] The active semiconductor layer further includes the active layer of the switching transistor;

[0032] The first conductive layer further includes the control electrode of the switching transistor, the second electrode of the first capacitor, and the second electrode of the second capacitor;

[0033] The source and drain metal layers also include the first and second electrodes of the switching transistor, the first plate of the first capacitor, and the first plate of the second capacitor.

[0034] In some examples, the modulation sub-circuit of the active pixel sensor is a voltage-controlled liquid crystal capacitor, which includes a first electrode, a liquid crystal layer, and a second electrode sequentially disposed on the substrate in the direction pointing towards the planarization layer; wherein,

[0035] The first electrode is disposed in the same layer as the control electrode of the follower transistor and is made of the same material; the second electrode is disposed in the same layer as the first electrode of the follower transistor and is made of the same material.

[0036] In some examples, the modulation sub-circuit of the active pixel sensor includes a PIN diode, the PIN diode comprising a third electrode, an N-type semiconductor layer, an intrinsic layer, a P-type semiconductor layer, and a fourth electrode sequentially disposed on the substrate in the direction pointing towards the planarization layer; wherein,

[0037] The third electrode is disposed in the same layer as the control electrode of the follower transistor and is made of the same material; the fourth electrode is disposed in the same layer as the first electrode of the follower transistor and is made of the same material.

[0038] In some examples, the modulation sub-circuit of the active pixel sensor includes a PN diode, the PN diode comprising a fifth electrode, an N-type semiconductor layer, a P-type semiconductor layer, and a sixth electrode sequentially disposed on the substrate in the direction pointing towards the planarization layer; wherein,

[0039] The fifth electrode is disposed in the same layer as the control electrode of the follower transistor and is made of the same material; the sixth electrode is disposed in the same layer as the first electrode of the follower transistor and is made of the same material.

[0040] In some examples, the modulation sub-circuit of the active pixel sensor is an amorphous metal nonlinear resistor device, which includes a first amorphous metal electrode, a second insulating layer, and a second amorphous metal electrode sequentially disposed on the substrate in the direction pointing towards the planarization layer; wherein,

[0041] The first amorphous metal electrode plate is disposed in the same layer as the control electrode of the follower transistor and is made of the same material; the second amorphous metal electrode plate is disposed in the same layer as the first electrode of the follower transistor and is made of the same material.

[0042] In some examples, the modulation sub-circuit of the active pixel sensor includes modulation transistors;

[0043] The active semiconductor layer further includes the active layer of the regulating transistor; the first conductive layer further includes the control electrode of the regulating transistor; the source-drain metal layer further includes the first electrode and the second electrode of the regulating transistor.

[0044] In some examples, the photosensitive device is a photodiode, which includes a seventh electrode, a photosensitive layer, and an eighth electrode sequentially disposed on the planarization layer in a direction away from the substrate;

[0045] The seventh electrode is divided into a first sub-electrode and a second sub-electrode that do not contact each other. The part of the photodiode corresponding to the first sub-electrode is the photosensitive part, and the part of the photodiode corresponding to the second sub-electrode is the varactor part. The varactor part serves as the regulating sub-circuit.

[0046] The first sub-electrode is connected to the control electrode of the follower transistor through a via penetrating the planarization layer and the first insulating layer; the second sub-electrode is connected to the control electrode of the follower transistor through a via penetrating the planarization layer and the first insulating layer.

[0047] The active pixel sensor further includes: a light-shielding electrode disposed on the side of the eighth electrode away from the substrate, wherein the orthographic projection of the light-shielding electrode on the substrate covers the orthographic projection of the second sub-electrode on the substrate and does not overlap with the orthographic projection of the first sub-electrode on the substrate. Attached Figure Description

[0048] Figure 1 A schematic diagram of the structure of one embodiment of the flat panel detector provided in this disclosure;

[0049] Figure 2 A layer structure diagram of one embodiment of the flat panel detector provided in this disclosure;

[0050] Figure 3 A circuit diagram of one embodiment of an active pixel sensor provided in this disclosure (Embodiment 1);

[0051] Figure 4 The output voltage-electrical signal characteristic curve of the active pixel sensor provided in the embodiments of this disclosure;

[0052] Figure 5 A pixel structure diagram of one embodiment of an active pixel sensor provided in this disclosure;

[0053] Figure 6 A circuit structure diagram of one embodiment of the active pixel sensor provided in this disclosure (Embodiment 2);

[0054] Figure 7 A circuit structure diagram of one embodiment of the active pixel sensor provided in this disclosure (Embodiment 3);

[0055] Figure 8 A circuit structure diagram of one embodiment of the active pixel sensor provided in this disclosure (Embodiment 4);

[0056] Figure 9 This is a capacitance-voltage characteristic curve for Example 4;

[0057] Figure 10 A circuit structure diagram of one embodiment of the active pixel sensor provided in this disclosure (Embodiment 5);

[0058] Figure 11 This is a capacitance-voltage characteristic curve for Example 5;

[0059] Figure 12 A circuit diagram of one embodiment of an active pixel sensor provided in this disclosure (Embodiment Six);

[0060] Figure 13 This is the capacitance-voltage characteristic curve of Example 6;

[0061] Figure 14a Simulation timing diagram of an active pixel sensor provided for embodiments of this disclosure;

[0062] Figure 14b A table showing simulation results for an active pixel sensor provided in the embodiments of this disclosure;

[0063] Figure 15 A layer structure diagram of one embodiment of an active pixel sensor provided in this disclosure (Embodiment 1);

[0064] Figure 16 A layer structure diagram of one embodiment of the active pixel sensor provided in this disclosure (Embodiment 2);

[0065] Figure 17 A layer structure diagram of one embodiment of an active pixel sensor provided in this disclosure (one of three embodiments);

[0066] Figure 18 A layer structure diagram of one embodiment of an active pixel sensor provided in this disclosure (Embodiment 3 of 2);

[0067] Figure 19 A layer structure diagram of one embodiment of an active pixel sensor provided in this disclosure (Embodiment 4);

[0068] Figure 20 A layer structure diagram of one embodiment of an active pixel sensor provided in this disclosure (Embodiment 5);

[0069] Figure 21 A layer structure diagram of one embodiment of the active pixel sensor provided in this disclosure (Embodiment Six). Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0071] The shapes and sizes of the components in the accompanying drawings do not reflect actual proportions and are intended only to facilitate understanding of the embodiments of the present invention.

[0072] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an,” “a,” or “the,” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “including,” “comprising,” or “containing,” and similar terms mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. The terms “connected,” “linked,” or similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right,” etc., are used only to indicate relative positional relationships, and these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0073] This disclosure is not limited to the embodiments shown in the accompanying drawings, but includes modifications to the configuration based on the manufacturing process. Therefore, the areas illustrated in the drawings are schematic, and the shapes of the areas shown illustrate specific shapes of the areas of an element, but are not intended to be limiting.

[0074] The transistors used in the embodiments of this invention can be thin-film transistors, field-effect transistors, or other devices with the same characteristics. Since the source and drain of the transistors are symmetrical, there is no distinction between them. In the embodiments of this invention, to distinguish the source and drain of the transistor, one of the source and drain is called the first terminal, the other is called the second terminal, and the gate is called the control terminal. Furthermore, according to their characteristics, transistors can be divided into N-type and P-type. When a P-type transistor is used, the first terminal is the source, the second terminal is the drain, and the source and drain are turned on when the gate input is low. When an N-type transistor is used, the first terminal is the source, the second terminal is the drain, and the source and drain are turned on when the gate input is high. The transistors described below are all based on N-type transistors. It is conceivable that using P-type transistors is something that those skilled in the art can conceive of without creative effort, and therefore is also within the scope of protection of the embodiments of this invention.

