Patent ID: 6941002

Claim:
A fingerprint reading device comprising: an active matrix liquid crystal cell having a front surface and a rear surface opposing the front surface; an illumination source for projecting a light from the rear surface to the front surface of the active matrix liquid crystal cell; a light guiding plate on the front surface of the active matrix liquid crystal cell for transmitting the light projected through the active matrix liquid crystal cell to a person's finger in contact with a front surface of the light guiding plate and light reflected from the finger is transmitted into the light guiding plate and reflected from a rear surface of the light guiding plate toward a side end surface of the light guiding plate, light receiving means on the side end surface of the light guiding plate for receiving the reflected light exiting from the side end surface of the light guiding plate; and a drive circuit for driving the active matrix liquid crystal cell to pinpoint-irradiate a fingerprint of the finger in contact with the light guiding plate by pinpointing with the light emitted from the illumination source and causing the light receiving means to pinpoint-receive the light reflected by the fingerprint to thereby obtain an image of the fingerprint.