Satellite-borne laser radar multi-functional narrow-band filtering optical system and method

Abstract

A kind of spaceborne laser radar multi-functional narrow-band filtering optical system and method, comprising: 1064nm channel and 532nm channel, with the function of the narrow-band filtering of 1064nm and 532nm dual-wavelength channel laser scattering echo, meet the needs of different wavelength laser common receiving optical system and APD detector, compact structure, high integration;With the function of testing the parallelism and transmittance of the whole machine transceiver of different wavelength channels without disassembling any assembled and adjusted component, the testing method is simple, suitable for whole machine testing;With the ability to cancel any wavelength channel arbitrarily, while keeping the auxiliary testing function of another channel unchanged, strong engineering applicability.

Description

Technical Field

[0001] This invention belongs to the field of spaceborne lidar and relates to a multifunctional narrowband filtering optical system and method for spaceborne lidar, which can be used for echo narrowband filtering of dual-wavelength spaceborne lidar and ground testing of the overall transceiver parallelism and transmittance. Background Technology

[0002] The narrowband filtering optical system of a spaceborne lidar converts the laser scattered echo of a specific wavelength and ground background stray light collected by the laser receiving system into parallel light. The ground background stray light is then filtered out by a narrowband filter, allowing the laser echo of the specific wavelength to pass through and converge to the APD detector. Finally, the APD responds with an output signal.

[0003] However, traditional spaceborne lidar narrowband filtering optical systems have limited functionality, typically only capable of filtering single-wavelength lasers. This makes them unsuitable for lidar layouts that share a dual-wavelength laser receiving optical system and APD detector. Furthermore, because narrowband filtering optical systems lack auxiliary test interfaces, testing the overall transmit / receive parallelism and transmittance after lidar assembly and adjustment involves disassembling and resetting the APD assembly or focal fiber, a complex process requiring high resetting accuracy. This method of test transmit / receive parallelism ignores the positional deviation between the reset APD assembly and focal fiber and the center of the receiving field of view, particularly the parallelism deviation caused by inaccurate resetting of the APD assembly and focal fiber. Another method, measuring transmit / receive parallelism through changes in the APD detector's response amplitude, suffers from significant amplitude fluctuations in the APD detector's response to simulated echoes, resulting in inaccurate measurements.

[0004] In addition, after adopting the traditional narrowband filter optical system of spaceborne lidar, the entire optical system has no auxiliary test interface, which makes it impossible to actually measure the true transmittance of the system. It can only be theoretically calculated through the transmittance or reflectance of each lens in the optical system.

[0005] Traditional narrowband filtering optical systems for lidar are unsuitable for lidar layouts that share a multi-wavelength laser receiving optical system and an APD detector. They suffer from inconvenience and inaccuracy in testing transmit-receive parallelism, and the lack of external testing interfaces prevents the accurate measurement of the system's true transmittance. Currently, there are no relevant documents or methods for developing a dual-wavelength narrowband filtering optical system that can both realize the functionality of a dual-wavelength laser receiving optical system and an APD detector, and also allows for the accurate measurement of the system's transmit-receive parallelism and transmittance through its auxiliary testing interface. Summary of the Invention

[0006] The problem this invention aims to solve is to provide a multifunctional narrowband filtering optical system and method for spaceborne lidar, realizing narrowband filtering of dual wavelength channels at 1064nm and 532nm, meeting the needs of sharing a receiving optical system and APD detector for lasers of different wavelengths. It features a compact structure and high integration; it allows for testing of the overall transceiver parallelism and transmittance of different wavelength channels using an auxiliary test interface without disassembling any assembled components. The testing method is simple and suitable for overall system testing, avoiding test errors caused by disassembly and resetting of APD components or focal fiber in existing transceiver parallelism testing methods, as well as test errors caused by fluctuations in APD response amplitude; it also has the ability to cancel one wavelength channel while maintaining the auxiliary testing function of the other channel, making it highly applicable in engineering projects.

[0007] The technical solution adopted in this invention is:

[0008] A multi-functional narrowband filtering optical system for spaceborne lidar includes: a 1064nm channel, a 532nm channel, and a dual-wavelength shared channel;

[0009] The dual-wavelength shared channel includes: a third lens group, window glass, photodetector APD, and dichroic prism;

[0010] The 1064nm channel, from right to left along the optical path, includes: a first lens group, a 1064nm narrowband filter, a 1064nm beam splitter, a second lens group, and a first auxiliary test interface; the first auxiliary test interface is used to test the transceiver parallelism and overall transmittance of the laser receiving optical system at a wavelength of 1064nm.

[0011] After being reflected by the 1064nm beam splitter, the light path consists of, from top to bottom, a light absorber, a dichroic prism, a third lens group, a window glass, and a photodetector (APD).

[0012] The 532nm channel, from bottom to top along the optical path, includes: the fourth lens group, the 532nm narrowband filter, the 532nm beam splitter, the fifth lens group, and the second auxiliary test interface; the second auxiliary test interface is used for the transmit-receive parallelism and overall transmittance of the laser receiving optical system in the 532nm band.

