Development of laser differential confocal radius measurement system

Aiming at the demand of high-precision radius metrology, a laser differential confocal radius measurement system is designed. Based on the property that the zero crossing point of a differential confocal intensity curve corresponds to the focus of the objective, the system uses the zero-crossing point to precisely identify the cat-eye and confocal positions of the tested device, and uses an interferometer to measure the distance between the two positions and achieve high-precision measurement of radius of curvature. The electrical control of the measurement system is realized with the main control software, which can accomplish axial scanning, data acquisition and data processing. Experimental results show that the system is less subject to environmental fluctuations and the measurement accuracy reaches at 3×10 ^-6, and the system meets the demand of high-precision metrology of radius of curvature.