Light beam pointing stability control system of high-power laser system

Abstract

A light beam pointing stability control system of a high-power laser system is characterized in that through a laser emitter, a lens, a position sensitive detector (PSD), a micro electro mechanical system fast reflector (MEMS fast reflector) and a data processing unit, it is ensured that a laser beam can still keep stable pointing when facing external interference such as environmental vibration; a PSD is used for capturing laser spot position information, a PID control algorithm is executed through an FPGA chip in a data processing unit, the rotation angle needed by the MEMS fast reflecting mirror is calculated, and light path adjustment is achieved through a driving module. The device has the advantages of high precision, quick response, low cost, miniaturization, real-time monitoring and feedback and the like, optical path errors caused by translation of the laser transmitter can be effectively corrected, the light beam pointing stability is ensured, high-precision detection, quick adjustment and an advanced control algorithm are integrated, and powerful support is provided for stable pointing of laser beams.

Description

Technical Field

[0001] The invention belongs to the field of laser technology, in particular to a light beam pointing stability control system for a high-power laser system. Background Art

[0002] Large-scale high-power laser devices contain a series of laser amplifiers and a large number of optical elements and components, with long optical paths and many devices. The physical requirements of the system have high requirements for the stability of the laser landing point, among which small focal spot and spatial overlap of multiple beams in target shooting put forward high requirements for the stability of the landing point. The efficient operation of the system requires the configuration of a corresponding optical path automatic alignment system to quickly correct the deviation of the beam caused by temperature changes, micro-vibration of the foundation and support frame, creep of the mechanical structure of the reflector, airflow and other random factors, so as to improve work efficiency. The so-called automatic alignment system is a technology involving multiple disciplines such as optics, mechanical design, and automatic control, which integrates science and engineering. It uses photoelectric sensors (charge coupled devices CCD, position sensitive detectors PSD, etc.) to measure the offset of the center of mass of the beam, send it to the servo control loop, and drive the fast reflector to rotate through the control system, so that the outgoing beam pointing remains stable. In order to solve the jitter problem, automatic beam alignment is usually used to improve the target accuracy. However, this method can only solve the chronic drift problem in a short period of time, and cannot solve the high-frequency beam jitter (100Hz) problem in the high-power laser system. Therefore, the present invention proposes a beam pointing stability control system and method for a high-power laser system to solve the high-frequency beam jitter problem.

[0003] Most of the current beam pointing stability control systems use CCD cameras and traditional piezoelectric ceramic fast mirrors for correction. For large-scale high-power laser devices, the cost of CCD cameras and traditional piezoelectric ceramic fast mirrors is very expensive. Therefore, inventing a beam pointing stability control system based on PSD and MEMS fast mirrors can not only optimize the system structure, reduce the size, and improve the linearity, but also has high economic value, which is very necessary for large-scale high-power laser devices. Summary of the invention

[0004] The purpose of the present invention is to propose a beam pointing stability control system and method for a high-power laser system, which controls the direction of the laser beam by adjusting the angle of a MEMS fast-reflecting mirror at high frequency, thereby achieving the purpose of controlling the direction of the laser beam. This system only needs one PSD and a MEMS fast-reflecting mirror for a single path to efficiently complete the beam pointing stability control of the optical path. Among them, the MEMS fast-reflecting mirror has the characteristics of low price, small size, and high linearity, which not only greatly simplifies the design of the beam pointing stability system and improves the economic benefit; but also implements the algorithm control of the system based on the field-programmable gate array (Field-Programmable Gate Array, hereinafter referred to as FPGA) technology, which greatly improves the operation speed of the system.

[0005] To achieve the above objectives, the technical solutions of the present invention are as follows: A beam pointing stability control system for a high-power laser system is characterized in that: the system includes a laser transmitter, a lens, a PSD, a MEMS fast-reflection mirror and a data processing unit, and is controlled by a PID algorithm. The MEMS fast-reflection mirror includes a mirror surface and a driving module, the MEMS fast-reflection mirror is located between the laser transmitter and the PSD, the PSD includes a signal acquisition module and a signal processing module, the data processing unit includes an FPGA chip, a digital-to-analog conversion module and an analog-to-digital conversion module, and the data processing unit is connected to the PSD and the MEMS fast-reflection mirror respectively.

[0006] When the system is working, the light signal emitted by the laser transmitter passes through the lens of the lens device, is collected by the PSD and sent to the data processing unit for analysis and processing. When the light path of the light signal after passing through the lens is offset due to environmental vibration or other interference, the light signal collected on the PSD will deviate from the center point. The signal processing module of the PSD converts the light signal into an electrical signal to represent the coordinates of the deviation from the center point. The analog-to-digital conversion module sent to the data processing unit is processed by the FPGA algorithm and converted into the required rotation angle of the MEMS fast mirror. The data processing unit sends the driving instruction of the digital signal of the required rotation angle of the MEMS fast mirror to the digital-to-analog converter of the driving module, which converts the received digital signal into an analog signal, and then the voltage amplifier amplifies the analog signal. Then the driving module applies the amplified analog signal to the actuating beam, and then drives the mirror to deflect through the coupling column, readjusts the light path, and corrects the light spot back to the center point of the PSD.

