Image analysis – Applications
Reexamination Certificate
1998-11-30
2001-05-22
Johns, Andrew W. (Department: 2721)
Image analysis
Applications
C392S488000
Reexamination Certificate
active
06236734
ABSTRACT:
DETECTION OF DEFECTS IN GLASS
This invention relates to a method and apparatus for detection of defects in glass. In particular, the invention is directed to a method and apparatus for locating nickel sulphide stones in tempered plate glass, although the invention is not limited to this particular use.
BACKGROUND ART
Nickel sulphide (NiS) stones are sometimes found as impurities in glass. It is known that such nickel sulphide stones cause spontaneous fracture in toughened window glass. The spontaneous fracture can cause serious problems in high-rise office buildings, where large areas of glass are used.
It is very difficult to detect the presence of NiS stones at the time of glass manufacture. The glass scanners on the glass production line cannot detect stones smaller than 1 mm in size. NiS is not a common impurity in glass and when it does occur, the stones range in size from 0.1 to 0.6 mm. It is believed that any nickel sulphide stone of diameter greater than 70 &mgr;m is capable of breaking toughened glass, but stones smaller than 70 &mgr;m do not normally break the glass.
Most batches of glass have very few nickel sulphide stones, but occasionally bad batches are produced. Problems resulting from the nickel sulphide impurities often do not become apparent until that glass is placed onto a building many months after manufacture. Consequently, it is very difficult for glass manufacturers to track down what actually caused the high incidence of NiS in that particular batch.
The applicant's earlier international patent application no. PCT/AU93/00498 described a method of detection of defects in glass under controlled lighting conditions. (The disclosure of that patent application is incorporated herein by reference). Although the method described in international patent application no. PCT/AU93/00498 was able to locate the majority of nickel sulphide stones in window glass, the method had a number of inherent disadvantages.
First, the method was conducted entirely on site, and hence was dependent on weather conditions. Secondly, the method was tedious and time consuming. Thirdly, the method did not located all problematic NiS stones, possibly due to lack of concentration by the person examining the windows as a result of tedium and uncomfortable environment.
It is an object of the present invention to provide an improved method and apparatus for detecting defects in window glass.
SUMMARY OF THE INVENTION
In one broad form, the present invention provides a method of detecting defects in window glass, comprising the steps of
photographing portions of the window glass onto photographic film in controlled lighting conditions,
optically magnifying the photographic film images, and
optically examining the magnified images to detect inclusions and/or other defects.
In the method of this invention, only the “photographing” step need be conducted on site. Once the window glass has been photographed, the film images can be examined subsequently in more comfortable surroundings. The film images can therefore be examined more easily, and more accurately.
Further, since the photographic film images are magnified for examination, the observer has the advantage of magnification in detecting defects in glass (as compared with direct visual observation of the glass as described in our earlier patent application).
Preferably, the photographing step is performed using a camera mounted on a frame which is releasably fixed to the building containing the window glass being examined. The frame may be suitably fixed to the window mullions. The camera frame is located in the building maintenance unit (BMU), but is fixed relative to the window during photography.
Several cameras may be carried on a single frame, to maximise photographic coverage of the window glass.
During photography, the window glass is illuminated by a light source carried on the BMU which also carries the operator.
In order that the invention may be more fully understood and put into practice, a preferred embodiment thereof will now be described with reference to the accompanying drawings.
REFERENCES:
patent: 4076426 (1978-02-01), Gross et al.
patent: 4160601 (1979-07-01), Frosch
patent: 5073707 (1991-12-01), Marcin
patent: 5841530 (1998-11-01), Hewitt et al.
patent: 0 282 687 (1988-09-01), None
patent: 08304048 (1996-11-01), None
patent: WO 94/08229 (1994-04-01), None
Akin Gump Strauss Hauer & Feld L.L.P.
Johns Andrew W.
Nakhjavan Shervin
The University of Queensland
LandOfFree
Detection of defects in glass does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Detection of defects in glass, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Detection of defects in glass will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2515243