Checkout of effective fingerprint signal under condition of light interference and identifying method for residual fingerprint
A fingerprint signal and interference signal technology, which is applied in character and pattern recognition, computer parts, instruments, etc., can solve the problems of inability to identify signal light interference signals, etc.
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Embodiment 1
[0053] figure 2 .For the setting of the foreground and background areas in the sensing area A of the optical sensor. Foreground A f Located in the center, represented by four local neighborhoods 5, 6, 7, and 8 in the figure; background area A b The four sub-blocks 1, 2, 3, and 4 of are located at the four corners of A respectively.
[0054] image 3 .In order to detect effective fingerprint signals, interference signals, and identify the interpretation process of residual fingerprints. Enable monochromatic red illumination image signal 21, judge A f Whether the average value of the gray value of the signal within is less than the threshold E T 22, if less than E T , and then judge A f Whether the variance of the gray value of the internal signal is greater than the threshold D T 23, if greater than D T , it is judged as valid fingerprint signal 24; if less than D T , into the secondary screening of fingerprint signals 25 . As mentioned earlier, the mean value E of ...
Embodiment 2
[0059] Figure 4 As shown, its function is that after the process 23 fails to detect valid fingerprint signals, a second screening judgment is performed to identify valid fingerprint information that may be included; or it is judged as an interference signal. The specific method is to judge whether the ratio of the variance of the front and background gray values is less than the threshold R T1 41. If it is too small, it is judged as an interference signal 42; if it is greater than the threshold R T1 , and further judge whether the variance of the foreground and background gray values satisfies the inequality D f -(D b · R T1 )>R T2 43. If yes, it is judged as valid fingerprint 44; otherwise, it is judged as interference information.
Embodiment 3
[0061] Figure 5 As shown, its effect is that the illumination light signal is in the following conditions:
[0062] When E f >E T
[0063] and D f D b R T (cannot be judged as a valid fingerprint)
[0064] Before the non-illuminated light signal needs to be used for further interpretation, in order to reduce the possibility of interference signals being brought into the subsequent process, some images that are very likely to be interference signals must be checked first. The conditions for checking interference features are:
[0065] if E f E b > R T 3
[0066] It is judged as an interference signal;
[0067] otherwise,
[0068] Start the follow-up...
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