Laser radar measurement system and method based on optical switch gating

Abstract

The invention discloses a laser radar measurement system and method based on optical switch gating, the system comprises a transmitting unit, a receiving unit and an electronics unit, the transmitting unit comprises a transmitting light path and a laser located on the transmitting light path, and the receiving unit comprises a receiving light path and an optical switch and a detector located on the receiving light path. The electronics unit comprises a main control circuit and a timing circuit; the main control circuit is used for controlling the output of the laser, controlling the on-off of the optical switch assembly and reading and calculating the data of the timing circuit; the optical switch assembly is located in front of the input end of the detector, and the main control circuit presets a time sequence according to the gating range so as to control the on-off time sequence of the light passing state and the isolation state of the optical switch assembly based on the gating range. The optical switch is arranged in front of the detector, so that return light energy in the non-gating interval can be effectively blocked, the detector can normally respond to return light in the gating interval, response of the detector to the return light in the non-gating interval is avoided, and the target detection probability and efficiency are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser radar measurement, and in particular relates to a laser radar measurement system and method based on optical switch gating. Background Art

[0002] LiDAR has relatively important application value in the fields of autonomous driving, precision measurement, remote sensing mapping, etc. LiDAR is a highly promising optical precision measurement method. However, due to the rapid attenuation of laser energy in the medium, the return light energy is often relatively weak, and there is strong noise in the transmission environment. Therefore, the signal-to-noise ratio is a key indicator that determines the performance of LiDAR.

[0003] Existing laser radars mainly gate echo signals through high-speed circuits, that is, they gate signals by controlling the working time of the detector during the entire detection cycle. This method can effectively isolate signals during non-gated time, so that the detector only responds to signals within the detection cycle.

[0004] However, in practical applications, since the target may exist in water or other complex media (such as smoke, dust, etc.), the effect of this method is not ideal. For example, in underwater target detection scenarios, due to the serious scattering effect of water on the light beam, the backscattered return light is very strong and will reach the detector target surface through the optical path. Although the detector's working range can be adjusted to avoid the detector responding at this moment, due to the influence of device process and material properties, the stray light energy will still stay on the detector target surface for a period of time, resulting in the detector responding to the stray light signal first when the power is turned on, and entering the "blind" state during the response period, that is, unable to respond to the current return light energy. In summary, when the laser radar is currently measuring a target, due to the complexity of the medium, the stray light energy may stay on the detector target surface for a period of time, resulting in the detector responding to the stray light signal first when the power is turned on, and entering the blind state during the response period, resulting in the inability to respond to the target's return light energy, affecting the measurement effect. Summary of the invention

[0005] The present invention provides a laser radar measurement system and method based on optical switch gating, aiming to solve the problem that when the laser radar performs target measurement, due to the complexity of the medium, the stray light energy may stay on the detector target surface for a period of time, causing the detector to respond to the stray light signal first when the power is started, and enter a blinding state during the response period, resulting in the inability to respond to the target's return light energy, affecting the measurement effect.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: The present invention provides a laser radar measurement system based on optical switch gating, which can be configured on a target to be measured so as to measure the distance of the target to be measured; the laser radar measurement system includes a transmitting unit, a receiving unit and an electronics unit, wherein: The transmitting unit includes a transmitting optical path and a laser located in the transmitting optical path, the receiving unit includes a receiving optical path and an optical switch and a detector located in the receiving optical path, and the electronics unit includes a main control circuit and a timing circuit; the main control circuit is used to: control the output of the laser, control the on and off of the optical switch component, and read and calculate the data of the timing circuit; The optical switch component is located in front of the input end of the detector, and the output of the optical switch component serves as the input of the detector; the timing circuit is located behind the output end of the detector, and the response of the detector serves as the input of the timing circuit; the main control circuit presets the timing according to the selection range, so as to be able to control the on-off timing of the light-passing state and the isolation state of the optical switch component based on the selection range.

[0007] In some embodiments, the optical switch assembly includes a plurality of optical switches, and the plurality of optical switches are arranged in a cascade combination. When the plurality of optical switches are arranged, the main control circuit presets the timing of different optical switches.

[0008] In some embodiments, the detector comprises a single point detector or an array detector.

[0009] In some embodiments, when the target to be measured is a moving target, the main control circuit adjusts the selection range according to the ranging result of the moving target in the previous frame, and synchronizes the selection range to the timing of the main control circuit to achieve selection and measurement of the moving target.

