The video shows a quick way to adjust the quarter waveplate to a geometric phase shifter. If the 1/4 waveplate is not aligned properly, after passing through it the beams have elliptical polarization and the interferograms have intensity variations, low contrast or even extinct at some phase shifts.

The geometric phase shifter (a 1/4 waveplate followed by a rotatable linear polarizer) works with any interferometer which outputs two beams having orthogonal linear polarisation states. The waveplate should have one of its main axes (fast or slow) at 45 degrees from both polarisation directions.

If one beam is extincted with the phase shifter polarizer (the one mounted on/before the camera lens), and the waveplate has one of the main axes aligned with its polarization direction, it does not change the polarisation state of the beam - so it will remain invisible. If one of the main axes of the waveplate is at 45 degrees from the polarization direction of the extinct beam, the beam will have the maximum intensity.

свернуть