Long-distance follow-up laser seeker and control method

Abstract

The present invention discloses a long-distance follow-up laser guidance head and control method. The guidance head of the present invention adopts a large-aperture transmission optical system, which reduces the cost while enhancing the received laser energy. In combination with the laser detection signal directly sampled by the signal conditioning circuit adopted in the back end, the sensitivity of the entire detection system is doubled, and the detection stability and anti-interference ability are also greatly improved, and finally a long-distance detection distance of not less than 10 km is achieved, while the cost is reduced by 2 to 3 times. Due to the application of a four-quadrant laser PIN detector, a large field of view detection of not less than ±15° is also achieved, which greatly reduces the technical threshold of terminal guidance flight control.

Description

Technical Field

[0001] The invention belongs to the field of laser guidance, and in particular relates to a long-distance follow-up laser seeker and a control method. Background Art

[0002] A laser seeker is a terminal guidance device installed on an aircraft. It performs photoelectric conversion, signal conditioning, and digital signal processing on the laser echo signal diffusely reflected by the target, then controls the optical axis to lock and track the target while sending out the missile-target line-of-sight angular rate signal for aircraft navigation. At present, most of the laser seekers equipped in the world use four-quadrant laser detectors, which are mainly divided into four-quadrant PIN laser detectors and four-quadrant APD laser detectors.

[0003] Due to the poor sensitivity of the four-quadrant PIN laser detector, even with a 100mJ airborne laser illuminator, the maximum range of the laser seeker can reach 4 to 5km, which seriously limits the scope of use. The four-quadrant laser APD detector is generally used in long-distance laser seekers with a range of more than 5km due to its high detection sensitivity, but the shortcomings of the four-quadrant APD laser detector are also obvious. First, the yield rate is low and the price is expensive. Only a few developed countries can master mass production. Secondly, the photosensitive surface of the four-quadrant APD laser detector is too small, resulting in the field of view of the applied laser seeker being no more than ±3°, which seriously affects the search efficiency and tracking stability of the laser seeker. Finally, the four-quadrant APD laser detector is technically difficult to use, the detection sensitivity is greatly affected by changes in ambient temperature, and the seeker has a large blind area.

[0004] The current laser seeker laser detection signal processing circuit is mainly designed with a peak hold circuit as the core solution. It uses the sum of four-quadrant signals to trigger the peak hold circuit and simultaneously trigger the DSP interrupt to control the low-speed ADC to complete the analog-to-digital conversion of the laser pulse peak hold signal. Since the peak hold circuit is built with discrete components, it has the disadvantages of weak anti-noise ability, poor linearity and stability of peak hold for large and small signals. Moreover, the laser echo signal loses the characteristics of the original signal after passing through the peak hold circuit, and cannot be processed by digital signals, and is easily induced by interference. Summary of the invention

[0005] The purpose of the present invention is to overcome the above shortcomings and provide a long-distance follow-up laser seeker and control method, which adopts a design scheme of a large aspherical lens optical system, a four-quadrant PIN laser detector and a high-speed ADC direct sampling, so that the laser semi-active seeker has a large field of view of ±15° without increasing the irradiation energy of the laser irradiator, and the detection and tracking distance reaches more than 10km. The design difficulty of the entire aircraft terminal guidance system is greatly reduced, the cost is reasonable, and it is easy to mass produce.

[0006] In order to achieve the above-mentioned purpose, a long-distance follow-up laser guidance head includes a transmission optical system with a four-quadrant laser PIN detector, an optical fairing is arranged outside the transmission optical system, the four-quadrant laser PIN detector in the transmission optical system is connected to a signal conditioning circuit, the transmission optical system is arranged on a dual-axis servo system, the signal conditioning circuit is connected to an FPGA preprocessing circuit, the FPGA preprocessing circuit is connected to a DSP main control circuit, and the DSP main control circuit is connected to the dual-axis servo system;

[0007] The transmission optical system collects the received laser echo signal into an image and performs photoelectric conversion, and then sends it to the signal conditioning circuit;

[0008] The signal conditioning circuit is used to perform automatic gain control and analog-to-digital conversion, and output the digital quantity of the four-quadrant laser echo signal to enter the FPGA preprocessing circuit;

[0009] The FPGA preprocessing circuit performs initial signal inspection and preprocessing and sends it to the DSP main control circuit;

[0010] The DSP main control circuit is used to confirm and identify the target, perform sum and difference calculations, and gain control. At the same time, it uses a proportional guidance algorithm to control the dual-axis servo system to track and point to the target.