[0010] In some embodiments, the laser radar measurement system is further configured with a scanning mirror or a turntable to illuminate the target to be measured at different angles and ranges.

[0011] In some embodiments, the transmitting optical path and the receiving optical path form a light transmitting and receiving optical path, and the light transmitting and receiving optical path includes a coaxial optical path or a non-coaxial optical path.

[0012] In some embodiments, the optical switch assembly selects spatial optical coupling or fiber coupling according to the model.

[0013] The present invention also provides a laser radar measurement method based on optical switch gating. The laser radar measurement method based on optical switch gating is based on the above-mentioned laser radar measurement system based on optical switch gating. The laser radar measurement method comprises the following steps: S1. Preset the timing of the main control circuit according to the gating range; and synchronize the timing of the main control circuit to the optical switch component. The main control circuit controls the time delay of the optical switch component in the light-transmitting state or the isolation state based on the gating range; the switch component receives diffuse reflection energy only when it is in the light-transmitting state; S2, the main control circuit sends a signal to the laser to trigger the laser to emit a pulse laser, and the signal is synchronized to the timing circuit as the emission signal time, and the pulse laser passes through the emission optical path to the target to be measured; S3, the receiving optical path collects the diffuse reflection energy of the target to be measured, and couples the diffuse reflection energy to the optical switch component; S4, the optical switch assembly outputs diffuse reflection energy to the detector, the detector response is used as the input of the timing circuit, and the timing circuit records the time of the return light signal; S5. The main control circuit reads the time of the transmitted signal and the time of the returned light signal to obtain the distance information of the current target to be measured.

[0014] Furthermore, it also includes S6, repeating S2-S5 several times to measure the target to be measured several times, repeating S2-S5 several times to measure the target to be measured several times, and obtaining discrete echo waveforms based on the arrival times of the several echoes to obtain distance information.

[0015] Furthermore, it also includes S7. If the detector is a single-point detector, S2-S5 are repeated. The single-point detector needs to be adjusted each time it is repeated, and different positions of the target to be measured are measured or scanned to obtain several groups of pixels. The scanning realizes three-dimensional imaging; if the detector is an array detector, three-dimensional imaging is directly realized.

[0016] Compared with the prior art, the laser radar measurement system and method based on optical switch gating of the present invention has the following beneficial effects: The present invention is based on a laser radar measurement system for optical switch gating, and the laser radar measurement system can be configured on a target to be measured so as to measure the distance of the target to be measured; the laser radar measurement system comprises a main control circuit and a transmitting optical path and a receiving optical path configured on the main control circuit, wherein: the transmitting optical path comprises a laser, and the receiving optical path comprises an optical switch component, a detector and a timing circuit; the main control circuit is used to: control the output of the laser, control the on and off of the optical switch component, and read the data of the timing circuit; the optical switch component is located in front of the input end of the detector, and the output of the optical switch component serves as the input of the detector; the timing circuit is located behind the output end of the detector, and the response of the detector serves as the input of the timing circuit; the main control circuit presets a timing sequence according to a gating range, so as to control the on and off timing of the light-passing state and the isolation state of the optical switch component based on the gating range. The present invention gates the echo signal by placing the optical switch in front of the input end of the detector, that is, in a non-gating interval, the optical switch can be kept in a closed state, and the return light energy will be significantly attenuated, so that the return light at this moment cannot trigger the detector or significantly reduces the probability of the detector being triggered. At the same time, in the gating interval, the optical switch can be converted to a light-passing state, so that the return light energy can smoothly reach the target surface of the detector and trigger the detector to respond, and then the current echo signal is recorded by the timing circuit and the main control circuit to obtain the distance data of the target. Compared with the gating method of the high-speed circuit, the present invention can effectively block the return light energy in the non-gating interval, so that the detector can normally respond to the return light in the gating interval, avoiding the detector's response to the return light in the non-gating interval, and improving the detection probability and detection efficiency of the target. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0018] Figure 1 This is a schematic diagram of the architecture of a laser radar measurement system based on optical switch gating according to the present invention; Figure 2 A schematic flow chart of a laser radar measurement method based on optical switch gating according to the present invention; Figure 3 A schematic diagram comparing detection effects of different gating methods in a laser radar measurement method based on optical switch gating of the present invention; Figure 4 The present invention is a schematic diagram of the application state of a laser radar measurement system based on optical switch gating. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0022] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0023] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0024] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] How to effectively block the return light energy in the non-gated interval so that the detector can respond normally to the return light in the gated interval, avoid the detector's response to the return light in the non-gated interval, and thus improve the measurement accuracy and efficiency of the target as a whole.

