Image Acquisition Technologies

image aqImage Acquisition Technologies are optical detectors utilized to deliver the highest quality image possible for Precision Biometrics.

Forms of IAT suitable for fingerprint scanners are:

  • Optical
  • Capacitive
  • Thermal
  • RF

Optical Sensors

  • This type of sensor has limitations in imaging unclean fingers.
  • Optical fingerprint imaging involves capturing a digital image of the fingerprint using visible light.
  • In simple terms, this type of sensor is, just a specialized digital camera. This type of sensor has limitations in imaging a unclean skin of the finger. In addition, it is relatively easy to circumvent this sensor.

Capacitive Sensors

  • Capacitive Sensors use the principles of Capacitance to form an image of the fingerprint patterns on the dermal layer of skin. Each sensor pixel is used to measure the capacitance at that point of the array.
  • The capacitance varies between the ridges and valleys of the fingerprint due to the fact that the volume between the dermal layer and sensing element in valleys contains an air gap.
  • The measured capacitance values are then used to distinguish between fingerprint ridges and valleys.

RF Sensors

  • RF sensors make use of the principles of medical ultrasonography to create visual images of the fingerprint.
  • The sound waves are generated using piezoelectric transducers and reflected energy is also measured using piezoelectric materials.
  • Since the dermal skin layer exhibits the same characteristic pattern of the fingerprint,unlike optical sensors, RF sensors can work well even if finger skin is not very clean.

Thermal Sensors

  • Thermal Sensors are made out of pyroelectric materials, which change their electrical property according to the temperature.
  • A pixel array is formed using these materials, which sense the heat at all points of the finger. The heat at the ridge will be that of the body temperature, with the same at the valley will be the atmospheric temperature of the air.
  • The temperature difference is used to differentiate between the peak and the valley of the fingerprint. This is measured at very high resolution as each sensor pixel is as tiny as 50 micron X 50 micron. A 3D image of the fingerprint is generated using as many as 100,000 sensing points.


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