Error corrected optical navigation system
View Patent ↗An optical navigation system. The optical navigation system includes an image sensor capable of optical coupling to a surface of an object, a data storage device, and a navigation circuit. The data storage device is capable of storing successive images captured by the image sensor. The navigation circuit includes a first digital circuit capable of determining an optical displacement estimate for a relative displacement between the image sensor and the object obtained by comparing the images, a second digital circuit capable of determining a mechanical displacement estimate for the relative displacement obtained from consideration of a mechanical characteristic associated with the optical navigation system, and a third digital circuit capable of determining an adjusted displacement estimate obtained from the optical displacement estimate and the mechanical displacement estimate.
1. An optical navigation system, comprising:
an image sensor capable of optical coupling to a surface of an object, wherein the image sensor is capable of capturing successive images of areas of the surface;
a data storage device, wherein the data storage device is capable of storing successive images captured by the image sensor; and
a navigation circuit, wherein the navigation circuit comprises a first digital circuit capable of determining an optical displacement estimate for a relative displacement between the image sensor and the object obtained by a comparison of the images, wherein the navigation circuit further comprises a second digital circuit capable of determining a mechanical displacement estimate for the relative displacement obtained from consideration of a mechanical characteristic associated with the optical navigation system, and wherein the navigation circuit comprises a third digital circuit capable of determining an adjusted displacement estimate obtained from the optical displacement estimate and the mechanical displacement estimate.
2. The optical navigation system as recited in claim 1 , wherein the first digital circuit comprises:
a fourth digital circuit capable of performing multiple shifts in one of the images;
a fifth digital circuit capable of performing a comparison between one of the other images and the shifted multiple images; and
a sixth digital circuit capable of obtaining the optical displacement estimate from the comparisons of the fifth digital circuit.
3. The optical navigation system as recited in claim 2 , wherein the comparisons of the fifth digital circuit are cross-correlations.
4. The optical navigation system as recited in claim 2 , wherein the first digital circuit further comprises:
a seventh digital circuit capable of specifying which images to use for comparison by the fifth digital circuit to determine the optical displacement estimate.
5. The optical navigation system as recited in claim 1 , wherein the mechanical characteristic is an acceleration profile.
6. The optical navigation system as recited in claim 5 , wherein at least part of the acceleration profile is determined from theoretical considerations.
7. The optical navigation system as recited in claim 5 , wherein at least part of the acceleration profile is empirically determined.
8. The optical navigation system as recited in claim 1 , wherein the mechanical characteristic is an acceleration profile for the optical navigation system.
9. The optical navigation system as recited in claim 1 , wherein the mechanical characteristic is an acceleration profile for the optical navigation system and at least one other device attached to the optical navigation system.
10. The optical navigation system as recited in claim 9 , wherein the at least one other device is a print head.
11. The optical navigation system as recited in claim 1 ,
wherein if the difference between the optical displacement estimate and the mechanical displacement estimate is outside a preselected error range, the third digital circuit reports the value of the optical displacement estimate adjusted in relation to the mechanical displacement estimate as the adjusted displacement estimate;
otherwise, the third digital circuit reports the value of the optical displacement estimate as the adjusted displacement estimate.
12. The optical navigation system as recited in claim 1 ,
wherein if the difference between the optical displacement estimate and the mechanical displacement estimate is outside a preselected error range, the third digital circuit reports the value of the optical displacement estimate adjusted to the mechanical displacement estimate, wherein the mechanical displacement estimate is less than or equal to a specified maximum value;
otherwise, the third digital circuit reports the value of the optical displacement estimate as the adjusted displacement estimate.
13. The optical navigation system as recited in claim 1 , wherein the optical navigation system is attached to a printer.
14. A method for error correcting an optical navigation system, comprising:
optically coupling an image sensor to a surface of an object;
capturing successive images with the image sensor of areas of the surface;
storing the successive images;
determining an optical displacement estimate for a relative displacement between the image sensor and the object by a comparison of the images;
determining a mechanical displacement estimate for the relative displacement by consideration of a mechanical characteristic associated with the optical navigation system; and
determining an adjusted displacement estimate from the optical displacement estimate and the mechanical displacement estimate.
15. The method as recited in claim 14 , wherein the step determining the optical displacement estimate for a relative displacement between the image sensor and the object comprises:
performing multiple shifts in one of the images;
performing a comparison between one of the other images and the shifted multiple images; and
obtaining the optical displacement estimate from the results of the step performing a comparison between one of the other images and the shifted multiple images.
16. The method as recited in claim 14 , wherein the mechanical characteristic is an acceleration profile.
17. The method as recited in claim 14 , wherein the step determining an adjusted displacement estimate comprises:
if the difference between the optical displacement estimate and the mechanical displacement estimate is outside a preselected error range, reporting the value of the optical displacement estimate adjusted in relation to the mechanical displacement estimate as the adjusted displacement estimate;
otherwise, reporting the value of the optical displacement estimate as the adjusted displacement estimate.
18. The method as recited in claim 14 , wherein if the mechanical displacement estimate indicates zero motion between successive images, the step determining an adjusted displacement estimate comprises:
averaging the optical displacement estimates to obtain the adjusted displacement estimate.
19. The method as recited in claim 14 , the steps further comprising:
adjusting the threshold for re-referencing based upon the direction of motion and the mechanical characteristics in that direction.
20. The method as recited in claim 14 , the steps further comprising:
adjusting the rate of image capture based on the mechanical characteristics and velocity of the optical navigation system.