Single-photon streak tube laser radar based on time delay difference

Abstract

The invention discloses a single-photon streak tube laser radar based on a delay difference. The single-photon streak tube laser radar comprises a delay pulse generator, a laser, a delay difference generation module, a beam shaping system and a receiving system. Wherein the delay difference generation module comprises an optical delay path and a time delay path, and can dynamically adjust the delay difference to adapt to near-field high-precision and far-field wide-range detection requirements; the light beam shaping system shapes the laser into a one-dimensional fan-shaped light beam, so that the divergence direction of the one-dimensional fan-shaped light beam is aligned with the time deflection dimension of the streak tube detector, and the energy utilization rate and the streak image quality are improved; the receiving system rejects noise and solves a target distance by using a cross-correlation noise reduction and weighted fusion algorithm through multi-stripe redundancy processing, so that the single-photon detection efficiency and the anti-interference capability are remarkably improved. According to the invention, the detection capability of the system on a long-distance weak reflection target, the reliability in a complex environment and the three-dimensional imaging precision are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser radars and relates to a single-photon streak tube laser radar, and in particular to a single-photon streak tube laser radar based on time delay difference. Background Art

[0002] Traditional single-photon streak tube lidar faces the technical challenge of a relatively fixed delay difference control mechanism in practical applications. Existing solutions mostly rely on a beam-splitting structure with a fixed optical path difference. This design makes it difficult to flexibly adjust the delay difference parameters according to different detection scenarios, resulting in insufficient distance resolution in near-field detection and an inability to cover a sufficient range in far-field detection. At the same time, environmental factors such as temperature changes and mechanical vibrations can easily interfere with the fixed optical path, affecting the stability of the delay difference and detection accuracy. When facing dynamic targets, the acquisition window with a fixed delay difference is also difficult to effectively match the rapidly changing echo signal, limiting the detection capability of moving targets.

[0003] In terms of single-photon detection performance, traditional technologies lack efficient single-photon signal enhancement mechanisms and multi-pulse collaborative processing capabilities, and therefore show obvious deficiencies in the detection of long-distance targets or low-reflectivity targets. Single-photon-level echo signals are easily overwhelmed by noise, resulting in reduced detection reliability. At the same time, the compatibility problem between the detector and the beam shape further aggravates this situation. The traditional circular beam fails to fully consider the working characteristics of the streak tube detector in converting time information into one-dimensional spatial offset, making it impossible to effectively concentrate the beam energy on the sensitive dimension of the detector, resulting in low energy utilization and poor streak image quality.

[0004] In addition, the existing multi-beam detection scheme has dual limitations in hardware architecture and signal processing. The fixed number of beam splitting paths is difficult to flexibly expand according to actual needs. The energy attenuation problem in the multi-level beam splitting process is more prominent. The lack of a multi-stripe redundant processing mechanism leads to insufficient noise resistance of the system when facing complex environmental interference. When a certain beam is affected by ambient light or device noise, it is easy to cause a large deviation in the overall detection results. It is impossible to effectively eliminate abnormal data through multi-path signal comparison, affecting the final distance solution accuracy and system reliability.

[0005] Overall, the core bottlenecks of existing technologies lie in the insufficient adaptability between the delay difference generation mechanism and actual detection needs, the insufficient matching between the beam control method and the detector working principle, and the lack of effective redundancy and enhancement means in the single-photon signal processing process. These problems make it difficult for traditional single-photon streak tube lidar to meet the application requirements of modern high-precision three-dimensional detection in terms of detection accuracy, range coverage, and environmental adaptability. It is urgent to fundamentally solve the above technical problems through innovative design. Summary of the Invention

[0006] To address the low sensitivity of existing streak tube lidars, which cannot meet the requirements for high-precision detection of long-range, weakly reflective targets, this invention provides a single-photon streak tube lidar based on time delay difference. Through the design of a time delay difference generation module, optimized beam shape, and a multi-stripe signal processing mechanism, this system achieves highly sensitive detection of weak optical signals and precise acquisition of three-dimensional target information. This invention improves the system's single-photon detection capability, enabling more accurate distance measurement and target imaging, making it suitable for applications requiring high-precision distance measurement and environmental perception.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A single-photon streak tube laser radar based on time delay difference includes a time delay pulse generator, a laser, a time delay difference generation module, a beam shaping system, and a receiving system, wherein:

[0009] The delay pulse generator is electrically connected to the emission trigger end of the laser and the acquisition trigger end of the receiving system, and outputs a synchronization electrical signal for collaboratively controlling the timing synchronization of the laser emission moment and the detection and acquisition moment, ensuring that the time deviation of the two signals meets the time resolution requirement of the streak tube detector;

[0010] The laser is used to emit a single beam of light or a pulse train of light signals;

[0011] The delay difference generating module is connected to the laser and is used to convert the optical signal into at least two detection lights with controllable delay difference;

[0012] The beam shaping system is connected to the delay difference generation module and is used to perform one-dimensional fan-shaped shaping on the multi-path detection light. The cylindrical lens group is used to make the light beam diverge in a plane perpendicular to the propagation direction and collimate in a plane parallel to the propagation direction, forming a fan-shaped light beam with a divergence direction consistent with the time deflection dimension of the streak tube detector.

