Image analysis – Histogram processing – For setting a threshold
Patent
1987-01-02
1990-05-01
Boudreau, Leo H.
Image analysis
Histogram processing
For setting a threshold
382 45, 382 46, 382 18, 356152, 364768, G06K 900
Patent
active
049225430
DESCRIPTION:
BRIEF SUMMARY
The invention here described refers to an image processing device as specified in the introduction to claim 1.
A great deal of effort has been spent and is being spent in order to identify and determine the location and orientation of an object by measuring characteristics of an image of the object which is sensed by a TV-camera for example. Beside a number of military, medical and space applications the use of such a remote measuring technique is very attractive for automization tasks within the mechanical engineering industry.
The interest in workshop applications emanates, among other things, from the fact that many monotonous operations still have to be performed manually. The operator's vision and related coordination of action are in many cases very difficult to replace with technical means. Production with a significantly reduced work-force compared to the situation today seems to be difficult to realize until effective systems based on artificial vision are available at reasonable cost.
Mechanical production is a suitable field for image processing, due to the fact that one often has detailed knowledge about which objects one wishes to make measurements on and how their images will look when generated by a specified imaging sensor. It is also often possible to arrange illumination and background so that the objects will be seen clearly and with good contrast against the background.
The measuring set-ups can often be made fairly reproducable for periodic measurement, although variations of illumination and image variations due to the actual location of the object relative to the optical axis might cause difficulties. Unsophisticated image processing devices have only taken a small share of the market due to their tendency to fail too often. The development of sophisticated systems within this technical area is continuing especially for cooperation with industrial robots. One known robot vision system is marketed by the Swedish company ASEA. The image processor which is a part of this system extracts by digital filtering and picture noise suppressing algorithms, among other means, the contour lines from pictures from a TV-camera. The system is able to process scenes which are fairly weak in contrast. From the contours, the location and identity of the objects within the picture are determined as well as the objects' orientation relative to some reference direction. The contour-lines are compared during this process to contour data previously obtained from a reference object and processed and stored within the memory of the equipment.
There are other known systems, where the seeking process takes place in a memory containing previously stored data which describe characteristic details of the pictures of the objects (such as blobs) their area, ratio between area and circumference, the centre of gravity of the area etc., in order to make similar computations to those just referred to.
Systems of this latter type are rather demanding on the operator whose responsibility it is to "teach" the equipment how to solve its task by using reference objects taken from the production line. One example of such a system is "Machine Vision" originally developed at MIT in the U.S.A.
The previously known systems are complicated and expensive. The goal set up for the invention has been primarily to solve a class of workshop problems, which are simple from the image processing point of view and where low cost is essential. In spite of the requirements of low cost, one also wants a system of this kind to perform in a way that is easy to understand and easy to handle for an operator who has not been given specialist training. The requirements specified above are solved in accordance with the invention by equipment characterized by what is claimed under claim 1. Further improvements and developments are described in the following claims.
A graphic terminal nowadays usually works in a so-called raster-scan mode. That means that the displayed field is scanned line by line using standard TV-technology. The market for graphic t
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Ahlbom Sten Hugo Nils
Kennedy Bo E.
kerlind Bo N.
Boudreau Leo H.
Jung Yon
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