# US 9,752,867 B2 · Chromatic confocal system

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- Number: US 9,752,867 B2
- Document ID: US9752867B2
- Status: Granted
- Kind: B2
- Application number: 14/980,337
- Filed: 2015-12-28
- Published: 2016-04-21
- Granted: 2017-09-05
- Earliest claimed: 2014-07-03
- Assignees: Align Technology, Inc.
- Applicants: Align Technology, Inc.
- Inventors: Yossef Atiya; Tal Verker
- Web page: https://patentgrep.com/patent/US9752867B2

## CPC

- 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})
- A61B 1/00009: {of image signals during a use of endoscope}
- A61B 1/00194: {adapted for three-dimensional imaging}
- A61B 1/04: combined with photographic or television appliances
- A61B 1/06: with illuminating arrangements
- A61B 1/0605: {for spatially modulated illumination}
- A61B 1/0638: {providing two or more wavelengths}
- A61B 1/24: for the mouth, i.e. stomatoscopes, e.g. with tongue depressors; Instruments for opening or keeping open the mouth
- A61B 5/0088: {for oral or dental tissue}
- A61B 5/1076: {for measuring dimensions inside body cavities, e.g. using catheters (A61B3/1005 takes precedence)}
- A61B 5/1079: {using optical or photographic means}
- A61B 5/4547: {Evaluating teeth}
- A61C 1/088: {Illuminating devices or attachments (for examination of the mouth A61B1/24 and A61B1/06)}
- A61C 9/006: {projecting one or more stripes or patterns on the teeth}
- A61C 9/0066: {Depth determination through adaptive focusing}
- G01B 11/24: for measuring contours or curvatures
- G01B 2210/50: Using chromatic effects to achieve wavelength-dependent depth resolution
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- A61C: DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE (non-driven toothbrushes A46B; {tongue scrapers A61B17/24;} preparations for dentistry A61K6/00; preparations for cleaning the teeth or mouth A61K8/00, A61Q11/00)

## Abstract

A system for determining surface topography of a three-dimensional structure is provided. The system can include an illumination unit configured to output a two-dimensional array of light beams each comprising a plurality of wavelengths. An optical assembly can focus the plurality of wavelengths of each light beam to a plurality of focal lengths so as to simultaneously illuminate the structure over a two-dimensional field of view. A detector and a processor are used to generate data representative of the surface topography of the three-dimensional structure based on the measured characteristics of the light reflected from the structure.

## Claims

### Claim 1

A system for measuring surface topography of a three-dimensional structure, the system comprising:
an illumination unit configured to output a two-dimensional array of light beams each comprising a plurality of wavelengths;
an optical assembly operatively coupled to the illumination unit and configured to focus the plurality of wavelengths of each light beam to a plurality of focal lengths relative to the optical assembly so as to simultaneously illuminate the three-dimensional structure over a two-dimensional field of view, wherein the plurality of focal lengths is fixed relative to the optical assembly during the measuring of the surface topography; and
a detector configured to measure a characteristic of light reflected from the three-dimensional structure for each of a plurality of locations distributed in two dimensions over the two-dimensional field of view.

### Claim 2 (depends on 1)

The system of claim 1, wherein the characteristic comprises an intensity.

### Claim 3 (depends on 1)

The system of claim 1, wherein the plurality of wavelengths comprises wavelengths from 400 nm to 800 nm.

### Claim 4 (depends on 1)

The system of claim 1, wherein the plurality of wavelengths comprises at least three spectral bands, and wherein the at least three spectral bands comprise overlapping wavelengths of light.

### Claim 5 (depends on 1)

The system of claim 1, wherein the plurality of wavelengths comprises a continuous spectrum of wavelengths.

### Claim 6 (depends on 1)

The system of claim 1, wherein the two-dimensional array of light beams forms a two-dimensional array of spots on the three-dimensional structure over the two-dimensional field of view, and wherein a ratio of pitch to spot size for the two-dimensional array of spots is configured to inhibit cross-talk between the two-dimensional array of spots.

### Claim 7 (depends on 1)

The system of claim 1, wherein the optical assembly is configured to focus the light beams of the two-dimensional array to the plurality of focal lengths using at least one optical component with longitudinal chromatic aberration.

### Claim 8 (depends on 1)

The system of claim 1, wherein the plurality of focal lengths covers a depth of at least 20 mm.