[0075] This disclosure provides an active pixel sensor that can be used in a flat panel detector. Taking an exemplary flat panel detector as an example... Figure 1 As shown, the flat panel detector may include multiple active pixel sensors PX arranged in an array, each active pixel sensor PX including at least one photosensitive element. Figure 1 (Not shown) and a readout circuit connected to the photosensitive device, the readout circuit having at least one thin-film transistor (TFT). The photosensitive device senses visible light and converts it into an electrical signal. The readout circuit reads the electrical signal from the photosensitive device, amplifies the electrical signal, and converts it into an output voltage for transmission to subsequent devices (e.g., a computer). The flat panel detector also includes multiple scan lines GATE extending along the row direction of the arrayed active pixel sensors PX, and multiple readout lines DATA extending along the column direction of the arrayed active pixel sensors PX. Active pixel sensors PX located in the same row are connected to the same scan line GATE, and active pixel sensors PX located in the same column are connected to the same readout line DATA. The area where the scan line GATE and the readout line DATA intersect defines an active pixel sensor PX. Based on this, as Figure 1As shown, the flat panel detector also includes a Field-Programmable Gate Array (FPGA) chip. Scan lines (GATE) are connected to the FPGA chip via a Chip-On-Flex (COF) thin film. The COF includes a Gate Driver IC (G-IC), which sequentially provides scan signals to multiple scan lines (GATE), activating the thin-film transistors in the readout circuit line by line. Readout lines (DATA) are connected to the FPGA chip via a Readout IC (ROIC). The output voltage read by the readout circuit is transmitted to readout lines (DATA), which then transmit the output voltage to the FPGA chip via the output interface on the ROIC.

[0076] It is understood here that in this embodiment, the scan line DATA is connected to the FPGA chip through COF, which can significantly reduce the generation of noise in signal transmission. In addition, the FPGA chip can be connected to other devices through a printed circuit board (PCB). The specific connection structure (e.g., PCB) can be of various types and is not limited here.

[0077] Further, see Figure 2 , Figure 2This is an exemplary layer structure diagram of a flat panel detector. If the active pixel sensor provided in this embodiment is applied in the flat panel detector, the flat panel detector includes a substrate 01 and a light conversion layer 11 disposed on the substrate 01. The light conversion layer 11 includes a plurality of active pixel sensors PX arranged in an array on the substrate 01. Each active pixel sensor PX includes a readout circuit and a photosensitive device. Therefore, the readout circuits of the plurality of active pixel sensors PX form a thin film transistor array 111 disposed on the substrate 01, and the photosensitive devices of the plurality of active pixel sensors PX form a photosensitive device array 112 disposed on the side of the thin film transistor array 111 facing away from the substrate 01. In addition, the flat panel detector also includes an X-ray conversion layer 12 disposed on the side of the light conversion layer 11 facing away from the substrate 01. The X-ray conversion layer 12 can be composed of a scintillator, which is a type of material that can emit light after absorbing high-energy particles or rays. It is usually processed into crystals in applications and is called a scintillation crystal. In this embodiment, the specific material of the scintillation crystal in the X-ray conversion layer 12 is not limited. For example, it can be cesium iodide, cadmium tungstate, barium fluoride, gadolinium oxysulfate (GOS), etc. When the scintillation crystal in the X-ray conversion layer 12 is struck by high-energy particles of X-rays that have attenuated after passing through the human body, the kinetic energy of the high-energy particles is converted into light energy and flashes, that is, X-rays are converted into visible light. The visible light shines on the light conversion layer 11, and the photosensitive devices in each active pixel sensor PX in the light conversion layer 11 can convert the visible light into an electrical signal. The electrical signal is amplified into an output voltage by the readout circuit and read out. It is then transmitted to the computer for image processing to form an X-ray image.

[0078] Understandably, as the pixels detected by the flat panel detector become smaller, meaning the flat panel detector has more active pixel sensors, resulting in higher image clarity, the visible light sensed by the photosensitive device in each active pixel sensor also decreases accordingly, thus reducing the electrical signal. Alternatively, in some detection methods, due to a reduction in the input X-ray dose, the light signal sensed by the photosensitive device in each active pixel sensor also decreases accordingly, causing a significant reduction in the signal read out by the readout circuit in each active pixel sensor, leading to a deterioration in the signal-to-noise ratio. Therefore, active pixel sensors can amplify the electrical signal converted from light by the photosensitive device, amplifying the electrical signal into an output voltage. However, the magnification (i.e., amplification sensitivity) of active pixel sensors is usually fixed. As the intensity of visible light increases, the electrical signal converted by the photosensitive device also increases. However, the magnitude of the electrical signal converted by the photosensitive device has a certain range. Therefore, if the amplification sensitivity of the active pixel sensor is too high, the electrical signal will quickly saturate, that is, the electrical signal will reach the upper limit of the photosensitive device. Therefore, further increasing the light intensity will not be detected by the photosensitive device, and thus will not improve the image quality, making it difficult to adapt to detection with a large range of light intensity changes. If the amplification sensitivity of the active pixel sensor is too low, it may not be able to detect signal changes for detection with small light intensity changes. To solve the above problems, the inventors have provided an active pixel sensor.

[0079] Firstly, see [the following] Figure 3This embodiment provides an active pixel sensor, which may include a photosensitive element Sg and a readout circuit. Specifically, the readout circuit may include a follower transistor T1, an adjustment sub-circuit 1, and a readout transistor T2. After the photosensitive element Sg senses visible light, it converts the visible light into an electrical signal and inputs it to the follower transistor T1. The control electrode of the follower transistor T1 is connected to the first electrode of the photosensitive element Sg, and the first electrode of the follower transistor T1 is connected to a first power supply voltage terminal, which provides a first power supply voltage VDD. The second electrode of the follower transistor T1 is connected to the first electrode of the readout transistor T2. The follower transistor T1 receives the electrical signal from the photosensitive element Sg and amplifies the signal into an output voltage. The adjustment sub-circuit 1 is configured to adjust the amplification sensitivity of the follower transistor T1 in response to a first control signal CON1, that is, to adjust the amplification factor of the electrical signal by the follower transistor T1. For example, the adjustment sub-circuit 1 can change the voltage difference between the control electrode and the first electrode of the follower transistor T1. The follower transistor T1 amplifies the electrical signal generated by the photosensitive device Sg sensing light. The control electrode of the readout transistor T2 is connected to the scan line GATE, the first electrode of the readout transistor T2 is connected to the second electrode of the follower transistor T1, and the second electrode of the readout transistor T2 is connected to the readout line DATA. The scan line GATE is used to provide the scan signal SCAN. The readout transistor T2 is configured to read the output voltage of the follower transistor T1 in response to the scan signal SCAN. As the intensity of visible light increases or decreases, the electrical signal converted by the photosensitive device Sg according to the visible light also increases or decreases. Consequently, the output voltage of the follower transistor T1 converted according to the electrical signal also increases or decreases. Thus, the readout sub-circuit 1 reads out the output voltage and transmits it to subsequent equipment (such as a computer) for image processing to form an X-ray image.

[0080] The active pixel sensor provided in this embodiment of the present disclosure, due to the inclusion of an adjustment sub-circuit 1, can adjust the amplification sensitivity of the follower transistor T1 as needed. Therefore, by adjusting the amplification sensitivity of the follower transistor T1, the active pixel sensor can adapt to various types of detection. For example, see [link to relevant documentation]. Figure 4 If the electrical signal converted from visible light by the photosensitive device Sg is small and the range of variation of the electrical signal is small, then the regulating sub-circuit 1 can adjust the amplification sensitivity of the follower transistor T1, so that the follower transistor T1 has a higher amplification sensitivity, thereby achieving the desired effect. Figure 4As shown in curve ①, as the electrical signal of the photosensitive device Sg increases, the output voltage of the follower transistor T1, converted according to the electrical signal, also increases rapidly. This allows the active pixel sensor to detect even small changes in visible light, thus making the active pixel sensor more sensitive. If the range of change in the electrical signal converted by the photosensitive device Sg according to visible light is large, the regulating sub-circuit 1 can adjust the amplification sensitivity of the follower transistor T1, giving it a lower amplification sensitivity, thus... Figure 4 As shown in curve ②, as the electrical signal of the photosensitive device Sg increases, the output voltage of the follower transistor T1, converted according to the electrical signal, also increases. However, its rate of increase is smaller than that in curve ①, thus avoiding rapid saturation of the electrical signal (i.e., reaching the upper limit of the detection range), thereby enabling the active pixel sensor to have a larger detection range. In summary, by adjusting the amplification sensitivity of the follower transistor T1 through sub-circuit 1, the active pixel sensor can be configured with different sensitivity modes, thus adapting to detection in various scenarios.

