Measuring camera to body alignment for an imager mounted within a structural body

• US 10,458,793 B2
• Filed: 01/17/2018
• Issued: 10/29/2019
• Est. Priority Date: 01/17/2018
• Status: Active Grant

• Current Assignee: The United States Of America As Represented By The Secretary Of The Army
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Everson, Daniel P., Maley, James M.
• Primary Examiner(s): Atala, Jamie J
• Assistant Examiner(s): Cammarata, Michael Robert
• Application Number:
  US15/873,036
• Publication Number:
  US 20190219392A1
• Time in Patent Office: 650 Days
• CPC Class Codes: G01B 11/27 for testing the alignment of axes means for centering or aligning a light guide within a ferrule G02B6/3834
• CPC Class Codes: G01B 5/0025 Measuring of vehicle parts G01B5/003 takes precedence
• CPC Class Codes: G01C 1/00 Measuring angles
• CPC Class Codes: G01C 11/02 Picture taking arrangements specially adapted for photogrammetry or photographic surveying, e.g. controlling overlapping of pictures
• CPC Class Codes: G01C 11/06 by comparison of two or more pictures of the same area
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G02B 27/62 Optical apparatus specially adapted for adjusting optical elements during the assembly of optical systems
• CPC Class Codes: G02B 7/003 Alignment of optical elements G02B7/001, G02B7/002 take precedence; for mirrors G02B7/1822
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 7/80 Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
• CPC Class Codes: G06T 7/85 Stereo camera calibration
• CPC Class Codes: H04N 13/246 Calibration of cameras
• CPC Class Codes: H04N 17/002 for television cameras

Abstract

A technique is provided to measure an alignment of an imaging device of a guided projectile containing an imager and a world coordinate frame, and includes producing a pure rolling motion of a body of the projectile, capturing a series of images of an imaging device calibration target over a range of body roll angles of the rolling body, measuring the roll angles of the rolling body with respect to a world coordinate frame as defined by the imaging device calibration target, simultaneously estimating alignment angles of the imaging device and misalignment angles associated with an orientation of the body, and estimating a rotational transform between an imaging device coordinate frame and a body coordinate frame based on the estimated alignment angles and misalignment angles.

Claims

1. A method for measuring an alignment of an imaging device, the method comprising:

producing a pure rolling motion of a body;

capturing a series of images of an imaging device calibration target over a range of body roll angles of the rolling body;

measuring the roll angles of the rolling body with respect to a world coordinate frame as defined by the imaging device calibration target;

simultaneously estimating alignment angles of the imaging device and misalignment angles associated with an orientation of the body; and

estimating a rotational transform between an imaging device coordinate frame and a body coordinate frame based on the estimated alignment angles and misalignment angles

wherein the producing of the pure rolling motion of the body occurs by a pair of support mechanisms that mechanically constrain the body to produce the pure rolling motion

wherein the support mechanisms comprise v-block mechanisms.

2. The method of claim 1, wherein the body comprises a guided projectile.

3. A system for measuring an alignment of an imager, the system comprising:

a pair of support mechanisms to produce a pure rolling motion of a body;

an imager rigidly affixed to the body to capture a series of images of an imager calibration target over a range of body roll angles of the rolling body;

a sensor to measure the roll angles of the rolling body with respect to a world coordinate frame as defined by the imager calibration target; and

a processor to;

simultaneously estimate alignment angles of the imager and misalignment angles associated with an orientation of the body; and

estimate a rotational transform between an imager coordinate frame and a body coordinate frame based on the estimated alignment angles and misalignment angles, wherein the alignment angles comprise three rotation angles representing a transform between the body coordinate frame and the imager coordinate frame, and wherein the misalignment angles comprise two rotation angles representing a transform between a roll axis of the body and the world coordinate frame,

wherein the body comprises a guided projectile containing the imager.