US Patent 12104897 Interometric optical system

An interferometric optical system for measuring a test object, including: i) a reference object comprising a partially reflective reference surface; ii) a light source module configured to direct first and second input beams through the reference surface to the test object at an angle to one another; iii) a detector positioned to detect light reflected from the reference surface and one or more surfaces of the test object; and iv) an aperture positioned to selectively block light from reaching the detector, wherein the angle between the first and second input beams causes the aperture to block light from the first input beam reflected by the reference surface and pass light from second input beam reflected by the reference surface, wherein the two input beams have a mutual coherence length smaller than twice an optical distance between the reference surface and the test object.