High-throughput photon-counting lidar imaging apparatus and methods

Abstract

This invention discloses a high-throughput photon-counting lidar imaging device and method. The device includes a beam transceiver module, a scanning module, a control module, a detection module, and a data processing module. The control module controls the scanning module to change the direction of the pulsed laser output to achieve target scanning. The detection module includes a single-photon detector and a time-correlated single-photon counting acquisition unit. A synchronization signal acquisition channel is connected to the pulsed laser to acquire the pulsed laser synchronization signal. This invention introduces a single-photon detector with photon number resolution, enabling simultaneous detection of multiple echo photons and simultaneous response to different photon counts. This invention effectively solves the limitations of traditional photon-counting lidars due to low-throughput and weak-light operating conditions, effectively improves the acquisition efficiency of echo photon information under high-throughput conditions, greatly reduces pulse accumulation time, and can achieve higher dynamic range and faster target detection.

Description

Technical Field

[0001] This invention relates to the field of lidar technology, and in particular to a high-throughput photon counting lidar imaging device and method. Background Technology

[0002] With the development of single-photon detection technology, detectors with single-photon sensitivity have become increasingly sophisticated. Compared with traditional linear detectors, they have significant advantages such as high sensitivity, high time resolution, and low power consumption. However, they are still unable to meet the growing requirements for accuracy and speed.

[0003] In single-photon 3D imaging technology, photon-counting lidar technology is widely used. It can acquire 3D images of target scenes with single-photon sensitivity and picosecond-level time resolution, and therefore has been increasingly widely used in satellite mapping, maritime target imaging, weapon guidance, and aerospace. However, the inherent defects of general single-photon detectors are: (1) long dead time; (2) lack of photon number resolution capability. The above defects will cause the loss of photon counting time, and the acquired signal will be distorted relative to the real signal. This drawback becomes more and more obvious as the incident light flux increases. Therefore, traditional photon-counting lidar is limited by the working mechanism of single-photon detectors and is usually limited to low-flux weak light working conditions that meet the "5% criterion", that is, the total number of photon counts of the system must be less than 5% of the total number of periodic laser pulses. However, this condition requires a large amount of pulse accumulation, which seriously restricts the information acquisition efficiency. In order to overcome this limitation, the concept of high-flux photon-counting lidar was born, whose incident light flux is much greater than the "5% criterion". Under high-throughput conditions, many issues, such as the role model of dead time, the operating characteristics of the system, and information sensing algorithms, are quite different from those under low-throughput and low-light conditions.

[0004] Currently, there are more and more new single-photon detectors, which have unique advantages over ordinary single-photon detectors, such as photon number resolution, low dead time and high dynamic range. Therefore, it is necessary to carry out in-depth research on photon counting lidar systems based on new single-photon detectors under high-throughput conditions. Summary of the Invention

[0005] This invention provides a high-throughput photon counting lidar imaging device and method. The imaging device achieves simultaneous detection of at least two different echo photons through a detection module, which improves the acquisition efficiency of echo signals, reduces the influence of background photons in lidar imaging, improves the signal-to-noise ratio and detection speed, enables rapid three-dimensional detection of moving targets, and is more conducive to real-time detection of weak targets in extreme scenarios.

[0006] According to one aspect of the present invention, a high-throughput photon counting lidar imaging device is provided, specifically including a beam transceiver module, a scanning module, a control module, a detection module, and a data processing module;

[0007] The beam transceiver module includes a pulsed laser and a beam adjustment unit. The pulsed laser output from the pulsed laser is transmitted to the target under test after passing through the beam adjustment unit and the scanning module. The echo beam returned from the target under test is transmitted to the detection module after passing through the beam adjustment unit and the scanning module.

[0008] The control module is connected to the scanning module. The control module is used to control the scanning module to change the direction of the pulsed laser output in order to scan the target under test.

[0009] The detection module includes a single-photon detector and a time-correlated single-photon counting acquisition unit. The single-photon detector has photon number resolution capability and is used to simultaneously detect at least two different echo photons. The time-correlated single-photon counting acquisition unit includes a synchronization signal acquisition channel and a photon number acquisition channel. The synchronization signal acquisition channel is connected to a pulsed laser and is used to acquire the synchronization signal of the pulsed laser. The photon number acquisition channel is connected to the single-photon detector and is used to acquire detection signals with at least two different photon number responses.

[0010] The data processing module is connected to the time-correlated single-photon counting acquisition unit and is used to image the target under test based on the synchronization signal and the detection signal.

[0011] Optionally, the beam adjustment unit includes a perforated mirror, a transceiver assembly, and a filter;

[0012] The pulsed laser beam is transmitted through the perforated mirror to the scanning module, modulated by the scanning module, and then transmitted to the transceiver group for emission. The echo beam returned by the target is received by the transceiver group, reflected by the scanning module and the perforated mirror, and then transmitted to the single-photon detector after passing through the filter.

[0013] Optionally, the center of the perforated mirror is offset from the center of the mirror.

[0014] Optionally, the beam adjustment unit may also include a collimating lens group and a converging lens group;

[0015] The collimating lens group is located between the pulsed laser and the perforated mirror. The collimating lens group includes at least one collimating lens. After being collimated by the collimating lens group, the pulsed laser is transmitted to the perforation of the perforated mirror.

[0016] The converging mirror assembly is located between the perforated mirror and the single-photon detector. The echo beam reflected by the perforated mirror is converged by the converging mirror assembly and then transmitted to the single-photon detector.

