| 摘要 |
PURPOSE:To arrange an optical member for lighting even when the distance to an object image is shortened by installing an image formation optical system where lens elements which have a refractive index distribution depending upon not only the distance from an optical axis, but also the distance in the optical- axis direction are arrayed. CONSTITUTION:The refractive index distribution of a lens 11 is nearly proportional to the square of the distance (r) from the optical axis in an optional cross section perpendicular to the optical axis and also varies monotonously depending upon the distance (x) measured from the front end surface S1 of the lens 11 in the optical-axis direction. The use of this lens makes the distance l0 between the object 2 and the front end surface S1 of the lens larger than the distance l1 between the rear end surface S2 of the lens 1 and an erect image 3 of life size of the object 2. Therefore, the object image distance is shortened while lighting optical systems 21 and 22 are unchanged in arrangement, and a thin type device is obtained.
|
