| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide an optical system that suppresses the deterioration of imaging performance, in the optical system and can simultaneously observe a front object and a substantially-lateral object. <P>SOLUTION: A first lens group having a negative refractive power, a second lens group including a reflective-refractive lens, and a third lens group having an aperture diaphragm and positive refractive power are arranged sequentially from the front object side. The reflective-refractive lens has a first surface formed at the front object side, a second surface formed at an image side, and a third surface formed on the entire peripheral surface between the first surface and the second surface. The first surface has a first transmission surface formed around the optical axis and a first reflection surface that faces the image side and is formed around the first transmission surface. The first surface is defined by an aspherical surface having a concave shape in the vicinity of the optical axis and a convex shape in the vicinity of the first reflection surface. The second surface has a second transmission surface formed around the optical axis and a second reflection surface that faces the front object side and is formed around the second transmission surface. The third surface is a transmission surface. <P>COPYRIGHT: (C)2011,JPO&INPIT</p> |
