Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1999-12-15
2003-05-20
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C356S073100, C356S238100
Reexamination Certificate
active
06566644
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates in general to the field of electro-optics and, more particularly, to an optical fiber sorter system and method.
BACKGROUND OF THE INVENTION
There are numerous methods and systems for detecting radiation. In one type of detector, photocathodes are used in conjunction with microchannel plates (MCPs) to detect low levels of electromagnetic radiation. Photocathodes emit electrons in response to exposure to photons. The electrons may then be accelerated by electrostatic fields toward a microchannel plate. A microchannel plate is typically manufactured from lead glass fibers and has a multitude of channels, each one operable to produce cascades of secondary electrons in response to incident electrons. A receiving device then receives the secondary electrons and sends out a signal responsive to the electrons. Since the number of electrons emitted from the microchannel plate is much larger than the number of incident electrons, the signal produced by the device is stronger than it would have been without the microchannel plate.
One example of the use of a photocathode with a microchannel plate is an image intensifier tube. The image intensifier tube is used in night vision devices to amplify low light levels so that the user can see even in very dark conditions. In the image intensifier tube, a photocathode produces electrons in response to photons from an image. The electrons are then accelerated to the microchannel plate, which produces secondary emission electrons in response. The secondary emission electrons are received at a phosphor screen or, alternatively, a charge coupled device (CCD), thus producing a representation of the original image.
Another example of a device that uses a photocathode with a microchannel plate is a scintillation counter used to detect particles. High-energy particles pass through a scintillating material, thereby generating photons. Depending on the type of material used and the energy of the particles, these photons can be small in number. A photocathode in conjunction with a microchannel plate can be used to amplify the photon signal in similar fashion to an image intensifier tube. The detector can thus be used to detect faint particle signals and to transmit a signal to a device, e.g., a counter, that records the particle's presence.
Microchannel plates are generally fabricated by heating a rod of core glass material surrounded by a sleeve of cladding glass material in a glass drawing furnace. The glass is drawn for fusing the core glass to the surrounding glass sleeve to produce a glass clad glass fiber of relatively small cross section. The glass fiber is then cut into smaller length portions and the portions assembled into a bundle. The bundle is then repeatedly heated, drawn and cut to produce glass clad glass fibers of relatively small hexagonal cross section. Hexagonal fibers having substantially equal cross section are then assembled into a second bundle. The second bundle is assembled within a pressing fixture, heated to the softening point, and pressed together to fuse the individual fibers together and to a surrounding sleeve. The composite fused bundle is then sliced transversely to form multiple plates which are etched to remove the core glass leaving a microchannel plate.
However, prior systems and methods for fabricating microchannel plates suffer several disadvantages. For example, fabricating the microchannel plate generally requires cross-sectionally measuring each hexagonal fiber to ensure that fibers having substantially equal cross section are bundled together to minimize gaps between the bundled fibers and maximize the quantity of channels in the microchannel plate. However, cross sectionally measuring each fiber is generally tedious and time consuming. Additionally, measurement variations along the length of the fiber may generally require calculating an average cross sectional measurement for the fiber prior to bundling the fiber with other fibers.
SUMMARY OF THE INVENTION
Accordingly, a need has arisen for a better technique having greater flexibility and control for fabricating a microchannel plate. In accordance with the present invention, an optical fiber sorter system and method are provided that substantially eliminates or reduces disadvantages and problems associated with previously developed systems and methods.
According to one embodiment of the present invention, an optical fiber sorter system includes a measurement system operable to determine a measurement characteristic of an optical fiber. The sorter system also includes a guide system operable to direct the optical fiber to a measurement position of the measurement system. The sorter system also includes a collection system disposed adjacent an outlet of the guide system. The collection system includes a plurality of receivers for receiving the optical fibers from the guide system. The sorter system further includes a controller operable to automatically position a particular receiver of the collection system adjacent the outlet of the guide system corresponding to the measurement characteristic of the optical fiber.
According to another embodiment of the present invention, a method for automatically sorting optical fibers includes guiding an optical fiber toward a measurement position of a measurement system using a guide system. The method also includes automatically determining a measurement characteristic of the optical fiber as the optical fiber passes through the measurement position of the measurement system. The method further includes automatically positioning one of a plurality of receivers of a collection system adjacent an output of the guide system to receive the optical fiber corresponding to the measurement characteristic of the optical fiber using a controller.
The technical advantages of the present invention include a system and method for automatically measuring and sorting optical fibers that substantially increases the uniformity of devices made with the sorted optical fibers, such as a microchannel plate. For example, according to one aspect of the present invention, optical fibers are transported through a guide system to a measurement system. The measurement system automatically determines measurement characteristic data of the optical fiber as the optical fibers travels through the guide system. The measurement characteristic data is transmitted to a controller. The controller automatically positions a collection system adjacent an outlet of the guide system to receive the optical fiber. The collection system may include a plurality of receivers each designated for receiving optical fibers having particular measurement characteristic values.
Another technical advantage of the present invention includes greater measurement characteristic data collection than prior systems and methods. For example, according to another aspect of the present invention, a feed system may be disposed adjacent the guide system to transport the optical fibers through the measurement position of the measurement system at a substantially constant rate and at a substantially fixed position relative to the measurement system, thereby providing increased control of the optical fiber during measurement characteristic data collection.
Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions, and claims.
REFERENCES:
patent: 3757942 (1973-09-01), Gunn
patent: 5139150 (1992-08-01), Fuller, Jr. et al.
patent: 5995212 (1999-11-01), Dar et al.
Pruet James D.
Wilson Kerry A.
Le Que T.
Litton Systems Inc.
Luu Thanh X.
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