US3784817A

US3784817A - Radio luminescent sighting arrangement

Info

Publication number: US3784817A
Application number: US00142190A
Authority: US
Inventors: R Whittaker; D James; S Smiley
Original assignee: Atlantic Richfield Co
Current assignee: Atlantic Richfield Co
Priority date: 1971-05-11
Filing date: 1971-05-11
Publication date: 1974-01-08
Anticipated expiration: 1991-01-08

Abstract

An illuminating arrangement is disclosed which, in one particular embodiment, includes a pair of optically-alignable ''''sight markings'''', the markings being illuminated and defined, at least in part, by a ''''radio-luminescent'''' segment, especially suited for a dimly-lit field of view, these segments including a phosphorescent material and a ''''matched'''' radio-isotope adapted to induce prescribed phosphorescence.

Description

UnitedStates Patent 1191 James: Dean B. et al. 1 Jan. 8, 1974 [54] RADIO LUMINESCENT SIGHTING 2,488,541 11/1949 Holme 250/71 R ARRANGEMENT 1,423,184 7/1922 Butler 250/71 R 1,534,937 4/1925 Foley 250/77 [75] Inventors: Dean B- Ja s, Be y r 2,113,973 4/1938 Addink 250/71 R H. Smiley, Pittsburgh; Ralph E.

l ll g gg Jr Upper St C a Primary Examiner-Archie R. Borchelt Attorney-John R. Eubank and John C. Martin, Jr. [73] Assignee: Atlantic Richfield Company, Glenolden, Pa.

22 Filed: May 11, 1971 [571 ABSTRACT [21] Appl. No.: 142,190 An illuminating arrangement is disclosed which, in

one particular embodiment, includes a pair of optically-alignable sight markings", the markings being illuminated and def-med atvleast in part by a [58] d R 77 78 luminescent segment, especially suited for a dimly-lit e 0 field of view, these segments including a phosphorescent material and a matched" radio-isotope adapted [56] ggifi gf to induce prescribed phosphorescence. 3,578,973 5/ 1971v Dooley et al 250/71 R 4 Claims, 6 Drawing Figures PATENTEUJAH 8 m4 SHEEI 10F 3 FIGURE I FIGURE 5 FIGURE 4 PAIENIEUm 8 m4 3. 784.81 7

sum

2 or 3 FIGURE 3 Pmminm 8mm 3.784.817

saw an: a

FIGURE 5 RADIO LUMINESCENT SIGHTING ARRANGEMENT BACKGROUND OF THE INVENTION When using a sighting arrangement, (such as the sights on a rifle, pistol or other weapon) under conditions of low-level (poor) ilumination, an operator (e.g., a rifleman) often is unable to perceive the sight markings and is thus hampered in the use of the device. For instance, when a rifleman is aiming his weapon in the half-light of near-dusk or moonlight, he may be able to dimly perceive his target but will often have difficulty identifying the markings or critical edges of the rifle sights. The brightness of the illumination should be just sufficient to provide adequate definition. If it is too bright, the operator will be blinded; or, at least, his ability to perceive the dimly-lit target will be impaired.

Various arrangements have been considered to illuminate such sighting devices; for instance, a (miniaturized) battery-powered lamp has been suggested, preferably in combination with light-conducting fibers (light-pipes) so as to remotely-locate the lamp and completely shield it, the fibers conducting the light from the lamp to illuminate the eyepiece markings. Such arrangements may use a miniaturized lampbattery combination, together with a small variable resistance for adjusting the current to the lamp, and resultant brightness e.g., permitting a rifleman to illuminate his sights sufficiently to aim his weapon but not so bright as to interfere with his vision, nor to generate glare about the sight markings, or, especially, not such as to signal his presence to the enemy. The minimal brightness that is required will vary with the darkness of the surroundings. This battery-powered, lamp-fiber arrangement has not proved very satisfactory, partly because the batteries and lamps involved are not sufficiently reliable. This is particularly so for military field applications, where extremes of temperature, moisture, shock and vibration etc. are encountered; e.g., in the use of an Army rifle in jungle warfare. Such an arrangement is also undesirably bulky and inconvenient to mount on the typical weapon. The use of a single spot of radio-luminescent material at the center of a circular, transparent reticle has been considered as a means of illuminating the rear sight of a rifle. This appears to present some difficulties, partly because a halo of light floods the reticle, obstructing vision and also because the radio-luminescent spot is white in color; furthermore, without illumination of the foreward sight, it is difficult to properly align the weapon.