[0081] Furthermore, the specific circuit structure of the readout circuit of the active pixel sensor provided in this disclosure embodiment can include various types, for example, see... Figure 3 The readout circuit of the active pixel sensor may include a follower transistor T1, a modulation sub-circuit 1, and a readout transistor T2. The control electrode of the follower transistor T1 is connected to the first electrode of the photosensitive device Sg; the first electrode of the follower transistor T1 is connected to a first power supply voltage terminal, and a second voltage terminal is used to provide the first power supply voltage VDD; the second electrode of the follower transistor T1 is connected to the readout transistor T2. The photosensitive device Sg senses visible light and converts it into charge according to the intensity of the visible light, generating an electrical signal. This electrical signal is output to the control electrode of the follower transistor T1, thereby determining the magnitude of the current flowing through the follower transistor T1. Therefore, by measuring the magnitude of the current flowing through the follower transistor T1, the intensity of the visible light sensed by the photosensitive device Sg can be obtained. The modulation sub-circuit 1 is connected to the control electrode of the follower transistor T1. The modulation sub-circuit 1 can adjust the amplification sensitivity of the follower transistor T1 to the electrical signal. Specifically, the amplification sensitivity of the follower transistor T1 can be adjusted by adjusting the potential between the control electrode and the first electrode of the follower transistor T1. The control electrode of read transistor T2 is connected to the scan line GATE, which provides the scan signal SCAN. The first electrode of read transistor T2 is connected to the follower transistor T1, and the second electrode of read transistor T2 is connected to the read line DATA. (See also...) Figure 1The scan signal provided by the G-IC in COF is loaded line by line to each scan line GATE according to the timing provided by the G-IC. A scan line GATE is connected to the control electrode of the read transistor T2 in a row of active pixel sensors, so that the read transistor T2 in multiple rows of active pixel sensors is turned on line by line. The output voltage of the follow transistor T1 is read by the read transistor T2 and transmitted to the FPGA through the read line DATA connected to the second electrode of the read transistor T2.

[0082] In some examples, the active pixel sensor provided in this disclosure may further include a reset transistor T3. The reset transistor T3 is configured to transmit an initialization signal VINIT to the first terminal of the photosensitive device Sg and the follower transistor T1 in response to a reset control signal RST. That is, in response to the reset control signal RST, the initialization signal VINIT is loaded onto the first terminal of the photosensitive device Sg and the follower transistor T1 to reset the photosensitive device Sg and the follower transistor T1. Specifically, the control terminal of the reset transistor T3 may be connected to a reset signal terminal, which provides the reset control signal RST; the first terminal of the reset transistor T3 is connected to an initialization signal terminal, which provides the initialization signal VINIT; and the second terminal of the reset transistor T3 is connected to the first terminal of the photosensitive device Sg and the control terminal of the follower transistor T1. When the reset control signal RST is loaded onto the control terminal of the reset transistor T3, the reset transistor T3 turns on, loading the initialization signal VINIT from its first terminal onto the first terminal of the photosensitive device Sg and the control terminal of the follower transistor T1. Of course, a circuit structure including two reset transistors may also be used for reset, and this is not limited thereto.

[0083] See Figure 1 , Figure 5 Taking the readout circuit of each active pixel sensor, including follower transistor T1, readout transistor T2, and reset transistor T3, as an example, Figure 1 As shown, multiple active pixel sensor PX arrays are arranged on substrate 01, with multiple scan lines (GATE) extending along the row direction and multiple read lines (DATA) extending along the column direction. Figure 5 As shown, Figure 5The diagram illustrates the pixel structure of a single active pixel sensor PX (without showing the photosensitive element Sg). Multiple reset signal lines L1 extend along the row direction and are connected to the control electrode of a reset transistor T3. These lines are also connected to a reset signal terminal to transmit the reset control signal RST. Multiple first power supply voltage lines L2 extend along the row direction and are connected to the first electrode of a follower transistor T1. These lines are also connected to a first power supply voltage terminal to transmit the first power supply voltage VDD. Multiple initialization signal lines L3 extend along the column direction and are connected to the first electrode of a reset transistor T3. These lines are also connected to an initialization signal terminal to transmit the initialization signal VINIT. The adjustment sub-circuit 1 can include various types of circuit structures and can be located in multiple positions. Figure 5 The following example illustrates the layout of the regulating sub-circuit between the read line DATA and the initialization signal line L3, and between the follower transistor T1 and the reset signal line L1.

[0084] It should be noted that in the embodiments of this disclosure, one of the second power supply voltage VSS and the first power supply voltage VDD is high voltage and the other is low voltage. In the following description, the second power supply voltage VSS is always kept at low voltage and the first power supply voltage VDD is always kept at high voltage as an example, and no limitation is made here.

[0085] To clarify the specific implementation of the active pixel sensor in this embodiment, the operation of the pixel driving circuit described above will be explained. The following explanation uses an active pixel sensor readout circuit including a follower transistor T1, a readout transistor T2, and a reset transistor T3 as an example. The operation of an active pixel sensor typically includes three stages: stage T1 (also called the reset stage), stage T2 (also called the exposure stage), and stage T3 (also called the readout stage). It should be noted that the second terminal of the photosensitive element Sg is connected to the second power supply voltage terminal and receives the second power supply voltage VSS. Throughout all three stages, the second terminal of the photosensitive element Sg consistently receives the second power supply voltage VSS.

[0086] In stage T1, a pulse is applied to the control electrode of reset transistor T3 using the reset control signal RST to turn on reset transistor T3, and the initialization signal VINIT on the first electrode of reset transistor T3 is loaded to the control electrode of follower transistor T1 and the first electrode of photosensitive device Sg for reset.

[0087] In stage T2, visible light shines on the photosensitive device Sg, and photons striking Sg generate electron-hole pairs. The resulting charge migrates to the first electrode of the photosensitive device Sg, while holes are attracted to the second electrode, and electrons are attracted to the first electrode. The charge accumulated at the first electrode of the photosensitive device Sg forms an electrical signal. The first electrode of the photosensitive device Sg is connected to the regulating circuit 1 and also to the control electrode of the follower transistor T1. Specifically, the magnitude of the electrical signal output by the photosensitive device Sg determines the magnitude of the current flowing through the follower transistor T1 (i.e., the magnitude of the output voltage). The regulating circuit 1 responds to the first control signal CON1 and adjusts the amplification sensitivity of the follower transistor T1 accordingly. Specifically, the regulating circuit 1 can adjust its own capacitance according to the first control signal. The capacitance of the regulating circuit 1 is inversely proportional to the amplification sensitivity of the follower transistor T1; the larger the capacitance, the lower the amplification sensitivity of the follower transistor T1, and the smaller the capacitance, the higher the amplification sensitivity of the follower transistor T1. In stage T2, the photosensitive device Sg senses visible light and converts it into an electrical signal. The follower transistor T1 amplifies the electrical signal proportionally to the output voltage according to the adjustment of the regulator circuit 1, and accumulates it at the second terminal of the follower transistor T1.

[0088] It should be noted that the step of regulating the sub-circuit 1 in response to the first control signal CON1 to adjust its own capacitance can be completed before stage T2 or during stage T2, and no limitation is made here.

[0089] In stage T3, a pulse is applied to the control terminal of read transistor T2 by scanning signal SCAN to turn on read transistor T2. The first terminal of read transistor T2 is connected to the second terminal of follower transistor T1. Therefore, after read transistor T2 is turned on, the output voltage of the second terminal of follower transistor T1 is read out to read line DATA.

[0090] In the active pixel sensor provided in this embodiment, the adjustment sub-circuit 1 can adjust the amplification sensitivity of the follower transistor T1. The circuit structure of the adjustment sub-circuit 1 can include various types. For example, the adjustment sub-circuit 1 can adjust the potential between the control electrode and the first electrode of the follower transistor T1 by adjusting its own capacitance, thereby adjusting the amplification sensitivity of the follower transistor T1. The larger the capacitance of the adjustment sub-circuit 1, the lower the amplification sensitivity of the follower transistor T1; correspondingly, the smaller the capacitance of the adjustment sub-circuit 1, the higher the amplification sensitivity of the follower transistor T1. The specific structure of the adjustment sub-circuit 1 is illustrated below. It should be noted that the following description uses the example of the follower transistor T1 including the follower transistor T1, the readout transistor T2 including the readout transistor T2, and the reset transistor T3 including the reset transistor T3 in the active pixel sensor, but this does not constitute a limitation on the present invention.

