Confocal surface topography measurement with fixed focal positions

• US 9,939,258 B2
• Filed: 05/12/2017
• Issued: 04/10/2018
• Est. Priority Date: 07/03/2014
• Status: Active Grant

• Current Assignee: Align Technology Incorporated
• Original Assignee: Align Technology Incorporated
• Inventors: Lampert, Erez, Levin, Adi, Verker, Tal
• Primary Examiner(s): Punnoose, Roy M
• Application Number:
  US15/593,680
• Publication Number:
  US 20170248412A1
• Time in Patent Office: 333 Days
• Field of Search: 356601
• CPC Class Codes: A61C 9/0053 Optical means or methods, e.g. scanning the teeth by a laser or light beam
• CPC Class Codes: A61C 9/006 projecting one or more stripes or patterns on the teeth
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01B 11/25 by projecting a pattern, e.g. one or more lines, moiré fringes on the object G01B11/255 takes precedence ; image analysis for depth or shape recovery G06T7/50
• CPC Class Codes: G01B 11/2513 with several lines being projected in more than one direction, e.g. grids, patterns
• CPC Class Codes: G01B 11/2518 Projection by scanning of the object
• CPC Class Codes: G01B 11/303 using photoelectric detection means
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• CPC Class Codes: G02B 21/0028 specially adapted for specific applications, e.g. for endoscopes, ophthalmoscopes, attachments to conventional microscopes
• CPC Class Codes: G02B 21/006 focusing arrangements; selection of the plane to be imaged
• CPC Class Codes: G02B 23/2461 Illumination
• CPC Class Codes: G02B 23/26 using light guides for illumination G02B23/2469
• CPC Class Codes: G02B 3/0056 arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses G02B3/0043 takes precedence; miniaturised objectives for electronic devices employing wafer level optics G02B13/0085

Abstract

An apparatus is described for measuring surface topography of a three-dimensional structure. In many embodiments, the apparatus is configured to focus each of a plurality of light beams to a respective fixed focal position relative to the apparatus. The apparatus measures a characteristic of each of a plurality of returned light beams that are generated by illuminating the three-dimensional structure with the light beams. The characteristic is measured for a plurality of different positions and/or orientations between the apparatus and the three-dimensional structure. Surface topography of the three-dimensional structure is determined based at least in part on the measured characteristic of the returned light beams for the plurality of different positions and/or orientations between the apparatus and the three-dimensional structure.

Claims

1. An apparatus for measuring surface topography of a three-dimensional structure, the apparatus comprising:

an optical probe moveable relative to the three-dimensional structure;

an illumination unit configured to generate a plurality of incident light beams, each of the plurality of incident light beams comprising a first wavelength component;

an optical system configured to focus the first wavelength component of each of the plurality of incident light beams to a respective fixed focal position relative to the optical probe while measuring the surface topography; and

a detector unit configured to measure a plurality of returned light beams that are generated by illuminating the three-dimensional structure with the plurality of incident light beams in order to measure the surface topography.

2. The apparatus of claim 1, wherein the detector unit comprises a two-dimensional array of sensor elements from a corresponding returned light beam of the plurality of returned light beams.

3. The apparatus of claim 2, wherein the optical system is configured to form a two-dimensional pattern of the plurality of incident light beams from light generated by the illumination unit, the two-dimensional pattern of the plurality of incident light beams corresponding to the plurality of returned light beams measured by the two-dimensional array of sensor elements.

4. The apparatus of claim 3, wherein the optical system comprises an optics expander unit configured to expand light generated by the illumination unit to form the two-dimensional pattern of the plurality of incident light beams.

5. The apparatus of claim 2, wherein the illumination unit is configured to produce a two-dimensional pattern of the plurality of incident light beams corresponding to the plurality of returned light beams measured by the two-dimensional array of sensor elements.

6. The apparatus of claim 2, wherein:

the plurality of incident light beams are arranged in a plurality of rows having a first row and a last row;

incident light beams in each row are focused to a respective common focal length; and

the respective common focal lengths of the first row and the last row are different by a predetermined length.

7. The apparatus of claim 6, wherein the predetermined length is from 5 mm to 25 mm.

8. The apparatus of claim 2, wherein the two-dimensional array of sensor elements is arranged in a plane that is oriented for confocal sensing of the plurality of returned light beams relative to focal lengths of the first wavelength component of the plurality of incident light beams.

9. The apparatus of claim 8, wherein the plane of the two-dimensional array of sensor elements is non-orthogonal to the plurality of returned light beams.

10. The apparatus of claim 1, wherein the optical system is configured to focus the first wavelength component of the plurality of incident light beams to at least 10 different focal lengths relative to the scanner, and wherein the at least 10 different focal lengths have a range of at least 10 mm.

11. A method of measuring surface topography of a three-dimensional structure, the method comprising:

focusing a first wavelength component of each of a plurality of incident light beams to a respective fixed focal position relative to an optical probe while measuring the surface topography; and

measuring a plurality of returned light beams that are generated by illuminating the three-dimensional structure with the plurality of incident light beams for one or more of a plurality of different relative positions or a plurality of different orientations between the optical probe and the three-dimensional structure in order to measure the surface topography.

12. The method of claim 11, comprising tracking changes in one or more of relative position or orientation between the optical probe and the three-dimensional structure.

13. The method of claim 12, wherein:

the plurality of incident light beams are arranged in a plurality of rows having a first row and a last row;

incident light beams in each row are focused to a respective common focal length; and

the respective common focal lengths of the first row and the last row are different by a predetermined length.

14. The method of claim 13, wherein the predetermined length is at least 10 mm.

15. The method of claim 12, wherein the first wavelength component of the plurality of incident light beams is focused to at least 10 different focal lengths relative to the scanner, and wherein the at least 10 different focal lengths have a range of at least 10 mm.

16. The method of claim 11, further comprising generating the plurality of incident light beams.

17. The method of claim 16, wherein the measuring step is performed using a two-dimensional array of sensor elements, each sensor element of the two-dimensional array of sensor elements being configured to measure a corresponding returned light beam of the plurality of returned light beams.

18. The method of claim 17, wherein the plurality of incident light beams are generated as a two-dimensional pattern, and the two-dimensional pattern of the plurality of incident light beams corresponds to the plurality of returned light beams measured by the two-dimensional array of sensor elements.