# US 9,436,868 B2 · Object classification for measured three-dimensional object scenes

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- Number: US 9,436,868 B2
- Document ID: US9436868B2
- Status: Granted
- Kind: B2
- Application number: 13/217,652
- Filed: 2011-08-25
- Published: 2012-03-15
- Granted: 2016-09-06
- Earliest claimed: 2010-09-10
- Assignees: Dimensional Photonics International, Inc.
- Applicants: Robert F. Dillon; Bing Zhao
- Inventors: Robert F. Dillon; Bing Zhao
- Web page: https://patentgrep.com/patent/US9436868B2

## CPC

- G06V 20/64: Three-dimensional [3D] objects
- A61B 1/0605: {for spatially modulated illumination}
- A61C 9/006: {projecting one or more stripes or patterns on the teeth}
- G06V 2201/03: Recognition of patterns in medical or anatomical images
- G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- 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

Described are methods that enable rapid automated object classification of measured three-dimensional object scenes. Each method can be performed during a three-dimensional measurement procedure while data are being acquired or after completion of the measurement procedure using the acquired data. In various embodiments, an object scene is illuminated with an optical beam and an image is acquired. In some embodiments, the object scene is illuminated with a structured light pattern and a sequence of images of the object scene illuminated by the pattern at different spatial phases is acquired. Coordinates are determined for points in the one or more images and a translucence value is determined for each of the points. An object class is determined for each point based on the translucence value for the point. Optionally, additional information, such as grayscale or color image data for each point, is used to supplement the object class determination.

## Claims

### Claim 1

A method of object classification for images of an intra-oral cavity, comprising:
illuminating at least a portion of an intra-oral cavity with an optical beam;
acquiring, at an imager having an array of photodetectors, an image of the illuminated portion of the intra-oral cavity;
determining, at a processor, coordinates for a plurality of points in the image;
determining, from the image, a background intensity value for each of the points;
determining, at the processor, a translucence value for each of the points based on the determined background intensity value for each of the points; and
determining, at the processor, an object class for each of the points based on the translucence value of the point, the object class selected from the group consisting of soft oral tissue, gingiva, teeth, posts, inserts, and cavity fillings.

### Claim 2 (depends on 1)

The method of claim 1 wherein determining the object class for each point comprises comparing the translucence value to at least one threshold value associated with an object class.

### Claim 3 (depends on 1)

The method of claim 1 further comprising determining, at the processor, an object color for each point and wherein determining the object class for each point is based on the translucence value and the object color.

### Claim 4 (depends on 1)

The method of claim 1 further comprising determining, at the processor, an object grayscale value for each point and wherein determining the object class for each point is based on the translucence value and the object grayscale value.

### Claim 5 (depends on 1)

The method of claim 1 wherein the coordinates are 3D coordinates for object surfaces in the intra-oral cavity.

### Claim 6 (depends on 1)

The method of claim 1 wherein the coordinates are 2D coordinates for the image of the intra-oral cavity.

### Claim 7 (depends on 1)

The method of claim 1 wherein determining the background intensity for each point comprises:
fitting an intensity function to a portion of the image including the point; and
determining a minimum value of the fitted intensity function.