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With most finger-scan devices, the user's finger is placed on a reader that takes a picture of the fingerprint.
Finger-scan imaging may use optical, thermal, tactile, capacitance, or ultra-sound techniques.
- For optical images, users typically place a finger on a glass plate and the impression made by the finger is captured.
- For tactile or thermal images, the user places a finger on a pressure or temperature sensor.
- Capacitance silicon sensors measure electrical charges and give electrical signals corresponding to ridges and valleys on the fingertip.
- For ultrasound images, sound waves detect the finger patterns.
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