[0017] Optionally, the transceiver assembly includes a first lens and a second lens, which together form a telescope structure.

[0018] Anti-reflective coatings are provided on the surfaces of the first and second lenses.

[0019] Optionally, the beam adjustment unit also includes a dichroic mirror located between the perforated mirror and the single-photon detector;

[0020] The high-throughput photon counting lidar imaging device also includes a monitoring module, which is used to receive a portion of the beam output by the dichroic mirror.

[0021] Optionally, the single-photon detector includes a tandem superconducting nanowire single-photon detector;

[0022] The tandem superconducting nanowire single-photon detector consists of multiple sets of superconducting nanowires, each set of which is connected in parallel with a resistor, and the multiple sets of superconducting nanowires are connected in series.

[0023] Optionally, the detection module also includes a signal amplifier connected between the single-photon detector and the time-correlated single-photon counting acquisition unit.

[0024] Optionally, the scanning module includes a dual-axis orthogonal scanning galvanometer;

[0025] Optionally, high throughput satisfies the following condition: the total number of photon counts of the high-throughput photon counting lidar imaging device is greater than 5% of the total number of periodic laser pulses.

[0026] According to another aspect of the present invention, a high-throughput photon counting lidar imaging method is provided, applicable to any of the aforementioned high-throughput photon counting lidar imaging devices. The high-throughput photon counting lidar imaging method includes:

[0027] The pulsed laser emits pulsed laser light, which is then incident on the target after passing through the beam adjustment unit and the scanning module. The echo beam returned from the target is then transmitted to the detection module after passing through the beam adjustment unit and the scanning module.

[0028] A single-photon detector receives the echo beam, and a time-correlated single-photon counting acquisition unit acquires the synchronization signal of the pulsed laser and the detection signals of at least two different photon number responses.

[0029] The control module controls the scanning module to change the direction of the pulsed laser output in order to scan the target under test. The time-correlated single-photon counting acquisition unit acquires the synchronization signal of all pulsed lasers and the detection signal of at least two different photon number responses during the scanning process.

[0030] The data processing module images the target under test based on the synchronization signal and the detection signal.

[0031] The high-throughput photon counting lidar imaging device and method provided in this invention specifically include a beam transceiver module, a scanning module, a control module, a detection module, and a data processing module. The beam transceiver module includes a pulsed laser and a beam adjustment unit. The pulsed laser output from the pulsed laser is transmitted to the target after passing through the beam adjustment unit and the scanning module. The echo beam returned from the target is transmitted to the detection module after passing through the beam adjustment unit and the scanning module. The control module is connected to the scanning module and is used to control the scanning module to change the direction of the pulsed laser output to achieve scanning of the target. The detection module includes... The invention includes a single-photon detector and a time-correlated single-photon counting acquisition unit. The single-photon detector has photon number resolution capability, enabling simultaneous detection of at least two different echo photons. The time-correlated single-photon counting acquisition unit includes a synchronization signal acquisition channel and a photon number acquisition channel. The synchronization signal acquisition channel is connected to a pulsed laser to acquire the synchronization signal of the pulsed laser. The photon number acquisition channel is connected to the single-photon detector to acquire detection signals with at least two different photon number responses. A data processing module is connected to the time-correlated single-photon counting acquisition unit and is used to image the target under test based on the synchronization signal and the detection signal. This embodiment of the invention can improve the acquisition efficiency of echo signals, reduce the influence of background photons in lidar imaging, greatly reduce pulse accumulation time, improve signal-to-noise ratio and detection speed, and enable rapid three-dimensional detection of moving targets. It is more conducive to real-time detection of weak targets in extreme scenarios and is beneficial for building a high dynamic range, high sensitivity, high signal-to-noise ratio, and real-time three-dimensional imaging system.

[0032] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the structure of a high-throughput photon counting lidar imaging device provided in an embodiment of the present invention;

[0035] Figure 2 This is a schematic diagram of a high-throughput photon counting lidar imaging device provided in an embodiment of the present invention;

[0036] Figure 3This is a schematic diagram of another high-throughput photon counting lidar imaging device provided in an embodiment of the present invention;

[0037] Figure 4 This is a flowchart of a high-throughput photon counting lidar imaging method provided in an embodiment of the present invention;

[0038] Figure 5 This is a flowchart of another high-throughput photon counting lidar imaging method provided in an embodiment of the present invention. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0040] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0041] The present invention provides a high-throughput photon counting lidar imaging device and method to solve the above problems, improve the acquisition efficiency of echo signals, greatly reduce pulse accumulation time, and achieve rapid target detection.

[0042] Figure 1 This is a schematic diagram of the structure of a high-throughput photon counting lidar imaging device provided in an embodiment of the present invention. (Refer to...) Figure 1 The present invention provides a high-throughput photon counting lidar imaging device, specifically including a beam transceiver module 10, a scanning module 20, a control module 30, a detection module 40 and a data processing module 50;

[0043] The beam transceiver module 10 includes a pulsed laser 11 and a beam adjustment unit 12. The pulsed laser output from the pulsed laser 11 is transmitted to the target under test after passing through the beam adjustment unit 12 and the scanning module 20. Figure 1 (not shown), the echo beam returned by the target under test is transmitted to the detection module 40 after passing through the beam adjustment unit 12 and the scanning module 20;

[0044] The control module 30 is connected to the scanning module 20. The control module 30 is used to control the scanning module 20 to change the direction of the pulsed laser output in order to achieve scanning of the target under test.