[0011] The dual-axis servo system is used to drive the transmission optical system to rotate and realize the target searching and tracking functions.

[0012] The transmission optical system includes a filter, an aspheric lens, a spherical lens and a four-quadrant PIN laser detector. The four-quadrant PIN laser detector is connected to a signal conditioning circuit. A spherical lens is arranged in front of the receiving end of the four-quadrant PIN laser detector, an aspheric lens is arranged in front of the spherical lens, and a filter is arranged in front of the aspheric lens.

[0013] The signal conditioning circuit includes a transimpedance amplifier circuit, a programmable amplifier circuit, and a sampling circuit. The transimpedance amplifier circuit and the programmable amplifier circuit respectively contain four completely identical circuit channels. The four channel input ends of the transimpedance amplifier circuit are respectively connected to the four-quadrant output ends A, B, C, and D of the four-quadrant PIN laser detector. The outputs of the four channels of the transimpedance amplifier circuit are respectively connected to the input ends of the four channels of the programmable amplifier circuit. The output ends of the four channels of the programmable amplifier circuit are respectively connected to the sampling circuit.

[0014] The FPGA preprocessing circuit includes a buffer receiving module, a low-pass filtering module, a laser pulse signal initial detection module, a preliminary detection signal parallel sending module, and a wave gate module. The signal conditioning circuit is connected to the buffer receiving module and the wave gate module. The buffer receiving module is connected to the low-pass filtering module. The low-pass filtering module is connected to the laser pulse signal initial detection module. The laser pulse signal initial detection module is connected to the preliminary detection signal parallel sending module. The preliminary detection signal parallel sending module and the wave gate module are both connected to the DSP main control circuit.

[0015] The buffer receiving module is used for buffering and receiving the four-quadrant laser echo signal;

[0016] The low-pass filter module is used to perform low-pass filtering on the four-quadrant laser echo signal;

[0017] The laser pulse signal initial detection module is used to sum the signals processed by low-pass filtering and identify the laser pulse signal;

[0018] The initial detection signal parallel sending module is used to send the original digital quantity of the laser pulse signal identified by the signal initial detection module to the DSP main control circuit;

[0019] The gate module is used to control the sampling time of the enabled high-speed ADC with a width of 2us.

[0020] The DSP main control circuit includes a DMA parallel receiving module, a signal lock solving module, a proportional guidance solving and control module, an automatic gain control module and an external communication module. The DMA parallel receiving module is connected to the FPGA preprocessing circuit and the signal lock solving module. The signal lock solving module is connected to the proportional guidance solving and control module and the automatic gain control module. The proportional guidance solving and control module is connected to the external communication module. The automatic gain control module is connected to the signal conditioning circuit and the FPGA preprocessing circuit.

[0021] The DMA parallel receiving module is used to receive the laser pulse signal that has been initially detected by the FPGA preprocessing circuit;

[0022] The signal lock calculation module is used to identify whether the laser pulse signal initially detected by the FPGA preprocessing circuit is indeed the target reflected laser echo signal, send the target reflected laser echo signal to the proportional guidance calculation and control module, and control the FPGA preprocessing circuit to open the wave gate module;

[0023] The proportional guidance solution and control module is used to calculate the difference between the target reflected laser echo signal and the missile-target line of sight angle error, and convert it into a missile-target line of sight angle rate signal through the proportional guidance algorithm and send it to the dual-axis servo system;

[0024] The automatic gain control module controls the laser pulse signal and voltage amplitude to be stable at 1.8V through the gain change of the large dynamic range programmable amplifier circuit, ensuring that the sampling circuit sampling data is stable and reliable;

[0025] The external communication module is used to send the missile-target line-of-sight angular rate signal and laser seeker status information and receive host computer instructions.

