| 摘要 |
A beam converting optical system is provided which is easy to position the optical elements, which has a comparatively short total length, and which has good aberration correction. A beam converting optical system converts light beams with an oval cross-sectional shape into parallel light beams with a substantially circular cross-sectional shape. A converting lens is provided which has at least one surface that is cylindrical. The horizontal cross section of the cylindrical surface of the converting lens is essentially non-circular. The converting lens may consist of two similar elliptic cylinder surfaces. The two ellipses are of the shape of a horizontal cross section of the two elliptic cylinder surfaces and have the same focal point. The two elliptic cylinder surfaces of the converting lens have concave surfaces facing toward the incident light beams
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