Integrated laser distance measuring device

Abstract

The present invention provides an integrated laser ranging device, which mainly includes a laser resonant cavity, a controller, a photodetector, a coaxial transmitting and receiving unit and a controller. A total reflection mirror and a coupling output mirror form a laser resonant cavity. In the laser resonant cavity, a phase wave plate, a laser gain module, an electro-optical Pockels cell and a polarization beam splitter are sequentially arranged from the total reflection mirror to the coupling output mirror. The coaxial transmitting and receiving unit is arranged in the laser emitting direction outside the laser resonant cavity. The present invention couples the echo laser into the laser gain module of the integrated laser ranging device for double-pass amplification through the integrated design of a solid laser and a laser ranging unit, so as to realize high-power optical amplification of the echo laser signal by the laser gain module. At the same time, the echo laser cleverly shares the same laser gain module with the transmitting laser in a time-sharing manner, effectively compressing the volume of the integrated laser ranging device, which is conducive to its promotion and application in vehicle-mounted, airborne and satellite-mounted environments.

Description

Technical Field

[0001] The invention relates to the technical field of laser distance measurement, and in particular to an integrated laser distance measurement device with echo laser gain. Background Art

[0002] Laser rangefinders have broad application prospects in many fields such as industry, national defense, and scientific research. They are suitable for mobile platforms such as vehicles, airborne, and satellites, and have attracted much attention at home and abroad. Among them, LD-pumped electro-optical Q-switched lasers have significant advantages such as short pulse width, high peak power, good beam quality, compact structure, and high cost-effectiveness, and are often used as light sources for laser rangefinders. High signal-to-noise ratio and large detection distance are the core evaluation indicators of laser rangefinders, and miniaturized and lightweight laser rangefinders are the objective requirements of application scenarios. How to balance ranging performance and volume weight is the research focus of laser rangefinders.

[0003] In order to improve the detection distance and signal-to-noise ratio of laser rangefinders, the commonly used methods include: improving the output capacity of the laser, improving the aperture of the rangefinder's transmitting system, improving the aperture of the rangefinder's receiving system, and improving the sensitivity and data processing capabilities of the photoelectric detector. The above methods will increase the volume and weight of the laser rangefinder system, increase the cost, and limit the scope of application. On the basis of not significantly increasing the volume and weight of the system, by optimizing the integrated design of the laser and the rangefinder unit, and improving the detection distance and signal-to-noise ratio of the laser rangefinder, it will help promote the application of laser rangefinders in vehicle-mounted, airborne, satellite-mounted and other application scenarios. Summary of the invention

[0004] In order to solve the above problems, the present invention provides an integrated laser ranging device. Through the integrated design of a solid-state laser and a laser ranging unit, the echo laser is coupled to a laser gain module of the integrated laser ranging device for double-pass amplification, thereby realizing high-magnification optical amplification of the echo laser signal by the laser gain module. At the same time, the echo laser cleverly shares the same laser gain module with the emitted laser in a time-sharing manner, thereby effectively compressing the volume of the integrated laser ranging device.

[0005] The integrated laser distance measuring device provided by the present invention comprises:

[0006] Total reflection mirror, coupling output mirror, coaxial transmitting and receiving unit, photodetector and controller, wherein:

[0007] The total reflection mirror and the coupling output mirror form a laser resonant cavity, in which a phase wave plate, a laser gain module, an electro-optical Pockels cell and a polarization beam splitter are arranged in sequence from the total reflection mirror to the coupling output mirror.

[0008] Among them, the laser gain module provides laser gain for the echo laser and the excitation emission laser, the electro-optical Pockels cell is used to dynamically adjust the phase delay of the emission laser and the echo laser, and the polarization beam splitter is used to transmit the P-polarized laser and reflect the S-polarized laser;

[0009] During the laser emission process, the phase wave plate, electro-optical Pockels cell and polarization beam splitter work together to realize the Q-switching function of the laser; during the laser echo process, the polarization beam splitter, laser gain module and phase wave plate work together to realize the double-pass optical amplification function of the echo laser;

[0010] The coaxial transmitting and receiving unit is used to compress the emission angle of the emitted laser emitted by the coupling output mirror, and at the same time, the coaxial transmitting and receiving unit is used to converge the received echo laser;

[0011] The photodetector receives the S-polarized echo laser reflected by the polarization beam splitter, and converts the S-polarized echo laser signal into an electrical signal.

