Method and system for biometric image assembly from multiple partial biometric frame scans

• US 7,197,168 B2
• Filed: 07/12/2002
• Issued: 03/27/2007
• Est. Priority Date: 07/12/2001
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Atrua Technologies Incorporated (Apple Inc.)
• Inventors: Russo, Anthony P.
• Primary Examiner(s): Bali; Vikkram
• Application Number:
  US10/194,994
• Publication Number:
  US 20030126448A1
• Time in Patent Office: 1,719 Days
• Field of Search: 382124-127, 382/193, 382/195, 382/209, 382215-217, 340/5.53, 340/5.83, 902/3, 713/186
• US Class Current: 382/125
• CPC Class Codes: G06Q 10/02 Reservations, e.g. for tickets, services or events
• CPC Class Codes: G06Q 20/04 Payment circuits
• CPC Class Codes: G06Q 20/4016 involving fraud or risk level assessment in transaction processing
• CPC Class Codes: G06Q 30/06 Buying, selling or leasing transactions
• CPC Class Codes: G06V 40/1335 Combining adjacent partial images (e.g. slices) to create a composite input or reference pattern; Tracking a sweeping finger movement
• CPC Class Codes: H04L 2209/08 Randomization, e.g. dummy operations or using noise
• CPC Class Codes: H04L 2209/805 Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor
• CPC Class Codes: H04L 9/3231 Biological data, e.g. fingerprint, voice or retina network architectures or network communication protocols for supporting authentication of entities using biometrical features in a packet data network H04L63/0861

Abstract

Method and system for reconstructing seamless fingerprint image from set of image slices, or frames, from fingerprint swipe sensor. Robust normalized cross-correlation procedures are used for frame evaluation and image matching. Efficient use of device processing resources including memory by keeping only data frames that indicate moving finger and discards frames where no finger exists at sensor during acquisition or finger has not moved since last frame was acquired. Capability to adjust sensor settings during acquisition process to obtain optimal results. Logic ensures operation across different physical systems and sensor characteristics with varying acquisition speeds. Statistics regarding resulting reconstructed image and finger swiping process are computed and embedded in reconstructed image and are useful to the downstream fingerprint matching system, and by embedding in image, inventive system and method ensure that any fingerprint processing system can use information if when called upon to do so.

Claims

1. A method for acquiring a plurality of biometric image frames from a sensor and generating a reconstructed composite image from at least some of said plurality of acquired biometric image frames, said method comprising:

(a) acquiring a frame from said sensor and storing the acquired frame in a memory as a last stored frame;

(b) comparing the stored frame to the reconstructed composite image to determine any usefulness and any alignment registration relationship between the acquired frame and said reconstructed composite image that is being generated;

(c) updating the generated reconstructed composite image to incorporate at least a portion of the acquired frame to extend the length (height) of the generated reconstructed composite image and storing the updated generated reconstructed composite image in a memory;

(d) determining if frame acquisition should be stopped according to a frame acquisition stop criteria; and

(e) if it is determined that frame acquisition should be stopped then stopping acquiring frames and identifying the then currently updated generated reconstructed composite image as the final generated reconstructed composite image, and otherwise repeating the procedure of acquiring additional frames through determining if frame acquisition should be stopped until it is determined that frame acquisition should be stopped.

2. A method as in claim 1, further comprising prior to said acquiring a frame from said sensor, performing one or more of:

initializing said sensor and adjusting an operating condition of said sensor.

3. A method as in claim 1, further comprising after said acquiring said frame from said sensor, estimating or determining properties of said acquired frame.

4. A method as in claim 3, further comprising retrieving information from the stored frame to use in estimating or determining said frame properties.

5. A method as in claim 4, wherein said estimating or determining frame properties including determining if a newly acquired frame has any new information as compared to the previous stored useful frame.

6. A method as in claim 1, further comprising after said acquiring said frame from said sensor, determining whether to keep or discard the acquired frame and keeping or discarding the acquired frame according to said keep/discard determination.

7. A method as in claim 6, wherein if the acquired frame is kept, storing the acquired stored frame as the last useful frame in a memory.