SUMMARY OF THE INVENTION The present invention contemplates using radioluminescent segments, preferably comprising red phosphors, to mark and define (at least a portion of) the sight markings (or critical edges) in such sighting devices. These radio-luminescent markings will provide adequate and variable (red) illumination of the sight markings, without interfering with the convenient use of the weapon. By using a red phosphor, the illumination can be brighter, providing better definition to the markings or critical edges, without blinding the operator or being visible to the target.

It will be evident that a primary object of the subject invention is to solve at least some of the foregoing problems and provide at least some of the foregoing features and advantages. A related object is to provide optical sighting devices with radio-luminescent segments defining at least a portion of the sight markings.

A further object is to provide such radio-luminescent segments using particular isotopic materials which are sufficiently active to provide for adequate stimulation of the phosphorescent material, but which emit a minimal amount of penetrating radiation that does not constitute a health hazard to the operator.

A related object is to provide such radio-luminescent segments using particular phosphorescent materials such as zinc sulfides, yttrium (europium) vanadates, gadolinium(europium) oxides, or like red phosphors in order to provide maximum illumination of the sight markings or critical edges without impairing the vision of the operator or permitting the weapon to be located by the intended prey.

A further related object is to use such red phosphor materials in combination with Promethium-l47 (isotope) so as to properly activate the phosphor and provide prescribed illumination with a minimum of penetrating, exterior, ionizing radiation and with an adequate brightness half-life associated with the illumination to provide for satisfactory operation over a period of several years.

Other objects are to miniaturize sight-illuminating arrangements, to eliminate problems associated with portable battery lamps, light fibers, and other devices, and to optimize the use of radio-luminescent materials so that the aforedescribed problems are avoided.

How the foregoing and other more specific objects are achieved will appear and become evident through consideration of the ensuing description of preferred embodiments of the invention in conjunction with the associated drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a highly schematic isometric view of an embodiment of the invention, with parts omitted or indicated only functionally for clarity.

FIG. 2 is a schematic isometric view of a rear sight embodiment like that in FIG. 1 but modified somewhat.

FIG. 3 is a schematic isometric view of a front sight embodiment like that in FIG. 1 but modified somewhat.

FIG. 4 is a rather simplified isometric view of a single radio-luminescent marking segment modified and indicated asrotatable about its own axis to make the emanating illumination variable in quality and/or intensity.

FIG. 5 is an upper perspective view of a radioluminescent tube embodiment suitable for use in the arrangements of FIGS. 1 to 4.

FIG. 6 is a very schematic isometric view of other embodiments illustrating means for selectively varying illumination quality and intensity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a suitable application environment for a preferred embodiment of the invention to be described. Here, an optical sighting arrangement OSA is shown, comprising from and rear sights, 30 and 20, re-

spectively, that are shown mounted, through associated

brackets

35 and 25, respectively, upon a common support indicated in phantom as support B which, for purposes of illustration, may be understood as including the frame portion of a rifle or like weapon supporting the optical sighting device, being used by an operator for aiming the weapon in a manner understood in the art. Accordingly, sights 20 and 30 (being functionally shown) may be understood as aligned along a common optical (sighting) axis SA, shown in phantom extending from the working end or origin (operators eye) of the sighting device along, and through, the sighting arrangement to terminate at a selected target locus T. The sighting arrangement is adapted, conventionally, to enable an operator to aim the piece so as to hit a prescribed target zone (here indicated as the center of target T). Axis SA thus defines the center of the field of view associated with the sighting arrangement, terminating at the center of illustrative target T.

