A new technique for phase introduction in a two-beam interferometer for amplitude image subtraction

Image subtraction to detect the difference between the two images is carried out by implementing a phase reversal technique in a two-beam interferometer. The phase (contrast) reversal is accomplished by varying the pressure within an air-filled quartz cell inserted in one of the arms of the interferometer. Initially, the interferometer is aligned to obtain board interference fringes in the cell region. Then the input imageries are introduced in both the arms of the interferometer, and adjusted for exact registration as seen in the plane of observation. By introducing the phase charge of π-radians between the two arms of the interferometer, the difference between the inputs is detected in real-time. Phase shift calibration and amplitude image substraction carried out by the proposed method using a Mach-Zehnder interferometer is presented with the experimental results.