| 摘要 |
<p>38/SO1535 S82P5 A device for detecting, on a record medium, positions of interband regions disposed between bands of recorded formation on the medium, detects differences in reflectivity of the regions and the bands by emitting electromagnetic radiation to be incident on a recorded surface of the medium containing the bands and regions, and detecting the level of the radiation reflected thereby. radiation source, such as an LED, emits a beam of radiation to be incident on the medium. A detector, such as a photo transistor, detects the intensity of the beam reflected from the medium and provides an output level that varies with the intensity of the reflected beam. An interband region detecting circuit provides an output signal in response to variations in the output level to indicate the presence of the interband regions. In order to automatically control the current furnished to the radiation source so that the intensity of the reflected beam is maintained within an optimum range of the detector, an average level detecting circuit, which can include an integrator, provides a time average of the detector output to a current control circuit whose output is connected to the radiation source. Thus the emitted level of radiation from the source is automatically increased if the record medium has a low reflectivity, and is automatically decreased if the record medium has a high reflectivity.</p> |
