Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/01—Manufacture of glass fibres or filaments
  • C03B37/012—Manufacture of preforms for drawing fibres or filaments
  • C03B37/01205—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments
  • C03B37/01211—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube
  • C03B37/01214—Manufacture of preforms for drawing fibres or filaments starting from tubes, rods, fibres or filaments by inserting one or more rods or tubes into a tube for making preforms of multifibres, fibre bundles other than multiple core preforms
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B23/00—Re-forming shaped glass
  • C03B23/20—Uniting glass pieces by fusing without substantial reshaping
  • C03B23/207—Uniting glass rods, glass tubes, or hollow glassware
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/005—Diaphragms
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/04—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres
  • G02B6/06—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings formed by bundles of fibres the relative position of the fibres being the same at both ends, e.g. for transporting images
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2203/00—Fibre product details, e.g. structure, shape
  • C03B2203/10—Internal structure or shape details
  • C03B2203/22—Radial profile of refractive index, composition or softening point
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2203/00—Fibre product details, e.g. structure, shape
  • C03B2203/40—Multifibres or fibre bundles, e.g. for making image fibres
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/0001—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings specially adapted for lighting devices or systems
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S359/00—Optical: systems and elements
  • Y10S359/90—Methods

Definitions

• a complex off-axi3 filter can be designed and constructed which is composed of layers of glass formulations having differing indices of refraction in a gradient which leads away off-axis light rays. Such devices suffer from distortion and breakage due to the differing coefficients of thermal expansion which generally accompany differing indices of refraction.
• Another solution would be to provide a peripheral jacket or cladding of light absorbing material with an index of refraction equal to that of the core of the filter.
• the problem is that the index of refraction is dependent on the frequency of radiation or light and the variation is not the same for different glass compositions. It is impractical to match indices for clear glass and black or absorbing glass over the frequency spectrum to avoid internal reflection.
• Another object of the invention is to provide a contrast enhancing component for a low level radiation imaging device.
• a further object of the invention is to provide a contrast enhancing aperture for a low level radiation imaging device which allows long term exposure of the detector to radiation from the target without interference from stray radiation.
• Another object of the present invention is to provide an off-axis radiation filter having substantially the same coefficient of thermal expansion throughout.
• a still further object of the invention is to provide an off-axis radiation filter which is effective for broad bands of frequencies of electromagnetic radiation.
• Another object of the invention is to provide an off-axis filter having no expensive and fallible electronic or electromechanical parts.
• Another object of the present invention is to provide a contrast enhancing component for a low level radiation imaging device which is simple in construction, inexpensive to manufacture, and capable of long life of useful service with minimum maintenance.
• the invention consists of an optical conduit having a well-defined axis, and provided with a radiation absorbing means at a peripheral surface, the surface being parallel to the axis.
• the conduit is adapted to collect radiation impinging on an optical device or detector and to selectively filter out, by absorption at its axial periphery, radiation that propagates in a direction oblique to the axis.
• a transparent glass core is provided with an axis adapted to be aligned with the line of sight of the detecting or imaging device.
• a cladding layer is provided at a periphery of the core, the cladding essentially formed of a glass composition having the same index of refraction and coefficient of thermal expansion as the core glass, thereby forming, with the core, a non-reflecting, non-refracting interface.
• a small percentage of the cladding is composed of "black" or absorbing glass in the form of fibers or leaves extending from random locations on the core in a direction generally normal to the interface of core and cladding.
• the absorbing elements have a higher index of refraction than the remainder of the cladding material to promote refraction of the light into the absorbing elements rather than
• the invention also involves a method of forming a cylindrical embodiment of the conduit by the steps of: forming a flat sheet of glass containing random parallel fibers or leaves of absorbing glass, cutting the sheets into several strips, assembling the strips into a cylindrical configuration with the absorbing elements extending generally radially of the axis and the cylinder , inserting a core having the same formulation of glass as the main component of the sheet, and fusing the assembly and core together.
• FIG. 1 is a schematic view of a filter embodying the present invention in conjunction with a light detecting device
• FIG. 2 is a perspective view of an embodiment of the filter in circular cylindrical form
• FIG. 3 is a cross-section taken on the line III-III of FIG. 2,
• FIG. 4 is a cross section taken on the line IV-IV of FIG. 2,
• FIG. 5 is a detail of the filter in the area labeled V of FIG. 3 showing the effect of the filter on off-axis and parallel light rays, respectively,
• FIGS . 6 and 7 show an end view of a bundle of fibers of clear and absorbing glass before and after the fusing of the bundle into a block
• FIG. 8 shows a plate of glass cut from a block with parallel absorbing fibers randomly distributed therein
• FIG. 9 shows one mode of cutting the plate in strips to form an octagonal cylinder as shown in FIG. 10,
• FIG. 11 illustrates a cross section of the article formed by a modified process.
• an off-axis filter is associated with a detecting or imaging device 11.
