| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an eyepiece that has a long eye relief, excellent characteristics over a wide field, and a large incident pupil diameter and is small in size, light in weight, and suitable for use in a night vision device. <P>SOLUTION: An eyepiece 1 has a three-group, three-lens configuration including a first lens 11, a second lens 12, and a third lens 13, which are arranged in order from the pupil side. The first lens 11 is a convex lens made of glass and has such a refractive power that 0.3<f/f<SB POS="POST">1</SB><1 is satisfied, where f is the focal length of the entire system, and f<SB POS="POST">1</SB>is the focal length of the first lens. The first lens 11 has a refractive index n<SB POS="POST">1</SB>that satisfies n<SB POS="POST">1</SB>>1.75. At least three surfaces among the first to sixth surfaces 21-26 of the first to third lenses 11-13 are aspheric surfaces. At least one surface among the third to sixth surfaces 23-26 of the second and third lenses 12, 13 is a diffraction optical surface. <P>COPYRIGHT: (C)2013,JPO&INPIT |
