Method for evaluating component calibration in machine vision vehicle wheel alignment system

Patent metadata

Field	Value
Publication number	US-9644952-B2
Application number	US-201313830867-A
Country	US
Kind code	B2
Filing date	Mar 14, 2013
Priority date	Oct 18, 2012
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

A process for calibrating and evaluating a machine-vision vehicle wheel alignment system having front and rear imaging components associated with each of the left and right sides of a vehicle support structure. Each pair of imaging components defines a front and rear field of view, with a common overlapping region associated with each respective side of the vehicle support structure. Optical targets disposed within each of the overlapping field of view regions are observed by the imaging components to establish performance ratings for the system as a whole, for groups of components within the system, and for individual components within the system.

First claim

The invention claimed is:

1. A method for evaluating a machine vision vehicle wheel alignment measurement system having a plurality of camera components, each of said camera components having a stationary field of view for observing at least one optical target, comprising:
disposing a set of optical targets within overlapping regions of the stationary fields of view for said plurality of camera components such that at least one optical target within said set of optical targets is observable by at least two camera components within said plurality of camera components;
observing said set of optical targets with said plurality of camera components to acquire a set of images representative of said observed optical targets, said set of images including, for each observed optical target, at least two images acquired from separate camera components within said plurality of camera components;
processing said set of images to identity, for each of said observing camera components, data representative of at least one feature associated with said observed optical targets;
comparing said identified data from each of said observing camera components to establish at least one representation of performance for at least a single component of the machine vision vehicle wheel alignment measurement system; and
wherein said single component may be an established calibration transform, a camera component, an optical target, a calibration fixture, or a vehicle support surface.

2. The method of claim 1 wherein said representation of performance is an identification of at least one defective component associated with the machine vision vehicle wheel alignment measurement system; and
wherein said defective component may be an established calibration transform, a camera component, an optical target, a calibration fixture, or a vehicle support structure.

3. The method of claim 1 wherein said representation of performance is an indication of a change in a configuration associated with at least one camera component of the machine vision vehicle wheel alignment measurement system having occurred after a calibration procedure; and
wherein said change in configuration is a change in a mounting position of said at least one camera component relative to another camera component, or a change in a configuration of one or more optical elements within said at least one camera component.

4. A method for evaluating a machine vision vehicle wheel alignment measurement system having at least four cameras including, for the left and right sides of a vehicle positioned on a vehicle support surface, a front camera with an associated field of view disposed to view a front wheel of the vehicle, and a rear camera with an associated field of view disposed to view a rear wheel of the vehicle, said rear camera associated field of view and said front camera associated field of view intersecting to define an overlapping region, comprising:
providing a fixture having identifiable features;
acquiring from said cameras disposed in a selected spatial configuration, a set of images of said identifiable features of said fixture disposed on said vehicle support surface at a plurality of positions within said fields of view, at least one of said plurality of positions disposed within said overlapping regions for said fields of view of said front and rear cameras on each side of the vehicle;
processing said set of acquired images to calibrate said plurality of cameras and said vehicle support surface associated with said machine vision wheel alignment measurement system;
repeating said step of acquiring to acquire from at least one of said cameras disposed in said selected spatial configuration, a second set of images while said fixture is disposed on said vehicle support surface at a position which is within the overlapping region of the fields of view associated with said front and rear cameras on each side of the vehicle support surface; and
processing said second set of acquired images to establish a performance metric for said calibrated machine vision wheel alignment measurement system.

5. The method of claim 4 wherein said second set of images includes images acquired from each of said cameras, and wherein said performance metric is established for said machine vision vehicle wheel alignment measurement system as a whole.

6. The method of claim 4 wherein said performance metric is established for at least one of said cameras.

7. The method of claim 4 wherein said performance metric identifies one of a change in a relative position of one of said cameras relative to another of said cameras, a change associated with a component within at least one of said cameras subsequent to said calibration, or a change associated with at least one of said identifiable features of said calibration fixture.

8. A method for evaluating a machine vision vehicle service system having a plurality of camera components disposed to view each side of a vehicle support surface, comprising:
observing a set of optical targets mounted to a fixture with said plurality of camera components to acquire a set of images representative of said observed optical targets, while said fixture is disposed on said vehicle support surface at a position which is within a region of overlapping fields of view associated with said plurality of camera components;
processing said set of images to identity at least one of a defective camera component, a defective optical target and a defect associated with said fixture.

9. A method for establishing coordinate transforms between cameras in a machine vision vehicle wheel alignment measurement system, comprising:
acquiring, from a first camera in a first position and orientation, at least two images of a portion of a fixture positioned in at least two different locations within the field of view of the first camera, at least one of said images acquired with said fixture positioned on a surface within a region of overlapping fields of view of said first camera and a second camera;
acquiring, from said second camera in a second position and orientation, at least two images of said portion of said fixture positioned in at least two different locations within the field of view of the second camera, at least one of said images acquired with said portion of said fixture positioned on said surface within said region of overlapping fields of view of said first camera and said second camera;
processing said set of acquired images from each of said cameras to establish a coordinate transform between reference frames of the first camera in said first position and orientation and said second camera in said second position and orientation;
wherein said first camera is a front camera having a field of view disposed to view a front wheel of a vehicle disposed on said surface;
wherein said second camera is a rear camera having a field of view disposed to view a rear wheel of said vehicle on said same side as said front wheel; and
wherein said front and rear cameras are secured in a fixed relationship laterally offset from, and longitudinally in front of, said surface.

10. The method of claim 9 wherein said portion of said fixture includes an optical target.

11. The method of claim 9 further including the steps of:
acquiring, from a third camera in a third position and orientation, at least two images of a second portion of said fixture positioned on said surface within a field of view of the third camera, at least one of said images acquired with said second portion of said fixture positioned on said surface within a region of overlapping fields of view of said third camera and a fourth camera;
acquiring, from said fourth camera in a fourth position

Assignees

• Hunter Eng Co

Inventors

• Shylanski Mark S
• Dorrance Daniel R
• Bernard Bruce E
• Golab Thomas J
• Stieff Michael T
• Mcclenahan James W
• Silver J Kaleb
• Strege Timothy A
• Colarelli Iii Nicholas J

Classifications

• G01B2210/12

  Method or fixture for calibrating the wheel aligner · CPC title

• G01B11/275

  for testing wheel alignment · CPC title

• G06T7/0024

  Physics · mapped topic

• G06T7/0042

  Physics · mapped topic

• G06T7/002

  Physics · mapped topic