[0013] After being reflected by the 532nm beam splitter, the light path consists of, in sequence: a light absorber, a dichroic prism, a third lens group, a window glass, and a photodetector (APD).

[0014] The 1064nm and 532nm channels share four components: a third lens group, a window glass, a photodetector (APD), and a dichroic prism.

[0015] Preferably, the first auxiliary test interface is located at the focal point of the second lens group, the photodetector APD is located at the focal point of the third lens group, the focal point of the third lens group is conjugate with the focal point of the first lens group, and is also conjugate with the focal point of the second lens group.

[0016] Preferably, the second auxiliary test interface is located at the focal point of the fifth lens group, and the focal point of the fifth lens group is conjugate with the focal point of the fourth lens group and simultaneously conjugate with the focal point of the third lens group.

[0017] Preferably, the layout of the multifunctional narrowband filtering optical system can be changed to place the 1064nm narrowband filter between the 1064nm beam splitter and the dichroic prism.

[0018] Preferably, a 532nm narrowband filter is placed between the 532nm beam splitter and the dichroic prism. This narrowband filtering optical system can perform narrowband filtering on the heat dissipation echo of lasers with dual wavelengths of 1064nm and 532nm, meeting the requirements of sharing a receiving optical system and APD detector for lasers of different wavelengths; the auxiliary test interface can be used to test the overall transceiver parallelism and overall transmittance of different wavelength channels; and it has the ability to use a single wavelength channel without changing the auxiliary test function.

[0019] Secondly,

[0020] A method for testing the transmit / receive parallelism of a 1064nm channel using the multifunctional narrowband filter optical system as described in the first aspect includes:

[0021] (1) The laser emission system emits a 1064nm pulsed laser, which is attenuated by the attenuator device and then enters the collimator. The collimator converges the emitted light spot onto the collimator focal plane detector CCD. The emitted light spot image is acquired on the laser beam analyzer, and the centroid coordinates X1 and Y1 of the light spot are calculated.

[0022] (2) Place a simulated light source at the first auxiliary test interface, turn on the light source to emit a 1064nm laser beam, the laser beam is converted into parallel light by the second lens group and incident on the 45° inclined surface of the 1064nm beam splitter. If the reflectivity of the 1064nm laser on the 45° inclined surface of the 1064nm beam splitter is 99%, then the 1064nm beam splitter will reflect 99% of the incident parallel light to the light absorber and be absorbed. 1% of the incident parallel light passes through the 1064nm narrowband filter and is transmitted to the first lens group. The first lens group will focus the parallel beam to its focal point and enter the left interface of the focal plane fiber.

[0023] (3) The beam is guided through the focal plane fiber to the focal plane of the laser receiving optical system, and then exits through the laser receiving optical system to the collimator. The collimator focuses the beam onto the collimator's focal plane CCD, and the laser beam analyzer acquires the spot image of the simulated light source and calculates the centroid coordinates X2 and Y2 of the spot.

[0024] (4) The deviation of the transmit / receive parallelism of the 1064nm channel in the X direction is:

[0025]

[0026] The deviation of the 1064nm channel transmit / receive parallelism in the Y direction is:

[0027]

[0028] Where f is the focal length of the collimator, and p is the pixel size of the collimator's focal plane CCD.

[0029] A method for testing the transmit / receive parallelism of a 532nm channel using the multifunctional narrowband filter optical system described in the first aspect includes:

[0030] (1) The laser emission system emits a 532nm pulsed laser, which is attenuated by the attenuator device and then enters the collimator. The collimator converges the emitted light spot onto the focal plane CCD of the collimator. The emitted light spot image is obtained on the laser beam analyzer, and the centroid coordinates X3 and Y3 of the light spot are calculated.

[0031] (2) Place a simulated light source at the second auxiliary test interface, turn on the light source to emit a 532nm laser beam, the laser beam is converted into parallel light by the fifth lens group and incident on the 45° inclined surface of the 532nm beam splitter. If the reflectivity of the 532nm laser on the 45° inclined surface of the 532nm beam splitter is 99%, then the 532nm beam splitter will reflect 99% of the incident parallel light to the light absorber and be absorbed, and transmit 1% of the incident parallel light through the 532nm narrowband filter to the fourth lens group. The fourth lens group will focus the parallel beam to its focal point and enter the left interface of the focal plane fiber. At this time, the left interface of the focal plane fiber should be removed from the focal point of the first lens group and installed at the focal point of the fourth lens group.

[0032] (3) The beam is guided to the focal plane of the laser receiving optical system through the focal plane fiber, and then emitted to the collimator after passing through the laser receiving optical system. The collimator with a focal length of 12m focuses the beam onto the collimator focal plane CCD. The pixel size of the collimator focal plane CCD is 9um. The gain and exposure time are adjusted on the laser beam analyzer to obtain the spot image of the simulated light source, and the centroid coordinates X4 and Y4 of the simulated light source spot are automatically calculated by the beam analysis software.