[0091] Example 1

[0092] See Figure 3 The active pixel sensor includes a follower transistor T1, a modulation sub-circuit 1, a readout transistor T2, and a reset transistor T3. The first terminal of the follower transistor T1 is connected to the first power supply voltage terminal to receive the first power supply voltage VDD. The control terminal of the follower transistor T1 is connected to the first terminal of the photosensitive element Sg. The second terminal of the follower transistor T1 is connected to the first terminal of the readout transistor T2. The control terminal of the readout transistor T2 is connected to the scan line GATE and receives the scan signal SCAN. The first terminal of the readout transistor T2 is connected to the second terminal of the follower transistor T1, and the second terminal of the readout transistor T2 is connected to the readout line DATA. The control terminal of the reset transistor T3 is connected to the reset signal terminal to receive the reset control signal RST. The first terminal of the reset transistor T3 is connected to the initialization signal terminal to receive the initialization signal VINIT. The second terminal of the reset transistor T3 is connected to the first terminal of the photosensitive element Sg and the control terminal of the follower transistor T1, used to reset the first terminal of the photosensitive element Sg and the control terminal of the follower transistor T1.

[0093] The regulating sub-circuit 1 may include a first capacitor C1, a second capacitor C2, and a switching transistor Tk. The first terminal of the first capacitor C1 is connected to the first terminal of the switching transistor Tk; the first terminal of the second capacitor C2 is connected to the second terminal of the switching transistor Tk; the control terminal of the switching transistor Tk is connected to a first control signal terminal, which provides a first control signal CON1; the second terminals of both the first capacitor C1 and the second capacitor C2 are connected to a follower transistor T1, meaning the switching transistor Tk and the second capacitor C2 are connected in series, and the branch formed by the switching transistor Tk and the second capacitor C2 is connected in parallel with the first capacitor C1. Furthermore, the first terminal of the switching transistor Tk is connected to a second power supply voltage terminal to receive the second power supply voltage VSS; the second terminals of both the first capacitor C1 and the second capacitor C2 are connected to the first terminal of the photosensitive device Sg, and also to the follower transistor T1, specifically to the control terminal of the follower transistor T1. The second power supply voltage VSS connected to the first terminal of the switching transistor Tk is always kept at a low level. The voltage output by the first control signal CON1 can change the conduction state of the switching transistor Tk, thereby changing the capacitance of the regulating sub-circuit 1. For example, if the follower transistor T1 needs to have a higher amplification sensitivity, the switching transistor Tk is turned off by the first control signal CON1, then the second capacitor C2 remains open, and the capacitance of the adjusting sub-circuit 1 is the same as that of the first capacitor C1; if the follower transistor T1 needs to have a lower amplification sensitivity, the switching transistor Tk is turned on by the first control signal CON1, then the second capacitor C2 is connected in the circuit, and the capacitance of the adjusting sub-circuit 1 is the sum of the capacitances of the first capacitor C1 and the second capacitor C2.

[0094] Example 2

[0095] See Figure 6 The active pixel sensor includes a follower transistor T1, a modulation sub-circuit 1, a readout transistor T2, and a reset transistor T3. The first terminal of the follower transistor T1 is connected to the first power supply voltage terminal to receive the first power supply voltage VDD. The control terminal of the follower transistor T1 is connected to the first terminal of the photosensitive element Sg. The second terminal of the follower transistor T1 is connected to the first terminal of the readout transistor T2. The control terminal of the readout transistor T2 is connected to the scan line GATE and receives the scan signal SCAN. The first terminal of the readout transistor T2 is connected to the second terminal of the follower transistor T1, and the second terminal of the readout transistor T2 is connected to the readout line DATA. The control terminal of the reset transistor T3 is connected to the reset signal terminal to receive the reset control signal RST. The first terminal of the reset transistor T3 is connected to the initialization signal terminal to receive the initialization signal VINIT. The second terminal of the reset transistor T3 is connected to the first terminal of the photosensitive element Sg and the control terminal of the follower transistor T1, used to reset the first terminal of the photosensitive element Sg and the control terminal of the follower transistor T1.

[0096] The regulating sub-circuit 1 can be a voltage-controlled liquid crystal capacitor (VCC). The VCC includes a first electrode, a second electrode, and a liquid crystal layer located between them. By controlling the electric field between the first and second electrodes, the deflection angle of the liquid crystal molecules in the liquid crystal layer can be adjusted, thereby changing the voltage of the VCC and consequently altering the amplification sensitivity of the follower transistor T1. The second electrode of the VCC is connected to the second power supply voltage terminal to receive the second power supply voltage VSS (i.e., the reference voltage), and the first electrode is connected to the first control signal terminal, where the first control signal CON1 is the bias voltage.

[0097] Example 3

[0098] See Figure 7 The active pixel sensor includes a follower transistor T1, a modulation sub-circuit 1, a readout transistor T2, and a reset transistor T3. The first terminal of the follower transistor T1 is connected to the first power supply voltage terminal to receive the first power supply voltage VDD. The control terminal of the follower transistor T1 is connected to the first terminal of the photosensitive element Sg. The second terminal of the follower transistor T1 is connected to the first terminal of the readout transistor T2. The control terminal of the readout transistor T2 is connected to the scan line GATE and receives the scan signal SCAN. The first terminal of the readout transistor T2 is connected to the second terminal of the follower transistor T1, and the second terminal of the readout transistor T2 is connected to the readout line DATA. The control terminal of the reset transistor T3 is connected to the reset signal terminal to receive the reset control signal RST. The first terminal of the reset transistor T3 is connected to the initialization signal terminal to receive the initialization signal VINIT. The second terminal of the reset transistor T3 is connected to the first terminal of the photosensitive element Sg and the control terminal of the follower transistor T1, used to reset the first terminal of the photosensitive element Sg and the control terminal of the follower transistor T1.

[0099] The regulating circuit 1 includes a varactor diode, which is a semiconductor device whose electrical characteristics are voltage-dependent capacitance. The capacitance of the varactor diode is determined by the voltage between its first and second terminals (i.e., the barrier voltage). Therefore, changing the voltage between the first and second terminals of the varactor diode can change the capacitance of the varactor diode, thereby changing the amplification sensitivity of the follower transistor T1.

[0100] In some examples, varactor diodes include various types, such as NMOS transistors, PMOS transistors, PIN diodes, PN diodes, etc., which are not limited here.

[0101] Example 4

[0102] See Figure 8The active pixel sensor includes a follower transistor T1, a modulation sub-circuit 1, a readout transistor T2, and a reset transistor T3. The first terminal of the follower transistor T1 is connected to the first power supply voltage terminal to receive the first power supply voltage VDD. The control terminal of the follower transistor T1 is connected to the first terminal of the photosensitive element Sg. The second terminal of the follower transistor T1 is connected to the first terminal of the readout transistor T2. The control terminal of the readout transistor T2 is connected to the scan line GATE and receives the scan signal SCAN. The first terminal of the readout transistor T2 is connected to the second terminal of the follower transistor T1, and the second terminal of the readout transistor T2 is connected to the readout line DATA. The control terminal of the reset transistor T3 is connected to the reset signal terminal to receive the reset control signal RST. The first terminal of the reset transistor T3 is connected to the initialization signal terminal to receive the initialization signal VINIT. The second terminal of the reset transistor T3 is connected to the first terminal of the photosensitive element Sg and the control terminal of the follower transistor T1, used to reset the first terminal of the photosensitive element Sg and the control terminal of the follower transistor T1.

[0103] The regulating sub-circuit 1 can be an amorphous metal nonlinear resistor (AMNR). Specifically, the AMNR resistor mainly consists of a three-layer structure: a first amorphous metal plate, a second insulating layer, and a second amorphous metal plate. Because both the upper and lower plates are amorphous metal plates, the surface roughness is low, and it can be made ultra-thin, resulting in a small overall structure that is easy to integrate. (See also...) Figure 9 , Figure 9 The capacitance-voltage characteristic curve of the AMNR device shows that by controlling the voltage between the first and second amorphous metal plates, the capacitance of the AMNR resistor device can be changed, thereby changing the amplification sensitivity of the follower transistor T1.