[0026] Dual-axis servo system with a tracking range of ±40° in pitch and ±30° in heading.

[0027] A control method for a long-distance follow-up laser seeker comprises the following steps:

[0028] Step 1: The target diffusely reflected laser echo signal enters the four-quadrant laser PIN detector of the transmission optical system through the optical fairing;

[0029] Step 2: The transmission optical system gathers the laser echo signal into an image, performs photoelectric conversion and then sends it to the signal conditioning circuit;

[0030] Step 3: The signal conditioning circuit performs automatic gain control and analog-to-digital conversion on the received signal, and outputs the digital quantity of the four-quadrant laser echo signal to the FPGA preprocessing circuit;

[0031] Step 4: The FPGA preprocessing circuit performs preliminary inspection and preprocessing on the digital quantity of the four-quadrant laser echo signal and sends it to the DSP main control circuit;

[0032] Step 5: The DSP main control circuit confirms the target identification, sum and difference calculation, and gain control, and uses the proportional guidance algorithm to control the dual-axis servo system to track and point to the target.

[0033] The signal conditioning circuit is composed of a transimpedance amplifier circuit, a program-controlled amplifier circuit, and a sampling circuit;

[0034] First, the signal received by the transimpedance amplifier circuit is converted into a voltage pulse signal, and the gain is adjusted through the programmable amplifier circuit. The digital quantity of the four-quadrant laser echo signal is collected by the sampling circuit and sent to the FPGA preprocessing circuit.

[0035] The FPGA preprocessing circuit includes a buffer receiving module, a low-pass filtering module, a laser pulse signal initial detection module, a preliminary detection signal parallel sending module and a wave gate module;

[0036] The four-quadrant laser echo signal digital quantity is received through the buffer receiving module, and the received four-quadrant laser echo signal digital quantity is low-pass filtered through the low-pass filtering module. The laser pulse signal preliminary inspection module sums the signal processed by the low-pass filtering and identifies the laser pulse signal. The laser pulse signal is sent to the DSP main control circuit through the preliminary inspection signal parallel sending module, and the gate module controls the enabling high-speed ADC sampling time with a width of 2us.

[0037] The DSP main control circuit includes a DMA parallel receiving module, a signal locking solution module, a proportional guidance solution and control module, an automatic gain control module, and an external communication module;

[0038] The digital quantity of the laser pulse signal preprocessed by the FPGA preprocessing circuit is received through the DMA parallel receiving module. The signal locking solution module uses the coherent detection algorithm to extract the target reflected laser echo signal from the laser pulse signal preliminarily inspected by the FPGA preprocessing circuit. The proportional guidance solution and control module performs sum and difference operations on the target reflected laser echo signal to obtain the missile-target line of sight angle error, which is converted into a missile-target line of sight angle rate signal through the proportional guidance algorithm for the dual-axis servo system. The automatic gain control module controls the gain change of the signal conditioning circuit.

[0039] Compared with the prior art, the guidance head of the present invention adopts a large-aperture transmission optical system, which reduces the cost while enhancing the received laser energy. Combined with the laser detection signal directly sampled by the signal conditioning circuit adopted in the back end, the sensitivity of the entire detection system is doubled, and the detection stability and anti-interference ability are also greatly improved, and finally a long-distance detection distance of not less than 10 km is achieved, while the cost is reduced by 2 to 3 times. Due to the application of a four-quadrant laser PIN detector, a large field of view detection of not less than ±15° is also achieved, which greatly reduces the technical threshold of terminal guidance flight control.

