| 摘要 |
<p>An illumination system (10, 40, 74, 100) is provided having one or more light sources (24, 26), opaque baffles (30, 32), and mirrors (50, 64, 66) for illuminating indicia on a substrate, such as a semiconductor wafer (18), for viewing by a camera (12, 42) aligned parallel to or at an angle (14) to the substrate. The light sources (24, 26) include light emitting diodes for illuminating soft marks and broad spectrum incandescent lamps for illuminating hard marks. Dark field and light field illuminators are provided for enhanced reading of light indicia on a dark background and dark indicia on a light background, respectively. A light control unit (158) allows for manual or automated control of light source selection and light intensity. Opposing mirrors extending along the optical paths of the light sources reflect light emitted from the light sources into the camera's field of view, thereby increasing the illumination efficiency and permitting the use of fewer light sources.</p> |
