PURPOSE: To make the position adjustment of a line sensor easy by setting the width of an aperture and the distance thereof from two re-image-forming lenses in such a way that the images of the aperture on the line sensor by said lenses overlap in the blurred part at the end.
CONSTITUTION: Re-image-forming lenses 8, 10 form the focusing image of an intended focal plane 4 on a line sensor surface C. The images 21A, 21B of an aperture 20 in the position nearer the lenses 8, 10 than the plane 4 are the out- of-focus images which are blurred at the edges. The width (x) and distance L of the apeture 20 are so set that the two images 21A, 21B overlap at the blurred part (e) at the end. A peak P of illuminance is formed at the part (e). When the center of the aperture 20 is in an optical axis 18, the peak P is also formed on the optical axis 18 and therefore the position of the line sensor is accurately and easily determined by moving the line sensor in the arranging direction of cells in such a way that the suitable cell in the line sensor, for example, the cell of a central address, emits the max. output.
MUKAI HIROSHI
KAWAMURA KUNIO
