A high-precision high-energy laser polarization state detection system

Abstract

The application relates to a high-precision high-energy laser polarization state detection system and relates to the field of laser radars, which comprises a focusing lens, a collimating lens, a Glan laser polarizer, a fiber coupling lens and a single-photon detector. The focusing lens focuses the light path to be detected to the collimating lens. The collimating lens performs beam shrinking on a return light beam. The shrunk light beam is modulated by the Glan laser polarizer to the polarization direction of the return light. Finally, the modulated light beam is incident into the single-photon detector. The application has the advantages that different polarization state lasers are used to obtain multi-piece multi-cycle ranging data, so that accurate ranging can be realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser radar, in particular to a high-precision high-energy laser polarization state detection system. BACKGROUND

[0002] As an advanced tool for detecting potential targets, laser radar has a wide range of applications in both military and civilian systems. Its basic working principle is to emit laser signals in a directional manner into the space to be detected. If there is a potential target in the space, the emitted laser signals will be diffusely reflected back to the radar base station and detected by the receiving device. Further, according to the emission angle, time, frequency of the laser signal and the time and frequency of the received reflected signal, the laser radar system can determine the position, distance, speed and shape of the potential target. Currently, laser radar technology is facing technical bottlenecks in sensitivity, resolution, anti-interference, anti-stealth capability, etc., and cannot meet the growing detection needs.

[0003] Therefore, in view of the above shortcomings, it is necessary to provide a high-precision high-energy laser polarization state detection system. SUMMARY

[0004] TECHNICAL SOLUTION

[0005] The present application provides a high-precision high-energy laser polarization state detection system, which comprises a focusing lens, a collimating lens, a Glan laser polarizer, a fiber coupling lens and a single photon detector. The focusing lens focuses the detected light path to the collimating lens. The collimating lens shrinks the beam. The shrunk beam is modulated by the Glan laser polarizer to the polarization direction of the echo. Finally, the modulated beam is incident into the single photon detector. The effective focal length of the single photon detector receiving the light path satisfies:

[0006]

[0007] The aperture of the receiving mirror;

[0008] The focal length

[0009] The half-angle of the incident beam divergence angle.

[0010] As a further description of the present application, preferably, the single photon detector uses a low-temperature superconducting nanowire detector.

[0011] As a further description of the present application, preferably, a quarter-wave plate and a half-wave plate are further provided between the Glan laser polarizer and the collimating lens. The Glan laser polarizer, the quarter-wave plate and the half-wave plate are arranged on a rotary table with a travel of 360° and are located in the same vertical plane.

[0012] As a further illustration of the present application, preferably, an energy meter is arranged outside the exit end of the G-Laser polarizer to determine the angle value corresponding to the energy peak value through the angle of rotation of the quarter-wave plate and the half-wave plate after the energy peak value is detected.

[0013] As a further illustration of the present application, preferably, an X-shaped mounting frame is arranged below the half-wave plate, the middle part of the straight rod of the mounting frame is provided with a slide, the left block and the right block are fixedly connected in the slide at intervals, a left slot is formed in the middle part of the left block, two right slots are formed in the right block at intervals, the distance between the two right slots is greater than or equal to the width of the left slot, and the slide is fixedly connected to the bottom of the turntable below the half-wave plate, and two left positioning blocks are fixedly connected to the slide at intervals.

[0014] As a further illustration of the present application, preferably, optical devices are slidably connected to the four sides of the mounting frame, the optical devices are fixedly connected to different slides, the right positioning blocks are fixedly connected to the bottom of the slide on one side of the straight rod, and the left positioning blocks are fixedly connected to the bottom of the slide on the other side of the straight rod, the right positioning blocks pass through the left slot and abut against one side of the right block so that the optical devices are on the same optical axis as the quarter-wave plate.

[0015] As a further illustration of the present application, preferably, the slides are fixedly connected to the bottom of the slide, the width of the gyrostat is the same as the width of the slide, the length of the gyrostat embedded in the slide is less than the depth of the slide, and the left positioning blocks and the right positioning blocks are fixedly connected below the gyrostat.

[0016] As a further illustration of the present application, preferably, the left positioning blocks, the right positioning blocks and the gyrostat are made of metal materials, and magnets are embedded on one side of the left block and the right block, the left positioning blocks and the right positioning blocks abut against the magnets when they move to the left block and the right block.

[0017] As a further illustration of the present application, preferably, the half-wave plate and other optical devices are fixed on the slide through bolts, and the mounting frame and the quarter-wave plate are fixed on the experimental table with multiple bolt holes through bolts.