[0033] (4) The deviation of the transmit / receive parallelism of the 532nm channel in the X direction is:

[0034]

[0035] The deviation of the transmit / receive parallelism in the Y direction is:

[0036]

[0037] Where f is the focal length of the collimator, and p is the pixel size of the collimator's focal plane CCD.

[0038] A method for measuring the transmittance of a 1064nm channel using a multifunctional narrowband filter optical system as described in the first aspect includes:

[0039] (1) Place a simulated light source at the CCD position of the collimator focal plane. The simulated light source emits a 1064nm laser beam. After measuring the emitted laser power at the output port of the simulated light source using an optical power meter, the optical power meter is removed.

[0040] (2) The 1064nm laser beam is converted into parallel light by a collimator and enters the laser receiving optical system and converges on the focal plane of the laser receiving optical system before entering the focal plane optical fiber.

[0041] (3) The 1064nm laser beam is transmitted through the focal plane fiber and enters the focal point of the first lens group of the narrowband filter optical system. After being filtered by the 1064nm narrowband filter, the non-1064nm stray light enters the 1064nm beam splitter. If the reflectivity of the 1064nm laser on the 45° inclined plane of the 1064nm beam splitter is 99%, then 99% of the energy is reflected by the 1064nm beam splitter to the dichroic prism. Most of the 1064nm laser is then transmitted to the third lens group. The third lens group converges the parallel light and enters the photodetector APD through the window glass.

[0042] The remaining 1% of the energy is transmitted to the second lens group, which refocuses the parallel light back to the first auxiliary test interface. An optical power meter is installed at the first auxiliary test interface to measure the optical power at this time, which is I2.

[0043] (4) Based on the transmittance τ2 of the second lens group, the transmittance τ3 of the third lens group, the transmittance τ4 of the window glass, and the 1064nm transmittance τ5 of the dichroic prism, the overall transmittance of the 1064nm channel from the laser receiving optical system to the focal fiber (5) and the narrowband filtering optical system can be calculated as follows:

[0044]

[0045] A method for measuring the transmittance of a 532nm channel using a multifunctional narrowband filter optical system as described in the first aspect includes:

[0046] (1) Place a simulated light source at the CCD position of the collimator focal plane. The simulated light source emits a 532nm laser beam. After measuring the emitted laser power at the output port of the simulated light source using an optical power meter, the optical power meter is removed.

[0047] (2) The 532nm laser beam is converted into parallel light by a collimator and enters the laser receiving optical system and converges on the focal plane of the laser receiving optical system. It then enters the focal plane fiber. At this time, the left interface of the focal plane fiber should be removed from the focal point of the first lens group and installed at the focal point of the fourth lens group.

[0048] (3) The laser beam is transmitted through the focal plane fiber and enters the focal point of the fourth lens group of the narrowband filter optical system. After being filtered by the 532nm narrowband filter to remove stray light of non-532nm wavelength, it enters the 532nm beam splitter. If the reflectivity of the 532nm laser on the 45° inclined plane of the 532nm beam splitter is 99%, then 99% of the energy is reflected by the 532nm beam splitter to the dichroic prism. Most of the laser light is reflected to the third lens group, which focuses the parallel light and enters the photodetector APD through the window glass. The remaining 1% of the energy is transmitted to the fifth lens group, which focuses the parallel light back to the second auxiliary test interface. An optical power meter is installed at the second auxiliary test interface to measure the optical power at this time as I4.

[0049] (4) Based on the transmittance τ5 of the fifth lens group, the 532nm reflectance τ6 of the dichroic prism, the transmittance τ3 of the third lens group, and the transmittance τ4 of the window glass, the overall transmittance of the 532nm channel from the laser receiving optical system to the focal plane fiber and narrowband filtering optical system can be calculated as follows:

[0050]

[0051] The advantages of this invention compared to the prior art are:

[0052] (1) This invention has a narrowband filtering function for laser scattering echoes of dual wavelengths of 1064nm and 532nm, which meets the needs of sharing the receiving optical system and APD detector for lasers of different wavelengths. It avoids the need to design and install narrowband filtering optical systems separately for different wavelength channels. It has a compact structure and high integration.

[0053] (2) This invention can test the transceiver parallelism of different wavelength channels by using an external simulated light source through an auxiliary test interface without disassembling any assembled components. The test method is simple and suitable for transceiver parallelism testing after the entire machine has been assembled.

[0054] (3) This invention can achieve the overall transmittance test of different wavelength channels by using an external optical power meter through an auxiliary test interface without disassembling any assembled components. It can obtain the system-level measured transmittance after the attenuation of various optical components, including the structural blockage attenuation of the laser receiving system, the focal fiber attenuation, and the narrowband filter attenuation. The test method is simple and effective.

