Light path device of visible near-infrared detector array test calibration system

Abstract

The embodiment of the invention discloses a light path device of a visible near-infrared detector array test calibration system, and the light path device of the visible near-infrared detector array test calibration system comprises a single photon source module which is used for generating near-infrared photons; the visible light generation module is used for generating visible light; and the optical focusing module adopts a coaxial light path and is used for focusing the photons output by the single photon source module and the visible light output by the visible light generation module to a photosensitive surface of the detector array to be tested.

Description

Technical Field

[0001] The present disclosure relates to the field of measurement and calibration technology, and in particular to an optical path device of a visible near-infrared detector array test and calibration system. Background Art

[0002] A single-photon avalanche photodiode is a semiconductor optoelectronic device with internal photocurrent gain, which has the ability to detect extremely weak light signals at the single-photon energy level. Its avalanche effect is a mechanism that causes PN junction breakdown. It uses the impact ionization effect of photogenerated carriers in the diode depletion layer to obtain the avalanche multiplication of photocurrent. When the bias voltage of a reverse-biased PN junction is high enough and the internal electric field in the space charge region is strong enough, the electron-hole pairs generated by the impact ionization can be continuously heated by the electric field and generate new hole-electron pairs. Then, these new hole-electron pairs will further impact ionize to generate more hole-electron pairs. Continuous impact ionization increases the number of carriers, and finally forms an avalanche current under the action of the electric field. At this time, the single-photon avalanche photodiode operates in Geiger mode (also called single-photon mode). In this mode, the internal gain of the single-photon avalanche photodiode can reach more than 106.

[0003] However, different parameters of existing SPAD devices require the use of different measuring instruments, multi-source meters, and peripheral circuits. Although the multi-source meter has high precision, it is also very expensive. The high precision far exceeds the needs of the SPAD device test system. Therefore, it is very meaningful to develop a high-precision, low-cost, easy-to-operate integrated test and calibration system for detectors. Summary of the invention

[0004] This disclosure section is provided to introduce concepts in a brief form, which will be described in detail in the detailed description section below. This disclosure section is not intended to identify key features or essential features of the claimed technical solution, nor is it intended to limit the scope of the claimed technical solution.

[0005] The disclosed embodiment provides an optical path device of a visible-near-infrared detector array test and calibration system, comprising: a single-photon source module for generating near-infrared photons; a visible light generating module for generating visible light; an optical focusing module, which adopts a coaxial optical path, and is used to focus the photons output by the single-photon source module and the visible light output by the visible light generating module onto the photosensitive surface of the detector array to be tested; wherein the test and calibration system comprises: a high-voltage bias circuit for providing a high-voltage bias to the detector array to be tested; an array scanning module for scanning the detectors in the detector array to be tested and outputting electrical signals; an array fixing module for fixing the detector array to be tested; and a control module for generating performance parameters of the detector array to be tested based on the electrical signals.

[0006] In some embodiments, the single-photon source module is used to output a pulsed single-photon source, and the output laser pulse is attenuated to 0.1 photons per pulse through an adjustable attenuator.

[0007] In some embodiments, the optical focusing module includes a microscope, which is positioned along the XY direction and focused along the Z direction with an adjustment accuracy of 1 μm.

[0008] In some embodiments, an aperture stop is also included, and the aperture stop can be translated along the XY direction, and the size of the aperture stop is smaller than the entrance pupil of the microscope lens; wherein, during the translation of the aperture stop, the incident angle of the laser incident on the detector array to be measured also changes.

[0009] In some embodiments, the optical focusing module includes the first beam splitter prism and the second beam splitter prism; wherein the first beam splitter prism is arranged between the aperture stop and the optical focusing module, and is used to guide the laser photons or visible light to the optical focusing module; the second beam splitter prism is arranged to guide the visible light to the first beam splitter prism.

[0010] In some embodiments, a CCD is also included; the near-infrared photons and the visible light observed by the CCD are focused on the detector array to be tested by the same microscope lens.

[0011] In some embodiments, the CCD and illumination LED are used to focus light onto the photosensitive surface of the array to be tested prior to testing.

[0012] In some embodiments, the single-photon source module receives a synchronization signal sent by a control circuit; the control module generates two synchronization signals; the first synchronization signal couples a periodic narrow gated pulse to the detector array to be tested to drive the detector array to be tested; the second synchronization signal is synchronized to the single-photon source module to align the narrow gated pulse with the optical signal generated by the single-photon source module.

[0013] In some embodiments, when the test and calibration system is in a dark count test state, the single photon source in the optical path device is in a closed state; wherein the dark count rate is generated in the following manner: when the detector array to be tested is in a dark room and no light is added, the signal extraction and identification module transmits the obtained pulse signal to the control module; the control module counts the number of pulses of the counting pulse to obtain the dark count, and generates the dark count rate based on the dark count.