[0026] Based on this, Figure 1 As shown, the present invention provides a laser radar measurement system based on optical switch gating, the laser radar measurement system can be configured on a target to be measured so as to measure the distance of the target to be measured; the laser radar measurement system includes a transmitting unit, a receiving unit and an electronics unit, wherein: The transmitting unit includes a transmitting optical path and a laser located in the transmitting optical path, the receiving unit includes a receiving optical path and an optical switch and a detector located in the receiving optical path, and the electronics unit includes a main control circuit and a timing circuit; the main control circuit is used to: control the output of the laser, control the on and off of the optical switch component, and read and calculate the data of the timing circuit; like Figure 3 As shown, the optical switch assembly is located in front of the input end of the detector, and the output of the optical switch assembly serves as the input of the detector; the timing circuit is located behind the output end of the detector, and the response of the detector serves as the input of the timing circuit; the main control circuit presets the timing according to the gating range, so as to be able to control the on-off timing of the light-passing state and the isolation state of the optical switch assembly based on the gating range. The laser radar measurement system based on the optical switch gating of the present invention can allow the light return to trigger the detector response at a specific moment by using the optical switch placed in front of the detector to accurately gate the return light, effectively avoiding the interference of stray light on the detector, resulting in damage to the detector or reduced detection accuracy, thereby improving the efficiency and accuracy of detection. Compared with the traditional high-speed circuit gating scheme, the laser radar measurement system of the present invention directly isolates or reduces the intensity of the return light in the non-gating interval from the physical level based on the optical gating, and the main control circuit presets the timing according to the gating range, realizes the precise control of the on-off state of the optical switch assembly, ensures that the detector only responds to valid signals within the set gating interval, and reduces the probability of false triggering of the detector. The laser radar measurement system of the present invention can adapt to complex and changeable detection environments, such as scenes with severe underwater scattering effects, by accurately presetting and controlling the switching moments of the optical switch, thereby ensuring stable operation and reliable measurement of the system under harsh conditions.

[0027] In some embodiments, the optical switch assembly of the present invention includes a plurality of optical switches, and the plurality of optical switches are arranged in a cascade combination. When the plurality of optical switches are arranged, the main control circuit presets the timing of the plurality of optical switches according to the gating range. Specifically: since the plurality of optical switches of the present invention are arranged in a cascade combination, although the gating range of each optical switch is the same, the position of each optical switch is different, and the time when the optical signal arrives at each optical switch will also be different. The main control circuit calculates the time when the optical signal arrives according to the gating range and the optical path difference caused by the positions of the plurality of optical switches, and then presets the timing according to the different times when the optical signal arrives at the optical switch, and finally controls the opening and closing time of each optical switch according to the preset timing to ensure that the optical signal can pass through the cascade optical switch according to the predetermined path and time point.

[0028] The present invention enhances the isolation capability of the non-gated area by cascading a plurality of optical switches, and the main control circuit ensures that each optical switch can be turned on or off at the correct time point by presetting the timing, thereby further improving the measurement accuracy.

[0029] Furthermore, the detector of the present invention includes a single-point detector or an array detector. The single-point detector can realize three-dimensional imaging by scanning, while the array detector can directly realize three-dimensional imaging, thereby improving the functionality and practicality of the measurement system.

[0030] Furthermore, the optical switch gating of the present invention is not only applicable to single-photon detectors (such as Geiger mode detectors), but also to common detector types such as CMOS and CCD, so that the present invention is applicable to different types of lidar systems.

[0031] In some embodiments, in the present invention, when the target to be measured is a moving target, the main control circuit adjusts the gating range according to the ranging result of the moving target in the previous frame, and synchronizes the gating range to the timing of the main control circuit to achieve gating and measurement of the moving target. The present invention can ensure that the measurement system accurately tracks and measures the moving target, and improves the adaptability of the measurement system in a dynamic environment.

[0032] In some embodiments, the laser radar measurement system of the present invention is also configured with a scanning mirror or a turntable to illuminate the target to be measured at different angles and ranges, thereby expanding the application scope of the measurement system and improving the measurement capability of the measurement system for complex targets.

[0033] Furthermore, in some practical working conditions, the light transmitting and receiving path of the present invention can be a coaxial light path or a non-coaxial light path. The optical switch component selects spatial light coupling or fiber coupling according to the model, meeting the design requirements in different application scenarios.

