The finger print recognition system null which uses the living body detection device and the said

摘要

PURPOSE:To instantaneously detect a living body by detecting the size of a formed image or whether or not the center of an area where reflection and scattering of light take place is displaced from the center position of a part irradiated with the light. CONSTITUTION:A light source 1 and light condensing optical system 2 which condenses an optical beam L1 and project the beam L1 condensed to a spot on the surface of an object 5 to be detected are provided. In addition, an image forming optical system 3 which condenses the rays of light L2 reflected or scattered by the section irradiated with the optical beam L1 and forms an image at a prescribed position and a light detecting means 4 which detects the size of the image of the irradiated part and outputs a light detecting signal J1 indicating the size of the detected image are also provided. Whether or the object to be detected is a living body is discriminated based on the detecting signal outputted from the means 4. When the image forming optical system 3 is constituted so that the point irradiated with light can become an object point in such way, the size of the formed image varies between an object of a living body and another object of a nonliving body, since the size of the object point varies between a living body and nonliving body. Therefore, whether or not an object to be inspected is a living body can be discriminated instantaneously irrespective of the conditions of the object.