Optics: measuring and testing – By configuration comparison – With photosensitive film or plate
Patent
1996-03-15
1997-10-21
Rosenberger, Richard A.
Optics: measuring and testing
By configuration comparison
With photosensitive film or plate
25055925, G01B 1100
Patent
active
056802196
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a device for automatic, contactless and optical video measurement of the dimension of one or more objects being at rest, or being conveyed in parallel position along a straight path.
General description of the device, in this case used as sawn timber controller at a saw mill:
SUMMARY OF THE INVENTION
The invention could be used at e.g. a saw mill for continuous measurement of the saw-cuts (kerfs) in a block being sawn. The purpose is that an operator at the saw mill is informed of the actual values, and that an alarm is given if actual values differ more from the reference values set than a predetermined limit value. Also, the departure between actual value and reference value is to be used such that this value is transmitted to the saw controller system in order to correct the position of the saws.
The kerf controller in FIG. 1 measures contactless and simultaneously up to 10 parallel planks (in front edge of block during sawing) while these are moving, and without the use of any movable or rotating mechanical parts.
The measuring time for each single kerf is maximum 25 micro second. When measuring one unit only, 50 micro seconds are allowed to be used. As the measurements occur so rapidly, a major part of the problems linked to erroneous measurement caused by the fact that the measured object vibrates such that it displaces itself with or against the line search direction in the course of the search time. The measurements can be repeated at choosable intervals, and in those cases where the objects to be measured can be assumed to have such a high displacement speed in or toward the measuring direction that it would have significant effects on the measuring results, one may, by means of statistical calculations within the program communicating with the device, within frames, filter away the measuring deviations caused thereby. The system uses parabola-shaped mirrors of 4-6 mm thick tempered glass. Thereby, erroneous measurements otherwise arising due to the camera objective's opening angle and varying distance to the measured object are avoided. In this system, only a few individual components are included. All components are easily replaceable.
What is particularly achieved is that the saw mill, in the assurance that an alarm will be given upon deviations, can allow that one constantly saws using smaller margins (smaller excess dimensions). One could eliminate the problem of having to stop the sawing while carrying out manual sample controls. One avoids that some of the kerf must be discarded due to the fact that the saws or the adjustment thereof, have not been satisfactory for a period. Otherwise, one achieves a contactless, rapid and accurate measurement by means of a compact device. The latter is partly caused by the components used, and the way these are assembled; this being described later on.
In order to achieve this, two parabola-shaped mirrors 3, 4 according to FIG. 2 are required, the mirror coating being on the concave side, and thusly arranged that they, longitudinally, are located parallel with each other, the concave sides opposing each other under a mutual angle of 90.degree. in the planes of the short sides of the mirrors. Further, it is required that a video CCD camera 5 is positioned such that the same, on some of the search lines, records a difference in the levels of the intensity of light beams coming from a measured object 7, and being reflected through both the two said parabola-shaped mirrors 3, 4. Additionally, two elongated light sources 1, 2 are required, placed laterally of and above, alternatively below, the measured object 7, such that the angle of the light sources in a plane perpendicularly to the measured object's direction of motion is 45.degree.. The light sources are placed in this way in order to let the saw-cuts appear in the greatest possible contrast and, thereby, easier recordable by the video camera 5. It is further required that the video signal by means of electronics is converted into TTL logic
REFERENCES:
patent: 4179707 (1979-12-01), Sjodin
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