| 摘要 |
PROBLEM TO BE SOLVED: To provide an imaging lens for a capsule type endoscope which achieves sufficient corrections in magnification chromatic aberrations and distortion and is compact while being a wide-angle lens. SOLUTION: The imaging lens 21 forms an image of light from a spherical subject 13 on an imaging surface of a planar image pickup device and comprises a first lens L1 having negative refractive power, an aperture diaphragm S6, a second lens L2 having positive (or negative) refractive power, a third lens L3 having positive refractive power, and a fourth lens L4 having positive refractive power. A shape of the distal end of a capsule 12 and a cover glass 18 of the image pickup device 17 are taken into consideration in shapes and arrangements of the lenses L1-L4 and the aperture diaphragm S6 constituting the imaging lens 21, and the first lens L1, wherein the aperture diaphragm S6, the second lens L2, the third lens L3, and the fourth lens L4 are disposed in this order from the side of the subject 13. COPYRIGHT: (C)2010,JPO&INPIT
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