[0040] The method of the present invention allows the diffusely reflected laser echo signal of the target to enter the laser guidance head through the optical fairing, and after the transmission optical system converges the image and photoelectric conversion, it is sent to the signal conditioning circuit for automatic gain control and analog-to-digital conversion. The digital quantity of the four-quadrant laser echo signal output by the signal conditioning circuit is firstly pre-processed by the FPGA pre-processing circuit to complete the signal initial inspection and pre-processing, and then confirmed by the DSP main control circuit (to identify the target, perform sum and difference operations, and calculate proportional guidance, and then control the dual-axis servo system to track and point to the target. At the same time, the navigation information is sent to the flight control computer on the missile. The present invention enables the laser semi-active guidance head to have a large field of view of ±15° without increasing the irradiation energy of the laser irradiator, and the detection and tracking distance reaches more than 10km. The design difficulty of the entire aircraft terminal guidance system is greatly reduced, and the cost is reasonable, and it is easy to mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram of the structure of my invention;

[0042] Figure 2 is a structural diagram of the transmission optical system of the present invention;

[0043] Figure 3 is a system diagram of the signal conditioning circuit in the present invention;

[0044] Figure 4 It is a connection diagram of the signal conditioning circuit, FPGA preprocessing circuit and DSP main control circuit in the present invention;

[0045] Among them, 1. optical fairing; 2. transmissive optical system; 3. dual-axis servo system; 4. signal conditioning circuit; 5. FPGA preprocessing circuit; 6. DSP main control circuit; 201. filter; 202. aspheric lens; 203. spherical lens; 204. four-quadrant PIN laser detector; 401. transimpedance amplifier circuit; 402. programmable amplifier circuit; 403. sampling circuit; 501. buffer receiving module; 502. low-pass filter module; 503. laser pulse signal initial detection module; 504. initial detection signal parallel sending module; 505. wave gate module; 601. DMA parallel receiving module; 602. signal lock solution module; 603. proportional guidance solution and control module; 604. automatic gain control module; 605. external communication module. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the accompanying drawings.

[0047] See also Figure 1 A long-distance follow-up laser guidance head includes a transmissive optical system 2, an optical fairing 1 is arranged outside the transmissive optical system 2, the transmissive optical system 2 is connected to a dual-axis servo system 3 and a signal conditioning circuit 4, the signal conditioning circuit 4 is connected to an FPGA preprocessing circuit 5, the FPGA preprocessing circuit 5 is connected to a DSP main control circuit 6, and the DSP main control circuit 6 is connected to the dual-axis servo system 3;

[0048] The transmission optical system 2 collects and images the received laser echo signal and performs photoelectric conversion, and then sends it to the signal conditioning circuit 4;

[0049] The signal conditioning circuit 4 is used to perform automatic gain control and analog-to-digital conversion, and output the digital quantity of the four-quadrant laser echo signal to enter the FPGA preprocessing circuit 5;

[0050] The FPGA preprocessing circuit 5 performs initial signal detection and preprocessing and sends it to the DSP main control circuit 6;

[0051] The DSP main control circuit 6 is used to confirm the target identification, calculate the sum and difference of the wing proportional guidance, and then control the operation of the dual-axis servo system 3;

[0052] The dual-axis servo system 3 is used to drive the transmissive optical system 2 to rotate.

[0053] A control method for a long-distance follow-up laser seeker comprises the following steps:

[0054] Step 1: The target diffusely reflected laser echo signal enters the four-quadrant laser PIN detector of the transmission optical system 2 through the optical fairing 1;

[0055] Step 2: The transmission optical system 2 gathers the laser echo signal into an image, performs photoelectric conversion and then sends it to the signal conditioning circuit 4;

[0056] Step 3, the signal conditioning circuit 4 performs automatic gain control and analog-to-digital conversion on the received signal, and outputs the digital quantity of the four-quadrant laser echo signal to the FPGA preprocessing circuit 5;

[0057] Step 4, the FPGA pre-processing circuit 5 performs preliminary inspection and pre-processing on the digital quantity of the four-quadrant laser echo signal, and sends it to the DSP main control circuit 6;

[0058] Step 5: After the DSP main control circuit 6 confirms the target identification, performs sum and difference operations and proportional guidance calculations, it controls the dual-axis servo system 3 to track and point to the target.

