Pixel unit circuit, reading circuit and infrared imaging sensor

Abstract

The utility model discloses a pixel unit circuit, a readout circuit and an infrared imaging sensor, and the pixel unit circuit comprises a front-end reading module which is used for converting a light current inputted by an infrared detector array into a light voltage and improving the output swing of the light voltage; the amplification and comparison module is connected with the front-end reading module, and is used for sampling the photovoltage, amplifying a change value of the photovoltage to obtain an amplified photovoltage and comparing the amplified photovoltage with a threshold voltage; and the signal resetting module is connected with the amplification and comparison module and is used for outputting a resetting signal to the amplification and comparison module to trigger the amplification and comparison module to sample the light voltage and outputting an event signal according to a comparison result of the amplified light voltage and the threshold voltage. According to the utility model, the front-end reading module is used for increasing the swing of the output photovoltage, so that the sensitivity of the photovoltage signal to noise and interference in the transmission process is reduced, the anti-interference capability of the signal is enhanced, and the signal-to-noise ratio is improved.

Description

Technical Field

[0001] This utility model relates to the field of infrared imaging technology, and in particular to a pixel unit circuit, a readout circuit, and an infrared imaging sensor. Background Technology

[0002] Infrared imaging detection technology, with its characteristics of being unaffected by light and having a certain degree of penetration, is widely used in various fields such as military, firefighting, medical, and civilian applications. Currently, the development direction of infrared imaging detection technology mainly focuses on research and design aimed at multi-band, multi-mode, multi-functional, high-performance, large-array, and high-integration technologies. However, there is relatively little exploration of infrared imaging methods. Currently, the main method of infrared detection imaging is to acquire and output image data of the entire scene at a fixed frame rate.

[0003] Infrared detection imaging, which acquires and outputs image data of the entire scene at a fixed frame rate, provides a clear and intuitive view of the entire image. However, in low-light conditions, the input photocurrent signal is relatively weak, leading to significant noise interference and a low signal-to-noise ratio.

[0004] Therefore, existing technologies still need to be improved and developed. Utility Model Content

[0005] In view of the shortcomings of the prior art, the purpose of this utility model is to provide a pixel unit circuit, a readout circuit and an infrared imaging sensor to solve the problem of low signal-to-noise ratio in existing infrared imaging technology under low light conditions.

[0006] The technical solution of this utility model is as follows:

[0007] In a first aspect, this utility model provides a pixel unit circuit, comprising:

[0008] The front-end reading module is used to convert the photocurrent input from the infrared detector array into photovoltage and increase the output swing of the photovoltage.

[0009] An amplification and comparison module is connected to the front-end reading module. The amplification and comparison module is used to sample the photovoltage and amplify the change value of the photovoltage to obtain the amplified photovoltage, and to compare the amplified photovoltage with a threshold voltage.

[0010] A signal reset module is connected to the amplification and comparison module. The signal reset module is used to output a reset signal to the amplification and comparison module to trigger the amplification and comparison module to sample the optical voltage, and to output an event signal based on the comparison result of the amplified optical voltage and the threshold voltage.

[0011] In a further embodiment of this invention, the front-end reading module includes: a conversion and output swing enhancement unit, a bias current supply unit, and a reverse bias voltage supply unit; wherein,

[0012] The conversion and output swing boosting unit is used to connect to the output terminal of the infrared detector array. The conversion and output swing boosting unit is used to convert the photocurrent input to the infrared detector array into photovoltage and to boost the output swing of the photovoltage. The infrared detector array includes a plurality of infrared detectors.

[0013] The bias current providing unit is connected to the power supply voltage and is connected to the conversion and output swing boosting unit and the reverse bias voltage providing unit respectively. The bias current providing unit is used to provide bias current.

[0014] The reverse bias voltage providing unit is connected to the bias current providing unit, and the reverse bias voltage providing unit is used to provide a reverse bias voltage for the infrared detector.

[0015] In a further embodiment of this invention, the conversion and output swing boosting unit includes a first MOS transistor and a second MOS transistor; the drain of the first MOS transistor is connected to the power supply voltage, the source of the first MOS transistor is connected to the drain of the second MOS transistor, and the gate of the first MOS transistor is connected to the bias current providing unit.

[0016] The source of the second MOS transistor is connected to the cathode of the infrared detector, and the gate of the second MOS transistor is connected to the source of the first MOS transistor.

