Simple lateral shearing interferometer using phase shifting interferometry technique

In order to use phase shifting interferometry(PSI) in lateral shearing interferometer, piezoelectric transducer(PZT) is mainly used. But because PZT has many error sources and the moving distance for required phase shifting is very short, the phase shifting quantity has always considerable errors. We present a simple phase shifting technique without PZT. Moving the wedge plate parallel to the first wedge surface changes the phase difference between the original wavefront and the sheared wavefront. This method makes the shearing interferometer very simple in spite of using PSI technique. We derive the phase shifting relations originated from the moving wedge and discuss some error factors.