Water body laser radar based on coded pulse and coded pulse laser generation method

Abstract

The present invention provides a water body laser radar based on coded pulses and a coded pulse laser generation method. A coded pulse laser conversion device in a modulation mode or a physical mode converts a continuous laser or a pulse laser into a blue-green band coded pulse laser suitable for water body and target detection. When the modulation mode is adopted, the average emission power of the emitted laser is increased, and the coding-related gain is generated by encoding the laser pulses, the background noise is removed, and the system signal-to-noise ratio is improved, thereby realizing long-distance and weak-signal target detection of the pulse laser radar. At the same time, since the continuous laser device is mature, there are more selectable bands, the applicability is wider, and the detection requirements of different water body scenes can be met. When the physical mode is adopted, the laser pulses are encoded to generate two-way coded pulse lasers. Compared with a single-repetition pulse laser radar system, not only the system signal-to-noise ratio can be improved, but also the detection dimension and range can be increased, the detection waiting time can be reduced, and the detection efficiency can be improved.

Description

Technical Field

[0001] The present invention relates to the field of laser radar technology, and in particular to a water body laser radar based on coded pulses and a coded pulse laser generation method. Background Art

[0002] Compared with visible light in other bands, blue-green band lasers have the smallest absorption coefficient in water bodies and are the window for water body lidar detection. LiDAR uses continuous lasers or pulsed lasers for detection. Continuous laser devices are mature and can obtain high average power lasers, and there are many wavelengths to choose from. However, it is difficult to achieve distance resolution in the visible light band through technologies such as continuous wave frequency modulation, and the technology is complex. Pulse lidar can obtain distance information, but the existing single-repetitive pulse blue-green band lidar has a low pulse repetition frequency and low average power, and cannot achieve long-distance detection in water bodies.

[0003] To achieve long-distance detection of lidar in water, the laser must have high average power and pulsed light, but existing technologies cannot meet both requirements in the blue and green bands. Summary of the invention

[0004] The present invention aims to overcome the deficiencies of the prior art and provide a water body laser radar based on coded pulses and a coded pulse laser generation method. The laser source uses a high-power continuous laser or a high-repetition-frequency pulse laser, and a modulated coded pulse conversion method is used to convert the continuous laser into a coded pulse laser, which can not only improve the average emission power of the blue-green band pulse laser, but also generate coding-related gain by encoding the pulse laser, remove background noise, and improve the system signal-to-noise ratio, thereby realizing long-distance and weak signal target detection of the water body pulse laser radar. At the same time, due to the maturity of the continuous laser device, there are more bands to choose from, and the applicability is wider, which can meet the detection needs of different water scenes. In addition, when using a physical coded pulse conversion method, the laser source can use a high-power continuous laser or a high-repetition-frequency pulse laser, and the laser pulse is encoded by a physical coded pulse laser conversion device to generate two-way coded pulse lasers. Compared with a single-repetition pulse laser radar system, it can not only improve the system signal-to-noise ratio, but also increase the detection dimension and range, reduce the detection waiting time, and improve the detection efficiency.

[0005] The present invention adopts the following technical solution:

[0006] On the one hand, a water body laser radar based on coded pulses includes: a high-power laser, a coded pulse laser conversion device, a collimating coupler, a transceiver telescope module, a filter, a detector, a collection module and a calculation module;

[0007] The coded pulse laser conversion device converts the high-power laser generated by the high-power laser into a coded pulse laser. The coded pulse laser is coupled into an optical fiber through a collimating coupler and then incident into a water body through a transmitting telescope in a transceiver telescope module. An echo signal generated by the interaction between the emitted laser and the water body is received by a receiving telescope in the transceiver telescope module. The echo signal is filtered by a filter and then enters a detector. The detector converts the echo light signal into an electrical signal. The electrical signal is collected by a collection module, and the collected digital signal is processed by a calculation module and then inverted to obtain water body and target detection information.

[0008] Preferably, the coded pulse laser conversion device converts the high-power continuous laser into the coded pulse laser in a modulation manner; the coded pulse laser conversion device includes an optical modulator and a coded waveform generating device; the high-power laser is a near-infrared band high-power continuous laser; the water body laser radar also includes a frequency multiplier;

[0009] The near-infrared band high-power continuous laser generates near-infrared band high-power continuous laser, the coded waveform generating device drives the optical modulator to modulate the near-infrared band continuous laser into coded pulse laser, and the coded pulse laser enters the frequency doubler to generate blue-green band coded pulse laser suitable for water body detection after double frequency.

[0010] The coding waveform generating device comprises a coding generator and a waveform generator; the coding generator generates a unipolar Golay complementary code sequence and drives the waveform generator to generate a unipolar Golay complementary code sequence pulse waveform; the waveform generator drives the optical modulator to modulate a near-infrared band high-power continuous laser into a Golay coded pulse laser.

[0011] Preferably, the coded pulse laser conversion device converts the high-power laser into the coded pulse laser in a physical manner; the high-power laser is a high-power continuous laser in the blue-green band; the coded pulse laser conversion device includes two coded pulse laser conversion devices; the collimating coupler includes a first collimating coupler and a second collimating coupler; the transceiver telescope module includes a first transceiver telescope module and a second transceiver telescope module; the filter includes a first filter and a second filter; the detector includes a first detector and a second detector; the acquisition module is a multi-channel acquisition module; the water laser radar also includes a focusing system;

[0012] The blue-green band high-power continuous laser generated by the blue-green band high-power continuous laser is focused by the focusing system to generate a focused beam, which is converted into two coded pulse lasers by the two-channel coded pulse laser conversion device, namely a first channel space pulse laser and a second channel space pulse laser; the first channel space pulse laser is coupled into the optical fiber by the first collimating coupler, and is incident into the water body through the transmitting telescope in the first transceiver telescope module; the second channel space pulse laser is coupled into the optical fiber by the second collimating coupler, and is incident into the water body through the transmitting telescope in the second transceiver telescope module;

[0013] A first echo signal generated by the interaction between the first laser and the water body is received by a receiving telescope in the first transceiver telescope module, and a second echo signal generated by the interaction between the second laser and the water body is received by a receiving telescope in the second transceiver telescope module; the first echo signal is filtered by a first filter and then enters a first detector, and the second echo signal is filtered by a second filter and then enters a second detector, the first detector is used to convert the first echo signal into a first electrical signal, and the second detector is used to convert the second echo signal into a second electrical signal, and the multi-channel acquisition module collects the first electrical signal and the second electrical signal and processes them through a calculation module and then inverts them to obtain water body and target detection information.

[0014] Preferably, the coded pulse laser conversion device converts the high-power laser into the coded pulse laser in a physical manner; the high-power laser is a blue-green band high repetition frequency pulse laser; the coded pulse laser conversion device includes two-way coded pulse laser conversion devices; the collimation coupler includes a first collimation coupler and a second collimation coupler; the transceiver telescope module includes a first transceiver telescope module and a second transceiver telescope module; the filter includes a first filter and a second filter; the detector includes a first detector and a second detector; the acquisition module is a multi-way acquisition module; the water body laser radar also includes a focusing system; the water body laser radar also includes a frequency synchronization device;

[0015] The blue-green band high repetition frequency pulse laser generated by the blue-green band high repetition frequency pulse laser is focused by the focusing system to generate a focused light beam, which is converted into two coded pulse lasers by the two-way coded pulse laser conversion device, namely the first spatial pulse laser and the second spatial pulse laser; the frequency synchronization device controls the pulse repetition frequency of the blue-green band high repetition frequency pulse laser to be an integer multiple of the pulse coding frequency of the coded pulse conversion device; the first spatial pulse laser is coupled into the optical fiber through the first collimating coupler, and is incident into the water body through the transmitting telescope in the first transceiver telescope module; the second spatial pulse laser is coupled into the optical fiber through the second collimating coupler, and is incident into the water body through the transmitting telescope in the second transceiver telescope module;

[0016] A first echo signal generated by the interaction between the first laser and the water body is received by a receiving telescope in the first transceiver telescope module, and a second echo signal generated by the interaction between the second laser and the water body is received by a receiving telescope in the second transceiver telescope module; the first echo signal is filtered by a first filter and then enters a first detector, and the second echo signal is filtered by a second filter and then enters a second detector, the first detector is used to convert the first echo signal into a first electrical signal, and the second detector is used to convert the second echo signal into a second electrical signal, and the multi-channel acquisition module collects the first electrical signal and the second electrical signal and processes them through a calculation module and then inverts them to obtain water body and target detection information.