[0017] In a further embodiment of this invention, the bias current providing unit includes a third MOS transistor, the drain of which is connected to a power supply voltage, the source of which is connected to the gate of the first MOS transistor, and the gate of which is connected to an external bias voltage.

[0018] In a further embodiment of this invention, the reverse bias voltage providing unit includes a fourth MOS transistor, the drain of which is connected to the source of the third MOS transistor, the gate of which is connected to the cathode of the infrared detector, and the source of which is grounded.

[0019] In a further embodiment of this invention, the front-end reading module also includes a capacitor, one end of which is connected to the gate of the fourth MOS transistor, and the other end of which is connected to the drain of the fourth MOS transistor.

[0020] In a further embodiment of this invention, the amplification and comparison module includes: a capacitively coupled inverting amplifier, a first comparator, and a second comparator; wherein,

[0021] The input terminal of the capacitively coupled inverting amplifier is connected to the output terminal of the front-end reading module;

[0022] The feedback terminal of the capacitively coupled inverting amplifier is connected to the signal reset module;

[0023] The output terminal of the capacitively coupled inverting amplifier is connected to the non-inverting input terminal of the first comparator and the non-inverting input terminal of the second comparator, respectively.

[0024] The capacitively coupled inverting amplifier is used to sample the photovoltage output by the front-end reading module according to the reset signal output by the signal reset module, and amplify the change value of the photovoltage to obtain the amplified photovoltage, which is then output to the first comparator and the second comparator.

[0025] The first comparator is used to compare the amplified optical voltage with a first threshold reference voltage and output an Off event signal when the amplified optical voltage reaches the first threshold reference voltage;

[0026] The second comparator is used to compare the amplified optical voltage with a second threshold reference voltage and output an On event signal when the amplified optical voltage reaches the second threshold reference voltage.

[0027] In a second aspect, the present invention also provides a readout circuit, which includes a logic control module, a clock module, a serial peripheral device interface, a bias voltage module, a reference voltage module, an output buffer module, a digital video interface, and a pixel unit circuit as described above.

[0028] The logic control module is connected to the pixel unit circuit and is used to provide control timing for the pixel unit circuit.

[0029] The clock module is connected to the logic control module and is used to provide a reference clock;

[0030] The serial peripheral device interface is connected to the logic control module and is used to write data from the external environment to configure the relevant settings of the pixel unit circuit.

[0031] The bias voltage module is connected to the pixel unit circuit and is used to provide bias voltage to the pixel unit circuit;

[0032] The reference voltage module is connected to the pixel unit circuit and is used to provide a reference voltage for the pixel unit circuit.

[0033] The output buffer module is connected to the pixel unit circuit and is used to buffer the event signals output by the pixel unit circuit.

[0034] The digital video interface is connected to the output buffer module and is used to output the event signal.

[0035] Thirdly, this utility model also provides an infrared imaging sensor, which includes an infrared detector array and a readout circuit as described above.

[0036] In a further embodiment of this invention, the infrared detector array comprises a plurality of infrared detectors arranged in an array.

[0037] This invention provides a pixel unit circuit, a readout circuit, and an infrared imaging sensor. The pixel unit circuit includes: a front-end readout module for converting the photocurrent input from the infrared detector array into a photovoltage and increasing the output swing of the photovoltage; an amplification and comparison module connected to the front-end readout module, which samples the photovoltage, amplifies the change in the photovoltage to obtain an amplified photovoltage, and compares the amplified photovoltage with a threshold voltage; and a signal reset module connected to the amplification and comparison module, which outputs a reset signal to the amplification and comparison module to trigger the amplification and comparison module to sample the photovoltage, and outputs an event signal based on the comparison result of the amplified photovoltage and the threshold voltage. This invention increases the swing of the output photovoltage through the front-end readout module, reducing the sensitivity of the photovoltage signal to noise and interference during transmission, enhancing the signal's anti-interference capability, and thus improving the signal-to-noise ratio. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the imaging system.

[0040] Figure 2 This is a schematic diagram of the infrared imaging sensor of this utility model.

[0041] Figure 3 This is a schematic diagram of the readout circuit in one embodiment of this utility model.

[0042] Figure 4 This is a circuit diagram of the pixel unit circuit in one embodiment of the present invention.

[0043] Figure 5This is a circuit diagram of the front-end reading module in one embodiment of this utility model.