• the imaging device 11 Under conditions of low light level or low radiation level, the imaging device 11 will be provided with means of intensifying the radiation which reaches it.
• image intensifying means are well known, and can be activated by very low levels of light and other radiation. If a light ray model is assumed for the propagation of radiation, it can be seen that a ray 13 parallel to the line of sight A-A from the source 12 to the device 11 is transmitted through the filter 10 without diminuation.
• the filter is formed as a cylinder having a core 20 of material
• OMPI transparent to a desired band of radiation, in this case visible or near-visible light.
• the core is surrounded at its radial periphery by a jacket or cladding 21.
• the main volume of this cladding is composed of a formulation of glass having the same index of refraction as the core, so that the interface 22 between core and cladding is non-reflecting and non-refracting.
• the cladding 21 is provided with a plurality of light absorbing fibers extending generally radially of the axis A-A (which is indicated in FIG. 4 by the numeral 25).
• the fibers are thus generally normal to the interface between the core and the cladding.
• the fibers are optimally formed of material having a high index of refraction relative to the material forming the core and the remainder of the cladding.
• FIG. 5 indicates the effect of the filter on, respectively, a quantity of light propagating parallel to the axis of the filter, and a quantity of light entering the filter on an oblique angle to the axis.
• a quantity of light 26 propagating parallel to the axis passes through the transparent core unhindered, with relatively constant intensity, and arrives at the detector 11 to activate it.
• the interface 22 between the core glass and the cladding glass of the same composition does not involve a difference in index or refraction
• the quantity of non-axial light 27 passes through the interface without reflection and is trapped among the absorbing fibers 23. At its first interaction with the fibers, the ray is partly absorbed and partly
• the fraction of the light which is absorbed with each encounter is a function of the index of refraction of the fiber and is preferably enhanced by using fibers with a relatively high index.
• off-axis light which is not filtered out immediatly by a sufficiently long filter incorporating the present invention, is light which reflects off the ends of the black fibers at the interface between core and cladding. It has been found that a relatively small ratio of absorbing fiber volume to cladding volume suffices to absorb off-axis light as described. For example, incorporation of about three percent absorbing fibers by volume satisfactorily absorbs oblique rays. This results in approximately three percent area-to-area ratio between the absorbing fiber ends and the interface 22.
• the effective amount of off-axis light that is transmitted by reflection from the fiber ends is further decreased; first of all, by absorption at the fiber end, and secondly, by the likelihood that such a beam will be absorbed by its second or a subsequent encounter with the interface of core and cladding.
• An added advangtage of minimizing the volume-to-volume ratio of fibers and cladding is that the problems which would be associated with differential thermal expansion and contraction are likewise minimized, even with fibers whose composition is very ill-matched with the glass of the core and the cladding.
• OMPI There are a number of ways to form an off-axis filter as described.
• a practical embodiment may be formed as described below.
• the resulting bundle is then fused into a continuous mass as FIG.. 7 shows.
• the resulting block of glass may be cut into plates by well-known methods. Such a plate is shown in FIG. 8. For some applications, the plate may simply be fused to a flat piece of core glass of the same composition as the clear fibers in the original bundle.
• the radial pattern which is ideal for a cylindrical conduit may be aproximated by sectioning a plate such as that shown in FIG. 8.
• the plate may be periodically cut into strips at an angle, alpha *, the angle chosen so that the strips may be assembled into a regular polygonal right cylindrical tube.
• the angle alpha is chosen to be 45°
• the resulting strips may be assembled into the octagonal cylindrical tube shown in FIG. 10.
• An appropriately shaped core may be inserted in this step, or preferably, the central opening 33 may be bored out into a circular cylindrical shape and a cylinder of core glass closely inserted. The entire assembly may then be fused to form an integral radiation conduit which absorbs off-axis radiation.
• An alternative embodiment of the device may be formed by the following modified steps.
• the continuous mass or block 32 shown in FIG. 7 may be cut into slabs parallel to the absorbing fibers. From these slabs, right cylindrical tubes may be cut and transparent cores inserted as above. Such a modification presents a cross-section as shown in FIG. 11.
• Another approach involves serial layering of clear and black glass to form a cylinder having planar alternate and randomly spaced layers of clear and black glass perpendicular to the axis of the cylinder. A central bore is formed along the axis and filled with clear glass to form the conduit.

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• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Optics & Photonics (AREA)
• General Physics & Mathematics (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
• Optical Couplings Of Light Guides (AREA)
• Manufacture, Treatment Of Glass Fibers (AREA)
• Light Guides In General And Applications Therefor (AREA)
• Optical Elements Other Than Lenses (AREA)

Priority Applications (2)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23977800

Family Applications (1)

Country Status (7)

Cited By (3)

Families Citing this family (8)

Citations (8)

Family Cites Families (11)

• 1983
  • 1983-05-24 US US06/497,665 patent/US4533210A/en not_active Expired - Fee Related
• 1984
  • 1984-04-26 IL IL71651A patent/IL71651A/xx unknown
  • 1984-05-11 DE DE8484902735T patent/DE3473935D1/de not_active Expired
  • 1984-05-11 WO PCT/US1984/000734 patent/WO1984004821A1/en not_active Ceased
  • 1984-05-11 EP EP84902735A patent/EP0148919B1/en not_active Expired
  • 1984-05-11 AU AU31506/84A patent/AU3150684A/en not_active Abandoned
  • 1984-05-11 JP JP59502689A patent/JPS60501428A/ja active Granted

Patent Citations (8)

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