[0045] The detection module 40 includes a single-photon detector 41 and a time-correlated single-photon counting acquisition unit 42. The single-photon detector 41 has photon number resolution capability, used to simultaneously detect at least two different echo photons. The time-correlated single-photon counting acquisition unit 42 includes a synchronization signal acquisition channel 421 and a photon number acquisition channel 422. The synchronization signal acquisition channel 421 is connected to the pulsed laser 11 and is used to acquire the synchronization signal of the pulsed laser. The photon number acquisition channel 422 is connected to the single-photon detector 41 and is used to acquire detection signals with at least two different photon number responses. The photon number acquisition channel 422 includes at least two photon number acquisition sub-channels. Figure 1 (Not shown), used to collect detection signals with different photon number responses.

[0046] The data processing module 50 is connected to the time-correlated single-photon counting acquisition unit 42 and is used to image the target under test based on the synchronization signal and the detection signal.

[0047] The imaging device provided in this embodiment is suitable for imaging under high-throughput conditions. The incident light flux received by the optical path must be greater than the "5% criterion," meaning that high throughput satisfies the following: the total number of photon counts in the high-throughput photon-counting lidar imaging device must be greater than 5% of the total number of periodic laser pulses, breaking through the low-throughput, weak-light operation limitation of traditional photon-counting lidar. Moreover, when the incident light flux received by the optical path is too high, the receiving and receiving optical paths do not require additional attenuation, which can greatly reduce the pulse accumulation time and improve information acquisition efficiency. The scanning module 20 can be controlled by the control module 30 to adjust the position of the beam to expand the scannable area and change the scanning position; the single-photon detector 41 can be a single-photon detector with photon number resolution capability; the data processing module 50 includes, but is not limited to, analyzing the incident light flux of the single-photon detector to determine the detection performance, and can image and output the target under test using hardware and / or software methods based on the synchronization signal and the detection signal. It is worth noting that the photon number acquisition channel 422 can acquire at least two photon corresponding signals at one time for the data processing module 50 to analyze and image the target under test, thereby improving the acquisition efficiency of the echo signal, greatly reducing the pulse accumulation time, and realizing rapid target detection.

[0048] Understandably, the adjustable pulsed laser output from the pulsed laser 11 is transmitted to the target under test after passing through the beam adjustment unit 12 and the scanning module 20. The echo beam returned from the target under test is transmitted to the detection module 40 after passing through the beam adjustment unit 12 and the scanning module 20. The position of the beam can be adjusted by the control module 30 to expand the scannable area and change the scanning position. The echo beam is received by the single-photon detector 41, and at least two detection signals with different photon number responses are collected by the photon number acquisition channel 422 in the time-correlated single-photon counting acquisition unit 42. At the same time, the corresponding synchronization signal in the pulsed laser 11 is collected by the synchronization signal acquisition channel 421. The collected detection signal and synchronization signal are transmitted to the data processing module 50 for analysis and imaging of the target under test.

[0049] The high-throughput photon-counting lidar imaging device provided in this invention includes a beam transceiver module, a scanning module, a control module, a detection module, and a data processing module. The beam transceiver module includes a pulsed laser and a beam adjustment unit. The pulsed laser output from the pulsed laser is transmitted to the target after passing through the beam adjustment unit and the scanning module. The echo beam returned from the target is transmitted to the detection module after passing through the beam adjustment unit and the scanning module. The control module is connected to the scanning module and controls the scanning module to change the direction of the pulsed laser output to achieve scanning of the target. The detection module includes a single-photon detector and a time-correlated single-photon counting acquisition unit. The single-photon detector has photon number resolution capability, used to realize at least two different echo beams. The simultaneous detection of photons is achieved through a time-correlated single-photon counting acquisition unit, which includes a synchronization signal acquisition channel and a photon number acquisition channel. The synchronization signal acquisition channel is connected to a pulsed laser to acquire the synchronization signal of the pulsed laser, while the photon number acquisition channel is connected to a single-photon detector to acquire detection signals with at least two different photon number responses. A data processing module is connected to the time-correlated single-photon counting acquisition unit and is used to image the target based on the synchronization and detection signals. The control module adjusts the beam position to make the scannable area and scanning position adjustable. By acquiring at least two detection signals with different photon number responses through the photon number acquisition channel in the time-correlated single-photon counting acquisition unit, the acquisition efficiency of the echo signal is improved, the pulse accumulation time is greatly reduced, and rapid target detection is achieved. This invention introduces a single-photon detector with photon number resolution, enabling simultaneous detection of multiple echo photons and simultaneous responses with different photon numbers. The embodiments of the present invention effectively solve the limitations of traditional photon counting lidar under low-throughput and weak-light operating conditions, effectively improve the acquisition efficiency of echo photon information under high-throughput conditions, greatly reduce pulse accumulation time, and can achieve higher dynamic range and faster target detection.

