| 摘要 |
For producing fine printing patterns on large serigraphical printing frames it is possible to apply an exposure through correspondingly large film areas, but it is cheaper to make use of a successive line-by-line exposure with the use of a modulated light or laser beam, which is caused to sweep across an emulsion coated printing frame surface from an oscillating deflection mirror. The beam (20), in its outermost positions, will be directed obliquely towards the surface (14), and if the latter changes its distance from the oscillating mirror (48) the exposure lines (16) will thus be correspondingly shorter or longer, whereby the printing pattern may be distorted. According to the invention this can be counteracted by the light ray being brought to pass a lense bar (56) mounted just in front of the line of exposure and adapted so as to deflect, all along the line, the light beam such that it will hit the surface perpendicularly, whereby the length or the lines will be independent of occurring distance variations. The width of the lense bar (56) should be at least twice the line width, as the invention also provides for a transverse displacement of the light beam for achieving that the latter may be delivered from a resonance oscillating goniometer mirror (48) with a high operational speed without overlappings occurring between the consecutive lines of exposure.
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