| 摘要 |
Image setting apparatus is disclosed for producing two-dimensional images on photosensitive material. The apparatus includes a device for transporting the photosensitive material past an imaging line to provide a first dimension of the two-dimensional image; a light source for producing a modulated beam of light; a scanning device for converting the light beam into a scanning beam; and a scan lens in the path of the scanning beam such that a focused beam spot moves linearly and repeatedly across the photosensitive material along the imaging line to provide the other dimension of the two-dimensional image. According to the invention, the device for transporting the photosensitive material past the imaging line includes a driving roller in contact with the photosensitive material, a stepper motor mechanically coupled to rotate the driving roller and a controllable circuit, connected to the coil of the stepper motor, for incrementing the motor in microsteps upon command. The current through the motor coils is so controlled that the stepper motor may be advanced at least two thousand substantially equal microsteps per revolution, thereby permitting correction of small repeatable errors in the advance of the photosensitive material and permitting the motor to be advanced in accordance with any desired image resolution.
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