[0007] The beam pointing stability control system further comprises an oscilloscope and a computer connected to the PSD module. The real-time position of the light spot on the PSD can be viewed through the oscilloscope or the computer.

[0008] The driving module receives the driving instruction from the data processing unit, converts the digital signal into an analog signal through digital-to-analog conversion, and then drives the mirror surface of the MEMS fast reflection mirror to deflect after amplification by a voltage amplifier.

[0009] The FPGA chip of the data processing unit is also used to execute algorithm processing, and calculate the deflection angle required by the MEMS fast reflection mirror according to the light spot position offset fed back by the PSD, so as to ensure the stable pointing direction of the laser beam.

[0010] The MEMS fast mirror rotation angle , satisfying the following formula:

[0011] Wherein, S is the translation amount of the laser emitter, and L is the distance between the mirror surface of the MEMS fast reflection mirror and the photosensitive surface of the PSD.

[0012] The technical effects of the present invention are as follows: 1) The present invention adopts a more cost-effective and compact position sensitive detector (PSD) combined with a fast reflector based on micro-electromechanical system (MEMS) technology, which can not only significantly improve the control efficiency of beam pointing stability, especially in high-frequency jitter suppression, but also effectively optimize the system structure and reduce costs, which is of great significance for promoting the development of large-scale high-power laser devices.

[0013] 2) The present invention uses PSD to measure the position of the laser deviating from the center point, and corrects the position error by rotating the MEMS fast mirror, thereby completing the design of the beam pointing stability control system. This method uses only one PSD, which has considerable economic value for large-scale high-power laser devices; the use of MEMS fast mirrors has the advantages of small size and high linearity, which greatly simplifies the structure of the system; the combination of FPGA chips and PID algorithms improves the system operation speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of a beam pointing stability control system of a high power laser system of the present invention; Figure 2 Schematic diagram of the corrected optical path before and after the beam is translated Figure 3 This is a flow chart of the beam pointing stability control of the high power laser system of the present invention; In the figure: 1-laser emitter; 2-MEMS fast reflector; 3-lens; 4-PSD; 5-data processing unit; 6-driving module; 11-laser emitter after translation; 21-MEMS fast reflector mirror after correction. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the accompanying drawings, but the protection scope of the present invention shall not be limited thereto.

[0016] Figure 1 This is a schematic diagram of a beam pointing stability control system of a high-power laser system of the present invention. As shown in the figure, a beam pointing stability control system of a high-power laser system includes a laser emitter 1, a MEMS fast reflection mirror 2, a lens 3, a PSD4 and a data processing unit 5.

[0017] The MEMS fast reflection mirror 2 is located between the laser emitter 1 and the PSD 4. The PSD 4 and the driving module 6 of the MEMS fast reflection mirror 2 are respectively connected to the data processing unit 5. The data processing unit 5 is connected to the MEMS fast reflection mirror and the PSD.

[0018] When the system is working, the light signal emitted by the laser transmitter changes the direction of the incident light beam after being reflected by the MEMS fast reflector. The reflected light beam passes through the convex lens, and the light spot is finally focused within the field of view of the PSD photosensitive surface. The light spot position offset feedback by the PSD controls the deflection of the MEMS fast reflector, thereby ensuring that the light spot is at the center of the PSD. When the light path of the light signal after passing through the lens is offset by environmental vibration or other interference, the light signal collected on the PSD will deviate from the center point. The signal processing module of the PSD converts the light signal into an electrical signal to characterize the coordinates of the deviated center point. The analog-to-digital conversion module sent to the data processing unit is processed by the FPGA algorithm and converted into the required rotation angle of the MEMS fast reflector. The data processing unit sends the driving instruction of the digital signal of the required rotation angle of the MEMS fast reflector to the digital-to-analog converter of the driving module, converts the received digital signal into an analog signal, and then the voltage amplifier performs voltage amplification on the analog signal. Then the driving module applies the amplified analog signal to the actuating beam, and then drives the mirror to deflect through the coupling column, readjusts the light path, and corrects the light spot back to the center point of the PSD.

[0019] Figure 2 The diagram is a schematic diagram of the corrected optical path before and after the beam is translated. As shown in the figure, the MEMS fast mirror is 45° to the horizontal plane. When the laser is translated, the optical path will also change, such as Figure 2 The laser beam is reflected by the MEMS fast mirror and focused by the lens. The transmitted beam hits the PSD, and the light spot moves from the origin to P(x,y). The size of the PSD photosensitive surface is × , the photocurrent output by the four electrodes is , , , , with the center of the photosensitive surface coordinate as the origin. In order to correct this deflection error, it is necessary to control and drive the MEMS fast mirror to rotate a certain angle to correct the error.