[0050] Figure 2 This is a schematic diagram of a high-throughput photon counting lidar imaging device provided in an embodiment of the present invention. (Refer to...) Figure 2 Based on the apparatus provided in the previous embodiment, the embodiments of the present invention are further refined. Optionally, the beam adjustment unit includes a perforated reflector 121, a transceiver lens group 122, and a filter 123;

[0051] The center of the perforation in the perforated mirror 121 is offset from the center of the mirror. Since the received beam is a Gaussian beam with the highest energy at the center, this offset design allows the energy of the echo signal to be coupled to the detection module, resulting in high receiving efficiency. The pulsed laser is transmitted through the perforation of the perforated mirror 121 to the scanning module 20, modulated by the scanning module 20, and then transmitted to the transceiver group 122 for emission. The echo beam returned by the target is received by the transceiver group 122, reflected by the scanning module 20 and the perforated mirror 121, and then transmitted to the single-photon detector 41 after passing through the filter 123. The perforation in the perforated mirror 121 is generally set as a circular hole.

[0052] In this embodiment, the pulsed laser emitted by the pulsed laser 11 passes through the perforation of the perforated mirror 121 to the scanning module 20, and is then modulated by the scanning module 20 and transmitted to the transceiver assembly 122 for emission. The echo beam from the scanning module 20 is reflected by the perforated mirror 121 and received by the single-photon detector 41. The transceiver assembly 122 can be a combination of multiple convex lenses, or a combination of a convex lens and a corresponding concave lens, or other optical devices that can adjust the optical path. This embodiment of the invention is not limited to any particular type, and the design can be tailored to the specific implementation. The filter 123 filters the beam received by the single-photon detector 41.

[0053] It is understandable that the echo beam is generally a Gaussian beam with the highest energy content at the center. The energy in the central region needs to be utilized and reflected as much as possible onto the single-photon detector 41 to improve the optical path receiving efficiency. Since the emitted beam does not need to occupy the entire aperture, the perforated mirror 121 should have an opening on the central side. The pulsed laser output from the pulsed laser 11 passes through the perforated mirror 121 for transmission, the scanning module 20 for reflection, and the transceiver mirror group 122 for transmission. This light transmission path can be designed as a single-station optical path (i.e., coaxial light transmission path, also called a coaxial optical path) to optimize the light transmission path to the target under test. The echo beam returned from the target under test is transmitted through the transceiver mirror group 122, reflected by the scanning module 20 and the perforated mirror 121, and then transmitted to the detection module 40. The position of the beam can be adjusted by the control module 30 to expand the scannable area and change the scanning position. The designed monostatic optical path optimizes the light transmission path. It can also be designed as a bistatic optical path using other components. The bistatic optical path does not require a perforated mirror, and the transceiver group includes a transmitting mirror group and a receiving mirror group. The echo beam is received by a single-photon detector 41, and at least two detection signals with different photon number responses are collected through the photon number acquisition channel in the time-correlated single-photon counting acquisition unit 42. Simultaneously, the corresponding synchronization signal from the pulsed laser 11 is acquired through the synchronization signal acquisition channel. The acquired detection and synchronization signals are then analyzed to image the target. Acquiring at least two detection signals with different photon number responses through the photon number acquisition channel in the time-correlated single-photon counting acquisition unit improves the acquisition efficiency of the echo signal, significantly reduces pulse accumulation time, and achieves rapid target detection. It is worth noting that compared to the bistatic optical path mode, this monostatic optical path's dynamic narrow field-of-view design can greatly reduce background noise. Furthermore, the monostatic mode makes the system structure more compact and smaller, and easier to aim at targets at different distances.

[0054] Figure 3 This is a schematic diagram of another high-throughput photon counting lidar imaging device provided in an embodiment of the present invention, with reference to... Figure 3 Based on the apparatus provided in the previous embodiment, the embodiments of the present invention are further refined. Optionally, the beam adjustment unit further includes a collimating lens group 124 and a converging lens group 125;

[0055] The collimating lens group 124 is located between the pulsed laser 11 and the reflector 121. The collimating lens group 124 includes at least one collimating lens. After being collimated by the collimating lens group 124, the pulsed laser is transmitted to the perforation of the perforated reflector 121.

[0056] The converging mirror group 125 is located between the perforated mirror 121 and the single-photon detector 41. The echo beam reflected by the perforated mirror 121 is converged by the converging mirror group 125 and then transmitted to the single-photon detector 41.

[0057] The order in which the beam of the target echo passes through the filter 123 and the converging lens group 125, and their relative positions, are not limited here. The collimating lens group 124 and the converging lens group 125 enhance the focusing of the beam in the device, thereby improving the stability of the optical path. It is worth noting that the number and type of the collimating lens group 124 and the converging lens group 125 are not limited here; they can be optical devices capable of collimation and focusing, such as convex lenses and related lens groups.

[0058] Understandably, high-throughput photon counting lidar imaging devices with added collimating lens groups and converging lens groups enhance the collimation of the pulsed laser emitted by the pulsed laser through the collimating lens group, and the converging lens group focuses the echo beam reflected by the perforated mirror before transmitting it to the single-photon detector, thus avoiding signal divergence.

[0059] Based on the above embodiments, the device can be optimized as follows:

[0060] Optionally, the transceiver assembly 122 includes a first lens 1221 and a second lens 1222, which together form a telescope structure.

[0061] The transceiver lens group 122 may include a first lens 1221 and a second lens 1222, which may be convex lenses to form a telescope structure. It focuses the pulse signal emitted by the pulse laser 11 to expand the monitoring distance of the target under test, and focuses the received detection signal to facilitate signal collection.

[0062] Optionally, the surfaces of the first lens 1221 and the second lens 1222 are provided with anti-reflective coatings.

