Dissertation > Industrial Technology > Radio electronics, telecommunications technology > Photonics technology,laser technology > Laser technology, the maser > Laser applications

Research and Design for the Laser’s Power Control System of Laser Direct Writing

Author LvYunFei
Tutor JiangXiuZhen
School Harbin Institute of Technology
Course Instrument Science and Technology
Keywords Laser direct writing Acousto-Optic Modulator Stability of laser output PID
Type Master's thesis
Year 2008
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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.

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