Laser confocal measurement system for curvature radii of lenses

Combined an air bearing platform and a laser interferometer, a set of non-contact and high precision system for curvature radius measurements of lenses is developed based on the axial focusing of confocal technique. The developed system is characterized by that the peak point of the confocal axial intensive curve corresponds to the focus of an objective. On the characteristic, it identifies precisely the cat-eye and confocal positions of the test lens. Then it takes the laser interferometer to obtain the position coordinates of the cat-eye and confocal positions and calculates the curvature radius of the lens. Furthermore, the main control software drives an air bearing slider with a test lens to achieve the scanning measurement near the cat eye and confocal positions, and then acquires signals and processes data. Experimental results show that the measurement system has the reproducibility less than 2 μm, which meets the requirements of curvature radius measurement for high precision. The developed measurement system has the advantages of high test speed, easy operation, simple structure and easy to be miniaturized.