Laser radar based on coaxial receiving and transmitting light path

Abstract

The utility model discloses a laser radar based on a coaxial receiving and transmitting light path, and aims to solve the problem of poor distance measurement precision of the existing laser radar. The device comprises a Newton type reflecting telescope, a coaxial receiving and emitting light path and a hardware correlator, a first reflecting mirror, a shaping beam expander and a pulse laser are sequentially arranged on one side of a lens cone in the axial direction, and a second reflecting mirror, an optical fiber coupler, a fast light intensity modulator and a photon detector are sequentially arranged on the other side of the lens cone in the axial direction; based on the Newton type reflection telescope and the fast light intensity modulator and through cooperation of the duplex auxiliary mirror, the first reflector and the second reflector, the distance measurement device has the advantages of being high in distance measurement precision, high in spatial resolution, insensitive to stray light, simple in data processing and the like, and powerful support is provided for related research of weather detection and distance detection; a coaxial design is adopted, and the transmitting unit and the receiving unit are integrated together, so that an overlapping factor can be improved to the maximum, and a higher light beam utilization rate and higher detection efficiency are achieved.

Description

Technical Field

[0001] This application relates to the field of optical distance measurement technology, specifically to a lidar based on a coaxial light-receiving path. Background Technology

[0002] With the development of industry and agriculture, cultural and sports performances, and social activities, there is an increasing demand for small-scale weather forecasting. Weather element detection based on lidar is receiving more and more attention. Traditional lidar can measure meteorological elements such as distance, temperature, humidity, wind speed, composition, and particle size, but it also has some shortcomings. For example, the laser echo intensity decreases non-linearly, making the signal of distant targets weak and difficult to detect and measure accurately; the signal-to-noise ratio is very low, which affects the detection accuracy and data quality; the distance measurement accuracy of such equipment on the market varies greatly, making it difficult to guarantee the consistency and reliability of the data; in addition, there are many difficulties in the horizontal comparison and in-depth processing of the obtained data, which are important factors restricting the development of the industry. Utility Model Content

[0003] Therefore, this application provides a lidar based on a coaxial light-receiving path to solve the problem of poor distance measurement accuracy in existing lidars.

[0004] To achieve the above objectives, this application provides the following technical solution:

[0005] A lidar based on a coaxial light-receiving path includes: a Newtonian reflecting telescope, a coaxial light-receiving path, and a hardware correlator. The Newtonian reflecting telescope includes a telescope tube, a primary mirror is disposed at the bottom of the telescope tube, and a duplex secondary mirror is disposed at a 45-degree angle at the opening of the upper part of the telescope tube.

[0006] The mirror barrel is provided with a first reflecting mirror, a beam shaper and a pulsed laser arranged sequentially along the axial direction on one side corresponding to the duplex sub-mirror. On the other side corresponding to the duplex sub-mirror, the mirror barrel is provided with a second reflecting mirror, a fiber coupler, a fast intensity modulator and a photon detector arranged sequentially along the axial direction. The first reflecting mirror is arranged parallel to the duplex sub-mirror, and the second reflecting mirror is arranged symmetrically to the duplex sub-mirror. The pulsed laser and the photon detector are connected to the hardware correlator.

[0007] The coaxial optical path includes a coaxial transmitting optical path and a coaxial receiving optical path. The laser beam emitted by the pulsed laser enters the lens tube through the first reflecting mirror, and is then emitted through the duplex sub-mirror to form the coaxial transmitting optical path. Various components in the atmosphere scatter the laser beam, which then enters the lens tube and passes through the duplex sub-mirror, the second reflecting mirror, the fiber coupler, and the fast light intensity modulator in sequence before entering the photon detector and being converted into an electrical signal to form the coaxial receiving optical path.

[0008] Optionally, it also includes a temperature controller connected to the pulsed laser via a Peltier element.

[0009] Optionally, the duplex secondary mirror is two or a combination of a concave mirror, a plane mirror, a micromirror array, a reflecting prism, a dielectric film reflecting mirror, a pentaprism, and a pentamirror.