[0012] The controller is a single chip microcomputer, which is used to start and interrupt the laser resonant cavity to excite the laser pulse, to record the time of the peak value of the emitted laser pulse and the time of the first detection of the echo laser, and to calculate the distance between the integrated laser ranging device and the target to be measured.

[0013] Preferably, the total reflection mirror is a concave reflection mirror coated with a dielectric film, which forms a stable cavity structure with the coupling output mirror, and the total reflection mirror is based on K14 glass.

[0014] Preferably, the phase wave plate is a 1 / 4 wave plate, and the phase angle of light passing through the 1 / 4 wave plate once is delayed by 45°. After the light is transmitted back and forth twice in the laser resonant cavity, the S polarized light becomes P polarized light.

[0015] Preferably, applying a 1 / 4 wave voltage to the electro-optic Pockels cell is equivalent to a 1 / 4 wave plate, and the phase angle of light passing through the electro-optic Pockels cell once is delayed by 45°; the electro-optic Pockels cell without applying voltage is equivalent to a plane crystal, and has no effect on the phase of the passing laser. The phase wave plate and the electro-optic Pockels cell combined are equivalent to a 1 / 2 wave plate, which is equivalent to a 1 / 2 wave plate. After the laser passes through the phase wave plate and the electro-optic Pockels cell, the linear polarization direction remains unchanged, and the photons resonate in the resonant cavity to form a pulsed laser output.

[0016] Preferably, the electro-optical Pockels cell uses potassium dihydrogen phosphate crystal, both ends of the electro-optical Pockels cell are coated with anti-reflection films, the extinction ratio TP:TS of the electro-optical Pockels cell is greater than 1000:1, TP represents the transmittance of P polarized light, TS represents the transmittance of S polarized light, and the 1 / 4 wave voltage is 3.3 kV.

[0017] Preferably, the polarization beam splitter adopts a polarization plate beam splitter with fused quartz as the substrate, the aperture of the polarization beam splitter is 20 mm, the working wavelength of the polarization beam splitter is 1064 nm, and when the incident angle of the laser incident on the polarization beam splitter is 45°, the extinction ratio TP:TS is greater than 10000:1.

[0018] Preferably, the coupling-out mirror adopts a quartz glass substrate, and the transmittance of the coupling-out mirror to laser is 20%-60%.

[0019] Preferably, the photodetector is an uncooled avalanche photodetector.

[0020] Preferably, the formula for calculating the distance between the integrated laser ranging device and the target to be measured is:

[0021] S = (t2 - t1) × c / 2;

[0022] Wherein, S represents the distance between the integrated laser ranging device and the target to be measured, t1 represents the time when the photoelectric detector first detects the pulse peak of the emitted laser, and t2 represents the time when the photoelectric detector first detects the echo laser.

[0023] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0024] 1. The present invention effectively solves the problems of weak echo signal and low detection signal-to-noise ratio of existing laser ranging devices. By controlling the polarization state of the echo laser, time-sharing optical amplification of the echo laser in the laser gain module of the laser is realized, which significantly improves the optical intensity of the echo signal.

[0025] 2. The present invention integrates the laser and the ranging unit into an integrated design without adding any additional optical elements, which effectively reduces the volume and weight of the laser ranging device, is conducive to its promotion and application in vehicle-mounted, airborne, and satellite-mounted environments, and laser ranging devices of various wavelengths can be formed by replacing laser devices of other wavelengths. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a component distribution diagram of an integrated Nd:YAG laser distance measuring device provided according to an embodiment of the present invention;

[0027] Figure 2 is a working logic diagram of a controller provided according to an embodiment of the present invention.

[0028] Reference numerals include:

[0029] Total reflection mirror 1, 1 / 4 wave plate 2, laser gain module 3, electro-optical Pockels cell 4, polarization beam splitter 5, coupling output mirror 6, controller 7, photodetector 8, coaxial transmitting and receiving unit 9, transmitting laser 10, echo laser 11. DETAILED DESCRIPTION

[0030] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0032] This embodiment is described by taking an integrated Nd:YAG laser ranging device with a wavelength of 1064 nm as an example. According to application requirements, laser devices with other wavelengths can be replaced to form integrated laser ranging devices of various wavelengths.