[0014] In some embodiments, when the test and calibration system is in a light counting rate test state or a post-pulse probability test state, the single photon source in the optical path device is in an on state; wherein the light counting rate is generated in the following manner: the detector array to be tested receives one or more photons in the detection gate, and the signal extraction and identification transmits the obtained pulse signal to the control module using the edge latching method; the control module counts the number of pulses of the counting pulse to obtain the light count, and generates the light counting rate based on the light count; wherein the post-pulse probability is generated in the following manner: the detector array to be tested receives one or more photons in the detection gate, and the signal extraction and identification transmits the obtained pulse signal to the control module using the double gating method; the control module counts the number of pulses of the counting pulse to obtain the post-pulse number, and generates the post-pulse probability based on the post-pulse number. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and the originals and elements are not necessarily drawn to scale.

[0016] Figure 1 It is a schematic diagram of an optical path device of a first visible near-infrared detector array test and calibration system provided in an embodiment of the present application;

[0017] Figure 2 It is a schematic diagram of the first visible near-infrared detector array test and calibration system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0018] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as being limited to the embodiments described herein, which are instead provided for a more thorough and complete understanding of the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not intended to limit the scope of protection of the present disclosure.

[0019] It should be understood that the various steps described in the method embodiments of the present disclosure may be performed in different orders and / or in parallel. In addition, the method embodiments may include additional steps and / or omit the steps shown. The scope of the present disclosure is not limited in this respect.

[0020] The term "including" and its variations used herein are open inclusions, i.e., "including but not limited to". The term "based on" means "based at least in part on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The relevant definitions of other terms will be given in the following description.

[0021] It should be noted that the concepts such as "first" and "second" mentioned in the present disclosure are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units.

[0022] It should be noted that the modifications of "one" and "plurality" mentioned in the present disclosure are illustrative rather than restrictive, and those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0023] In view of the above problems, the present application provides the following embodiments to solve them.

[0024] See also Figure 1 The present application embodiment provides an overall view of an optical path device of a visible near-infrared detector array test and calibration system ( Figure 1 The arrow in the figure indicates the propagation direction of light), and may include: a single photon source module for generating near-infrared photons; a visible light generating module for generating visible light; and an optical focusing module, which adopts a coaxial optical path and is used to focus the photons output by the single photon source module and the visible light output by the visible light generating module onto the photosensitive surface of the detector array to be tested.

[0025] The test and calibration system includes: a high-voltage bias circuit for providing a high-voltage bias to the detector array to be tested; an array scanning module for scanning the detectors in the detector array to be tested and outputting electrical signals; an array fixing module for fixing the detector array to be tested; and a control module for generating performance parameters of the detector array to be tested based on the electrical signals. As an example, Figure 1 The visible near-infrared detector array test and calibration system shown in the figure may include a high-voltage bias circuit (1), an optical focusing module (2), an APD array scanning module (3), a signal extraction and identification module (4), a single-photon source module (5), an FPGA control module (6), a human-computer interaction interface (7), and a TEC cooling module.

[0026] The single photon source module can generate a single photon, that is, a single light quantum. In the field of quantum communication and precision measurement, the single photon source is very important. The technical effect is that it can provide single photons with high purity and high stability for experiments or tests.

[0027] The visible light generation module can generate visible light, which is the light wave that the human eye can perceive. Visible light is necessary in many applications, such as lighting, display and optical testing. It can provide a stable and controllable visible light source.

[0028] The optical focusing module adopts a coaxial optical path design, which can focus the light generated by the single photon source module and the visible light generation module to one point. The coaxial optical path means that the light beam propagates along the same axis, which helps to improve the focusing accuracy. In this way, the light can be accurately focused on the photosensitive surface of the detector array for effective testing.

[0029] The high voltage bias circuit can provide high voltage to the detector array. In some photodetectors, high voltage needs to be applied to improve their performance or perform specific tests. This can stably provide the required high voltage to ensure the performance of the detector array during the test process.

[0030] The array scanning module is used to scan each detector in the detector array and output the corresponding electrical signal. The scanning can be performed by physical movement or electronic means. This can detect the performance of each detector and provide data for subsequent analysis.

[0031] The array fixing module is used to fix the detector array to ensure the stable position during the test and avoid the test results being affected by movement. This ensures the stability and repeatability of the detector array during the test.

[0032] The control module is responsible for receiving the electrical signals output by the array scanning module and generating the performance parameters of the detector array based on these signals. The control module may include data processing and analysis software to evaluate the performance of the detector. This provides a comprehensive evaluation of the performance of the detector array and helps optimize the design and improve performance.

