fingerprint time clock through the special photoelectric
Posted Nov 16 2012 1:35am
fingerprint time clock through the special photoelectric conversion equipment and computer image processing technology, the living fingerprint acquisition, analysis and comparison, we can quickly and accurately identify the personal identity. General system mainly includes the fingerprint image acquisition, fingerprint image processing, feature extraction, feature value of the comparison and matching process. Modern electronic integrated manufacturing technology makes the fingerprint image reading and processing equipment miniaturization, and at the same time, the rapid development of the personal computer arithmetic speed provides in the single computer and even can fingerprint than the possibility of operation, and good fingerprint processing and matching algorithm to ensure the accuracy of the results.
Automatic time and attendance systems technology is from science fiction and Hollywood movie into our real life, maybe one day, you don't have to carry that a bunch of keys, just a click of the fingers, the door will open; Also don't have to remember that annoying password, using fingerprint can drawings, computer login. Believe this one day, not too far away.
Optical take like fingerprint time clock equipment has the long history, can be traced back to the 1970 s. Optical take like equipment based on the light's total reflection principle (FTIR). The light to pressure have fingerprint glass surface, reflex the light by CCD to get, and the amount of reflected light depends on the pressure in the glass surface fingerprint ridge and depth and skin and glass between oil and water. Light through glass shot to the valley after the place in the glass and air interface happen total reflection, the light is reflected to the CCD, and into ridge light does not occur total reflection, but by ridge and glass contact surface absorption or diffuse to other places, so in the CCD is formed on the fingerprint image.
Fingerprint is just a small part of the human body skin, but it contains a large amount of biometric time clock information. Fingerprint features can be divided into two categories: general characteristics and local characteristics. General characteristics of those employing eye can be directly observed characteristics, including basic grain design, pattern area, it, triangulation point, style line and grain number, etc. Capacitance sensor is according to the fingerprint ridge and valley and semiconductor capacitance induction grain to form the capacitance value size to differ, to decide what position is ridge what position is valley. When a finger contact to semiconductor capacitive fingerprint on the surface, because the ridge is outstanding valley is concave, according to the capacitance value and interval relations, will be in the ridge and valley place form different capacitance value. The working process of each pixel point is through the capacitance induction particle precharge to a reference voltage. According to the discharge rate is different, can detect ridge and valley position, so as to form the fingerprint image data.