[0033] Figure 1 The component distribution of the integrated Nd:YAG laser ranging device provided according to an embodiment of the present invention is shown.

[0034] like Figure 1 As shown, the integrated Nd:YAG laser ranging device includes: a total reflection mirror 1, a quarter wave plate 2, a laser gain module 3, an electro-optical Pockels cell 4, a polarization beam splitter 5, a coupling output mirror 6, a controller 7, a photodetector 8 and a coaxial transmitting and receiving unit 9. The total reflection mirror 1 and the coupling output mirror 6 form a laser resonant cavity. In the laser resonant cavity, the quarter wave plate 2, the laser gain module 3, the electro-optical Pockels cell 4 and the polarization beam splitter 5 are sequentially arranged from the total reflection mirror 1 to the coupling output mirror 6. In addition, an integrated Nd:YAG laser ranging device controller is also provided. The coaxial transmitting and receiving unit 9 is arranged in the direction of laser emission outside the laser resonant cavity, wherein:

[0035] The total reflection mirror 1 is the back cavity mirror of the laser resonant cavity. The total reflection mirror 1 is based on K14 glass, has a diameter of 12 mm, a curvature radius of 300 mm, and is coated with a dielectric film. The reflectivity of the laser with a wavelength of 1064 nm is ≥99.9%.

[0036] The 1 / 4 wave plate 2 is a phase delay element of the laser resonant cavity, and the phase delay angle is 45°. The 1 / 4 wave plate 2 adopts a zero-order quartz wave plate, with an operating wavelength of 1064nm and an aperture of 12mm.

[0037] Laser gain module 3 provides laser gain for the emission laser and the echo laser in time-sharing. Laser gain module 3 uses a LD side-pumped Nd:YAG module. The maximum peak pump power of a single module is 1kW. The size of the Nd:YAG crystal rod contained in it is Represents the outer diameter of the crystal rod, with a doping concentration of 1%.

[0038] The electro-optical Pockels cell 4 is a laser phase delay element and laser Q-switching device in the laser resonant cavity. The electro-optical Pockels cell 4 uses potassium dihydrogen phosphate crystals, and both ends are coated with anti-reflection films. The anti-reflection film has an increased transmission effect on lasers with a wavelength of 1064nm. The aperture of the electro-optical Pockels cell 4 is 9mm, the extinction ratio TP:TS>1000:1, and the 1 / 4 wave voltage is 3.3kV.

[0039] Polarization beam splitter 5 is an intracavity laser polarization selective device. Polarization beam splitter 5 uses a polarization plate beam splitter based on fused quartz, with an aperture of 20mm and an operating wavelength of 1064nm. Polarization beam splitter 5 has high transmittance to P polarization component and high reflection to S polarization component. When the laser incident angle is 45°, the extinction ratio TP:TS>10000:1.

[0040] The coupling output mirror 6 is the output mirror of the laser resonant cavity. The coupling output mirror 6 has a quartz glass substrate and an aperture of 20 mm. The transmittance of the coupling output mirror 6 to the laser with a wavelength of 1064 nm is 20%-60%.

[0041] The controller 7 is a single chip microcomputer, which has the functions of starting and interrupting the laser resonant cavity to excite the laser pulse, recording the time and calculating the distance to the target to be measured.

[0042] Photodetector 8 uses an uncooled avalanche photodetector with a noise equivalent power of The response time is ≤1ns, and it has the ability to detect incident lasers quickly and with high sensitivity, and convert the detected optical signals into voltage signals.

[0043] The coaxial transmitting and receiving unit 9 adopts a Galilean beam expander lens group, the aperture of the incident end is 12 mm, and the beam expansion ratio is 8 times, which is used for transmitting and receiving lasers.

[0044] The emitted laser 10 represents a laser with a wavelength of 1064 nm emitted by an integrated Nd:YAG laser ranging device. The repetition frequency of the emitted laser 10 is 20 Hz, the single pulse energy is ≥200 mJ, the pulse width is ≤7 ns, and the polarization direction is P polarization.

[0045] The echo laser 11 represents the portion of the laser light with distance information that is reflected back by the target after the emitted laser light 10 is emitted to the target.