[0063] Among them, anti-reflection coatings are provided on the surfaces of the first lens 1221 and the second lens 1222, which can increase the transmittance of the echo beam in the transceiver lens group, reduce the weakening effect of the detection signal intensity, and obtain more detection signals.

[0064] The high-throughput photon counting lidar imaging device provided in this invention optimizes the device structure, specifically the beam transceiver module. An anti-reflection coating is applied to the lens surface of the transceiver lens group in the beam transceiver module to increase the transmittance of the echo beam in the transceiver lens group, reducing the weakening effect on the detection signal intensity and thus acquiring more detection signals. Multiple lenses form a telescope structure, converging and diverging the transmitted and received beams respectively. The designed monostation optical path optimizes the light transmission path, significantly reducing background noise. Furthermore, the monostation mode makes the system structure more compact and smaller, making it easier to aim at targets at different distances, and avoiding the need to change the optical path of shared optical components, which could cause some laser light to enter the single-photon detector along the receiving optical path, affecting the detection of the target echo.

[0065] Continue to refer to Figure 3 Optionally, the beam adjustment unit 12 also includes a high-quality dichroic mirror 126, which is located between the reflector 121 and the single-photon detector 41.

[0066] The high-throughput photon counting lidar imaging device also includes a monitoring module 13, which is used to receive a portion of the beam output by the dichroic mirror 126, the wavelength of which is different from that of the imaging light signal.

[0067] The monitoring module 13 can intuitively determine whether a detection signal has been acquired using optical sensors through both hardware and software methods, thereby quickly determining the detection location. In specific implementations, a converging lens 127 can also be placed between the detection module 13 and the dichroic mirror 126.

[0068] Optionally, the single-photon detector 41 includes a tandem superconducting nanowire single-photon detector;

[0069] The tandem superconducting nanowire single-photon detector consists of multiple sets of superconducting nanowires, each set of which is connected in parallel with a resistor, and the multiple sets of superconducting nanowires are connected in series.

[0070] Among them, superconducting nanowires can be placed in a low-temperature environment to enhance the superconducting effect and avoid the weakening of the detected signal during the transmission process.

[0071] Optionally, the detection module also includes a signal amplifier connected between the single-photon detector and the time-correlated single-photon counting acquisition unit.

[0072] The signal amplifier is positioned between the single-photon detector and the time-correlated single-photon counting acquisition unit. It amplifies the acquired detection signal and transmits it to the time-correlated single-photon counting acquisition unit, where it is analyzed and calculated by software using methods such as noise reduction and error correction algorithms. In practice, the single-photon detector and signal amplifier are placed in a cryogenic thermostat to improve stability; the specific temperature can be set to 1.5K.

[0073] Optionally, the scanning module includes a biaxial orthogonal scanning galvanometer.

[0074] In most cases, the highest deflection angle of the dual-axis orthogonal scanning galvanometer rotating back and forth along the axis at high speed is +12.5° (+10° is often a safer range), and the incident angle should not be deflected to 45°.

[0075] It is understandable that the pulsed laser output from the pulsed laser 11 passes sequentially through the perforation of the perforated reflector 121, the scanning module 20, and the transceiver group 122. The light transmission path can be designed as a single-station optical path to optimize the light transmission path to the target under test. The echo beam returned from the target under test passes through the scanning module 20 and the reflector 121 and is transmitted to the detection module 40. Under the high-speed back-and-forth rotation of the dual-axis orthogonal scanning galvanometer, the position of the beam is adjusted by the control module to expand the scannable area and change the scanning position. The perforated reflector 121 and the transceiver group 122 can be designed as a single-station optical path to optimize the light transmission path, or they can be designed as a dual-station optical path by other components. After the collimating lens group and converging lens group enhance the stability of the optical path, a portion of the beam output by the dichroic mirror 126 and the monitoring module 13 can be received to directly monitor the echo beam. After a large amount of interference is removed by a filter, the echo beam is received by a single-photon detector 41 (such as a tandem superconducting nanowire single-photon detector) under low-temperature conditions. At least two detection signals with different photon number responses are collected by the photon number acquisition channel 422 in the time-correlated single-photon counting acquisition unit 42. Simultaneously, the corresponding synchronization signal from the pulsed laser 11 is acquired by the synchronization signal acquisition channel 421. Based on the analysis of the acquired detection and synchronization signals, the target to be measured is imaged. Under high-throughput operating conditions, the single-photon detector can simultaneously detect multiple echo photons. The multi-channel time-correlated single-photon counting acquisition unit collects at least two detection signals with different photon number responses, improving the acquisition efficiency of the echo signal, greatly reducing the pulse accumulation time, and achieving rapid target detection. It is worth noting that, compared with the bistatic optical path mode, this dynamic narrow field-of-view design mode of the monostatic optical path can greatly reduce background noise; in addition, the monostatic mode makes the system structure more compact and smaller, and makes it easier to aim at targets at different distances.

[0076] Figure 4 A flowchart illustrating a high-throughput photon counting lidar imaging method provided in an embodiment of the present invention. (Reference) Figure 4 This imaging method is applicable to any of the above-mentioned high-throughput photon counting lidar imaging devices, and the imaging method includes:

[0077] S110, the pulsed laser emits pulsed laser light, which is transmitted to the target under test after passing through the beam adjustment unit and the scanning module. The echo beam returned by the target under test is transmitted to the detection module after passing through the beam adjustment unit and the scanning module.

