| 摘要 |
PURPOSE:To attain reading with high accuracy by providing a beam splitter between a collimate lens and a laser diode to minimize the lateral aberration. CONSTITUTION:The beam splitter 12 is provided between the collimatelens 11 and the laser diode 2, and the collimate lens 11 consists of a convex lens 11a being a flat convex lens, a biconvex lens or a positive meniscus lens (in figure, a flat convex lens is shown), and a positive meniscus lens 11b positioned to the side of the laser diode 2 and whose concaved face is directed to the side of the laser diode 2, and conditions of Equations I, II are satisfied, where f1 is a focus of the convex lens 11a forming the collimate lens 11, r3 is the radius of curvature of the convexed plane of the meniscus lens 11b, d2 is a distance between the convex lens 11a and the meniscus lens 11b and (f) is the total focus. |