[0046] The specific working process of this embodiment:

[0047] In the first step, the quarter wave plate 2, the electro-optical Pockels cell 4 and the polarization beam splitter 5 cooperate to realize the Q-switching function of the integrated Nd:YAG laser ranging device. The specific process is as follows:

[0048] At time t0, the controller 7 sends a start signal to the electro-optical Pockels cell 4. At the beginning, no voltage is applied to the electro-optical Pockels cell 4, which is equivalent to a plane crystal and has no effect on the phase of the laser passing through. The phase angle of the emitted laser 11 passing through the 1 / 4 wave plate 2 once is delayed by 45°. After passing through the 1 / 4 wave plate 2 twice, the phase angle of the emitted laser 10 is delayed by 90°. After the laser is transmitted back and forth once in the resonant cavity, it changes from a P-polarized laser to an S-polarized laser. The S-polarized laser cannot pass through the polarization beam splitter 5. At this time, there is no laser resonance in the cavity, and a large number of inverted particles are stored in the laser gain module.

[0049] The controller 7 sends a start signal to the electro-optical Pockels cell 4, a 1 / 4 wave voltage is added to the electro-optical Pockels cell 4, the electro-optical Pockels cell 4 is equivalent to a 1 / 4 wave plate, the combination of the electro-optical Pockels cell 4 and the 1 / 4 wave plate 2 is equivalent to a 1 / 2 wave plate, the phase angle of the laser after passing through the 1 / 4 wave plate 2 and the electro-optical Pockels cell 4 once is delayed by 90°, and the S-polarized laser is converted into a P-polarized laser. At this time, the P-polarized laser can efficiently pass through the polarization beam splitter 5, and a large number of inverted particles are stored in the laser gain module 3 and output in the form of giant laser pulses to form an emitted laser 11.

[0050] In the second step, the polarization beam splitter 5, the controller 7 and the photodetector 8 cooperate to record the laser emission time t1. The specific working process is as follows:

[0051] Since the polarization beam splitter 5 is a non-ideal optical element, its reflectivity for P-polarized laser is greater than 0.001%. A very small amount of P-polarized laser will be reflected by the polarization beam splitter 5 to the photodetector 8. The photodetector 8 receives the laser signal and sends it to the controller 7. The controller 7 records the pulse establishment process of the emitted laser 11. When the pulse peak of the emitted laser 11 is detected, the controller 7 records the laser emission time t1 and sends a termination signal to the electro-optical Pockels cell 4 to interrupt the laser resonance. The inverted particle number continues to accumulate in the cavity, and the emitted laser 11 is emitted through the coaxial transmitting and receiving unit.

[0052] In the third step, the polarization beam splitter 5, the laser gain module 3 and the quarter wave plate 2 cooperate to realize the double-pass optical amplification function of the echo laser 11. The specific process is as follows:

[0053] The emitted laser 10 is shot onto the target to be measured, and part of the emitted laser 10 is reflected back by the target to be measured to form an echo laser 11, which is P polarized. The echo laser 11 passes through the coaxial transmitting and receiving unit 9, the coupling output mirror 6, the polarization beam splitter 5 and the electro-optical Pockels cell 4 in sequence, and the electro-optical Pockels cell 4 is in a non-voltage state at this time. The echo laser 11 enters the laser gain module 3 for time-sharing optical amplification, and then passes through the 1 / 4 wave plate 2 to reach the total reflection mirror 1, is reflected again by the total reflection mirror 1, and then passes through the 1 / 4 wave plate 2. At this time, the echo laser 11 changes from the P polarization state to the S polarization. The S polarized echo laser enters the gain module 3, and after a second time-sharing optical amplification, it passes through the unpressurized electro-optical Pockels cell 4 and is shot to the polarization beam splitter 5.

[0054] Step 4: The beam splitter 5, controller 7 and photodetector 8 record the echo time t2 and calculate the distance of the target. The specific process is as follows:

[0055] The echo laser 11 incident on the beam splitter 5 is reflected and detected by the photodetector 8, and the controller 7 records the echo time t2 and calculates the distance of the measured target, thus completing the laser emission and laser ranging.

[0056] Figure 2 The working logic of the controller provided according to the embodiment of the present invention is shown.

[0057] like Figure 2 As shown, the electro-optical Pockels cell 4, the controller 7 and the photodetector 8 cooperate to realize the timing control and distance calculation of the integrated Nd:YAG laser ranging device.

[0058] The distance calculation formula of the measured target is: S = (t2-t1) × c / 2, where S is the distance of the measured target and c is the speed of light.