[0018] (Three) beneficial effects

[0019] The above technical scheme of the present application has the following advantages:

[0020] The present application designs a new laser echo receiving system, which can not only detect the laser echo, but also replace the single-photon detector with an energy meter through time-sharing public use, so as to measure the wave plate angle when the laser energy appears a peak value. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a laser echo receiving system optical path diagram of the present application;

[0022] Figure 2 is a laser polarization detection system diagram of the present application;

[0023] Figure 3 is a quarter wave plate and half wave plate installation effect diagram of the present application;

[0024] Figure 4 is a mounting rack structural diagram of the present application;

[0025] Figure 5 is a left positioning block and right positioning block installation position diagram of the present application;

[0026] Figure 6 is a left positioning block and left stop block abutting side view of the present application;

[0027] Figure 7 is a right positioning block and right stop block abutting side view of the present application;

[0028] Figure 8 is a left positioning block and left stop block abutting top view of the present application;

[0029] Figure 9 is a right positioning block and right stop block abutting top view of the present application.

[0030] In the figure: 1, quarter wave plate; 11, half wave plate; 2, Glan laser polarizer; 3, fiber coupling lens; 4, energy meter; 5, focusing lens; 6, collimating lens; 7, experiment table; 8, mounting rack; 81, fixing bolt; 82, slide; 83, left stop block; 831, left slot; 84, right stop block; 841, right slot; 85, magnet; 9, slide; 91, direction stabilizing seat; 92, left positioning block; 93, right positioning block. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0032] A high-precision high-energy laser polarization state detection system, such as Figure 1The shown, including focusing lens 5, collimating lens 6, quarter-wave plate 1, Glan laser polarizer 2, fiber coupling lens 3 and single photon detector, single photon detector uses low temperature superconducting nanowire detector (SNSPD), the main reason for using this detector is that the detector has very high detection efficiency (~ 30%) at 1064nm waveband; The dark count noise is low (1000pps). Unlike the single photon detector used at 532nm wavelength, SNSPD uses a multimode fiber space optical coupling mode to receive the echo, and the optical parameter design of the receiving optical system needs to consider the multimode fiber parameter matching of SNSPD.

[0033] The effective focal length of the 1064nm receiving optical path is calculated as follows:

[0034] Select a fiber with a core diameter of 100 microns and a numerical aperture of 0.22 without an adapter

[0035]

[0036]

[0037] Take , the incident beam divergence angle half angle is (12.7082°). The system equivalent focal length should meet:

[0038]

[0039] The aperture of the receiving mirror is

[0040] The focal length is

[0041] The incident beam divergence angle half angle is

[0042] For a receiving telescope with a receiving aperture of 1050mm, the receiving aperture is 1050mm, and the receiving aperture is 1050mm. 2350mm. Therefore, the designed optical system for 100μm fiber has a comprehensive equivalent focal length of 2354mm.

[0043] In actual measurement, the detected light path is focused through focusing lens 5 to collimating lens 6, collimating lens 5 shrinks the echo beam, the shrunk beam is incident to the quarter-wave plate, the polarization direction of the echo is modulated through the Glan laser polarizer 2, and finally the modulated beam is incident into the single photon detector.

[0044] As Figure 2As shown, the Glan laser polarizer 2 is a prism specially used in high-energy lasers, with two escape windows on the side. The prism has a very high laser damage threshold and a higher extinction ratio than ordinary Glan-Taylor prisms. A beam of unpolarized light is input to obtain a linearly polarized light. Compared with other polarizing plates (such as polarizing plates), it has higher transmittance and polarization purity. Between the collimating lens 6 and the Glan laser polarizer 2, a half-wave plate 11 is added, and the Glan laser polarizer 2 and the quarter-wave plate 1 and the half-wave plate 11 are arranged on a 360° rotation table and are located in the same vertical plane. An energy meter 4 is arranged outside the exit end of the Glan laser polarizer 2, which can detect the polarization state of the input laser after use. The 360° rotation table is mounted on a motorized displacement table, and the displacement table is moved to switch between 532nm and 1064nm laser emission. The polarization state detection processes of the two wavelengths of laser emission are the same, and the rotation table angle values corresponding to different polarization directions of the Glan laser polarizer 2, the half-wave plate 11 and the quarter-wave plate 1 need to be measured respectively. The measurement process is as follows:

[0045] 1. Control the rotation table to rotate from 0° to 360° at a step of 10°, and collect the energy meter 4 readings at each rotation step to find the angle value corresponding to the energy peak value;

[0046] 2. Rotate near the angle value at a step of 5° and collect the energy meter 4 readings to find the angle value corresponding to the energy peak value;

[0047] 3. Rotate near the angle value at a step of 1° and collect the energy meter 4 readings to find the angle value corresponding to the energy peak value. When the rotation table is at the angle value, the emitted laser is linearly polarized.

