PURPOSE: To ensure a function with a multicolor and continuous control of sensitivity. CONSTITUTION: A reference surface PC functioning optically in association with a plane where the wave surface of an optical beam is analyzed is determined by incident lenses 02, 04. A two-dimensional mesh-shaped grid GR is arranged perpendicularly to the beam in this plane PC. Different sub-beams with different diffraction degrees are focused on an intermediate focusing plane PF by a first lens L1 . A mask positioned in the vicinity of the plane selects at least one relating to three different deffraction degrees out of sub-beams. A second lens L2 leads the selected sub-beam to a zero sensitivity plane PO co-serving with the grid plane. An interference image is observed at a work plane Pa positioned at a position at a specified interval (d) from a zero sensitivity plane PO.
LATERAL THREE-WAY DISPLACEMENT TYPE ACHROMATION OPTICAL INTERFEROMETER