[0044] The labels in the attached diagram are as follows: 100, Infrared detector array; 200, Readout circuit; 210, Logic control module; 220, Clock module; 230, Serial peripheral interface; 240, Bias voltage module; 250, Reference voltage module; 260, Output buffer module; 270, Digital video interface; 280, Pixel unit circuit; 281, Front-end readout module; 2811, Conversion and output swing enhancement unit; 2812, Bias current supply unit; 2813, Reverse bias voltage supply unit; 282, Amplification and comparison module; 283, Signal reset module; 300, Indium pillar. Detailed Implementation

[0045] This utility model provides a pixel unit circuit, a readout circuit, and an infrared imaging sensor. To make the purpose, technical solution, and effects of this utility model clearer and more explicit, the following describes this utility model in further detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of this utility model and are not intended to limit this utility model.

[0046] In the implementation methods and claims, unless otherwise specified in the text, the terms "a," "an," "the," and "the" may also include plural forms. If the embodiments of this utility model involve descriptions of "first," "second," etc., such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features.

[0047] It should be further understood that the term "comprising" as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when an element is referred to as "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements present. Furthermore, "connected" or "coupled" as used herein can include wireless connections or wireless coupling. The term "and / or" as used herein includes all or any of the units and all combinations thereof of one or more associatedly listed items.

[0048] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0049] Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0050] The inventors discovered that current infrared imaging methods primarily rely on capturing and outputting image data of the entire scene at a fixed frame rate. While this method outputs the entire sensed image, providing a clear visual effect, it suffers from excessive repetition in each frame, leading to information redundancy. This wastes significant bandwidth during transmission and storage, resulting in slow system response and an inability to achieve higher frame rates. Low-frame-rate infrared imagers cannot capture fast-moving objects, causing image trailing and blurring. Therefore, current infrared imaging technology suffers from several drawbacks, including data redundancy, slow response, and low frame rates. Furthermore, in low-light conditions, the weak input photocurrent signal makes the infrared imaging system highly susceptible to noise interference, resulting in a low signal-to-noise ratio.

[0051] To address the aforementioned technical problems, this invention provides a pixel unit circuit, a readout circuit, and an infrared imaging sensor. Utilizing the advantages of event camera imaging principles—low data redundancy, high frame rate, and high response speed—and combining the advantages of infrared imaging—such as its independence from visible light and its certain penetrating power—the pixel unit circuit does not output the entire image data as in traditional infrared imaging. Instead, it responds only to changes in the intensity of infrared radiation in the environment and outputs corresponding event signals for imaging. The output image removes static redundant information that has not changed, allowing for data transmission in a shorter time, improving data response speed and bandwidth utilization, and enabling higher frame rates and faster response speeds in the infrared imaging system. Furthermore, by increasing the swing amplitude of the output photovoltage through the front-end readout module, the sensitivity of the photovoltage signal to noise and interference during transmission is reduced, enhancing the signal's anti-interference capability and thus improving the signal-to-noise ratio.

[0052] Please also refer to Figures 1 to 5This utility model provides a preferred embodiment of an infrared imaging sensor.

[0053] In some embodiments, such as Figure 1 and Figure 2 As shown, this utility model provides an infrared imaging sensor, which includes an infrared detector array 100 and a readout circuit 200. The infrared detector array 100 and the readout circuit 200 are associated by bonding, for example, through indium pillars 300. The infrared detector array 100 converts the infrared radiation received from the object under test into a corresponding photocurrent Ipd, which is transmitted to the readout circuit 200 for information processing. Based on changes in the light source, corresponding event signals are generated and transmitted to the imaging device for final visual imaging.

[0054] In this embodiment, the infrared detector array 100 includes a plurality of infrared detectors PDs arranged in an array. The infrared detectors PDs can detect the infrared light intensity in the environment and convert the light intensity into a corresponding photocurrent Ipd. The readout circuit 200 includes a plurality of pixel unit circuits 280 arranged in an array. The pixel unit circuits 280 are associated with the infrared detectors PDs by bonding.

[0055] In some embodiments, such as Figure 3 As shown, the readout circuit 200 includes a logic control module 210, a clock module 220, a serial peripheral device interface 230, a bias voltage module 240, a reference voltage module 250, an output buffer module 260, a digital video interface 270, and an array-configured pixel unit circuit 280. The logic control module 210 is connected to the pixel unit circuit 280 and is used to provide control timing for the pixel unit circuit 280; the clock module 220 is connected to the logic control module 210 and is used to provide a reference clock; the serial peripheral interface 230 is connected to the logic control module 210 and is used to write data from the peripheral to configure the relevant settings of the pixel unit circuit 280; the bias voltage module 240 is connected to the pixel unit circuit 280 and is used to provide a bias voltage for the pixel unit circuit 280; the reference voltage module 250 is connected to the pixel unit circuit 280 and is used to provide a reference voltage for the pixel unit circuit 280; the output buffer module 260 is connected to the pixel unit circuit 280 and is used to buffer the event signals output by the pixel unit circuit 280; the digital video interface 270 is connected to the output buffer module 260 and is used to output the event signals.

