Automatic sphericity interferometer for testing lens radii

The majority of lens radii measurements are made with test plates. This technique has the disadvantage of bringing the lens into direct contact with the test plate which can cause scratching of the surface and subsequent rejection of the test unit. In addition, test plate measurements are subjective because they depend on the experience and skill of the operator. As an alternative, an automated interferometric technique was evaluated for its ability to measure lens radii. This method uses a fizeau interferometer with the following accessories: transmission sphere, lens mount, and digital radius slide. This technique, chosen for its ease of operation and noncontact approach, proved to be a more suitable approach to radius measurement than the use of test plates, because it eliminated both the subjectivity and contact associated with the test plates.