Method and device for mapping radiation sources

• US 6,782,123 B1
• Filed: 12/14/1999
• Issued: 08/24/2004
• Est. Priority Date: 02/17/1997
• Status: Expired due to Fees

• Current Assignee: Compagnie Generale DES Etablissements Michelin SCA
• Original Assignee: Compagnie Generale DES Etablissements Michelin SCA
• Inventors: Dalancon, Thomas, Guillon, François, Baussart, Philippe
• Primary Examiner(s): Wu, Jingge
• Assistant Examiner(s): Hesseltine, Ryan J.
• Application Number:
  US09/355,956
• Time in Patent Office: 1,715 Days
• Field of Search: 382/154, 250/336.01, 250/393, 250/363.01, 250/366, 348/42, 348/46-48, 600/407, 600/436, 374/4, 378/41
• US Class Current: 382/154
• CPC Class Codes: G01C 11/06 by comparison of two or more pictures of the same area
• CPC Class Codes: G01T 7/00 Details of radiation-measuring instruments

Abstract

A method and apparatus for precisely locating radioactive sources. A pair of visual cameras are oriented in directions so that they have all or part of their field of vision in common. The apparatus also includes an intermediate camera which is sensitive to the radiation to be measured. The visual cameras make it possible to define the position of the details of the environment by a triangulation method and another triangulation is carried out in order to know the position of the sources after having moved the apparatus. Photogrammetry software is used to accomplish these tasks easily.

Claims

1. A method for mapping sources of radiation in a three-dimensional environment, comprising:

providing an assembly comprising a support, means for taking visual images, and means for taking images of the sources, said means for taking visual images and said means for taking images of the sources being secured together to the support;

determining relationships between respective positions and orientations of said means for taking visual images and said means for taking images of the sources;

taking at least two visual images of the environment at different angles of view with said assembly displaced at one imaging position and at least two images of the sources with said assembly displaced to at least two imaging positions;

establishing a three-dimensional model of the environment from said at least two visual images, identifying homologous elements in the at least two visual images, and then computing locations of said homologous elements;

determining lines of projection of the sources leading to the means for taking images of the sources for the at least two imaging positions;

locating said lines of projection in said three-dimensional model based on said relationships; and

computing positions of intersection points of said lines of projection in said three-dimensional model, which are positions of the sources.

2. A method according to claim 1, wherein said three-dimensional model of the environment is established using measurements of translation and rotation displacements of said assembly between said at least two imaging positions.

3. A method according to claim 1, further comprising:

a preliminary calibration comprising correcting any distortion in images by establishing a look-up table between points on the images and directions of sight of a known object at a given position of said means for taking visual images and said means for taking images of the sources.

4. A method according to claim 1, further comprising:

a preliminary calibration comprising assessing positions of optical centers of said means for taking visual images and said means for taking images of the sources with respect to a known object and assessing directions of central axes of sight of said means for taking visual images and said means for taking images of the sources.

5. A method for mapping sources of radiation in a three-dimensional environment, comprising:

providing an assembly comprising a support, two means for taking visual images, and one means for taking images of the sources, said two means for taking visual images being oriented in directions such that they have at least a part of their field of vision in common, said two means for taking visual images and said one means for taking images of the sources being secured together to the support;

determining relationships between respective positions and orientations of said two means for taking visual images and said one means for taking images of the sources, and relationships between respective positions and orientations of said two means for taking visual images;

taking at least two visual images of the environment with each of said two means for taking visual images with said assembly displaced at least at two imaging positions and at least two images of the sources with said assembly displaced to the respective two imaging positions;

establishing three-dimensional models of the environment from said at least two visual images for each one of said two means for taking visual images, identifying homologous elements in the visual images, and then computing locations of said homologous elements for each of said imaging positions;

determining lines of projection of the sources leading to said one means for taking images of the sources for the respective two imaging positions;

locating in each three-dimensional model said lines of projection determined for a same imaging position by using said relationships;

combining the three-dimensional models into an overall model and locating said lines of projection in said overall model; and

computing positions of intersection points of said lines of projection in said overall model, which are positions of the sources.

6. A method according to claim 5, wherein one of said two means for taking visual images is said means for taking images of the sources.

7. A method according to claim 5, wherein said overall model of the environment is established using measurements of translation and rotation displacements of said assembly between said imaging positions.

8. A method according to claim 5, further comprising:

a preliminary calibration comprising correcting any distortion in images by establishing a look-up table between points on the images and directions of sight of a known object at a given position of said two means for taking visual images and said one means for taking images of the sources.

9. A method according to claim 5, further comprising:

a preliminary calibration comprising assessing positions of optical centers of said two means for taking visual images and said one means for taking images of the sources with respect to a known object and assessing directions of central axes of sight of said two means for taking visual images and said one means for taking images of the sources.