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Installer Reference Guide
CM728B-CM729B
Understanding Fingerprint Analysis, Reader Limitations And Other Considerations
Fingerprint patterns are made up of shapes, which determine the general classification
characteristics of the print. In all fingerprints a centre part can be found, which is called
the fingerprint core. The area surrounding the core holds many of the interesting finger-
print characteristics that are unique for each individual.
The upper parts of all fingerprints look very much alike (parallel curves) with very few
distinct areas. To ensure adequate fingerprint detail is available, users should make sure to
place the entire core area of the fingertip onto the sensor area using the placement dimple
as a guide.
Do not point the end of the finger onto the sensor as this part of the fingerprint does not
contain enough unique biometric information for high security applications. Also note
that you do not need to place any downward pressure for the sensor to read the credential.
According to the fingerprint and system characteristics described above, the following conclusions can be made
regarding placement of the finger:
• The finger should be placed in the same position every time.
• The fingertip should cover the whole sensor surface.
• The fingerprint core should be placed as near the sensor centre as possible.
Fingerprint recognition systems are limited by the number of calculations required for authentication, and the num-
ber of iterations can be reduced by means of correct fingertip placement and repeatability. There are several situa-
tions which can arise when the using the system that may lead to unreliable performance. These can be divided into
the following four areas; translation, rotation, finger pitch and finger roll.
Translation - is defined as the difference in horizontal and/or vertical
direction from the enrolled template to the verification occasion.
The CM728B and CM729B readers allow a few millimetres in both
horizontal and vertical direction (between the enrolled fingerprint
and the verified fingerprint). Translation is essentially a result of the
lack of guidance of the fingertip in both directions. The level of
translation depends also on the finger size. If the user has small
fingers then there is more space for the finger to move around
compared to a bigger finger.
Finger Rotation - is defined as the angle difference between an
imaginary centre line of the finger from one placement to another.
The CM728B and CM729B readers allow some variation from the
enrolment occasion but when the rotation exceeds a certain angle, the
algorithms will not be able to handle this variation. Small fingers are
generally more susceptible to finger roll issues.
8
Enrolment
Figure 6: Fingerprint Core
Enrolment
Figure 7: Fingerprint Core
Bosch Security Systems 06/12 CM728B-CM729BIRG FTR1.0
Figure 5: Fingerprint Core
Verification
Verification
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