Moiré Interferometry with White-Light
While high-sensitivity moiré interferometry requires monochromatic light, an auxiliary compensator grating removes the requirement. Experimental verification utilized white light for moiré interference of sensitivity 0.833 μm/fringe. Configurations readily amenable to compensation include moiré fringe multiplication by even factors and the minimum-deviation arrangement. Chromatic compensation is effective with virtual reference gratings as well as real reference gratings; in both cases the moiré interference system becomes achromatic. Compensation provides the special quality of nearly zero phase difference—an actual range of ±π—between interfering beams. Potential applications include use of electrical spark light sources for high-sensitivity dynamic moiré photography.