[0013] The receiving system includes an optical receiving unit, an image enhancement unit and a high-speed imaging unit, which are used to receive multi-path detection light echoes reflected by the target. After being focused by the optical receiving unit, the echoes are incident on the image enhancement unit. The image enhancement unit multiplies the single-photon echo signal into a detectable signal, which is finally collected by the high-speed imaging unit and converted into an independent fringe image consistent with the number of detection light paths. The echo of each detection light path corresponds to an independent fringe.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] 1. Multi-beam detection can obtain multiple sets of stripe images carrying redundant information about the same target. The subsequent denoising algorithm can effectively eliminate random noise and abnormal signals by analyzing the temporal correlation between multiple stripes. Even if one beam is interfered with by ambient light or device noise, the abnormal data can be verified and filtered out through comparison with the stripe signals of other beams, thereby greatly improving the accuracy and stability of distance solution. This is especially true in complex environments such as strong background light and interference from multiple light sources, which significantly improves the reliability of detection results.

[0016] 2. Multiple light beams are projected onto the target area simultaneously, increasing the number of photon emission and reception paths within the same timeframe, significantly increasing the probability of collecting single-photon echo signals. The energy accumulation effect of multiple light beams effectively enhances the ability to detect weak signals in long-distance or low-reflectivity target scenarios. The synchronous generation of multi-stripe images allows the system to utilize multi-path signals for energy fusion, avoiding detection failures caused by insufficient photons in a single path, thereby improving single-photon detection efficiency and shortening the time to acquire valid data.

[0017] 3. Multi-stripe images contain multi-dimensional information of the target under different delay differences. The collaborative solution of this information can significantly improve the target distance measurement accuracy and three-dimensional spatial positioning accuracy. In near-field detection, the fine delay difference configuration of multiple light beams can achieve higher distance resolution. In far-field detection, the redundant information of multiple stripes can compensate for the measurement error caused by signal attenuation. The system can flexibly adjust the number of beam paths according to different scenarios, improve redundancy by increasing the number of paths in a strong noise environment, and achieve more precise target detection through multi-path collaboration under high-precision requirements.

[0018] 4. The present invention addresses the problems of inflexible delay difference control, low single-photon detection efficiency, and insufficient compatibility between light beams and detectors in traditional technologies, and achieves a technological breakthrough through the collaborative design of a delay difference generation module, a beam shaping system, and a receiving system. The delay difference generation module includes two paths: optical delay and time delay, which can dynamically adjust the delay difference to adapt to the requirements of high-precision near-field and wide-range far-field detection. The beam shaping system shapes the laser into a one-dimensional fan-shaped beam so that its divergence direction is aligned with the time deflection dimension of the streak tube detector, thereby improving energy utilization and streak image quality. The receiving system uses multi-stripe redundant processing, cross-correlation noise reduction, and weighted fusion algorithms to eliminate noise and calculate the target distance, significantly improving the single-photon detection efficiency and anti-interference ability. The present invention effectively improves the system's detection capability for long-distance weak-reflection targets, its reliability in complex environments, and its three-dimensional imaging accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the results of single-photon streak tube lidar based on time delay difference;

[0020] Figure 2 It is a schematic diagram of three optical paths;

[0021] Figure 3 Schematic diagram of multiple light paths;

[0022] Figure 4 Schematic diagram of pulse train;

[0023] In the figure: G1 and G2 are beam splitters, and M1, M2, M3, and M4 are reflectors. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0025] The present invention provides a single-photon streak tube laser radar based on time delay difference, comprising a time delay pulse generator, a laser, a time delay difference generation module, a beam shaping system, and a receiving system, wherein:

[0026] The delay pulse generator is electrically connected to the emission trigger end of the laser and the acquisition trigger end of the receiving system, and is configured to output a synchronization electrical signal for collaboratively controlling the timing synchronization of the laser emission moment and the detection and acquisition moment, ensuring that the time deviation of the two signals meets the time resolution requirement of the streak tube detector;