[0056] In this embodiment, the number of pixel unit circuits 280 corresponds to the number of infrared detectors in the infrared detector array 100. The pixel unit circuits 280 are respectively connected to the logic control module 210, the clock module 220, the serial peripheral interface 230, the bias voltage module 240, and the output buffer module 260. Taking a 2×8 infrared detector array as an example, the pixel unit circuits 280 are also arranged in a 2×8 array, such as... Figure 3 The pixel unit circuits Pixel(1,0) to Pixel(0,7) are configured in the image. The logic control module 210 and the clock module 220 provide all timing control and a reference clock for the pixel unit circuit 280. The bias voltage module 240 and the reference voltage module 250 provide bias voltage and reference voltage for the pixel unit circuit 280. The serial peripheral interface 230 allows external data to be written to the pixel unit circuit 280 to configure its settings. The event signals output by the pixel unit circuit 280 are buffered by the output buffer module 260 and then output to the imaging device via the digital video interface 270.

[0057] In some embodiments, such as Figure 4 As shown, the pixel unit circuit 280 includes: a front-end reading module 281, an amplification and comparison module 282, and a signal reset module 283. The front-end reading module 281 is used to convert the photocurrent input from the infrared detector array 100 into a photovoltage and increase the output swing of the photovoltage. The amplification and comparison module 282 is connected to the front-end reading module 281. The amplification and comparison module 282 is used to sample the photovoltage and amplify the change value of the photovoltage to obtain an amplified photovoltage, and is used to compare the amplified photovoltage with a threshold voltage. The signal reset module 283 is connected to the amplification and comparison module 282. The signal reset module 283 is used to output a reset signal to the amplification and comparison module 282 to trigger the amplification and comparison module 282 to sample the photovoltage, and is used to output an event signal based on the comparison result of the amplified photovoltage and the threshold voltage.

[0058] In this embodiment, the front-end reading module 281 is connected to the infrared detector, converting the photocurrent input to the infrared detector into photovoltage and increasing the swing of the output photovoltage to reduce noise interference caused by an excessively small output voltage swing, thereby preventing the output accuracy of the pixel unit circuit 280 from being affected. The amplification and comparison module 282 can acquire the photovoltage output by the front-end reading module 281 and amplify the change value of the photovoltage to obtain an amplified photovoltage, where the amplified photovoltage refers to the amplified change value of the photovoltage. The threshold voltage includes a first threshold reference voltage for determining the generation of an Off event and a second threshold reference voltage for determining the generation of an On event, both of which are provided by the reference voltage module 250. The amplification and comparison module 282 compares the amplified photovoltage with the first threshold reference voltage and the second threshold reference voltage, respectively. When the amplified photovoltage reaches the first threshold voltage, an Off event is output; when the amplified photovoltage reaches the second threshold reference voltage, an On event is output. In other words, if the photovoltage remains unchanged, no event signal will be output. This means the system only responds to changes in the infrared radiation intensity in the environment and outputs the corresponding event signal for imaging. The output image removes static, redundant information that hasn't changed, allowing for data transmission in a shorter time. This improves data response speed and bandwidth utilization, enabling higher frame rates and faster response times in the infrared imaging system. The signal reset module 283 outputs the corresponding event signal from the amplification and comparison module 282 to an external imaging device for subsequent imaging operations, and simultaneously generates a corresponding reset signal to return to the amplification and comparison module 282, facilitating sampling for the next signal change.