[0104] Example 5

[0105] See Figure 10The active pixel sensor includes a follower transistor T1, a modulation sub-circuit 1, a readout transistor T2, and a reset transistor T3. The first terminal of the follower transistor T1 is connected to the first power supply voltage terminal to receive the first power supply voltage VDD. The control terminal of the follower transistor T1 is connected to the first terminal of the photosensitive element Sg. The second terminal of the follower transistor T1 is connected to the first terminal of the readout transistor T2. The control terminal of the readout transistor T2 is connected to the scan line GATE and receives the scan signal SCAN. The first terminal of the readout transistor T2 is connected to the second terminal of the follower transistor T1, and the second terminal of the readout transistor T2 is connected to the readout line DATA. The control terminal of the reset transistor T3 is connected to the reset signal terminal to receive the reset control signal RST. The first terminal of the reset transistor T3 is connected to the initialization signal terminal to receive the initialization signal VINIT. The second terminal of the reset transistor T3 is connected to the first terminal of the photosensitive element Sg and the control terminal of the follower transistor T1, used to reset the first terminal of the photosensitive element Sg and the control terminal of the follower transistor T1.

[0106] The regulating sub-circuit 1 may include a regulating transistor T4. The first terminal of the regulating transistor T4 is connected to the second power supply voltage terminal, receiving the second power supply voltage VSS. The second terminal of the regulating transistor T4 is connected to a follower transistor T1, specifically, it can be connected to the control terminal of the follower transistor T1. The control terminal of the regulating transistor T4 is connected to the first control signal terminal, receiving the first control signal CON1. ​​The second power supply voltage VSS received by the first terminal of the regulating transistor T4 is always valid. By adjusting the voltage input through the first control signal CON1, the regulating transistor T4 can operate in different operating states (e.g., cutoff state, saturation state, amplification state). The regulating transistor T4 in different operating states has different capacitances, thereby changing the amplification sensitivity of the follower transistor T1.

[0107] See Figure 11 , Figure 11 To adjust the capacitance-voltage characteristic curve of transistor T4, it can be seen that by controlling the voltage of the first control signal CON1, the value of Vgs of transistor T4 can be changed, thereby changing the capacitance of transistor T4, and thus changing the amplification sensitivity of follower transistor T1.

[0108] Example 6

[0109] See Figure 12 The photosensitive device Sg can be a photodiode, which is divided into a photosensitive part Sga and a varactor part Sgb. The photosensitive part Sga is connected to the readout circuit as the original photosensitive device, while the varactor part Sgb is connected to the readout circuit as part of the circuit structure of the adjustment sub-circuit 1.

[0110] The active pixel sensor includes a follower transistor T1, a modulation sub-circuit 1, a readout transistor T2, and a reset transistor T3. The first terminal of the follower transistor T1 is connected to the first power supply voltage terminal to receive the first power supply voltage VDD. The control terminal of the follower transistor T1 is connected to the first terminal of the photosensitive portion Sga of the photosensitive element Sg. The second terminal of the follower transistor T1 is connected to the first terminal of the readout transistor T2. The control terminal of the readout transistor T2 is connected to the scan line GATE and receives the scan signal SCAN. The first terminal of the readout transistor T2 is connected to the second terminal of the follower transistor T1, and the second terminal of the readout transistor T2 is connected to the readout line DATA. The control terminal of the reset transistor T3 is connected to the reset signal terminal to receive the reset control signal RST. The first terminal of the reset transistor T3 is connected to the initialization signal terminal to receive the initialization signal VINIT. The second terminal of the reset transistor T3 is connected to the first terminal of the photosensitive portion Sga and the control terminal of the follower transistor T1, used to reset the first terminal of the photosensitive portion Sga and the control terminal of the follower transistor T1.

[0111] The regulating circuit 1 is the varactor portion Sgb of the photosensitive device Sg. The photosensitive device Sg is a photodiode, which usually includes a PN diode or a PIN diode. The capacitance of the photodiode is determined by the voltage between its first and second terminals. Therefore, changing the voltage between the first and second terminals of the varactor portion Sgb of the photodiode can change the capacitance of the varactor portion Sgb, thereby changing the amplification sensitivity of the follower transistor T1.

[0112] See Figure 13 , Figure 13 The capacitance-voltage characteristic curve of the varactor Sgb of the photodiode shows that by changing the voltage between the first and second terminals of the varactor Sgb, the capacitance of the varactor Sgb can be changed, thereby changing the amplification sensitivity of the follower transistor T1.

[0113] It should be noted that the specific structure of the regulating sub-circuit 1 in the above embodiments can also include many other ways. The above are only exemplary structures given for the purpose of illustration and do not constitute a limitation on this application.

[0114] The inventors performed a simulation using the active pixel sensor provided in this embodiment. See the simulation timing diagram below. Figure 14a Wherein, the Reset signal is the reset control signal RST, the Integration signal is the acquisition signal, and readout1 and readout512 are the scan signals SCAN of the first and 512th row active pixel sensors, respectively. Figure 14a The simulation results for timing simulation can be found in [reference]. Figure 14bIt should be noted that in an active pixel sensor, the photosensitive element Sg generates a carrier forming voltage (i.e., photogenerated voltage) after sensing visible light. The magnitude of this photogenerated voltage is directly proportional to the intensity of the visible light radiation it receives, and the corresponding current is... Figure 14b The photocurrent in the sensor; however, even when the photosensitive element Sg of the active pixel sensor does not sense light, a voltage is generated, and the current corresponding to this voltage is... Figure 14b Dark current in. It should be noted that... Figure 14b In the figure, Cst represents the capacitance of the regulating sub-circuit 1, MSM represents the non-adjustable capacitance of the metal-semiconductor-metal (MSM), and the values ​​of MSM dark current and MSM photocurrent are simulation results of an exemplary active pixel sensor in which the regulating sub-circuit 1 is not applied and the MSM capacitance is used as the storage capacitor.

[0115] Secondly, combining Figure 2 , Figure 15 This disclosure also provides a flat panel detector, which includes a substrate 01, a light conversion layer 11 disposed on the substrate 01, and the light conversion layer 11 including a plurality of active pixel sensors PX arranged in an array on the substrate 01. Figure 15 This is an exemplary layer structure diagram of an active pixel sensor PX. Each active pixel sensor PX includes a readout circuit and a photosensitive device Sg. Therefore, the readout circuits of multiple active pixel sensors PX form a thin-film transistor array 111 disposed on a substrate 01, and the photosensitive devices Sg of multiple active pixel sensors PX form a photosensitive device array 112 disposed on the side of the thin-film transistor array 111 facing away from the substrate 01. Furthermore, the flat panel detector also includes an X-ray conversion layer 12 disposed on the side of the light conversion layer 11 facing away from the substrate 01, that is, the X-ray conversion layer 12 is disposed on the side of multiple active pixel sensors PX facing away from the substrate 01. The X-ray conversion layer 12 can be, for example, composed of a scintillator. A scintillator is a material that can emit light after absorbing high-energy particles or rays. It is usually processed into crystals in applications and called a scintillator crystal. In this embodiment, the specific material of the scintillator crystal in the X-ray conversion layer 12 is not limited; for example, it can be cesium iodide, cadmium tungstate, barium fluoride, gadolinium oxysulfate (GOS), etc. The scintillation crystal in the X-ray conversion layer 12, when struck by high-energy particles of X-rays that have attenuated after passing through the human body, converts the kinetic energy of the high-energy particles into light energy, emitting a flash of light, that is, converting X-rays into visible light. The visible light shines on the light conversion layer 11, and the photosensitive device Sg in each active pixel sensor PX in the light conversion layer 11 can convert the visible light into an electrical signal. The electrical signal is amplified into an output voltage by the readout circuit and read out, and then transmitted to the computer for image processing to form an X-ray image.

[0116] Furthermore, the readout circuit of the active pixel sensor in the light conversion layer 11 may include at least one thin-film transistor. Specifically, the film layer of the readout circuit of the active pixel sensor may include an active semiconductor layer, a gate insulating layer, a first conductive layer, a first insulating layer, a source-drain metal layer, and a planarization layer sequentially disposed on the substrate 01 in the direction pointing towards the photosensitive device Sg. The active semiconductor layer may include the active layer of each thin-film transistor in the readout circuit, the first conductive layer may include the control electrode (i.e., the gate) of each thin-film transistor in the readout circuit, and the source-drain metal layer may include the first electrode and the second electrode (i.e., the source and drain) of each thin-film transistor in the readout circuit.

