Fingerprint Sensor based on Optical Characteristics Inside a Finger
Fingerprint has been widely used as the method to realize personal authentication because it has the best balance among authentication performance, cost, size of device, and ease of use. However, conventional fingerprint sensors have some problems; quality of the fingerprint pattern is sometimes not so good due to the condition of a finger surface such as moisture or wrinkles. These problems are caused by the principle of the sensors. Most of fingerprint sensors detect a fingerprint pattern from the presence/absence of the convexities and concavities of a finger surface. To solve these problems, we devised a new kind of fingerprint sensor, which detects a fingerprint pattern through the use of optical characteristics inside a finger. This method is based on a new scientific discovery that there is layer of skin inside a finger that has a transmittance distribution corresponding to the pattern of concavities and convexities of a finger surface. Therefore, it can detect stable fingerprint images at all times regardless of finger surface conditions (wet, wrinkles). In this paper, we describe the principle of a new type of fingerprint sensor and demonstrate the effectiveness of the proposed sensor by using some examples.