Image sensing wheel alignment system

• US 20040246470A1
• Filed: 05/28/2004
• Published: 12/09/2004
• Est. Priority Date: 05/05/2000
• Status: Active Grant

• Current Assignee: Hunter Engineering Company
• Original Assignee: Hunter Engineering Company
• Inventors: Shylanski, Mark S., Golab, Thomas J., Voeller, David A., Dorrance, Daniel R., Burns, Leigh R.
• Granted Patent: US 7,295,297 B2
• Time in Patent Office: Days
• US Class Current: 356/139.09
• CPC Class Codes: G01B 11/2755 using photoelectric detection means

Abstract

An improved image sensing wheel alignment system for calculating vehicle wheel alignments having a detector array for receiving an input image containing vehicle wheel alignment information. An image sensor controller controls the detector array to receive the input image during an acquisition period, the image sensor controller examining signals from the image detecting elements individually at a plurality of times during the acquisition period to determine exposure levels for image detecting elements. An output image from the image detecting elements at the end of the acquisition period contains wheel alignment information for use in calculating vehicle wheel alignments.

Claims

1. An improved image sensing wheel alignment system for calculating vehicle wheel alignments comprising:

a detector array for receiving an input image containing vehicle wheel alignment information, said detector array having image detecting elements;

an image sensor controller for controlling the detector array to receive the input image during an acquisition period, said image sensor controller examining signals from the image detecting elements individually during the acquisition period, and further including circuitry for reading out an output image from the image detecting elements, said output image containing wheel alignment information for use in calculating vehicle wheel alignments, said output image including outputs from image detecting elements obtained at two different exposure levels.

2. The image sensing wheel alignment system as set forth in claim 1 wherein the input image contains a plurality of points of interest, said output image having different exposure levels for at least some of the points of interest.

3. The image sensing wheel alignment system as set forth in claim 1 wherein the input image includes at least one bright lighted portion, the output image having a lower exposure level for said bright ambient lighted portion.

4. The image sensing wheel alignment system as set forth in claim 1 wherein the image sensor controller is responsive to brightness gradients over the input image to control the exposure level of the image detecting elements.

5. The image sensing wheel alignment system as set forth in claim 4 wherein the brightness gradient is due to illumination.

6. The image sensing wheel alignment system as set forth in claim 4 wherein the brightness gradient is due to reflection.

7. The image sensing wheel alignment system as set forth in claim 4 wherein the brightness gradient is due to image detecting element response.

8. The image sensing wheel alignment system as set forth in claim 4 wherein the brightness gradient is due to lens effects.

9. The image sensing wheel alignment system as set forth in claim 1 further including a first illumination source for illuminating a scene containing wheel alignment information from a first angle during a first interval, and a second illumination source for illuminating said scene from a second angle during a second interval, said image sensor controller controlling the image detecting elements to prevent saturation during each of said intervals, exposure of said scene during the first interval resulting in a first output image, and exposure of said scene during the second interval resulting in a second output image, the system including logic for analyzing differences between the first and second output images to identify specularities in the image.

10. The image sensing wheel alignment system as set forth in claim 9 wherein the logic uses subpixel techniques for analyzing said differences.

11. The image sensing wheel alignment system as set forth in claim 9 wherein the image detecting elements constitute a first image array associated with the first illumination source, further including a second image array associated with the second illumination source, the input images of the scene resulting from use of the first illumination source being received by the second image array, and the input images of the scene resulting from use of the second illumination source being received by the first image array, the exposure levels of both image arrays being controlled during the corresponding intervals, further including logic for comparing output images from the first and second arrays to determine positions of specularities in the output images.

12. The image sensing wheel alignment system as set forth in claim 11 wherein the first interval and the second interval are concurrent, the first image array being sensitive to light of a first color, and the second image array being sensitive to light of a second color.

13. The image sensing wheel alignment system as set forth in claim 1 wherein the input image includes at least one under exposed portion, said controller being responsive to under exposure to increase the total acquisition time.

14. The image sensing wheel alignment system as set forth in claim 1 wherein the image sensor controller is responsive to banding over the input image to control exposure level of the image detecting elements.

15. The image sensing wheel alignment system as set forth in claim 14 wherein the input image includes a target that contains no retroreflective material.

