| 摘要 |
PURPOSE:To enable light projection and light reception with defocusing without being affected by an object distance by making the surface of a 2nd lens on an image plane side aspherical and specifying its shape. CONSTITUTION:This system consists of a 1st positive meniscus lens which is a biconvex or positive lens having its large-curvature convex surface on an object side and a 2nd positive or negative meniscus lens which has its convex surface on the object side in order from the object and at least the image plane side of the 2nd lens is made aspherical; when the system is in a shape of a rotary body shown by an equation I, inequalities II-V hold. In the inequalities I-V, Z is the distance from the peak point of the aspherical surface in the optical-axis direction, (h) the perpendicular distance from the optical axis, (r) the radius of paraxial curvature, (k) a cone constant, a1, a2, a3... aspherical surface coefficients of 4th order, 6th order, 8th order ..., (f) the focal length of the whole system, f1 and f2 the focal lengths of the 1st and 2nd lenses, d1 and d3 the on-axis thicknesses, d2 the air gap, n1 and n2 the refractive indexes, and r4 the radius of paraxial curvature of the 2nd lens on the image plane side. Consequently, the defocusing is reduced. |
