US922 USER GUIDE | 2016
5
Getting Good Fingerprint Images
The quality of fingerprint images is relative to the number of minutiae points cap-
tured by the US922’s sensor. Fingerprint images not possessing an adequate number
of minutiae points may be unreadable. It is advised to issue a secret password for
those users whose fingerprint images lack sufficient minutia points and cannot be
read by the sensor. Also, you may consider purchasing an US922 with an integrated
card reader if you do not intend to assign passwords
Figure A-2 shows poor-quality fingerprints, characterized by smudged, faded or dis-
torted areas on the fingerprint. These conditions can be caused by excessive dryness,
wetness, insufficient pressure or scarring of the skin at the fingertip..
Dry
Wet
Scarred
The US922 fingerprint matching algorithm is capable of extracting the correct minu-
tiae without the benefit of a perfect print. However, the positioning of the finger and
the moisture and pressure of the fingerprint are significant factors to consider when
it is placed on the sensor. This will help achieve a good consistent fingerprint match.
Correcting Wet or Dry Fingerprint Images
When the temperature is rigid or when hands have just been washed, fingerprints
often become very dry. In this case, the user should moisturize his/her fingerprint
simply by breathing on the fleshy pad of his/her fingertip prior to placing his/her fin-
ger on the sensor. The moisture from his/her breath should improve the recognition
of his/her fingerprint.
Conversely, if the fingerprint is too wet, the ridges and valleys are rendered indistin-
guishable. The lack of recognizable minutiae causes wet fingerprints to be rejected
by the US922. This can be remedied simply by swiping the finger on a clean dry
towel or cloth.
How much pressure is required for a good-quality
fingerprint?
If too much pressure is applied when pressing down on the sensor, the finger’s
ridges become pressed together and create an unrecognizable image. Applying too
much pressure (similar to fingerprints that are too wet) will create a “blurred” image
which the US922 sensor might not recognize.
If too little pressure is applied, the resulting image will be similar to the dry fingerprint
and unidentifiable. Issues related to moisture and pressure can easily be addressed
with practice and users getting a feel of the sensor.
Be sure to maintain contact with the fingerprint sensor for 2 full seconds, until
the US922 responds.
The US922 has both audio and visual indicators which respond when the US922
senses a finger.
Fingerprint Recognition Technology