[0033] In some embodiments, the single-photon source module is used to output a pulsed single-photon source, and the output laser pulse is attenuated to 0.1 photons per pulse through an adjustable attenuator.

[0034] A pulsed single photon source is a single photon source that can output a single photon in the form of a pulse. The pulsed output allows photons to be generated precisely at a specific point in time, which is very important for experiments and applications that require time resolution.

[0035] A laser pulse is a short burst of light emitted by a laser, with high energy and short duration. In a single-photon source, laser pulses can be used to generate single photons.

[0036] Variable attenuators can adjust the intensity of light and are usually used to reduce the intensity of light. Variable attenuators are used to reduce the number of photons in a laser pulse.

[0037] 0.1 photons per pulse means that after attenuation, each laser pulse contains only about 0.1 photons. This is a very low number of photons, meaning that on average there is only a one in ten chance of a photon being present in each pulse, which helps achieve precise control at the single-photon level.

[0038] Therefore, through the adjustable attenuator, precise control of the output of the single photon source can be achieved. Reducing the number of photons in each pulse can reduce the noise caused by multi-photon events and improve the signal-to-noise ratio of the system. By adjusting the attenuator, it can adapt to different experimental conditions and needs, providing experimental flexibility. In general, this technology can provide strong support for precision experiments and applications that require single photons or extremely low photon numbers.

[0039] In some embodiments, the optical focusing module includes a microscope, which is positioned along the XY direction and focused along the Z direction with an adjustment accuracy of 1 μm.

[0040] Microscope: A microscope is an optical instrument used to observe small objects or details. In optical testing and precision operations, microscopes can provide high-resolution imaging.

[0041] XY positioning refers to the ability of a microscope to move in two directions (X and Y) in the horizontal plane. XY positioning allows the microscope to be precisely aimed at a sample or area of ​​interest.

[0042] Z-axis focusing refers to the ability of a microscope to adjust in the vertical direction (Z-axis) to change the focal length and ensure image clarity. Z-axis focusing is the key to achieving precise focusing.

[0043] Adjustment accuracy is 1μm: This means that the movement and adjustment of the microscope in the three directions of XYZ can reach an accuracy of 1 micron (μm). 1 micron is equal to one thousandth of a millimeter, which is a very fine scale, that is, the system has a very high positioning and focusing accuracy.

[0044] As a result, high-resolution imaging can be achieved, and the microscope can achieve very fine imaging. The high precision of XY positioning and Z focusing allows the microscope to accurately align the target area, ensuring the accuracy of the test or operation. The high-precision adjustment capability enables the microscope to adapt to different samples or test conditions, providing greater flexibility. The high-precision adjustment system can ensure the repeatability of each operation and improve the reliability of experiments or tests. Fast and accurate positioning and focusing can reduce setup time and improve work efficiency.

[0045] In some embodiments, an aperture stop is also included, and the aperture stop can be translated along the XY direction, and the size of the aperture stop is smaller than the entrance pupil of the microscope lens; wherein, during the translation of the aperture stop, the incident angle of the laser incident on the detector array to be measured also changes.

[0046] The optical path device also includes an aperture stop. An aperture stop is an optical element used to limit or adjust the diameter of a light beam entering an optical system. By changing the size of the aperture, the intensity and focusing characteristics of the light beam can be controlled.

[0047] XY Translation: This means that the aperture stop can be moved in the X and Y directions on the horizontal plane to change the incident position or shape of the light beam.

[0048] The entrance pupil of a microscope lens is the opening in an optical system that receives light, usually located at the front of the microscope lens. The aperture diaphragm is smaller than the entrance pupil, meaning it can adjust the light beam without completely blocking the light.

[0049] The incident angle is the angle between the light and the normal of the detector array surface to be measured. Changing the incident angle can affect the distribution and reflection characteristics of light on the detector.

[0050] As a result, the aperture diaphragm can precisely control the size of the beam entering the system, helping to optimize the focusing effect and beam quality. By translating the aperture diaphragm in the XY direction, the beam can be positioned at different locations for different testing or operational needs. Translation of the aperture diaphragm results in a change in the angle of incidence, which can be used to study the response of the detector array to different incident angles, or to adjust the interaction between the beam and the detector. By precisely controlling the angle of incidence, the performance of the detector array can be more accurately tested and evaluated, especially in applications where angle dependence needs to be considered. The ability to move the aperture diaphragm provides versatility in experiments, allowing researchers to explore the performance of the detector under different conditions. By adjusting the aperture diaphragm, the beam quality and focusing characteristics of the entire optical system can be optimized, thereby improving the overall performance of the system.

[0051] In some embodiments, the optical focusing module includes the first beam splitter prism and the second beam splitter prism; wherein the first beam splitter prism is arranged between the aperture stop and the optical focusing module, and is used to guide the laser photons or visible light to the optical focusing module; the second beam splitter prism is arranged to guide the visible light to the first beam splitter prism.

