Leak detector for sealed optical devices

Details Leak detector for sealed optical devices Leak detector for sealed optical devices

2001-03-05

2004-02-24

Alexander, Lyle A. (Department: 1743)

Chemistry: analytical and immunological testing

Process or composition for determination of physical state...

Leak detection

C436S001000, C436S164000, C116S004000, C073S040700, C073S040000

Reexamination Certificate

active

06696296

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to apparatuses and method for leak detection. More particularly, this invention relates to apparatuses and methods for leakage detection for sealed optical devices.
BACKGROUND OF THE INVENTION
Manufacturers of fiber optical components are often encountered with the difficult tasks of assuring that optical components, commonly very small in size, are completely sealed with no leakage such that the optical components are able operate under humid, dusty and harsh environment with long term reliability. In order to assure that the optical components are produced without leakage, leak tests of the optical components under high temperature and high humidity test chamber for long period of times over several thousand hours are typically performed. Optical performance parameters are then measured after the optical components are placed in a accelerated burn-in test in order to screen the defective devices with cycling under a high humidity condition over a burn-in testing period. These methods have several drawbacks. First of all, the test methods are time consuming and labor-intensive thus cause the production cost to increase significantly. Furthermore, these conventional test methods may not produce reliable test results for detecting the leaks. Depending on the size and position of the leak, changes in performance parameters of an optical component may or may not related to a leakage after the tests carried out in a test chamber. There are multiple reasons that could cause the changes in optical parameters. The tests and measurements provide no direct indications for detecting a leak. Additionally, the severe test conditions may be destructive to the optical components. The damages caused by the leakage tests may be unnecessary and could have been avoided if the leakage of the optical components can be detected by a less severe but more direct and sensitive testing method.
For these reasons, a need still exists in the art of optical component design, manufacture and testing to provide a new and improved component configuration and testing method s to conveniently detect the leakage of the optical component such that the difficulties and limitations can be resolved.
SUMMARY OF THE PRESENT INVENTION
It is therefore an object of the present invention to provide an improved method of manufacturing and testing the optical components such that a leak on an optical component can be more directly and conveniently detected to overcome the above mentioned difficulties and limitations encountered in the conventional test techniques.
Specifically, it is an object of the present invention to provide an improved method of component manufacturing and testing for the sealed fiber optical components by injecting a target gas with no optical interference effects into the sealed optical components. The sealed optical components are then placed in a leak detection chamber for measuring a variation of the amount of the target gas in the test chamber. A leak test is carried out by elevating the temperature in the test chamber thus causing the target gas in the optical components to expand and expelled from the sealed components if there is a leak. A simple and direct measurement is now provided for detecting a leak without testing the optical components for measuring performance parameters through many indirect and often unnecessary duty cycles of temperature cycling under high humidity pressure or other kinds of testing conditions.
Another object of the present invention is to provide a simple, direct and convenient method for manufacturing and testing fiber optical components to simplify the leak detection processes such that cost savings in component productions can be achieved and meanwhile component reliability can be improved.
Briefly, in a preferred embodiment, the present invention discloses a method for detecting a leak from a sealed optical device. The method includes the steps of a) injecting a target gas with no performance interference to the sealed optical device for leak detection followed by sealing the sealed optical device as usual. B) Placing the sealed device in a leak testing chamber and measuring a background level of the target gas in the leak-testing chamber. C) Heating the sealed device to a gas-expelling temperature for expelling the target gas from the leak in the sealed optical device. And D) detecting the target gas with a detection sensitivity in a one-part-per million (PPM) range in the leak-detecting chamber for comparing with the background level of the target gas for determining the leak in the sealed optical device. In a preferred embodiment, the target gas injected into the optical component may be a target gas of carbon dioxide or other non-hazardous gases. In another preferred embodiment, the step of heating the seated device is a step of heating the optical device to a temperature approximately between eighty to one hundred degrees Celsius.
In summary, this invention also discloses a sealed device that includes a sealed inner space containing a target gas useful for leakage detection. In a preferred embodiment, the sealed inner space containing a higher than a normal atmospheric content of the target gas. In a preferred embodiment, the sealed device is a sealed optical device. In another preferred embodiment, the sealed inner space of the sealed optical device containing a target gas of carbon dioxide or other non-hazardous gases.
These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various drawing figures.


REFERENCES:
patent: 3729983 (1973-05-01), Coppens
patent: 3987664 (1976-10-01), Hass et al.

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