High Precision Semiconductor Laser Temperature Sensing And Control System Based On Phase Recognition

Semiconductor laser with the advantages of tiny, high efficiency, simple structure,low cost and easy modulation gained widespread application in high-precisionmeasurement, laser ranging, laser alignment, optical information processing, opticalstorage, optical computer and laser fuze. But the working state of the semiconductorlaser is affected by temperature is heavy. Temperature instability will cause outputwavelength of laser drifting that greatly influence the interferometry. So to preciselycontrol the temperature of the semiconductor laser is priority problems in practicalapplication.The purpose of this paper is to control the temperature of the semiconductor laser,with the principle of RC first-order filter circuit and thermistor temperaturecharacteristic, design the improved secondary charge and discharge circuit and designea wide range and high precision of temperature sensing circuit. In this system, designthe hardware counting module and the USB interface module for data communicationwith structure of FPGA and USB. Then configurating CY7C68013A chip withfirmware,transfer data to the PC and do the relevant analysis on the experiment. Themain research content is as follows:Firstly, introduces the characteristics of the semiconductor laser, analyze thetemperature impact is an important factor of output wavelength of semiconductor laser,and combined with Michelson interference experiment, illustrates the necessity oftemperature control on it from the point of quality of interference fringe.Secondly, select the thermal resistor as temperature sensor. Through the comparingand analyzing with traditional bridge circuit, using the thermal characteristics ofnegative temperature coefficient of resistance that design the RC circuit which includingsine signal source circuit, second order filter circuit, amplifier and comparison circuit.The second charge and discharge circuit on the basis of the design. Calculating amathematical relationship between resistance and temperature, and the PCB board isalso designed.Thirdly, the system adopts FPGA and USB architecture, FPGA as controller, USBas a data transmission channel. Introduce the FPGA and USB technology; design thepulse counting module of pulse width and USB data communication interface module.On the software, design the USB driver, firmware program of USB control chip, andNios II program which using with PC communication. Design TEC driving circuit, PCinterface developed on VC++6.0platform and display data on real time. And controlFPGA to drive TEC by circuit to make automatic adjustment.Finally, the experiment of the system and the error were analyzed.