[0059] In this embodiment, the pixel unit circuit 280 does not output the entire image data as in traditional infrared imaging. Instead, it only responds to changes in the infrared radiation intensity in the environment and outputs corresponding event signals for imaging. Static redundant information that has not changed is removed from the output image, allowing for data transmission in a shorter time. This improves data response speed and bandwidth utilization, enabling higher frame rates and faster response speeds in the infrared imaging system. By fusing infrared imaging with an event camera—combining the advantages of infrared imaging (its independence from visible light and its penetrating power) with the low data redundancy, high frame rate, and high response speed of an event camera—it achieves the capture and imaging of high-speed moving objects in harsh environments such as low light. This can be applied to nighttime autonomous driving, infrared guidance, and other applications. Furthermore, the front-end reading module 281 enhances the swing of the output photovoltage, reducing the sensitivity of the photovoltage signal to noise and interference during transmission, enhancing the signal's anti-interference capability, thereby improving the signal-to-noise ratio and ultimately enhancing image quality. This invention is suitable for infrared dynamic scene detection with low noise, low redundancy, and high response speed, and can be widely used in military reconnaissance, fire monitoring, medical imaging and civilian security.

[0060] In some embodiments, such as Figure 4 and Figure 5 As shown, the front-end reading module 281 includes: a conversion and output swing enhancement unit 2811, a bias current providing unit 2812, and a reverse bias voltage providing unit 2813. The conversion and output swing enhancement unit 2811 is connected to the output terminal of the infrared detector array 100, and converts the photocurrent input to the infrared detector array 100 into a photovoltage, thereby enhancing the output swing of the photovoltage. The bias current providing unit 2812 is connected to a power supply voltage and is connected to both the conversion and output swing enhancement unit 2811 and the reverse bias voltage providing unit 2813, providing a bias current. The reverse bias voltage providing unit 2813 is connected to the bias current providing unit 2812, providing a reverse bias voltage to the infrared detector.

[0061] In this embodiment, the conversion and output swing enhancement unit 2811 is connected to the output terminal of the infrared detector, enabling it to convert the input photocurrent into photovoltage and enhance the output swing of the photovoltage. The bias current providing unit 2812 provides bias current to the pixel unit circuit 280, while the reverse bias voltage providing unit 2813 is connected to the infrared detector, providing a stable reverse bias voltage to the infrared detector. This results in a more uniform dark current generated by the infrared detector, improving its linearity.

[0062] In some embodiments, such as Figure 5 As shown, the conversion and output swing boosting unit 2811 includes a first MOSFET M1 and a second MOSFET M2. The drain of the first MOSFET M1 is connected to a power supply voltage, the source of the first MOSFET M1 is connected to the drain of the second MOSFET M2, and the gate of the first MOSFET M1 is connected to the bias current providing unit 2812. The source of the second MOSFET M2 is connected to the cathode of the infrared detector PD, and the gate of the second MOSFET M2 is connected to the source of the first MOSFET M1. The bias current providing unit 2812 includes a third MOSFET M3. The drain of the third MOSFET is connected to a power supply voltage VDD, the source of the third MOSFET is connected to the gate of the first MOSFET M1, and the gate of the third MOSFET M3 is connected to an external bias voltage VB. The reverse bias voltage providing unit 2813 includes a fourth MOSFET M4. The drain of the fourth MOSFET M4 is connected to the source of the third MOSFET M3, the gate of the fourth MOSFET M4 is connected to the cathode of the infrared detector PD, and the source of the fourth MOSFET M4 is grounded to GND.

[0063] It's important to understand that the front-end reading module 281 converts the photocurrent Ipd generated by the infrared detector PD into a photovoltage Vlog for subsequent circuit processing. Based on the form in which the photocurrent is converted into photovoltage, it can be categorized into two types: linear and logarithmic.

[0064] Linear front-end reading modules use integrating capacitors to integrate the photocurrent and obtain the corresponding photovoltage information. However, the dynamic range of linear circuits is usually narrow, and the response is not ideal if the photocurrent is too weak or too strong. When the photocurrent is too weak, the linearity of the circuit will be affected by non-ideal factors such as circuit noise or dark current. When it is too strong, the linear circuit is more likely to be in a voltage saturation state and can no longer accurately reflect the changes in photocurrent.

[0065] The logarithmic front-end readout module utilizes the subthreshold conductivity of a MOSFET operating in the subthreshold region. The gate-source voltage is logarithmically related to the leakage current flowing through the MOSFET, thus obtaining the corresponding logarithmic voltage information. Logarithmic circuits typically have a wider dynamic range because the photocurrent and photovoltage are logarithmically related during logarithmic conversion, resulting in a "compression" effect. When the photocurrent increases logarithmically, the photovoltage increases linearly, and the rate of increase in photovoltage is very slow relative to the photocurrent. This characteristic prevents the photovoltage from increasing as sharply as the photocurrent in high-intensity regions, thus avoiding voltage saturation. Simultaneously, in low-intensity regions, even small changes in photocurrent become more noticeable, improving the circuit's sensitivity to photocurrent detection. Therefore, logarithmic readout circuits can adapt to light intensity variations from extremely low to extremely high, exhibiting a wider dynamic range than linear circuits. Furthermore, the logarithmic relationship helps compress noise signals, optimizing the circuit's signal-to-noise ratio. In some applications, logarithmic circuits can also better simulate human visual perception, providing a more human-like visual response.

