| 摘要 |
PROBLEM TO BE SOLVED: To intensify the light intensity of a fingerprint image which is formed on an image formation plane, without intensifying the light intensity of a light source and to drastically suppress the occurrence of trapezoidal distortions under the condition of restrained out-of-focus image. SOLUTION: A lens that has a barrel distortion aberration is used as a lens 3-4. In this case, the central axis LC of the lens 3-4 is tilted to a B side on a fingerprint collecting plane A-B only by justθ1 with respect to an optical axis LO shown in Figure (a). Inclination with respect to the axis LO of an image forming plane a-b is adjusted so that out-of-focusing does not occur. When a lens that has pin-cushion distortion aberration is used as the lens 3-4, the axis LC of the lens 3-4 is tilted towards the A side on the plane A-B just byθ2 with respect to the axis LO as shown in Figure (b).
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