Research Of Monitoring Technology Of Electrothermal Optical Scanning Micromirror

With the development of integrated circuit technology and MOEMS technology,all kinds of testing instruments tend to be diversified,miniaturized and intelligent.Optical scanning micromirror is the core component of many micro-optical instrument systems,which can promote the miniaturization of optical systems and is widely used in spectrometers,medical imaging and other equipment.Various optical systems also put forward different requirements for scanning micromirrors,many of which require a large scanning range,such as Fourier transform spectrometer and optical coherence tomography for retinal scanning imaging,which require vertical large scanning displacement and two-dimensional large angle scanning mirrors,respectively.In the micro-scanning mirror,the electrothermal driving micro-mirror has the advantages of large scanning range,low driving voltage and linear driving.It has more room for development than other types of micro-mirror(electrostatic,piezoelectric,electromagnetic,etc.).However,the mismatch of driving mirror caused by voltage drift,jitter,process and external interference has a great impact on the accuracy of open-loop control,especially in micro-systems,which will seriously affect the scanning effect.The task is to realize real-time monitoring of vertical displacement and deflection angle of large-scale scanning electrothermal micromirror,and to control and rectify four mismatched driving arms according to the monitoring results,that is,to realize feedback control for two-dimensional micromirror.In this thesis,the main work are as follows:1.The optical system model of electrothermal micromirror and optoelectronic integrated chip is constructed.Based on the Gauss distribution theory of laser,two kinds of four-quadrant photodetectors are optimized through theoretical analysis and simulation.The size of single photodetector is 500 ?m*500?m,spacing is 500 ?m and 600 ?m respectively,and the light source is 850 VCSEL.2.The electrothermal micromirror with the optoelectronic integrated chip is designed and packaged.The vertical displacement and scanning angle of the electrothermal micromirror are monitored,which are displacement resolution of at least 0.413 um and angular resolution of 0.0067 degrees;3.To reduce the driving mismatch in the process of displacement scanning,STM32 single-chip computer and extended DAC circuit are used for feedback correction,which reduces the displacement output error by about 6%.and the initial correction accuracy is about 0.012?m.Meanwhile,the displacement monitoring accuracy is improved to 0.150 ?m.4.In order to improve the simulation performance,the current conversion circuit w ith controllable output mode and low power consumption is optimized,which can output displacement and angle on demand.The designed transconductance amplifier can convert the current within 20 ?A to voltage,and the transconductance gain is 84 K?.The final converting circuit can convert the change of 6?A to the output voltage of 360 mV on the basis of a certain original current.The innovation points are as follows:1.The electrothermal micro-mirror and photoelectric sensor chip is co-designed and packaged.The scanning displacement and deflection angle of electrothermal micro-mirror is synchronously monitored..2.Based on four-quadrant photoelectric detector and STM32 single-chip technology,the mismatch of actuators in the displacement scanning process of electrothermal micro-mirror is preliminarily corrected.3.A low-power current conversion circuit with controllable output mode is designed.The output mode can be controlled externally.This design is mainly used for the monitoring and control of various scanning micromirrors in MOEMS equipment.Especially for the monitoring of electrothermal micromirrors w:ith large scanning range,it can be used in imaging systems,optical communications,biomedicine,automobile industry and other fields.