Laser differential reflection-confocal lens thickness measurement

A new laser differential reflection-confocal lens thickness measurement (DRCTM) method is proposed for the high-accuracy measurement of the lens thickness. DRCTM uses the test beam reflected from the lens first and last surface to determine the vertex positions of the two surfaces. Differential confocal technology is used to precisely identify the lens vertexes of the lens first and last surfaces, thereby enabling the precise measurement of the lens thickness. Compared with the existing measurement methods, DRCTM has high accuracy and strong anti-interference capability. Theoretical analysis and experimental results indicate that the DRCTM measurement error can be limited to 0.0015%.