[0017] Preferably, the two-path coded pulse laser conversion device includes a high-speed motor, a coding turntable, a branch turntable, and a synchronous shaft; the coding turntable is punched on the disc according to two groups of identical Golay complementary code sequences, each with 4 code groups arranged alternately; the branch turntable alternately transmits the coded pulse laser and reflects the coded pulse laser according to the arched areas corresponding to the 8 code group holes of the coding turntable; the high-speed motor fixes the coding turntable through the synchronous shaft and the clamp; the synchronous shaft connects the high-speed motor, the coding turntable and the branch turntable, and the high-speed motor drives the coding turntable and the branch turntable to rotate synchronously through the synchronous shaft, the coding turntable is perpendicular to the synchronous shaft, and the branch turntable forms an angle of 45 degrees with the synchronous shaft, so that the projections of the 8 sectors corresponding to the coding turntable and the branch turntable in the horizontal direction always remain overlapping when they rotate; the branch turntable divides the coded pulse laser generated by the coding turntable into two paths through the hollow area and the reflection area, the hollow area transmits the first group of coded pulse laser to generate the first path of coded pulse laser, and the reflection area reflects the second group of coded pulse laser to generate the second path of coded pulse laser.

[0018] Preferably, the formula for obtaining the diameter dt of the encoding disc is as follows:

[0019] dt={[N*dr+(N-1)d] / 1000+dc}*8 / π+2*dw

[0020] The formula for obtaining the laser pulse duration pt of the encoding disk (162) is as follows:

[0021] pt=1 / Rd / 60 / {[N*dr+(N-1)d] / 1000+dc)*8}*1000*dr / 1000000000

[0022] Among them, Rd represents the rotation speed; N represents the Golay code group length; dr represents the diameter of the circular hole; d represents the circular hole spacing; dc represents the code group spacing; dw represents the distance between the center of the circular hole and the edge of the turntable.

[0023] Preferably, the focusing system comprises a collimating lens and a focusing lens, and the diameter of the focused light spot is 10-50 μm.

[0024] In a second aspect, a coded pulse laser generating method comprises:

[0025] Near-infrared band high-power continuous laser produces near-infrared band high-power continuous laser;

[0026] A coding waveform generating device composed of a coding generator and a waveform generator drives an optical modulator to modulate a near-infrared band continuous laser into a coded pulse laser;

[0027] Specifically, the code generator generates a unipolar Golay complementary code sequence and drives the waveform generator to generate a unipolar Golay complementary code sequence pulse waveform; the waveform generator drives the optical modulator to modulate a near-infrared band high-power continuous laser into a Golay coded pulse laser.

[0028] In a third aspect, a coded pulse laser generating method comprises:

[0029] The blue-green band high-power continuous laser generated by the blue-green band high-power continuous laser is focused by a focusing system to generate a focused beam, which is converted into a two-channel coded pulse laser by a two-channel coded pulse laser conversion device;

[0030] Specifically, the two-path coded pulse laser conversion device includes a high-speed motor, a coding turntable, a branch turntable, and a synchronous shaft; the coding turntable is punched on a disc according to two groups of identical Golay complementary code sequences, each with 4 code groups arranged alternately; the branch turntable alternately transmits and reflects the coded pulse laser according to the arched areas corresponding to the 8 code group holes of the coding turntable; the synchronous shaft connects the high-speed motor, the coding turntable and the branch turntable, and the high-speed motor drives the coding turntable and the branch turntable to rotate synchronously through the synchronous shaft, the coding turntable is perpendicular to the synchronous shaft, and the branch turntable forms an angle of 45 degrees with the synchronous shaft, so that the projections of the 8 sectors corresponding to the coding turntable and the branch turntable in the horizontal direction always remain overlapping when they rotate.

[0031] In a fourth aspect, a coded pulse laser generating method comprises:

[0032] The blue-green band high repetition frequency pulse laser generated by the blue-green band high repetition frequency pulse laser is focused by a focusing system to generate a focused beam, which is converted into a two-way coded pulse laser by a two-way coded pulse laser conversion device. The frequency synchronization device controls the pulse repetition frequency of the blue-green band high repetition frequency pulse laser to be an integral multiple of the pulse coding frequency of the two-way coded pulse conversion device.

[0033] Specifically, the two-path coded pulse laser conversion device includes a high-speed motor, a coding turntable, a branch turntable, and a synchronous shaft; the coding turntable is punched on a disc according to two groups of identical Golay complementary code sequences, each with 4 code groups arranged alternately; the branch turntable alternately transmits and reflects the coded pulse laser according to the arched areas corresponding to the 8 code group holes of the coding turntable; the synchronous shaft connects the high-speed motor, the coding turntable and the branch turntable, and the high-speed motor drives the coding turntable and the branch turntable to rotate synchronously through the synchronous shaft, the coding turntable is perpendicular to the synchronous shaft, and the branch turntable forms an angle of 45 degrees with the synchronous shaft, so that the projections of the 8 sectors corresponding to the coding turntable and the branch turntable in the horizontal direction always remain overlapping when they rotate.

[0034] The beneficial effects of the present invention are as follows:

[0035] (1) The present invention generates coded pulse laser based on a coded pulse laser conversion device. When the modulation method is adopted, the coded pulse laser conversion device is composed of a coded waveform generating device and an optical modulator. The high-power continuous laser passes through the coded pulse laser conversion device to generate a blue-green band coded pulse laser suitable for water body detection. It can not only improve the average emission power of the pulse laser, but also generate coding-related gain by encoding the laser pulse, remove background noise, and improve the system signal-to-noise ratio, thereby realizing long-distance and weak signal target detection of the pulse laser radar. At the same time, due to the maturity of continuous laser devices, there are more selectable bands and wider applicability, which can meet the detection needs of different water scenes;

[0036] (2) When the present invention is implemented in a physical way, the coded pulse laser conversion device is composed of a coding turntable, a branch turntable, a high-speed motor and a synchronous shaft. Through the reasonable design of the coding turntable and the branch turntable, compared with the single-repetition pulse laser radar system, it can not only improve the system signal-to-noise ratio, but also increase the detection dimension and range, reduce the detection waiting time, and improve the detection efficiency.

[0037] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0039] Figure 1This is an optical path diagram of a water body laser radar that adopts a modulated coded pulse laser conversion method and has coaxial transmitting and receiving telescopes according to Example 1 of the present invention;

[0040] Figure 2 This is an optical path diagram of a water body laser radar that adopts a modulated coded pulse laser conversion method and has separate transmitting and receiving telescopes according to embodiment 2 of the present invention;

[0041] Figure 3 This is an optical path diagram of a water body laser radar that adopts a physical coded pulse laser conversion method and has coaxial transmitting and receiving telescopes according to embodiment 3 of the present invention;

[0042] Figure 4 Schematic diagram of coded pulse laser generation according to Example 3 of the present invention; wherein (a) is a structural diagram of a two-channel coded pulse conversion device; (b) is a schematic diagram of generating a first channel coded pulse laser; (c) is a schematic diagram of generating a second channel coded pulse laser;

[0043] Figure 5 It is a schematic diagram of the time domain waveform and autocorrelation sum of bipolar Golay complementary code sequences A and B;

[0044] Figure 6 is a unipolar Golay complementary code sequence A 1 , A 2 , B 1 , B 2 The time domain waveform diagram of

[0045] Figure 7 The water response echo signal of a single laser pulse is used to simulate the water response echo signal and decoding result of the Golay complementary code sequence encoded laser pulse; (a) represents the echo signal obtained by emitting a single laser pulse through the water body response, and the peak is the response of the hard target; (b) represents the single polarity Golay complementary code sequence A after 8-bit offset 1 , A 2 , B 1 , B 2 The waveform of the coded laser pulse in the time domain; (c) represents the simulated 8-bit unipolar Golay complementary code sequence A 1 , A 2 , B 1 , B 2 The coded laser pulse returns an echo signal after passing through the water body;