[0048] According to the measurement results, when the fast axes of the half-wave plate 11 and the quarter-wave plate 1 are consistent, the emitted laser is linearly polarized with a polarization direction perpendicular to the optical platform or parallel to the optical platform. When the angle between the fast axes of the quarter-wave plate 1 and the half-wave plate 11 is 45° or 22.5°, the emitted laser is circularly polarized or elliptically polarized. When detecting circularly polarized and elliptically polarized light, the half-wave plate 11 and the quarter-wave plate 1 are fixed, and the Glan laser polarizer 2 is rotated 360° and the energy meter 4 readings are recorded.

[0049] The detection processes of 1064nm circularly polarized and elliptically polarized light are the same as those of 532nm. First, rotate the half-wave plate 11 and the quarter-wave plate 1 through the rotation table to make the emitted laser linearly polarized, and then rotate the quarter-wave plate 1 by 45° or 22.5° and record the energy meter readings by rotating the Glan laser polarizer 2.

[0050] Among them, in combination with Figure 3 , Figure 4, quarter-wave plate 1 and energy meter 4 and other devices are fixed on the experimental table 7 with multiple bolt holes through bolts, the half-wave plate 11 is provided with an X-shaped mounting bracket 8, the middle part of the mounting bracket 8 is a straight rod, the two sides of the straight rod are bifurcated support rods, and the two ends of the straight rod are fixed with the experimental table 7 through fixing bolts 81. The support rods and the straight rod are both provided with slideways 82, the slideways 82 are slidably connected with sliding seats 9, and the optical devices such as the half-wave plate 11 can be arranged on the sliding seats 9 through bolts, so that a maximum of four groups of optical devices can be arranged on the mounting bracket 8, when a group of optical devices needs to be used, the sliding seat 9 provided with the group of optical devices on the support rod can be slid to the straight rod, and after the experiment is completed, the sliding seat 9 is reset first, and then other optical devices are retrieved according to the experimental requirements. The scheme can retrieve the half-wave plate 11 in cooperation with the quarter-wave plate 1, and the energy meter 4 can also be installed on the sliding seat 9 to directly detect laser data.

[0051] In combination with Figure 5 , Figure 6 and Figure 7 , the left block 83 and the right block 84 are fixed in the slideway 82 of the straight rod at intervals, a left slot 831 is formed in the middle part of the left block 83, and two right slots 841 are formed in the right block 84 at intervals, and the distance between the two right slots 841 is greater than or equal to the width of the left slot 831. The bottom of each sliding seat 9 on one side of the straight rod is fixed with a right positioning block 93, the right positioning block 93 is a square block, and the width of the right positioning block 93 is slightly smaller than the width of the left slot 831. The bottom of each sliding seat 9 on the other side of the straight rod is a left positioning block 92, the left positioning block 92 is a square block, the number of the left positioning block 92 is two and is distributed at intervals, and the width of the left positioning block 92 is slightly smaller than the width of the right slot 841.

[0052] In combination with Figure 8 , Figure 9 , if the half-wave plate 11 is installed on the sliding seat 9 connected with the left positioning block 92, the half-wave plate 11 needs to be called only by sliding the sliding seat 9 from the support rod to the straight rod, the two left positioning blocks 92 pass through the right slots 841 and abut on one side of the left block 83, so that the half-wave plate 11 and the quarter-wave plate 1 are on the same optical axis. If the half-wave plate 11 is installed on the sliding seat 9 connected with the right positioning block 93, the half-wave plate 11 needs to be called only by sliding the sliding seat 9 from the support rod to the straight rod, the right positioning block 93 passes through the left slot 831 and abuts on one side of the right block 84, so that the half-wave plate 11 and the quarter-wave plate 1 are on the same optical axis. The use of other optical devices is the same. By adopting the mounting bracket 8 with different sliding seats 9, the required optical devices can be quickly called, and since the mounting bracket 8 has been positioned during installation, subsequent multiple uses of different optical devices do not need to be positioned and adjusted in position, which greatly reduces the experimental error. In addition, compared with the more advanced electric debugging table, the use of the mounting bracket 8 and the sliding seat 9 has simple structure, low manufacturing cost and low procurement cost. Although manual operation is needed, it is convenient and fast.

