Optical heterodyne interferometry has been widely used to measure linear or angular displacement for industrial applications. Nowadays, considerable need exists for more high-resolution, more high-speed interferometer system as a result of increasing demands for higher dimensional accuracy and productivity.
A new digital phase measuring concept for a heterodyne displacement measuring interferometer is presented for high-speed and high-resolution laser interferometer. A high bandwidth electronic counter with low resolution and a high-resolution phase meter with low bandwidth are used simultaneously. We design the beat frequency shifter and the phase meter with "heterodyne detection scheme" and PSD and low-pass filter circuit.
We test the performance of the designed beat frequency shifter and phase meter compared with general phase meter. And usefulness of that scheme is proved with static and dynamic test of the designed circuit and typical phase meter. Designed target specification is satisfied and the accuracy is improved by proposed scheme.
This paper presents a measuring method of all movement errors i.e. 5 degree of freedom of a translatory precision machine axis. This method is a simultaneous measuring technique in which two plane mirrors are used to generate an interferometric fringe pattern utilizing the optical principles of Twyman-Green interferometry. From the fringe pattern, one translatory and two rotational error components of the machine axis are simultaneously detected by using CCD camera vision and image processing techniques. And new optics are designed for simultaneous measuring of all movement errors. Experimental results demonstrate that a machine axis can be controlled with movement errors less than 50nm in vertical straightness, 0.2arcsec in yaw, and0.1arcsec in pitch.