Optics: measuring and testing – Inspection of flaws or impurities – Transparent or translucent material
Reexamination Certificate
1998-03-16
2001-05-01
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
Inspection of flaws or impurities
Transparent or translucent material
C356S427000, C250S22300B, C382S142000
Reexamination Certificate
active
06226081
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to the field of measurement of the fill level of the contents of containers at least part of which is transparent, and more particular to optical means by which the height of fill can be measured in such containers, for example glass or plastic bottles, whether of clear or colored glass or other material. The term “transparent” is used herein to mean capable of transmitting electromagnetic radiation at an adopted working wavelength band, not necessarily within just the visible region. For example, certain embodiments of the invention use infra-red radiation, and can thus be used with glasses which are transparent in the infra-red though not in the visible.
Although the invention may be used for other purposes, for example measuring the height-of-fill (HOF) of pulverulent (e.g., powder) materials in glass ampoules, it is primarily intended to address the problem of measuring the HOF of the fluid contents of transparent beverage containers, such as soda or beer bottles, to determine if they meet specifications for their volumetric content, which directly correlates to HOF for a known bottle geometry. While a bottle could possibly be stationary it is typically moving at appreciable speed while conveyed along a production line, so it is measured while moving, but at sampling rates that are sufficiently fast so that the bottle appears “stopped” to the measuring optical system. Preferred embodiments of the invention have been tailored to meet the needs of bottled beers in clear, green and brown glass containers. As will be seen, the system preferably utilizes a line scan CCD imager to provide high-speed image capture.
Height of Fill is traditionally measured using an x-ray beam that is set to 3 mm below the calibrated liquid level. When the beam signal changes, the fill is within limits, and produces a yes
o only answer to a Host control system, usually in the form of a computer of other suitable microprocessor based system.
Optical systems for measuring HOF are also known. For example, U.S. Pat. No. 3,232,429 (Norwich) describes a fill level detector for use in checking the HOF of bottles of foamable liquid passing along a filling line. The presence of a bottle at a measuring station is detected by a mechanical switch, and two beams from light sources are passed through the upper end of the bottle on to two photodetectors. Depending upon the output from the photodetectors, the bottle is classified as acceptably filled, underfilled, or empty, and the latter two categories of bottle are removed from the filling line by a mechanical rejection device. Since this apparatus uses only two spaced photodetectors, only one of which detects the presence of liquid contents lying beneath the foam in the bottle, it gives only a yes
o answer as to whether the bottle is sufficiently filled and cannot measure the actual HOF. Furthermore, since the HOF detection is made from fixed apparatus lying alongside the filling line, the process cannot compensate for vertical variations in the position of the bottle such as tend to occur when bottles are being transported by a flexible conveyor.
U.S. Pat. No. 5,414,778 (Schwartz et al.) describes an apparatus for measuring HOF of a carbonated or similar fluid which is in a “dynamic state” immediately after filling of a bottle. The somewhat elaborate process described in this patent requires line-by-line analysis of a two dimensional image of a part of the bottle, above and below the fill line produced by a video camera; this analysis serves to identity not only the HOF but also the number and size of bubbles within the liquid. To carry out such an image analysis on bottles on a commercial filling line, which may be filling 1200 bottles per minute, requires a high powered computer, and an expensive apparatus. Furthermore, the process described in this patent does not attempt to allow for the presence of foam above the liquid, despite the fact that such foam is inevitably present when many liquids, for example beer, are filled on high speed filling lines.
The present invention provides a process and apparatus for determining the HOF of a container; this process does not require the elaborate analysis and computing power required by the Schwartz et al. process, but can measure the HOF and allow for the presence of foam above the liquid. Preferred embodiments of the present invention can compensate for variations in the vertical height of the container, such as those which occur when the container is being transported by a flexible conveyor.
SUMMARY OF THE INVENTION
Accordingly, this invention provides a first process for determining the height-of-fill of a container comprising a body having an optically detectable feature, and contents filling the body up to a fill level, at least a measuring portion of the container extending from the optically detectable feature to the fill level being capable of transmitting electromagnetic radiation. This process comprises: illuminating at least the measuring portion of the container with electromagnetic radiation; forming an image of part of the measuring portion of the container; and analyzing the image by data processing means to identify:
(a) a first region having a first intensity that varies in accordance with the optically detectable feature; and
(b) a second region having a second intensity associated with the contents below the fill level and which varies in accordance with the optical properties of the contents,
and determining the distance between a point within the first region and the upper edge of the second region, thereby determining the height-of-fill.
This invention also provides a first apparatus for carrying out this first process and thus for determining the height-of-fill of a container comprising a body having an optically detectable feature, and contents filling the body up to a fill level, at least a measuring portion of the container extending from the optically detectable feature to the fill level being capable of transmitting electromagnetic radiation. This apparatus comprises: image-forming means arranged to form an image of part of the measuring portion of the container; and data processing means for analyzing this image, the data processing means being programmed to identify in the image:
(a) a first region having a first intensity that varies in accordance with the optically detectable feature; and
(b) a second region having a second intensity, associated with the contents below the fill level, and which varies in accordance with the optical properties of the contents
and to determine the distance between a point within the first region and the upper edge of the second region, thereby determining the height-of-fill of the container.
This first process and apparatus may hereinafter for convenience be called the “optical feature” process and apparatus of the present invention.
This invention also provides a second process for determining the height-of-fill of a container comprising a body, foamable liquid contents filling the body up to a fill level, and foam resting upon the liquid contents and extending from the fill level up to a foam level, at least an upper portion of the container extending from below the fill level to the foam level being capable of transmitting electromagnetic radiation. This process comprises: illuminating at least the upper portion of the container with electromagnetic radiation; forming an image of part of the upper portion of the container; and analyzing the image by data processing means to identify:
(a) a first region having a first intensity the varies in accordance with the optical properties of the foam; and
(b) a second region having a second intensity that varies in accordance with the optical properties of the liquid contents,
and determining the position of the boundary between the first and second regions, thereby determining the height-of-fill.
Finally, this invention provides a second apparatus for carrying out this second process and thus for determining the height-of-fill of a container com
Anthony Brian W.
Fantone Stephen D.
Sevigny Kevin M.
Wilk Stephen R.
Caufield Francis J.
Optikos Corporation
Pham Hoa Q.
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