[0010] Optionally, the first reflector and the second reflector are aluminum-coated reflectors.

[0011] Optionally, the pulsed laser and the first reflector are provided with a beam-shaping expander, the beam-shaping expander being a combination of a cylindrical mirror and a beam expander.

[0012] Optionally, the photosensitive element inside the photon detector is an avalanche diode operating in Geiger mode.

[0013] Optionally, the fast light intensity modulator is one of an electro-optic modulator, an acousto-optic modulator, or a magneto-optic modulator.

[0014] Optionally, the hardware correlator has a 1ps time resolution and 2-18 channels, and its communication interface includes a USB interface and an Ethernet port.

[0015] Optionally, the temperature range of the pulsed laser is 20°C to 30°C.

[0016] Optionally, the outer wall of the lens barrel is provided with a first opening and a second opening for the coaxial emitting optical path and the coaxial receiving optical path to pass through, respectively.

[0017] Compared with the prior art, this application has at least the following beneficial effects:

[0018] 1. Based on further analysis and research of existing technical problems, this application improves a lidar based on a coaxial light-receiving path, including: a Newtonian reflecting telescope, a coaxial light-receiving path, and a hardware correlator. A first reflecting mirror, a beam shaper and expander, and a pulsed laser are sequentially arranged along the axial direction on one side of the telescope tube, while a second reflecting mirror, an optical fiber coupler, a fast intensity modulator, and a photon detector are sequentially arranged along the axial direction on the other side. Based on the Newtonian reflecting telescope and the fast intensity modulator, and through the cooperation of a duplex sub-mirror, the first reflecting mirror, and the second reflecting mirror, this application features high distance measurement accuracy, high spatial resolution, insensitivity to stray light, and simple data processing. It can detect the distance of weather elements in real time, achieving high-resolution imaging and providing strong support for weather detection and distance detection-related research. The coaxial design integrates the transmitting and receiving units, maximizing the overlap factor, resulting in higher beam utilization and detection efficiency. Especially in close-range detection, it significantly reduces blind spots and improves the overall system performance.

[0019] 2. This application also includes a temperature controller, which uses a Peltier element to control the temperature of the pulsed laser to stabilize the emission wavelength and ensure that the wavelength of the output beam of the pulsed laser does not drift. Attached Figure Description

[0020] To more intuitively illustrate the prior art and this application, exemplary drawings are provided below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concept disclosed in this application and the exemplary drawings, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, size ratios, etc. of certain units (components).

[0021] Figure 1 A schematic diagram of a lidar based on a coaxial light-receiving path provided in one embodiment of this application;

[0022] Figure 2 for Figure 1 A schematic diagram of the structure of a medium Newtonian reflecting telescope;

[0023] Figure 3 for Figure 1 A schematic diagram of the coaxial light receiving and transmitting circuit;

[0024] Figure 4 for Figure 1 A schematic diagram of the structure of a medium photon detector;

[0025] Figure 5 for Figure 1 Schematic diagram of a medium-fast optical intensity modulator;

[0026] Figure 6 for Figure 1 A schematic diagram of the hardware correlator.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1. Newtonian reflecting telescope; 101. Telescope tube; 102. Primary mirror; 103. Duplex secondary mirror; 104. First aperture; 105. Second aperture; 2. Temperature controller; 3. Pulsed laser; 4. Beam shaper and expander; 5. First reflecting mirror; 6. Second reflecting mirror; 7. Fiber optic coupler; 8. Fast intensity modulator; 9. Photon detector; 10. Hardware correlator. Detailed Implementation

[0029] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] In the description of this application: unless otherwise stated, "a plurality of" means two or more. The terms "first," "second," "third," etc., in this application are intended to distinguish the objects referred to and do not have any special meaning in terms of technical connotation (e.g., they should not be construed as an emphasis on importance or order). Expressions such as "comprising," "including," and "having" also mean "not limited to" (certain units, components, materials, steps, etc.).

