Patent ID: 8537369

Claim:
A system comprising: a polished opaque plate having a first surface and a second surface opposite said first surface; a first single shot phase-shifting interferometer configured to require only one instantaneous interferogram to extract an interferometric fringe phase, positioned so that said first polished opaque plate surface is in an interferometer channel of said first phase-shifting interferometer; a second single shot phase-shifting interferometer configured to require only one instantaneous interferogram to extract an interferometric fringe phase, positioned so that said second polished opaque plate surface is in an interferometer channel of said second phase-shifting interferometer; said first and second single shot phase-shifting interferometers configured to provide data sufficient to measure shape of said polished opaque plate and thickness variation of said polished opaque plate; and a computer programmed to use an algorithm employing the phase measurement of interferometric fringes to cancel out vibration terms in a calculation of a thickness map of said polished opaque plate; said computer further programmed to control said first and second single shot interferometers to obtain data acquisition simultaneously with each other.