User's Manual

A PPENDIX A – Q UALITY AND C ONTENT

Section A.3 - Using Content and Quality during Enrollments

As described in section A.1, Quality and Content scores are returned in the enrollment

process. These scores give an indication of the performance of the template enrolled. To a

large degree, the verification algorithm compensates for deficiencies in image quality and

loss of information content. Nonetheless, knowledge of these parameters and what they

mean helps ensure optimal performance.

False Acceptance and False Rejection

In order to understand the effects of poor image quality and poor information content it

is necessary to understand how to measure performance. Performance of the Veri-

Series unit is presented in terms of False Rejection and False Acceptance.

False Rejection indicates that the unit incorrectly rejected a fingerprint that

corresponds to the person’s template. False Rejections rarely occur and

primarily result from the inability to get a good image of the finger.

False Acceptance indicates that the unit accepted a fingerprint that does

not correspond to the template it was compared against. False

Acceptances also are rare and primarily result when a fingerprint template

is characterized by low information in the enrolled print.

The algorithm on the Veri-Series units has been tuned so that the false acceptance

and false rejection rates are equal at the medium security level (level 3), delivering the

industry leading accuracy. This is known as the Equal Error Rate. Increasing the

security (e.g., changing the security level from 3 to 1) will decrease the chance for

false acceptance at the expense of increased false rejection. Reducing the security

(e.g., changing the security level from 3 to 5) will decrease the chance of a false

rejection at the expense of false acceptance. The table below indicates the expected

error rates at the different security levels.

Security Level False Rejection Rate False Acceptance Rate

Very Low (5) 1 / 10,000 1 / 100

Low (4) 1 / 5000 1 / 200

Medium (3) 1 / 1000 1 / 1000

High (2) 1 / 200 1 / 5000

Very High (1) 1 / 100 1 / 20,000