Method for calibrating a stereoscopic photography device

• US 9,787,970 B2
• Filed: 02/22/2012
• Issued: 10/10/2017
• Est. Priority Date: 02/24/2011
• Status: Active Grant

• Current Assignee: Nintendo European Research And Development
• Original Assignee: Nintendo European Research And Development
• Inventors: Delattre, Alexandre, Larrieu, Jrme
• Primary Examiner(s): Kalapodas, Dramos I
• Application Number:
  US14/000,483
• Publication Number:
  US 20140204181A1
• Time in Patent Office: 2,057 Days
• CPC Class Codes: G06T 2207/10012 Stereo images
• 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

The present invention concerns the field of stereoscopic photography devices and more precisely calibration thereof.

The invention proposes a method for calibrating a stereoscopic photography device that calculates a set of correction parameters for the images. These parameters are classed according to an order of importance. The first-order correction parameters are estimated first, the second-order correction parameters secondly. Advantageously, the first-order parameters are refined by taking account of the estimation values of the second-order parameters. Advantageously, a measurement of the relevance of the scene is carried out before the actual calibration.

Claims

1. Calibration method for calibrating a stereoscopic photography device having a right camera for capturing a right-hand image and a left camera for capturing a left-hand image, at least four orders from lowest to highest of defects appearing between the right and left hand images, the defects comprising at least a global translation offset of the image, a horizontal and vertical trapezium deformation, a rotation, and a zoom factor, each of these defects being able to be corrected by applying a transformation to at least one of the two captured images, the method comprising the steps of:

calculating a relevance index to determine a scene for implementing the calibration method, and for the determined scene performing the following;

a) estimating the correction parameters for the defects of at least one lower order;

b) estimating the correction parameters for the defects of a higher order using the estimated correction parameters for the defects of the at least one lower order;

c) re-estimating the correction parameters for the defects of the at least one lower order using the estimated correction parameters for the defects of the higher order;

d) re-estimating the correction parameters for the defects of the higher order using the re-estimated correction parameters for the defects of the at least one lower order; and

e) estimating the correction parameters for the defects of a next higher order using the re-estimated correction parameters for the at least two lower orders.

2. Calibration method according to claim 1, further comprising a fifth order of defects to be corrected of

a barrel or pincushion distortion.

3. Calibration method according to claim 1, characterized in that the calculation of an index of relevance of the scene comprises the steps of:

calculating histograms of the right and left images, each histogram comprising a spread relating to the level of detail of a scene;

calculating, for each area of the plurality of areas of the left and right images, a parallax index and a correlation reliability index;

calculating, from the spreads of the histograms and from the correlation reliability indices, a detail index of the scene;

calculating, from the parallax indices, a distance index that will be greater, the more the parallax indices are uniformly low; and

calculating, from the detail index and the distance index the relevance index.

4. Calibration method according to claim 1, further comprising a step of repeating steps c) and d) until convergence of the estimation of the parameters is obtained, before proceeding to step e).

5. Calibration method according to claim 1, further comprising a step of displaying the calculated relevance index on a screen of the device.

6. Calibration method according to claim 5, wherein the relevance index is a relevance bar the length of which is proportional to the relevance index.

7. Calibration method according to claim 6, wherein the color of the bar is used to determine zones for the relevance index.