[0066] In this embodiment, the first MOS transistor M1 is a converter that converts the photocurrent generated by the infrared detector into a logarithmic photovoltage. The second MOS transistor M2 is connected between the first MOS transistor M1 and the infrared detector PD, which can increase the output swing of the photovoltage. Both the first MOS transistor M1 and the second MOS transistor M2 operate in the subthreshold region. The third MOS transistor M3 is a bias transistor that provides bias current to the pixel unit circuit 280. The gate of the third MOS transistor M3 is connected to the bias voltage module 240, and the gate of the third MOS transistor M3 is connected to the bias voltage provided by the bias voltage module 240. The fourth MOS transistor M4 is a feedback transistor. The third MOS transistor M3 provides a stable reverse bias voltage to the infrared detector PD. The anode of the infrared detector is connected to the bias voltage Vpd_bias to ensure that the infrared detector is in a normal bias state. Figure 3 In this configuration, node Vin is the input port for photocurrent, and the photovoltage output port Vout is the common terminal for the first MOS transistor M1, the third MOS transistor M3, and the fourth MOS transistor M4. In this embodiment, the first MOS transistor M1, the second MOS transistor M2, and the fourth MOS transistor M4 are N-type MOS transistors, and the third MOS transistor M3 is a P-type MOS transistor.

[0067] In this embodiment, the readout circuit 200 needs to operate at an ultra-low temperature of 77K. When the temperature decreases, the output swing of the photovoltage output by the front-end readout module will drop significantly. An excessively small output swing is more susceptible to noise interference, affecting the circuit's output accuracy. Therefore, in this embodiment, a second MOS transistor M2, using a diode connection method, is added below the conversion transistor (first MOS transistor M1) to increase the output voltage swing.

[0068] Simulation results show that, at a temperature of 77K and a power supply voltage of 2.5V, the dynamic range of the front-end reading module 281 is 66dB. When the photocurrent input range is 1nA to 10nA, the photovoltage output swing is 85.7mV, the linearity of the photocurrent-to-photovoltage conversion is 98.13%, and the circuit injection efficiency is 99%. It is evident that this embodiment not only increases the dynamic range of the circuit by employing a logarithmic reading circuit structure, allowing for a measurable photocurrent range of 1nA-2000nA, but also, within the infrared photocurrent detection range of 1-10nA, by adding a second MOSFET M2, the output voltage swing of the pixel unit circuit 280 is doubled, resulting in a better signal-to-noise ratio.

[0069] In some embodiments, the front-end reading module 281 further includes a capacitor Cc, one end of which is connected to the gate of the fourth MOS transistor M4, and the other end of which is connected to the drain of the fourth MOS transistor M4.

[0070] In this embodiment, the capacitor Cc can improve the phase margin of the pixel unit circuit 280, so that the front-end reading module 281 remains stable during closed-loop operation.

[0071] In some embodiments, such as Figure 4As shown, the amplification and comparison module 282 includes: a capacitively coupled inverting amplifier IA, a first comparator CP1, and a second comparator CP2. The input terminal of the capacitively coupled inverting amplifier IA is connected to the output terminal of the front-end reading module 281; the feedback terminal of the capacitively coupled inverting amplifier IA is connected to the signal reset module 283; the output terminal of the capacitively coupled inverting amplifier IA is connected to the non-inverting input terminal of the first comparator CP1 and the non-inverting input terminal of the second comparator CP2, respectively; the capacitively coupled inverting amplifier IA is used to sample the photovoltage output by the front-end reading module 281 according to the reset signal output by the signal reset module 283, and amplify the change value of the photovoltage to obtain the amplified photovoltage -K×ΔVlog, which is then output to the first comparator CP1 and the second comparator CP2; the first comparator CP1 is used to compare the amplified photovoltage -K×ΔVlog with the first threshold reference voltage Vref_Off and output an Off event signal when the amplified photovoltage -K×ΔVlog reaches the first threshold reference voltage Vref_Off; the second comparator CP2 is used to compare the amplified photovoltage -K×ΔVlog with the second threshold reference voltage Vref_On and output an On event signal when the amplified photovoltage -K×ΔVlog reaches the second threshold reference voltage Vref_On.