[0059] See also Figure 2 The transmission optical system 2 includes a four-quadrant PIN laser detector 204, which is connected to a signal conditioning circuit. A spherical lens 203 is arranged in front of the receiving end of the four-quadrant PIN laser detector 204, an aspherical lens 202 is arranged in front of the spherical lens 203, and a filter 201 is arranged in front of the aspherical lens 202.

[0060] The lens barrel of the transmission optical system 2 is made of aluminum alloy material. After hard anodizing treatment, a spherical lens 203, an aspherical lens 202, a narrow-band filter 201, and a four-quadrant PIN laser detector 204 are installed from the inside to the outside. Finally, the lens barrel is installed on the optical stand of the dual-axis servo system 3.

[0061] See also Figure 3 The signal conditioning circuit 4 includes a transimpedance amplifier circuit 401, a large dynamic range programmable amplifier circuit 402 and a sampling circuit 403. The four channel input ends of the transimpedance amplifier circuit 401 are respectively connected to the four-quadrant output ends A, B, C, and D of the four-quadrant PIN laser detector 204, the outputs of the four channels of the transimpedance amplifier circuit 401 are respectively connected to the input ends of the four channels of the programmable amplifier circuit 402, and the outputs of the four channels of the programmable amplifier circuit 402 are respectively connected to the sampling circuit 403.

[0062] The transimpedance amplifier circuit 401 consists of 4 channels, mainly composed of 4 completely identical and parallel transimpedance amplifier circuits. The programmable amplifier circuit 402 consists of 4 completely identical and parallel programmable amplifier circuits with a large dynamic range. The programmable amplifier circuit 402 controls the gain of the automatic gain control module 604 through the SPI interface. The sampling circuit 403 is mainly composed of a four-channel high-speed ADC chip with a sampling rate of 250MIPS and an accuracy of 14 bits and a 250MHz high-precision temperature compensated crystal oscillator.

[0063] First, the signal received by the transimpedance amplifier circuit 401 is converted into a voltage pulse signal, and the gain is adjusted by the programmable amplifier circuit 402, and the digital quantity of the four-quadrant laser echo signal is collected by the sampling circuit 403 and sent to the FPGA preprocessing circuit 5.

[0064] See also Figure 4 , the FPGA preprocessing circuit 5 includes a buffer receiving module 501, a low-pass filtering module 502, a laser pulse signal initial detection module 503, a preliminary detection signal parallel sending module 504, and a wave gate module 505. The signal conditioning circuit 4 is connected to the buffer receiving module 501 and the wave gate module 505. The buffer receiving module 501 is connected to the low-pass filtering module 502, the low-pass filtering module 502 is connected to the laser pulse signal initial detection module 503, the laser pulse signal initial detection module 503 is connected to the preliminary detection signal parallel sending module 504, and the preliminary detection signal parallel sending module 504 and the wave gate module 505 are both connected to the DSP main control circuit 6;

[0065] The buffer receiving module 501 is used for buffering and receiving the four-quadrant laser echo signal;

[0066] The low-pass filter module 502 is used to perform low-pass filtering on the four-quadrant laser echo signal;

[0067] The laser pulse signal initial detection module 503 is used to sum the signals processed by low-pass filtering and identify the laser pulse signal;

[0068] The initial detection signal parallel sending module 504 is used to send the original digital quantity of the laser pulse signal identified by the laser pulse signal initial detection module 503 to the DSP main control circuit 6; the initial detection signal parallel sending module 504 uses a parallel channel for transmission, with a transmission speed of 50MHz and a bit width of 16Bit.

[0069] The gate module 505 is used to control the enabling high-speed ADC sampling time with a width of 2us. After the laser seeker locks the target laser echo, the time when the next laser signal arrives is calculated according to the laser code, and the high-speed ADC sampling is turned on 1us in advance and turned off 2us later, thereby reducing power consumption and increasing the anti-interference ability of the laser seeker.

