| 摘要 |
PURPOSE:To make it possible to detect and correct the amount of optical distortion of a reducing projection type lens, by processing images, which are projected on the matrix of a charge coupled device (C.C.D). CONSTITUTION:A reducing projection type lens 2 is arranged directly over a wafer stage 4. A reticle 1 is provided over the lens 2. Measuring marks are attached to the four corners of the reticle 1 around a required circuit pattern. A C.C.D 3 for detecting the amount of lens distortion is supported on the wafer stage 4 so that the device 3 can be detached and attached beneath the lens 2. The C.C.D 3 has a matrix grid for transferring the measuring marks. The positions of the projected images of the measuring marks, which are transferred on the matrix grid, are compared with the positions of the ideal projection images of the measuring marks set on the matrix surface. The amount of the distortion of the lens 2 is detected on the basis of the amount of the deviation in said comparison. |
