Optics: measuring and testing – Plural test
Reexamination Certificate
2001-03-05
2002-04-16
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Plural test
Reexamination Certificate
active
06373561
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a device and a method for detecting depth and color information of an object.
Such a device and such a method are extremely important in the field of quality assurance during a process for producing an object, since the depth information can be used to detect whether or not the object has a shape defect. An optical 3D measurement method is customarily used to detect the depth information.
Laser triangulation is disclosed as a 3D measurement method by a book entitled: Bildverarbeitung und optische Me&bgr;technik [Image Processing and Optical Measurement Techniques] by B. Breuckmann, Franzis Verlag, 1993, ISBN 3-7723-4861-0, pp. 127-128. A laser is used to project a light point onto an object to be measured. A light beam reflected from the object to be measured is received by a photosensitive detector. The position of the object which is point marked by the light beam is calculated by triangulation from the geometry of the measurement setup and an angle between the projection direction of the laser and the direction of the light beam reflected from the object. The term “projection direction of the laser” is intended to mean an axis along which the laser is aligned and along which the laser beam is projected.
The object can be measured two-dimensionally by scanning the laser beam, i.e. guiding the laser beam line-by-line over the surface of an object. In general, an elaborate opto-mechanical system is needed for scanning the laser beam.
Another disadvantage of laser triangulation is the measurement time needed for measuring an object. In the case of measuring a moving object, the measurement speed that can be achieved in the scope of laser triangulation is insufficient to measure the object fully.
Furthermore, laser triangulation is unsuitable for measuring a person, since a laser beam striking one of the person's eyes can cause damage to the eye.
An improvement of the measurement method for detecting depth information of an object, with respect to the disadvantages mentioned above, is obtained by changing from a point projection method to an extended projection method. That approach is the basis for a topometric measurement method using structured light, as is disclosed by the book entitled: Bildverarbeitung und optische Me&bgr;technik [Image Processing and Optical Measurement Techniques] by B. Breuckmann, Franzis Verlag, 1993, ISBN 3-7723-4861-0, pp. 129-138.
In a topometric measurement method using structured light, a predeterminable pattern (structure) is projected onto an object to be measured through the use of a projector and through the use of a transparent support which carries the pattern and is fitted in front of or behind the lens of the projector. The object pattern which becomes visible on the object to be measured is captured by a video camera. The position of the associated object point can be determined quantitatively for each pixel in the video-camera picture according to the laws of triangulation with the aid of the recorded picture and the pattern which is visible thereon.
In the case of a stripe projection method according to product information sheets for the Line Projector Type LCD-320, AWB GmbH, Gutenbergstra&bgr;e 9, D-72636 Frickenhausen [Germany], February 1998, a periodic grid is projected onto an object. A stripe pattern which becomes visible on the object is captured by a camera, which is disposed at a predetermined angle with respect to the projection direction. In that case, the projected periodic grid is selected in such a way that the geometry of the stripes which become visible can be identified by using the camera. The position of the associated object point can be determined quantitatively for each pixel in the camera picture according to the laws of triangulation with the aid of the recorded stripe picture.
The methodology for positional determination of an object in the scope of the stripe projection method will be summarized below with the aid of FIG.
2
. The stripe projection method also has disadvantages.
Since the stripe projection method requires the projection of a visible stripe pattern onto an object, further optical analysis which may possibly need to be carried out at the same time as the detection of the depth information of the object, for example analysis with respect to the color of the object, is no longer possible.
A color Charge-Coupled-Device camera (color CCD camera) is generally used to detect color information of an object. A digital red-green-blue color CCD camera (RGB color CCD camera) is disclosed by product information sheets entitled: EHD RGB Color CCD Camera TK-1270E, http://www.ehd.de/tk-1270.htm, September 1997.
That digital RGB color CCD camera delivers digital camera pictures with a resolution of 752×582 effective pixels. Color information is assigned to each pixel for storing or further processing a digital picture in the scope of image processing. It is determined from the RGB intensity composition of a color hue at a surveyed object point. The term “RGB intensity composition” is intended to mean an intensity which corresponds to superposition of a first spectral color red, a second spectral color green and a third spectral color blue with their respective intensities resulting in a specific color hue.
Expressed more clearly, any color hue can be produced by superposition of the first spectral color red, the second spectral color green and the third spectral color blue with known respective intensities.
The camera has three acquisition channels, each having a CCD chip which is used to determine the corresponding intensity of the first spectral color red, the second spectral color green and the third spectral color blue of a color hue of a light beam which is reflected from an object point and then strikes the camera.
Furthermore, product information sheets entitled: Richter Enterprises Solution for Optics & Imaging, Optical Prism Assembly Data Sheet, November 1994, disclose a modification of a color CCD camera. That camera has an additional acquisition channel with a CCD chip which registers the intensity of an infrared beam striking a pixel of the camera.
It is possible to determine color information of a surveyed object by using the color CCD cameras presented above.
In order to carry out comprehensive quality assurance of a production process, it would be desirable to have a measurement system with which it is easy to determine depth and color information of an object.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a device and a method for detecting depth and color information of an object to be surveyed, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and which provide a simple way of detecting depth information and color information of an object to be surveyed.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for detecting depth and color information of an object to be surveyed, comprising a projection unit which is constructed in such a way that a predetermined radiation pattern (wave pattern) having first waves with at least one first wavelength in a spectral range outside the light visible to a human, can be projected. A collector unit includes at least one first and one second subunit. The first subunit is constructed in such a way that the first waves can be processed, and the second subunit is constructed in such a way that second waves, which have at least one second wavelength in the spectral range of the light visible to a human, can be processed. An evaluation unit, which is coupled to the collector unit, is constructed in such a way that the depth and color information of the object, from which the first waves and/or the second waves are at least partially reflected, can be detected from signals received by the collector unit.
With the objects of the invention in view, there is also provided a method for detecting
Font Frank G.
Greenberg Laurence A.
Lerner Herbert L.
Stafira Michael P.
Stemer Werner H.
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