| 摘要 |
PURPOSE:To provide the clear fingerprint picture by reducing the scattered light on the prism surface of a triangular prism and increasing the contrast of light to be reflected on the side of a camera. CONSTITUTION:A triangular prism 11 is provided with a pair of electrodes 12a and 12b on a prism surface 11a. An interface active thin film layer 18 is formed on the prism surface 11a. An ultrasonic humidifier 16 sprinkles a water solution S housed in a tank 17 on the prism surface 11a. The water solution S is mixed with the interface active agent. A controller 13 detects resistance R of the prism surface 11a by a pair of electrodes 12a and 12b. By driving and controlling the ultrasonic humidifier 16 so as to keep the resistance value R within the prescribed range, a width (d) of a water film 19 is controlled to be within the prescribed width range. Thus, the prism surface 11a is properly humidified and the fingerprint pattern can be surely and accurately detected even by dried fingers. Thus, the high-contrast fingerprint picture can be inputted. |