[0052] The optical focusing module is responsible for focusing light of different wavelengths (such as laser photons and visible light) to a specific point or area.

[0053] A beam splitter is an optical component that can separate an incoming beam of light by wavelength or direction. In this description, a beam splitter is used to direct light of different wavelengths to the correct path.

[0054] First beam splitter: This is a beam splitter in the optical focusing module, set between the aperture stop and the optical focusing module. Its function is to guide laser photons or visible light to the optical focusing module.

[0055] Second beam splitter prism: This is another beam splitter prism, set at another position in the optical system, used to guide visible light to the first beam splitter prism.

[0056] Therefore, by using a beam splitter, the optical path can be effectively managed to ensure that laser photons and visible light can be transmitted along the intended path.

[0057] The use of beam splitters provides a flexible way to control and adjust the optical path to suit different test or application requirements. By precisely guiding the light beam to the optical focusing module, the accuracy and quality of focusing can be improved. Beam splitters allow the system to process multiple wavelengths of light at the same time, which is very useful for applications that require simultaneous analysis or testing of different types of light. By properly configuring the beam splitter, the performance of the entire optical system can be optimized, improving the accuracy and reliability of the test or experiment.

[0058] In some embodiments, a CCD is also included; the near-infrared photons and the visible light observed by the CCD are focused on the detector array to be tested by the same microscope lens.

[0059] CCD, Charge-Coupled Device, is a semiconductor device that can convert light into electrical signals.

[0060] As a result, CCD has high resolution and can provide clear images, which is very important for accurate testing and calibration of detector arrays. By using the same microscope lens to focus visible light and near-infrared photons, it is possible to ensure that the positions of the two types of light on the detector array are precisely aligned, allowing for simultaneous observation. By centralizing the testing of visible light and near-infrared light, equipment configuration and testing time can be reduced, improving test efficiency.

[0061] In some embodiments, the CCD and illumination LED are used to focus light onto the photosensitive surface of the array to be tested prior to testing.

[0062] Lighting LED, Light Emitting Diode, is used as a light source here to provide the lighting required for the test.

[0063] Focusing: refers to the process of concentrating light onto a point or a small area so that it can be accurately irradiated onto the photosensitive surface of the detector array to be tested.

[0064] The photosensitive surface of the array to be tested refers to the light-sensitive part of the detector array, which is the area that receives and converts light signals into electrical signals.

[0065] Before the test: refers to the preparation work that needs to be done before the formal performance test of the detector array.

[0066] Thus, the use of illumination LEDs can provide a stable and uniform light source, ensuring consistent illumination conditions on the photosensitive surface. Focusing the light source by CCD and illumination LED before testing can ensure that the photosensitive surface of the detector array to be tested is accurately and evenly illuminated. Improve test accuracy. By precisely controlling the lighting conditions, the variables in the test process can be reduced, and the accuracy and reliability of the test results can be improved. Optimize the test process. Focusing the light source before the test helps to optimize the test process and ensure the smooth progress of the test. Strong adaptability This configuration allows the system to adapt to different test conditions and requirements, improving the flexibility of the system. By pre-focusing the light source, the adjustment time during the test can be reduced and the test efficiency can be improved. CCD can be used to monitor and calibrate the focus of the light source to ensure the consistency and repeatability of the test conditions.

[0067] The combined use of CCD and lighting LED provides an efficient and accurate light source control method for the optical path device of the visible near-infrared detector array test and calibration system, which helps to improve the quality and efficiency of the test.

[0068] In some embodiments, the single-photon source module receives a synchronization signal sent by a control circuit; the control module generates two synchronization signals; the first synchronization signal couples a periodic narrow gated pulse to the detector array to be tested to drive the detector array to be tested; the second synchronization signal is synchronized to the single-photon source module to align the narrow gated pulse with the optical signal generated by the single-photon source module.

[0069] Control circuit is an electronic system responsible for generating control signals to coordinate and drive the various components in the entire test system.

[0070] Synchronization signals are used to ensure that different parts of the system operate in sync.

[0071] The periodic narrow gate pulse refers to a pulse signal with a short duration periodically generated by the control module, which is used to control the test process of the detector array.

[0072] Coupling is the process of delivering a synchronization signal to the detector array under test. The transmission or reception of the signal is controlled by a gating pulse.

[0073] Thus, the two synchronization signals generated by the control module ensure that the operation of the detector array and the single photon source module can be precisely synchronized. The synchronization mechanism allows the detector array to receive the light signal at a precise moment, thereby improving the accuracy and reliability of the test. The control module can generate and manage multiple synchronization signals, which enhances the control ability of the test process.

