Measurement of optically effective surfaces by imaging of gratings

Due to the increasing use of aspherical optics, there is a demand for innovative measuring methods that allow the flexible testing of a wide variety of optical components. With the measuring method presented in this paper the imaging properties of the optical component under test may be determined by making it part of an imaging system consisting of an electronic camera with lens, a special grid pattern and the object itself. The grid pattern is taken as a reference object whose resulting image recorded by the camera is evaluated in order to obtain the properties of the tested optical component. In favour of a high measurement accuracy phase shifting techniques and photogrammetric methods are used in the course of the evaluation of the reference structure and the characterisation of the tested optical surface. Unlike other techniques the presented measuring method does not require particular previous knowledge of the tested component and may be applied to both reflective and refractive optical surfaces. Measuring examples for reflective and refractive components are given, demonstrating the potential of the method.