| 摘要 |
A beam position sensor for a beam scanner is disclosed for use in a laser printer. The printer comprises three diode lasers each of which emits at a different wavelength. The beams from the three lasers are combined by the use of dichroic plates to form one combined beam. The combined beam is scanned onto a receiving medium by a polygon. The beam position sensor of the present invention is adapted to sense the position of the polygon in order to provide a synchronizing signal which will insure that each raster line in the printer is started at the proper position. The beam position sensor includes a diode laser and optics for projecting a beam from the laser onto the polygon. The beam is reflected back from the polygon into a photodetector which effects the start of a new raster line at the appropriate time. In order to minimize the number of optical elements in the beam position sensor and to simplify the device, the diode laser and the photodetector are located along the same optical axis.
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