Non-fingerprint region indicator

• US 4,225,850 A
• Filed: 11/15/1978
• Issued: 09/30/1980
• Est. Priority Date: 11/15/1978
• Status: Expired due to Term

• Current Assignee: Printrak International, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Rockwell International Corporation
• Inventors: White, Stanley A., Riganati, John P., Kabaian, Jimmy H., Chang, Tien-Lin
• Primary Examiner(s): Boudreau, Leo H.
• Application Number:
  US05/960,813
• Time in Patent Office: 685 Days
• Field of Search: 340/146.3 E, 340/146.3 R, 340/146.3 H, 356/71, 350/162 SF, 364/576, 364/726, 324/77 B, 324/77 CS
• US Class Current: 382/124
• CPC Class Codes: G06V 10/10 Image acquisition document image scanning and transmission H04N1/00; control of digital cameras H04N23/60
• CPC Class Codes: G06V 10/20 Image preprocessing
• CPC Class Codes: G06V 10/24 Aligning, centring, orientation detection or correction of the image
• CPC Class Codes: G06V 10/42 Global feature extraction by analysis of the whole pattern, e.g. using frequency domain transformations or autocorrelation
• CPC Class Codes: G06V 40/1347 Preprocessing; Feature extraction

Abstract

Signalling means for enhancing the performance of automatic fingerprint identification systems by reducing system response to non-fingerprint-like regions within an image field pattern of interest. A two dimensional generalized sequency analyzer, such as a fast Fourier transform machine, responsive to a binary coded image signal identifies discrete frequency terms occurring within a selected bandwidth corresponding to a spatial frequency region of interest, associated with a fingerprint image. Logic means, responsive to the sequency analyzer, further identifies the relative energy levels of the bandwidth-limited spectral content of the binary coded image signal to signal the identity of a non-fingerprint-like region within the scanned image.

Claims

1. A pre-edit signalling system responsive to an electrical signal analog of a scanned image for indicating the probable absence or presence of a non-fingerprint region of such image, said system comprising

a two-dimensional sequency function transform analyzer responsive to a binary-coded image signal for identifying discrete frequency terms occurring within a preselected bandwidth corresponding to a spatial frequency region associated with descriptions of a fingerprint image;

and

logic means responsive to said bandwith limited transform analyzer for further identifying the relative energy level of the bandwidth-limited spectral content of the binary-coded image signal as an indication of the inclusion of a non-fingerprint region within the scanned image represented by said binary-coded signal analog.

2. The device of claim 1 in which said logic means includes multiple level thresholding means responsive to the total energy represented by the output of the bandwidth limited transform analyzer for indicating a degree of probability that the scanned image represents a non-fingerprint region.

3. The device of claim 1 in which said logic means comprises:

means for determining the total energy E represented by the discrete frequency term output of the bandwidth limited transform analyzer, as the signal sum of selected signals in the output of said analyzer and corresponding to at least the largest energy component occurring at a discrete first frequency, and a second largest energy component occurring at a second discrete frequency, said signal corresponding to said second largest energy component being attenuated as a function of the frequency spacing between the spatial frequencies of said largest and second largest energy components.

4. The device of claim 1 in which said logic means comprises:

means for determining the total energy E represented by the discrete frequency term output of the bandwidth limited transform analyzer, as the signal sum of selected signals in the output of said analyzer and corresponding to the largest energy component occurring at a discrete first frequency, a second largest energy component occurring at a second discrete frequency, and a third energy component occurring at a third discrete frequency, each of said signals corresponding to said second and third largest energy components being attenuated as a function of the frequency spacing between the spatial frequencies of said largest and respective second and third largest energy components.

5. The device of claim 3 or 4 in which said logic means further included means for identifying that discrete frequency term having the largest energy component associated therewith and comprising:

register means responsive to a current output sample and associated two-dimensional frequency address for temporary storage of said sample and associated address;

storage means for storing a previous data sample and the associated address thereof; and

comparator means responsive to said register means and storage means for comparing said current and previous data samples, said comparator cooperating with said storage means to dump said stored previous data sample and associated address and substitute said current sample and associated address in said storage means, in response to said current sample exceeding said stored sample.