[0117] Specifically, taking the readout circuit of an active pixel sensor as an example, which includes a follower transistor T1 and a readout transistor T2; the active pixel sensor may also include a reset transistor T3. It should be noted that the control electrode of the thin-film transistor described below is the gate, the first electrode is the source, and the second electrode is the drain. The flat panel detector may include a substrate 01 and a buffer layer 02 disposed on the substrate 01. The flat panel detector may also include an active semiconductor layer disposed on the side of the buffer layer 02 away from the substrate 01. The active semiconductor layer may include the active layer A1 of the follower transistor T1, the active layer A2 of the readout transistor T2, and the active layer A3 of the reset transistor T3. The active semiconductor layer may include oxide semiconductors, organic semiconductors, amorphous silicon, or polycrystalline silicon, etc. For example, oxide semiconductors include metal oxide semiconductors (e.g., indium gallium zinc oxide (IGZO)), and polycrystalline silicon includes low-temperature polycrystalline silicon or high-temperature polycrystalline silicon, etc. Furthermore, the active layer of each thin-film transistor may include a channel region (…). Figure 15 The pattern of diagonal lines filling the active layer and the source / drain doped regions ( Figure 15 (A pattern filled with dots in the active layer).

[0118] Furthermore, the flat panel detector may also include a gate insulating layer 03, which is disposed on the side of the active semiconductor layer opposite to the substrate 01. The material of the gate insulating layer 03 may include inorganic insulating materials such as silicon nitride, nitrogen oxide, and silicon oxynitride, or organic insulating materials such as organic resin, or other suitable materials, and is not limited herein.

[0119] Furthermore, the flat panel detector may also include a first conductive layer disposed on the side of the gate insulating layer 03 away from the substrate 01. The first conductive layer may include the control electrode G1 of the follower transistor T1, the control electrode G2 of the read transistor T2, and the control electrode G3 of the reset transistor T3.

[0120] Furthermore, the flat panel detector may also include a first insulating layer 04, which is disposed on the side of the first conductive layer opposite to the substrate 01.

[0121] Furthermore, the flat panel detector may also include a source-drain metal layer disposed on the side of the first insulating layer 04 away from the substrate 01. The source-drain metal layer includes a first electrode S1 and a second electrode D1 of the follow transistor T1, a first electrode S2 and a second electrode D2 of the read transistor T2, and a first electrode S3 and a second electrode D3 of the reset transistor T3.

[0122] Furthermore, the flat panel detector may also include a planarization layer 05 disposed on the side of the source / drain metal layer away from the substrate 01.

[0123] Furthermore, a photosensitive device Sg can be disposed on the side of the planarization layer 05 facing away from the substrate 01. The photosensitive device Sg may include a seventh electrode Sg1, a photosensitive layer Sg2, and an eighth electrode Sg3 sequentially disposed on the side of the planarization layer 05 facing away from the substrate 01, wherein one of the seventh electrode Sg1 and the eighth electrode Sg3 is a cathode and the other is an anode. The seventh electrode Sg1 is connected to the control electrode G1 of the follower transistor T1 and the second electrode D3 of the reset transistor T3 through a via in the planarization layer 05 (only the portion connected to the second electrode D3 of the reset transistor T3 is shown exemplary in the figure). The photosensitive layer Sg2 contains at least a photosensitive material. If it is used to detect ultraviolet light, an ultraviolet light-sensitive material is selected. In specific implementations, appropriate materials can be selected according to actual needs.

[0124] Furthermore, the flat panel detector may also include a protective layer 06, which is disposed on the side of the photosensitive device Sg away from the substrate 01, for the purpose of protecting the photosensitive device Sg.

[0125] Optionally, the material of at least one of the buffer layer 02, planarization layer 05, and protective layer 06 may be the same as the material of the gate insulating layer 03, such as inorganic insulating materials such as silicon nitride, nitrogen oxide, and silicon oxynitride, or organic insulating materials such as organic resin or other suitable materials, which are not limited here.

[0126] It is understood that in this embodiment, the reading circuit of the active pixel sensor includes an adjustment sub-circuit 1, and the adjustment sub-circuit 1 may include various types of circuit structures. Depending on the different circuit structures, the layer structure of the flat panel detector using the active pixel sensor will also change accordingly, as detailed below.

[0127] In some examples, combined Figure 3 , Figure 15Corresponding to the above embodiment one, if the active pixel sensor described in embodiment one is applied to a flat panel detector, that is, the adjustment sub-circuit 1 of the active pixel sensor includes a first capacitor C1, a second capacitor C2 and a switching transistor Tk, the active layer Ak of ​​the switching transistor Tk is disposed in the same layer as the active layers of other transistors (e.g., the active layer A1 of the follower transistor T1) and is made of the same material, that is, the active semiconductor layer also includes the active layer Ak of ​​the switching transistor Tk; the control electrode Gk of the switching transistor Tk is disposed in the same layer as the control electrode of other transistors (e.g., the control electrode G1 of the follower transistor T1) and is made of the same material, that is, the first conductive layer also includes the control electrode Gk of the switching transistor Tk; the first electrode Sk and the second electrode Dk of the switching transistor Tk are disposed in the same layer as the first electrode and the second electrode of other transistors (e.g., the first electrode S1 and the second electrode S2 of the follower transistor T1) and are made of the same material, that is, the source and drain metal layers also include the first electrode Sk and the second electrode Dk of the switching transistor Tk. The first capacitor C1 and the second capacitor C2 are disposed in the same layer and are composed of two plates. The first plate C11 of the first capacitor C1 and the first plate C21 of the second capacitor C2 are disposed in the same layer and are made of the same material as the first electrode of other transistors (e.g., the first electrode S1 of the follower transistor T1). That is, the source and drain metal layer also includes the first plate C11 of the first capacitor C1 and the first plate C21 of the second capacitor C2. The second plate C12 of the first capacitor C1 and the second plate C22 of the second capacitor C2 are disposed in the same layer and are made of the same material as the control electrode of other transistors (e.g., the control electrode G1 of the follower transistor T1). That is, the first conductive layer also includes the second plate C12 of the first capacitor C1 and the second plate C22 of the second capacitor C2.

[0128] In some examples, combined Figure 6 See also Figure 16 Corresponding to Embodiment 2 above, if the active pixel sensor described in Embodiment 2 is applied to a flat panel detector, that is, the adjustment sub-circuit 1 of the active pixel sensor is a voltage-controlled liquid crystal capacitor C3, the voltage-controlled liquid crystal capacitor C3 includes a first electrode C31, a liquid crystal layer C33, and a second electrode C32 sequentially disposed in the direction from the substrate 01 to the planarization layer 05, and also includes a sealing adhesive disposed between the first electrode C31 and the second electrode C32, located in the edge region of the first electrode C31, to seal the liquid crystal layer C33 between the first electrode C31 and the second electrode C32. The first electrode C31 of the voltage-controlled liquid crystal capacitor C3 is disposed in the same layer and made of the same material as the control electrode of other transistors (e.g., the control electrode G1 of the follower transistor T1), that is, the first conductive layer also includes the first electrode C31 of the voltage-controlled liquid crystal capacitor C3. The second electrode C32 of the voltage-controlled liquid crystal capacitor C3 is disposed in the same layer and made of the same material as the first electrode of other transistors (e.g., the first electrode S1 of the follower transistor T1), that is, the source and drain metal layers also include the second electrode C32 of the voltage-controlled liquid crystal capacitor C3.

[0129] In some examples, corresponding to Embodiment 3 above, if the active pixel sensor described in Embodiment 3 is applied to a flat panel detector, that is, the adjustment sub-circuit 1 of the active pixel sensor includes a varactor diode, which may include an NMOS transistor, a PMOS transistor, a PN diode, a PIN diode, etc.