8. A method as in claim 1, wherein the comparing includes performing a correlation between at least a portion of the stored frame and a portion of the reconstructed composite image.

9. A method as in claim 8, wherein the correlation includes using statistics of the reconstructed image being generated.

10. A method as in claim 9, wherein said correlation comprises a normalized cross-correlation.

11. A method as in claim 10, wherein the normalized cross-correlation includes using statistics of the reconstructed image being generated.

12. A method as in claim 1, wherein the comparing includes using statistics of the reconstructed image being generated.

13. A method as in claim 1, further comprising updating the reconstructed image statistics including the contribution of the incorporated portion of the acquired frame.

14. A method as in claim 1, wherein said storing includes storing of said reconstructed image statistics in a memory in association with the updated generated reconstructed composite image.

15. A method as in claim 1, further comprising adjusting sensor settings after the updated generated reconstructed composite image is updated.

16. A method as in claim 1, further comprising adjusting sensor settings if the last acquired frame was discarded and not used for reconstruction, prior to the acquisition of the next frame.

17. A method as in claim 1, wherein said stop criteria is selected from the group of stop criteria consisting of:

a total number of frames captured, a number of consecutive frames captured where no finger movement is observed, a number of consecutive frames captured where no biometric data is determined to exist, and combinations thereof.

18. A method as in claim 1, wherein said biometric comprises a fingerprint biometric.

19. A method as in claim 18, wherein the comparing comprise performing a correlation or performing the mathematically or functionally equivalent of a correlation.

20. A method as in claim 18, wherein the comparing comprises performing a normalized cross correlation or performing the mathematically or functionally equivalent of a normalized cross correlation.

21. A method as in claim 18, wherein said fingerprint biometric comprises a region of a human fingerprint less than the total region of a human fingerprint biometric needed for fingerprint identification by matching.

22. A method as in claim 1, further comprising generating and storing post-reconstruction image information about the final generated reconstructed composite image.

23. A method as in claim 22, wherein the post-reconstruction image information are stored with the final generated reconstructed composite image.

24. A method as in claim 22, wherein the post-reconstruction image information are encoded or stored with the final generated reconstructed composite image data set.

25. A method as in claim 22, wherein the post-reconstruction image information are encoded or stored in a header record of the final generated reconstructed composite image data set.

26. A method as in claim 22, wherein the post-reconstruction image information comprises statistical information.

27. A method as in claim 22, wherein the statistical information is selected from the set of statistical metrics consisting of:

a final reconstructed image height, an angle of swipe, a speed of swipe, and combinations thereof.

28. A method as in claim 1, wherein the frame is a scan of an imaged portion of a fingerprint, and said final generated reconstructed composite image is a larger imaged portion of said fingerprint.

29. A method as in claim 28, further comprising performing minutiae identification and extraction on said final generated reconstructed composite fingerprint image.

30. A method as in claim 28, wherein said sensor is a swipe sensor that acquires a plurality of frames at a frame rate of said sensor, and said acquiring, comparing, updating, and determining, are performed in real-time according to said sensor frame acquisition rate.

31. A method as in claim 28, wherein said sensor is a swipe sensor that acquires a plurality of frames at a frame rate of said sensor, and said acquiring is performed in real-time according to said sensor frame acquisition rate and said comparing and updating are performed in non-real-time using a plurality of prior stored acquired frames.

32. A method for generating a reconstructed image from a plurality of acquired biometric image frames, said method comprising:

acquiring a frame from said sensor and storing the acquired frame;

comparing the acquired frame to a partially reconstructed image to determine any usefulness and any alignment registration relationship between the acquired frame and said reconstructed composite image that is being generated;

updating the generated reconstructed image to incorporate at least a portion of the acquired frame to extend the length (height) of the generated reconstructed composite image and storing the updated generated reconstructed composite image in a memory;

determining if frame acquisition should be stopped according to a frame acquisition stop criteria; and

if it is determined that frame acquisition should be stopped then stopping acquiring frames and identifying the then currently updated generated reconstructed composite image as the final generated reconstructed composite image, and otherwise repeating the procedure of acquiring additional frames through determining if frame acquisition should be stopped until it is determined that frame acquisition should be stopped.

