PURPOSE: To detect and adjust various kinds of relative deviations of first and second exposing units by detecting the picture light of a test pattern illuminated by the second exposing unit of a pattern illuminating means.
CONSTITUTION: When the pattern forming means of a CPU, etc., forms the pattern on a photosensitive drum 11 by a laser scanner 13, the pattern illuminating means of a head driver, etc., drives an LED in the vicinity of one end of a line head 16 at prescribed timing, so that the LED of the line head 16 illuminates the passing test pattern. Then. elapsed time from timing that the laser scanner 13 completes the formation of the test pattern to the timing that a photosensor 48 detects the test pattern is measured by a subscanning deviation detecting means of the CPU, etc., and the relative error in an exposing position in a subscanning direction between the laser scanner 13 and the line head 16 with respect to the face to be scanned of the photosensitive drum 11 is detected to adjust the operational timing of the laser scanner 13 with the line head 16.
MAMA TAKASHI
SANADA KEIICHI