[0027] The laser is configured to emit a single beam of light or a pulse train light signal, wherein the pulse train comprises a plurality of intra-train pulses arranged at a preset time interval as a detection light source;

[0028] The delay difference generation module is connected to the laser and is configured to convert the optical signal into at least two detection lights with controllable delay differences. The module includes the following two implementation methods:

[0029] (a) Mirror assembly beam splitting unit: This unit includes a beam splitter, a fixed reflector, and an adjustable delay element. The beam splitter splits a single light beam into multiple light signals. After the fixed reflector guides the light path, an adjustable delay element, such as a displacement-adjustable reflector or an acousto-optic modulator, adjusts the optical path difference of each light path, thereby generating a controllable delay difference.

[0030] (b) Pulse train transmitting unit: This unit controls the laser to transmit a pulse train optical signal containing multiple pulses within the train. The time interval between pulses within the train is used to directly form the delay difference of multiple probe beams, with each probe beam corresponding to a pulse within the train.

[0031] The beam shaping system is connected to the delay difference generation module and is configured to perform one-dimensional fan-shaped shaping on the multi-path detection light. The beam is diverged in a plane perpendicular to the propagation direction and collimated in a plane parallel to the propagation direction through a cylindrical lens group, forming a fan-shaped beam whose divergence direction is consistent with the time deflection dimension of the streak tube detector.

[0032] The receiving system includes an optical receiving unit, an image intensification unit, and a high-speed imaging unit, and is configured to receive multi-path detection light echoes reflected by the target. After being focused by the optical receiving unit, the echoes are incident on the image intensification unit. The image intensification unit multiplies the single-photon echo signals into detectable signals, which are finally collected by the high-speed imaging unit and converted into independent fringe images consistent with the number of detection light paths. The echo of each detection light path corresponds to an independent fringe.

[0033] The number of detection optical paths of the time delay difference generation module can be expanded, and the pulse train mode of the laser improves the single photon detection probability through multi-pulse time domain energy accumulation.

[0034] In the present invention, the synchronous control principle of the delayed pulse generator is as follows: output two electrical signals, one triggering the laser to emit light signals, and the other triggering the receiving system to start acquisition. Through timing control, it is ensured that the arrival time of the two echo signals is within the duration of the streak tube scanning voltage, so that the echo signals of all detection lights fall into the acquisition window.

[0035] In the present invention, the laser adopts Nd:YAG solid laser, which outputs 1064nm laser at the fundamental frequency, and is converted into 532nm laser for detection through frequency doubling technology. Combined with the hardware architecture of the delay difference control of the present invention, the laser needs to be equally divided into transmission branch and reflection branch detection light by the mirror group beam unit, so special adaptation requirements are put forward for the laser: First, energy distribution adaptability: taking the splitting ratio of 50:50 as an example, in order to ensure that the two-way split light still has sufficient energy density in the single-photon detection mode, the laser single pulse energy needs to be 1.8~2.2 times that of the traditional single-light path system. Through the design of "single pulse high energy + dual-way beam splitting", the detection sensitivity and system power consumption are balanced; second, the potential for repetition rate improvement: relying on single photons Due to the "sparseness" of the signal, the laser repetition rate can be increased by 50-150% compared to traditional streak tube lidars. By compensating for the energy dispersion of the dual optical paths through high-frequency pulse emission, a high frame rate of 10kHz and dynamic data acquisition efficiency can be achieved. Thirdly, the timing stability requirement: the laser's narrow pulse width ≤10ns and low time jitter ≤1ps directly support the sub-nanosecond optical path difference adjustment accuracy of the delay difference control module, avoiding dual-stripe matching deviations caused by the laser's own timing errors, thereby enhancing noise rejection capabilities and signal acquisition stability. The selection of a 532nm laser is based not only on the quantum efficiency advantage of the photocathode, but also through the coordinated optimization of energy, repetition rate, and timing characteristics, deeply adapted to the hardware requirements of the dual-stripe detection architecture of the present invention.

[0036] In the present invention, the mirror assembly beam-bearing unit adjusts the optical path through physical displacement or optical modulation: piezoelectric ceramics are used to drive the reflector to move along the optical axis to change the optical path, or an acousto-optic modulator is used to change the propagation speed of light, thereby realizing dynamic control of the delay difference between each light path.

[0037] In the present invention, the pulse train emission unit controls the driving electrical signal of the laser to continuously emit multiple pulses in a short period of time. The time interval between the pulses in the train is the delay difference between the two adjacent detection lights. Adjusting the number of pulses in the train can expand the number of detection light paths.