[0072] In this embodiment, after the front-end reading module 281 outputs a continuously changing photovoltage signal, it is output to the analog event processing module. This module mainly consists of a comparator group composed of a capacitively coupled inverting amplifier IA, a first comparator CP1, and a second comparator CP2, and a signal reset module 283. The voltage output by the capacitively coupled inverting amplifier IA after each reset is a fixed value, which changes with the photovoltage generated by the front-end reading module 281. The capacitively coupled inverting amplifier IA continuously samples the photovoltage and amplifies the continuous change in the sampled photovoltage to obtain an amplified photovoltage -K×ΔVlog. When this change exceeds a set threshold, an event is generated; otherwise, sampling continues. The amplified photovoltage -K×ΔVlog output by the capacitively coupled inverting amplifier IA is input to the first comparator CP1 and the second comparator CP2. The first comparator CP1 is connected to a first threshold reference voltage Vref_Off, and the second comparator CP2 is connected to a second threshold reference voltage Vref_On. Both the first threshold reference voltage Vref_Off and the second threshold reference voltage Vref_On are provided by the reference voltage module 250. The first comparator CP1 compares the amplified optical voltage -K×ΔVlog with a first threshold reference voltage Vref_Off. When the amplified optical voltage -K×ΔVlog reaches the first threshold reference voltage Vref_Off, it flips and outputs an Off event signal. For example, if the optical voltage -K×ΔVlog drops to the set first threshold reference voltage Vref_Off compared to a previous time, the first comparator CP1 outputs an Off event, that is, the Off signal flips from high level to low level. The second comparator CP2 compares the amplified optical voltage -K×ΔVlog with a second threshold reference voltage Vref_On. When the amplified optical voltage -K×ΔVlog reaches the second threshold reference voltage Vref_On, it flips and outputs an On event signal. For example, if the optical voltage rises to the set second threshold reference voltage compared to a previous time, the second comparator CP2 outputs an On event, that is, the On signal flips from low level to high level. The event signals corresponding to the flipping of the first comparator CP1 and the second comparator CP2 are input to the signal reset module 283. The signal reset module 283 outputs the corresponding Off event signal and On event signal to the external imaging device, and simultaneously generates a reset signal Reset back to the capacitively coupled inverting amplifier IA to reset the change of the capacitively coupled inverting amplifier IA so as to start sampling the next signal change.It can be understood that an event signal will only be output when the first comparator CP1 or the second comparator CP2 flips. That is, it will only respond to changes in the infrared radiation intensity in the environment and output the corresponding event signal for imaging, thereby removing static redundant information that has not changed from the output image.

[0073] In summary, the pixel unit circuit, readout circuit, and infrared imaging sensor provided by this utility model have the following beneficial effects:

[0074] By combining the advantages of infrared imaging, such as not relying on visible light and having a certain degree of penetration, with an event camera that has low data redundancy, high frame rate, and high response speed, it is possible to capture and image high-speed moving objects in harsh environments such as low light. This technology can be applied to nighttime autonomous driving, infrared guidance, and other fields, and has certain research value.

[0075] Unlike traditional infrared imaging, which outputs the entire image data, the pixel unit circuit only responds to changes in the intensity of infrared radiation in the environment and outputs corresponding event signals for imaging. The static redundant information that has not changed is removed from the output image, which allows data transmission to be completed in a shorter time, improving the data response speed and bandwidth utilization, and enabling higher frame rates and faster response speeds in infrared imaging systems.

[0076] By increasing the swing of the output photovoltage through the front-end reading module, the sensitivity of the photovoltage signal to noise and interference during transmission is reduced, enhancing the signal's anti-interference capability and thus improving the signal-to-noise ratio.

[0077] It should be understood that the application of this utility model is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A pixel unit circuit, characterized in that, include: The front-end reading module is used to convert the photocurrent input from the infrared detector array into photovoltage and increase the output swing of the photovoltage. An amplification and comparison module is connected to the front-end reading module. The amplification and comparison module is used to sample the photovoltage and amplify the change value of the photovoltage to obtain the amplified photovoltage, and to compare the amplified photovoltage with a threshold voltage. A signal reset module is connected to the amplification and comparison module. The signal reset module is used to output a reset signal to the amplification and comparison module to trigger the amplification and comparison module to sample the optical voltage, and to output an event signal based on the comparison result of the amplified optical voltage and the threshold voltage.

