Research On Design Of Alignment System Based On Interference Fringe

Recently, the measuring approach by the means of alignment laser beam as the linear references has been greatly promoted. Laser alignment technology has been widely used in shape error measuring, such as linear, concentricity, flatness and parallelism. But the precision of Laser alignment in testing of long trace hasn't been improved for many years, because of some existing problems such as Laser beam's drifting, Laser beam's bending and the atmospheric perturbation, which can't be overcome under current technical conditions.A new kind of portable laser alignment system based on interference fringe is designed, to solve the problems existing in the measurement of linear error of long rail. Having been collimated and broadened, the laser beam can be projects onto the wedge-shaped plate. Because of the reflection on the two surfaces of the wedge-shaped plate, the laser beam become two cross beams of a cross angular. The photo-electricity sensor is used to detect the interference fringe's appearance in the crossed region of the two beams, and the output is treated by the measuring circuit to acquire the surface minute angle of the measured track. The measured data can be calculated by computer, to acquire the linear error of measured track.Integrating the feedback control circuit, filter program is used to calculate the offset of the photoelectric signal, and proportional control method is used to eliminating the DC residual existing in photoelectric signal, which would vary in the measuring process, to obtain higher measuring precision.Having integrated the wireless communication circuit into the newly-invented program, we can send the measured data to the wireless station by wireless communication circuit, and then the data can be transferred to the computer. The applicable program is developed by VC++ 6.0, to realize the USB interface's data reading, to display the real-time signal's motion, to save the measured data, and to calculate the linear error of the measured long trace. It makes data transmission and data processing much easier.Electronic devices with value of small volume and lower power consumption are used to design the measurement circuit, and Lithium Batteries are used as the power supply of the measurement circuit. It makes the system portable and testing easy. The experiments of Stability test, repeatability test, calibration test and real testing of long trace have been done. The results indicate that the system can function well and the performances have met the scheduled targets.