[0046] Figure 8 Comparison of received echo signals; (a) represents the echo signal of a single laser pulse; (b) represents the decoding result of an 8-bit unipolar Golay coded pulse echo signal;

[0047] Fig. 9is the comparison of the received echo signal after normalization; where (a) represents Figure 8 (a) is the normalized result; (b) indicates Figure 8 (b) Normalized results;

[0048] Fig.10 It is a schematic diagram of the implementation method of the encoding turntable;

[0049] Fig.11 Schematic diagram of the positional relationship between the energy of the laser beam passing through two adjacent circular holes on the encoding disk and the time t;

[0050] Fig.12 The pulse waveform diagram in the time domain formed by the laser beam passing through two adjacent circular holes on the encoding disk when d=2r;

[0051] Fig.13 A schematic diagram of a two-way 8-bit Golay complementary code sequence encoding turntable provided in Example 3 of the present invention;

[0052] Fig.14 A schematic diagram of a two-way 8-bit Golay complementary code sequence split turntable provided in Example 3 of the present invention;

[0053] Fig.15 A normalized waveform diagram of a first channel of coded pulse laser and a second channel of coded pulse laser generated in the time domain according to Embodiment 3 of the present invention, wherein the waveform diagram includes two channels of 8-bit unipolar Golay complementary code sequence pulses;

[0054] Fig.16 This is an optical path diagram of a water body laser radar that adopts a physical coded pulse laser conversion method and has separate transmitting and receiving telescopes according to Example 4 of the present invention;

[0055] Fig.17 This is an optical path diagram of a water body laser radar that adopts a physical coded pulse laser conversion method according to embodiment 5 of the present invention, where the laser source is a pulse laser and the transmitting and receiving telescopes are coaxial;

[0056] Fig.18 This is an optical path diagram of a water body laser radar that adopts a physical coded pulse laser conversion method according to embodiment 6 of the present invention, where the laser source is a pulse laser and the transmitting and receiving telescopes are separated;

[0057] Fig.19 The laser pulses generated by the pulse lasers of Examples 5 and 6 of the present invention are normalized waveform diagrams in the time domain of the first coded pulse laser and the second coded pulse laser generated by the two-channel coded pulse conversion device, and the waveform diagram includes two 8-bit unipolar Golay complementary code sequence pulses. DETAILED DESCRIPTION

[0058] The following is a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the present invention.

[0059] Example 1

[0060] See also Figure 1 As shown, this embodiment adopts a modulated coded pulse laser conversion method, and the transceiver telescope module of this embodiment is a transceiver coaxial telescope structure.

[0061] Specifically, a water body laser radar based on coded pulses includes:

[0062] A near-infrared band high-power continuous laser 1, an optical modulator 2, a coded waveform generating device 3, a frequency multiplier 4, a collimating coupler 5, an optical signal branching module 6, a transceiver coaxial telescope 7, a filter 8, a detector 9, a collection module 10 and a calculation module 11.

[0063] Among them, the near-infrared band high-power continuous laser 1 generates a near-infrared band high-power continuous laser with a central wavelength of 1064nm (the wavelength range of the infrared band high-power continuous laser is 800nm-1100nm, the average power is greater than 100W, and 1064nm is selected in this embodiment), the coded waveform generating device 3 is composed of a code generator and a waveform generator, the code generator generates a code sequence, the code generator drives the waveform generator to generate a code sequence pulse waveform, and the code sequence pulse waveform generated by the waveform generator drives the optical modulator 2 to modulate the near-infrared band continuous laser into a coded pulse laser, and the coded pulse laser enters the frequency multiplier 4 for double frequency to generate a green light band coded pulse laser with a central wavelength of 532nm suitable for water body detection. The spatial laser is coupled into the optical fiber through the collimating coupler 5, and the collimating coupler 5 is connected to the optical signal branching module 6 through the optical fiber. The green light band coded pulse laser is incident into the water body through the transceiver coaxial telescope 7 after passing through the optical signal branching module 6.

[0064] The echo signal generated by the interaction between the emitted laser and the water body is received by the transceiver coaxial telescope 7, and the echo signal passes through the optical signal splitting module 6 and the filter 8 to filter out the background noise of the sun and the sky, and then enters the detector 9, which converts the echo light signal into an electrical signal. The electrical signal is collected by the acquisition module 10, and the collected digital signal is processed by the calculation module 11 and then inverted to obtain the water body and target detection information.

[0065] In this example, the optical signal branching module 6 includes a fiber optic circulator or an optical switch, that is, the optical signal branching module 6 can be any one of the fiber optic circulators or optical switches. Of course, it can also be other devices with equivalent functions, and this example does not make specific limitations.

[0066] In this embodiment, the code sequence generated by the code generator selects codes with strong autocorrelation to obtain a high code correlation gain.

[0067] In this example, the optical modulator 2 includes an acousto-optic modulator and an electro-optic modulator.

[0068] In summary, the conversion of continuous laser into coded pulse laser by modulation is achieved by driving the optical modulator 2 with the coded waveform generator 3. The near-infrared band continuous laser 1 generates near-infrared continuous laser (for example, wavelength 864nm or 1064nm), the coded waveform generator 3 is composed of a code generator and a waveform generator, the code generator generates a unipolar Golay complementary code sequence, the code generator drives the waveform generator to generate a unipolar Golay complementary code sequence pulse waveform, the pulse waveform generated by the waveform generator drives the optical modulator (AOM or EOM) to modulate the near-infrared continuous laser into a Golay coded pulse laser, and after being doubled by the frequency multiplier 4, a blue-green band Golay coded pulse laser is generated (corresponding to the continuous laser with a wavelength of 864nm, the wavelength of the pulse laser obtained by doubled frequency is 432nm, and corresponding to the continuous laser with a wavelength of 1064nm, the wavelength of the pulse laser obtained by doubled frequency is 532nm).

[0069] Example 2

[0070] See also Figure 2 As shown, this embodiment adopts a modulated coded pulse laser conversion method, and the transceiver telescope module of this embodiment is a transceiver separated telescope structure, that is, it includes an independently arranged transmitting telescope and a receiving telescope. When the transceiver separated optical telescope structure is adopted, two optical fibers are required, one optical fiber connects the collimating coupler and the transmitting telescope, and the other optical fiber connects the receiving telescope and the filter.

[0071] Specifically, a water body laser radar based on coded pulses includes:

[0072] A near-infrared band high-power continuous laser 1, an optical modulator 2, a coded waveform generating device 3, a frequency multiplier 4, a collimating coupler 5, a transmitting telescope 12, a receiving telescope 13, a filter 8, a detector 9, a collection module 10, and a calculation module 11.

[0073] Among them, the near-infrared band high-power continuous laser 1 generates a near-infrared band high-power continuous laser with a central wavelength of 1064nm (the wavelength range of the infrared band high-power continuous laser is 800nm-1100nm, and the average power is greater than 100W. 1064nm is selected in this embodiment). The coded waveform generating device 3 is composed of a coding generator and a waveform generator. The coded waveform generating device 3 drives the optical modulator 2 to modulate the near-infrared band continuous laser into a coded pulse laser. The coded pulse laser enters the frequency multiplier 4 for double frequency to generate a green light band coded pulse laser with a central wavelength of 532nm suitable for water body detection. The space laser is coupled into the optical fiber through the collimating coupler 5. The collimating coupler 5 is connected to the transmitting telescope 12 through the optical fiber. The green light band coded pulse laser is incident into the water body through the transmitting telescope 12.

[0074] The echo signal generated by the interaction between the outgoing laser and the water body is received by the receiving telescope 13. The echo signal passes through the filter 8 to filter out the background noise of the sun and the sky and then enters the detector 9. The detector 9 converts the echo light signal into an electrical signal. The electrical signal is collected by the acquisition module 10, and the collected digital signal is processed by the calculation module 11 and then inverted to obtain the water body and target detection information.

[0075] The specific structure and implementation of other parts of this embodiment are the same as those of Embodiment 1 and will not be repeated here.

[0076] Example 3

[0077] See also Figure 3 As shown, this embodiment adopts a physical coded pulse laser conversion method, and the transceiver telescope module of this embodiment is a transceiver coaxial telescope structure.