[0031] The terms used in this application, such as "upper," "lower," "left," "right," and "middle," are generally used to indicate the general relative positional relationship for the purpose of intuitive understanding by referring to the accompanying drawings, and are not absolute limitations on the positional relationship in the actual product.

[0032] One embodiment of this application discloses a lidar based on a coaxial light-receiving path, such as... Figures 1-6 As shown, it includes: a Newtonian reflecting telescope 1, a coaxial receiving and receiving optical path and a hardware correlator 10. The Newtonian reflecting telescope 1 includes a telescope tube 101, a primary mirror 102 is provided at the bottom of the telescope tube 101, and a duplex secondary mirror 103 is provided at the opening of the upper part of the telescope tube 101 at an inclined angle of 45 degrees.

[0033] The first mirror 5, the beam shaper 4, and the pulsed laser 3 are arranged sequentially along the axial direction on one side of the mirror barrel 101 corresponding to the duplex sub-mirror 103. The second mirror 6, the fiber optic coupler 7, the fast light intensity modulator 8, and the photon detector 9 are arranged sequentially along the axial direction on the other side of the mirror barrel 101 corresponding to the duplex sub-mirror 103. The first mirror 5 is arranged parallel to the duplex sub-mirror 103, and the second mirror 6 is arranged symmetrically to the duplex sub-mirror 103. The pulsed laser 3 and the photon detector 9 are connected to the hardware correlator 10.

[0034] The coaxial light-receiving path includes a coaxial transmitting light path and a coaxial receiving light path. The Newtonian reflecting telescope 1 adopts a Newtonian reflecting focusing structure. The coaxial transmitting light path and the coaxial receiving light path are connected together through a reflecting mirror and a duplex sub-mirror 103 to achieve coaxiality between the transmitting and receiving light paths. The working process of the coaxial transmitting light path is as follows: the laser beam emitted by the pulsed laser 3 passes through the shaping beam expander 4 and the first reflecting mirror 5 in sequence and enters the mirror tube 101, and is emitted out through one side of the duplex sub-mirror 103. The working process of the coaxial receiving light path is as follows: after various components in the atmosphere scatter the laser beam, it enters the mirror tube 101, and passes through the other side of the duplex sub-mirror 103, the second reflecting mirror 6, the fiber coupler 7, and the fast light intensity modulator 8 in sequence, and then enters the photon detector 9 to be converted into an electrical signal.

[0035] Preferably, it also includes a temperature controller 2, which is connected to the pulsed laser 3 via a Peltier element; the Peltier element is used to control the temperature of the pulsed laser 3 to ensure that the wavelength of the beam output by the pulsed laser 3 does not drift.

[0036] Preferably, the first reflector 5 and the second reflector 6 are aluminum-coated reflectors.

[0037] Preferably, the beam shaper 4 contains a combination of a cylindrical mirror and a beam expander, which is used to shape and expand the laser beam, reduce the divergence angle, and make it suitable for long-distance transmission.

[0038] Preferably, the duplex sub-mirror 103 is used to reflect the emitted beam and focus the laser echo beam. It is the core for realizing the coaxiality of the emitted optical path and the coaxial receiving optical path and maximizing the overlap factor of the two optical paths. Its shape is two or a combination of concave mirror, plane mirror, micromirror array, reflecting prism, dielectric film reflecting mirror, pentaprism, and pentamirror. It can reflect and focus the laser beam in two directions at the same time.

[0039] Preferably, the photosensitive element inside the photon detector 9 is an avalanche diode. Avalanche diodes have two operating modes: linear mode and Geiger mode. Linear mode has low amplification gain, requiring multiple cascaded amplifier stages, increasing the overall size and functionality. In common applications, Geiger mode avalanche diodes and gated avalanche diodes are typically used. The photon detector 9 in this application uses a Geiger mode avalanche diode.