[0078] Under high-throughput conditions, the probability of a single-photon detector receiving different numbers of photons varies with the incident light flux; for an incident light pulse with an average photon number of μ, the probability of measuring a photon number of k follows a Poisson distribution:

[0079]

[0080] Where e is the natural constant, in one embodiment, the time-correlated single-photon counting acquisition unit includes six photon number acquisition channels with different photon number responses, enabling the resolution of 1 to 6 photons. The number of photons in the output pulse of a pulsed laser follows a Poisson distribution. For example, when the incident light is weak and the average photon number does not exceed 0.1 photons / pulse, most of the photons in the pulse are single photons. At this time, the detector response is mostly a single-photon response, with a small number of multi-photon responses possible. As the incident light power increases, the probability of the pulse containing multiple photons increases, and the probability of the detector generating a multi-photon response also increases.

[0081] First, the bias current of the single-photon detector is set. By adjusting the attenuation of the laser, incident light of different powers can be obtained. Various photon response signals can be observed under different optical powers. The average photon count of the incident light is set at different photon counts / pulses. Then, the corresponding output pulses are acquired using a high-speed oscilloscope or a time-correlated single-photon counting acquisition unit. The pulse signal waveform acquired by the oscilloscope in fluorescence mode is analyzed to obtain the counting statistics for different pulse amplitudes. Generally, multiple counting amplitude peaks will appear, corresponding to the responses of different photons. Each counting peak can be fitted with a Gaussian distribution to obtain the photon count distribution map under different incident light fluxes. Based on the Gaussian peak of the count rate corresponding to each pulse amplitude, integrating each counting peak yields the count rate corresponding to each response photon count. Alternatively, the readout signal can be directly connected to the counter to directly read the photon response count rate. For example, selecting the midpoint between the (n-1)th and nth peaks as the threshold voltage of the counter defines the count rate for detecting ≥n photons, and then the relationship between the count rate for detecting ≥n photons and different optical powers can be obtained. When the average power of the incident light is below the level of a single photon, the average number of photons μ per pulse is much less than 1. In this case, the counting rate of ≥n photons should be proportional to ημ, where η is the system detection efficiency of the detector.

[0082] It is worth noting that incandescent lamps or other light sources can be placed on the side of the optical path to generate strong background noise. The influence of different incident light fluxes on the photon number distribution can be observed, and then combined with image processing algorithms to suppress background noise and improve the detection performance of the system.

[0083] Unlike traditional lidar signal recording modes based on linear detection, photon counting lidar typically uses the echo photon statistical histogram method to extract signals. Goodman, in his theoretical research on energy-based lidar, discovered that the signal photoelectrons generated by the laser echo from a mirror target follow a Poisson distribution, while those from a rough target follow a negative binomial distribution. In reality, target surfaces are usually diffusely reflective rough surfaces. In this case, assuming the energy of the laser echo incident on the photodetector is W, the unconditional probability that the detector will generate k signal photoelectrons within any given time interval can be given by the formula:

[0084]

[0085] In the formula, p(W) is the probability density function of the incident light energy, and the conditional probability P0 is the probability density function of the incident light energy. S (k|W) follows a Poisson distribution, specifically:

[0086]

[0087] Where v is the photon frequency, h and η D These represent Planck's constant and photon detection efficiency, respectively. Typically, single-photon detectors lack photon number resolution, meaning they can only distinguish between the mutually exclusive states of "light present" and "light absent." For a tandem superconducting nanowire single-photon detector with 6-photon number resolution, given the photon number k, it is necessary to calculate the probabilities of generating exactly 0, 1, 2, 3, 4, 5, and 6 photons, respectively. The appropriate probability can be selected based on the specific implementation requirements.

[0088] S120: A single-photon detector receives the echo beam, and a time-correlated single-photon counting acquisition unit acquires the synchronization signal of the pulsed laser and the detection signals of at least two different photon number responses.

[0089] The detection signals corresponding to at least two different photon number responses can be pre-calibrated and set using hardware and / or software methods.

[0090] S130: The control module controls the scanning module to change the direction of the pulsed laser output in order to achieve scanning of the target under test. The time-correlated single-photon counting acquisition unit acquires the synchronization signal of all pulsed lasers and the detection signal of at least two different photon number responses during the scanning process.

[0091] The control module uses hardware and / or software to adjust the beam adjustment unit and scans the target in sequence.

[0092] S140, the data processing module images the target under test based on the synchronization signal and the detection signal.

[0093] The data processing module performs noise reduction on the synchronization signal and the detection signal using hardware and / or software methods, and then images the detection signals with at least two pre-calibrated different photon number responses.

[0094] Understandably, the bias current of the pulsed laser is first set, and the incident light of different powers is obtained by adjusting the adjustable attenuator. Under different incident light powers, various photon response signals can be collected. Next, the average photon count of the incident light is set at different photon counts / pulses. Then, the corresponding output pulses are collected using a time-correlated single-photon counting module, and the count statistics for different pulse intensities are obtained through analysis. Generally, multiple count intensity peaks will appear, corresponding to different photon responses. Each count peak can be fitted with a Gaussian distribution to obtain a photon count distribution map under different incident light fluxes. Based on the Gaussian peak of the count rate corresponding to each pulse intensity, integrating each count peak yields the count rate corresponding to each response photon count. Repeating the above operation obtains at least two detection signals with different photon count responses. After the data processing module performs noise reduction using hardware and / or software denoising algorithms based on the synchronization signal and detection signal, the corresponding channel is imaged.

