Evaluation of the aspherical surface of a plano-convex lens by refraction using an LCD.

We present a simple method to evaluate the curved surface of a plano-convex aspheric lens using an incoherent light source. We implement an exact ray trace to obtain analytical expressions for designing a set of geometric objects, placed within a plane, to produce by refraction a regular array of either circles or straight lines in the plane of detection when the optical system under test works in accordance with the nominal design. An innovative geometrical test is implemented to calibrate the position of each element involved in the measurement system. As part of the calibration process, we considered that the camera lens can be affected by the distortion aberration; therefore, we proposed a straightforward method to compensate for the defects introduced in the experimental images. Finally, we used the measured values of the slopes to recover the shape of the surface under test using an iterative algorithm; as a result, we obtained the geometric parameters describing the surface with a percentage error less than 1.7%.