[0055] (4) The present invention can arbitrarily cancel a certain wavelength channel, simplify the narrowband filter optical system, and still maintain the auxiliary testing function of the other channel, which has strong engineering applicability. Attached Figure Description

[0056] Figure 1 This is a layout diagram of the multifunctional narrowband filtering optical system of the present invention;

[0057] Figure 2 This is a schematic diagram of the overall transceiver parallelism test principle in the method of the present invention;

[0058] Figure 3 This is a schematic diagram of the overall transmittance test principle in the method of the present invention;

[0059] Figure 4 This is a schematic diagram showing the relative coordinate relationship between the centroid of the emitted light spot on the CCD focal plane and the centroid of the simulated light source spot when testing the parallelism of the whole machine's transmit and receive during the method of the present invention. Detailed Implementation

[0060] This invention proposes a multifunctional narrowband filtering optical system for spaceborne lidar. It utilizes a dichroic prism 410 to achieve narrowband filtering for dual wavelength channels of 1064nm and 532nm, solving the need for sharing a receiving optical system and APD detector for lasers of different wavelengths. The system is compact and highly integrated. By using a 1064nm beam splitter prism 403, a 532nm beam splitter prism 413, and first and second auxiliary test interfaces 408 and 415, it enables testing of the overall transceiver parallelism and transmittance of different wavelength channels without disassembling any assembled components. This solves the problem of difficult transceiver parallelism and transmittance testing at the overall system stage. The testing method is simple and has strong engineering applicability.

[0061] Specifically, such as Figure 1 As shown, the present invention proposes a multifunctional narrowband filtering optical system for spaceborne lidar, including a 1064nm channel and a 532nm channel:

[0062] The 1064nm channel, from right to left along the optical path, includes a first lens group 401, a 1064nm narrowband filter 402, a 1064nm beam splitter 403, a second lens group 404, and a first auxiliary test interface 408; and from top to bottom along the optical path, it includes a light absorber 407, a dichroic prism 410, a third lens group 405, a window glass 406, and a photodetector APD 409.

[0063] The 532nm channel, from bottom to top along the optical path, includes a fourth lens group 411, a 532nm narrowband filter 412, a 532nm beam splitter 413, a fifth lens group 414, and a second auxiliary test interface 415. After reflection by the 532nm beam splitter 413, along the optical path, it includes a light absorber 407, a dichroic prism 410, a third lens group 405, a window glass 406, and a photodetector APD 409.

[0064] The two channels share four components: the third lens group 405, the window glass 406, the photodetector APD 409, and the dichroic prism 410.

[0065] The 45° bevel surfaces of the 1064nm beam splitter 403 and the 532nm beam splitter 413 are coated with high-reflectivity films for their respective wavelengths to ensure that the reflectivity at their respective wavelengths is not less than 95%. The 45° bevel surface of the dichroic prism 410 is coated with a high-transmittance film for the 1064nm wavelength to ensure that the transmittance at the 1064nm wavelength is not less than 95%, and the 45° bevel surface is coated with a high-reflectivity film for the 532nm wavelength to ensure that the reflectivity at the 532nm wavelength is not less than 95%.

[0066] The first auxiliary test interface 408 is located at the focal point of the second lens group 404, and the photodetector APD 409 is located at the focal point of the third lens group 405. The setup ensures that this focal point is simultaneously conjugate with the focal points of the first lens group 401 and the second lens group 404, guaranteeing that the light emitted from the first auxiliary test interface 408 represents the light emitted from the photodetector APD 409; the two are equivalent. Simultaneously, the second auxiliary test interface 415 is located at the focal point of the fifth lens group 414. The setup ensures that this focal point is simultaneously conjugate with the focal points of the fourth lens group 411 and the third lens group 405, guaranteeing that the light emitted from the second auxiliary test interface 415 represents the light emitted from the photodetector APD 409; the two are also equivalent.

[0067] Furthermore, this technical solution also allows for the placement of the 1064nm narrowband filter 402 between the 1064nm beam splitter prism 403 and the dichroic prism 410, and the placement of the 532nm narrowband filter 412 between the 532nm beam splitter prism 413 and the dichroic prism 410. The advantage of this placement is that when testing transmit / receive parallelism using the first auxiliary test interface 408, the beam avoids the 1064nm narrowband filter 402; similarly, when testing transmit / receive parallelism using the second auxiliary test interface 415, the beam avoids the 532nm narrowband filter 412. This allows for the selection of any wavelength of analog light source to test the transmit / receive parallelism of the system, reducing the requirements for the analog light source. However, when testing the system transmittance, the transmittance of the 1064nm narrowband filter 402 and the 532nm narrowband filter 412 is not included in the test system; their transmittance must be tested separately before calculating the overall transmittance. The specific layout of the 1064nm narrowband filter 402 and the 532nm narrowband filter 412 should be selected appropriately according to the system requirements.

[0068] The main functions of a multi-functional narrowband filtering optical system for spaceborne lidar are as follows:

[0069] (1) To achieve narrowband filtering of laser scattering echoes from dual wavelength channels of 1064nm and 532nm, so as to meet the requirements of sharing the receiving optical system and APD detector for lasers of different wavelengths.