[0034] like Figure 2 and Figure 4The laser radar measurement system based on optical switch gating of the present invention is mainly composed of main control circuit, laser, optical switch, detector and timing circuit and other components, and the light beam is sent and received through the transmitting optical path and the receiving optical path. The main working process of the system is as follows: S1. Preset the timing of the main control circuit according to the gating range; and synchronize the timing of the main control circuit to the optical switch component. The main control circuit controls the time delay of the optical switch component in the light-transmitting state or the isolation state based on the gating range; the switch component receives diffuse reflection energy only when it is in the light-transmitting state; S2, the main control circuit sends a signal to the laser to trigger the laser to emit a pulse laser, and the signal is synchronized to the timing circuit as the emission signal time, and the pulse laser passes through the emission optical path to the target to be measured; S3, the receiving optical path collects the diffuse reflection energy of the target to be measured, and couples the diffuse reflection energy to the optical switch component; S4, the optical switch assembly outputs diffuse reflection energy to the detector, the detector response is used as the input of the timing circuit, and the timing circuit records the time of the return light signal; S5. The main control circuit reads the time of the transmitted signal and the time of the returned light signal to obtain the distance information of the current target to be measured.

[0035] In some actual working conditions, S6 is also included, S2-S5 is repeated several times to measure the target to be measured several times, and discrete echo waveforms are obtained based on the arrival times of the several echoes to obtain distance information.

[0036] Furthermore, in some actual working conditions, S7 is also included. If the detector is a single-point detector, S2-S5 are repeated. The single-point detector needs to be adjusted each time it is repeated. The target to be measured is measured or scanned at different positions to obtain a plurality of groups of pixels. The scanning realizes three-dimensional imaging. If the detector is an array detector, three-dimensional imaging is directly realized. The following is a detailed description of a laser radar measurement system and method based on optical switch gating according to the present invention through specific embodiments.

[0037] 1) Set the timing of the main control circuit (the following describes the process within one cycle, and repeat the above process several times to complete the collection of multiple signals); a. Pulse laser synchronization signal T1; b. Assume that the selection distance is [D1, D2], the speed of light in the medium is c, and the response time of the optical switch is T2. The selection time of the optical switch is [T1+2D1 / c-T2, T1+2D2 / c-T2]. That is, the main control circuit controls the optical switch to open only during this part of the time, and it is in the closed state for the rest of the time.

[0038] 2) The main control circuit sends out a synchronization signal at time T1 to control the pulse laser to emit pulse laser; 3) The pulse laser illuminates the target through the receiving / emitting path, where the receiving / emitting path can be coaxial or non-coaxial; 4) The return light diffusely reflected by the target is collected by the receiving / emitting circuit and coupled to the optical switch; the optical switch can be spatial optical coupling or fiber coupling, depending on the specific design and selection of the device; 5) The optical switch is synchronized with the main control circuit, and according to the timing set by the main control circuit, the optical switch is only in the open state within the time range of [T1+2D1 / c-T2, T1+2D2 / c-T2]; 6) The return light within the selection range reaches the target surface of the photodetector through the optical switch. The photodetector responds to the signal and synchronizes the output signal to the timing circuit; 7) The timing circuit records the arrival time T3 of the return light, and obtains the synchronization signal T1 of the laser by synchronizing with the main control circuit; 8) According to the principle of time-of-flight ranging, the target distance D3=(T3-T1)×c / 2; 9) To improve the measurement accuracy, steps 2-8 can be repeated to measure the target multiple times, and the arrival times of multiple echoes can be counted to obtain discrete echo waveforms (the horizontal axis is the echo delay, and the vertical axis is the number of photon events), and then the distance information can be obtained based on the waveforms; 10) If imaging of the target is required, a precise beam pointing mechanism such as a scanning mirror or a turntable can be added to ensure that the target is illuminated. Repeat 2-9 for each pixel; If it is a moving target, repeat 1-9 and adjust the selection range setting in 1) according to the target distance in 8). The selection range is changed to [D3-(D2-D1) / 2, D3+(D2-D1) / 2].

[0039] In summary, the present invention is a laser radar measurement system and method based on optical switch gating. By placing the optical switch component in front of the detector input end, the gating of the return light signal is realized, the return light energy in the non-gated interval is effectively blocked, and the detector is prevented from responding to the return light in the non-gated interval. The main control circuit presets the timing according to the gating range, accurately controls the on and off of the optical switch component, ensures that the detector only responds to valid signals within the set gating interval, and reduces the probability of false triggering of the detector. The system of the present invention can be applied to complex and changeable detection environments and has better applicability.

