Omni-directional camera with calibration and up look angle improvements

• US 20060023074A1
• Filed: 07/28/2004
• Published: 02/02/2006
• Est. Priority Date: 07/28/2004
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Cutler, Ross
• Granted Patent: US 7,495,694 B2
• Time in Patent Office: Days
• US Class Current: 348/218.100
• CPC Class Codes: G06T 7/80 Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
• CPC Class Codes: H04N 23/58 Means for changing the camera field of view without moving the camera body, e.g. nutating or panning of optics or image sensors
• CPC Class Codes: H04N 23/698 for achieving an enlarged field of view, e.g. panoramic image capture

Abstract

Improved camera calibration techniques, including an improved up look angle and an improved method for calibrating a virtual center of projection. By using a view camera technique for the up look angle, the image sensors can be mounted flat to a Printed Circuit Board (PCB). By using a sub-region of the image sensor for the active area of the camera it is possible to calibrate the virtual center of projection (C′).

Claims

1. A camera system comprising:

N cameras of a camera array, wherein each camera comprises a lens and associated sensor, and wherein the lens of each camera is offset with respect to its associated sensor so that the optical axis of the camera is shifted to achieve a desired virtual center of projection; and

an N-sided mirror is located above the N cameras, each camera capturing an image reflected in a different side of said N-sided mirror.

2. The camera system of claim 1 wherein by adjusting the x and y offset of the lens relative to the sensor, the virtual center of projection C′

is shifted to a desired position.

3. The camera system of claim 1 wherein for a camera with an optical axis angle with the vertical of χ

and with focal length f, the shift of the sensor relative to the lens is defined by f*tan(χ

).

4. The camera system of claim 2 wherein the desired position of the virtual center of projection is electronically achieved using sensor sub-images.

5. The camera system of claim 2 wherein the focus of the camera is adjusted.

6. A camera system comprising:

an N-sided mirror located said above N cameras arranged to be equally spaced around at least a portion of a circle each capturing an image reflected in a different side of said N-sided mirror, wherein each camera has an up look angle from the horizontal plane achieved by horizontally mounting the camera sensor and offsetting the sensor center from the optical axis so that the image is completely captured by the sensor.

7. The camera system of claim 6 wherein said N cameras in total cover 360 degrees in the horizontal plane.

8. The camera system of claim 6 wherein the up look angle is achieved by offsetting the optical axis by the camera'"'"'s focal length f multiplied by the tangent of the angle χ

of the optical axis with respect to the vertical.

9. A camera system comprising:

N cameras of a camera array, wherein each camera comprises a lens and associated sensor, and wherein the lens of each camera is offset with respect to the center of its associated sensor so that the optical axis of the camera is shifted to achieve a desired up look angle; and

an N-sided mirror is located above the N cameras, each camera capturing an image reflected in a different side of said N-sided mirror.