Research On Wide Range And High Precision Spot Position Detection System Based On Four Quadrant Detector

Laser spot position detection technology has gained a lot of attention in modern science and technology and scientific research,playing an important role in laser guidance,space free communication,precision measurement,optical tweezers and other fields.In the extreme ultraviolet lithography light source system,beam pointing control is a core technology,which is related to the conversion efficiency of the extreme violet light and the safety of the light source system,and the beam pointing control effect depends on the laser spot detection technology,so it is necessary to study the spot position detection technology.In the spot position detection,it is necessary to select the appropriate photodetector according to the application environment,so we choose a high sensitivity and high response speed four-quadrant detector as the spot position detection device of the extreme ultraviolet lithography light source system.The specific research content is as follows:(1)The basic structure and working principle of the four-quadrant detector are introduced in detail,based on which the pulsed laser spot position detection system is built,and the evaluation parameters of the system are analyzed;The detection system is divided into three parts: front-end optical system,core four-quadrant detector,back-end signal acquisition and data processing system.and introduces in detail the structural composition of each part and the tasks undertaken in the detection system;The traditional spot position calculation algorithm is introduced,which is ready for the subsequent improvement of the spot position calculation algorithm and the analysis of the influencing factors of spot position detection.(2)The factors affecting the position detection system of pulsed laser spot are deeply analyzed.Firstly,the influencing factors such as spot energy distribution,radius and position are analyzed qualitatively;Then,the composite noise interference model is established based on the analysis of noise sources and noise interference mechanisms;finally,the influence of detector performance and spot position solution algorithms are briefly analyzed.(3)The high-precision detection technology of laser spot position is studied.Firstly,the mathematical model of the laser spot position detection error is established,and the influence of the spot parameters and noise on the spot position detection error is quantitatively analyzed.In order to suppress the system noise,a correction algorithm is proposed to suppress the inherent noise of the system,and the Kalman filter is built to suppress the random white noise of the system.At the same time,a second-order extended error compensation algorithm based on polynomial fitting is proposed,which expands the detection range of spot position,and improves the problem that the traditional algorithm can not take into account the calculation speed and detection accuracy.(4)Built a spot position detection platform for testing.The platform verifies that the four channel synchronous high-speed acquisition circuit designed in this paper can detect the pulse signal with k Hz and ns pulse width,and can meet the design requirements;At the same time,test the designed filter,and the test results verify the feasibility and practicability of the filter;Finally,the improved spot location algorithm is tested to verify the superiority of the improved algorithm over the traditional algorithm.