Image distortion correction of a camera with a rolling shutter
Correcting image distortion during camera motion using a system including a processor and a camera having a rolling shutter. Multiple image frames are captured by the camera equipped with the rolling shutter. The captured image frames include a base image frame and a previous image frame. Multiple time stamps are recorded respectively for multiple corresponding image points in the previous and base image frames. For the corresponding image points, multiple ego-motions are computed responsive to the time stamps of the corresponding image points of the base image frame and the previous image frame to correct the image distortion caused by the rolling shutter.
1. A system for determining a distance to a point from a rolling shutter camera, the system comprising:
a processor configured to:
access a first image and a second image of an environment captured by the rolling shutter camera, the first and second images captured while the camera was moving, the first and second images each including a plurality of capture lines, the difference between capture time of respective capture lines of the first and second image being dT;
detect a point (x 1 , y 1 ) in a capture line of the first image at a time T 1 , which is the time when the capture line including y 1 was captured in the first image;
detect a corresponding point (x 2 , y 2 ) in a capture line of the second image at a time T 2 , which is the time when the capture line including y 2 was captured in the second image, wherein a difference between the time T 2 and the time T 1 is not equal to dT; and
determine the distance to the point at a time T 0 , which is different than the time T 1 or the time T 2 .
2. The system of claim 1 , wherein the processor is further configured to:
determine a distance to a second point from rolling shutter camera by:
detecting a point (x 3 , y 3 ) in a capture line of the first image at a time T 3 , which is the time when the capture line including y 3 was captured in the first image;
detecting a point (x 4 , y 4 ) in a capture line of the second image at a time T 4 , which is the time when the capture line including y 4 was captured in the second image, wherein the time T 3 is not equal to the time T 1 , and the time T 4 is not equal to the time T 2 ; and
determine the distance to the second point at the time T 0 , which is different from the time T 3 or the time T 4 .
3. The system of claim 1 , wherein the distance to the point from the rolling shutter is calculated by using camera motion detected between the time T 1 and the time T 2 , a line including point (x 1 , y 1 ) in a first coordinate frame of the rolling shutter camera at the time T 1 , and a line including the point (x 2 , y 2 ) in a second coordinate frame of the rolling shutter camera at the time T 2 , which are transformed to the first coordinate frame of the rolling shutter camera at the time T 1 using ego motion between the time T 1 and the time T 2 .
4. The system of claim 3 , wherein the processor is further configured to transform a distance to a third coordinate frame at the time T 0 using the camera motion detected between the time T 1 and the time T 0 .
5. The system of claim 3 , wherein the ego motion represents a translation and a rotation of the rolling shutter camera between the time T 1 and the time T 2 .
6. A method for determining a distance to a point from a rolling shutter camera, the method comprising:
receiving, from the rolling shutter camera, a first image and a second image of an environment of the rolling shutter camera, captured while the camera was moving, the first and second images each including a plurality of capture lines, the difference between capture time of respective capture lines of the first and second image being dT;
detecting a point (x 1 , y 1 ) in a capture line of the first image at a time T 1 , which is the time when the capture line including y 1 was captured in the first image;
detecting a corresponding point (x 2 , y 2 ) in a capture line of the second image at a time T 2 , which is the time when the capture line including y 2 was captured in the second image, wherein a difference between the time T 2 and the time T 1 is not equal to dT; and
determining the distance to the point at a time T 0 , which is different than the time T 1 or the time T 2 .
7. The method of claim 6 , further comprising:
determining a distance to a second point from the rolling shutter camera by:
detecting a point (x 3 , y 3 ) in a capture line of the first image at a time T 3 , which is the time when the capture line including y 3 was captured in the first image;
detecting a point (x 4 , y 4 ) in a capture line of the second image at a time T 4 , which is the time when the capture line including y 4 was captured in the second image, wherein the time T 3 is not equal to the time T 1 , and the time T 4 is not equal to the time T 2 ; and
determine the distance to the second point at the time T 0 , which is different from the time T 3 or the time T 4 .
8. The method of claim 6 , wherein determining the distance to the point from the rolling shutter comprises calculating by using camera motion detected between the time T 1 and the time T 2 , a line including point (x 1 , y 1 ) in a first coordinate frame of the rolling shutter camera at the time T 1 , and a line including the point (x 2 , y 2 ) in a second coordinate frame of the rolling shutter camera at the time T 2 , which are transformed to the first coordinate frame of the rolling shutter camera at the time T 1 using ego motion between the time T 1 and the time T 2 .
9. The method of claim 8 , further comprising transforming a distance to a third coordinate frame at the time T 0 using the camera motion detected between the time T 1 and the time T 0 .
10. The method of claim 8 , wherein the ego motion represents a translation and a rotation of the rolling shutter camera between the time T 1 and the time T 2 .