ELECTROSTATICE CHUCK WITH ANTI-REFLECTIVE COATING, MEASURING METHOD AND USE OF SAID CHUCK

• US 20100046005A1
• Filed: 10/16/2007
• Published: 02/25/2010
• Est. Priority Date: 10/16/2006
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Stenzel, Olaf, Stöckl, Wieland, Kalkowski, Gerhard
• Granted Patent: US 8,243,286 B2
• Time in Patent Office: Days
• US Class Current: 356/604
• CPC Class Codes: G01B 11/2545 with one projection direction and several detection directions, e.g. stereo
• CPC Class Codes: G01C 11/06 by comparison of two or more pictures of the same area

Abstract

The invention relates to a device for the contactless detection of a three-dimensional contour, comprising a projector with an imaging element and a projection lens for depicting a stripe pattern that is generated on the imaging element in an object space. The invention further comprises a camera arrangement for the surveillance of the object space from two different directions, having two camera lenses. The projector and the camera arrangement are housed together in a measurement head that can be handheld. The invention further relates to a method for detecting a three-dimensional contour using said device.

Claims

1. A device for the contactless detection of a three-dimensional contour comprising:

a projector with an image-producing element and a projection lens for imaging a stripe pattern which can be generated on the image-producing element in an object space; and

a camera arrangement which includes two camera lenses for observing the object space from two different directions, wherein the projector and the camera arrangement are configured together in one measuring head which can be used as a hand-held device.

2. The device according to claim 1, wherein the camera arrangement has a common camera chip for both camera lenses, each of the camera lenses producing an image on respectively one half of the camera chip.

3. The device according to claim 2, wherein at least two tilted elements are disposed in a beam path of each of the two camera lenses, all the lenses of the camera lenses being disposed on an object side of the tilted elements and at least one first tilted element of the tilted elements being disposed out of the beam path of each of the two camera lenses on a displaceable slide for adjustment.

4. The device according to claim 1, wherein the two camera lenses have optical axes which enclose an angle of between 5°

and 20°

.

5. The device according to claim 1, wherein the two camera lenses have optical axes which are disposed in mirror symmetry relative to a plane in which an optical axis of the projection lens is situated.

6. The device according to claim 1, wherein the camera lenses and/or the projection lens is designed for an object-side sectional width of between 7 cm and 13 cm.

7. The device according to claim 1, wherein a light source is provided for the projector, light emanating from the light source being able to be modulated in intensity by the image-producing element which is configured to be transmissive or reflective.

8. The device according to claim 7, wherein the light source is accommodated in the measuring head or connected via a light guide to the measuring head.

9. The device according to claim 1, further comprising:

a control and evaluation unit for actuating the image-producing element and for evaluating image data produced by the camera arrangement, the control and evaluation unit being installed with programming technology, wherein the programming technology is configured to generate at least one stripe pattern on the image-producing element, to evaluate a course of phase values determined with the camera arrangement along mutually corresponding epipolar lines in image planes of both camera lenses with respect to constancy, to divide the epipolar lines into intervals of a constant phase course, to identify mutually corresponding intervals in the mutually corresponding epipolar lines, o identify mutually corresponding image points of the same phase values within the intervals identified as correlating with each other, and to triangulate an object point based on the identified image points which correspond to this object point and correlate with each other.

18. Use of a device according to claim 1 for implementing a method according to claim 10.

10. A method for the contactless detection of a three-dimensional contour comprising:

projecting at least one stripe pattern onto an object;

by means of two camera lenses disposed at a defined spacing relative to each other, recording two images of the object with the stripe pattern projected thereon from two different directions;

determining phase values of the stripe pattern for image points in both images;

determining, by means of triangulation based on respectively mutually corresponding image points in the two images, depth information for an object point corresponding to these image points,

wherein determining the mutually corresponding image points in the two images comprises;

selecting pairs of respectively mutually corresponding epipolar lines in the two images;

evaluating the determined phase values along the epipolar lines with respect to constancy;

dividing the epipolar lines into intervals of a constant phase course;

identifying mutually corresponding intervals in the mutually corresponding epipolar lines; and

within the mutually corresponding intervals, mutually assigning points of the same phase values.

11. The method according to claim 10, wherein a sequence of a plurality of mutually phase-shifted stripe patterns is projected in succession onto the object and recorded for determining the phase values.

12. The method according to claim 10, wherein at least one further stripe pattern with differently orientated stripes is projected onto the object in a temporally offset manner, phase values also of this further stripe pattern being evaluated in order to identify mutually corresponding image points in the two images.

13. The method according to claim 10, wherein at least one recording of the object is made my means of the two camera lenses, in the case of which at least one marking which is located in a defined manner relative to the simultaneously, previously or subsequently recorded stripe pattern is projected onto the object for identification of two corresponding image points, which assists the method, and/or for calibration of a device used for the method.

14. The method according to claim 10, wherein the evaluated epipolar lines are situated densely in the two images.

15. The method according to claim 10, wherein a subpixel-precise assignment of image points to phase values is effected by means of interpolation.

16. The method according to one claim 10, wherein all the stripe patterns used for detection of one contour and possibly additionally projected markings are recorded within between 100 ms and 500 ms and/or with an image repeat rate of between 15 Hz and 60 Hz.

17. The method according to claim 10, wherein the object concerns teeth, tooth models or dentures.