[0070] (2) By connecting an external analog light source through the first auxiliary test interface 408 and the second auxiliary test interface 416, the parallelism of the whole machine's transceiver for different wavelength channels can be tested without disassembling any assembled components.

[0071] (3) By connecting an external optical power meter through the first auxiliary test interface 408 and the second auxiliary test interface 416, the overall transmittance of different wavelength channels can be tested without disassembling any assembled components.

[0072] (4) It has the ability to cancel one wavelength channel at will, that is, to simplify the narrowband filter optical system, while keeping the auxiliary testing function of the other channel unchanged.

[0073] like Figure 2 As shown, this invention proposes a method for testing the transmit-receive parallelism of a multifunctional narrowband filter optical system for spaceborne lidar, the steps of which are as follows:

[0074] For the 1064nm channel

[0075] (1) The laser emitting system 1 emits a 1064nm pulsed laser with an energy of 75mJ and a frequency of 40Hz. After being attenuated by 10dB by the attenuator device 6, it enters the collimator 7 with a focal length of 12m. The emitted light spot is focused by the collimator and falls on the focal plane CCD 8 of the collimator. The pixel size of the focal plane CCD 8 is 9um. The laser beam analyzer 9 adjusts the appropriate gain and exposure time to obtain the image of the emitted light spot. The laser spot centroid coordinates X1 and Y1 are automatically calculated by the beam analysis software. Figure 4 As shown;

[0076] (2) A simulated light source 10 is placed at the first auxiliary test interface 408. The light source emits a 1064nm laser beam with an energy of 5uW and a frequency of 10kHz. The laser beam is converted into parallel light by the second lens group 404 and incident on the 45° inclined surface of the beam splitter 403. If the reflective film coated on the 45° inclined surface of the 1064nm beam splitter 403 has a reflectivity of 99% for the 1064nm laser, then the beam splitter 403 will reflect 99% of the incident parallel light to the light absorber 407 and absorb it. The remaining 1% of the incident parallel light passes through the 1064nm narrowband filter 402 and is transmitted to the first lens group 401. The first lens group 401 focuses the parallel beam to its focal point and enters the left interface of the focal plane fiber 5.

[0077] (3) The light beam is guided through the focal plane fiber 5 to the focal plane 3 of the laser receiving optical system, and then exits through the laser receiving optical system 2 to the collimator 7. The collimator 7, with a focal length of 12m, focuses the light beam onto the collimator focal plane CCD 8. The pixel size of the collimator focal plane CCD 8 is 9um. The gain and exposure time are adjusted on the laser beam analyzer 9 to acquire the spot image of the simulated light source 10, and the centroid coordinates X2 and Y2 of the simulated light source 10 are automatically calculated by the beam analysis software. Figure 4 As shown;

[0078] (4) Based on the centroid coordinates obtained above, the following can be obtained:

[0079] The X-axis deviation of the transmit / receive parallelism of the 1064nm channel is:

[0080]

[0081] The deviation of the 1064nm channel transmit / receive parallelism in the Y direction is:

[0082]

[0083] Where f is the focal length of the collimator, 12m; p is the pixel size of the collimator's focal plane CCD, 9um;

[0084] For the 532nm channel

[0085] (1) The laser emitting system 1 emits a 532nm pulsed laser with an energy of 75mJ and a frequency of 40Hz. After being attenuated by 10dB by the attenuator device 6, it enters the collimator 7 with a focal length of 12m. The emitted light spot is focused by the collimator and falls on the focal plane CCD 8 of the collimator. The pixel size of the focal plane CCD 8 is 9um. The laser beam analyzer 9 adjusts the appropriate gain and exposure time to obtain the image of the emitted light spot. The centroid coordinates X3 and Y3 of the light spot are automatically calculated by the beam analysis software. Figure 4 As shown;

[0086] (2) Place a simulated light source 10 at the second auxiliary test interface 415 and turn on the light source to emit a 532nm laser beam with an energy of 5uW and a frequency of 10kHz. The laser beam is converted into parallel light by the fifth lens group 414 and incident on the 45° inclined surface of the 532nm beam splitter 413. If the reflectivity of the 532nm laser on the 45° inclined surface of the 532nm beam splitter 40 is 99%, then the 532nm beam splitter 413 will reflect 99% of the incident parallel light to the light absorber 407 and absorb it. 1% of the incident parallel light will pass through the 532nm narrowband filter 412 and be transmitted to the fourth lens group 411. The fourth lens group 411 will focus the parallel beam to its focal point and enter the left interface of the focal plane fiber 5. At this time, the left interface of the focal plane fiber 5 should be removed from the focal point of the first lens group 401 and installed at the focal point of the fourth lens group 411.

