| 摘要 |
PURPOSE: An apparatus for measuring a flatness of a substrate is provided to solve the inaccuracy of the measurement resulted from the time unbalance of a lamp and the spatial nonuniformity of a light incident on a substrate. CONSTITUTION: The apparatus(100) includes a light source(102), a source lens(104), a source stop(106), a beam splitter(108), a field lens(110a,110b), a substrate(112), a projection stop(114), a projection lens(116), a charge coupled device(18), a general purpose interface bus(GPIB) board(120), a computer(122), a chopper(124), a reference mirror(126) and a mirror(128). The light source is a halogen metal lamp and emits a long wavelength infrared(LWIR) light or a ultraviolet(UV) light. The source lens converges a light from the lamp. The source stop(106) is an optically opaque material and has an aperture to pass the light. The source stop(106) determines the intensity of the light forming an image. The beam splitter splits the light into the first light and the second light, and the fist light is incident on the reference mirror, and the second light is incident on the substrate. The chopper modulates the first and the second light, and removes the temporal nonuniformity of the light intensity by modulating the light intensity of the lamp.
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