Patent ID: 7817256

Claim:
A personal authentication method comprising imaging, on an image sensor as a laser speckle using an optical system, light reflected from a blood vessel layer in subcutaneous and internal tissues when a laser beam is expanded and made to irradiate a finger pad, calculating a quantity that represents the rate of change with respect to time of the amount of light received for each pixel of the laser speckle, obtaining a finger pad blood flow map as a two-dimensional map of the numerical values, and comparison-checking the blood flow map against pre-registered data of individuals, wherein using a near-infrared laser beam, which can reach the internal tissue of the finger pad, and a visible laser beam, which is easily absorbed by the subcutaneous stratum corneum, finger pad blood flow maps obtained from the respective reflected lights are measured at the same time or in sequence, and the two types of blood flow maps thus obtained are comparison-checked against pre-registered data of individuals.