[0040] Preferably, the fast light intensity modulator 8 can be one of an electro-optic modulator, an acousto-optic modulator, or a magneto-optic modulator, used to adjust the intensity of the laser echo signal in real time; when there are too many laser echo photons and the photon detector 9 tends to be saturated, the laser intensity is reduced in real time so that the laser intensity falls within the working range of the photon detector 9, thereby realizing variable attenuation control of the laser intensity.

[0041] Preferably, the hardware correlator 10 is used to acquire the echo time. Typical parameters are: 1ps time resolution and 2-18 channels, capable of receiving multiple input signals simultaneously, and its communication interface includes a USB interface and an Ethernet port.

[0042] Preferably, the optimal temperature range for the pulsed laser 3 is 20°C to 30°C.

[0043] Preferably, such as Figure 2 As shown, the outer wall of the lens barrel 101 is provided with a first opening 104 and a second opening 105 for the coaxial transmitting optical path and the coaxial receiving optical path to pass through, respectively, which can realize efficient input and output of optical signals.

[0044] The aforementioned fiber coupler 7 focuses and couples the laser echo into the optical fiber, facilitating flexible placement of the detection device. The photon detector 9 is a general-purpose single-photon detector that operates in Geiger mode, featuring a simple structure and high sensitivity. The hardware correlator 10 is used to perform correlation analysis on the synchronization signal from the pulsed laser 3 and the laser echo signal from the photon detector 9, achieving high-precision distance measurement. Adjusting the parameters of the correlator allows for adjustment of the system's distance resolution.

[0045] The working principle of this application is as follows: The pulsed laser 3 generates a pulsed laser beam with a variable frequency and emits it into the air through a coaxial transmission optical path. Various molecules and microparticles of different sizes in the air will scatter the laser beam. The beam is then received by the coaxial receiving optical path and focused and coupled into the optical fiber through the fiber coupler 7. After the intensity is modulated by the fast intensity modulator 8, it is transmitted to the photon detector 9. The latter outputs an electrical pulse signal that enters the hardware correlator 10. Combined with the synchronization signal of the pulsed laser 3, the arrival time of the laser echo signal is accurately measured, and the accurate distance can be calculated accordingly.

[0046] In summary, this application employs the principle of laser reflection to detect meteorological elements. It emits a laser beam, measures the intensity and duration of the laser echo, and then detects the distance distribution of weather elements such as clouds, microdroplets, microparticles, fog, and haze. This allows for better real-time, high-precision distance measurement of meteorological elements, solving the problem of insufficient spatial resolution in traditional lidar systems, which severely impacts subsequent data use and data processing and modeling. It has at least the following advantages:

[0047] 1. The use of a Newtonian reflecting telescope for coaxial light-receiving path design significantly improves the overlap factor of the emitted and received beams, ensuring measurement accuracy. At the same time, the Newtonian reflecting telescope has advantages such as large receiving aperture, short optical path length, simple structure, and convenient adjustment.

[0048] 2. A fast light intensity modulator is used to control the intensity of the laser echo signal in real time. During the test time, the transmission intensity is linearly adjusted from 5% to 100%, taking into account the measurement of both near and far objects. The measured blind zone is less than 2 meters. This solves the problem that the laser echo of near targets is strong and has a large number of photons, which can easily lead to saturation or even damage to the photon detector, while the laser echo of distant targets is weak, has a small number of photons, and has a low signal-to-noise ratio, resulting in a large measurement range that exceeds the instrument's response range.

[0049] 3. A temperature controller is also provided because the fast intensity modulator is sensitive to changes in laser wavelength, so the temperature controller is used to stabilize the emission wavelength of the pulsed laser.

