| 摘要 |
<p>A high resolution light pen is disclosed for use with graphic displays and more particularly, a light pen (10) having a collimation tube (22) slidably mounted within a housing (20). The collimation tube includes an axially extending channel (38) having a non-reflective surface. A photodetector (30) is fixably mounted within the housing aligned with the channel. A lens (42) is mounted adjacent the front end of the channel and has a focal length equal to the spacing between the lens and an aligned pixel (P2) of the video screen. By this arrangement, all light rays emanating from an aligned pixel and passing through the lens are refracted axially along the channel and directed to the photodetector thereby maximizing the input thereto. The light pen further includes a discrimination circuit which generates an interrupt signals for reading an address counter. The discrimination circuit generates an interrupt signal when the signal from the photodetector is valid. The interrupt signal is generated at a time which is substantially independent of the amplitude and slope of the signals thereby reducing the effects ofjitter.</p> |