6. The device of claims 2, 3 or 4 in which said means for determining the total energy E comprises:

amplitude means responsive to data sets (e_i, ω

_x.sbsb.i and ω

_y.sbsb.i) representing the two-dimensional discrete frequency transform output of the transform analyzer for determining that data set corresponding to a predominant data set (e_i, ω

_x.sbsb.i, ω

_y.sbsb.1) and at least a second next most predominant data set (e₂, ω

_x.sbsb.2 and ω

_y.sbsb.2), where |e₁ |<

|e₂ |;

frequency spacing means responsive to the two-dimensional frequency coordinates associated with said first predominant and at least a second next most predominant data set for determining an attenuation factor;

attenuation means responsive to said frequency spacing means for attenuation of an energy term of said second predominant data set; and

signal combining means responsive to said amplitude means and said attenuation means for providing a signal output E indicative of the sum of said predominant energy term and said attenuated energy term.

7. The device of claim 1 in which said logic means includes:

first signalling means responsive to the discrete frequency term output of the bandwidth limited transform analyzer for generating a signal indicative of the largest energy component occurring at a discrete first frequency,

second signalling means responsive to said first signalling means for generating a signal indicative of a second largest energy component occurring at a second discrete frequency, said second signalling means including signal attenuating means for attenuating said signal indicative of said second largest energy component as a function of the frequency spacing between said first and second discrete frequencies.

8. The device of claim 1 in which said logic means includes:

first signalling means responsive to the discrete frequency term output of the bandwidth limited transform analyzer for generating a signal indicative of the largest energy component occurring at a discrete first frequency,

second signalling means responsive to said first signalling means for generating a signal indicative of a second largest energy component occurring at a second discrete frequency, said second signalling means including signal attenuating means for attenuating said signal indicative of said second largest energy component as a function of the frequency spacing between said first and second discrete frequencies; and

summing means responsive to said first and second signal means for providing an output indicative of the sum of the inputs thereto.

9. The device of claim 1 in which said logic means comprises

means for determining the total energy E represented by the discrete Fourier term output of the bandwidth limited fast Fourier transform analyzer, as the sum of selected signals in the output of said analyzer and corresponding to at least the largest energy component occurring at a discrete first frequency, a second largest energy component occurring at a second discrete frequency, said signal corresponding to said second largest energy component being attenuated as a function of the frequency spacing between the spatial frequencies of said largest and second largest energy components, and

multiple thresholding means responsive to said means for determining for indicating ones of preselected threshold levels exceeded by the bandwidth limited response of said analyzer.

10. The device of claim 1 in which said logic means includes means for identifying those respective discrete Fourier terms having the largest and second largest energy components, respectively, and the associated two-dimensional frequency addresses thereof.

11. The device of claim 10 in which said means for identifying includes:

first peak detection means adapted to be responsive to an applied input for storing a first detected peak value (e₁) of a data train and discarding all other data of the data train, and

second peak detecting means responsive to said all other data of the data train for storing a second peak detected value (e₂ <

e₁) of said data train and discarding the remainder of the data.

12. A pre-edit signalling subsystem for use in a fingerprint identification system and responsive to an electrical signal analog of a scanned image for indicating the presence/absence of a non-fingerprint region of such image, said subsystem comprising:

a two-dimensional sequency transform analyzer responsive to a binary-coded image signal for identifying the two largest discrete frequency terms occurring within a selected bandwidth corresponding to a spatial frequency region describing the description of a fingerprint image; and

logic means responsive to said bandwidth limited transform analyzer for further identifying the relative energy levels of the spectral content of the binary-coded image signal, for indicating the probability that the scanned image represented by said binary coded signal analog represents a non-fingerprint region.

