Integrated Technology Of Photoelectric Detection And Signal Processing In Picometer Resolutin Heterodyneinterferometer

The flourishment of gravitational wave detection and precision microelectronics manufacturing equipment is drving ultra-precision displacement measurement technology to a continuous improvement to the magnitude of picometer resolution,bringing challenges to the widely-used ultra-precision heterodyne laser interference technology.In order to achieve higher resolution in displacement measurement,a new generation of heterodyne laser interferometer uses signal processing technology based on biorthogonal lock in amplifier.However,in order to achieve measurement in picometer level,still need to suppress the noise in the various modules of heterodyne laser interference system to a certain level.Among them,the noise from the photodetection circuit and the signal processing circuit are the key factors that limit the noise level of the interferometric system.In this paper,the principle of ultra-precision heterodyne interferometry is introduced,and the photonic detection and signal processing are introduced in detail.The noise source and the equivalent noise voltage intensity range are analyzed,and the noise in the heterodyne interferometry system is finally established.Mathematical model is built between the noise intensity and the system resolution,as a basis to guide the work of noise suppression.Aimed at the resolution constrained by noise in the photoelectric detection circuit,the low-noise photoelectric detection technology of the picometer scale is studied in this paper.Based on the characteristics of the device of the photoelectric conversion element,according to the characteristics of the photoelectric detection,the photodetection of the photoelectric detection circuit is studied.The relationship between the bias voltage and the temperature under the fixed gain is designed,and the temperature compensation module is designed to suppress the influence of the ambient temperature on the detection output gain.The experimental results show that the temperature compensation circuit can adjust the system bias voltage in real time with the change of ambient temperature,and improve the gain stability of avalanche diode photoelectric conversion.The low noise optimization design of the multi-stage amplification module is carried out,and the high-frequency white noise and low-frequency noise mixed in the measurement signal are filtered out.The noise level of each device in the circuit can be quantitatively analyzed and used as the guidance to adjust the circuit parameters.As a result of the overall noise calculation,the device noise of the low-noise optimized amplifier circuit can be reduced by about 70%.In order to improve the practicability of the low noise photoelectric detection circuit,the self-gain circuit is designed to increase the detectable amplitude range of the input signal to meet the system's measurement requirements for different light intensity signals.Experiments show that the introduction of self-gain circuit will expand the amplitude range from 0.9V ~ 1.6V to 0.2V ~ 2V.A new generation of heterodyne interferometry system began to merge the traditional separation structure to form an integrated system,this model has gradually become a new design trend.At the same time,due to the long-distance transmission is easy to cause the signal integrity degradation and system electromagnetic interference,it also drives the heterodyne interference measurement to the integration system development.The sensitivity of the analog signal to the noise in the integrated system and the high noise characteristic of the digital signal are the main contradiction of the system,which is especially obvious in the high speed signal system.In view of this problem,this paper will start the low noise integrated system design based on high-speed modular mixed board design rules.Using the "Star Ground" to the ground design principles.Impedance design tool is used to carry on the impedance matching of the key signal in the system,and circuit design software is used to constrain the key connection.In addition,the paper focuses on the signal integrity simulation of the board power supply.According to the simulation results,the equivalent noise voltage caused by the power fluctuation is calculated quantitatively,and the design of the system power plane is repeatedly optimized in order to realize the picometer resolution.Finally,based on the above theoretical analysis and technical research,the experimental platform is designed and built to test the performance of the integrated system of photoelectric detection and signal processing.The experimental results show that the short-term measurement peak-to-peak displacement variation is 110 pm under 100 samples(2 seconds),and the standard deviation of is 18 pm.The long-term measurement peak-to-peak displacement variation is 216 pm under within 1 hour,and the standard deviation of is 28 pm.The long-term static peak-to-peak displacement variation under 500 smoothing is about 45 pm.