[0095] This invention provides a high-throughput photon-counting lidar imaging method. The method involves a pulsed laser emitter transmitting pulsed laser light. The pulsed laser light passes through a beam adjustment unit and a scanning module before being transmitted to the target. The echo beam returned from the target passes through the beam adjustment unit and the scanning module before being transmitted to a detection module. A single-photon detector receives the echo beam. A time-correlated single-photon counting acquisition unit acquires the synchronization signal of the pulsed laser light and detection signals from at least two different photon number responses. A control module controls the scanning module to change the direction of the pulsed laser output to scan the target. The time-correlated single-photon counting acquisition unit acquires the synchronization signal of all pulsed laser light during the scanning process and detection signals from at least two different photon number responses. A data processing module images the target based on the synchronization and detection signals. Utilizing the low dead time and unique photon number resolution advantages of the photon number-resolved single-photon detector, a statistical model of the echo photons under different incident light fluxes is established, thereby formulating an optimal discrimination scheme to improve detection performance under high-throughput conditions. The light scattered from the target is collected through the optical path, and the received echo pulse signal is focused onto the photosensitive surface of the single-photon detector. At least two detection signals with different photon number responses can be obtained in a single operation to improve the acquisition efficiency of the echo signal, greatly reduce the pulse accumulation time, and achieve rapid target detection.

[0096] In addition, the time-correlated single-photon counting module, which extracts photon count information from the echo signal, can calculate the distance between the target transmitter and receiver based on the photon count information obtained from the echo signal analysis using a noise reduction and cancellation algorithm.

[0097] The high-throughput photon counting lidar imaging method provided in the above embodiments is optimized by adding a step after the data processing module images the target based on the synchronization signal and the detection signal. This step involves calculating the distance between the target transmitter and receiver based on the photon count information obtained by the time-correlated single-photon counting module through the analysis of the echo signal and a noise reduction algorithm. Figure 5 A flowchart of another high-throughput photon counting lidar imaging method provided in an embodiment of the present invention is shown below. Figure 5 The specific optimization methods are as follows:

[0098] S210, the pulsed laser emits pulsed laser light, which is transmitted to the target under test after passing through the beam adjustment unit and the scanning module. The echo beam returned by the target under test is transmitted to the detection module after passing through the beam adjustment unit and the scanning module.

[0099] S220: A single-photon detector receives the echo beam, and a time-correlated single-photon counting acquisition unit acquires the synchronization signal of the pulsed laser and the detection signals of at least two different photon number responses.

[0100] S230: The control module controls the scanning module to change the direction of the pulsed laser output in order to scan the target under test. The time-correlated single-photon counting acquisition unit acquires the synchronization signal of all pulsed lasers and the detection signal of at least two different photon number responses during the scanning process.

[0101] S240, the data processing module, images the target under test based on the synchronization signal and the detection signal.

[0102] S250: Based on the photon count information obtained by the time-correlated single-photon counting module through the analysis of the echo signal, the distance between the target transmitter and receiver is calculated using a noise reduction and error elimination algorithm.

[0103] Understandably, the bias current of the pulsed laser is first set, and the incident light of different powers is obtained by adjusting the adjustable attenuator. Under different incident light powers, various photon response signals can be collected. Next, the average photon count of the incident light is set at different photon counts / pulses. Then, the corresponding output pulses are collected using a time-correlated single-photon counting module and connected to a counter to directly read the photon response count rate. For example, selecting the midpoint between the (n-1)th and nth peaks as the threshold voltage of the counter defines the count rate for detecting at least n photons. Then, the relationship between the count rate for detecting at least n photons and different optical powers can be obtained. When the average power of the incident light is below the single-photon level, the average photon count μ per pulse is much less than 1. In this case, the count rate for detecting at least n photons should be proportional to ημ, where η is the system detection efficiency of the detector. Repeating the above operation yields at least two detection signals with different photon count responses. After the data processing module performs noise reduction using hardware and / or software denoising algorithms based on the synchronization signal and the detection signal, the corresponding channel is imaged.

[0104] It is worth noting that incandescent lamps or other light sources can be placed on the side of the optical path to generate strong background noise. The influence of different incident light fluxes on the photon number distribution can be observed, and then image processing algorithms can be combined to suppress background noise and improve the detection performance of the system.

[0105] Optionally, under different parameters, the statistical description of signal photons can be accurately approximated by a Poisson distribution. The Poisson distribution assumption is further calculated, and then combined with the photon statistical model of noise, the improvement of signal-to-noise ratio under high throughput conditions is derived. The peak position (representing distance information), peak size (representing reflectivity information), number of peaks, and noise intensity in the lidar echo signal are estimated by using a Markov chain Monte Carlo stochastic estimation method based on Bayesian inference. The three-dimensional image of the target is then reconstructed by combining it with a single-photon imaging processing algorithm.

