1. Field of the Invention
The present invention relates to a multibeam recording apparatus for irradiating a plurality of light beams onto a recording surface.
2. Description of the Background Art
FIG. 17 is a view of a conventional multibeam recording apparatus. The multibeam recording apparatus is comprised of a light source unit 90 in which a plurality of light source parts 91 are arranged in a predetermined arrangement pattern, and a reduction optical system (imaging optical system) 92 for reducing a plurality of light beams from the light source unit 90 and irradiating the reduced light beams onto a photosensitive material (recording surface) PM.
Each light source part 91 comprises a semiconductor laser 93 and a collimating lens 94 which are fixed to the main body of the light source part (not shown). A light beam from the semiconductor laser 93 is collimated into a parallel light beam by the collimating lens 94 to be thereafter emitted from a tip portion of the main body of the light source part (which is generally indicated at 95 in FIG. 1) toward the reduction optical system 92. Here, the tip portion 95 of the main body of the light source part functions as an aperture which cuts an unwanted portion of the parallel light beam.
The reduction optical system 92 is comprised of a plurality of optical elements. For example, as shown in FIG. 1, receiving parallel light beams which travel parallel to an optical axis Z from the light source parts 91 and which have at predetermined pitches P, the reduction optical system 92 reduces the light beams at an appropriate magnification M and irradiates parallel light beams which have beam pitches BP (=P.multidot.M) and which advance parallel to the optical axis Z onto the photosensitive material PM.
Hence, by moving the photosensitive material PM in a primary scanning direction X (which is perpendicular to the plane of FIG. 17) while step feeding the light source unit 90 and the reduction optical system 92 in a sub scanning direction Y, a two-dimensional image is recorded on the photosensitive material PM.
If high quality recording of a predetermined image using the multibeam recording apparatus having such a construction above is desired, the light beams from the respective light source parts 91 must travel parallel to the optical axis Z of the reduction optical system 92 and the light source parts 91 must be arranged with equal distances from each other (i.e., constant pitches P). If these requirements are not satisfied, light beam spots will not be formed equidistant from each other on the photosensitive material PM, resulting in a varied quality image recorded on the photosensitive material PM.
For this reason, in the conventional multibeam recording apparatus, the direction of the light beams from the respective light source parts 91 must be adjusted and the light source parts 91 must be arranged with a high accuracy in a predetermined arrangement pattern (with constant pitches P in the example described above), which requires a long time.