Measurements of wave front distortions of optical radiation using a shadow method V. I. Bredikhin*, S. P. Kuznetsov Institute of Applied Physics RAS 46 Ulyanov Str., Nizhny Novgorod 603950, Russia ABSTRACT zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCB The technique for measuring wave front distortions in optical elements by the shadow method is developed. Shadow pictures obtained for mutually perpendicular orientations of the Foucault knife-edge are the distributions of components of the gradient of the function describing the wave front relief, so that its shape can be restored by means of integration. An example of measurements of wave front distortions in large-scale optical KDP crystal elements employing the IAB 451 device is given. Keywords: shadow method, measurements of wave front The problem of quality control of large-aperture optical elements is still urgent. This control is usually carried out employing interferometer methods. However, an extension of the element size increases the complexity and cost of interferometers, as well as the complexity and consumption of labor. Thus alternative methods are explored We use the IAB 451 shadow device for this purpose. It should be noted that shadow methods are not inferior to the interferometer ones either in sensitivity or accuracy, and they enable one to investigate samples of much larger sizes. But the specific character of shadow pictures impedes their treatment and up to now they were employed as qualitative ones or for rough estimates. The available computer technologies permit to eliminate these disadvantages. Figure 1 deals with the simplified optical scheme of the shadow device illustrating a light beam forming an image of an object point. We consider the processes in the geometric optics approximation. Note that in the focal plane of lens 3 where the Foucault knife-edge is situated, there is an image of the lighting slot located in the focal plane of lens 2. On the other side, the system of lenses 3,5 builds the image A' of a point of the investigated sample A in plane 6. 1. INTRODUCTION 2. SHADOW METHOD A' zyxwvutsrqponmlkjihgfedcba 2 3 Fig. 1. Shadow device scheme. 1 - illuminator slot; 2, 3 - lenses of illuminating and receiving collimators, respectively; 4 - the Foucault knife-edge; 5 - recording device lens; 6 - image plane of investigated object; 7 - illuminator slot image. * bredikh@appl.sci-nnov.ru 98 Eighth International Conference on Laser and Laser Information Technologies, edited by Vladislav Ya. Panchenko, Nikola V. Sabotinov, Proceedings of SPIE Vol. 5449 (SPIE, Bellingham, WA, 2004) • 0277-786X/04/$15 • doi: 10.1117/12.563105