CALIBRATION METHOD, CALIBRATION DEVICE, AND COMPUTER PROGRAM PRODUCT

• US 20170070725A1
• Filed: 02/24/2015
• Published: 03/09/2017
• Est. Priority Date: 03/07/2014
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Jun Kishiwada, Kagehiro Nagao, Naoki Kikuchi, Shin Aoki
• Inventors: NAGAO, Kagehiro, KISHIWADA, Jun, AOKI, Shin, KIKUCHI, Naoki
• Granted Patent: US 10,218,961 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B60R 11/04 Mounting of cameras operative during drive; Arrangement of controls thereof relative to the vehicle
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 2207/30208 Marker matrix
• CPC Class Codes: G06T 2207/30252 Vehicle exterior; Vicinity of vehicle
• CPC Class Codes: G06T 7/85 Stereo camera calibration
• CPC Class Codes: H04N 13/239 using two 2D image sensors having a relative position equal to or related to the interocular distance H04N13/243 takes precedence
• CPC Class Codes: H04N 13/246 Calibration of cameras

Abstract

A calibration method is for a photographic device that photographs an object through a transparent body. The calibration method includes: acquiring a first photographic image by photographing the object without interposing the transparent body; acquiring a second photographic image by photographing the object through the transparent body; calculating an absolute positional deviation that indicates a deviation in coordinates of an image of the object due to the transparent body based on coordinates of an image of the object on the first photographic image and coordinates of an image of the object on the second photographic image; calculating a correction parameter for calibrating the absolute positional deviation; and storing the correction parameter in the photographic device.

Claims

1. A calibration method for a photographic device that photographs an object through a transparent body, the calibration method comprising:

acquiring a first photographic image by photographing the object without interposing the transparent body;

acquiring a second photographic image by photographing the object through the transparent body;

calculating an absolute positional deviation that indicates a deviation in coordinates of an image of the object due to the transparent body based on coordinates of an image of the object on the first photographic image and coordinates of an image of the object on the second photographic image;

calculating a correction parameter for calibrating the absolute positional deviation; and

storing the correction parameter in the photographic device.

2. The calibration method according to claim 1, wherein

the photographic device is a stereo camera including a first camera and a second camera;

the calculating of the absolute positional deviation includes;

calculating the absolute positional deviation in the first camera based on coordinates of an image of the object on the first photographic image photographed by the first camera and coordinates of an image of the object on the second photographic image photographed by the first camera, and

calculating the absolute positional deviation in the second camera based on coordinates of an image of the object on the first photographic image photographed by the second camera and coordinates of an image of the object on the second photographic image photographed by the second camera;

at the calculating of the correction parameter, a first correction parameter for calibrating the absolute positional deviation in the first camera and a second correction parameter for calibrating the absolute positional deviation in the second camera are calculated; and

at the storing, the first camera correction parameter and the second camera correction parameter are stored in the stereo camera.

3. The calibration method according to claim 2, further comprising:

calculating a third correction parameter for calibrating a relative positional deviation indicating a deviation in a parallax between the image of the object in the second photographic image photographed by the first camera and the image of the object in the second photographic image photographed by the second camera; and

updating the first correction parameter based on the third correction parameter.

4. The calibration method according to claim 1, wherein the transparent body is a windshield of a vehicle.

5. The calibration method according to claim 1, wherein the object photographed at the acquiring of the first photographic image and the object photographed at the acquiring of the second photographic image are a calibration tool that has a pattern for facilitating detection of coordinates on the second photographic image that correspond to coordinates on the first photographic image.

6. A calibration device that calibrates a photographic device that photographs an object through a transparent body, the calibration device comprising;

a receiving unit that receives a first photographic image obtained by photographing the object photographed without interposing the transparent body and a second photographic image obtained by photographing the object through the transparent body;

an absolute positional deviation calculating unit that calculates an absolute positional deviation indicating deviation in coordinates of an image of the object due to the transparent body based on coordinates of an image of the object on the first photographic image and coordinates of an image of the object on the second photographic image;

a correction parameter calculating unit that calculates a correction parameter for calibrating the absolute positional deviation; and

a memory control unit that stores the correction parameter in the photographic device.

7. A computer program product comprising a non-transitory computer-readable medium having computer readable program codes, the program codes when executed causing a computer that calibrates a photographic device that photographs an object through a transparent body to perform:

receiving a first photographic image obtained by photographing the object without interposing the transparent body and a second photographic image obtained by photographing the object through the transparent body;

calculating an absolute positional deviation indicating a deviation in coordinates of an image of the object due to the transparent body based on coordinates of an image of the object on the first photographic image and coordinates of an image of the object on the second photographic image;

calculating a correction parameter for calibrating the absolute positional deviation; and

storing the correction parameter in the photographic device.