Highly sensitive interferometric system for optical surface contouring

In the present work we demonstrate a highly sensitive system for optical surface contouring constructed by combining phase conjugation and digital phase shifting interferometry. The phase conjugating mirror in the modified phase conjugate Michelson interferometer is based on degenerate four wave mixing in a photorefractive BTO crystal. Digital phase shifting interferometry is used to decode the interference fringe pattern. An increase in sensitivity and high measurement accuracy are achieved through this new combination due to the interferometric scheme and the phase shifting. Experimental results are presented. The interferometric system is flexible and undergoes further improvement.