[0070] The four-quadrant laser echo signal digital quantity is received by the buffer receiving module 501, and the received four-quadrant laser echo signal digital quantity is low-pass filtered by the low-pass filtering module 502. The laser pulse signal preliminary detection module 503 sums the signal processed by the low-pass filtering and identifies the laser pulse signal. The laser pulse signal is sent to the DSP main control circuit 6 through the preliminary detection signal parallel sending module 504, and the enabling high-speed ADC sampling time with a width of 2us is controlled by the wave gate module 505.

[0071] See also Figure 4, the DSP main control circuit 6 includes a DMA parallel receiving module 601, a signal lock solving module 602, a proportional guidance solving and control module 603, an automatic gain control module 604 and an external communication module 605, the DMA parallel receiving module 601 is connected to the FPGA preprocessing circuit 5 and the signal lock solving module 602, the signal lock solving module 602 is connected to the proportional guidance solving and control module 603 and the automatic gain control module 604, the proportional guidance solving and control module 603 is connected to the external communication module 605, and the automatic gain control module 604 is connected to the signal conditioning circuit 4 and the FPGA preprocessing circuit 5;

[0072] The DMA parallel receiving module 601 is used to receive the laser pulse signal preliminarily detected by the FPGA preprocessing circuit 5;

[0073] The signal lock calculation module 602 is used to identify whether the laser pulse signal initially detected by the FPGA preprocessing circuit 5 is indeed the target reflected laser echo signal, send the target reflected laser echo signal to the proportional guidance calculation and control module 603, and control the FPGA preprocessing circuit 5 to open the wave gate module 505 to enhance the anti-interference ability;

[0074] The proportional guidance solution and control module 603 is used to calculate the difference between the target reflected laser echo signal and the missile-target line of sight angle error, convert it into a missile-target line of sight angle rate signal through a proportional guidance algorithm and send it to the dual-axis servo system 3;

[0075] The automatic gain control module 604 controls the laser pulse signal and the voltage amplitude to be stable at 1.8V by adjusting the gain change of the large dynamic range programmable amplifier circuit, ensuring that the sampling data of the sampling circuit 403 is stable and reliable;

[0076] The external communication module 605 is used to send the missile-target line of sight angular rate signal and the laser seeker status information and receive the host computer command. The external communication module (605) is a CAN communication interface. The DSP main control circuit (6) sends the missile-target line of sight angular rate signal and the laser seeker status information and receives the host computer command through the external communication module (605). The CAN interface communication rate is 500KHz.

[0077] The laser pulse signal passing through the FPGA preprocessing circuit 5 is received through the DMA parallel receiving module 601, and the signal locking solution module 602 uses the coherent detection algorithm to extract the target reflected laser echo signal from the laser pulse signal initially detected by the FPGA preprocessing circuit 5. The proportional guidance solution and control module 603 performs sum and difference operations on the target reflected laser echo signal to obtain the missile-target line of sight angle error, and converts it into a missile-target line of sight angular rate signal through the proportional guidance algorithm for the dual-axis servo system 3. The automatic gain control module 604 controls the gain change of the signal conditioning circuit 4.

[0078] The dual-axis servo system 6 has a tracking range of ±40° in pitch and ±30° in heading.

