| 摘要 |
PURPOSE:To prevent the nonuniformity of a line width and concentration from being generated by measuring the surface inclination error of a polygon-mirror and determining laser exposure quantity, which is given to beam tracks to be scanned, from the error. CONSTITUTION:The center of a photo-detecting part 1 is not on a beam locus 2 as conventional one but at a position to be separated only by a distance yo (yo<rc, rc: detecting distance). An analog output from the photo-detecting part 1 is binarized by a comparator 3 and the binary signal of a pulse shape is inputted to an error calculating circuit 5. Then, by the time and width of an input pulse, the surface inclination error of the polygon mirror is calculated. Thus, exact correction can be executed and satisfactory picture quantity can be obtained. |
