Device and method for calibrating an imaging device for generating three dimensional surface models of moving objects

• US 20070104361A1
• Filed: 11/10/2006
• Published: 05/10/2007
• Est. Priority Date: 11/10/2005
• Status: Active Grant

• Current Assignee: Motion Analysis Corp.
• Original Assignee: Motion Analysis Corp.
• Inventors: Alexander, Eugene
• Granted Patent: US 8,223,208 B2
• Time in Patent Office: Days
• US Class Current: 382/154
• CPC Class Codes: G06V 10/147 Details of sensors, e.g. sensor lenses fingerprint or palmprint sensors G06V40/13; vascular sensors G06V40/145; eye sensors G06V40/19
• CPC Class Codes: G06V 2201/12 Acquisition of 3D measurements of objects
• CPC Class Codes: H04N 13/261 with monoscopic-to-stereoscopic image conversion

Abstract

A device and technique are presented to calibrate an imaging device for generating three-dimensional surface models of moving objects and calculating three-dimensional coordinates of detected features relative to a coordinate system embedded in the device. The internal projector and camera parameters, i.e., zoom, focus, aperture, optical center, logical pixel size, aspect ratio, are determined for all projectors and cameras and all possible focal planes of the device in operation.

Claims

1. A device for determining a parameterization of the optical characteristics of an imaging device, comprising:

a directional mount;

a linear tracked device;

a step motor;

a mounting jig; and

a calibration object.

2. The device of claim 1, wherein the directional mount positions the imaging device and the mounting jig positions the calibration object.

3. A method for calibrating an imaging device, comprising:

aligning a calibration object with the imaging device;

projecting a pattern on the calibration object;

detecting features of the pattern;

using locations of the features to calibrate camera elements of the imaging device; and

repeating the procedure.

4. The method of claim 3, wherein the distance between the calibration object and the optical axis of the imaging device projects a known distance.

5. The method of claim 3, wherein the distance perpendicular to the optical axis defines a focal plane.

6. The method of claim 5, wherein the procedure is repeated at all focal planes where the device will be operated.

7. A method for validating the calculation of three dimensional coordinates produced by a three dimensional imaging device, comprising:

aligning a calibration object with the imaging device;

projecting a pattern on the calibration object at a known out of focus distance;

detecting features of the pattern;

determining the variation of the features from those features at the in focus distance; and

calculating a mapping of the degree of de-focus of any set of feature points.

8. The method of claim 7, wherein the feature is a line, and the variation between the in focus value of the line thickness is mapped to the out of focus value of the line thickness.

9. The method of claim 7, wherein the feature is a box, and the variation between the in focus value of the box size is mapped to the out of focus value of the box size.

10. The method of claim 7, wherein the feature is a box, and the variation between the in focus value of the ratio of white pixels to black pixels is mapped to the out of focus value of the ratio of white pixels to black pixels.