Claims

1. A long-distance follow-up laser seeker, characterized in that: The invention comprises a transmissive optical system (2) having a four-quadrant laser PIN detector, an optical fairing (1) being arranged in front of the transmissive optical system (2), the four-quadrant laser PIN detector in the transmissive optical system (2) being connected to a signal conditioning circuit (4), the transmissive optical system (2) being arranged on a dual-axis servo system (3), the signal conditioning circuit (4) being connected to an FPGA preprocessing circuit (5), the FPGA preprocessing circuit (5) being connected to a DSP main control circuit (6), and the DSP main control circuit (6) being connected to the dual-axis servo system (3); The transmission optical system (2) collects and images the received laser echo signal and performs photoelectric conversion, and then sends the signal to the signal conditioning circuit (4); The signal conditioning circuit (4) is used to perform automatic gain control and analog-to-digital conversion, and output the digital quantity of the four-quadrant laser echo signal to enter the FPGA preprocessing circuit (5); The FPGA pre-processing circuit (5) performs preliminary signal detection and pre-processing and sends the signal to the DSP main control circuit (6); The DSP main control circuit (6) is used to confirm and identify the target, perform sum and difference calculations, and perform gain control, and at the same time, use a proportional guidance algorithm to control the dual-axis servo system (3) to track and point to the target; The dual-axis servo system (3) is used to drive the transmissive optical system (2) to rotate; The transmission optical system (2) comprises a filter (201), an aspheric lens (202), a spherical lens (203) and a four-quadrant PIN laser detector (204); the four-quadrant PIN laser detector (204) is connected to a signal conditioning circuit; a spherical lens (203) is arranged in front of a receiving end of the four-quadrant PIN laser detector (204); a aspheric lens (202) is arranged in front of the spherical lens (203); and a filter (201) is arranged in front of the aspheric lens (202); The DSP main control circuit (6) comprises a DMA parallel receiving module (601), a signal lock solving module (602), a proportional guidance solving and control module (603), an automatic gain control module (604) and an external communication module (605); the DMA parallel receiving module (601) is connected to the FPGA preprocessing circuit (5) and the signal lock solving module (602); the signal lock solving module (602) is connected to the proportional guidance solving and control module (603) and the automatic gain control module (604); the proportional guidance solving and control module (603) is connected to the external communication module (605); and the automatic gain control module (604) is connected to the signal conditioning circuit (4) and the FPGA preprocessing circuit (5); The DMA parallel receiving module (601) is used to receive the laser pulse signal preliminarily detected by the FPGA preprocessing circuit (5); The signal lock calculation module (602) is used to identify whether the laser pulse signal initially detected by the FPGA pre-processing circuit (5) is indeed a target reflected laser echo signal, send the target reflected laser echo signal to the proportional guidance calculation and control module (603), and control the FPGA pre-processing circuit (5) to open the wave gate module (505); The proportional guidance solution and control module (603) is used to calculate the difference between the target reflected laser echo signal and the missile-target line of sight angle error, convert it into a missile-target line of sight angle rate signal through a proportional guidance algorithm and send it to the dual-axis servo system (3); An automatic gain control module (604) controls the gain change of the programmable amplifier circuit (402); The external communication module (605) is used to send missile-target line-of-sight angular rate signals and laser seeker status information and receive host computer instructions.

2. A long-distance follow-up laser seeker according to claim 1, characterized in that: The signal conditioning circuit (4) comprises a transimpedance amplifier circuit (401), a programmable amplifier circuit (402), and a sampling circuit (403). The transimpedance amplifier circuit (401) and the programmable amplifier circuit (402) respectively comprise four identical circuit channels. The four channel input ends of the transimpedance amplifier circuit (401) are respectively connected to the four-quadrant output ends A, B, C, and D of the four-quadrant PIN laser detector (204). The output ends of the four channels of the transimpedance amplifier circuit (401) are respectively connected to the input ends of the four channels of the programmable amplifier circuit (402). The output ends of the four channels of the programmable amplifier circuit (402) are respectively connected to the sampling circuit (403).

3. A long-distance follow-up laser seeker according to claim 1, characterized in that: The FPGA preprocessing circuit (5) comprises a buffer receiving module (501), a low-pass filtering module (502), a laser pulse signal initial detection module (503), an initial detection signal parallel transmission module (504), and a gate module (505); the signal conditioning circuit (4) is connected to the buffer receiving module (501) and the gate module (505); the buffer receiving module (501) is connected to the low-pass filtering module (502); the low-pass filtering module (502) is connected to the laser pulse signal initial detection module (503); the laser pulse signal initial detection module (503) is connected to the initial detection signal parallel transmission module (504); and the initial detection signal parallel transmission module (504) and the gate module (505) are both connected to the DSP main control circuit (6); The buffer receiving module (501) is used for buffering and receiving four-quadrant laser echo signals; The low-pass filtering module (502) is used to perform low-pass filtering on the four-quadrant laser echo signal; The laser pulse signal initial detection module (503) is used to sum the signals processed by low-pass filtering and identify the laser pulse signal; The initial detection signal parallel sending module (504) is used to send the original digital quantity of the laser pulse signal identified by the laser pulse signal initial detection module (503) to the DSP main control circuit (6); The gate module (505) is used to control the enabling high-speed ADC sampling time with a width of 2us.

