| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a system which monitors a position of one or more optical elements in a projection lens. <P>SOLUTION: An interferometer system includes a plurality of interferometers 110 and 120 configured to respectively derive a first wave surface and a second wave surface from input radiation and to synthesize the first and the second wave fronts to provide output radiation conveying information on a difference in optical lengths between a path of the first wave surface and the path of the second wave surface. Each interferometer has a reflection element positioned in the path of the first wave surface. At least one of the reflection elements of the interferometers is attached to a first object. The interferometer system also includes a plurality of fibers 111 and 121 and an electronic control device 170. Each of the fibers 111 and 121 is used for emitting light to the corresponding interferometer 110 and 120 or for receiving the light from the corresponding interferometer 110 and 120. The electronic control device 170 monitors an absolute displacement of the first object with respect to a second object based on the information from at least one of the interferometers 110 and 120. <P>COPYRIGHT: (C)2013,JPO&INPIT |
