Masaaki ADACHI^*

Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan

(Received September 13, 2007; Accepted January 23, 2008)

White-light interference has changes in fringe contrast. When phase-shift techniques are applied to white-light interference, the phase-shift algorithm which can extract the phase accurately under the contrast changes is required. There is often another requirement that the phase shift between frames should not be restricted to π/2. Computer simulations show that the well-known algorithms have non-negligible errors under both requirements. To find an algorithm which will satisfy the requirements, I extract individual terms (I_j + I_k or I_j - I_k) in an algorithmic equation by considering symmetry of light intensity against phase, where I_j is light intensity just after the j-th phase shift. Using computer simulations, I search for appropriate coefficients by which the terms are multiplied in the equation, finally finding an algorithm which satisfies both the requirements with the phase shift used.

Key words: phase shift, algorithm, white-light interferometer, fringe contrast, error estimation, computer simulation

^*E-mail address: adachi@t.kanazawa-u.ac.jp