Fingerprint detection using sweep-type imager with optoelectronic speed sensor

• US 20070086629A1
• Filed: 08/30/2004
• Published: 04/19/2007
• Est. Priority Date: 09/11/2003
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Duijve, Rene, Riemschneider, Karl-Ragmar, Hase, Thomas, Drews, Steffan
• Granted Patent: US 7,706,581 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

In a method and an arrangement for detecting skinprints, in particular fingerprints, it is provided that at least one strip sensor comprising at least one elongate narrow sensor line detects the structure of the fingertip when the fingertip passes over the strip sensor, that at least one optoelectronic speed sensor continuously determines the finger movement, that the fingertip is moved over at least one optoelectronic speed sensor and the strip sensor, and that the determined finger movement is used to correct an image of the finger structure that has been distorted as a result of non-uniform movement. Preferably, the speed sensor evaluates the Doppler shift of a modulation of the modulated laser light reflected at the moved finger surface.

Claims

1. A method of detecting skinprints, in particular fingerprints, characterized in that

a) at least one strip sensor comprising at least one elongate narrow sensor line detects the structure of the fingertip when the fingertip passes over the strip sensor,

b) at least one optoelectronic speed sensor continuously determines the finger movement,

c) the fingertip is moved over at least one optoelectronic speed sensor and the strip sensor, and

d) the determined finger movement is used to correct an image of the finger structure that has been distorted as a result of non-uniform movement.

2. A method as claimed in claim 1, characterized in that the optoelectronic speed sensor evaluates the Doppler shift of a modulation of the modulated laser light reflected at the moved finger surface.

3. A method as claimed in claim 1, characterized in that the correction is applied to a biometric data record derived from the distorted image.

4. A method as claimed in claim 1, characterized in that in order to detect the finger movement

a) in a first movement phase firstly only part regions of the fingertip pass over the strip sensor and are detected as images,

b) in one of the subsequent movement phases further regions of the fingertip pass over the strip sensor and are detected as images, and

c) these movement phases have considerably different directions and/or are separated by intermediate movement phases of considerably different directions, at least part of the spatial allocation of the image information taking place when the image is constructed through the detected finger movement in the movement phases.

5. A method as claimed in claim 1, characterized in that the determined involuntary finger movement is used as an additional feature besides the biometric features of the fingertip for identifying person.

6. A method as claimed in claim 1, characterized in that

a) a movement sequence takes place such that

b) the same regions of the fingertip pass over the strip sensor a number of times and are detected as images, and

c) the image information detected a number of times for one region is taken into account for image improvement purposes, at least part of the spatial allocation of the image information taking place through the detected movement sequence.

7. A method as claimed in claim 6, characterized in that the finger movement is carried out by the user with a characteristic sequence of movements, and in that the determined finger movement is compared with a stored finger movement.

8. A method as claimed in claim 7, characterized in that the stored finger movement is typical for the user and the user is thus identified.

9. A method as claimed in claim 7, characterized in that the detecting unit is switched into various operating states by different results during the detection of the finger movement.

10. A method as claimed in claim 1, characterized in that the passing over of the settable movement distance determined by the speed sensor triggers image detection of a new line by the strip sensor.

11. A method as claimed in claim 1, characterized in that the address of an image point for storing the image of the fingerprint in a storage medium depends on the determined finger movement.

12. A method as claimed in claim 1, characterized in that the determined finger movement is used to calculate and/or select the coefficients of non-symmetrical, orientation-selective spatial filters, and in that the spatial filters perform corrections of the movement directions during processing of the image.

13. A method as claimed in claim 1, characterized in that the determined finger movement is used to calculate and/or select the coefficients of spatial filters, and in that the spatial filters perform corrections of the different movement distances during processing of the finger image.

14. A method as claimed claim 1, characterized in that the finger movement is determined simultaneously on various part-surfaces of the fingertip, and in that a proportional rotary movement (rotation) in that plane of image recording is calculated therefrom.

15. A method as claimed in claim 1, characterized in that movement information from various part-surfaces of the fingertip is determined simultaneously and taken into account separately for the part-surfaces.

16. A method as claimed in claim 1, characterized in that the finger movement of various part-surfaces of the fingertip is determined simultaneously and an excessively highly pronounced deformation and/or a measurement error is identified when the determined finger movements of the part-surfaces differ considerably from those which would be possible as a result of a rotation and/or displacement with plausible parameters.

17. A method as claimed in claim 1, characterized in that the correction of the image by means of the determined finger movement comprises the following part-calculations:

a) conversion of the positions of the image points from a representation that is not necessarily equidistant on account of non-uniform movement to a spatially highly resolved representation (oversampling) and in accordance with spatial filtering with low-pass effect, and

b) conversion into a representation that is reduced again but reliably equidistant (resampling).

18. A method as claimed in claim 1, characterized in that the laser light emitted by the speed sensor and reflected is furthermore used to determine chemical properties from the color line spectrum of the light component reflected by the finger.

19. A method as claimed in claim 18, characterized in that a determination of the concentration of dissolved and bound gases in the blood—

such as the blood oxygen content or carbon dioxide content—

is carried out.

20. An arrangement for detecting skinprints, in particular fingerprints, characterized in that a least one optoelectronic speed sensor is located within at most a few millimeters of a strip sensor and on a surface at a point provided for detecting the fingerprint.

21. An arrangement as claimed in claim 20, characterized in that at least one optoelectronic speed sensor and the strip sensor form a compact assembly.

22. An arrangement as claimed in claim 20, characterized in that at least one optoelectronic speed sensor is used at the same time as an input device for operating functions.

23. An arrangement as claimed in claim 20, characterized in that a light source of the optoelectronic speed sensor is at the same time an illumination device of the speed sensor.

24. An arrangement as claimed in claim 20, characterized in that the light source of the optoelectronic speed sensor is used at the same time as a device for outputting signals to the user.

25. An arrangement as claimed in claim 20, characterized in that the optoelectronic speed sensor and the strip sensor are applied to elastic support material, as a result of which a finger bearing surface formed by the support material is flexible at least in the transverse direction with respect to the strip sensor.

26. An arrangement as claimed in claim 20, characterized in that it is part of a device for mobile communication.

27. An arrangement as claimed in claim 20, characterized by a configuration such that it can be guided over the surface of body parts for the purpose of detecting skinprints.