16. The image sensing wheel alignment system as set forth in claim 14 wherein a tire assembly is imaged.

17. The image sensing wheel alignment system as set forth in claim 14 wherein the banding is due to cycling of illumination sources at a higher rate than image acquisition cycles.

18. The image sensing wheel alignment system as set forth in claim 1 wherein the image sensor controller is responsive to brightness variations due to fluctuation in the brightness of artificial lighting during exposure times to control exposure levels of the image detecting elements.

19. The image sensing wheel alignment system as set forth in claim 1 further including a memory for saving signal values of each image detecting element, said signal values being capable of indicating over-exposure of image detecting elements, and logic for analyzing said saved values to reduce over-exposure.

20. The image sensing wheel alignment system as set forth in claim 19 wherein the saved signal values are averaged.

21. The image sensing wheel alignment system as set forth in claim 1 wherein the input image includes a vehicle tire assembly.

22. The image sensing wheel alignment system as set forth in claim 1 wherein the input image includes a target associated with a vehicle wheel to be aligned.

23. The image sensing wheel alignment system as set forth in claim 22 wherein the target is constructed without retroreflective material.

24. The image sensing wheel alignment system as set forth in claim 1 wherein the image sensor controller is responsive to a signal indicating probable over-exposure of a particular image detecting element by the end of the acquisition period to reset said particular image detecting element.

25. An image sensing wheel alignment system comprising:

an imager having a sensitivity that extends from below 10 Lux to at least 10,000 Lux;

an ambient light source for illuminating a scene containing wheel alignment information;

said imager receiving information from said scene as illuminated by the ambient light source;

logic for analyzing the output of the imager to extract wheel alignment information.

26. An image sensing wheel alignment system comprising:

an image detector for sensing an input image of a scene containing vehicle wheel alignment information, said image detector having a plurality of pixels disposed in an array, each pixel having at least first and second photo detectors, the first photo detector for at least some of the pixels having a first sensitivity to light and the second photo detector for at least some of the pixels having a second sensitivity to light;

logic responsive to the output levels of said photo detectors to select, for each pixel, an optimal photo detector output and to extract vehicle wheel alignment information from measured values of the selected outputs.

27. The image sensing wheel alignment system as set forth in claim 26 wherein when said output exceeds a predetermined level indicative of saturation the logic selects the output of the lower sensitivity photo detector for each pixel where said output exceeds said predetermined level.

28. The image sensing wheel alignment system as set forth in claim 26 wherein the first and second photo detectors are disposed horizontally with respect to the array.

29. The image sensing wheel alignment system as set forth in claim 26 wherein the first and second photo detectors are disposed vertically with respect to the array.

30. A method of operating an image sensing wheel alignment system comprising:

obtaining multiple input images of a scene containing wheel alignment information taken at different exposure levels and using different angles of illumination, at least some of the input images being taken at the same exposure levels but different angles of illumination;

said input images falling on a detector array so as to create corresponding output images for each input image;

comparing at least some of the output images to identify specularities in the scene.

31. The method as set forth in claim 30 further including classifying scene elements as to smoothness.

32. The method as set forth in claim 30 further including determining positions of specularities in the scene.

33. A method of operating an image sensing wheel alignment system comprising:

sensing an input image of a scene containing vehicle wheel alignment information with an image detector having a plurality of pixels disposed in an array, each pixel having at least first and second photo detectors, the first photo detector for at least some of the pixels having a first sensitivity to light and the second photo detector for at least some of the pixels having a second sensitivity to light;

selecting, for at least one pixel, an optimal photo detector output; and

extracting vehicle wheel alignment information from measured values of the selected outputs.

34. A method of operating an image sensing wheel alignment system comprising:

receiving an image of a scene containing wheel alignment information;

identifying a region of interest in said image;

processing the region of interest in the image without further processing of the remainder of the image; and

determining wheel alignment angles from the processed image of the region of interest.

35. A method of operating an image sensing wheel alignment system comprising:

receiving an output image of a scene containing wheel alignment information from an imager;

identifying a region of interest in said image;

controlling subsequent output images to reduce extraneous information, said extraneous information not including said wheel alignment information; and

determining wheel alignment angles from the processed image of the region of interest.