4. A long-distance follow-up laser seeker according to claim 1, characterized in that: The dual-axis servo system (3) has a tracking range of ±40° in pitch and ±30° in heading.

5. The control method of a long-distance follow-up laser seeker according to claim 1, characterized in that: The following steps are involved: Step 1: The target diffusely reflected laser echo signal enters the four-quadrant laser PIN detector of the transmission optical system (2) through the optical fairing (1); Step 2: The transmission optical system (2) gathers the laser echo signal into an image, performs photoelectric conversion, and then sends it to the signal conditioning circuit (4); Step 3: the signal conditioning circuit (4) performs automatic gain control and analog-to-digital conversion on the received signal, and outputs the digital quantity of the four-quadrant laser echo signal to the FPGA preprocessing circuit (5); Step 4, the FPGA pre-processing circuit (5) performs preliminary inspection and pre-processing on the digital quantity of the four-quadrant laser echo signal and sends it to the DSP main control circuit (6); Step 5: The DSP main control circuit (6) confirms the target identification, performs sum and difference calculations and proportional guidance calculations, and then controls the dual-axis servo system (3) to track and point to the target.

6. The control method of a long-distance follow-up laser seeker as claimed in claim 5, characterized in that: The signal conditioning circuit (4) is composed of a transimpedance amplifier circuit (401), a programmable amplifier circuit (402), and a sampling circuit (403); First, the signal received by the transimpedance amplifier circuit (401) is converted into a voltage pulse signal, and the gain is adjusted by the programmable amplifier circuit (402). The digital quantity of the four-quadrant laser echo signal is collected by the sampling circuit (403) and sent to the FPGA pre-processing circuit (5).

7. The control method of a long-distance follow-up laser seeker as claimed in claim 5, characterized in that: The FPGA pre-processing circuit (5) comprises a buffer receiving module (501), a low-pass filtering module (502), a laser pulse signal initial detection module (503), an initial detection signal parallel sending module (504) and a wave gate module (505); The digital quantity of the four-quadrant laser echo signal is received through a buffer receiving module (501), the received digital quantity of the four-quadrant laser echo signal is low-pass filtered through a low-pass filtering module (502), the signal processed by the low-pass filtering is summed through a laser pulse signal preliminary detection module (503), and the laser pulse signal is identified, the laser pulse signal is sent to a DSP main control circuit (6) through a preliminary detection signal parallel sending module (504), and the enabling high-speed ADC sampling time with a width of 2us is controlled through a wave gate module (505).

8. The control method of a long-distance follow-up laser seeker as claimed in claim 5, characterized in that: The DSP main control circuit (6) comprises a DMA parallel receiving module (601), a signal locking solution module (602), a proportional guidance solution and control module (603), an automatic gain control module (604), and an external communication module (605); The digital quantity of the laser pulse signal preprocessed by the FPGA preprocessing circuit (5) is received through the DMA parallel receiving module (601), the signal locking solution module (602) uses a coherent detection algorithm to extract the target reflected laser echo signal from the laser pulse signal preliminarily detected by the FPGA preprocessing circuit (5), the proportional guidance solution and control module (603) performs sum and difference operations on the target reflected laser echo signal to obtain the missile-target line of sight angle error, and converts it into a missile-target line of sight angle rate signal through the proportional guidance algorithm for the dual-axis servo system (3), and the automatic gain control module (604) controls the gain change of the signal conditioning circuit (4).

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