2. The pixel unit circuit according to claim 1, characterized in that, The front-end reading module includes: a conversion and output swing enhancement unit, a bias current supply unit, and a reverse bias voltage supply unit; wherein... The conversion and output swing boosting unit is used to connect to the output terminal of the infrared detector array. The conversion and output swing boosting unit is used to convert the photocurrent input to the infrared detector array into photovoltage and to boost the output swing of the photovoltage. The infrared detector array includes a plurality of infrared detectors. The bias current providing unit is connected to the power supply voltage and is connected to the conversion and output swing boosting unit and the reverse bias voltage providing unit respectively. The bias current providing unit is used to provide bias current. The reverse bias voltage providing unit is connected to the bias current providing unit, and the reverse bias voltage providing unit is used to provide a reverse bias voltage for the infrared detector.

3. The pixel unit circuit according to claim 2, characterized in that, The conversion and output swing boosting unit includes a first MOSFET and a second MOSFET; the drain of the first MOSFET is connected to the power supply voltage, the source of the first MOSFET is connected to the drain of the second MOSFET, and the gate of the first MOSFET is connected to the bias current providing unit. The source of the second MOS transistor is connected to the cathode of the infrared detector, and the gate of the second MOS transistor is connected to the source of the first MOS transistor.

4. The pixel unit circuit according to claim 3, characterized in that, The bias current providing unit includes a third MOS transistor, the drain of which is connected to a power supply voltage, the source of which is connected to the gate of the first MOS transistor, and the gate of which is connected to an external bias voltage.

5. The pixel unit circuit according to claim 4, characterized in that, The reverse bias voltage providing unit includes a fourth MOS transistor, the drain of which is connected to the source of the third MOS transistor, the gate of which is connected to the cathode of the infrared detector, and the source of which is grounded.

6. The pixel unit circuit according to claim 5, characterized in that, The front-end reading module also includes a capacitor, one end of which is connected to the gate of the fourth MOS transistor, and the other end of which is connected to the drain of the fourth MOS transistor.

7. The pixel unit circuit according to claim 1, characterized in that, The amplification and comparison module includes: a capacitively coupled inverting amplifier, a first comparator, and a second comparator; wherein... The input terminal of the capacitively coupled inverting amplifier is connected to the output terminal of the front-end reading module; The feedback terminal of the capacitively coupled inverting amplifier is connected to the signal reset module; The output terminal of the capacitively coupled inverting amplifier is connected to the non-inverting input terminal of the first comparator and the non-inverting input terminal of the second comparator, respectively. The capacitively coupled inverting amplifier is used to sample the photovoltage output by the front-end reading module according to the reset signal output by the signal reset module, and amplify the change value of the photovoltage to obtain the amplified photovoltage, which is then output to the first comparator and the second comparator. The first comparator is used to compare the amplified optical voltage with a first threshold reference voltage and output an Off event signal when the amplified optical voltage reaches the first threshold reference voltage; The second comparator is used to compare the amplified optical voltage with a second threshold reference voltage and output an On event signal when the amplified optical voltage reaches the second threshold reference voltage.

8. A readout circuit, characterized in that, It includes a logic control module, a clock module, a serial peripheral device interface, a bias voltage module, a reference voltage module, an output buffer module, a digital video interface, and several pixel unit circuits as described in any one of claims 1-7; The logic control module is connected to the pixel unit circuit and is used to provide control timing for the pixel unit circuit. The clock module is connected to the logic control module and is used to provide a reference clock; The serial peripheral device interface is connected to the logic control module and is used to write data from the external environment to configure the relevant settings of the pixel unit circuit. The bias voltage module is connected to the pixel unit circuit and is used to provide bias voltage to the pixel unit circuit; The reference voltage module is connected to the pixel unit circuit and is used to provide a reference voltage for the pixel unit circuit. The output buffer module is connected to the pixel unit circuit and is used to buffer the event signals output by the pixel unit circuit. The digital video interface is connected to the output buffer module and is used to output the event signal.

9. An infrared imaging sensor, characterized in that, It includes an infrared detector array and a readout circuit as described in claim 8.

10. The infrared imaging sensor according to claim 9, characterized in that, The infrared detector array comprises several infrared detectors arranged in an array.

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