Optics: measuring and testing – By configuration comparison – With photosensitive film or plate
Reexamination Certificate
2000-04-28
2001-09-04
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
By configuration comparison
With photosensitive film or plate
C250S559270
Reexamination Certificate
active
06285451
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of determining the thickness of an article by employing a noncontacting means and associated apparatus; and more specifically, it relates to such a system for determining wall thickness of transparent articles or portions of articles.
2. Description of the Prior Art
There are a number of known systems for measuring the thickness of transparent objects. These can be divided into two categories, (a) those that contact the object such as capacitive sensors, and (b) those that are noncontacting that measure reflection, scattering, or absorption of radiation. Noncontact techniques have been developed for measuring objects that have well-defined relationships of the inner and outer surfaces such as the cylindrical and coaxial surfaces of drawn glass tubing, some molded containers, and the parallel surfaces of plate glass, for example. For accurately measuring the thickness of irregular objects such as most molded containers, available techniques have been limited.
U.S. Pat. No. 5,636,027 discloses a noncontacting thickness measurement apparatus wherein reflected light is measured by sensing means in order to determine thickness of object made of transparent material. Beam splitters are also employed. See also U.S. Pat. No. 4,902,902.
U.S. Pat. No. 5,291,271 is directed toward measurement of wall thickness of a transparent container employing laser light and sensors receiving light reflected from the surface of the container at a first point and refracted into the container emerging at a second point with a view toward determining thickness.
U.S. Pat. No. 4,822,171 shows a noncontact method to measure wall thickness of a transparent article by projecting a narrow band of light in a longitudinal direction employing sensors that receive light reflected from the surface of the article and refracted into the container emerging at a second portion of the article.
In spite of the foregoing known systems, there remains a need for providing an improved means for measuring the thickness of transparent articles.
SUMMARY OF THE INVENTION
The present invention solves the above-described problems by providing a method of inspecting an article which includes directing a light beam having generally parallel rays onto a first portion or point of the exterior surface (first surface) of the article, directing reflected light from the first portion or point onto a first sensor with an optical system, establishing relative movement between the light beam and the article until the refracted light entering the article reflects from a rear surface of the article and is refracted out of said first portion and onto said first sensor and employing the reflected and refracted light to determine wall thickness of the article at the point. The relative movement between the article and the beam may be the beam moving in a direction generally perpendicular to the beam direction or may be through movement of the article as by translation thereof, for example.
The method may be employed to determine the angles of the walls being measured.
The article may be a hollow article such as a container or a tube composed of a transparent material.
The apparatus for inspecting the article in the present invention includes a light source, an optical system, and a first sensor for receiving light reflected from a first point on the exterior surface of the article and converting the reflected light into a corresponding electrical signal. The first sensor also receives light refracting into the article, which is reflected from the rear surface, which exits through the first point and converts the refracted light into a corresponding electrical signal. A processor means is used to convert the reflected and refracted light into a determination of wall thickness at the first point. The angles of the walls may also be determined.
It is an object of this invention to provide a noncontacting system for accurately measuring the thickness of transparent hollow objects.
It is a further object of the invention to provide thickness measurement of irregular surfaces of different diameters where only a small portion of the circumference of the container is accessible.
It is yet another object of the present invention to permit simultaneous measurement of the angles of the walls and thickness thereof.
It is yet another object of the present invention to provide such a system which permits greater lateral displacement of the article being inspected due to the use of a scanning beam.
It is a further object of the present invention to provide such a system, which minimizes focus and positional errors.
These and other objects of the invention will be more fully understood from the following description of the invention with reference to the figures appended hereto.
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Pham Hoa Q.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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