[0074] The system design allows independent synchronization control of different parts, providing greater flexibility and adaptability. Through the synchronization signal, the start and end of the test can be accurately controlled to optimize the entire test process. The synchronization mechanism helps to reduce errors caused by time asynchrony and ensure the accuracy of test results.

[0075] In some embodiments, when the test and calibration system is in a dark count test state, the single photon source in the optical path device is in a closed state; wherein the dark count rate is generated in the following manner: when the detector array to be tested is in a dark room and no light is added, the signal extraction and identification module transmits the obtained pulse signal to the control module; the control module counts the number of pulses of the counting pulse to obtain the dark count, and generates the dark count rate based on the dark count.

[0076] The dark count test state is a test state in which the system receives no external light source and is used to measure the noise level of the detector under no light conditions.

[0077] The off state means that the single-photon source does not generate photons during the dark count test, that is, it does not work.

[0078] Darkroom: A completely dark environment used to isolate external light sources and ensure that the test is not disturbed by external light.

[0079] The signal extraction and identification module is responsible for receiving signals from the detector array and extracting and identifying useful pulse signals from them.

[0080] The control module is responsible for coordinating and controlling the test process, including statistics and analysis of data.

[0081] Pulse Signal: A signal detected by a detector array, usually represented as an electrical pulse.

[0082] Dark counts are counts produced by the detector array due to noise or other non-optical signal sources in the absence of external light sources.

[0083] The dark count rate, the number of dark counts per unit time, is an important parameter for evaluating the detector noise level.

[0084] Thus, the dark count test allows the evaluation of the noise level of the detector under no light conditions, which is critical for testing the performance of the detector. By measuring the dark count rate, the system design can be optimized to reduce noise and improve the signal-to-noise ratio. The dark count test provides a method to calibrate the detector array to ensure accuracy in practical applications. The measurement of the dark count rate helps to analyze and compare the performance of different detectors. By testing in a dark room, the interference of external light sources can be controlled to ensure the accuracy of the test results. The statistics and analysis of the pulse signal by the control module provide a reliable method to determine the dark count rate.

[0085] In some embodiments, when the test and calibration system is in a light counting rate test state or a post-pulse probability test state, the single photon source in the optical path device is in an on state; wherein the light counting rate is generated in the following manner: the detector array to be tested receives one or more photons in the detection gate, and the signal extraction and identification transmits the obtained pulse signal to the control module using the edge latching method; the control module counts the number of pulses of the counting pulse to obtain the light count, and generates the light counting rate based on the light count; wherein the post-pulse probability is generated in the following manner: the detector array to be tested receives one or more photons in the detection gate, and the signal extraction and identification transmits the obtained pulse signal to the control module using the double gating method; the control module counts the number of pulses of the counting pulse to obtain the post-pulse number, and generates the post-pulse probability based on the post-pulse number.

[0086] Photocount rate test state, a test state in which the single photon source is turned on and emits photons to the detector array to measure the frequency of the detector array's response to the optical signal.

[0087] The afterpulse probability test state is a specific test state used to measure the probability of the detector generating an additional pulse after receiving a photon, which is usually related to the afterpulse effect of the detector.

[0088] The on state means that the single photon source works during the light count rate test or the afterpulse probability test to generate photons.

[0089] The detector array under test refers to the detector array under test, which will respond to photon signals and generate electrical pulses.

[0090] Detection gate: A time window defined in the test during which the detector array responds to photon signals only.

[0091] Signal extraction and identification is responsible for receiving signals from the detector array and extracting and identifying useful pulse signals from them.

[0092] The edge latching method uses the edge of the signal (such as the rising edge or the falling edge) to trigger the latch, thereby capturing and transmitting the pulse signal.

[0093] The double-gating method uses two time gates to determine whether the pulse signal is within a specific time window and is often used to measure the afterpulse probability.

[0094] Light count, the number of photons received by the detector array within the detection gate.

[0095] The light count rate, the number of light counts per unit time, is an important parameter for evaluating the frequency of the detector array's response to light signals.

[0096] Post-pulse count is the number of extra pulses generated after a photon is received by the detector array within the detection gate.

[0097] Afterpulse probability, the ratio of the number of afterpulses to the total light counts, is used to evaluate the afterpulse effect of the detector.

[0098] Therefore, by controlling the opening and closing of the single photon source, dark counts and light counts can be measured respectively, so as to more accurately evaluate the performance of the detector. Light count rate and afterpulse probability are key parameters for evaluating detector performance, which help to understand the sensitivity and reliability of the detector. The edge latch method and double gating method provide effective signal processing technology to ensure that only qualified signals are counted.