33. A method as in claim 32, wherein said biometric comprises a fingerprint biometric.

34. A method as in claim 33, wherein the comparing comprise performing a correlation or performing the mathematically or functionally equivalent of a correlation.

35. A method as in claim 34, wherein the comparing comprises performing a normalized cross correlation or performing the mathematically or functionally equivalent of a normalized cross correlation.

36. A method as in claim 33, wherein said fingerprint biometric comprises a region of a human fingerprint less than the total region of a human fingerprint biometric needed for fingerprint identification by matching.

37. A method as in claim 32, further comprising performing an analysis of the content of the acquired frame to determine if it contains any useful fingerprint biometric information.

38. A method as in claim 37, wherein the determination of whether there is any useful fingerprint information in a collected frame is a pattern based determination.

39. A method as in claim 37, wherein the determination of whether there is any useful fingerprint information in a collected frame is an image statistic based determination using measured frame image statistics including an average value and a variance of at least a portion of the acquired frame.

40. A method as in claim 39, wherein said portion comprises the entire acquired frame.

41. A method as in claim 39, wherein said portion comprises a number of frame pixel elements less than the entire acquired frame.

42. A method as in claim 39, wherein the frame or partial frame average value M is given by the expression:

43. A method as in claim 42, wherein the frame or partial frame variance Ψ

is given by the by the expression;

44. A method as in claim 43, wherein the acquired frame is determined to contain only noise rather than any biometric information if the frame average is:

(i) equal to or above a high noise average threshold value, (ii) equal to or below a low noise average threshold value, or (iii) the frame variance is less than or equal to a variance average threshold value according to;

Φ

≧

Noise_average_threshold_high or if

Φ

≦

Noise_average_threshold_low, or if

Ψ

≦

Variance_average_threshold.

45. A method as in claim 37, wherein the determination as to whether the acquired frame contains any new biometric information comprises determining the correlation, cross-correlation, normalized correlation, or normalized cross-correlation between the last stored useful acquired frame and the current acquired frame.

46. A method as in claim 45, wherein all of the pixels in each of the last stored useful acquired frame and the current acquired frame are compared by correlation or normalized cross-correlation.

47. A method as in claim 45, wherein fewer than all rows of pixels in each of the last stored useful acquired frame and the current acquired frame are compared by correlation or normalized cross-correlation.

48. A method as in claim 45, wherein one row of pixels in the last stored useful acquired frame and the same row of pixels in the current acquired frame are compared by correlation or normalized cross-correlation.

49. A method as in claim 45, wherein the any new biometric information determination cross-correlation comprises a cross-correlation (Correlation(R,d)) of row R of the last useful acquired frame (lastFrame[R,m]) with row R of the current acquired frame (curtFrame[R,m-d]) according to the expression:

50. A method as in claim 49, wherein d is set to be equal to zero (d=0) for detecting lack of movement.

51. A method as in claim 49, wherein the cross-correlation is maximized if the pixel values in each of the last stored useful acquired frame and the currently acquired frame are identical and lack of movement is determined by comparing the correlation expression value Correlation(R,0) with a movement detection correlation threshold value so that there is assessed to be insufficient movement to constitute new information when the correlation value is greater than or equal to the movement correlation threshold value, or:

Correlation (R,

     0)≧

Movement_correlation_threshold.

52. A method as in claim 51, wherein the correlation comprises a movement detection normalized cross correlation.

53. A method as in claim 52, wherein the movement detection normalized cross-correlation is substantially invariant to changes in image pixel gray-level or intensity value which may result from changes in finger contact pressure, sensor bias or gain drift, sensor automatic gain control (AGC) changes.

54. A method as in claim 53, wherein the movement detection normalized cross-correlation has a range due to the normalization component that is substantially independent of the number of frame pixels used in the normalized cross-correlation calculation.

55. A method as in claim 53, wherein the movement detection normalized cross-correlation is more accurate than other non-normalized comparisons or correlations because it is less dependent on local properties of the image frames being correlated.