[0078] Specifically, a water body laser radar based on coded pulses includes:

[0079] A blue light band high-power continuous laser 14, a focusing system 15, a two-way coded pulse conversion device 16, a first collimating coupler 17, a first optical signal branching module 18, a first transceiver coaxial telescope 19, a first filter 20, a first detector 21, a second collimating coupler 22, a second optical signal branching module 23, a second transceiver coaxial telescope 24, a second filter 25, a second detector 26, a multi-channel acquisition module 27, and a calculation module 28.

[0080] The blue light band high power continuous laser 14 generates a blue light band high power continuous laser with a central wavelength of 445-465nm (the wavelength range of the blue-green band high power continuous laser is 400nm-560nm, and the average power is greater than 100W. This embodiment uses the 445-465nm blue light band). The focusing system 15 is composed of a collimator and a focusing lens. After the blue light band laser is collimated by the collimator, it is focused to a light spot of 10-50μm by the focusing lens, and is converted into a two-channel coded pulse laser by a two-channel coded pulse laser conversion device 16. The first channel of spatial pulse laser is coupled into the optical fiber by the first collimator coupler 17. The first collimator coupler 17 is connected to the first optical signal branching module 18 by an optical fiber. After passing through the first optical signal branching module 18, the first channel of pulse laser is incident into the water body through the first transceiver coaxial telescope 19. The second spatial pulse laser is coupled into the optical fiber through the second collimating coupler 22, and the second collimating coupler 22 is connected to the second optical signal branching module 23 through the optical fiber. After passing through the second optical signal branching module 23, the second pulse laser is incident into the water body through the second transceiver coaxial telescope 24.

[0081] The echo signal generated by the interaction between the first outgoing laser and the water body is received by the first transceiver coaxial telescope 19. The echo signal is filtered by the first filter 20 through the first optical signal branching module 18 and then enters the first detector 21. The echo signal generated by the interaction between the second outgoing laser and the water body is received by the second transceiver coaxial telescope 24. The echo signal is filtered by the second optical signal branching module 23 through the second filter 25 and then enters the second detector 26. The first detector 21 and the second detector 26 are used to convert the echo optical signal into an electrical signal. The two electrical signals enter the multi-channel acquisition module 27 and are collected by the multi-channel acquisition module 27. The collected digital signals are processed by the calculation module 28 and then inverted to obtain the water body and target detection information corresponding to the two echo signals.

[0082] In this example, the first optical signal branching module 18 and the second optical signal branching module 23 include a fiber optic circulator and an optical switch, that is, the first optical signal branching module 18 and the second optical signal branching module 23 can be any one of a fiber optic circulator or an optical switch. Of course, they can also be other devices with equivalent functions, and this example does not make any specific limitations.

[0083] See also Figure 4As shown, the two-channel coded pulse laser conversion device 16 in this example is composed of a high-speed motor 161, a coding turntable 162, a branch turntable 163 and a synchronous shaft 164. The blue-band high-power continuous laser 14 generates a blue-band high-power continuous laser, which is collimated by a collimator and focused to a light spot of 10-50 μm by a focusing lens. The laser beam focal spot passes through the circular holes arranged according to the code on the coding turntable 162 driven by the high-speed motor 161. The coding turntable 162 rotates one circle to generate two groups of coded pulse lasers, one group is transmitted through the branch turntable 163, and the other group is reflected by the branch turntable 163, thereby generating two channels of blue-green band spatial pulse lasers suitable for water body detection.

[0084] A series of small circular holes (code group circular holes 1621) are arranged in a certain coding manner near the outer edge of the circumference of the encoder disk 162. The centers of these circular holes are located on a concentric circle with the encoder disk 162 (i.e., the distances from the centers of the circular holes to the center of the encoder disk are all equal). When the encoder disk 162 rotates, the laser beam 151 emitted by the focusing system 15 passes through the circular holes and appears as a laser pulse in time. The circular holes on the encoder disk 162 are punched and arranged according to the selected code with strong autocorrelation to obtain code correlation gain.

[0085] The following codes are available for selection:

[0086] (1) Golay complementary code sequence;

[0087] (2) Pseudo-random (PN) code sequence (m sequence and M sequence);

[0088] (3) Chaotic sequence;

[0089] (4) Minimum peak sidelobe (MPS) sequence;

[0090] (5) Complementary Related Promethean Standard Orthogonal Sequences (CCPONS);

[0091] (6) Simplex code sequence.

[0092] The Golay complementary code sequence has the following advantages:

[0093] (1) The correlation value outside the main correlation peak is 0 (ie, the side lobe is 0). Ideally, the Golay complementary code sequence is decoded without distortion, so the Golay complementary code sequence can obtain the highest coding correlation gain under the same coding length.

[0094] (2) Sequence balance (the number of "1" and "-1" is equal). Under this condition, the background noise superimposed on the echo signal that satisfies the stationary random process can be removed by correlation operation;

[0095] (3) Code group sequences of various lengths can be generated by iterative methods, and the physical hardware implementation is relatively simple.

[0096] Since other encoding methods cannot simultaneously satisfy the above three conditions, this embodiment selects a Golay complementary code sequence as a coding sequence to puncture the coding wheel 162 to generate a coded pulse laser.

[0097] The Golay complementary code sequence consists of two sequences of order n and length N = 2 n , consisting of bipolar sequences A and B containing "1" and "-1", sequences A and B satisfy the following relationship:

[0098]

[0099] Wherein, “*” represents the correlation operation, k is the shift value of the correlation operation, and when k=0, the two sequences subjected to the correlation operation are aligned, at which time the sum of the autocorrelation values ​​of sequences A and B is the largest.

[0100] Golay complementary codes are generated using the following iterative rules:

[0101]

[0102] Among them, “|” means connecting two sequences. Represents the reverse polarity code of B, that is, replace "1" in sequence B with "-1", and "-1" with "1" to obtain the sequence

[0103] The iterative initial sequence of order 0 and length 1 is:

[0104]

[0105] For example, the bipolar Golay complementary code sequences of length N = 2 and N = 4 are:

[0106]

[0107] Taking length N=8 as an example, its bipolar Golay complementary code sequence is:

[0108]

[0109] The time domain waveform and autocorrelation sum of bipolar Golay complementary code sequences A and B can be found in Figure 5 shown.

[0110] Since the laser radar can only transmit positive polarity (“1”) pulses, it is necessary to bias the bipolar Golay complementary code sequence to obtain 4 sets of unipolar (“1” and “0”) code sequences A 1 , A 2 , B1 , B 2 , the bias formula is as follows:

[0111]

[0112] Right now:

[0113]

[0114] Taking N=8 as an example, the bipolar Golay complementary code sequence is converted into a unipolar Golay complementary code sequence after biasing:

[0115]

[0116] Unipolar Golay complementary code sequence A 1 , A 2 , B 1 , B 2 The time domain waveform of Figure 6 shown.

[0117] The laser radar transmitter transmits a single polarity Golay complementary code pulse sequence A 1 , A 2 , B 1 , B 2 When it reaches the water body, the receiver divides the echo signal in the time domain according to the synchronization trigger signal and the Golay code group length, and intercepts the echo signal to obtain 4 groups of echo signals that are consistent with the transmission sequence A. 1 , A 2 , B 1 , B 2 The corresponding received signal A 1 ′、A 2 ′、B 1 ′、B 2 ′, assuming that the total channel impulse response between the water body and the receiver is h k , ignoring other noises, the decoding formula of the echo signal is as follows:

[0118]

[0119]

[0120] Among them, "*" represents related operations. represents the convolution operation, and Z is the final decoding result. It can be seen that, in theory, after the Golay complementary code coded pulse passes through the water body and the receiver's response, the decoded result is 2N times the channel impulse response of the water body and the receiver.

[0121] The water body response echo signal of a single laser pulse is used to simulate the water body response echo signal and decoding result of the Golay complementary code sequence encoded laser pulse. Figure 7 (a) shows the echo signal obtained by emitting a single laser pulse through the water body, and the peak is the response of the hard target. Figure 7 (b) represents the 8-bit unipolar Golay complementary code sequence A after 8-bit offset 1 , A 2 , B 1 , B 2 The waveform of the coded laser pulse in the time domain. The interval between the four code group sequences is the time length of the single pulse echo signal (to prevent signal overlap between code groups). Figure 7 (c) represents the simulation of 8-bit unipolar Golay complementary code sequence A 1 , A 2 , B 1 , B 2 The coded laser pulse returns an echo signal after passing through the water body.

