PROCESS AND DEVICE FOR AN INTERFEROMETRIC MEASUREMENT OF THE LINEAR DISPLACEMENT OF AN OBJECT WITH RECOGNITION OF ITS DIRECTION OF MOVEMENT

摘要

For interferometric measurement of the length of the linear component of movement of a moving point relative to a fixed point and simultaneous recognition of the direction of that movement, two merged or overlapping Fabry-Perot part interferometers are used to form an asymmetric pattern of the reflection or transmission intensity which is periodically dependent on the linear component of the path, the pattern having main and secondary maxima of different heights and main and secondary minima of different depths. The intensity variation is converted by a detector into electrical intensity signals which cross threshold values of trigger circuits to produce output pulses. The pulses are combined and counted to produce displays of the direction and to provide a reading of the instantaneous position of the movable point.