56. A method as in claim 53, wherein the movement detection normalized cross-correlation is determined for any of:

a row, a plurality of rows, a patch or region of a frame, where a patch or region of a frame may be equal to a row, a subset of a row, a superset of a plurality of rows, or a collection of subsets or supersets of a plurality of rows.

57. A method as in claim 56, wherein the patches of each frame to be correlated are any arbitrary set of pixels.

58. A method as in claim 56, wherein the patches of each frame to be correlated are the middle row of each frame.

59. A method as in claim 56, wherein the movement detection normalized cross correlation (NCC) for patches (P) of a frame is given by the expression:

60. A method as in claim 52, wherein the movement detection normalized cross correlation (NCC) for rows (or regions) R of a frame is given by the expression:

61. A method as in claim 60, wherein the currently acquired frame is determined to have no movement relative to the last stored useful acquired frame if the normalized movement detection cross-correlation NCC is greater than a movement detection normalized cross-correlation threshold value given by the expression:

NCC>

Movement_NCC_threshold.

62. A method as in claim 61, wherein movement detection normalized cross-correlation threshold (movement_NCC_threshold) has a value between substantially 0.8 and substantially 0.99 for an NCC range of 0 and 1.0 or an equivalent range of movement detection normalized cross-correlation threshold for an NCC scaled and or offset by a scaling constant and/or an offset bias.

63. A method as in claim 61, wherein movement detection normalized cross-correlation threshold (Movement_NCC_threshold) has a value of substantially 0.95 for an NCC range of 0 and 1.0 or an equivalent range of movement detection normalized cross-correlation threshold for an NCC scaled and or offset by a scaling constant and/or an offset bias.

64. A method as in claim 52, wherein the movement detection normalized Cross-Correlation NCC(R,d) at row or region R and a lag of d is determined, for the columns in row or region R, by summing the following terms for each pixel in row or region R and then dividing by a normalization:

(a) the difference of each pixel in row or region R of the last frame to the average value of that row or region, and (b) the difference of each pixel in row or region R of the current frame to the average value of that row or region where the column is offset by d, and multiplying the two above terms (a) and (b); and

dividing the sum by a normalization term so that the movement detection normalized cross-correlation ranges from 0 to 1.

65. A method as in claim 32, wherein the comparing further comprising correlating the acquired frame to the partially reconstructed image.

66. A method as in claim 65, wherein the first acquired frame is determined to have useful and new information without correlating the acquired frame to partially reconstructed image, the because there is no prior acquired frame or partially reconstructed image for performing the correlation, and storing the first acquired frame as the partially reconstructed image.

67. A method as in claim 65, wherein the correlating comprises a frame matching correlation of the latest acquired useful frame to the partially reconstructed image is performed to determine the alignment registration of the latest acquired useful frame to the generated or reconstructed image.

68. A method as in claim 67, wherein said frame matching correlation comprises a frame matching normalized cross-correlation.

69. A method as in claim 68, wherein the frame matching normalized cross correlation NCC(R,S,d) of row R of the reconstructed image to row S of the current frame for a lag of d, is given by the expression:

70. A method as in claim 69, wherein NCC(R,S,d) is calculated for a plurality of values of d to find the one value of d that corresponds to the best fit since the lag of the information in the current acquired frame relative to the lag in the partially reconstructed image is not known beforehand.

71. A method as in claim 70, wherein NCC(R,S,d) is selected as the NCC(R,S,d) for which NCC(R,S,L) is equal to the maximum value of MAX{NCC(R,S,d) over the range of d from −

L to +L where L is the lag value, as follows;

PeakNCC(R,S,L)=MAX{NCC(R,S,d)} for d=−

L to d=L, and

the peak value of d (d_peak(R,S,L)) is equal to the value of d at which PeakNCC(R,S,L) is satisfied, that is;

d_peak(R,S,L)=the value of d at which the above equation is satisfied.

72. A method as in claim 71, wherein L is chosen so that it is at least as large as the maximum x-velocity (Δ

x(i)) that can occur from frame to frame.

