Research and Design for the Laser’s Power Control System of Laser Direct Writing
|School||Harbin Institute of Technology|
|Course||Instrument Science and Technology|
|Keywords||Laser direct writing Acousto-Optic Modulator Stability of laser output PID|
Laser direct writing technology is one of the most important ways to produ-ce a binary optical component. In the production process, the stability of the lase-r’s power is essential to the components. However, affected by the external facto-rs, the laser output have a drift, which has direct impact on the etching quality. S-o it is necessary to control the laser’s power to achieve a constant power output and continuous-tuning.Using a system that applies the Acousto-Optic Modulator (AOM) for the ac-tuator could solve the problem properly. On the analysis of the performance and characteristics of AOM, a proper AOM system is selected. In the MATLAB envi-ronment, a mathematical model of AOM is successfully identified. And with the help of SIMULINK toolbox, a simulation model for PID controlling is designed. On the basis of theoretical analysis, a closed-loop optical power control system which uses +1 level diffraction light to control the +1 level is proposed. The diff-ractive light changed into electrical signal after photo electricity conversion. The-n by filtering, the electrical signal enters into a board applying a FPGA (field pr-ogramable gate array) chips. After processing, the signal is exported to the AOM drive to control the intensity of the diffraction light so that the system could achi-eve a stable output power and continuous power-adjustable.Using FPGA to design a PID controller is to use digital logic circuits to co-mplete PID control. Based on the analysis of structures and characteristics of the FPGA, a method to design a improved parallel structure of the PID controller on the basis of a FPGA is proposed. For PID algorithm and FPGA logic image’s co-nversion. It can reduce the logical components effectively and speed up the com-puting speed.The results show that, through closed-loop control system, the max amount of deviation of +1 Level diffraction power is 0.008mw whose stability is 0.399% and the setting time is about 300μs which is three times better than the time wit-hout control.The paper discusses the whole system hardware design, the improved parall-el structure of the PID controller design, serial communication procedures and st- ability experiment of optical power in detail. Finally, the thesis research is sum-med up, some deficiencies is analyzed and further optimize design is proposed.