Optical waveguides – Miscellaneous
Reexamination Certificate
1999-03-03
2001-10-16
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
Miscellaneous
C385S115000, C349S002000, C250S227150
Reexamination Certificate
active
06304713
ABSTRACT:
BACKGROUND OF THE INVENTION
This application is based on Japanese Patent Application No. 10-53482, filed Mar. 5, 1998, the content of which is cited herein by reference.
The present invention relates to an optical fiber seal verifying system used to probate an optical fiber seal.
In nuclear facilities, to comply with the NTP safeguards agreement based on the NTP (Nuclear Nonproliferation Treaty), many seals are used for the purpose of checking whether nuclear substances are illicitly taken out from storage facilities or casks. Judging whether seals have been tampered with is called “verification”.
There are seals of various types, and currently, E type metal cap seals are widely used. However, as the first problem, the E type metal cap seals must be detached for verification to check the presence/absence of abnormalities. As the second problem, one to two weeks are required for verification.
To solve these problems, an optical fiber seal (also called a COBRA seal) has been developed by Sandia National Laboratories in USA.
The optical pattern of optical fiber transmission light on the seal end face is photographed in sealing and verification, and the two photographs are visually compared, thereby verifying an optical fiber seal.
By comparing the optical pattern photographed in sealing with the optical pattern photographed in verification, the presence/absence of seal break is determined. To do this, the optical patterns are recorded by photographing them, and the optical pattern in sealing and that in verification are visually compared and collated.
In this method, however, the load on the person who performs verification is heavy. In addition, the determination result cannot be quantified and contains the subjective point of view of the inspector.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide an optical fiber seal verifying system capable of obtaining a determination result quantified at the verifying site.
According to the first aspect of the present invention, there is provided an optical fiber seal verifying system comprising an optical pattern generation unit for reading an optical pattern of an optical fiber seal in sealing and verification and generating first and second optical pattern data corresponding to the sealing and verification, respectively, a seal number input unit for inputting a unique seal number for identifying the optical fiber seal, a memory unit for recording the optical pattern data generated by the optical pattern generation unit together with the seal number input by the seal number input unit, a processor unit for reading the first optical pattern data recorded in the memory unit in verifying the optical fiber seal and the second optical pattern data recorded in the memory unit in sealing the optical fiber seal corresponding to the seal number on the basis of the seal number recorded in the memory unit and comparing the optical pattern data with each other to calculate a concordance ratio and a display unit for displaying a calculation result from the processor unit.
According to this arrangement, the optical pattern of an optical fiber seal is recorded in sealing. In verification, an optical pattern read from an optical fiber seal to be probated is compared to the optical pattern recorded in sealing to obtain the concordance ratio, thereby verifying the optical fiber seal.
As the inspector need not compare photographs for verification, the operation load on the inspector is largely reduced. Additionally, the verifying result is not influenced by the subjective point of view of the inspector.
According to the second aspect of the present invention, there is provided an optical fiber seal verifying system similar to the system according to the first aspect, which further comprises a portable case and a power supply unit. The power supply unit is accommodated in the portable case, along with the optical pattern generation unit, seal number input unit, memory unit, processor unit and display unit.
According to this arrangement, not only the effect obtained by the system of the first aspect of the present invention but also the following effect can be obtained.
Since the optical fiber seal verifying system of the present invention is portable, a verifying result can be obtained at the verifying site.
According to the third aspect of the present invention, the optical pattern generation unit of the second aspect comprises a holder for holding the optical fiber seal in which two end portions of an optical fiber bundle are fixed, a light-emitting device for sending light from one end face of the optical fiber bundle, and an image pickup device for picking up optical patterns of the optical fiber seal held by the holder and the seal number carved near an end portion of the optical fiber seal.
With this arrangement, the end face image of the optical fiber seal can be appropriately picked up.
According to the fourth aspect of the present invention, the holder of the third aspect comprises an insertion portion for receiving the optical fiber seal, a fixing spring for fixing the optical fiber seal inserted into the insertion portion, and a limit switch for detecting that the optical fiber seal is inserted to a position that allows picking up images.
With this arrangement, the end face image of the optical fiber seal can be properly picked up, and any end faces' images can be picked up under the same condition.
According to the fifth aspect of the present invention, the optical pattern generation unit of the first aspect comprises an analog/digital converter for converting the optical patterns picked up by the image pick up device into multivalued digital data, and an image memory unit for storing the digital data converted by the analog/digital converter.
With this arrangement, optical pattern processing can be easily performed by the processor unit.
According to the sixth aspect of the present invention, a processor unit identical to the one according to the fourth aspect calculates the number of luminous points and luminance distribution in two optical patterns of an optical fiber, which are represented by digital data generated by the analog/digital converter. The first optical pattern is one the fiber has while probated, and the second optical pattern is one the fiber has while being sealed. From the number of luminous points and luminance distribution, the processor unit determines the positions which the two optical pattern should take to have the greatest number of luminous points in common, and calculates a ratio of the number of luminous points which each pattern has in common with the to the other pattern to the number of other luminous points which the pattern has.
With this arrangement, matching between the optical patterns in verification and sealing can be quantitatively evaluated.
According to the seventh aspect of the present invention, the processor unit of the sixth aspect calculates the concordance ratio by
S
/(
N
1
+
N
2
−
S
)
where N
1
is the number of luminous points of a first optical pattern of the optical fiber seal in sealing, N
2
is the number of luminous points of a second optical pattern of the optical fiber seal in verification, and S is the number of luminous points at which the first and second optical patterns match.
With this arrangement, matching between the optical patterns in verification and sealing can be quantitatively evaluated.
According to the eighth aspect of the present invention, when the concordance ratio is equal to or higher than a predetermined value, the processor unit of the seventh aspect determines that the optical fiber seals are identical, and when the concordance ratio is lower than the predetermined value, the processor unit determines that the optical fiber seals are different, or the optical fiber seal has been broken.
With this arrangement, verification determination standards in the optical fiber seal verifying operation can be unified.
According to the ninth aspect of the present invention, the optical pattern generation unit of the fifth aspec
Isogai Takeshi
Wakahara Michio
Yamamoto Youichi
Cooper & Dunham LLP
Mitsubishi Heavy Industries Ltd.
Palmer Phan T. H.
White John P.
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