| 摘要 |
PROBLEM TO BE SOLVED: To provide an imaging lens for a capsule endoscope improved in distortion. SOLUTION: The capsule endoscope has the imaging lens 45a to form the image of a substantially spherical subject 40 in a plane shape on an imaging surface. The imaging lens 45a is composed of first-fourth lenses L1-L4 and an aperture diaphragm S7. Their surface shapes and the arrangement thereof are in consideration of a front cover 41 of the capsule endoscope and a glass cover 56 of an imaging device. The imaging lens is configured to satisfy the expression: 0.7<(Y(ω+Δω)-Y(ω))/Y(Δω) for an optionally selected half-angleωwhen the image height relative to the half angleωis Y(ω) and the quantity of minute change of the half angleωisΔω. COPYRIGHT: (C)2009,JPO&INPIT
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