13. A pre-edit signalling system responsive to an electrical signal analog of a scanned image for indicating the probable absence or presence of a non-fingerprint region of such image, said system comprising

signalling means response to a grey level electrical signal corresponding to a scanned image, for providing a compacted, thresholded binary-coded electrical signal;

a two-dimensional sequency transform analyzer responsive to said binary-coded signal for identifying discrete frequency terms occuring within a preselected bandwidth corresponding to a spatial frequency region associated with descriptions of a fingerprint image; and

logic means responsive to said bandwidth limited transform analyzer for further identifying the relative total energy level of the bandwidth limited spectral content of the binary-coded image signal as in terms of the probability of the scanned image corresponding to said binary-coded signal representing a non-fingerprint region.

14. The device of claim 13 in which said signalling means comprises

data comparator means responsive to a matrix (n×

n) of discrete grey level first pixels corresponding to an image field of interest for combining clusters of contiguous grey level pixels to provide a compacted matrix (N/2×

n/2) of second pixels, each said second pixel having a grey level corresponding to the average grey level of the associated pixel cluster represented by such second pixel.

15. The device of claim 14 in which said signalling means further comprises means for thresholding signals representing said second pixels of said compacted matrix to provide binary-coded signals corresponding to a binary-coded data matrix representing said scanned image.

16. A pre-edit signalling system responsive to an electrical signal analog of a scanned image for indicating the probable absence or presence of a non-fingerprint region of such image, said system comprising

a two-dimensional periodic function transform analyzer responsive to a binary-coded image signal for identifying discrete periodic function frequency terms occurring within a preselected bandwidth corresponding to a spatial frequency region associated with descriptions of a fingerprint image;

and

logic means responsive to said bandwidth limited transform analyzer for further identifying the relative energy level of the bandwidth-limited spectral content of the binary-coded image signal as an indication of the inclusion of a non-fingerprint region within the second image represented by said binary-coded signal analog.

17. The device of claim 16 in which said logic means comprises:

means for determining the total energy E represented by the frequency term output of the bandwidth limited transform analyzer, as the sum,

space="preserve" listing-type="equation">e.sub.1 +(e.sub.2 /d.sub.12.sup.2)+(e.sub.3 /d.sub.13.sup.2),

where

e₁ =the largest energy component occurring at a first discrete frequency

e₂ =a second largest energy component occurring at a second discrete frequency

e₃ =a third energy component occurring at a third discrete frequency

d₁₂ =the frequency interval or spacing between e₁ and e₂

d₁₃ =the frequency interval or spacing between e₁ and e₃.

18. The device of claim 17 in which said logic means further includes means for identifying that discrete Fourier term having the largest energy component associated therewith and comprising:

a first register responsive to a current serial output sample of said fast Fourier transform analyzer for temporary storage of said current sample;

first storage means for storing a previous data sample input thereto;

a comparator responsive to said first register and said first storage means for comparing the amplitudes represented by said current sample and previous sample;

a second register responsive to a two-dimensional frequency address of said fast Fourier serial output sample; and

a second register for storing a two-dimensional frequency address associated with said previous data sample,

said comparator, in response to said current sample exceeding said stored sample, cooperating to dump said stored previous sample and associated stored address from said first and second storage means, respectively, and substitute said exceeding current sample and the associated address therefor in a respective one of said storage means.

19. The device of claim 17 in which said logic means further includes means for identifying that discrete Fourier term having the largest energy component associated therewith and comprising:

register means responsive to a current said output sample and associated two-dimensional frequency address for temporary storage of said sample and associated address;

storage means for storing a previous data sample and the associated address thereof; and

comparator means responsive to said register means and storage means for comparing said current and previous data samples, said comparator cooperating with said storage means to dump said stored previous data sample and associated address and substitute said current sample and associated address in said storage means, in response to said current sample exceeding said stored sample.

20. The device of claim 17 in which said logic means includes means for identifying those respective discrete Fourier terms having the largest, and second and third largest energy components, respectively, and the associated two-dimensional frequency addresses thereof.

21. The device of claim 20 in which said means for identifying includes:

a first peak detection means adapted to be responsive to an applied input for storing a first detected peak value (e₁) of a data train and discarding all other data of the data train,

second peak detecting means responsive to said all other data of the data train for storing a second peak detected value (e₂ <

e₁) of said data train and discarding the remainder of the data, and

third peak detecting means responsive to the remainder of said data train for storing a third peak value (e₃ <

e₂ <

e₁) of said data train.