### Claim 9 (depends on 2)

The system of claim 2, wherein the detector comprises a plurality of sensor elements distributed over a surface area configured to receive the light reflected from the three-dimensional structure over the two-dimensional field of view.

### Claim 10 (depends on 9)

The system of claim 9, wherein each sensor element of the plurality of sensor elements is configured to measure the intensity of at least one wavelength of the light reflected from the three-dimensional structure.

### Claim 11 (depends on 10)

The system of claim 10, wherein the plurality of sensor elements comprises a plurality of red sensor elements, a plurality of green sensor elements, and a plurality of blue sensor elements; each of the plurality of red sensor elements being configured to measure the intensity of a red light wavelength, each of the plurality of green sensor elements being configured to measure the intensity of a green light wavelength, and each of the plurality of blue sensor elements being configured to measure the intensity of a blue light wavelength.

### Claim 12 (depends on 11)

The system of claim 11, wherein the plurality of sensor elements are arranged in a Bayer pattern or in a plurality of layers.

### Claim 13 (depends on 1)

The system of claim 1, wherein the optical assembly is configured to focus the plurality of wavelengths to the plurality of focal lengths to a depth within a range from 10 mm to 30 mm relative to the optical assembly without relative movement of components of the optical assembly and components of the illumination unit.

### Claim 14

A method for measuring surface topography of a three-dimensional structure, the method comprising:
generating a two-dimensional array of light beams each comprising a plurality of wavelengths;
focusing the plurality of wavelengths of each light beam to a plurality of focal lengths relative to the three-dimensional structure so as to simultaneously illuminate the three-dimensional structure over a two-dimensional field of view, wherein the plurality of focal lengths is fixed relative to the optical assembly during the measuring of the surface topography; and
measuring a characteristic of light reflected from the three-dimensional structure for each of a plurality of locations distributed in two dimensions over the two-dimensional field of view.

### Claim 15 (depends on 14)

The method of claim 14, wherein the characteristic comprises an intensity.

### Claim 16 (depends on 14)

The method of claim 14, wherein the plurality of wavelengths comprises wavelengths from 400 nm to 800 nm.

### Claim 17 (depends on 14)

The method of claim 14, wherein the plurality of wavelengths comprises at least three spectral bands, and wherein the at least three spectral bands comprise overlapping wavelengths of light.

### Claim 18 (depends on 14)

The method of claim 14, wherein the plurality of wavelengths comprises a continuous spectrum of wavelengths.

### Claim 19 (depends on 14)

The method of claim 14, wherein the two-dimensional array of light beams forms a two-dimensional array of spots on the structure over the two-dimensional field of view, and wherein a ratio of pitch to spot size for the two-dimensional array of spots is selected to inhibit cross-talk between the two-dimensional array of spots.

### Claim 20 (depends on 14)

The method of claim 14, wherein the light beams of the two-dimensional array are focused to the plurality of focal lengths using at least one optical component with longitudinal chromatic aberration.

### Claim 21 (depends on 14)

The method of claim 14, wherein the plurality of focal lengths covers a depth of at least 20 mm.

### Claim 22 (depends on 15)

The method of claim 15, wherein the intensity of the light reflected from the three-dimensional structure is measured using a detector comprising a plurality of sensor elements distributed over a surface area configured to receive the light reflected from the three-dimensional structure over the two-dimensional field of view.

### Claim 23 (depends on 22)

The method of claim 22, wherein each sensor element of the plurality of sensor elements is configured to measure the intensity of at least one wavelength of the light reflected from the three-dimensional structure.

### Claim 24 (depends on 23)

The method of claim 23, wherein the plurality of sensor elements comprises a plurality of red sensor elements, a plurality of green sensor elements, and a plurality of blue sensor elements; each of the plurality of red sensor elements being configured to measure the intensity of a red light wavelength, each of the plurality of green sensor elements being configured to measure the intensity of a green light wavelenath, and each of the plurality of blue sensor elements being configured to measure the intensity of a blue light wavelength.

### Claim 25 (depends on 24)

The method of claim 24, wherein the plurality of sensor elements are arranged in a Bayer pattern or in a plurality of layers.

### Claim 26 (depends on 14)

The method of claim 14, wherein the focusing of the plurality of wavelengths to the plurality of focal lengths to a depth within a range from 10 mm to 30 mm is performed without relative movement of components of an optical assembly and components of an illumination unit.