[0040] Finally, it should be noted that the above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the specification and described above, and any equivalent changes made by using the technical content disclosed above are equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A laser radar measurement system based on optical switch gating, characterized in that: The laser radar measurement system can be configured on a target to be measured so as to measure the distance of the target to be measured; the laser radar measurement system includes a transmitting unit, a receiving unit and an electronics unit, wherein: The transmitting unit includes a transmitting optical path and a laser located in the transmitting optical path, the receiving unit includes a receiving optical path and an optical switch and a detector located in the receiving optical path, and the electronic unit includes a main control circuit and a timing circuit; the main control circuit is used to: control the output of the laser, control the on and off of the optical switch component, and read and calculate the data of the timing circuit; The optical switch component is located in front of the input end of the detector, and the output of the optical switch component serves as the input of the detector; the timing circuit is located behind the output end of the detector, and the response of the detector serves as the input of the timing circuit; the main control circuit presets the timing according to the selection range, so as to be able to control the on-off timing of the light-passing state and the isolation state of the optical switch component based on the selection range.

2. The laser radar measurement system based on optical switch gating according to claim 1 is characterized in that: The optical switch assembly includes a plurality of optical switches, and the plurality of optical switches are arranged in a cascade combination. When the plurality of optical switches are arranged, the main control circuit presets the timing of different optical switches.

3. The laser radar measurement system based on optical switch gating according to claim 1 is characterized in that: The detector includes a single point detector or an array detector.

4. The laser radar measurement system based on optical switch gating according to claim 1 is characterized in that: When the target to be measured is a moving target, the main control circuit adjusts the gating range according to the ranging result of the moving target in the previous frame, and synchronizes the gating range to the timing of the main control circuit to achieve gating and measurement of the moving target.

5. The laser radar measurement system based on optical switch gating according to claim 1 is characterized in that: The laser radar measurement system is also configured with a scanning mirror or a turntable to illuminate targets to be measured at different angles and ranges.

6. The laser radar measurement system based on optical switch gating according to claim 1, characterized in that: The transmitting optical path and the receiving optical path form a light-transmitting and light-emitting path, and the light-transmitting and light-emitting path includes a coaxial optical path or a non-coaxial optical path.

7. The laser radar measurement system based on optical switch gating according to claim 1 is characterized in that: The optical switch assembly selects spatial optical coupling or optical fiber coupling according to the model.

8. A laser radar measurement method based on optical switch gating, characterized in that: The laser radar measurement method based on optical switch gating is performed based on the laser radar measurement system based on optical switch gating according to any one of claims 1 to 7, and the laser radar measurement method comprises the following steps: S1. Preset the timing of the main control circuit according to the gating range; and synchronize the timing of the main control circuit to the optical switch component. The main control circuit controls the time delay of the optical switch component in the light-transmitting state or the isolation state based on the gating range; the switch component receives diffuse reflection energy only when it is in the light-transmitting state; S2, the main control circuit sends a signal to the laser to trigger the laser to emit a pulse laser, and the signal is synchronized to the timing circuit as the emission signal time, and the pulse laser passes through the emission optical path to the target to be measured; S3, the receiving optical path collects the diffuse reflection energy of the target to be measured, and couples the diffuse reflection energy to the optical switch component; S4, the optical switch assembly outputs diffuse reflection energy to the detector, the detector response is used as the input of the timing circuit, and the timing circuit records the time of the return light signal; S5. The main control circuit reads the time of the transmitted signal and the time of the returned light signal to obtain the distance information of the current target to be measured.

9. The laser radar measurement method based on optical switch gating according to claim 8 is characterized in that: The method further includes S6, repeating S2-S5 for several times to measure the target for several times, and obtaining discrete echo waveforms based on the arrival times of the several echoes to obtain distance information.

10. The laser radar measurement method based on optical switch gating according to claim 8, characterized in that: It also includes S7. If the detector is a single-point detector, S2-S5 are repeated. Each time the steps are repeated, auxiliary equipment is needed to adjust and change the direction of the light beam illumination to achieve scanning. The target to be measured is measured or scanned at different positions to obtain several groups of pixels. The scanning achieves three-dimensional imaging. If the detector is an array detector, three-dimensional imaging is directly achieved.

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