22. The device of claim 16 in which said logic means includes multiple level thresholding means responsive to the total energy represented by the output of the bandwidth limited Fourier transform analyzer for indicating a degree of probability that the scanned image represents a non-fingerprint region.

23. The device of claim 16 in which said logic means comprises means for determining the total energy E represented by the discrete Fourier term output of the bandwidth limited fast Fourier transform analyzer, as the sum,

28. The device of claims 17, 23 or 27 in which said logic means E comprises:

amplitude means responsive to data sets (ω

_x.sbsb.i, ω

_y.sbsb.i and e_i) representing the two-dimensional discrete Fourier transform output of the fast Fourier transform analyzer for determining that data set corresponding to a predominant data set (e₁, ω

_x.sbsb.1, ω

_y.sbsb.1) and a second and third next most predominant data set (e₂, ω

_x.sbsb.2 and ω

_y.sbsb.2) and (e₃, ω

_x.sbsb.3 and ω

_y.sbsb.3), where |e₁ |>

|e₂ |>

|e₃ |,

frequency spacing means responsive to the two dimensional frequency coordinates associated with said first predominant second and third next most predominant data sets for determining the frequency spacing factors d₁₂^1/2 and d₁₃^1/2,

signal combining means responsive to said amplitude means and frequency spacing means for providing a signal output E indicative of the relationship, e₁ +(e₂ /d₁₂²)+(e₃ /d₁₃²).

29. The device of claim 28 in which said signal combining means comprises:

first multiplier means responsive to data element e₂ and factor d₁₂^1/2 for providing an output e₂ /d₁₂² corresponding to the product of the applied inputs thereto;

second multiplier means responsive to data element e₃ and factor d₁₃^1/2 for providing an output e₃ /d₁₃² corresponding to the product of the applied inputs thereto; and

output data summing means responsive to data element e₁ and to the outputs of said first and second multiplier means for providing an output E corresponding to the sums of the applied inputs thereto.

24. A pre-edit signalling subsystem for use in a fingerprint identification system and responsive to an electrical signal analog of a scanned image for indicating the presence/absence of a non-fingerprint region of such image, said subsystem comprising:

a two dimensional fast Fourier transform analyzer responsive to a binary-coded image signal for identifying the two largest discrete Fourier terms occurring within a selected bandwidth corresponding to a spatial frequency region describing the description of a fingerprint image; and

logic means responsive to said bandwidth limited fast Fourier transform analyzer for furtheer identifying the relative energy levels of the spectral content of the binary-coded image signal, for indicating the probability that the scanned image represented by said binary coded signal analog represents a non-fingerprint region.

25. A pre-edit signalling system responsive to an electrical signal analog of a scanned image for indicating the probable absence or presence of a non-fingerprint region of such image, said system comprising

signalling means response to a grey level electrical signal corresponding to a scanned image, for providing a compacted, thresholded binary-coded electrical signal;

a two dimensional fast Fourier transform analyzer responsive to said binary-coded signal for identifying discrete Fourier terms occurring within a preselected bandwidth corresponding to a spatial frequency region associated with descriptions of a fingerprint image; and

logic means responsive to said bandwidth limited fast Fourier transform analyzer for further identifying the relative total energy level of the bandwidth limited spectral content of the binary-coded image signal as in terms of the probability of the scanned image corresponding to said binary-coded signal representing a non-fingerprint region.

26. The device of claim 25 which said sampling means comprises

data comparator means responsive to a matrix (n×

n) of discrete grey level first pixels corresponding to an image field of interest for combining clusters of contiguous grey level pixels to provide a compacted matrix (n/2×

n/2) of second pixels, each said second pixel having a grey level corresponding to the average grey level of the associated pixel cluster represented by such second pixel.

27. The device of claim 25 in which said signalling means further comprises means for thresholding signals representing said second pixels of said compacted matrix to provide binary-coded signals corresponding to a binary-coded data matrix representing said scanned image.