[0122] Figure 8 (a) and 8(b) are the comparisons between the decoding results of the echo signal of a single laser pulse and the echo signal of an 8-bit unipolar Golay coded pulse. The maximum values ​​of the peaks in the two figures are 148788 and 2380608, respectively, which are exactly 16 times the ratio. That is, when the Golay complementary code sequence is used to encode the laser pulse as the transmitting signal, the coding correlation gain generated is 2N times that of a single laser pulse in terms of the energy amplitude of the received signal.

[0123] Fig. 9 (a) and Fig. 9 (b) respectively represent Figure 8 The results of normalization of the two signals (a) and (b) show that the waveform of the echo signal after the single laser pulse responds to the water body is exactly the same as the waveform of the decoded echo signal of the laser pulse water body response encoded by the 8-bit single-polarity Golay complementary code sequence. That is, in an ideal case, the decoding of the Golay coded pulse echo signal is not distorted.

[0124] As mentioned above, in this embodiment, when a physical method is adopted, the conversion of continuous laser into pulsed laser by two-way coded pulse laser conversion device 16 is realized by coding disk 162. Taking the Golay complementary code sequence of length N=8 as an example, the coding disk is designed, and the unipolar Golay complementary code sequence is arranged in a "circular hole" manner near the outer circumference of the coding disk, and the distances from the center of these circular holes to the center of the coding disk are equal. The implementation method of coding disk 162 can be found in Fig.10As shown, the solid circle indicates a hole is punched and the laser can pass through (indicating "1"), and the hollow circle indicates no hole is punched and the laser cannot pass through (indicating "0"). The blue light band high-power continuous laser 14 and the focusing system 15 are fixed in position, the axis of the focusing system 15 is perpendicular to the encoding turntable 162, and the laser focus spot is fixed at a certain position on the circumference of the circular hole. When the high-speed motor 161 drives the encoding turntable 162 to rotate through the synchronous rotating shaft 164, when the laser beam is rotated to be within the circular hole, the laser beam passes through the circular hole and forms a pulse in the time domain.

[0125] When the distance d between two adjacent circular holes takes different values, the positional relationship between the energy of the laser beam passing through the two circular holes (expressed by the area of ​​the spot circle, that is, the laser beam passing through the circular holes forms a pulse in the time domain) and the time t is shown in Fig.11 As shown, d = r at this time. Set the circular hole radius r = 10, the laser focus spot size is equal to the circular hole size (the focus spot radius should be less than or equal to the circular hole radius to ensure that the laser beam passes through the circular hole), and the focus spot moves from left to right on the axis where the centers of the two circular holes are located. In the schematic diagram, the focus spot now moves to the center position between the centers of the two circular holes. The relationship between the spacing d between two adjacent circular holes and the circular hole radius r and the pulse formed by the laser beam passing through the two circular holes is as follows:

[0126] (1) When 0≤d<2r, the two pulses formed by the laser beam passing through the two circular holes overlap in the time domain.

[0127] (2) When d ≥ 2r, the two pulses formed by the laser beam passing through the two circular holes are separated and do not overlap in the time domain. Fig.12 It represents the pulse waveform in the time domain formed when the laser beam passes through two circular holes when d=2r. At this time, the two pulses do not overlap.

[0128] Considering that the spacing d between the circular holes affects the design size of the encoder disk, when the circular hole size and encoding length are the same, the larger the circular hole spacing, the larger the disk size. Therefore, the spacing between the two circular holes takes the minimum value that meets the non-overlapping condition, that is:

[0129] d=2r

[0130] Assuming that the maximum detection distance of the laser radar is L, the spacing Cd between the four code groups of the unipolar Golay complementary code sequence is required to satisfy the following relationship to ensure that the echo signals of two adjacent code group pulses do not overlap and the receiving end can decode correctly, that is:

[0131] Cd≥L

[0132] However, if Cd and L satisfy the above relationship, the duty cycle of the pulse signal in the time domain will be very low. Similar to the single-repetition pulse laser radar, the interval between two adjacent code group pulses (i.e., the detection waiting time) must also be left according to the above relationship to avoid the overlap of the echo signals of two adjacent code group pulses. In order to improve the detection efficiency, two sets of identical Golay code group sequences A 1 , A 2 , B 1 , B 2 and AA 1 AA 2 BB 1 BB 2 Cross combination, press A 1 AA 1 , A 2 AA 2 , B 1 BB 1 , B 2 BB 2 The order is arranged on the coding disk, see Fig.13 As shown, the two groups of Golay code groups are separated by a subsequent splitter disk and divided into two pulse laser emissions, thereby improving the detection efficiency.

[0133] After the laser passes through the circular hole on the encoding disk 162, it is divided into two paths of coded pulse laser emission through the branching disk 163. Fig.14 shown.

[0134] The arched through hole 1631 is hollowed out to allow the pulse laser generated by the encoder disk 162 to pass through, generating the first route Golay complementary code sequence A 1 , A 2 , B 1 , B 2 Encoded pulse laser; the arched reflector 1632 can reflect the pulse laser generated by the encoding turntable 162 to generate a second route Golay complementary code sequence AA 1 AA 2 BB 1 BB 2 Coded pulsed laser.

[0135] The encoder disk 162 is perpendicular to the shaft of the high-speed motor 161, and the branch disk 163 is at a 45-degree angle to the shaft of the high-speed motor 161. The encoder disk 162 and the branch disk 163 are connected by a synchronous shaft to ensure synchronous rotation, that is, to ensure that the A on the two disks 1 AA 1 , A 2 AA 2 , B 1 BB 1 , B2 BB 2 The projections of these eight sectors in the horizontal direction always overlap when they rotate. The principle diagram of the physical encoding pulse conversion device composed of a high-speed motor 161, an encoding disk 162, a branching disk 163 and a synchronous shaft 164 is shown in FIG. Figure 4 The process of the laser beam 151 passing through the encoding disk 162 and then passing through the arched through hole 1631 of the branching disk 163 to generate the first coded pulse laser is shown in FIG. Figure 4 As shown in (b), the laser beam 151 passes through the encoding disk 162 and is reflected by the arched reflector lens 1632 of the branching disk 163 to generate the second encoded pulse laser. Figure 4 (c) as shown.

[0136] When the focused continuous laser beam passes through Fig.13 The encoding disk 162 and the encoding disk 164 shown are punctured by a Golay complementary code sequence of length N=8. Fig.14 After the branching disk 163 is shown, the normalized waveforms of the first coded pulse laser and the second coded pulse laser generated in the time domain are as follows: Fig.15 As shown, at this time, the relationship between the circular hole spacing d and the circular hole radius r on the encoding disk is set to d=2r.

[0137] Table 1 shows some relationships among the encoder disk speed (i.e., high-speed motor speed), Golay code group length, circular hole diameter, circular hole spacing, encoder disk diameter, and laser pulse duration.

[0138] Table 1

[0139]

[0140] As can be seen from Table 1, when the speed of the high-speed motor is determined, the size of the encoder turntable is mainly determined by the Golay code group length, the circular hole diameter and the circular hole spacing, but it is also necessary to consider factors such as the motor power, the size of the entire laser radar system, the difficulty and accuracy of laser micro-hole processing, and the stability of the turntable rotation. Taking the above factors into consideration, the encoder turntable is more suitable at 100mm-150mm. After the size of the encoder turntable is determined, the higher the motor speed, the longer the code length or the smaller the circular hole diameter, the shorter the laser pulse duration.

[0141] Specifically, the encoder turntable speed Rd (i.e., the high-speed motor speed, unit rpm), the Golay code group length N, the circular hole diameter dr (unit μm), the circular hole spacing d (calculated according to the circumference of the circular hole center, unit μm), the two sector spacing dc (i.e., the code group spacing, calculated according to the circumference of the circular hole center, unit mm), and the distance dw (unit mm) between the circular hole center and the turntable edge are set. The calculation formula and relationship of the encoder turntable diameter dt (unit mm) and the laser pulse duration pt (i.e., the system resolution, unit ns) are as follows:

[0142] dt={[N*dr+(N-1)d] / 1000+dc}*8 / π+2*dw (7)

[0143] pt=1 / Rd / 60 / {[N*dr+(N-1)d] / 1000+dc)*8}*1000*dr / 1000000000 (8)

[0144] Table 1 only lists the cases where the encoder disk rotates 60,000 times and 120,000 times. The other cases can be calculated by equations (7) and (8).

