| 摘要 |
<p>Magnification correction for small field scanning of large blanks is provided by adding magnification adjusting elements (lenses 712, 714, 722, 724) to a double pass Wynne-Dyson lens (770) or other type of one-to-one projection lens. The magnification adjusting optical elements include two pairs (710, 720) of low power lenses, one associated with each of the input and output prisms (731, 732) of a Wynne-Dyson lens. Movement of the magnification adjusting optics provides positive or negative magnification as needed to correct for any expansion or compaction of the blank (160) relative to the reticle (120) and hence maintain alignment. Further magnification correction is provided by a small velocity relative movement between reticle (120) and blank (160) by means of a secondary stage in the scan direction. This corrects for any alignment error in the scan direction and may be used independently of the optical correction technique with any type of projection lens.</p> |