[0099] Please refer to Figure 2 The visible near-infrared detector array test and calibration system may include a high-voltage bias circuit (1), an optical focusing module (2), an APD array scanning module (3), a signal extraction and identification module (4), a single-photon source module (5), an FPGA control module (6), a human-computer interaction interface (7), and a TEC cooling module.

[0100] The optical focusing module (2) system adopts a coaxial optical path, and the 1550nm irradiation laser and the visible light observed by the CCD are focused on the APD array (3) to be measured by the same microscope lens. In the system, the optical focusing module (2) system adopts a coaxial optical path, and the 1550nm irradiation laser and the visible light observed by the CCD are focused on the APD array (3) to be measured by the same microscope lens. The visible near-infrared single-photon detector SPAD to be measured is installed on an XYZ three-dimensional translation stage, which can be positioned in the XY direction and focused in the Z direction, and the adjustment accuracy can reach 1μm. There is an aperture stop that can be translated in the XY direction on the middle optical path of the 1550nm laser, and the size of the aperture stop is smaller than the entrance of the microscope lens. During the translation of the aperture stop, the incident angle of the laser incident on the APD array (3) also changes accordingly, and the position of the light spot remains unchanged.

[0101] The APD array scanning module (3) can realize a fully parallel array integration method for integrating multiple APD pixels. The data of a pixel at a certain address is selected by a row and column decoder and output to the on-chip bus. The on-chip controller sequentially traverses the pixel addresses of the entire array and uploads the entire frame of data through the off-chip bus. The bus bandwidth limits the read frame rate to a certain extent. The UART bus implementation method is selected, which mainly consists of a sending module Trasmitter, a receiving module Receiver, a receiving FIFO with a depth of 16, a sending FIFO with a depth of 16, a register list and a status control interrupt register module. Facing the array circuit is a register list (Reg File). The data read out by the array is stored in the corresponding position in the list and then uploaded through Trasmitter. The identification voltage, frame rate, gate setting and other parameters are set for the chip through the human-computer interaction interface (7) via UART.

[0102] The high-voltage bias circuit (1) is connected to the APD array (3) to provide a high-voltage bias. Its function is to realize voltage conversion, convert the input voltage into a DC voltage and output it to the APD array (3), ensuring that the bias voltage provided is stably below the avalanche voltage of the APD array (3); the high-voltage bias circuit (1) can be a DC-DC conversion circuit or an AC-DC conversion circuit.

[0103] The FPGA control module (6) generates a periodic narrow gate pulse which is coupled to the APD array (3) to drive the detector. At the same time, the FPGA control module (6) generates another synchronous pulse signal which passes through the single photon source module (5) to 0.1 single photons per pulse and is coupled to the photosensitive surface of the APD array (3) through an optical fiber.

[0104] The signal extraction and identification module (4) obtains the signal after the APD array scan (3) by amplifying the sampled signal through a high-speed amplifier, and connects the amplified signal to an ECL high-speed comparator with adjustable identification voltage for comparison and identification, and then connects it to the FPGA control module (6) for reading and counting. The extraction and identification module (4) uses a passive quenching method to make SPADs work in a gated Geiger mode. The avalanche signal generated in the gated state with incident photons is first sampled through a 50Ω resistor, and the sampled signal is amplified through a high-speed amplifier. The amplified signal is connected to an ECL high-speed comparator with an adjustable identification voltage for comparison and identification, thereby outputting a pure avalanche signal corresponding to the occurrence of avalanche. Due to the junction capacitance effect of the SPADs pn junction, when a periodic gate pulse is loaded to both ends of the SPADs, a capacitive spike response is generated, resulting in an erroneous count. The avalanche signal will also be superimposed on this capacitive spike response noise signal, resulting in difficulty in extracting the avalanche signal. Therefore, an edge latching method is adopted, by aligning the latching edge with the avalanche signal, when a photon is incident, an avalanche occurs, and the high level obtained by comparing the generated avalanche signal with the comparator will be latched, and then this high level is connected to the FPGA control module (6) for reading and counting.

[0105] The FPGA control module (6) is connected to the human-machine interface (7). The pulse width and repetition frequency of the gated signal generated by the FPGA control module (6) can be modified through the human-machine interface (7), and the dark count, light count, after-pulse and other data processed and obtained by the FPGA control module (6) are sent to the human-machine interface (7) for display. The FPGA control module (6) generates a series of corresponding gated signals through the digital clock management of the FPGA. All units inside the module are synchronously driven by the same gated signal or a gated signal with a certain phase difference therewith. In order to avoid the spike pulse noise generated when the gated pulse is loaded on the SPADs and cause miscounting, it is necessary to provide a latch pulse to the ECL comparator in the signal extraction and identification module (4) when extracting the avalanche signal, and finely adjust its latch edge to align with the center of the avalanche signal through IO DELAY, and its high level is maintained until the rising edge of the next gated pulse signal of the FPGA, so as to avoid the error of the establishment and holding time when the counting module inside the FPGA counts. The pulse signal LaserDriver of the synchronous laser is divided by the DCM clock drive and is adjustable within the full gated pulse cycle. When the avalanche level is detected, the HOLDOFF dead time is set to keep the gate pulse signal at a low level. The dead time is adjustable in the range of 9ns to 1009ns with a step of 10ns.