[0145] In this embodiment, when the speed of the high-speed motor 161 is 60,000 rpm, the circular holes on the encoding turntable 162 are coded and punched according to an 8-bit Golay complementary code sequence, the diameter of the circular hole is 1000 μm, the spacing between the circular holes is 1000 μm, the code group spacing is 20 mm, and the distance between the center of the circular hole and the circumferential edge of the turntable is 2 mm. The diameter of the encoding turntable 162 is calculated to be 93.127 mm through the above parameters, and the laser pulse duration is 3571.429 ns.

[0146] Example 4

[0147] See also Fig.16 As shown, this embodiment adopts a physical coded pulse laser conversion method, and the transceiver telescope module of this embodiment is a transceiver separated telescope structure, that is, it includes an independently arranged transmitting telescope and a receiving telescope. When the transceiver separated optical telescope structure is adopted, two optical fibers are required, one optical fiber connects the collimating coupler and the transmitting telescope, and the other optical fiber connects the receiving telescope and the filter.

[0148] Specifically, a water body laser radar based on coded pulses includes:

[0149] A blue light band high-power continuous laser 14, a focusing system 15, a two-way coded pulse conversion device 16, a first collimating coupler 17, a first transmitting telescope 29, a first receiving telescope 30, a first filter 20, a first detector 21, a second collimating coupler 22, a second transmitting telescope 31, a second receiving telescope 32, a second filter 25, a second detector 26, a multi-channel acquisition module 27, and a calculation module 28.

[0150] The blue light band high power continuous laser 14 generates a blue light band high power continuous laser with a central wavelength of 445-465nm (the central wavelength range of the blue-green band high power continuous laser is 400nm-560nm, and the average power is greater than 100W. The present embodiment adopts the 445-565nm blue light band). The focusing system 15 is composed of a collimator and a focusing lens. After the blue light band laser is collimated by the collimator, it is focused to a light spot of 10-50μm by the focusing lens, and is converted into two coded pulse lasers by two 8-bit Golay complementary code sequence coded pulse conversion devices 16. The first spatial pulse laser is coupled into the optical fiber by the first collimator coupler 17. The first collimator coupler 17 is connected to the first transmitting telescope 29 by an optical fiber. The first pulse laser is incident into the water body by the first transmitting telescope 29. The second spatial pulse laser is coupled into the optical fiber via the second collimating coupler 22 . The second collimating coupler 22 is connected to the second transmitting telescope 31 via the optical fiber. The second pulse laser is incident into the water body via the second transmitting telescope 31 .

[0151] The echo signal generated by the interaction between the first outgoing laser and the water body is received by the first receiving telescope 30. The echo signal enters the first detector 21 after being filtered by the first filter 20. The echo signal generated by the interaction between the second outgoing laser and the water body is received by the second receiving telescope 32. The echo signal enters the second detector 26 after being filtered by the second filter 25. The first detector 21 and the second detector 26 are used to convert the echo light signal into an electrical signal. The two electrical signals enter the multi-channel acquisition module 27 and are collected by the multi-channel acquisition module 27. The collected digital signals are processed by the calculation module 28 and then inverted to obtain the water body and target detection information corresponding to the two echo signals.

[0152] See also Figure 4As shown, the two-channel coded pulse laser conversion device 16 in this example is composed of a high-speed motor 161, a coding turntable 162, a branch turntable 163 and a synchronous shaft 164. The blue-band high-power continuous laser 14 generates a blue-band high-power continuous laser, which is collimated by a collimator and focused to a light spot of 10-50 μm by a focusing lens. The laser beam focal spot passes through the circular holes arranged according to the code on the coding turntable 162 driven by the high-speed motor 161. The coding turntable 162 rotates one circle to generate two groups of coded pulse lasers, one group is transmitted through the branch turntable 163, and the other group is reflected by the branch turntable 163, thereby generating two channels of blue-band spatial pulse lasers suitable for water body detection.

[0153] Similarly, in this embodiment, when the speed of the high-speed motor is 60,000 rpm, the circular holes on the encoding turntable are coded and punched according to an 8-bit Golay complementary code sequence, the diameter of the circular hole is 1000μm, the spacing between the circular holes is 1000μm, the code group spacing is 20mm, and the distance between the center of the circular hole and the circumferential edge of the turntable is 2mm. The diameter of the encoding turntable is calculated by the above parameters to be 93.127mm, and the laser pulse duration is 3571.429ns.

[0154] The specific structure and implementation of other parts of this embodiment are the same as those of Embodiment 3 and will not be repeated here.

[0155] Example 5

[0156] See also Fig.17 As shown, this embodiment adopts a physical coded pulse laser conversion method, the laser source adopts a high repetition frequency pulse laser, and the pulse repetition frequency of the pulse laser is controlled by a frequency synchronization device to be an integer multiple of the pulse coding frequency of the coded pulse conversion device, so that the laser pulse generated by the pulse laser can just pass through the circular hole on the coding turntable, and the transceiver telescope module of this embodiment is a transceiver coaxial telescope structure.

[0157] Specifically, a water body laser radar based on coded pulses includes:

[0158] A green light band high repetition frequency pulse laser 34, a focusing system 15, a two-way coded pulse conversion device 16, a frequency synchronization device 35, a first collimating coupler 17, a first optical signal branching module 18, a first transceiver coaxial telescope 19, a first filter 20, a first detector 21, a second collimating coupler 22, a second optical signal branching module 23, a second transceiver coaxial telescope 24, a second filter 25, a second detector 26, a multi-channel acquisition module 27, and a calculation module 28.

[0159] Among them, the green light band high repetition frequency pulse laser 34 generates a pulse laser in the green light band with a central wavelength of 532nm. The focusing system 15 is composed of a collimator and a focusing lens. After the green light band pulse laser is collimated by the collimator, it is focused to a light spot of 10-50μm by the focusing lens, and converted into two-way coded pulse lasers by the two-way coded pulse laser conversion device 16. The frequency synchronization device 35 controls the pulse repetition frequency of the pulse laser 34 to be an integer multiple of the pulse coding frequency of the coded pulse conversion device 16. The first spatial pulse laser is coupled into the optical fiber through the first collimator coupler 17. The first collimator coupler 17 is connected to the first optical signal branching module 18 through the optical fiber. After passing through the first optical signal branching module 18, the first pulse laser is incident into the water body through the first transceiver coaxial telescope 19. The second spatial pulse laser is coupled into the optical fiber through the second collimating coupler 22, and the second collimating coupler 22 is connected to the second optical signal branching module 23 through the optical fiber. After passing through the second optical signal branching module 23, the second pulse laser is incident into the water body through the second transceiver coaxial telescope 24.

[0160] The echo signal generated by the interaction between the first outgoing laser and the water body is received by the first transceiver coaxial telescope 19. The echo signal is filtered by the first filter 20 through the first optical signal branching module 18 and then enters the first detector 21. The echo signal generated by the interaction between the second outgoing laser and the water body is received by the second transceiver coaxial telescope 24. The echo signal is filtered by the second optical signal branching module 23 through the second filter 25 and then enters the second detector 26. The first detector 21 and the second detector 26 are used to convert the echo optical signal into an electrical signal. The two electrical signals enter the multi-channel acquisition module 27 and are collected by the multi-channel acquisition module 27. The collected digital signals are processed by the calculation module 28 and then inverted to obtain the water body and target detection information corresponding to the two echo signals.

[0161] In this example, the first optical signal branching module 18 and the second optical signal branching module 23 include a fiber optic circulator and an optical switch, that is, the first optical signal branching module 18 and the second optical signal branching module 23 can be any one of a fiber optic circulator or an optical switch. Of course, they can also be other devices with equivalent functions, and this example does not make any specific limitations.

