| 摘要 |
PROBLEM TO BE SOLVED: To provide a printing image writing method which is capable performing focused exposure and latent image formation by activating an autofocusing mechanism to correct the mechanism by as much as a fluctuation component of the distance between a roll for plate making and a semiconductor laser head by swingy rotation of the roll for plate making. SOLUTION: The roll for plate making is coated with a photosensitive film containing a coloring matter which allows a latent image to be written in response to a laser of a first specific wavelength and absorbs the laser of a second specific wavelength. This roll for plate making is chucked at both ends and is rotated. The semiconductor laser head with an autofocusing function to radiate the lasers of the first and second specific wavelengths is brought near to the roll for plate making and while the laser beam head is moved from one end to the other, the laser of the first specific wavelength is flickered to write the latent image. The laser of the second specific wavelength is then radiated and the autofocusing mechanism is activated to be corrected by as much as the fluctuation component of the distance by the swingy rotation of the roll for plate making in such a manner that the distance from the surface of the photosensitive film to the semiconductor laser head is kept constant.
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