Non-contact measurement method for thickness of optical element

In order to realize non-contact central thickness measurement of the optical elements,an non-contact measurement system is established based on the electrical-optical scanning technology.Continuous moving light points are acquired in the optical axis when annular light produced by electrically controlling the optical switch array crosses the axicon.When the optical element places in the middle of these continuous moving light points,the thickness of the optical elements can be evaluated by monitoring the reflective light energy because the reflective light energy can present a peak when one of light points coincides with a surface of optical element.The mathematics model for testing the thickness of parallel plane plate and lens central thickness are built respectively.The measurement range and accuracy are analyzed in theory.The results show that the measurement range for parallel plate element varies from 5507 mm to 26 mm with the cone angle of axicon increasing from 1°to 40°,its materials refractive index is 1.52 and its radius is 100 mm,and the minimum measurement accuracy can reach to 2.5μm with measurement range of 26 mm.It can satisfy the non-contact measurement requirements of the central thickness of the optical elements.