[0162] See also Figure 4As shown, the two-path coded pulse laser conversion device 16 in this example is composed of a high-speed motor 161, a coding turntable 162, a branch turntable 163 and a synchronous shaft 164. The green light band pulse laser 34 generates a green light band pulse laser, which is collimated by a collimator and focused to a light spot of 10-50 μm by a focusing lens. The laser beam focal spot passes through the circular holes arranged according to the code on the coding turntable 162 driven by the high-speed motor 161. The pulse repetition frequency of the green light band high repetition frequency pulse laser 34 is controlled by the frequency synchronization device 35 to be an integer multiple of the pulse coding frequency of the coded pulse conversion device 16, so that the laser pulse generated by the pulse laser can just pass through the circular holes on the coding turntable. The coding turntable 162 rotates one circle to generate two groups of coded pulse lasers, one group is transmitted through the branch turntable 163, and the other group is reflected by the branch turntable 163, thereby generating two paths of green light band space pulse lasers suitable for water body detection. The normalized waveforms of the first coded pulse laser and the second coded pulse laser generated by the pulse laser generated by the green band high repetition frequency pulse laser 34, the two-channel coded pulse laser conversion device 16 and the frequency synchronization device 35 after controlling the pulse frequency synchronization in the time domain are shown in FIG. Fig.19 shown.

[0163] Similarly, in this embodiment, when the speed of the high-speed motor is 60,000 rpm, the circular holes on the encoding turntable are coded and punched according to an 8-bit Golay complementary code sequence, the diameter of the circular hole is 1000μm, the spacing between the circular holes is 1000μm, the code group spacing is 20mm, and the distance between the center of the circular hole and the circumferential edge of the turntable is 2mm. The diameter of the encoding turntable is calculated by the above parameters to be 93.127mm, and the laser pulse duration is 3571.429ns.

[0164] The specific structure and implementation of other parts of this embodiment are the same as those of Embodiment 3 and will not be repeated here.

[0165] Example 6

[0166] See also Fig.18 As shown, this embodiment adopts a physical coded pulse laser conversion method, the laser source adopts a high repetition frequency pulse laser, and the pulse repetition frequency of the pulse laser is controlled by a frequency synchronization device to be an integral multiple of the pulse coding frequency of the coded pulse conversion device, so that the laser pulse generated by the pulse laser can just pass through the circular hole on the encoding turntable, and the transceiver telescope module of this embodiment is a transceiver separated telescope structure, that is, it includes an independently arranged transmitting telescope and receiving telescope. When the transceiver separated optical telescope structure is adopted, two optical fibers are required, one optical fiber connects the collimating coupler and the transmitting telescope, and the other optical fiber connects the receiving telescope and the filter.

[0167] Specifically, a water body laser radar based on coded pulses includes:

[0168] A green light band high repetition rate pulse laser 14, a focusing system 15, a two-way coded pulse conversion device 16, a frequency synchronization device 35, a first collimation coupler 17, a first transmitting telescope 29, a first receiving telescope 30, a first filter 20, a first detector 21, a second collimation coupler 22, a second transmitting telescope 31, a second receiving telescope 32, a second filter 25, a second detector 26, a multi-channel acquisition module 27, and a calculation module 28.

[0169] Among them, the green light band high repetition frequency pulse laser 34 generates a pulse laser in the green light band with a central wavelength of 532nm. The focusing system 15 is composed of a collimator and a focusing lens. After the green light band laser is collimated by the collimator, it is focused to a light spot of 10-50μm by the focusing lens, and converted into two coded pulse lasers by two 8-bit Golay complementary code sequence coded pulse conversion devices 16. The frequency synchronization device 35 controls the pulse repetition frequency of the green light band high repetition frequency pulse laser 34 to be an integer multiple of the pulse coding frequency of the coded pulse conversion device 16. The first spatial pulse laser is coupled into the optical fiber through the first collimator coupler 17, and the first collimator coupler 17 is connected to the first transmitting telescope 29 through the optical fiber. The first pulse laser is incident into the water body through the first transmitting telescope 29. The second spatial pulse laser is coupled into the optical fiber through the second collimator coupler 22, and the second collimator coupler 22 is connected to the second transmitting telescope 31 through the optical fiber. The second pulse laser is incident into the water body through the second transmitting telescope 31.

[0170] The echo signal generated by the interaction between the first outgoing laser and the water body is received by the first receiving telescope 30. The echo signal enters the first detector 21 after being filtered by the first filter 20. The echo signal generated by the interaction between the second outgoing laser and the water body is received by the second receiving telescope 32. The echo signal enters the second detector 26 after being filtered by the second filter 25. The first detector 21 and the second detector 26 are used to convert the echo light signal into an electrical signal. The two electrical signals enter the multi-channel acquisition module 27 and are collected by the multi-channel acquisition module 27. The collected digital signals are processed by the calculation module 28 and then inverted to obtain the water body and target detection information corresponding to the two echo signals.

[0171] See also Figure 4As shown, the two-channel coded pulse laser conversion device 16 in this example is composed of a high-speed motor 161, a coding turntable 162, a branch turntable 163 and a synchronous shaft 164. The blue-band high-power continuous laser 14 generates a blue-band high-power continuous laser, which is collimated by a collimator and focused to a light spot of 10-50 μm by a focusing lens. The laser beam focal spot passes through the circular holes arranged according to the code on the coding turntable 162 driven by the high-speed motor 161. The coding turntable 162 rotates one circle to generate two groups of coded pulse lasers, one group is transmitted through the branch turntable 163, and the other group is reflected by the branch turntable 163, thereby generating two channels of blue-band spatial pulse lasers suitable for water body detection.

[0172] Similarly, in this embodiment, when the speed of the high-speed motor is 60,000 rpm, the circular holes on the encoding turntable are coded and punched according to an 8-bit Golay complementary code sequence, the diameter of the circular hole is 1000μm, the spacing between the circular holes is 1000μm, the code group spacing is 20mm, and the distance between the center of the circular hole and the circumferential edge of the turntable is 2mm. The diameter of the encoding turntable is calculated by the above parameters to be 93.127mm, and the laser pulse duration is 3571.429ns.

[0173] The specific structure and implementation of other parts of this embodiment are the same as those of Embodiment 3 and will not be repeated here.

[0174] The coded pulse-based water laser radar technology and method provided by the embodiments of the present invention have the following beneficial effects:

[0175] (1) When a high-power continuous laser is used as the laser source, it can not only increase the average emission power of the pulsed laser, but also generate coding-related gain by encoding the laser pulses, remove background noise, and improve the system signal-to-noise ratio, thereby realizing long-distance and weak signal target detection of pulsed laser radar. As continuous laser devices are mature, there are more bands to choose from, and the applicability is wider, which can meet the detection needs of different water scenes.

[0176] (2) Compared with the single-pulse laser radar system, the single detection time is greatly reduced, which is very suitable for the detection of fast-moving underwater targets and rapidly changing water bodies.

[0177] (3) When using the physical coded pulse laser conversion method, the laser source can be a high-power continuous laser or a high-repetition-frequency pulse laser. The laser pulses are encoded by a physical coded pulse laser conversion device to generate two coded pulse lasers, which can simultaneously detect water bodies in two different directions and positions. Compared with the single-repetition pulse laser radar system, it can not only improve the system signal-to-noise ratio, but also increase the detection dimension and range, reduce the detection waiting time, and improve the detection efficiency.

