| 摘要 |
PURPOSE:To know the optimum magnification of a semiconductor laser having astigmatic difference without correction of astigmatic difference by an optical system by disposing an image forming lens under the specific conditions with respect to the longitudinal direction of the semiconductor laser. CONSTITUTION:When the emission end face of a semiconductor laser is put approximately at the front side focal plane f1 of a condensing lens 6a and an image forming face 7 is put in the rear side focal position f2 of the image forming lens 6a, the longitudinal exit beam of the semiconductor laser images on the image forming face 7 as an approximate beam west because its diversion origin positions near the emission end face. On the other hand, the exit light in the transverse direction images on the image forming plane 7 without becomong beam west because its diversion origin is in the position away from the end face and the correction of astigmatic difference. As is not done for the lens system, thus the magnification beta of the conjugate face of the laser end face and the recording face is expressed by formula I. Here, F2 denotes the F number of the image forming lens and constant gamma 2. Hence, if the values of f1, f2 in the optical system are suitably set, the optimum magnification of the semiconductor layser may be known.
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