Fingerprint image reading apparatus

• US 7,480,397 B2
• Filed: 04/14/2004
• Issued: 01/20/2009
• Est. Priority Date: 04/18/2003
• Status: Expired due to Fees

• Current Assignee: Casio Computer Company Limited
• Original Assignee: Casio Computer Company Limited
• Inventors: Ide, Hiroyasu
• Primary Examiner(s): Ahmed; Samir A
• Assistant Examiner(s): VANCHY JR, MICHAEL J
• Application Number:
  US10/825,556
• Publication Number:
  US 20040208349A1
• Time in Patent Office: 1,742 Days
• Field of Search: 382/124, 382/115
• US Class Current: 382/124
• CPC Class Codes: A61B 5/1172 using fingerprinting
• CPC Class Codes: G06V 40/1324 by using geometrical optics, e.g. using prisms G06V40/1312 takes precedence
• 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: H04N 1/00827 Arrangements for reading an image from an unusual original, e.g. 3-dimensional objects
• CPC Class Codes: H04N 1/121 Feeding arrangements transporting sheets to or from the scanning position H04N1/0057; control or error compensation of sub-scanning velocity H04N1/0473
• CPC Class Codes: H04N 1/193 using electrically scanned linear arrays , e.g. linear CCD arrays

Abstract

An image reading apparatus which reads a fingerprint image, includes a roller rotatably mounted to the image reading apparatus, a given pattern being printed on part of an outer surface of the roller in a circumferential direction, a line sensor including a plurality of image pickup elements which read a fingerprint image from a finger that touches with the roller as well as the pattern printed on the roller, a generating unit which generates a reference value to each of the image pickup elements corresponding to part of the line sensor, which reads the pattern, based on image data of the pattern, a rotation sensing image extracting unit which extracts a rotation sensing image based on the reference value, and a determination unit which determines capture timing of the fingerprint image based on variations in the rotation sensing image.

Claims

1. A fingerprint image processing apparatus comprising:

a line sensor including a plurality of image pickup elements;

a pixel value detecting unit which detects a respective maximum value and a respective minimum value from fingerprint image data output from each of the image pickup elements;

a pixel value range detecting unit which detects a pixel value range between the respective maximum value and the respective minimum value detected by the pixel value detecting unit for the fingerprint image data read by each of the image pickup elements;

a normalized data generating unit which generates, for each pixel of the fingerprint image data, normalized data that indicates a ratio of a pixel value of the pixel to the pixel value range corresponding to the image pickup element which read the pixel;

a normalized data average calculating unit which calculates averages, corresponding respectively to the image pickup elements, of the normalized data generated by the normalized data generating unit from the fingerprint image data read by the respective image pickup elements; and

a pixel value correcting unit which corrects a pixel value of each of the pixels of the fingerprint image data based on;

(i) the average calculated by the normalized data average calculating unit corresponding to the image pickup element which read the pixel, and (ii) a maximum possible pixel value of the pixels.

2. The apparatus according to claim 1, wherein the pixel value detecting unit comprises:

a designated value recording unit which records a designated value that indicates an order of the pixel values of the pixels of the fingerprint image data output from the image pickup elements;

a unit which determines, as the respective maximum value for the fingerprint image data from each of the image pickup elements, a pixel value of a pixel of the fingerprint image data output from the image pickup element that is an x-th largest pixel value recorded by the designated value recording unit, which is determined with reference to a maximum value detected from the fingerprint image data output from the image pickup element, and which determines, as the respective minimum value for the fingerprint image data from each of the image pickup elements, a pixel value of a pixel of the fingerprint image data output from the image pickup element that is a y-th smallest pixel value recorded by the designated value recording unit, which is determined with reference to a minimum value detected from the fingerprint image data output from the image pickup element.

3. The apparatus according to claim 1, wherein the pixel value detecting unit includes:

a designated value recording unit which records a designated value that indicates an order of the pixel values of the pixels of the fingerprint image data output from the image pickup elements;

a unit which determines, as the respective maximum value for the fingerprint image data from each of the image pickup elements, an average of pixel values from a maximum pixel value detected from the fingerprint image data output from the image pickup element to an x-th pixel value recorded by the designated value recording unit, which is determined with reference to a minimum value detected from the fingerprint image data output from the image pickup element, and which determines, as the respective minimum value for the fingerprint image data from each of the image pickup elements, an average of pixel values from a minimum pixel value detected from the fingerprint image data output from the image pickup element to a y-th pixel value recorded by the designated value recording unit, which is determined with reference to a minimum value detected from the fingerprint image data output from the image pickup element.

4. The apparatus according to claim 1, further comprising a hollow transparent roller which is rotatably mounted at a main body of the image processing apparatus, and wherein the line sensor is fixed in the roller.

5. The apparatus according to claim 4, wherein the line sensor reads a fingerprint image of a finger that is in contact with the roller to obtain the fingerprint image data.

6. A method of processing fingerprint image data, which is captured by a line sensor that includes a plurality of image pickup elements, and each pixel of the fingerprint image data having a multilevel pixel value, the method comprising:

detecting a respective maximum value and a respective minimum pixel value from the fingerprint image data captured by each of the image pickup elements of the line sensor;

detecting a pixel value range between the respective maximum value and the respective minimum value for the fingerprint image data captured by each of the image pickup elements;

generating, for each pixel of the fingerprint image data, normalized data that indicates a ratio of a pixel value of the pixel to the pixel value range corresponding to the image pickup element which read the pixel;

calculating averages of the normalized data corresponding respectively to the image pickup elements; and

correcting a pixel value of each of the pixels of the fingerprint image data based on;

(i) the average corresponding to the image pickup element which read the pixel, and (ii) a maximum possible pixel value of each of the pixels.

7. The method according to claim 6, wherein the pixel value detecting includes:

recording a designated value that indicates an order of the pixel values of the pixels of the fingerprint image data output from the image pickup elements;

determining, as the respective maximum value for the fingerprint image data from each of the image pickup elements, a pixel value of a pixel of the fingerprint image data output from the image pickup element that is an x-th largest pixel value indicated by the designated value, which is determined with reference to a maximum value detected from the fingerprint image data output from the image pickup element; and

determining, as the respective minimum value for the fingerprint image data from each of the image pickup elements, a pixel value of a pixel of the fingerprint image data output from the image pickup element that is a y-th smallest pixel indicated by the designated value, which is determined with reference to a minimum value detected from the fingerprint image data output from the image pickup element.

8. The method according to claim 6, wherein the pixel value detecting includes:

recording a designated value that indicates an order of the pixel values of the pixels of the fingerprint image data output from the image pickup elements;

determining, as the respective maximum value for the fingerprint image data from each of the image pickup elements, an average of pixel values from a maximum pixel value detected from the fingerprint image data output from the image pickup element to an x-th pixel value indicated by the designated value, which is determined with reference to a maximum value detected from the fingerprint image data output from the image pickup element; and

determining, as the respective minimum value for the fingerprint image data from each of the image pickup elements, an average of pixel values from a minimum pixel value detected from the fingerprint image data output from the image pickup element to a y-th pixel value indicated by the designated value, which is determined with reference to a minimum value detected from the fingerprint image data output from the image pickup element.

9. The method according to claim 6, further comprising capturing a fingerprint image by the line sensor to obtain the fingerprint image data.