[0038] In the present invention, the delay difference generation module can divide the laser into two, three or more beams according to needs. It includes two delay paths. The specific structure and working principle of the delay difference generation module are described using two optical paths and three optical paths as examples:

[0039] like Figure 1 As shown in the figure, the time delay difference generation module is the core component for dual-stripe detection. The specific implementation of its two-beam beam splitting is as follows: the laser beam emitted by the laser is incident on the beam splitter G1, which splits the incident light into a transmission main branch and a reflection delay branch. The transmission main branch: the laser light directly passes through G1 and is transmitted along the original optical axis. The reflection delay branch: after being reflected by G1, the laser light first enters the fixed reflector M1, is deflected by M1, and then enters the adjustable reflector M2. The beam reflected by M2 is then transmitted to the adjustable reflector M3, and after reflection, it merges with the transmission main branch beam. After reflecting from the target, the two detection beams return to the streak tube detector. Due to the optical path difference, a dual-stripe image corresponding to the time interval and the optical path difference is formed on the detector.

[0040] like Figure 2 As shown in the figure, the delay difference generation module is the core component for achieving three-fringe detection. The specific implementation of its three-beam beam splitting is as follows: the laser beam emitted by the laser is incident on the first-stage beam splitter G1, which splits the incident light into a transmission main branch and a reflection primary branch. The transmission main branch: the laser light directly passes through G1 and propagates along the original optical axis, serving as the reference beam, with an optical path difference ΔL = 0. The reflection primary branch: after being reflected by G1, the laser light is incident on the second-stage beam splitter G2, which splits it into a reflection secondary branch and a transmission secondary branch. The reflection secondary branch: after being reflected by G2, the laser light is incident on the adjustable reflector M3. The beam reflected by M3 is transmitted to the adjustable reflector M4, and then merges with the other beams after reflection. The transmission secondary branch: the laser light directly passes through G2 and is incident on the adjustable reflector M2. The beam reflected by M2 is transmitted to M4, and then merges with the other beams after reflection. The three detection beams are reflected by the target and return to the streak tube detector. Due to the optical path difference, three fringe images corresponding to the time interval and the optical path difference are formed on the detector.

[0041] The time delay path (TD) is a system that controls the laser to emit a pulse train signal consisting of multiple pulses within a train, directly generating a delay difference using the time interval between adjacent pulses. Specifically, the system adjusts the laser's driving electrical signal to cause it to emit multiple pulses in a short period of time. Each pulse corresponds to a probe beam path, and the time interval between adjacent pulses determines the delay difference between the adjacent probe beam paths. For example, when the laser emits a signal consisting of three pulses within a train, the time interval between the first and second pulses forms the delay difference between the first and second probe beam paths. The time interval between the second and third pulses forms the delay difference between the second and third beam paths, and so on. This approach eliminates the need for additional optical beam splitting components or complex optical path adjustments; delay difference generation is achieved solely through electrical signal control, significantly simplifying the system's hardware architecture. The TD path, with its simple structure and fast response, is more suitable for scenarios requiring high integration and real-time performance. The optical delay path, with its high-precision and wide-range delay difference adjustment capability, is more suitable for scenarios with stringent range resolution requirements, such as high-precision measurement. The collaborative design of the two provides flexible options for optimizing lidar performance across diverse applications.

[0042] In the present invention, the beam shaping system uses a cylindrical lens group to asymmetrically shape the detection light: in the plane perpendicular to the propagation direction, the cylindrical lens causes the light beam to diverge to form a fan-shaped coverage, corresponding to the time deflection dimension of the streak tube; in the plane parallel to the propagation direction, the cylindrical lens keeps the light beam collimated to concentrate the energy, forming a fan-shaped beam adapted to the characteristics of the streak tube detector.

[0043] In this invention, the beam shaping system adjusts the laser output beam into a shape that is compatible with the characteristics of the streak tube detector. Using optical components, it shapes the laser's one-dimensional divergence, converting the original circular beam into a fan-shaped beam. This ensures that the beam's divergence direction is strictly aligned with the streak tube detector's temporal deflection dimension. This design concentrates energy in the detector's sensitive area, avoiding redundant energy distribution in non-sensitive dimensions, thereby improving detection efficiency and fringe image quality.

[0044] In the present invention, the receiving system includes an optical receiving unit, an image enhancement unit and a high-speed imaging unit. The optical receiving unit in the receiving system is used to focus the target echo light signal; the image enhancement unit is constructed to multiply the single-photon echo signal into a detectable electron cloud; the high-speed imaging unit responds to the electrical trigger signal and synchronously collects independent stripe images corresponding to the number of split-beam detection lights.

