Image analysis – Applications – 3-d or stereo imaging analysis
Reexamination Certificate
1998-06-25
2001-12-04
Ahmed, Samir (Department: 2623)
Image analysis
Applications
3-d or stereo imaging analysis
Reexamination Certificate
active
06327380
ABSTRACT:
TECHNICAL FIELD
The present invention concerns the technical field of the three-dimensional measurement of objects in the general sense, performed with the aid of optical image-acquisition systems, and it relates more particularly to the measurement methods relying on the technique of fringe projection and analysis of the deformation of the fringes on the object.
The invention finds a particularly advantageous application in the field of measuring the parts of the human body, with a view to obtaining partial or full reproduction of the parts of the body which are measured.
In an application which is preferred, but not exclusive, the subject of the invention aims to measure, in three dimensions, the torso of an individual in order to perform the automated manufacture of orthopedic corsets.
PRIOR ART
In the field of measurement with the aid of image-acquisition systems, such as cameras, the situation often occurs, in numerous applications, that the angle of view of a camera is insufficient to cover the surface of the object to be acquired. In order to solve this problem, various pictures are taken and the images are correlated with one another.
A first technique for correlating images is proposed by patent application FR 88-15 483. This technique consists in fixing a marker on the object and, when taking the pictures, in displacing the camera relative to the object. In practice, placing a marker on the object proves to be an operation which is difficult to achieve, in particular when the object constitutes a part of an individual. It should be noted that errors may be made in the measurements, in particular in this type of application, because of the movement of the individuals when the pictures are being taken. In addition, the very principle of this method demands that the marker be constantly visible by the camera, which limits the field of view for taking pictures. This technique thus makes it impossible, in particular, to reconstruct a complete volume encompassing 360°.
In order to overcome the drawback of positioning a marker on the object, another technique for correlating images has been proposed, consisting in the use of a plurality of cameras whose positions, relative to one another, are known and predetermined. This method makes it necessary to take dimensional readings which prove to be time-consuming, difficult and tedious to achieve. In addition, the supports for the cameras must have a high degree of robustness and rigidity in order to keep the measurements accurate.
The object of the invention therefore aims to overcome the drawbacks of known techniques, by providing a method for correlating three-dimensional measurements given by at least two optical image-acquisition systems, affording the advantage of not having to employ markers on the object and not requiring dimensional readings to be made between said systems.
SUMMARY OF THE INVENTION
In order to achieve this object, the correlation method according to the invention consists, for the calibration phase:
in producing a standard sphere, mounted so as to move in rotation about an axis different than that passing through the center of the sphere;
in displacing the standard sphere by successive rotations in order to place it in at least first and second measurement positions which are visible simultaneously by the two optical image-acquisition systems;
in displacing the standard sphere by rotation in order to place it in at least one measurement position, which is visible by at least the first optical image-acquisition system and is different than the first and second measurement positions;
in displacing the standard sphere by rotation in order to place it in at least one measurement position, which is visible by at least the second optical image-acquisition system and is different than the first and second measurement positions;
in measuring, for each of the measurement positions, the cap of the standard sphere seen by each of the optical image-acquisition systems;
in determining, for each of the measurement positions, the center of the cap of the standard sphere seen by each of the optical image-acquisition systems, in order to make it possible to express the same reference system in a first coordinate frame seen by the first optical image-acquisition system, and in a second coordinate frame seen by the second optical image-acquisition system;
and in calculating the matrix of the transformation between the first and second coordinate frames, in order to make a correlation between the measurements of the first and second optical image-acquisition systems.
A method of this type thus makes it possible to calibrate at least two optical image-acquisition systems, making it possible to link, in a unique coordinate frame, the various surfaces measured by said systems.
Another object of the invention aims to improve the reconstruction of the surfaces which are observed, by eliminating the effects of shadows cast by the reliefs on the object, due to the illumination orientation.
In order to achieve this objective, the method according to the invention consists:
for at least one optical image-acquisition system, in using two sensors, each formed by a camera and a fringe projector;
and in making a correlation between the two sensors by using a plane delimiting a physical reference common to the two sensors.
Various other characteristics will emerge from the description, given below with reference to the appended drawings which show, by way of nonlimiting examples, embodiments and ways of implementing the subject of the invention.
REFERENCES:
patent: 5446798 (1995-08-01), Morita et al.
patent: 4-259809 (1992-09-01), None
Paul K. Commean et al., “Geometric design of multisensor structured light range digitizer”, Optical Engineering, vol. 33 No. 4, pp 1349-1358, Apr., 1994.*
Keith D. Gremban et al., “Geometric Camera Calibration Using Systems of Linear Equations”, Proceedings IEEE of Int. Conference on Robotics & Automation on Philadelphia USA, P562-567, 1988.
Divet Michel
Rolet Guy
Sciandra Jacques
Ahmed Samir
Dowell & Dowell , P.C.
Orten S.A.
LandOfFree
Method for the correlation of three dimensional measurements... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for the correlation of three dimensional measurements..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for the correlation of three dimensional measurements... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2556224