Vehicle wheel alignment methods and systems

1. A wheel alignment system comprising:

a pair of first and second passive heads, each for mounting in association with one wheel of a first pair of wheels disposed on first and second sides, respectively, of a vehicle that is to be measured by operation of the wheel alignment system;

a side-to-side reference system comprising a pair of reference pods mounted to a stationary reference, the pair of reference pods including a first reference pod disposed on one of the first and second sides of the vehicle, and a second reference pod disposed on the other of the first and second sides of the vehicle, wherein one of the first and second reference pods has a reference image sensor oriented to view the other of the first and second reference pods, and to produce image data of the other of the first and second reference pods;

a pair of first and second active heads, each comprising an image sensor, for mounting in association with the first and second sides of the vehicle, respectively, the image sensor of the first active head producing image data of the first passive head and of the first reference pod, and the image sensor of the second active head producing image data of the second passive head and of the second reference pod; and

a computer for processing image data from the reference image sensor to determine a spatial relationship between the first and second reference pods, and for processing image data from the image sensors of the active heads to compute at least one alignment measurement of the vehicle based on the determined spatial relationship between the first and second reference pods.

2. The wheel alignment system of claim 1 , wherein the first reference pod comprises the reference image sensor and a reference target fixedly attached to the reference image sensor; and

wherein the computer computes the spatial relationship between the first and second reference pods based on image data of the second reference pod produced by the reference image sensor, and based on a known spatial relationship between the reference image sensor and the reference target of the first reference pod.

3. The wheel alignment system of claim 1 , wherein the first reference pod comprises the reference image sensor and the second reference pod comprises first and second targets, the reference image sensor produces image data including a perspective representation of the first target of the second reference pod, and the image sensor of the second active head produces image data including a perspective representation of the second target of the second reference pod.

4. The wheel alignment system of claim 3 , wherein the first and second targets of the second reference pod have a known spatial relationship to each other, and the computer computes the spatial relationship between the first and second reference pods according to the image data produced by the image sensors and the known spatial relationship between the first and second targets of the second reference pod.

5. The wheel alignment system of claim 1 , wherein the stationary reference having the first and second reference pods mounted thereon is a ground, a rack, or a lift.

6. The wheel alignment system of claim 1 , wherein the first and second active heads are for mounting to a stationary reference.

7. The wheel alignment system of claim 1 , wherein the first and second active heads are for mounting to the vehicle that is to be measured by operation of the wheel alignment system.

8. The wheel alignment system of claim 7 , wherein the first and second active heads are for mounting in association with a second pair of wheels disposed on the first and second sides of the vehicle.

9. A method for measuring an alignment of a vehicle comprising:

attaching a pair of first and second passive heads in association with a first pair of wheels disposed on first and second sides, respectively, of the vehicle to be measured;

providing a side-to-side reference system comprising a pair of reference pods mounted to a stationary reference, the pair of reference pods including a first reference pod disposed on one of the first and second sides of the vehicle, and a second reference pod disposed on the other of the first and second sides of the vehicle, one of the first and second reference pods comprising a reference image sensor oriented to view the other of the first and second reference pods;

capturing, using the reference image sensor of the one of the first and second reference pods, image data of the other one of the first and second reference pods;

capturing, using an image sensor of a first active head mounted in association with the first side of the vehicle, image data of the first passive head and of the first reference pod;

capturing, using an image sensor of a second active head mounted in association with the second side of the vehicle, image data of the second passive head and of the second reference pod;

processing the image data from the reference image sensor to determine a spatial relationship between the first and second reference pods; and

processing the image data from the image sensors of the active heads to compute at least one alignment measurement of the vehicle based on the determined spatial relationship between the first and second reference pods.

10. The method of claim 9 , comprising providing the first reference pod with the reference image sensor and with a reference target fixedly attached to the reference image sensor;

wherein the processing comprises computing the spatial relationship between the first and second reference pods based on the image data produced by the reference image sensor, and based on a known spatial relationship between the reference image sensor and the reference target of the first reference pod.

11. The method of claim 9 , wherein the first reference pod comprises the reference image sensor, and the second reference pod comprises first and second targets;

wherein the step of capturing image data using the reference image sensor comprises capturing image data including a perspective representation of the first target of the second reference pod, and

wherein the step of capturing image data using the image sensor of the second active head comprises capturing image data including a perspective representation of the second target of the second reference pod.

12. The method of claim 11 , wherein the first and second targets of the second reference pod have a known spatial relationship to each other, and the step of processing the image data from the reference image sensor includes determining the spatial relationship between the first and second reference pods according to the image data produced by the image sensors and the known spatial relationship between the first and second targets of the second reference pod.

13. The method of claim 9 , further comprising mounting the first and second reference pods to the stationary reference prior to capturing image data using the reference image sensor and the image sensors of the first and second active heads, wherein the stationary reference is a ground, a rack, or a lift.

14. The method of claim 9 , further comprising mounting the first and second active heads to a stationary reference prior to capturing image data using the image sensors of the first and second active heads.

15. The method of claim 9 , further comprising mounting the first and second active heads in association with the vehicle that is to be measured by operation of the wheel alignment system prior to capturing image data using the images sensors of the first and second active heads.

16. The method of claim 15 , wherein the mounting comprises mounting the first and second active heads in association with a second pair of wheels disposed on the first and second sides of the vehicle.