Laser differential confocal radius measurement method for the cylindrical surfaces

This paper proposes a laser differential confocal cylindrical radius of curvature measurement (DCCRM) method for high accuracy measurement of the radius of curvature of the cylindrical lens. Based on the property that the null point of an axial intensity curve precisely corresponds to the focus of the objective in a differential confocal system (DCS), the DCCRM uses the null point of the DCS axial intensity curve to precisely identify the cat's eye position and confocal position of the test cylindrical lens. The distance between the two positions is measured accurately using a laser distance instrument, thus achieving high precision radius measurement. In comparison with existing measurement methods, the proposed DCCRM has high measurement precision and strong environmental anti-interference capability. Theoretical analyses and preliminary experimental results indicate that the DCCRM has a relative measurement uncertainty of better than 0.03% and provides a new approach for a high precision radius measurement of the cylindrical lens.