[0106] In this embodiment, since there are many models of FPGA control module, high-voltage bias circuit, single-photon source module and TEC refrigeration equipment to choose from, the specific implementation method involved in this embodiment uses PicoQuant's PDL 800-B synchronous laser, EXFO's FVA-3150 variable attenuator as the single-photon source module, Xilinx's Virtex 5 series FPGA, ITECH's IT6834 high-voltage bias power supply and Linear Technology's LTC1923TEC controller to illustrate the example effect. Laser driver PDL 800-B is a single-channel dual-mode driver for LDH series and LDH-FA series picosecond pulse laser heads (375-1990nm) and PLS series sub-nanosecond pulse LEDs (255-600nm). The wavelength can be changed by connecting different laser or LED heads. The internal oscillator has two user-selectable base frequencies, 80MHz and 1MHz, and can also be controlled by an external trigger signal. The maximum laser pulse is 10MHz; variable attenuator FVA-3150 has three attenuation modes to choose from, absolute mode (including insertion loss), relative mode (relative to a reference value of 0.00dB) or X+B mode (relative to the display of any selected reference value); high-voltage bias power supply IT6834 has a resolution of 10mV / 10mA, an accuracy of less than 0.1%+38mV / 0.1%+15mA, and supports RS232 / GPIB / USB communication interfaces; LTC1923 The TEC controller integrates all necessary control circuits and two sets of complementary output drivers to drive a full bridge, providing an effective method to deliver bidirectional current to the TEC, enabling an accurate temperature control loop to stabilize the temperature of the laser diode system with 0.1°C accuracy.

[0107] The light spot is focused onto the photosensitive surface of the APD array through optical focusing and a three-dimensional adjustable optical displacement platform; a DC high-voltage power supply provides the APD array with a stable bias high voltage VP that is lower than the breakdown voltage VBR; the FPGA generates a gate signal Vpulse with a pulse width of 9ns, a repetition frequency of 100KHz, and a gate amplitude of 3.3V, which is coupled to the APD array. The N-pole voltage of the APD array rapidly increases to a level several tens of volts higher than the breakdown voltage VBR, and the APD enters the Geiger mode working state. At the same time, the FPGA system synchronously triggers the laser, and after the emitted pulse laser is attenuated to 0.1 photons per pulse, it is irradiated onto the APD photosensitive surface to generate an avalanche signal; when the gate pulse becomes a low level, the APD N-pole voltage rapidly returns to a voltage VP that is lower than the breakdown voltage VBR, which plays a quenching role.

[0108] Due to the capacitive effect of APD, when periodic gate pulses are loaded to both ends of APD, a capacitive spike response will be generated, resulting in erroneous counts; the avalanche signal will also be superimposed on this capacitive spike response noise signal, making it difficult to extract the avalanche signal. The system adopts an edge latching method, which aligns the latch edge with the avalanche signal. When a photon is incident, an avalanche occurs, and the generated avalanche signal is compared by the comparator to obtain a high level that will be latched, and then this high level is connected to the FPGA for reading and counting.

[0109] The number of pulse trains generated each time the gated signal is set through the human-computer interaction interface. When the APD array is not lighted, the dark count can be obtained. If the APD array receives photons in the detection gate, the light count and the number of post-pulses can be obtained. The human-computer interaction interface can set the gated pulse width, gated pulse repetition frequency, and number of gated pulse trains through FPGA, and process and display the test results such as dark count, light count, and post-pulse, so as to realize the performance calibration of the APD array.

[0110] The human-machine interaction interface (7) in the system can adjust and set parameters related to the SPAD, communicate with the FPGA control module (6) via USB, and feed back the count value in the FPGA to the human-machine interaction interface (7) for display and storage.

[0111] In the system, TEC cooling is achieved through a TEC controller to control the APD array with an accuracy of 0.1°C, and can adapt to different types of semiconductor cooling chips with different operating voltages of 5-12V and a maximum of 6A.

[0112] The above description is only a preferred embodiment of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of disclosure involved in the present disclosure is not limited to the technical solutions formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosed concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present disclosure (but not limited to) by each other to form a technical solution.

[0113] In addition, although each operation is described in a specific order, this should not be understood as requiring these operations to be performed in the specific order shown or in a sequential order. Under certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although some specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the present disclosure. Some features described in the context of a separate embodiment can also be implemented in a single embodiment in combination. On the contrary, the various features described in the context of a single embodiment can also be implemented in multiple embodiments individually or in any suitable sub-combination mode.

