Finger Contact Detecting Apparatus, Finger Contact Detecting Method, Fingerprint Reading Apparatus and Fingerprint Reading Method

• US 20090087044A1
• Filed: 09/22/2008
• Published: 04/02/2009
• Est. Priority Date: 09/27/2007
• Status: Active Grant

• Current Assignee: Mitsumi Electric Co., Ltd. (Minebea Mitsumi, Inc.)
• Original Assignee: Mitsumi Electric Co., Ltd. (Minebea Mitsumi, Inc.)
• Inventors: Tahara, Yoshinori, Mizushima, Satoshi
• Granted Patent: US 8,131,027 B2
• Time in Patent Office: Days
• US Class Current: 382/124
• 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

Abstract

A finger contact detecting apparatus, which detects a finger being swept on a fingerprint sensor of the finger contact detecting apparatus, the finger contact detecting apparatus including, a pixel data averaging unit calculating an average value of pixel data collected by the fingerprint sensor; a deviation adding unit calculating, based on the average value and respective pixel data of predetermined pixels obtained by the fingerprint sensor, a summation of deviations of the respective pixel data of the predetermined pixels; and a finger contact detecting unit determining whether the finger is separated from the fingerprint sensor based on the summation of deviations and a predetermined threshold value.

Claims

1. A finger contact detecting apparatus, which detects a finger being swept on a fingerprint sensor,

the finger contact detecting apparatus comprising:

a pixel data averaging unit calculating an average value of pixel data collected by the fingerprint sensor;

a deviation adding unit calculating, based on the average value and respective pixel data of predetermined pixels obtained by the fingerprint sensor, a summation of deviations of the respective pixel data of the predetermined pixels; and

a finger contact detecting unit determining whether the finger is separated from the fingerprint sensor based on the summation of deviations and a predetermined threshold value.

2. The finger contact detecting apparatus as claimed in claim 1, wherein the fingerprint sensor includes a line sensor provided with plural pixels arranged in a line shape, the finger contact detecting unit compares the summation of deviations and the predetermined threshold value, and when a state where the summation of deviations is less than the predetermined threshold value continues for more than a predetermined number of lines, the fingerprint sensor determines that the finger is separated from the line sensor.

3. The finger contact detecting apparatus as claimed in claim 2, wherein the predetermined pixels include plural pixels arranged with a uniform separation on the line sensor.

4. A fingerprint reading apparatus comprising:

the finger contact detecting apparatus claimed in claim 1;

the fingerprint sensor; and

an image composing memory that records fingerprint image data collected by the fingerprint sensor and composes a fingerprint image.

5. A finger contact detecting method comprising the steps of:

(a) collecting pixel data of a fingerprint sensor while a finger is being swept on the fingerprint sensor;

(b) calculating an average value of the pixel data collected by the fingerprint sensor;

(c) calculating a summation of deviations based on the average value and respective pixel data of predetermined pixels obtained by the fingerprint sensor; and

(d) determining whether the finger is separated from the fingerprint sensor based on the calculated summation of deviations at step (c) and a predetermined threshold value.

6. The finger contact detecting method as claimed in claim 5, wherein the fingerprint sensor includes a line sensor provided with plural pixels arranged in a line shape, in step (d) comparing the summation of deviations and the predetermined threshold value, and when a state where the summation of deviations is less than the predetermined threshold value continues for more than a predetermined number of lines, the fingerprint sensor determines that the finger is separated from the line sensor.

7. The finger contact detecting method as claimed in claim 6, wherein the predetermined pixels includes plural pixels arranged with a uniform separation on the line sensor.

8. A computer-readable recording medium having instructions executable by a computer to execute a fingerprint reading method comprising the steps of:

collecting fingerprint image data while a finger is being swept on a fingerprint sensor; and

performing the finger contact detecting method of claim 5;

wherein when the finger is detected as being separated from the fingerprint sensor after executing the step of performing the finger contact detecting method, the step of collecting fingerprint image data is terminated.