Original Publication Date: 1976-May-01
Included in the Prior Art Database: 2005-Mar-02
As shown in Fig. 1, a revolving mirror 3 scans the medium 5 to be impressed with an image, directing coherent light beams from sources 7, across the medium 5. Density of the light beams is modulated to produce light and dark areas.
As shown in Fig. 1, a revolving mirror 3 scans the medium 5 to be impressed
with an image, directing coherent light beams from sources 7, across the medium
5. Density of the light beams is modulated to produce light and dark areas.
Mirror 3 consists of multiple tracks, one track for each modulated light beam to be scanned across the recording medium 5. Each track mirror surface spirals inward around the circumference, i.e., the dimension at any point on the radius is equal to R-K, where R is the radius at the start of the spiral and K increases linearly from zero to the maximum value needed to fully deflect the light beam, as shown in Fig. 2a.
Each track mirror surface is also set at an angle which varies from zero degrees at the start of horizontal sweep to a maximum number of degrees, determined by the amount of vertical deflection needed to compensate for vertical movement of the recording medium 5, as shown in Fig. 2b. This angle will vary linearly from zero degrees at the dead band around the circumference to a maximum value upon reaching the dead band again.
A number of laser beams (coherent light sources 7) are directed at the rotating mirror 3, one for each track. The number of tracks depends on the amount of information to be recorded on one sweep. The sweeps will start on one side of the dead band, and be deflected across the recording medium 5 by the changing radius of the mirror track as it rotates. The beam will also be deflected a smal...