[0045] In the present invention, the core function of the receiving system is to convert the weak light signal reflected by the target into a collectible multi-stripe image. The two beams of detection light reflected by the target are collected by the optical receiving system, the background light interference is suppressed by a narrow-band filter, and then focused on the photocathode surface of the streak tube. The focal length and field angle design of the optical receiving system ensure that the multiple beams of echo light are accurately incident on the corresponding area of the photocathode. After receiving the light signal, the photocathode generates photoelectrons. The photoelectrons are accelerated by the high voltage applied by the accelerating electrode, and enter the microchannel plate (MCP) after obtaining sufficient kinetic energy. The channel structure inside the MCP multiplies the single photoelectron to form a multi-electron containing about 10 ^6 The multiplied electron cloud significantly enhances the signal strength, enabling the detection of weak single-photon signals. The multiplied electron cloud enters the streak tube's deflection field. The voltage of the deflection field varies linearly with time, causing electron clouds arriving at different times to undergo varying degrees of lateral deflection—earlier electrons experience smaller deflections, while later electrons experience larger deflections. This converts the temporal information of the optical signal into spatial positional information of the electron cloud. The electron clouds corresponding to the multiple echo light signals with different optical path lengths arrive at different times, and under the action of the deflection field, they form multiple fringes with lateral spacing corresponding to the optical path length differences. The deflected electron cloud strikes the fluorescent screen, stimulating the fluorescent material to emit light, forming a multi-fringe image. A high-speed CMOS camera captures the screen in real time at a high frame rate, capturing multi-fringe image data containing temporal information and light intensity distribution. The camera's pixel resolution and frame rate ensure that the spatial positions and time intervals of the multiple fringes are accurately recorded, providing the raw information for subsequent data processing.

Claims

1. A single-photon streak tube laser radar based on time delay difference, characterized in that The single-photon streak tube laser radar includes a time-delay pulse generator, a laser, a time-delay difference generation module, a beam shaping system, and a receiving system, wherein: The delay pulse generator is electrically connected to the emission trigger end of the laser and the acquisition trigger end of the receiving system, and outputs a synchronization electrical signal for collaboratively controlling the timing synchronization of the laser emission moment and the detection and acquisition moment, ensuring that the time deviation of the two signals meets the time resolution requirement of the streak tube detector; The laser is used to emit a single beam of light or a pulse train of light signals; The delay difference generating module is connected to the laser and is used to convert the optical signal into at least two detection lights with controllable delay difference; The beam shaping system is connected to the delay difference generation module and is used to perform one-dimensional fan-shaped shaping on the multi-path detection light. The cylindrical lens group is used to make the light beam diverge in a plane perpendicular to the propagation direction and collimate in a plane parallel to the propagation direction, forming a fan-shaped light beam with a divergence direction consistent with the time deflection dimension of the streak tube detector. The receiving system includes an optical receiving unit, an image enhancement unit and a high-speed imaging unit, which are used to receive multi-path detection light echoes reflected by the target. After being focused by the optical receiving unit, the echoes are incident on the image enhancement unit. The image enhancement unit multiplies the single-photon echo signal into a detectable signal, which is finally collected by the high-speed imaging unit and converted into an independent fringe image consistent with the number of detection light paths. The echo of each detection light path corresponds to an independent fringe.

2. The single-photon streak tube laser radar based on time delay difference according to claim 1, characterized in that The delayed pulse generator outputs two electrical signals, one to trigger the laser to emit light signals, and the other to trigger the receiving system to start acquisition. Through timing control, it is ensured that the arrival time of the two echo signals is within the duration of the streak tube scanning voltage, so that the echo signals of all detection lights fall into the acquisition window.

3. The single-photon streak tube laser radar based on time delay difference according to claim 1, characterized in that The laser adopts Nd:YAG solid laser, which outputs 1064nm laser at fundamental frequency and is converted into 532nm laser for detection through frequency doubling technology.

4. The single-photon streak tube laser radar based on time delay difference according to claim 1, characterized in that The delay difference generation module is a mirror group beam-forming unit, which includes a beam splitter, a fixed reflector and an adjustable delay element. The beam splitter is used to split a single beam of light into multiple optical signals. After the light path is guided by the fixed reflector, the optical path difference of each light path is adjusted by the adjustable delay element, thereby generating a controllable delay difference.

5. The single-photon streak tube laser radar based on time delay difference according to claim 1, characterized in that The delay difference generation module is a pulse train emission unit, which controls the laser to emit a pulse train optical signal containing multiple pulses in the train, and uses the time interval between the pulses in the train to directly form the delay difference of multiple detection lights, each detection light corresponding to one pulse in the train.

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