Calibration apparatus and calibration method

Patent metadata

Field	Value
Publication number	US-10032274-B2
Application number	US-201514671682-A
Country	US
Kind code	B2
Filing date	Mar 27, 2015
Priority date	Apr 2, 2014
Publication date	Jul 24, 2018
Grant date	Jul 24, 2018

Abstract

There is provided a calibration apparatus for calculating a camera installation parameter with respect to a flat surface without preparing two sets of parallel lines on the flat surface, with respect to which the camera installation parameter is to be obtained. An acquirer acquires a photographed image of two linearly-extending lines substantially perpendicular to a flat surface. An extractor extracts the two linearly-extending lines from the acquired image through image processing. A calculator calculates a vanishing point from the extracted two linearly-extending lines and calculates a camera installation parameter with respect to the flat surface on the basis of coordinates of the vanishing point and given coordinates different from the coordinates of the vanishing point.

First claim

What is claimed is:

1. A calibration apparatus comprising:
an acquirer which acquires an image including two real linear line segments based on two different objects, respectively, photographed at an identical time, from a camera installed on a movable body, the two real linear line segments being substantially perpendicular to a movement flat surface on which the movable body moves;
an extractor which extracts the two real linear line segments from the image acquired by the acquirer;
a calculator which calculates a first vanishing point from two extended lines of the two real linear line segments that are extracted by the extractor and sets any point other than the first vanishing point as a second vanishing point, and calculates a vanishing line which passes through the first and second vanishing points, and calculates a camera installation parameter with respect to the movement flat surface, on a basis of coordinates of the first and second vanishing points and the vanishing line; and
a transmitter which transmits the camera installation parameter;
wherein the camera measures the distance from the movable body to an object using the camera installation parameter.

2. The calibration apparatus according to claim 1 , further comprising the camera which acquires the image.

3. A calibration method comprising:
acquiring an image including two real linear line segments based on two different objects, respectively, photographed at an identical time, from a camera installed on a movable body, the two real linear line segments being substantially perpendicular to a movement flat surface on which the movable body moves;
extracting the two real linear line segments from the acquired image through image processing;
calculating a first vanishing point from two extended lines of the extracted two real linear line segments and setting any point other than the first vanishing point as a second vanishing point, and calculating a vanishing line which passes through the first and second vanishing points, and calculating an installation parameter for the camera with respect to the movement flat surface, on a basis of coordinates of the first and second vanishing points; and
transmitting the installation parameter;
wherein the camera measures the distance from the movable body to an object using the camera installation parameter.

4. A calibration apparatus comprising:
an acquirer which acquires a first image and a second image from a camera installed on the movable body, the first image being photographed at a first time and including a first real linear line segment substantially perpendicular to a movement flat surface on which a movable body moves, and the second image being photographed at a second time after movement of a movable body after the first time and including a second real linear line segment substantially perpendicular to the movement flat surface, the second real linear line segment being based on a photographed object identical to that of the first real linear line segment;
an extractor which extracts the first real linear line segment from the first image and the second real linear line segment from the second image through image processing; and
a calculator which calculates a first vanishing point from a first extended line of the first real linear line segment extracted from the first image by the extractor and a second extended line of the second real linear line segment extracted from the second image by the extractor and sets any point other than the first vanishing point as a second vanishing point, and calculates a vanishing line which passes through the first and second vanishing points, and calculates an installation parameter for the camera with respect to the movement flat surface, on a basis of coordinates of the first and second vanishing points and the vanishing line; and
a transmitter which transmits the installation parameter;
wherein the camera measures the distance from the movable body to an object using the camera installation parameter.

5. The calibration apparatus according to claim 4 , further comprising the camera which acquires the image.

6. A calibration method comprising:
acquiring a first image including a first real linear line segment substantially perpendicular to a movement flat surface on which a movable body moves, from a camera installed on the movable body, at a first time;
extracting the first real linear line segment from the first image through image processing;
acquiring a second image including a second real linear line segment substantially perpendicular to the movement flat surface, at a second time after movement of the movable body after the first time, the second real linear line segment being based on a photographed object identical to that of the first real linear line segment;
extracting the second linear line segment from the second image through image processing;
calculating a first vanishing point from a first extended line of the first real linear line segment and a second extended line of the second real linear line segment and setting any point other than the first vanishing point as a second vanishing point;
calculating a vanishing line which passes through the first and second vanishing points;
calculating an installation parameter for the camera with respect to the movement flat surface, on a basis of coordinates of the first and second vanishing points and the vanishing line; and
transmitting the installation parameter;
wherein the camera measures the distance from the movable body to an object using the camera installation parameter.

7. The calibration apparatus according to claim 1 , wherein the two real linear line segments substantially perpendicular to the movement flat surface includes a range of required perpendicularity for calculating the camera installation parameter.

8. The calibration apparatus according to claim 1 , wherein the two real linear line segments are along a direction perpendicular to the movement flat surface, and are extending upwardly from the movement flat surface.

9. The calibration apparatus according to claim 1 , wherein the two real linear line segments are identical to a Y c axis of the camera extending upwardly from the camera, and along a direction perpendicular to the Z c axis and the X c axis.

10. The calibration apparatus according to claim 1 , wherein the two real linear line segments are two bars standing substantially perpendicular to the movement flat surface.

11. The calibration apparatus according to claim 1 ,
wherein the camera installation parameter with respect to the movement flat surface is calculated by the calculator by calculating a camera installation parameter with respect to a surface substantially perpendicular to the movement flat surface, on a basis of coordinates of the first vanishing point and the vanishing line, then transforming the camera installation parameter with respect to the surface substantially perpendicular to the movement flat surface into the camera installation parameter with respect to the movement flat surface.

12. The calibration apparatus according to claim 4 ,
wherein the camera installation parameter with respect to the movement flat surface is calculated by the calculator by calculating a camera installation parameter with respect to a surface substantially perpendicular to the movement flat surface, on a basis of coordinates of the first vanishing point and the vanishing line, then transforming the camera installation parameter with respect to the surface substantially perpendicular to the movement flat surface into the camera installation parameter with respect to the movement flat surface.

Assignees

• Panasonic Ip Man Co Ltd

Inventors

• Nakai Wataru

Classifications

• G06T11/23

  using straight lines or curves · CPC title

• G06T7/80 Primary

  Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration · CPC title

• G06T7/536

  from perspective effects, e.g. by using vanishing points · CPC title

• G06T2207/30252

  Vehicle exterior; Vicinity of vehicle · CPC title

• G06T2207/30244

  Camera pose · CPC title