[0178] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0179] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A water laser radar based on coded pulses, characterized in that: include: High-power lasers, coded pulse laser conversion devices, collimation couplers, transceiver telescope modules, filters, detectors, acquisition modules, and computing modules; The coded pulse laser conversion device converts the high-power laser generated by the high-power laser into a coded pulse laser, and the coded pulse laser is coupled into the optical fiber through the collimating coupler and then incident into the water body through the transmitting telescope in the transceiver telescope module; the echo signal generated by the interaction between the emitted laser and the water body is received by the receiving telescope in the transceiver telescope module, and the echo signal enters the detector after being filtered by the filter, and the detector converts the echo signal into an electrical signal; the electrical signal is collected by the acquisition module, and the collected digital signal is processed by the calculation module and then inverted to obtain water body and target detection information; The coded pulse laser conversion device converts the high-power laser into the coded pulse laser in a physical manner; the coded pulse laser conversion device comprises two coded pulse laser conversion devices (16); The two-path coded pulse laser conversion device (16) comprises a high-speed motor (161), a coding turntable (162), a branching turntable (163), and a synchronous rotating shaft (164); the coding turntable (162) is punched with holes on a disk according to two groups of identical Golay complementary code sequences, each with four code groups arranged alternately; the branching turntable (163) alternately transmits and reflects the coded pulse laser according to the arched areas corresponding to the eight code group circular holes (1621) of the coding turntable (162); the high-speed motor (161) fixes the coding turntable (162) via the synchronous rotating shaft (164) and a fixture; the synchronous rotating shaft (164) connects the high-speed motor (161), the coding turntable (162), and the branching turntable (163); 63), a high-speed motor (161) drives the encoding disk (162) and the branching disk (163) to rotate synchronously through a synchronous rotating shaft (164), the encoding disk (162) is perpendicular to the synchronous rotating shaft (164), and the branching disk (163) forms an angle of 45 degrees with the synchronous rotating shaft (164), so that the projections of the eight sectors corresponding to the encoding disk (162) and the branching disk (163) in the horizontal direction always remain overlapped when they rotate; the branching disk (163) divides the encoding pulse laser generated by the encoding disk (162) into two paths through a hollow area and a reflection area, the hollow area transmits the first group of encoding pulse lasers to generate a first path of encoding pulse lasers, and the reflection area reflects the second group of encoding pulse lasers to generate a second path of encoding pulse lasers.

2. The coded pulse water laser radar according to claim 1, characterized in that: The high-power laser is a blue-green band high-power continuous laser (14); the collimating coupler comprises a first collimating coupler (17) and a second collimating coupler (22); the transceiver telescope module comprises a first transceiver telescope module and a second transceiver telescope module; the filter comprises a first filter (20) and a second filter (25); the detector comprises a first detector (21) and a second detector (26); the acquisition module is a multi-channel acquisition module (27); the water laser radar also comprises a focusing system (15); The blue-green band high-power continuous laser light generated by the blue-green band high-power continuous laser (14) is focused by the focusing system (15) to generate a focused light beam, which is converted into two-path coded pulse laser light by a two-path coded pulse laser conversion device (16), namely a first-path spatial pulse laser light and a second-path spatial pulse laser light; A first spatial pulse laser is coupled into an optical fiber via a first collimating coupler (17), and is incident into the water body via a transmitting telescope in a first transceiver telescope module; The second spatial pulse laser is coupled into the optical fiber via the second collimating coupler (22), and is incident into the water body via the transmitting telescope in the second transceiver telescope module; A first echo signal generated by the interaction between the first laser and the water body is received by a receiving telescope in the first transceiver telescope module, and a second echo signal generated by the interaction between the second laser and the water body is received by a receiving telescope in the second transceiver telescope module; the first echo signal is filtered by a first filter (20) and then enters a first detector (21), and the second echo signal is filtered by a second filter (25) and then enters a second detector (26); the first detector (21) is used to convert the first echo signal into a first electrical signal, and the second detector (26) is used to convert the second echo signal into a second electrical signal; the multi-channel acquisition module (27) acquires the first electrical signal and the second electrical signal and processes them through a calculation module and then inverts them to obtain water body and target detection information.

3. The coded pulse water laser radar according to claim 1, characterized in that: The high-power laser is a blue-green band high repetition frequency pulse laser (34); the collimating coupler comprises a first collimating coupler (17) and a second collimating coupler (22); the transceiver telescope module comprises a first transceiver telescope module and a second transceiver telescope module; the filter comprises a first filter (20) and a second filter (25); the detector comprises a first detector (21) and a second detector (26); the acquisition module is a multi-channel acquisition module (27); the water body laser radar further comprises a focusing system (15); the water body laser radar further comprises a frequency synchronization device (35); The blue-green band high repetition frequency pulse laser generated by the blue-green band high repetition frequency pulse laser (34) is focused by the focusing system (15) to generate a focused light beam, which is converted into two-path coded pulse lasers, namely a first-path spatial pulse laser and a second-path spatial pulse laser, by a two-path coded pulse laser conversion device (16); the frequency synchronization device (35) controls the pulse repetition frequency of the blue-green band high repetition frequency pulse laser (34) to be an integer multiple of the pulse coding frequency of the coded pulse laser conversion device (16); A first spatial pulse laser is coupled into an optical fiber via a first collimating coupler (17), and is incident into the water body via a transmitting telescope in a first transceiver telescope module; The second spatial pulse laser is coupled into the optical fiber via the second collimating coupler (22), and is incident into the water body via the transmitting telescope in the second transceiver telescope module; A first echo signal generated by the interaction between the first laser and the water body is received by a receiving telescope in the first transceiver telescope module, and a second echo signal generated by the interaction between the second laser and the water body is received by a receiving telescope in the second transceiver telescope module; the first echo signal is filtered by a first filter (20) and then enters a first detector (21), and the second echo signal is filtered by a second filter (25) and then enters a second detector (26); the first detector (21) is used to convert the first echo signal into a first electrical signal, and the second detector (26) is used to convert the second echo signal into a second electrical signal; the multi-channel acquisition module (27) acquires the first electrical signal and the second electrical signal and processes them through a calculation module and then inverts them to obtain water body and target detection information.

4. The coded pulse water laser radar according to claim 1, characterized in that: The formula for obtaining the diameter dt of the encoding disc (162) is as follows: dt={[N*dr+(N-1)d] / 1000+dc}*8 / π+2*dw The formula for obtaining the laser pulse duration pt of the encoding disk (162) is as follows: pt=1 / Rd / 60 / {[N*dr+(N-1)d] / (1000+dc)*8}*1000*dr / 1000000000 Among them, Rd represents the rotation speed; N represents the Golay code group length; dr represents the diameter of the circular hole; d represents the circular hole spacing; dc represents the code group spacing; dw represents the distance between the center of the circular hole and the edge of the turntable.

5. The coded pulse water laser radar according to claim 2 or 3, characterized in that: The focusing system (15) comprises a collimating lens and a focusing lens, and the focusing spot diameter is 10-50 μm.

6. A method for generating coded pulse laser, characterized in that: include: The blue-green band high-power continuous laser generated by the blue-green band high-power continuous laser is focused by a focusing system to generate a focused beam, which is converted into a two-channel coded pulse laser by a two-channel coded pulse laser conversion device; Specifically, the two-path coded pulse laser conversion device includes a high-speed motor, a coding turntable, a branch turntable, and a synchronous shaft; the coding turntable is punched on a disc according to two groups of identical Golay complementary code sequences, each with 4 code groups arranged alternately; the branch turntable alternately transmits and reflects the coded pulse laser according to the arched areas corresponding to the 8 code group holes of the coding turntable; the synchronous shaft connects the high-speed motor, the coding turntable and the branch turntable, and the high-speed motor drives the coding turntable and the branch turntable to rotate synchronously through the synchronous shaft, the coding turntable is perpendicular to the synchronous shaft, and the branch turntable forms an angle of 45 degrees with the synchronous shaft, so that the projections of the 8 sectors corresponding to the coding turntable and the branch turntable in the horizontal direction always remain overlapping when they rotate.

7. A method for generating coded pulse laser, characterized in that: include: The blue-green band high repetition frequency pulse laser generated by the blue-green band high repetition frequency pulse laser is focused by a focusing system to generate a focused beam, which is converted into a two-way coded pulse laser by a two-way coded pulse laser conversion device. The frequency synchronization device controls the pulse repetition frequency of the blue-green band high repetition frequency pulse laser to be an integral multiple of the pulse coding frequency of the two-way coded pulse conversion device. Specifically, the two-path coded pulse laser conversion device includes a high-speed motor, a coding turntable, a branch turntable, and a synchronous shaft; the coding turntable is punched on a disc according to two groups of identical Golay complementary code sequences, each with 4 code groups arranged alternately; the branch turntable alternately transmits and reflects the coded pulse laser according to the arched areas corresponding to the 8 code group holes of the coding turntable; the synchronous shaft connects the high-speed motor, the coding turntable and the branch turntable, and the high-speed motor drives the coding turntable and the branch turntable to rotate synchronously through the synchronous shaft, the coding turntable is perpendicular to the synchronous shaft, and the branch turntable forms an angle of 45 degrees with the synchronous shaft, so that the projections of the 8 sectors corresponding to the coding turntable and the branch turntable in the horizontal direction always remain overlapping when they rotate.

Images