[0087] (3) The light beam is guided through the focal plane fiber 5 to the focal plane 3 of the laser receiving optical system, and then exits through the laser receiving optical system 2 to the collimator 7. The collimator 7, with a focal length of 12m, focuses the light beam onto the collimator focal plane CCD 8. The pixel size of the collimator focal plane CCD 8 is 9um. The gain and exposure time are adjusted on the laser beam analyzer 9 to obtain the spot image of the simulated light source 10. The centroid coordinates X4 and Y4 of the simulated light source 10 in the 532nm channel are automatically calculated by the beam analysis software. Figure 4 As shown;

[0088] (4) Based on the centroid coordinates obtained above, the following can be obtained:

[0089] The deviation of the transmit / receive parallelism of the 532nm channel in the X-axis is:

[0090]

[0091] The deviation of the transmit / receive parallelism in the Y direction is:

[0092]

[0093] Where f is the focal length of the collimator, 12m; p is the pixel size of the collimator's focal plane CCD, 9um;

[0094] Furthermore, such as Figure 3 As shown, this invention proposes a method for testing the overall transmittance of a multifunctional narrowband filtering optical system for spaceborne lidar, the steps of which are as follows:

[0095] For the 1064nm channel

[0096] (1) Place a simulated light source 10 at the focal point of the collimator CCD position 8 or the focal point of its conjugate optical path. The simulated light source 10 emits a 1064nm laser beam with an energy of 5mW and a frequency of 10kHz. After measuring the actual power of the emitted laser at the output port of the simulated light source 10 using an optical power meter 9, remove the optical power meter 9.

[0097] (2) The 1064nm laser beam is converted into parallel light through the 12m collimator 7 and enters the laser receiving optical system 2 and converges on the focal plane 3 of the laser receiving optical system, and then enters the focal plane optical fiber 5.

[0098] (3) The laser beam is transmitted through the focal plane fiber 5 and enters the focal point of the first lens group 401 of the narrowband filter optical system 4. After being filtered by the 1064nm narrowband filter 402 to remove stray light other than 1064nm, it enters the 1064nm beam splitter 403. If the reflectivity of the 1064nm laser on the 45° inclined plane of the 1064nm beam splitter 403 is 99%, then 99% of the energy is reflected by the 1064nm beam splitter 403 to the dichroic prism 410. Most of the 1064nm laser is then transmitted to the third lens group 405. The third lens group 405 focuses the parallel light and enters the photodetector APD 409 through the window glass 406.

[0099] The remaining 1% of the energy is transmitted to the second lens group 404, which refocuses the parallel light onto the first auxiliary test interface 408. An optical power meter 9 is installed at the first auxiliary test interface 408 to measure the actual optical power at this time, which is I2.

[0100] (4) Based on the transmittance τ2 of the second lens group 404, the transmittance τ3 of the third lens group 405, and the transmittance τ4 of the window glass 406 obtained during the component stage testing, and the 1064nm transmittance τ5 of the dichroic prism 410, the overall transmittance of the 1064nm channel from the laser receiving optical system 2 to the focal fiber 5 and the narrowband filtering optical system 4 can be calculated as follows:

[0101]

[0102] For the 532nm channel

[0103] (1) Place a simulated light source 10 at the focal point of the collimator CCD position 8 or the focal point of its conjugate optical path. The simulated light source 10 emits a 532nm laser beam with an energy of 5mW and a frequency of 10kHz. After measuring the actual power of the emitted laser at the output port of the simulated light source 10 using an optical power meter 9, remove the optical power meter 9.

[0104] (2) The 532nm laser beam is converted into parallel light through the 12m collimator 7 and enters the laser receiving optical system 2 and converges on the focal plane 3 of the laser receiving optical system, and enters the focal plane fiber 5. At this time, the left interface of the focal plane fiber 5 should be removed from the focal point of the first lens group 401 and installed at the focal point of the fourth lens group 411.

[0105] (3) The laser beam is transmitted through the focal plane fiber 5 and enters the focal point of the fourth lens group 411 of the narrowband filter optical system 4. After the stray light of non-532nm wavelength is filtered by the 532nm narrowband filter 412, it enters the 532nm beam splitter 413. If the reflectivity of the 532nm laser on the 45° inclined plane of the 532nm beam splitter 413 is 99%, then 99% of the energy is reflected by the 532nm beam splitter 413 to the dichroic prism 410. Most of the laser is reflected to the third lens group 405. The third lens group 405 focuses the parallel light and enters the photodetector APD 409 through the window glass 406.

[0106] The remaining 1% of the energy is transmitted to the fifth lens group 414, which refocuses the parallel light to the second auxiliary test interface 415. An optical power meter 9 is installed at the second auxiliary test interface 415 to measure the actual optical power at this time, which is I4.

[0107] (4) Based on the transmittance τ5 of the fifth lens group 414, the 532nm reflectance τ6 of the dichroic prism 410, the transmittance τ3 of the third lens group 405, and the transmittance τ4 of the window glass 406 obtained during the component stage testing, the overall transmittance of the 532nm channel from the laser receiving optical system 2 to the focal fiber 5 and the narrowband filtering optical system 4 can be calculated as follows:

[0108]

[0109] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make possible variations and modifications to the technical solutions of the present invention using the disclosed methods and techniques without departing from the spirit and scope of the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall fall within the protection scope of the present invention. Where there is no conflict, the embodiments of this application and the technical features thereof can be combined with each other.