[0020] Assume that the translation of the laser emitter and the displacement of the light spot are both S, and the rotation angle of the MEMS fast reflection mirror is , like Figure 2 As shown, point A is the incident point of the laser on the MEMS fast mirror, point C is the intersection of the optical path after translation and the vertical axis, and point D is the center point of the PSD. AD is the distance between the incident point of the laser on the MEMS fast mirror and the vertical axis, and AC is the translation distance of the laser, so AC=S. The AD distance can be measured during the experiment and is set to L, which is a known quantity. The angle and length in the optical path are as follows: Figure 2 As shown, the following relationship can be obtained:

[0021]

[0022]

[0023] The deflection angle of the MEMS fast mirror is

[0024] Therefore, the data processing unit can calculate the required deflection angle of the MEMS fast mirror through the position signal measured by the PSD, thereby correcting the error and completing the beam pointing stability control.

[0025] Figure 3 This is a flow chart of the beam pointing stability control of the high-power laser system of the present invention. As shown in the figure, the coordinate information of the laser at the PSD is collected by a photosensitive sensor, and the coordinate information is transmitted to the FPGA. The compensation angle required for the MEMS fast mirror to rotate is obtained through algorithm processing, and finally the compensation angle is transmitted to the actuator to drive the MEMS fast mirror for driving correction, so that the laser is corrected back to the center point of the PSD.

[0026] Experiments show that the present invention can complete the beam pointing stability control using only one PSD and one MEMS fast mirror, which greatly simplifies the structure of the system and can effectively reduce the development costs of structural parts, optical parts and related environmental protection components. It has considerable economic value for large-scale high-power laser devices and has important application prospects in the field of laser technology.

Claims

1. A beam pointing stability control system for a high power laser system, characterized in that: include: A laser transmitter, used for emitting a laser beam; A lens is arranged at the output end of the laser transmitter and is used to focus the laser beam; The PSD has a signal acquisition module and a signal processing module, which are used to collect the position information of the laser beam focused by the lens on the photosensitive surface of the PSD and convert the position information into an analog signal; The MEMS fast reflector includes a mirror surface and a driving module, and is disposed between the laser emitter and the PSD to reflect the laser beam and adjust its direction; The data processing unit is connected to the signal processing module of the PSD and the driving module of the MEMS fast mirror, respectively, and is used to receive the analog signal output by the PSD, calculate the required rotation angle of the MEMS fast mirror through the FPGA chip executing the PID control algorithm, and convert the angle into a driving instruction and send it to the driving module of the MEMS fast mirror; wherein, the driving module receives the driving instruction of the data processing unit, drives the mirror deflection of the MEMS fast mirror, so as to adjust the direction of the laser beam, so that the spot of the laser beam on the PSD is kept at the center position or within a predetermined range.

2. The beam pointing stability control system of the high power laser system according to claim 1, characterized in that: The device also includes an oscilloscope and a computer, which are respectively connected to the signal processing module of the PSD and are used for real-time monitoring and displaying the spot position of the laser beam on the PSD.

3. The beam pointing stability control system of the high power laser system according to claim 1, characterized in that: The photosensitive surface of the PSD has four electrodes for outputting a photocurrent signal related to the position of the light spot. The photocurrent signal is processed by the signal processing module of the PSD and converted into coordinate information representing the deviation of the light spot from the center point.

4. The beam pointing stability control system of a high power laser system according to claim 1, characterized in that: The mirror surface of the MEMS fast reflection mirror is arranged at 45 degrees to the horizontal plane to facilitate the reflection and adjustment of the laser beam.

5. The beam pointing stability control system of a high power laser system according to claim 1, characterized in that: The driving module receives the driving instruction from the data processing unit, converts the digital signal into an analog signal through digital-to-analog conversion, and then drives the mirror surface of the MEMS fast reflection mirror to deflect after amplification by a voltage amplifier.

6. The beam pointing stability control system of a high power laser system according to claim 1, characterized in that: The FPGA chip of the data processing unit is also used to execute algorithm processing, and calculate the deflection angle required by the MEMS fast reflection mirror according to the light spot position offset fed back by the PSD, so as to ensure the stable pointing direction of the laser beam.

7. The beam pointing stability control system of a high power laser system according to claim 1, characterized in that: The MEMS fast mirror rotation angle , satisfying the following formula: Wherein, S is the translation amount of the laser emitter, and L is the distance between the mirror surface of the MEMS fast reflection mirror and the photosensitive surface of the PSD.

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