73. A method as in claim 72, wherein L is chosen to be in the range of 10 to 50 frame columns.

74. A method as in claim 72, wherein L is chosen to be in the range of 20 to 30 frame columns.

75. A method as in claim 72, wherein L is chosen to be substantially 25 frame columns.

76. A method as in claim 71, wherein L is a function of the d_peak from the last frame acquisition and image generation reconstruction iteration i−

1.

77. A method as in claim 71, wherein L is chosen to be L(at iteration i)=d_peak (at iteration i−

1)+e, where e is an integer related to the maximum movement of the finger from one frame to the next frame.

78. A method as in claim 32, wherein the updating comprising generating a reconstructed image sequentially from the acquired frames.

79. A method as in claim 78, wherein generating the reconstructed image includes select the row S in of the current frame to be equal to the number of row N (S=N) so that there is a high confidence that if the user is not swiping the finger too quickly, row S of the reconstructed image will correlate and be a duplicate of one of the rows N of the current acquired frame.

80. A method as in claim 79, wherein said normalized cross-correlation calculation generates values for row S of the current frame as follows:

(i) bestMatchRow, the row of the reconstructed image that results in the highest correlation value;

(ii) MaxPeakNCC, the value of the correlation of the best matching row of the reconstructed image to the one in the current frame; and

(iii) d_peakMax, the correlation lag where MaxPeakNCC is reached.

81. A method as in claim 32, further comprising determining a fingertip swipe x-velocity and a fingertip swipe y-velocity for use in reconstructing a fingerprint image for fingerprint acquisition operation where the user swipes the finger too quickly for consecutive frames to overlap.

82. A method as in claim 81, wherein the determining a fingertip swipe x-velocity and a fingertip swipe y-velocity comprises a deterministic calculation based on measured values.

83. A method as in claim 81, wherein the determining a fingertip swipe x-velocity and a fingertip swipe y-velocity comprises an estimate based on prior historical velocity values.

84. A method as in claim 81, wherein the x-velocity Δ

x(i) at iteration i and the y-velocity Δ

y(i) at iteration i is determined differently for two different conditions;

(i) if the maximum peak NCC (MaxPeakNCC) is greater than the frame matching correlation threshold (corr_threshold), or MaxPeakNCC>

corr_threshold, then;

Δ

x(i)=d_peakMax and Δ

y(i)=N-(best Match Row); and

(ii) otherwise if MaxPeakNCC≦

corr_threshold), then;

the x-velocity is chosen to be the x-velocity of the previous iteration i−

1 (Δ

x(i)=Δ

x(i−

1)), and the y-velocity is chosen to be equal to N (Δ

y(i)=N), where N is the number of rows.

85. A method as in claim 84, where in the frame matching correlation threshold value (corr_threshold) is selected to be in the range from 0.6 to 0.99 for an NCC range of 0 and 1.0 or an equivalent range of movement detection normalized cross-correlation threshold for an NCC scaled and or offset by a scaling constant and/or an offset bias.

86. A method as in claim 81, wherein the x-velocity and y-velocity calculation is repeated to obtain information for some or all of the rows in the current frame.

87. A method as in claim 86, wherein said some of all of the rows in the current frame consists of row N of the current frame.

88. A method as in claim 86, wherein said some of all of the rows in the current frame comprise a plurality or rows of the current frame.

89. A method as in claim 88, wherein when said correlation calculation is performed for a plurality of rows, then at each frame acquisition and image reconstruction iteration i, a plurality of values of Δ

x(i) and Δ

y(i) for each frame row are obtained.

90. A method as in claim 89, wherein when a plurality of values of Δ

x(i) and Δ

y(i) for each frame row are obtained, a final pair of velocities used in the image reconstruction at this iteration i are calculated by taking the statistical mode of each above-threshold velocity, finalΔ

x(i) and final Δ

y(i) as;

Final Δ

x(i)=MODE{set of all Δ

x(i) where MaxPeakNCC>

corr_threshold, and Final Δ

y(i)=MODE{set of all Δ

y(i) where MaxPeakNCC>

corr_threshold}, unless there are no above-threshold velocities found in which situation the estimates are;

Final Δ

x(i)=Δ

x(i−

1), and Final Δ

y(i)=N.

