EXTENDING THE UNAMBIGUOUS RANGE OF 2-COLOR INTERFEROMETERS

The unambiguous distance measurement range in two-color interferometry is generally understood to be limited to the equivalent or synthetic wavelength, which is inversely proportional to the wavelength separati on of the two colors. Here it is shown that one may extend the unambig uous range well beyond this limit by using optical phase information t o determine the synthetic-wavelength fringe order.