[0059] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0060] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An integrated laser ranging device, characterized in that: include: Total reflection mirror, coupling output mirror, coaxial transmitting and receiving unit, photodetector and controller, wherein: The total reflection mirror and the coupling output mirror form a laser resonant cavity, in which a phase wave plate, a laser gain module, an electro-optical Pockels cell and a polarization beam splitter are sequentially arranged from the total reflection mirror to the coupling output mirror. The laser gain module provides laser gain for the echo laser and the excitation emission laser, the electro-optical Pockels cell is used to dynamically adjust the phase delay of the emission laser and the echo laser, and the polarization beam splitter is used to transmit the P-polarized laser and reflect the S-polarized laser; During the laser emission process, the phase wave plate, the electro-optical Pockels cell and the polarization beam splitter cooperate to realize the Q-switching function of the laser; during the laser echo process, the polarization beam splitter, the laser gain module and the phase wave plate cooperate to realize the double-pass optical amplification function of the echo laser; The coaxial transmitting and receiving unit is arranged in the direction of laser emission outside the laser resonant cavity, and is used to compress the emission angle of the emitted laser emitted by the coupling output mirror, and at the same time, the coaxial transmitting and receiving unit is used to converge and receive the echo laser; The photodetector receives the S-polarized echo laser reflected by the polarization beam splitter, and the photodetector converts the S-polarized echo laser signal into an electrical signal; The controller is a single chip microcomputer, which is used to start and interrupt the laser resonant cavity to excite the laser pulse, to record the time of the peak value of the emitted laser pulse and the time when the echo laser is first detected, and to calculate the distance between the integrated laser ranging device and the target to be measured.

2. The integrated laser distance measuring device according to claim 1, characterized in that: The total reflection mirror is a concave reflection mirror coated with a dielectric film, which forms a stable cavity structure with the coupling output mirror. The total reflection mirror uses K14 glass as a substrate.

3. The integrated laser distance measuring device according to claim 1, characterized in that: The phase wave plate is a 1 / 4 wave plate. The phase angle of light passing through the 1 / 4 wave plate once is delayed by 45°. After the light is transmitted back and forth twice in the laser resonant cavity, the S polarized light becomes P polarized light.

4. The integrated laser distance measuring device according to claim 3, characterized in that: Applying a 1 / 4 wave voltage on the electro-optic Pockels cell is equivalent to a 1 / 4 wave plate, and the phase angle of light passing through the electro-optic Pockels cell once is delayed by 45°; the electro-optic Pockels cell without applying voltage is equivalent to a plane crystal, and has no effect on the phase of the passing laser. The phase wave plate and the electro-optic Pockels cell combined are equivalent to a 1 / 2 wave plate, and the linear polarization direction of the laser light remains unchanged after passing through the phase wave plate and the electro-optic Pockels cell back and forth, and the photons resonate in the resonant cavity to form a pulsed laser output.

5. The integrated laser distance measuring device according to claim 4, characterized in that: The electro-optical Pockels cell adopts potassium dihydrogen phosphate crystal, and both ends of the electro-optical Pockels cell are coated with anti-reflection films. The extinction ratio TP:TS of the electro-optical Pockels cell is greater than 1000:1, TP represents the transmittance of P polarized light, TS represents the transmittance of S polarized light, and the 1 / 4 wave voltage is 3.3kV.

6. The integrated laser distance measuring device according to claim 1, characterized in that: The polarization beam splitter adopts a polarization plate beam splitter with fused quartz as the substrate. When the incident angle of the laser incident on the polarization beam splitter is 45°, the extinction ratio TP:TS is greater than 10000:

1.

7. The integrated laser distance measuring device according to claim 1, characterized in that: The coupling output mirror adopts a quartz glass substrate, and the transmittance of the coupling output mirror to laser is 20%-60%.

8. The integrated laser distance measuring device according to claim 1, characterized in that: The photoelectric detector is an uncooled avalanche photoelectric detector.

9. The integrated laser distance measuring device according to claim 1, characterized in that: The formula for calculating the distance between the integrated laser ranging device and the target to be measured is: S = (t2 - t1) × c / 2; Wherein, S represents the distance between the integrated laser ranging device and the target to be measured, t1 represents the time when the photoelectric detector first detects the pulse peak of the emitted laser, and t2 represents the time when the photoelectric detector first detects the echo laser.

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