91. A method as in claim 90, wherein the a Final Δ

x(i) and Final Δ

y(i) identify where the new frame belongs with respect to the reconstructed image and the reconstructed image is updated by adding the new frame to the previous partial reconstructed image to obtain a new reconstructed image that includes the additional acquired frame.

92. A method as in claim 32, further comprising, after the updating of the reconstructed image, updating reconstructed image statistics.

93. A method as in claim 92, wherein the reconstructed image statistics computed when a predetermined number of frames are added to the reconstructed image are selected from the set consisting of:

final Δ

x(i) and final Δ

y(i) of the current i^th frame relative to the reconstructed image;

Height(i)=Height(i−

1)+Δ

y(i), the reconstructed image height, equal to the new total number of rows in the partially reconstructed image;

i=total_frames_used and equal to the total number of iterations is equal to the total frames used thus far in the reconstruction;

the count of the number of iterations where the MaxPeakNCC correlation is below threshold;

the number of consecutive frames discarded due to noise;

the number of consecutive frames discarded due to no finger on sensor, and combinations thereof.

94. A method as in claim 93, wherein the reconstructed image statistics are used to stop the frame acquisition process.

95. A method as in claim 93, wherein the reconstructed image statistics are used to calculate a speed of swipe and an angle of the swipe.

96. A method as in claim 32, further comprising testing a frame acquisition stopping criteria to decide when to stop acquiring additional frames.

97. A method as in claim 96, wherein the stopping criteria comprises a frame based stopping criteria to terminate the frame acquisition process.

98. A method as in claim 97, wherein the frame based stopping criteria comprises a procedure wherein frame acquisition and image generation or reconstruction is stopped if:

(i) more than some number F of consecutive frames discarded due to noise, or (ii) more than some number G of consecutive frames have been discarded due to non-movement of the finger, or (iii) more than some number K of total frames have already been acquired.

99. A method as in claim 98, wherein F, G, and K are numbers that depend on the sensor frame rate and ensure that frame acquisition and image reconstruction systems operating at different frame rates behave similarly, since F, G and K are normalized to units of time and compensate for different frame rates.

100. A method as in claim 99, wherein the compensation for slower and faster systems facilitates comparable performance across many different systems, so that such frame acquisition and image reconstruction rate differences will not be readily apparent in operation to the person using the system.

101. A method as in claim 32, further comprising, after the determining that frame acquisition should be stopped, calculating post final image reconstruction information including calculation of a final height of the reconstructed image, an angle of swipe, and a speed of swipe.

102. A method as in claim 101, wherein the final height of the reconstructed image=Height(i)=H.

103. A method as in claim 101, wherein the angle of swipe=arctan[H/Σ

{Δ

x(i)}], where the sum or all of the x-velocities (Σ

{Δ

x(i)}) is the sum of the Δ

x(i) over all iterations where Δ

y(i)>

0.

104. A method as in claim 101, wherein the speed of swipe=average number of new rows added per frame=[Σ

{Δ

y(i)}/total_frames_used].

105. A method as in claim 32, further comprising embedding information into the reconstructed image.

106. A method as in claim 105, wherein information identifying characteristics of the biometric and its acquisition characteristics are attached stored in a token identified to the generated reconstructed image.

107. A method as in claim 105, wherein information identifying characteristics of the biometric and its acquisition are embedded into the generated reconstructed image.

108. A method as in claim 105, wherein the embedded information is embedded within a predetermined portion of the reconstructed image in place of selected image pixels.

109. A method as in claim 105, wherein the embedded information is embedded within the reconstructed image as a separate record.

110. A method as in claim 105, wherein the embedded information is embedded within a predetermined portion of the reconstructed image in place of image pixels.

111. A method as in claim 105, wherein the embedded information is selected from the set of information items consisting of:

a unique identifier enabling detection of the presence of the embedded information block in the reconstructed biometric image;

a record or header version identifier;

a sensor identifier including one or more of a sensor vendor identifier, a sensor model identifier, and a sensor type identifier;

a reconstructed image height;

a reconstructed image width;

an angle of swipe;

a swipe speed;

a set of x-velocity values at each row of the reconstructed image;

a bad correlation count identifying the number of iterations where the maximum peak normalized cross-correlation was below the correlation threshold value; and

combinations thereof.

