| 摘要 |
A light beam scanning optical apparatus is provided which simultaneously converges a plurality of light beams on different locations in a scanning surface and thereby simultaneously writes a plurality of lines in one scanning operation. The light beam scanning optical apparatus comprises a light source having three or more light emitting points, and a converging lens which shapes light beams emitted from the light source, into generally parallel or convergent bundles of rays. The converging lens has a shape generally symmetrical with respect to the optical axis, and the light emitting points on the light source are disposed on a circle having its center generally on the optical axis. Alternatively, the light source comprises a first light source having one light emitting point, a second light source having a plurality of light emitting points, and a light beam coupling device for unifying the directions of travel of light beams emitted from the first and second light sources. Scanning with light beams of which the number is n and which have been emitted from the light source is simultaneously performed at unequal intervals with respect to the direction of sub scanning on the scanning surface, and then the following relational expressions hold:hi mod n NOTEQUAL 0hi mod n NOTEQUAL hj mod n(2</=i</=n, 2</=j</=n, i NOTEQUAL j)wherein hk (2</=k</=n) is the position where the kth light beam from the front extremity of an image is condensed, which position is measured with respect to the position where the first light beam from the front extremity of the image is converged on the scanning surface, and which position is expressed in units of the interval between scanning lines required by a given image density on the scanning surface, and wherein mod is an operator for finding the remainder in the case that hi or hj is divided by n.
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