摘要 |
In an electronic image printing apparatus of the type in which a light sensitive image recording layer is exposed by a light beam, an apparatus is provided for determining and controlling the position of the light beam which comprises one or two alternating pluralities of diffraction grating patterns disposed in a corresponding relationship with at least a portion of the light sensitive image recording layer to produce a diffraction grid which when irradiated by the light beam provides a diffracted beam which is representative of the position of the light beam on the diffraction grid. The position of the diffracted beam is detected to provide the requisite signal for controlling the position of the light beam.
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