| 摘要 |
PURPOSE:To obtain a fingerprint detector in which a distortion can not be generated by forming so that the outgoing angle of a light beam from a fingerprint inspection face to an image formation face of an optical system on the fingerprint inspection face is more than the critical angle of the first lens. CONSTITUTION:The center of curvature of each face of lens 1 and 2 is on the same optical axis 9, which is different from a prism, so that the trapezoidal distortion can not be generated at the fingerprint detector. And also, the outgoing angle theta of the light beam from a fingerprint inspection face 3 to an image formation face 4 is more than the critical angle, so that a shading plate 7 can be seen from the image formation face 4 in the direction of a non-contact part 11a of the fingerprint, and therefore the direction can be seen dark. On the other hand, a light beam 6b outgoing from a light source 8 with which the fingerprint inspection face 3 is irradiated reaches the image formation face 4 after an irregular reflection on a contact part 11b of the fingerprint, so that the direction of the contact part 11b can be seen bright from the image formation face 4. Thus, the fingerprint can be detected without generating the distortion, or being affected by any disturbance due to an outside light. |
