A new exposure method using cover glass

We present a new exposure method to achieve super resolution of a projection lens. The idea is based on a cover glass inserted between an optical lens and image plane. We have designed a projection lens system using a cover glass. It has found that the resolution of the projection pattern can be improved by use of a cover glass under the condition that the practical size of the projection lens is restricted. We have also set up a proto-type exposure evaluation system of reduction projection lens. It has been found that projection image of mask pattern was improved using a cover glass inserted between a projection lens and its image plane. We have also found that projection image of mask pattern was much improved by use of both phase shifting mask and a cover glass inserted between a projection lens and its image plane.