| 摘要 |
<p>Illumination apparatus includes a light source (10) which directs a polarized source beam (16) in a downstream direction along an optical axis and desirably focuses the beam. A polarization-altering element (20) downstream from the source alters the polarization in a portion or portions of the source beam, so that the altered beam (24) includes portions (23, 25) having different polarization directions. The altered beam passes downstream through a polarization-selective filter (28). The output beam (30) from the polarization-selective filter can include either portion depending on the orientation of the filter. The arrangement can be used to provide a spot of a given size and shape at the focal location (18) in a scanner such as a bar code scanner. The size and depth of field of the spot can be varied dynamically during operation.</p> |
