CAMERA CALIBRATION APPARATUS

• US 20110216194A1
• Filed: 01/24/2011
• Published: 09/08/2011
• Est. Priority Date: 03/02/2010
• Status: Active Grant

• Current Assignee: Alpine Electronics Incorporated (Alps Alpine Co., Ltd.), Toshiba Digital Solutions Corporation (Toshiba Corporation), Toshiba Electronic Devices & Storage Corporation (Toshiba Corporation)
• Original Assignee: Toshiba Corporation
• Inventors: KOSAKI, Masanori
• Granted Patent: US 8,842,181 B2
• Time in Patent Office: Days
• US Class Current: 348/148
• CPC Class Codes: B60R 1/00 Optical viewing arrangements; Real-time viewing arrangements for drivers or passengers using optical image capturing systems, e.g. cameras or video systems specially adapted for use in or on vehicles
• CPC Class Codes: B60R 1/27 providing all-round vision, e.g. using omnidirectional cameras
• CPC Class Codes: B60R 2300/402 Image calibration
• 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 7/18 Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast
• CPC Class Codes: H04N 7/181 for receiving images from a plurality of remote sources

Abstract

According to one embodiment, a camera calibration apparatus includes: a plurality of on-vehicle cameras; a feature point detection section that identifies an image of lines representing a parking frame from each of images by the plurality of cameras and detects two feature points; a viewpoint conversion section that generate an overhead view having a viewpoint from just above the vehicle based on the feature points and two directions crossing each other at each of the feature points; and an adjustment section that determines the boundary position between the vehicle and line image from the overhead view to determine the display frame of a vehicle image and changes the overhead view such that the size ratio and position of the display frame become previously specified values.

Claims

1. A camera calibration apparatus comprising:

an image photographing unit that has a plurality of cameras mounted on a vehicle to obtain camera images for the surrounding area of the vehicle;

a feature point detection unit that identifies an image of lines representing a parking frame from each of images obtained by the plurality of cameras and detects at least two feature points on the parking frame from each of the camera images;

a viewpoint conversion unit that synthesizes the camera images based on information including the feature points detected by the feature point detection unit and two directions crossing each other at each of the feature points to generate an overhead view having a viewpoint from just above the vehicle;

an adjustment unit that determines the boundary position between the vehicle and line image from the overhead view to determine the display frame of a vehicle image and changes the overhead view such that the size ratio and position of the display frame with respect to the overhead image become previously specified values; and

a camera data storage that stores camera parameters representing characteristics of each of the cameras which are calculated based on the changed overhead view.

2. The apparatus according to claim 1, wherein

the image photographing unit has four cameras for photographing the front surrounding area, back surrounding area, left surrounding area, and right surrounding area of the vehicle.

3. The apparatus according to claim 1, wherein

the image photographing unit photographs the parking frame being defined by white lines at a plurality of different positions by moving the vehicle, and

the feature point detection unit detects the feature points at the respective different positions.

4. The apparatus according to claim 1, wherein

the image photographing unit photographs the parking frame being defined by white lines, from at least one different position after moving the vehicle, and

the feature point detection unit detects the feature points at which the white lines cross each other and two directions of the white lines crossing each other at each of the feature points.

5. The apparatus according to claim 1, wherein

the adjustment unit sets the boundary lines based on the boundary position between each of the four sides of the vehicle and line image and determines a region defined by the minimum and maximum values of the coordinates of the intersections of the boundary lines as the display frame of the vehicle image.

6. The apparatus according to claim 5, wherein

the adjustment unit determines the position at which the line image disappears in the shade of the vehicle due to movement of the vehicle or position at which the line appears from the shade of the vehicle as the boundary position.

7. The apparatus according to claim 6, wherein

the adjustment unit determines the boundary position based on a change in the width of the line image when the vehicle passes over the line image.