| 摘要 |
<p>A masking device (40) is provided for use with projectors (10), such as overhead projectors, to selectively block the projection beam that carries an image disposed on a substrate, such as a transparency (16), for projection onto a screen. The masking device (40) has a framework having guide rails (44, 46) that form slideways receiving a shutter panel (90). A transparency (16) is aligned by the guide rails. The shutter panel (90) has a leading edge that extends transversely across the aligned transparency (16) so that only the image portion (20) forward of the leading edge is projected. The shutter panel (90) is constructed of a material that inhibits the projection beam, but allows the user to view the blocked image (20). A base plate (42) supports the guide rails and provides a stage on which the transparency may be positioned for projection of the image. The masking device (40) adjustably mounts (52, 62) on various projectors, but the device could be integrally with the projector (10).</p> |