[0110] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A multi-functional narrowband filtering optical system for spaceborne lidar, characterized in that, include: 1064nm channel, 532nm channel, and dual-wavelength shared channel; The dual-wavelength shared channel includes: a third lens group (405), a window glass (406), a photodetector APD (409), and a dichroic prism (410). The 1064nm channel, from right to left along the optical path, includes: a first lens group (401), a 1064nm narrowband filter (402), a 1064nm beam splitter (403), a second lens group (404), and a first auxiliary test interface (408); the first auxiliary test interface (408) is used to test the transmit-receive parallelism and overall transmittance of the laser receiving optical system (2) at a wavelength of 1064nm. After being reflected by the 1064nm beam splitter (403), the light path includes, from top to bottom, a dichroic prism (410), a third lens group (405), a window glass (406), and a photodetector APD (409). The 532nm channel, from bottom to top along the optical path, includes: a fourth lens group (411), a 532nm narrowband filter (412), a 532nm beam splitter (413), a fifth lens group (414), and a second auxiliary test interface (415); the second auxiliary test interface (415) is used to test the transmit-receive parallelism and overall transmittance of the laser receiving optical system (2) in the 532nm band. After being reflected by the 532nm beam splitter (413), the light path includes, in sequence: a light absorber (407), a dichroic prism (410), a third lens group (405), a window glass (406), and a photodetector APD (409).

2. The multifunctional narrowband filtering optical system according to claim 1, characterized in that: The first auxiliary test interface (408) is located at the focal point of the second lens group (404), and the photodetector APD (409) is located at the focal point of the third lens group (405). The focal point of the third lens group (405) is conjugate with the focal point of the first lens group (401) and is also conjugate with the focal point of the second lens group (404).

3. The multifunctional narrowband filtering optical system according to claim 1, characterized in that: The second auxiliary test interface (415) is located at the focal point of the fifth lens group (414). The focal point of the fifth lens group (414) is conjugate with the focal point of the fourth lens group (411) and is also conjugate with the focal point of the third lens group (405).

4. The multifunctional narrowband filtering optical system according to claim 1, characterized in that: A 1064nm narrowband filter (402) is placed between a 1064nm beam splitter (403) and a dichroic prism (410).

5. The multifunctional narrowband filtering optical system according to claim 1, characterized in that: A 532nm narrowband filter (412) is placed between a 532nm beam splitter (413) and a dichroic prism (410).

6. A method for testing the transmit / receive parallelism of a 1064nm channel using the multifunctional narrowband filtering optical system as described in any one of claims 1 to 5, characterized in that, include: The laser emitting system (1) emits a 1064nm pulsed laser, which is attenuated by the attenuator device (6) and then enters the collimator (7). The emitted light spot is focused by the collimator and falls on the focal plane CCD (8) of the collimator. The image of the emitted light spot is acquired on the laser beam analyzer (9), and the centroid coordinates of the light spot are calculated. , ; A simulated light source (10) is placed at the first auxiliary test interface (408). The light source is turned on and emits a 1064nm laser beam. The laser beam is converted into parallel light by the second lens group (404) and incident on the 45° inclined surface of the 1064nm beam splitter (403). The beam splitter (403) reflects most of the incident parallel light to the light absorber (407) and absorbs it. A small part of the incident parallel light passes through the 1064nm narrowband filter (402) and is transmitted to the first lens group (401). The first lens group (401) focuses the parallel beam to its focal point and enters the left interface of the focal plane fiber (5). The light beam is guided through the focal plane fiber (5) to the focal plane (3) of the laser receiving optical system, and then exits through the laser receiving optical system (2) to the collimator (7). The collimator (7) focuses the light beam onto the collimator focal plane CCD (8), and the spot image of the simulated light source (10) is acquired on the laser beam analyzer (9), and the centroid coordinates of the spot are calculated. , ; The X-axis deviation of the transmit / receive parallelism of the 1064nm channel is: ； The deviation of the 1064nm channel transmit / receive parallelism in the Y direction is: ； in, p is the focal length of the collimator (7), and p is the pixel size of the collimator focal plane CCD (8).

