Image analysis – Applications – 3-d or stereo imaging analysis
Reexamination Certificate
2000-04-21
2003-09-09
Ahmed, Samir (Department: 2623)
Image analysis
Applications
3-d or stereo imaging analysis
C382S152000
Reexamination Certificate
active
06618496
ABSTRACT:
This application claims Paris Convention priority of DE 299 18 341 filed Oct. 18, 1999 the complete disclosure of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
The present invention concerns a device for determining the position of measuring points of a measuring object, comprising a measuring means for determining the position of the measuring points relative to the position of the measuring means, and a reference measuring means for determining the position of the measuring means relative to a reference system.
A device of this kind is disclosed in DE 197 21 903 C1. In the device disclosed therein, the measuring means is formed as a probe with a probe tip. The measuring points of a measuring object are measured by touching the individual measuring points, one after the other, with the probe tip. The position of the probe in a reference system is determined by a reference measuring means rigidly connected to the probe.
The reference measuring means comprises three electronic cameras displaced from one another which detect special measuring symbols in the reference system. The position of the probe tip in the reference system is determined photogrammetrically from the position of the measuring symbols. The conventional device can thereby determine the position of the probe tip and therefore the position of a measuring point relative to the reference system. This can be done, in particular, online, wherein the signal values of the cameras for each measuring point are passed on to a processing means, in which the positions of the measuring points are determined.
If the shape and the position (position and orientation) of at least part of a measuring object is to be determined in three-dimensional space, the conventional device has to detect the position of at least six measuring points of the measuring object, one after the other. If e.g. the shape and position of a circular depression in the measuring object has to be measured, the probe tip must be initially positioned to at least three different measuring points, one after another, from the inside to the edge of the depression for determining the shape of the depression, and the positions of the measuring points must be determined by the processing means. For determining the position of the depress ion in three-dimensional space, the probe tip is subsequently disposed at at least three different measuring points, one after another, outside of the depression on a surface of the measuring object and the positions of the measuring points are again determined. It is easy to imagine that measurement of the shape and position of complex patterns, in particular measuring object geometries which have polygonal substructures, is considerably more demanding.
The recording of a plurality of measuring points for determining the shape and position of an individual measuring object requires a substantial amount of time and work. In addition, the conventional method for determining the position of the measuring points of a measuring object is susceptible to errors generated when the probe tip does not properly seat at a measuring point. This may occur e.g. with poorly accessible measuring points or if determination of the position of the probe tip relative to the reference system is triggered, although the probe tip is still moving towards the measuring point or has already departed therefrom.
A further disadvantage is that the conventional device only allows measurement of measuring objects made from materials which do not yield when the probe tip is supported thereon. For this reason, it is not possible to measure measuring objects made from a flexible material, such as e.g. foamed material or rubber. Nor can patterns on flat surfaces of a measuring object be measured with the conventional device, since a lateral supporting surface for the probe tip is required to determine the shape of the structure (in the above-mentioned example e.g. the edge of the depression) which is not present on a flat surface. For this reason, the patterns disposed on a glass ceramic cooker for delimiting the individual cooking fields cannot be measured with the conventional device.
A further disadvantage of the conventional device is the excessively demanding design of the reference measuring system. At first, a target surface rigidly connected to the reference system must be provided, with the measuring symbols disposed thereon. The rigid connection between the target surface and the reference system must be maintained at all times and the measuring symbols must be disposed very precisely on the target surface, since otherwise the determination of the position of the measuring points would be erroneous. In addition, the photogrammetric method of the conventional device for determining the position of the probe tip from the detected measuring symbols (e.g. so-called inverse photogrammetry) is very demanding and requires an excessive amount of time and calculation.
It is therefore the underlying purpose of the present invention to facilitate, design, and develop a device of the above mentioned kind such that any measuring object, in particular comprising surfaces of any design and consisting of any material, can be measured.
SUMMARY OF THE INVENTION
In achieving this object in accordance with the invention and departing from the device of the above mentioned kind:
the reference measuring means is a measuring arm or a robot arm, the proximal end of which is fixed relative to the reference system; and
the measuring means is an optical sensor means disposed at the distal end of the measuring arm or robot arm;
wherein the optical sensor means comprises at least two single or multiple image sensors recording images of at least part of the measuring object; and
the device comprises a processing means which determines the position of the measuring points of the measuring object from the recorded images;
wherein processing of the recorded images is carried out in real time with the recording frequency of the single or multiple image sensors (real time processing).
The device in accordance with the invention advantageously combines a highly accurate and high-speed optical sensor means of simple design with a measuring or robot arm of simple design and with easy handling. A device of simple construction which can measure any measuring object in a straight forward fashion, in particular one having surfaces of any design and consisting of any material, is thereby obtained.
The measuring arm comprises several elements pivotably attached to one another. The proximal end of the measuring arm is disposed in a reference system. The distal end of the measuring arm can be moved with several degrees of freedom. The measuring arm is usually moved manually by a user. The number of positions to which the measuring arm can be moved depends on the number of elements and the number and kind of joints between the elements. The measuring arm comprises sensors which detect a motion of the joints and are preferably disposed in the area of the joints. The sensor signals are guided to a processing means which uses the sensor signals to determine the position of the distal end of the measuring arm relative to the reference system. The measuring arms used for the present invention are sold e.g. by the company Faro, Lake Mary, Fla., USA (http://www.faro.com) under the name FaroArm.
Alternatively, a robot arm can be used instead of a measuring arm, which also comprises several jointed elements and is disposed with its proximal end in a reference system. The distal end of the robot arm can be moved with several degrees of freedom. Towards this end, the robot arm has a number of actuators which are controlled by the processing means such that the distal end of the robot arm assumes a predetermined position. The number of positions to which the robot arm can be moved depends on the number of elements and the number and kind of the joints between the elements. For determining the position of the distal end, the robot arm may have sensors which detect a motion of the joints an
Karaivazoglou Efstratios
Tassakos Charalambos
Ahmed Samir
Bali Vikkram
Tassakos Charalambos
Vincent Paul
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