A Phase Locked Loop Analog System for Real-Time Phase Retrieval

It is often useful to know the effect an optical component has on the phase of light passing through it. Since optical detectors are sensitive to intensity, not phase, phase must be encoded in an intensity pattern in order to be detected. To do this, the beam under test is usually interfered with a reference beam and the resulting intensity distribution is analyzed to retrieve the unknown phase. Several methods can be used to retrieve the phase information from interference pattern.