Research On Photoelectric Integrated Chip With High-precision Angular Displacement Sensor

Angular displacement sensor,also known as photoelectric encoder,is a digital angular displacement measuring device integrating light,machine and electricity.At present,it has been widely used in engineering practice.It is an important component unit in intelligent processing,satellite communication,servo system,aerospace and other systems.In certain important applications,such as aerospace technology,the system requirements are demanding not only for encoder angle measurement accuracy and resolution but also size of the system.At present,in the domestic market,high-end angular displacement sensors are mainly made of foreign products,and optoelectronic integrated circuits,as the key technology part,are currently all controlled by foreign companies.Under this background,the work of this paper relies on the major scientific instrument and equipment development project of the Ministry of Science and Technology,and the subject of this work is the design of ASIC optoelectronic integrated chips.According to the requirements of the High-tech Research and Development Center of the Ministry of Science and Technology,and in order to fill the gap of domestic high-end angular displacement sensor products,break the monopoly of foreign markets and the technical barriers of high-end products,the work of this paper is devoted to the development of special-purpose optoelectronic integrated chips and signal processing chips to achieve Domestic replacement for high-end angular displacement sensors.On the basis of consulting the research results at home and abroad in detail,starting from the principle of photoelectric integration technology,the working principle,performance index and current technology of photoelectric detector are studied.Indepth research is carried out on the integration methods of absolute code track and incremental code track detectors,and the detector function is expanded to realize the integration of grating integration and dual-code track detectors.An additional process is added to the standard CMOS process to realize a P-I-N photodiode with a dielectric layer window and an anti-reflection coating.The large size of 22?m×600?m is realized,and the integration time can reach the microsecond level.It has a high working speed and completes the detection and processing of high-speed optical signals of the chip in this paper.At the same time,the generation principle and subdivision method of moiréfringe photoelectric signal are deeply analyzed,the relationship between signal quality and subdivision error is mainly studied,and the signal waveform equation when there is error in moiré photoelectric signal is established.According to the output principle of moir(?) fringe signal,a photoelectric receiving chip is designed.Combined with the working mode of each code track,the corresponding readout circuit with high speed and high linearity is designed,which integrates the photodetector,signal amplification circuit and signal driving circuit.At the same time,the circuit design of the auxiliary module is completed according to the function of the chip,which realizes the signal reception,photoelectric signal conversion,signal amplification and the adjustment of the gain and offset of each channel amplifier.The system bandwidth can reach 300 k Hz,the output swing of analog signal can reach0.6?2.4V,and the output consistency of signal is greater than 95%.Complete the integration of photodetector,signal amplification circuit,signal control circuit and other systems,and realize the development of photoelectric encoder integrated chip.According to the subdivision principle of electronics,a high-speed,low-noise and high-precision analog-to-digital converter chip is designed to convert the analog signal output by the photoelectric receiving chip.At the sampling rate of 10 MSps,SFDR is 71.4d B,SNDR is 67.0d B,SNR is 73.8d B and ENOB is 10.71 bit.Using the method of digital domain calculation and correction,the signal is input to the sample and hold circuit for anti aliasing filtering and sampling.Further electronic subdivision of the output signal of incremental code channel.For the output signal of absolute code channel,the inconsistency correction is carried out after adaptive operation,and the consistency of the output signal is more than 95%.The photoelectric integrated circuit,the core device of high-precision angular displacement sensor,is applied to the encoder prototype.The development of the encoder prototype equipped with this chip is completed,and the error in the encoder fine code signal is deeply studied.Based on particle swarm optimization algorithm and cuckoo algorithm,the sinusoidal error,amplitude and DC component error in the signal are compensated.A special test system is developed for photoelectric receiving chip and signal processing chip.Combined with the working principle of the two chips,the functional test of the chip is carried out first.After the test performance meets the expectation,a precision detection platform is built to test the encoder equipped with this chip.A 22-bit encoder prototype is selected for testing to verify the effectiveness of the error compensation scheme proposed in this paper.The peak and peak of fine code subdivision error can be reduced by about 60%.Further,the 25-bit encoder prototype is tested in real time.Through the comparison before and after error correction,it is obtained that the measurement accuracy in a single cycle can reach0.41".The main technical indicators of the project products have reached the international leading level,that is,the resolution is greater than 25-bit and the angle measurement accuracy is less than 1",which makes the equipment realize domestic substitution in the domestic high-end product market and completely break the blockade of foreign countries.