Note that the assumption of statistic independence appears justifiable based on the hypothesis of uniqueness. Imperfections such as a dirty finger generally, however, often coincide with other fingers, so that a certain statistical dependence cannot be avoided. For the Case 2, this means a reduced improvement of FRR. Furthermore, in practice it is rare that the performance data FAR and FRR are the same for every finger n.
Cases 1 and 2 are extreme cases. With suitable systems, the information fusion allows 'in term ediate levels' to exist. In principle, every set recognition threshold should have a way, which by combining multiple fingerprints makes a simultaneous improvement of FAR and FRR possible.
Q: Which type of sensor is the best?
A: This question unfortunately offers no definitive answer, as every application has different requirements and each type of sensor has its specific advantages and disadvantages. The following criteria can assist in reaching an answer:
· Costs
· Degree of maturity
· Image quality in suboptimal conditions
o indoor/outdoor
o personal/public use
o normal/abnormal fingers
o dry/moist fingers
· Size
· Sensitivity against vandalism
· Temperature resistance
· Sensitivity against forgery
· ESD (electrostatic discharge) sensitivity
Q: How do fingerprint sensors work?
A:All fingerprint sensors try to generate a digital picture of the finger surface. This picture normally has a pixel resolution of 500 dpi. The picture generation can be different for every type of sensor.
Optical Reflexive Sensor
The finger lies on a prism surface for example. Where the finger ridges touch the glass,a total reflection of light inside of the glass is disturbed. This will supply a picture of the finger lines to a camera chip.
Optical Contactless Sensor
The finger surface is directly acquired by a camera chip. The fingerprint area needs no contact to a plate.
Q: How does biometrics work?
A: Your finger, iris or other unique body part is first scanned and
digitally stored in the biometric system. Each time you want to gain access,
your finger or iris is scanned again and compared against the stored sample.
If the two match within a preset threshhold, you are allowed access.
· Why verification fails even the
fingers were enrolled?
Reasons
Resolution
1.Didn’t enroll correctly.
Refer to section 2.4.7 and enroll fingerprints again.
2.Finger is too dry.
Have a breath on the finger, and then press with some pressures.
3.Have oil, smudginess and make up on the finger.
Clean the finger.
4.Fingerprint is not perfect, such as dry, break, molt and callus.
Refer to section 2.4.7, changing the finger and enroll it again.
5.Put the finger in a wrong position.
Refer to section 2.4.7
6.The fingerprint collected window is dirty.
Clean the glass surface of the collected window.
7.The affection of the finger skin’s change
Refer to section 2.4.7 and enroll it again.
8.The collected window with the direct sunshine and strong light.
Put the machine at the place where avoiding the direct sunshine and the strong light.
9.Press with un-enrolled finger.
Press with enrolled finger
· Why prompt verification error under different verification means?
Reasons
Resolutions
1.The communication hasn’t been operated correctly.
The communication of the software should be accorded with the T&A
2.Electric line’s problem or not be inserted well.
Insert the electric line again or change another line. How to make a electric line please refer to the section 2.2
3.RS232 interface can’t access successfully.
Please check the interface numbers, baud rate and instrument numbers. The T&A should be accorded with the software.
4.RS485 main line can’t access successfully.
Please check the interface numbers, baud rate and instrument numebers,485 main line is not permitted the repeated instrument numbers, please choose the professional RS485-232.
5.Ethernet can’t access successfully.
Please check the IP address.
6. USB fails to connect
Check if the attendance machine drive program is installed.
7.attendance machine fails to read flash disk
Please select flash disk with better quality. The flash disk can not have more than one hard disk partition
· Why T&A fails to connect with PC?
Reasons
Resolutions
1.The communication hasn’t been operated correctly.
The communication of the software should be accorded with the T&A
2.Electric line’s problem or not be inserted well.
Insert the electric line again or change another line. How to make a electric line please refer to the section 2.2
3.RS232 interface can’t access successfully.
Please check the interface numbers, baud rate and instrument numbers. The T&A should be accorded with the software.
4.RS485 main line can’t access successfully.
Please check the interface numbers, baud rate and instrument numebers,485main line is not permitted the repeated instrument numbers, please choose the professional RS485-232.
5.Ethernet can’t access successfully.
Please check the IP address.
6. USB fails to connect
Check if the attendance machine drive program is installed.
7.attendance machine fails to read flash disk
Please select flash disk with better quality. The flash disk can not have more than one hard disk partition
· Why the T&A will remind' Please press the finger again' when nobody attend?
Reasons
Resolutions
1.The collected window with the direct sunshine and strong light.
Put the machine at the place where avoiding the direct sunshine and the strong light.
FAQ