[0114] Although the subject matter has been described in language specific to structural features and / or methodological logical actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. On the contrary, the specific features and actions described above are merely example forms of implementing the claims.

[0115] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0116] The above description is only a preferred embodiment of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of disclosure involved in the present disclosure is not limited to the technical solutions formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above disclosed concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present disclosure (but not limited to) by each other to form a technical solution.

[0117] In addition, although each operation is described in a specific order, this should not be understood as requiring these operations to be performed in the specific order shown or in a sequential order. Under certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although some specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the present disclosure. Some features described in the context of a separate embodiment can also be implemented in a single embodiment in combination. On the contrary, the various features described in the context of a single embodiment can also be implemented in multiple embodiments individually or in any suitable sub-combination mode.

[0118] Although the subject matter has been described in language specific to structural features and / or methodological logical actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. On the contrary, the specific features and actions described above are merely example forms of implementing the claims.

[0119] The above description is only an embodiment of the present application and is not intended to limit the protection scope of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An optical path device for a detector array test and calibration system, characterized in that: include: A single photon source module for generating near-infrared photons; A visible light generating module, used for generating visible light; An optical focusing module, using a coaxial optical path, is used to focus the photons output by the single-photon source module and the visible light output by the visible light generation module onto the photosensitive surface of the detector array to be tested; Among them, the test and calibration system includes: a high-voltage bias circuit, which is used to provide high-voltage bias to the detector array to be tested; an array scanning module, which is used to scan the detectors in the detector array to be tested and output electrical signals; an array fixing module, which is used to fix the detector array to be tested; and a control module, which is used to generate performance parameters of the detector array to be tested based on the electrical signals.

2. The optical path device according to claim 1, characterized in that: The single-photon source module is used to output a pulsed single-photon source, and the output laser pulse is attenuated to 0.1 photons per pulse through an adjustable attenuator.

3. The optical path device according to claim 1, characterized in that: The optical focusing module comprises a microscope, which is positioned along the XY direction and focused along the Z direction, with an adjustment accuracy of 1 μm.

4. The optical path device according to claim 3, characterized in that: It also includes an aperture diaphragm, which can be translated along the XY direction, and the size of the aperture diaphragm is smaller than the entrance pupil of the microscope lens; In the process of translating the aperture stop, the incident angle of the laser incident on the detector array to be measured also changes.

5. The optical path device according to claim 1, characterized in that: The optical focusing module includes the first beam splitter prism and the second beam splitter prism; Wherein, the first beam splitter prism is arranged between the aperture stop and the optical focusing module, and is used to guide the laser photons or visible light to the optical focusing module; The second beam splitter prism is arranged to guide the visible light to the first beam splitter prism.

6. The optical path device according to claim 1, characterized in that: Also includes CCD; Near-infrared photons and visible light observed by the CCD are focused onto the detector array to be measured by the same microscope lens.

7. The optical path device according to claim 6, characterized in that: The CCD and illumination LED are used to focus the light source on the photosensitive surface of the array to be tested before testing.

8. The optical path device according to claim 1, characterized in that: The single photon source module receives a synchronization signal sent by a control circuit; The control module generates two synchronization signals; the first synchronization signal couples the periodic narrow gate pulse to the detector array to be tested to drive the detector array to be tested; The second synchronization signal is synchronized to the single-photon source module so that the narrow gated pulse is aligned with the optical signal generated by the single-photon source module.

9. The optical path device according to claim 1, characterized in that: When the test and calibration system is in a dark count test state, the single photon source in the optical path device is in a closed state; The dark count rate is generated in the following manner: when the detector array to be tested is in a dark room and no light is added, the signal extraction and identification module transmits the obtained pulse signal to the control module; the control module counts the number of pulses of the counting pulse to obtain the dark count, and generates the dark count rate based on the dark count.

10. The optical path device according to claim 1, characterized in that: When the test and calibration system is in a light count rate test state or a post-pulse probability test state, the single photon source in the optical path device is in an on state; The light counting rate is generated in the following manner: the detector array to be tested receives one or more photons in the detection gate, and the signal extraction and identification transmits the obtained pulse signal to the control module by edge latching; the control module counts the number of pulses of the counting pulse to obtain the light count, and generates the light counting rate based on the light count; Among them, the post-pulse probability is generated in the following way: the detector array to be tested receives one or more photons in the detection gate, and the signal extraction and identification uses the double gating method to transmit the obtained pulse signal to the control module; the control module counts the number of pulses of the counting pulse to obtain the number of post-pulses, and generates the post-pulse probability based on the number of post-pulses.

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