[0050] 4. The laser echo signal is input to the photon detector to obtain the corresponding electrical signal. The echo electrical signal and the synchronization signal of the pulsed laser are connected to the hardware correlator, which has a time resolution of 1 ps and a corresponding distance resolution of 0.33 mm. The hardware correlator has multiple input channels, can process multiple signals simultaneously, and has channel expansion capability, allowing for appropriate expansion of the number of channels. The communication interfaces used are USB and Ethernet. Using the hardware correlator can significantly reduce the amount of data calculation on the host computer and speed up the system response. After integrating the scanning beam hardware, the entire lidar can be expanded into an imaging lidar. This lidar is suitable for cloud height measurement, measurement of microdroplets, microparticles, fog, haze, etc., and distance measurement of long-distance objects.

[0051] The technical features of the above embodiments can be combined in any way (as long as there is no contradiction in the combination of these technical features). For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; these embodiments not explicitly written should also be considered to be within the scope of this specification.

Claims

1. A laser radar based on a coaxial transmitting and receiving optical path, characterized by include: The Newtonian reflecting telescope includes a coaxial receiving and receiving optical path and a hardware correlator. The Newtonian reflecting telescope includes a telescope tube, a primary mirror at the bottom of the telescope tube, and a duplex secondary mirror at a 45-degree angle at the opening of the upper part of the telescope tube. The mirror barrel is provided with a first reflecting mirror, a beam shaper and a pulsed laser arranged sequentially along the axial direction on one side corresponding to the duplex sub-mirror. On the other side corresponding to the duplex sub-mirror, the mirror barrel is provided with a second reflecting mirror, a fiber coupler, a fast intensity modulator and a photon detector arranged sequentially along the axial direction. The first reflecting mirror is arranged parallel to the duplex sub-mirror, and the second reflecting mirror is arranged symmetrically to the duplex sub-mirror. The pulsed laser and the photon detector are connected to the hardware correlator. The coaxial optical path includes a coaxial transmitting optical path and a coaxial receiving optical path. The laser beam emitted by the pulsed laser enters the lens tube through the first reflecting mirror, and is then emitted through the duplex sub-mirror to form the coaxial transmitting optical path. Various components in the atmosphere scatter the laser beam, which then enters the lens tube and passes through the duplex sub-mirror, the second reflecting mirror, the fiber coupler, and the fast light intensity modulator in sequence before entering the photon detector and being converted into an electrical signal to form the coaxial receiving optical path.

2. The laser radar based on coaxial transmitting and receiving optical path according to claim 1, characterized in that, It also includes a temperature controller, which is connected to the pulsed laser via a Peltier element.

3. The laser radar based on coaxial transmitting and receiving optical path according to claim 1, characterized in that, The duplex mirror is two or a combination of concave mirror, plane mirror, micromirror array, reflecting prism, dielectric film reflecting mirror, pentaprism, and pentamirror.

4. The lidar based on a coaxial light-receiving path according to claim 1, characterized in that, The first and second reflectors are aluminum-coated reflectors.

5. The laser radar based on coaxial transmitting and receiving optical path according to claim 1, characterized in that, The pulsed laser and the first reflector are provided with a beam shaper and expander, the beam shaper and expander being a combination of a cylindrical mirror and a beam expander.

6. The laser radar based on coaxial transmitting and receiving optical paths according to claim 1, characterized in that, The photosensitive element inside the photon detector is an avalanche diode operating in Geiger mode.

7. The lidar based on a coaxial light-receiving path according to claim 1, characterized in that, The fast light intensity modulator is one of an electro-optic modulator, an acousto-optic modulator, or a magneto-optic modulator.

8. The lidar based on a coaxial light-receiving path according to claim 1, characterized in that, The hardware correlator has a 1ps time resolution and 2-18 channels, and its communication interfaces include a USB interface and an Ethernet port.

9. The laser radar based on coaxial transmitting and receiving optical path according to claim 1, characterized in that, The temperature range of the pulsed laser is 20℃~30℃.

10. The laser radar based on coaxial transmitting and receiving optical path according to claim 1, characterized in that, The outer wall of the lens barrel has a first opening and a second opening for the coaxial emitting optical path and the coaxial receiving optical path to pass through, respectively.

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