Optical testing of lens systems with concentric design

It is well known that manufacturing of lens systems featuring concentric design is a difficult task mainly due to nontrivial testing required for optical surfaces sharing their center of curvature. We propose an inexpensive imaging method, which can be used to test the alignment, concentricity, the axial length of air gaps and figure errors of the optical surfaces in concentric lens systems. Our setup consists of a laser, collimating lenses, a beam splitter, testing and imaging arms. We demonstrate the functionality of this scheme by testing an artificial eye with concentric design. During the experiment, the laser beam travels along the optical axis of the testing arm until it is focused onto the surfaces of the artificial eye. The light is then reflected and directed into the imaging arm to the camera. We perform tests in two positions: first, when the focused beam hits the vertex of the convex lens of the eye, and second, when the light comes into the system perpendicular to the optical surfaces. By finding the distance between these two positions, we can obtain the radius of curvature of the lens surfaces. In addition, the images formed on the camera give us accurate information about the alignment and the quality of the optical system under the test. Our results also show that this method is a powerful technique to determine the position of air gaps in compound optical systems.