| 摘要 |
<p>The image formation system (10) of the invention provides a compact apparatus for viewing indicia (14) on a planar mirror-like (specular) substrate (12), such as a semiconductor wafer. The invention is particularly effective in viewing indicia (14) that require either brightfield or high-angle darkfield illumination. These and other benefits of the invention are provided in part by providing selective directional focusing and defocusing of the reflected image of the illumination elements that illuminate the indicia (14), while providing substantial focusing of the image of the indicia at high contrast. In the case of high-angle darkfield illumination, directionally selective focusing maximizes useful darkfield area by minimizing interference between the reflected image of the illumination sources and the image of the indicia (14), while the contrast of the image of the indicia (14) is maximized.</p> |
