Study On Photoelectronic Autocollimatic System Based On Invariant Light-distance

The essence of the traditional photoelectric autocollimator based on QPD is by detecting the location of the light intensity center of gravity to achieve the angle measurement. And, however, we found that when measuring the deflection angle of the target with having space linear motion, due to laser divergence angle, spot diffraction ring, the uniformity of the spot, as well as the partial burr of the target mirror, the light intensity center of gravity is changing, and that will increase the measurement error. Therefore, for meeting the high precision measurement requirements, the traditional structure with plane mirror reflection is merely suitable for measurement in a fixed position angle, but not for the moving targe with space linear displacement caused by changes of light-distance. So, in this thesis, we designed a new kind of a photoelectric autocollimator system based on invariant light-distance. We used two right-angle prisms to form a structure which can detect the angle changes. And the location of the laser and QPD is fixed, that can ensure the light-distance of the system optical path constant and reduce the measurement error. The main research contents as follows:First of all, we have done the analysis and comparison of the traditional small angle measurements, and studied on the various of laser's characteristics. On this basis, the theory of invariant light-distance is put forward. We designed a new optical structure based on this theory and carried out the mathematical derivation.Secondly, the system optic devices have been selected and analyzed. Through the simulations and experiments, we researched influences of the optic devices to the measurement results.Thirdly, by researching characteristics of laser's loading, we designed hardware circuit of the automatic control system of the invariant light-intensity. Besides, we carried out the circuit designs of the signal receiving and processing.Finally, we carried out the analysis of the system error and some related experiments.The measurement range of the photoelectric autocollimator system is greater than±100", and the measurement accuracy is 0.1", which achieved the desired purposes of measurement.In this thesis, the photoelectric autocollimator system based on invariant light-distance has characteristics of compact structure and easy loading and unloading, while ensuring the case of high-precision measurement, it can achieve measurement with two-dimensional and real-time dynamic. It lays the foundation for the measurement of straightness of high precision guide, as well as the compensation of Abbe error, which has a certain theoretical significance and engineering value.