Reticle for an object measurement system

Optics: measuring and testing – By configuration comparison – With object being compared and scale superimposed

Reexamination Certificate

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Details

C250S201100

Reexamination Certificate

active

06246478

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a reticle for an object measurement system, an object measurement system and a method of measuring an object. The reticle, in particular, allows an image measurement system to be self-calibrating and self-aligning.
BACKGROUND OF THE INVENTION
When digitising images, such as photographs, it is desirable to be able to automatically measure the size of the object being imaged so that the image may be reproduced to scale. When a camera is used to capture images of objects of different sizes, then an operator will often zoom in on the image, by varying the camera lens focal length, so that the object image fills as much of the viewfinder as possible. This allows for greater reproduction of picture quality because more image information is captured at source. It means, however, that the actual size of the object is independent of its size in captured image coordinates, pixels. To measure such an object accurately, it would normally be necessary to know the focal length of the lens, to determine image magnification and thus calculate the size of the object in absolute coordinates (millimeters).
Use of reticles to assist in determining the size of objects under magnification is well known. It is common to see a printed scale superimposed on images to enable a viewer to determine the size of an object, for example, a transparent ruler. Printed scales, however, are of little use in enabling a computer to determine the absolute size of an object being imaged when the magnification achieved by a zoom lens camera for each image is an unknown variable.
It is an object of the present invention to mitigate such problems.
DISCLOSURE OF THE INVENTION
According to a first aspect of the invention, there is provided a reticle for an object measurement system comprising a pattern having one or more pairs of contrasting elements, the or each pair of contrasting elements defining a path such that an edge of an object occluding said path causes a change in contrast adjacent an edge point along said path, the pattern having a coded element associated with the or each pair of contrasting elements, the or each coded element being indicative of an absolute coordinate of the or each edge point at which an object edge crosses a path.
In a further aspect there is provided an object measurement system including the reticle according to the invention.
In a yet further aspect there is provided a method of measuring an object placed on the reticle according to the invention.


REFERENCES:
patent: 2484103 (1949-10-01), Lewis
patent: 4621256 (1986-11-01), Rusk
patent: 4908656 (1990-03-01), Suwa et al.
patent: 5300786 (1994-04-01), Brunner et al.
patent: 5389774 (1995-02-01), Gelman et al.
patent: 5933239 (1999-08-01), Hoshiyama

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