[0053] In combination Figure 6 、 Figure 7 The bottom of the sliding seat 9 is fixed with a block-shaped direction stabilizing seat 91, the bottom of the direction stabilizing seat 91 extends out of the sliding seat 9 and extends into the sliding channel 82, the width of the direction stabilizing seat 91 is the same as the width of the sliding channel 82, the length of the direction stabilizing seat 91 embedded in the sliding channel 82 is less than the depth of the sliding channel 82, the left positioning block 92 and the right positioning block 93 are fixedly connected below the direction stabilizing seat 91; the left positioning block 92, the right positioning block 93 and the direction stabilizing seat 91 are all made of metal material, the sliding channel 82 is embedded with a magnet 85 on the side of the left block 83 and the right block 84, and the left positioning block 92 and the right positioning block 93 abut against the magnet 85 when moving to the left block 83 and the right block 84. The direction stabilizing seat 91 can stabilize the moving direction of the sliding seat 9, avoid the deflection of the sliding seat 9 on the horizontal plane during movement, and make the optical device also deflect to affect the measurement accuracy. The magnet 85 cooperates with the left block 83 and the right block 84 to quickly position and also stably fix the sliding seat 9, so that the sliding seat 9 can resist the vibration of the experiment table 7 and not displace, and ensure the accuracy of the detected data. Compared with the traditional fixing mode of screwing on and off the bolt, although the fixing strength of this mode is not as good as that of the bolt connection pair, it is also enough to be used in the optical measurement environment with low vibration probability, and more importantly, it simplifies the calling process and improves the operation efficiency.

[0054] In summary, the application designs a new laser echo receiving system, which can not only detect laser echo, but also replace the single photon detector with an energy meter through time-sharing public use, so as to measure the wave plate angle when the laser energy appears peak.

[0055] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-precision, high-energy laser polarization state detection system, characterized in that: The system includes a focusing lens, a collimating lens, a Glan laser polarizer, a fiber-coupled lens, and a power meter. The focusing lens focuses the detected light path onto the collimating lens, which then constricts the echo beam. The constricted beam is modulated by the Glan laser polarizer to change the polarization direction of the echo beam. Finally, the modulated beam is incident on the power meter. The angle corresponding to the energy peak is determined by the rotation angle of the quarter-wave plate and half-wave plate after detecting the energy peak. The effective focal length of the receiving light path of the power meter satisfies the following condition: The aperture of the receiving mirror; Focal length; The incident beam divergence angle is half an angle. Between the Glan laser polarizer and the collimating lens, there are also quarter-wave plates and half-wave plates. The Glan laser polarizer, quarter-wave plates, and half-wave plates are arranged on a turntable with a stroke of 360° and are all located on the same vertical plane. An X-shaped mounting bracket is set under the half-wave plate. The middle of the mounting bracket is a straight rod with a slide rail. A left stop block and a right stop block are fixedly connected at intervals in the slide rail. A left through slot is opened in the middle of the left stop block, and two right through slots are opened at intervals in the right stop block. The distance between the two right through slots is greater than or equal to the width of the left through slot. A slide block is fixedly connected to the bottom of the turntable below the half-wave plate. Two left positioning blocks are fixedly connected at intervals under the slide block. The two left positioning blocks pass through the right through slots and abut against one side of the left stop block so that the half-wave plate and the quarter-wave plate are on the same optical axis.

2. The high-precision, high-energy laser polarization state detection system according to claim 1, characterized in that: Optical components are slidably connected to all four sides of the mounting bracket. The optical components are fixed to different slides. A right positioning block is fixed to the bottom of the slide on one side of the straight rod, and a left positioning block is fixed to the bottom of the slide on the other side of the straight rod. The right positioning block passes through the left through slot and abuts against the right stop block to make the optical components and the quarter-wave plate on the same optical axis.

3. The high-precision, high-energy laser polarization state detection system according to claim 2, characterized in that: Each slide block has a fixed locating seat at its bottom. The width of the locating seat is the same as the width of the slide. The length of the locating seat embedded in the slide is less than the depth of the slide. The left and right positioning blocks are fixed under the locating seats.

4. The high-precision, high-energy laser polarization state detection system according to claim 3, characterized in that: The left positioning block, right positioning block, and stabilizer are all made of metal. Magnets are embedded in the slide rails located on one side of the left and right stops. When the left and right positioning blocks move to the left and right stops, they come into contact with the magnets.

5. The high-precision, high-energy laser polarization state detection system according to claim 4, characterized in that: The half-wave plate and other optical components are fixed to the slide by bolts, and the mounting bracket and quarter-wave plate are fixed to the experimental table with multiple bolt holes by bolts.

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