[0130] See in some examples Figure 7 , Figure 17 If the varactor diode is a PN diode (P1 in the figure), the PN diode includes a fifth electrode P11, an N-type semiconductor layer P13, a P-type semiconductor layer P14, and a sixth electrode P12, which are sequentially disposed on the substrate 01 in the direction pointing towards the planarization layer 05. The fifth electrode P11 is the first terminal of the varactor diode, and the sixth electrode P12 is the second terminal. By applying a voltage between the fifth electrode P11 (receiving VSS) and the sixth electrode P12 (receiving CON1), the barrier voltage between the N-type semiconductor layer P13 and the P-type semiconductor layer P14 is changed, thereby altering the capacitance of the PN diode and adjusting the amplification sensitivity of the follower transistor T1. The fifth electrode P11 is disposed in the same layer and made of the same material as the control electrode of other transistors (e.g., the control electrode G1 of the follower transistor T1), meaning the first conductive layer also includes the fifth electrode P11. Similarly, the sixth electrode P12 is disposed in the same layer and made of the same material as the first electrode of other transistors (e.g., the first electrode S1 of the follower transistor T1), meaning the source and drain metal layers also include the sixth electrode P12.

[0131] Combination Figure 7 , Figure 18 If the varactor diode is a PIN diode (P1ˊ in the figure), the PIN diode includes a third electrode P11ˊ, an N-type semiconductor layer P13ˊ, an intrinsic layer Pi, a P-type semiconductor layer p14ˊ, and a fourth electrode p12ˊ, which are sequentially disposed on the substrate 01 in the direction pointing to the planarization layer 05. The third electrode P11ˊ is the first electrode of the varactor diode, and the fourth electrode p12ˊ is the second electrode of the varactor diode. By applying a voltage between the third electrode P11ˊ (receiving VSS) and the fourth electrode p12ˊ (receiving CON1), the barrier voltage between the N-type semiconductor layer P13ˊ and the P-type semiconductor layer p14ˊ is changed, thereby changing the capacitance of the PIN diode to adjust the amplification sensitivity of the follower transistor T1. The third electrode P11ˊ is disposed in the same layer and made of the same material as the control electrode of other transistors (e.g., the control electrode G1 of the follow transistor T1), that is, the first conductive layer also includes the third electrode P11ˊ; the fourth electrode p12ˊ is disposed in the same layer and made of the same material as the first electrode of other transistors (e.g., the first electrode S1 of the follow transistor T1), that is, the source and drain metal layers also include the fourth electrode p12ˊ.

[0132] In some examples, combined Figure 8 , Figure 19 Corresponding to Embodiment 4 above, if the active pixel sensor described in Embodiment 4 is applied to a flat panel detector, that is, the adjustment sub-circuit 1 of the active pixel sensor is an amorphous metal nonlinear resistor device, the amorphous metal nonlinear resistor device includes a first amorphous metal electrode C41, a second insulating layer C43, and a second amorphous metal electrode C42 sequentially disposed in the direction from the substrate 01 to the planarization layer 05. The thickness of the second insulating layer C43 is between 10-20 nm, and the first amorphous metal electrode C41 and the second amorphous metal electrode C42 are made of amorphous metal, thus having low roughness, thereby reducing the overall volume of the amorphous metal nonlinear resistor device, which is beneficial for integration. The first amorphous metal electrode C41 is disposed in the same layer and made of the same material as the control electrode of other transistors (e.g., the control electrode G1 of the follower transistor T1), that is, the first conductive layer also includes the first amorphous metal electrode C41; the second amorphous metal electrode C42 is disposed in the same layer and made of the same material as the first electrode of other transistors (e.g., the first electrode S1 of the follower transistor T1), that is, the source and drain metal layers also include the second amorphous metal electrode C42.

[0133] In some examples, combined Figure 10 , Figure 20 Corresponding to Embodiment 5 above, if the active pixel sensor described in Embodiment 5 is applied to a flat panel detector, the adjustment sub-circuit 1 of the active pixel sensor includes an adjustment transistor T4. The active layer A4 of the adjustment transistor T4 is co-located with the active layers of other transistors (e.g., the active layer A1 of the follow transistor T1) and made of the same material; that is, the active semiconductor layer also includes the active layer A4 of the adjustment transistor T4. The control electrode G4 of the adjustment transistor T4 is co-located with the control electrodes of other transistors (e.g., the control electrode G1 of the follow transistor T1) and made of the same material; that is, the first conductive layer also includes the control electrode G4 of the adjustment transistor T4. The first electrode S4 and the second electrode D4 of the adjustment transistor T4 are co-located with the first and second electrodes of other transistors (e.g., the first electrode S1 and the second electrode S2 of the follow transistor T1) and made of the same material; that is, the source and drain metal layers also include the first electrode S4 and the second electrode D4 of the adjustment transistor T4.

[0134] In some examples, combined Figure 12 , Figure 21Corresponding to Embodiment Six above, if the active pixel sensor described in Embodiment Six is ​​applied to a flat panel detector, the photosensitive device Sg is a photodiode. The photodiode includes a seventh electrode Sg1, a photosensitive layer Sg2, and an eighth electrode Sg3 sequentially disposed on the planarization layer 05 in the direction away from the substrate 01. If the photodiode is a PIN diode, the photosensitive layer Sg2 includes an N-type semiconductor layer, an intrinsic layer, and a P-type semiconductor layer. The seventh electrode Sg1 is divided into a first sub-electrode Sg11 (i.e., the first electrode of the photosensitive portion Sga) and a second sub-electrode Sg12 (i.e., the first electrode of the varactor portion Sgb), which are not in contact with each other. The portion of the photodiode corresponding to the first sub-electrode Sg11 is the photosensitive portion Sga, which is used as a photosensitive device; the portion of the photodiode corresponding to the second sub-electrode Sg12 is the varactor portion Sgb, which is used as the regulating sub-circuit 1. Specifically, the overlapping portion of the orthographic projections of the first sub-electrode Sg11 on the substrate 01, the orthographic projections of the photosensitive layer Sg2 on the substrate 01, and the orthographic projections of the eighth electrode Sg3 on the substrate 01 defines the photosensitive portion Sga; the overlapping portion of the overlapping projections of the second sub-electrode Sg12 on the substrate 01, the orthographic projections of the photosensitive layer Sg2 on the substrate 01, and the orthographic projections of the eighth electrode Sg3 on the substrate 01 defines the varactor portion Sgb. The photosensitive portion Sga and the varactor portion Sgb are respectively connected to the circuit. Specifically, the first sub-electrode Sg11 is connected to the control electrode of the follower transistor T1 through a via penetrating the planarization layer 05 and the first insulating layer 04 (the connection portion is not shown in the figure), connecting the photosensitive portion Sga to the circuit for use as a photosensitive device. The second sub-electrode Sg12 is connected to the control electrode of the follower transistor T1 through a via penetrating the planarization layer 05 and the first insulating layer 04, connecting the varactor portion Sgb to the circuit for use as the regulating sub-circuit 1 (the connection portion is not shown in the figure). The orthographic projection of the eighth electrode Sg3 onto the substrate 01 can cover the orthographic projection of the first sub-electrode Sg11 onto the substrate 01, and can also cover the orthographic projection of the second sub-electrode Sg12 onto the substrate 01. That is, the photosensitive part Sga and the variable capacitance part Sgb share the eighth electrode Sg3. The eighth electrode Sg3 is connected to the second power supply voltage terminal and receives the second power supply voltage VSS. In order to prevent the photosensitive layer sg2 of the variable capacitance part Sgb from sensing light, the active pixel sensor may also include a light-shielding electrode 07. The light-shielding electrode 07 is disposed on the side of the eighth electrode Sg3 away from the substrate 01, and the orthographic projection of the light-shielding electrode 07 onto the substrate 01 covers the orthographic projection of the second sub-electrode Sg12 onto the substrate 01. Moreover, the orthographic projection of the light-shielding electrode 07 onto the substrate 01 does not overlap with the orthographic projection of the first sub-electrode Sg11 onto the substrate 01. Thus, the light-shielding electrode 07 can block the photosensitive layer Sg12 of the variable capacitance part Sgb, preventing visible light from incident on the variable capacitance part Sgb.The second sub-electrode Sg12 of the varactor section Sgb can be connected to the first control signal terminal to receive the first control signal CON1, while the eighth electrode Sg3 receives the second power supply voltage VSS. By adjusting the voltage of the first control signal CON1, the barrier voltage of the varactor section Sgb can be adjusted, thereby changing the capacitance of the varactor section Sgb, and thus changing the amplification sensitivity of the follower transistor T1.