112. A method as in claim 111, wherein the information further includes information about the type of processor or computer used, time information, date information, Cyclic Redundancy Check (CRC) codes to verify integrity of the data, and combinations thereof.

113. A method as in claim 32, further comprising acquiring a new frame and performing an analysis of the content of the acquired frame to determine if it contains any fingerprint biometric information;

said determination of whether there is any fingerprint information in a collected frame is an image statistic based determination using measured frame image statistics including an average value and a variance of at least a portion of the acquired frame;

said frame or partial frame average value M is given by the expression;

114. A computer readable medium encoded with a computer program which when executed performs a method for acquiring a plurality of biometric image frames from a sensor and generating a reconstructed composite image from at least some of said plurality of acquired biometric image frames, said method comprising:

(a) acquiring a frame from said sensor and storing the acquired frame in a memory as a last stored frame;

(b) comparing the stored frame to the reconstructed composite image to determine any usefulness and any alignment registration relationship between the acquired frame and said reconstructed composite image that is being generated;

(c) updating the generated reconstructed composite image to incorporate at least a portion of the acquired frame to extend the length (height) of the generated reconstructed composite image and storing the updated generated reconstructed composite image in a memory;

(d) determining if frame acquisition should be stopped according to a frame acquisition stop criteria; and

(e) if it is determined that frame acquisition should be stopped then stopping acquiring frames and identifying the then currently updated generated reconstructed composite image as the final generated reconstructed composite image, and otherwise repeating the procedure of acquiring additional frames through determining if frame acquisition should be stopped until it is determined that frame acquisition should be stopped.

115. A computer readable medium encoded with a computer program which when executed performs a method for generating a reconstructed image from a plurality of acquired biometric image frames, said method comprising:

acquiring a frame from said sensor and storing the acquired frame;

comparing the acquired frame to a partially reconstructed image to determine any usefulness and any alignment registration relationship between the acquired frame and said reconstructed composite image that is being generated;

updating the generated reconstructed image to incorporate at least a portion of the acquired frame to extend the length (height) of the generated reconstructed composite image and storing the updated generated reconstructed composite image in a memory;

determining if frame acquisition should be stopped according to a frame acquisition stop criteria; and

if it is determined that frame acquisition should be stopped then stopping acquiring frames and identifying the then currently updated generated reconstructed composite image as the final generated reconstructed composite image, and otherwise repeating the procedure of acquiring additional frames through determining if frame acquisition should be stopped until it is determined that frame acquisition should be stopped.

116. A system for generating a reconstructed biometric from a plurality of biometric image frames acquired from a biometric sensor, said system comprising:

means for acquiring a frame from said biometric sensor and storing the acquired frame;

means for comparing the acquired frame to a partially reconstructed image to determine any usefulness and any alignment registration relationship between the acquired frame and said reconstructed composite image that is being generated;

means for updating the generated reconstructed image to incorporate at least a portion of the acquired frame to extend the length of the generated reconstructed composite image and storing the updated generated reconstructed composite image in a memory;

means for determining if frame acquisition should be stopped according to a frame acquisition stop criteria;

means for stopping acquiring frames if it is determined that frame acquisition should be stopped and for identifying the then currently updated generated reconstructed composite image as the final generated reconstructed composite image; and

means for repeating the procedure of acquiring additional frames through determining if frame acquisition should be stopped until it is determined that frame acquisition should be stopped.

117. A system as in claim 116, wherein said biometric comprises a fingerprint biometric.

118. A system as in claim 116, wherein said biometric sensor comprises a biometric swipe sensor.

119. A system as in claim 116, wherein said means for acquiring, means for comparing, means for updating, means for determining, means for stopping, and means for repeating comprises at least one computer program stored in a memory and executing within a processor to generate said reconstructed image.

120. A system as in claim 116, wherein said biometric comprises a fingerprint biometric image.

121. A system as in claim 116, wherein said biometric comprises a fingerprint minutiae biometric.