Optics: measuring and testing – Range or remote distance finding – Triangulation ranging to a point with one projected beam
Reexamination Certificate
1999-03-11
2002-03-19
Buczinski, Stephen C. (Department: 3662)
Optics: measuring and testing
Range or remote distance finding
Triangulation ranging to a point with one projected beam
C356S370000, C382S154000, C702S167000
Reexamination Certificate
active
06359680
ABSTRACT:
The invention concerns a process for the three-dimensional measurement of objects through optical exposures, projected patterns, and calculations of triangulation, in which the devices for the projection of the pattern and for the image capture are constructed separately from one another and can, for the measurement, be positioned independently of one another.
Furthermore, the invention concerns a device for such a process.
The use of processes that work on an optical basis offer a multiplicity of advantages for the purpose of measuring. A measurement can be carried out quickly and without contact. Electronic image converters, such as CCD arrays, for example, the output signals of which can be stored or evaluated after digitalization, already belong to the state of the art.
Processes and devices for the representation and three-dimensional optical measurement of spatial surfaces are already known. These are based upon triangulation processes in which patterns of points, lines, or any other chosen patterns are projected, at a certain angle, onto the surface under consideration, and the projected patterns are captured, under another viewing angle, by means of an optical device and an image converter. The known geometry between the direction of projection and the direction of capture permits the three-dimensional calculation of support points of the surface.
If a uniform pattern of lines is projected onto an object with spatial extensions, for example, then, because of the surface shape of the object, a distorted line pattern is brought about in a direction of view which is different from the direction of projection. If the object is represented from this direction of consideration on a CCD-array by means of a suitable optical device, and the image signals are digitalized and made available to a data processing unit, then it is possible to identify the lines at the various points of the image and, given a knowledge of the optical path of the rays, and under consideration to the geometrical configuration of the projected pattern of lines, to compute the 3D coordinates by means of triangulation.
In the capture of several individual images with different directions of capture, it is already state of the art to combine the partial information obtained about three-dimensional surfaces by means of the 3D coordinates of corresponding surface segments into a total information by means of so-called “registration-algorithms”.
It is now desirable to do the following for endoscopic investigations, for example:
a) To use a separate unit for the projection of the pattern and for the capture of the image, and to use this with an orientation that is freely selectable in relation to the surface to be measured. In order to obtain relevant data for the calculation of the triangulation, a minimum angle between the orientation of both of the units should not be fallen short of in this connection;
b) Insofar as a series of individual images is captured during the capture process, to change the position and orientation of both of the units independently of one another in relation to the object, such as for the simplification of the handling, for example, in order to be able to measure additional surface areas by means of additional image captures.
It is thus the task of the invention to create the process and the device for the three-dimensional measurement of objects of the type just described, in which the position and orientation of the image capture unit and of the projection unit can be adjusted to one another and, in the event that more than one capture is useful for this purpose, to follow the independent movement of the two units towards one another that has taken place during the course of the capture process. The geometrical connection between the image capture and the pattern projection determined for the specific individual image must then be taken into consideration for the calculation of triangulation.
This task is solved, in accordance with the invention, through the fact that:
a) Through the use of an electronic surface image converter, a capture process is carried out;
b) Through the use of a source of beams and suitable optical devices, a pattern is projected onto the object at an angle which is different from the direction of capture that is to be measured;
c) Through the use of a suitable unit, the output signals of the image converter are digitalized, and these data are made available to a data processing apparatus;
d) Through the use of a data processing apparatus, 3D coordinates of the points of the surface of the object to be measured are determined, by means of suitable circuits and/or algorithms, through calculations of triangulation from the image data of the individual images;
while additional devices are provided in such a manner, and/or the process coming for use and/or the devices are configured in such a manner, that the position and the orientation of the image capture unit and of the projection unit to one another can be determined. If the position and the orientation of both units to one another is known, then, for the capture of an individual image, 3D coordinates can be determined by means of a triangulation calculation, in the known manner and method, for a number of points of the surface.
It is, in accordance with the invention, advantageous to use additional devices for this purpose in order to measure the position and the orientation of the image capture unit and of the projection unit to one another.
In accordance with the invention, this can be carried out, in an advantageous manner, both directly as well as indirectly, both by means of scanning or in connection with measuring means, as well as without contact, such as by optical means, for example.
If information on the object which is additional to that information acquired from an individual exposure is now to be determined, then the image capture unit must be able to record a sequence of individual images. For the task in accordance with the invention, namely, that the projection unit and the image capture unit are moved differently during the course of the image capture process, the devices and/or processes in accordance with the invention must, in an advantageous manner, be configured in such a manner that the geometrical configuration of the image capture unit and of projection unit can be adjusted to one another for the sequential images.
This can, in accordance with the invention, be advantageously guaranteed through the fact that the above-stated measuring devices are also evaluated at the point in time of the exposures that are additionally carried out, and the measuring results are taken into consideration, in the way and manner described above, in the calculation of triangulation.
For the event that, in the sequence of the individual images, the object is recorded in such a manner that the 3D coordinates determined from the individual images describe surface segments that are in agreement to a considerable degree, then—as has been described above—the specific 3D information can be combined by means of “registration algorithms” corresponding to the state of the art.
If the capture of the individual images takes place in rapid sequence, then, with a corresponding handling of the units, it can be assumed that—first of all—the portion of corresponding surface segments is sufficient and—secondly—that the geometrical correspondence of the image capture unit and of the projection unit to one another has only been altered in extent in relation to the previous capture.
If, therefore, the coordination of both units in the first capture was known, for example, and if a considerable number of 3D coordinates describing the surface could be computed, then the information contained in the next capture differs in the following components:
a) The 3D coordinates of the corresponding surface segments can be represented displaced linearly in the three spatial directions;
b) The 3D coordinates of the corresponding surface segments can be represented displaced in a rotational manner in relation to the three spatial di
Buczinski Stephen C.
McDonnell & Boehnen Hulbert & Berghoff
OraMetrix Inc.
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