[0135] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. An active pixel sensor, characterized in that, include: Photosensitive device; The control electrode of the follow transistor is connected to the first electrode of the photosensitive device, and the first electrode is connected to the first power supply voltage terminal; wherein, the first power supply voltage terminal is used to provide the first power supply voltage; An adjustment sub-circuit is configured to adjust the potential between the control electrode and the first electrode of the follower transistor in response to a first control signal, thereby adjusting the amplification sensitivity of the follower transistor; the operation of the active pixel sensor includes a reset phase, an exposure phase, and a readout phase; the adjustment sub-circuit adjusts the amplification sensitivity of the follower transistor before the exposure phase; and the adjustment sub-circuit is capable of decreasing the amplification sensitivity of the follower transistor when the range of electrical signal changes according to visible light conversion of the photosensitive device increases, and capable of increasing the amplification sensitivity of the follower transistor when the range of electrical signal changes according to visible light conversion of the photosensitive device decreases; A read transistor has its control electrode connected to a scan line, its first electrode connected to the second electrode of the follower transistor, and the second electrode connected to the read line; wherein the scan line is used to provide a scan signal.

2. The active pixel sensor according to claim 1, characterized in that, The regulating sub-circuit includes a first capacitor, a second capacitor, and a switching transistor; The first terminal of the first capacitor is connected to the first terminal of the switching transistor; the first terminal of the second capacitor is connected to the second terminal of the switching transistor; and the second terminals of both the first and second capacitors are connected to the control terminal of the follower transistor.

3. The active pixel sensor according to claim 1, characterized in that, The regulating sub-circuit is a voltage-controlled liquid crystal capacitor.

4. The active pixel sensor according to claim 1, characterized in that, The regulating sub-circuit includes a varactor diode.

5. The active pixel sensor according to claim 4, characterized in that, The varactor diode is a PIN diode or a PN diode.

6. The active pixel sensor according to claim 1, characterized in that, The regulating sub-circuit is an amorphous metal nonlinear resistor device.

7. The active pixel sensor according to claim 1, characterized in that, The regulating sub-circuit includes a regulating transistor, the first terminal of which is connected to a second power supply voltage terminal, the second terminal of which is connected to the control terminal of the follower transistor, and the control terminal is connected to the first control signal terminal; wherein, the second power supply voltage terminal is used to provide a second power supply voltage; and the first control signal terminal is used to provide a first control signal.

8. The active pixel sensor according to claim 1, characterized in that, The photosensitive device is a photodiode, which is divided into a photosensitive part and a varactor part. The photosensitive part is connected to the control electrode of the follower transistor and is used to convert visible light into an electrical signal and transmit it to the follower transistor. The varactor part serves as the regulating sub-circuit and is connected to the control electrode of the follower transistor.

9. The active pixel sensor according to any one of claims 1-8, characterized in that, Also includes: A reset transistor has its control terminal connected to a reset signal terminal, its first terminal connected to an initialization signal terminal, and its second terminal connected to the first terminal of the photosensitive device and the control terminal of the follower transistor; wherein, the initialization signal terminal is used to provide the initialization signal; and the reset signal terminal is used to provide the reset control signal.

10. A flat panel detector, characterized in that, It includes the active pixel sensor described in any one of claims 1-9.

11. The flat panel detector according to claim 10, characterized in that, include: A substrate on which multiple active pixel sensor arrays are arranged; An X-ray conversion layer is disposed on the side of the plurality of active pixel sensors facing away from the substrate.

12. The flat panel detector according to claim 11, characterized in that, The flat panel detector further includes: an active semiconductor layer disposed on the substrate, which includes the active layer of the follower transistor and the readout transistor; A gate insulating layer is disposed on the side of the active semiconductor layer opposite to the substrate; A first conductive layer is disposed on the side of the gate insulating layer opposite to the substrate; the first conductive layer includes the follower transistor and the control electrode of the read transistor; A first insulating layer is disposed on the side of the first conductive layer that faces away from the substrate; A source-drain metal layer is disposed on the side of the first insulating layer away from the substrate, and includes the follower transistor, the first electrode of the read transistor, and the second electrode of the read transistor; A planarization layer is disposed on the side of the source / drain metal layer opposite to the substrate.

13. The flat panel detector according to claim 12, characterized in that, The modulation sub-circuit of the active pixel sensor includes a first capacitor, a second capacitor, and a switching transistor; The active semiconductor layer further includes the active layer of the switching transistor; The first conductive layer further includes the control electrode of the switching transistor, the second electrode of the first capacitor, and the second electrode of the second capacitor; The source and drain metal layers also include the first and second electrodes of the switching transistor, the first plate of the first capacitor, and the first plate of the second capacitor.

14. The flat panel detector according to claim 12, characterized in that, The adjustment sub-circuit of the active pixel sensor is a voltage-controlled liquid crystal capacitor, which includes a first electrode, a liquid crystal layer, and a second electrode sequentially disposed on the substrate in the direction pointing towards the planarization layer; wherein... The first electrode is disposed in the same layer as the control electrode of the follower transistor and is made of the same material; the second electrode is disposed in the same layer as the first electrode of the follower transistor and is made of the same material.

15. The flat panel detector according to claim 12, characterized in that, The modulation sub-circuit of the active pixel sensor includes a PIN diode, which comprises a third electrode, an N-type semiconductor layer, an intrinsic layer, a P-type semiconductor layer, and a fourth electrode sequentially disposed on the substrate in the direction pointing towards the planarization layer; wherein... The third electrode is disposed in the same layer as the control electrode of the follower transistor and is made of the same material; the fourth electrode is disposed in the same layer as the first electrode of the follower transistor and is made of the same material.

16. The flat panel detector according to claim 12, characterized in that, The modulation sub-circuit of the active pixel sensor includes a PN diode, which comprises a fifth electrode, an N-type semiconductor layer, a P-type semiconductor layer, and a sixth electrode sequentially disposed on the substrate in the direction pointing towards the planarization layer; wherein... The fifth electrode is disposed in the same layer as the control electrode of the follower transistor and is made of the same material; the sixth electrode is disposed in the same layer as the first electrode of the follower transistor and is made of the same material.

17. The flat panel detector according to claim 12, characterized in that, The adjustment sub-circuit of the active pixel sensor is an amorphous metal nonlinear resistor device, which includes a first amorphous metal electrode, a second insulating layer, and a second amorphous metal electrode sequentially disposed on the substrate in the direction pointing towards the planarization layer; wherein... The first amorphous metal electrode plate is disposed in the same layer as the control electrode of the follower transistor and is made of the same material; the second amorphous metal electrode plate is disposed in the same layer as the first electrode of the follower transistor and is made of the same material.

18. The flat panel detector according to claim 12, characterized in that, The modulation sub-circuit of the active pixel sensor includes a modulation transistor; The active semiconductor layer further includes the active layer of the regulating transistor; the first conductive layer further includes the control electrode of the regulating transistor; the source-drain metal layer further includes the first electrode and the second electrode of the regulating transistor.

19. The flat panel detector according to claim 12, characterized in that, The photosensitive device is a photodiode, which includes a seventh electrode, a photosensitive layer and an eighth electrode sequentially disposed on the planarization layer in the direction away from the substrate; The seventh electrode is divided into a first sub-electrode and a second sub-electrode that do not contact each other. The part of the photodiode corresponding to the first sub-electrode is the photosensitive part, and the part of the photodiode corresponding to the second sub-electrode is the varactor part. The varactor part serves as the regulating sub-circuit. The first sub-electrode is connected to the control electrode of the follower transistor through a via penetrating the planarization layer and the first insulating layer; The second sub-electrode is connected to the control electrode of the follower transistor through a via penetrating the planarization layer and the first insulating layer; The active pixel sensor further includes: a light-shielding electrode disposed on the side of the eighth electrode away from the substrate, wherein the orthographic projection of the light-shielding electrode on the substrate covers the orthographic projection of the second sub-electrode on the substrate and does not overlap with the orthographic projection of the first sub-electrode on the substrate.

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