[0106] This invention provides a photon-counting lidar imaging method. A pulsed laser emits pulsed laser light, which is transmitted to the target after passing through a beam adjustment unit and a scanning module. The echo beam returned from the target is transmitted to a detection module after passing through the beam adjustment unit and the scanning module. A single-photon detector receives the echo beam. A time-correlated single-photon counting acquisition unit acquires the synchronization signal of the pulsed laser and detection signals with at least two different photon count responses. A control module controls the scanning module to change the direction of the pulsed laser output to scan the target. The time-correlated single-photon counting acquisition unit acquires the synchronization signal of all pulsed lasers during the scanning process and detection signals with at least two different photon count responses. A data processing module images the target based on the synchronization and detection signals. The distance between the target transmitter and receiver is calculated based on the photon count information obtained by the time-correlated single-photon counting module through analysis of the echo signal, using a noise reduction and cancellation algorithm. By connecting single-photon detectors to acquire at least two detection signals with different photon number responses, the acquisition efficiency of echo signals can be improved by obtaining at least two detection signals with different photon number responses in a single operation. This greatly reduces the pulse accumulation time and enables rapid target detection. The echo signals are assumed to have a Poisson distribution, and then combined with a photon statistical model of noise, the peak position (representing distance information), peak size (representing reflectivity information), number of peaks, and noise intensity in the lidar echo signals are estimated. Combined with single-photon imaging processing algorithms, the three-dimensional image of the target is accurately reconstructed.

[0107] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A high-throughput photon counting lidar imaging device, characterized in that, It includes a beam transceiver module, a scanning module, a control module, a detection module, and a data processing module; The beam transceiver module includes a pulsed laser and a beam adjustment unit. The pulsed laser output by the pulsed laser is transmitted to the target under test after passing through the beam adjustment unit and the scanning module. The echo beam returned by the target under test is transmitted to the detection module after passing through the beam adjustment unit and the scanning module. The control module is connected to the scanning module, and the control module is used to control the scanning module to change the direction of the pulsed laser output in order to scan the target under test. The detection module includes a single-photon detector and a time-correlated single-photon counting acquisition unit. The single-photon detector has photon number resolution capability, used to simultaneously detect at least two different echo photons. The time-correlated single-photon counting acquisition unit includes a synchronization signal acquisition channel and a photon number acquisition channel. The synchronization signal acquisition channel is connected to the pulsed laser and is used to acquire the synchronization signal of the pulsed laser. The photon number acquisition channel is connected to the single-photon detector and includes at least two photon number acquisition sub-channels, respectively used to acquire detection signals with different photon number responses. The data processing module is connected to the time-correlated single-photon counting acquisition unit and is used to image the target under test based on the synchronization signal and the detection signal. High throughput is achieved when the total number of photon counts in the high-throughput photon-counting lidar imaging device is greater than 5% of the total number of periodic laser pulses.

2. The high-throughput photon counting lidar imaging device according to claim 1, characterized in that, The beam adjustment unit includes a perforated mirror, a transceiver assembly, and a filter. The pulsed laser is transmitted through the perforated mirror to the scanning module, modulated by the scanning module, and then transmitted to the transceiver group for emission. The echo beam returned by the target is received by the transceiver group, reflected by the scanning module and the perforated mirror, and then transmitted to the single-photon detector after passing through the filter.

3. The high-throughput photon counting lidar imaging device according to claim 2, characterized in that, The center of the perforation in the perforated mirror is offset from the center of the mirror.

4. The high-throughput photon counting lidar imaging device according to claim 2, characterized in that, The beam adjustment unit also includes a collimating lens group and a converging lens group; The collimating lens group is located between the pulsed laser and the perforated mirror. The collimating lens group includes at least one collimating lens. The pulsed laser is collimated by the collimating lens group and then transmitted to the perforation of the perforated mirror. The converging mirror group is located between the perforated mirror and the single-photon detector. The echo beam reflected by the perforated mirror is converged by the converging mirror group and then transmitted to the single-photon detector.

5. The high-throughput photon counting lidar imaging device according to claim 2, characterized in that, The transceiver assembly includes a first lens and a second lens, and the first lens and the second lens constitute a telescope structure. The surfaces of the first lens and the second lens are provided with anti-reflective coatings.

6. The high-throughput photon counting lidar imaging device according to claim 2, characterized in that, The beam adjustment unit also includes a dichroic mirror, which is located between the perforated mirror and the single-photon detector. The high-throughput photon counting lidar imaging device also includes a monitoring module, which is used to receive a portion of the beam output by the dichroic mirror.

7. The high-throughput photon counting lidar imaging device according to claim 1, characterized in that, The single-photon detector includes a tandem superconducting nanowire single-photon detector; The series-connected superconducting nanowire single-photon detector comprises multiple sets of superconducting nanowires, each set of which is connected in parallel with a resistor, and the multiple sets of superconducting nanowires are connected in series.

8. The high-throughput photon counting lidar imaging device according to claim 1, characterized in that, The detection module also includes a signal amplifier, which is connected between the single-photon detector and the time-correlated single-photon counting acquisition unit.

9. The high-throughput photon counting lidar imaging device according to claim 1, characterized in that, The scanning module includes a biaxial orthogonal scanning galvanometer.

10. A high-throughput photon counting lidar imaging method, characterized in that, The high-throughput photon counting lidar imaging device according to any one of claims 1 to 9, wherein the high-throughput photon counting lidar imaging method comprises: A pulsed laser emits a pulsed laser beam, which is then incident on the target under test after passing through a beam adjustment unit and a scanning module. The echo beam returned by the target under test is then transmitted to the detection module after passing through the beam adjustment unit and the scanning module. A single-photon detector receives the echo beam, and a time-correlated single-photon counting acquisition unit acquires the synchronization signal of the pulsed laser and the detection signals of at least two different photon number responses. The control module controls the scanning module to change the direction of the pulsed laser output in order to scan the target under test; The data processing module images the target under test based on the synchronization signal and the detection signal.

Images