7. A method for testing the transmit / receive parallelism of a 532nm channel using the multifunctional narrowband filtering optical system as described in any one of claims 1 to 5, characterized in that, include: The laser emitting system (1) emits a 532nm pulsed laser, which is attenuated by the attenuator device (6) and then enters the collimator (7). The emitted light spot is focused by the collimator and falls on the focal plane CCD (8) of the collimator. The image of the emitted light spot is acquired on the laser beam analyzer (9), and the centroid coordinates of the light spot are calculated. , ; A simulated light source (10) is placed at the second auxiliary test interface (415). The light source is turned on and emits a 532nm laser beam. The laser beam is converted into parallel light by the fifth lens group (414) and incident on the 45° inclined surface of the 532nm beam splitter (413). The 532nm beam splitter (413) reflects most of the incident parallel light to the light absorber (407) and absorbs it. A small portion of the incident parallel light passes through the 532nm narrowband filter (412) and is transmitted to the fourth lens group (411). The fourth lens group (411) focuses the parallel beam to its focal point and enters the left interface of the focal plane fiber (5). At this time, the left interface of the focal plane fiber (5) should be removed from the focal point of the first lens group (401) and installed at the focal point of the fourth lens group (411). The light beam is guided through the focal plane fiber (5) to the focal plane (3) of the laser receiving optical system, and then exits through the laser receiving optical system (2) to the collimator (7). The collimator (7) with a focal length of 12m focuses the light beam onto the collimator focal plane CCD (8). The pixel size of the collimator focal plane CCD (8) is 9um. The gain and exposure time are adjusted on the laser beam analyzer (9) to obtain the spot image of the simulated light source (10), and the centroid coordinates of the spot of the simulated light source (10) are automatically calculated by the beam analysis software. , ; The deviation of the transmit / receive parallelism of the 532nm channel in the X-axis is: ； The deviation of the transmit / receive parallelism in the Y direction is: ； in, ρ is the focal length of the collimator, and p is the pixel size of the collimator's focal plane CCD.

8. A method for testing the transmittance of a 1064nm channel using the multifunctional narrowband filtering optical system as described in any one of claims 1 to 5, characterized in that, include: A simulated light source (10) is placed at the CCD position (8) of the collimator focal plane. The simulated light source (10) emits a 1064nm laser beam. The emitted laser power is measured at the output port of the simulated light source (10) using an optical power meter (9). Remove the optical power meter (9); The 1064nm laser beam is converted into parallel light through a collimator (7) and enters the laser receiving optical system (2) and converges on the focal plane (3) of the laser receiving optical system before entering the focal plane optical fiber (5). A 1064nm laser beam is transmitted through a focal fiber (5) to the focal point of the first lens group (401) of the narrowband filter optical system (4). After being filtered by a 1064nm narrowband filter (402) to remove stray light other than 1064nm, it enters the 1064nm beam splitter (403). Most of the energy is reflected by the 1064nm beam splitter (403) to the dichroic prism (410), and most of the 1064nm laser light is transmitted to the third lens group (405). The third lens group (405) focuses the parallel light and passes through the window glass (406) into the photodetector APD (409). The remaining small portion of the energy is transmitted to the second lens group (404), which refocuses the parallel light to the first auxiliary test interface (408). An optical power meter (9) is installed at the first auxiliary test interface (408) to measure the optical power at this time. ; The reflectivity of the 1064nm beam splitter (403) is 99%; Based on the transmittance of the second lens group (404) Transmittance of the third lens group (405) and the transmittance of window glass (406) The transmittance of the dichroic prism (410) at 1064 nm Then the overall transmittance of the 1064nm channel from the laser receiving optical system (2) to the focal plane fiber (5) and the narrowband filtering optical system (4) can be calculated as follows: 。 9. A method for testing the transmittance of a 532nm channel using the multifunctional narrowband filtering optical system as described in any one of claims 1 to 5, characterized in that, include: A simulated light source (10) is placed at the CCD position (8) of the collimator focal plane. The simulated light source (10) emits a 532nm laser beam. The emitted laser power is measured at the output port of the simulated light source (10) using an optical power meter (9). Remove the optical power meter (9); The 532nm laser beam is converted into parallel light through the collimator (7) and enters the laser receiving optical system (2) and converges on the focal plane (3) of the laser receiving optical system, and enters the focal plane fiber (5). At this time, the left interface of the focal plane fiber (5) should be removed from the focal point of the first lens group (401) and installed at the focal point of the fourth lens group (411). The laser beam is transmitted through the focal plane fiber (5) to the focal point of the fourth lens group (411) of the narrowband filter optical system (4). After being filtered by the 532nm narrowband filter (412) to remove stray light of non-532nm wavelength, it enters the 532nm beam splitter (413). Most of the energy is reflected by the 532nm beam splitter (413) to the dichroic prism (410), and most of the laser light is reflected back to the third lens group (405). The third lens group (405) focuses the parallel light and passes through the window glass (406) into the photodetector APD (409). The remaining small portion of the energy is transmitted to the fifth lens group (414), which refocuses the parallel light to the second auxiliary test interface (415). An optical power meter (9) is installed at the second auxiliary test interface (415) to measure the optical power at this time. ; The reflectivity of the 532nm narrowband filter (412) is 99%; Based on the transmittance of the fifth lens group (414) The 532nm reflectance of the dichroic prism (410) Transmittance of the third lens group (405) and the transmittance of window glass (406) Then the overall transmittance of the 532nm channel from the laser receiving optical system (2) to the focal plane fiber (5) and the narrowband filtering optical system (4) can be calculated as follows: 。

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