Device, method and system for generating dynamic projection patterns in a confocal camera

Patent metadata

Field	Value
Publication number	US-10753734-B2
Application number	US-201816003628-A
Country	US
Kind code	B2
Filing date	Jun 8, 2018
Priority date	Jun 8, 2018
Publication date	Aug 25, 2020
Grant date	Aug 25, 2020

Abstract

A device, method and system for utilizing an optical array generator, confocal measurement/depth of focus techniques to generate dynamic patterns in a camera for projection onto the surface of an object for three-dimensional (3D) measurement. Projected light patterns are used to generate optical features on the surface of an object to be measured and optical 3D measuring methods which operate according to triangulation, confocal and depth of focus principles are used to measure the object.

First claim

What is claimed is:

1. A camera, comprising:
an optical array generator for generating a plurality of dynamic patterns for projection, the optical array generator further comprising:
a light source including a plurality of discrete regions wherein a luminous intensity of each of the plurality of discrete regions is controlled independently,
a lens array comprising a plurality of lenses, and
a collimator having a single optical axis, said collimator with the single optical axis constructed to direct light of the light source to the plurality of lenses such that each lens of the plurality of lenses that is illuminated by light from the light source, images said light of the light source onto an image plane of the lens array in order to produce the plurality of dynamic patterns;

an imaging sensor arranged within the camera to record a plurality of reflected images from a surface of an object to be measured;
a variable imaging optics arranged within the camera to focus the plurality of dynamic patterns onto the surface of the object and to image the plurality of reflected images onto the imaging sensor;
wherein the variable imaging optics is constructed such that a depth of focus of the variable imaging optics is varied during projection or imaging so that features of the plurality of dynamic patterns are projected onto the object with maximum contrast at the depth of focus or features of the plurality of reflected images are imaged onto the sensor with maximum contrast at the depth of focus.

2. The camera of claim 1 , wherein the light source is selected from the group consisting of LED dies, laser diodes and an end of a plurality of optical fibers that have other light sources attached to the other end.

3. The camera of claim 1 , wherein the light source includes at least three discrete regions.

4. The camera of claim 1 , wherein the depth of focus of the variable imaging optics is substantially smaller than a thickness of the object.

5. The camera of claim 1 , wherein the imaging sensor is constructed to perform in-pixel demodulation.

6. The camera of claim 1 , wherein the dynamic patterns are complementary checkerboard patterns or complementary stripe patterns.

7. The camera of claim 1 , wherein each of the plurality of lenses is cylindrical.

8. A method for generating a plurality of dynamic patterns for measuring an object, the method comprising:
providing a collimator with a single optical axis;
electronically controlling the luminous intensities of each of a plurality of discrete regions of a light source to generate structured light for said collimator;
directing the structured light from the light source to a plurality of lenses of a lens array using the collimator;
producing sub-images of the structured light using each lens of the plurality of lenses that is illuminated by light from the light source such that the sub-images are formed in an image plane of the lens array to form the plurality of dynamic patterns;
varying a depth of focus of the variable imaging optics during projection or imaging so that features of the plurality of dynamic patterns are projected onto the object with maximum contrast at the depth of focus or features of a plurality of reflected images are imaged onto an imaging sensor with maximum contrast at the depth of focus.

9. The method of claim 8 , further comprising the step of recording the plurality of reflected images from the surface of the object with the imaging sensor to create an image stack.

10. The method of claim 9 , further comprising processing the plurality of reflected images to obtain a three-dimensional image of the object by determining for each sensor pixel, a maximum amplitude across the image stack.

11. The method of claim 9 , further comprising processing the plurality of reflected images to obtain a three-dimensional image of the object by determining a variable imaging optics position that produces the maximum contrast of the dynamic pattern for a region of the object.

12. The method of claim 8 , further comprising aligning the lens array with pixels of the imaging sensor by displacing the light source such that the dynamic patterns in the image plane of the lens array are also shifted.

13. The method of claim 8 , further comprising performing lateral fine adjustment by using a magnification of the optical array generator wherein a required alignment accuracy of the lens array is reduced to an alignment accuracy of the light source.

14. A system for generating a plurality of dynamic patterns for measuring an object, the system comprising:
at least one processor operable to:
electronically control the luminous intensities of each of a plurality of discrete regions of a light source to generate structured light for a collimator that is constructed to have a single optical axis;
direct the structured light from the light source to a plurality of lenses a lens array using the collimator having the single optical axis;
produce sub-images of the structured light using each lens of the plurality of lenses that is illuminated by light from the light source such that the sub-images are formed in an image plane of the lens array to form the plurality of dynamic patterns;
vary a depth of focus of the variable imaging optics during projection or imaging so that features of the plurality of dynamic patterns are projected onto the object with maximum contrast at the depth of focus or features of a plurality of reflected images are imaged onto an imaging sensor with maximum contrast at the depth of focus.

Assignees

• Dentsply Sirona Inc

Inventors

• Tewes Michael
• Berner Markus

Classifications

• A61B1/00194

  adapted for three-dimensional imaging · CPC title

• G02B21/0032

  Optical details of illumination, e.g. light-sources, pinholes, beam splitters, slits, fibers (G02B21/0036 - G02B21/008; means for illumination of specimens in general G02B21/06) · CPC title

• G01B11/2518

  Projection by scanning of the object · CPC title

• G01B11/2513 Primary

  with several lines being projected in more than one direction, e.g. grids, patterns · CPC title

• G01B11/24

  for measuring contours or curvatures · CPC title