| 摘要 |
PURPOSE: A level system is provided to reduce a level error by using zoom lens. CONSTITUTION: An level system comprises a light emitting part(130) and a light receiving part(160). In the light emitting part, a light source(141,151) emits a light to a wafer(110) and a lens(120). Only a straight component among lights radiated from the light source is filtered by a first grating(143,144,153,154). The light image filtered by the first grating is adjusted to an area size to be exposed by a zoom element(145,155). The path of the adjusted light is controlled by an offset plan plate(147,157) so as to be incident on the area to be exposed. In the light receiving part, the controlled light image is adjusted to the first grating size by a zoom element(177,187). The adjusted reflected light is once more filtered by a second grating(172,173,182,183). The luminous intensity of the filtered reflected light is detected by a detecting unit(175,185).
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