Long Guide Straightness Error Measurement Based on Laser Interference

A new kind of straightness error measurement system based on laser interference is developed. High stability He-Ne laser beam which is collimated and broadened is cast on wedge-shaped glass plate, on which back and front the light reflects and interfere. The angle of the guide and target would be changed when the motion of the target is along the guide, if there is linearity error existing in the guide. So interference stripes would be moved by the changed angle of the guide and target. In this way the straightness error of the guide is transferred to the displacement of the interference stripes. Then interference stripes are tested by photoelectricity sensor and deviation of the laser beam is acquired. The comparison tests and repeated tests show that the straightness error is 623.103μm when the tested long guide is 50 meters long.