Front sight 30 comprises a cylindrical radioluminescent tube 33 mounted in alignment with, and concentric along, axis SA upon a suitable arm 31 which, in turn is attached to fixed bracket 35. Rear sight 20 comprises a planar opaque supporting plate 21 of any suitable shape and dimension as dictated by established sight design and accommodated upon the supporting weapon. Plate 21 includes a relieved sighting-aperture portion 22. Aperture 22 preferably comprises a generally circular cut-out of a radius which defines a prescribed field of view that will surround the target (taking into account the relative location of origin O and other dimensions as is conventional in the art). The center 20-C of aperture 22, lies along axis SA and forms the focus or origin from which the upper edges of plate 21 and the pair of elongate

radioluminescent tubes

23 and 24, mounted therealong, all extend. Preferably, these upper sighting-edges (critical edges) are bevelled along a pair of symmetrical axes originating at focus 20-C. Sight 20 is rigidly affixed on bracket 25 which, in turn, is affixed upon

support B. Brackets

25, 35 may of course (either or both) be adjustably affixed to support B so as to permit the repositioning and adjusted alignment of the associated sights, as is well known in the art. Moreover, the general mechanical arrangements of the foregoing sighting device (including the general configuration of sight 20) are generally known in the art.

Radio-

luminescent tubes

23, 24, and 33 may be understood as, all, generally fashioned in the manner indicated in FIG. as tube 1 and are hereinafter described in some detail, although modified embodiments will also serve. Radio-luminescent tube 1 comprises an outer casing 3 enclosing and housing an inner slug 5 of radio-luminescent material. Tube 3 preferably comprises a closed cylinder. Radio-luminescent tube 1 can also be constructed by suspending the fine-powder mixture of radio-luminescent material in a monomer (or un-solidified form of any transparent plastic material) and then fixing the radio-luminescent material within the solidified transparent plastic material by casting it in the desired cylindrical shape. This cylindrical shape may also be achieved by extruding a rod of plastic material, containing the suspended radio-luminescent material, as the plastic solidifies. Then single tubes would be sectioned from the extruded rod. It may be desirable to coat the impregnated tubes" with a thin layer of plastic material that does not contain radioluminescent material in order to provide a surface from which radioactive powder cannot be released by abrasion or wear.

In the case of

embodiments

23, 24, the tube is partially shielded with an opaque material so as to provide one or more translucent window sections along at least a portion of the side walls so as to generate linesegments of illumination along the tube length at selected circumferential locations thereof. Such a line of illumination can also be achieved as in the case of

tubes

23 and 24 by embedding all but a portion of the side of the tube into the sight frame. Tube 3 is about one-quarter to one-half inches long, as required, providing the necessary length of linear definition, with an inner diameter of one-sixteenth to one-thirty-second inches and with a wall thickness as may be required to provide adequate strength and integrity to the tube.

In the case of end-illuminated embodiment 33, the tube is as afore-described except, of course, that one end (only) is translucent while the other end and the sides are opaque to shield it optically directing illumination only back along axis SA toward origin 0. In the case of 33, the entire tube 1 can be embedded in a metal holder, etc., exposing only the tube end to provide an illuminated dot along sighting axis SA. Also, in the case of tube 33, the tube could be embedded vertically in a vertical post-type sight (replacing 30), exposing only the curved end of the tube 1 to provide an illuminated shaft along sighting axis SA.

The radio-luminescent materials comprising slug 5 may take a number of forms, all receiving an energizing isotope plus a luminescent material responsive thereto. We prefer to use phosphors of the zinc sulfide type, that emit illumination in the red region of the visible spectrum. We have found this particularly suitable for night, or other low-illumination, situations, the red illumination being less blinding to a darkness-adapted eye than other regions of the visible spectrum or white light of the same brightness. Other phosphors such as those based upon rare-earth compounds, such as yttrium(europium) vandate, yttrium(europium) oxysulfide, or gadolinium (europium) oxide may be used in certain situations instead of, or in combination with, the zinc sulfide type.

Various radio-isotopes may be used as the activating energy source. Generally, the penetrating nature of gamma radiation and its associated health-physics problems make gamma emitting isotopes unacceptable. Alpha-emitting isotopes may be used, but the energyconversion efficiency can be quite low due to short mean-free path. Beta emitting isotopes are generally preferred. We have considered tritium, promethium (Pm-147), krypton (Kr-85), and strontium (Sr-90) primarily. Kr-85 and Sr-90, however, have the disadvantage of emitting considerable penetrating gamma radiation in addition to their beta activity, and thus present a health hazard. The beta energy of tritium is only 1/ 10 that of Pm-l47 and accordingly much more must be rounding the operator is brighter (but still insufficient to permit him to define his sights without the aid of illumination), the sight illumination must be brighter to provide adequate definition. If, however, the environment is quite dark, (but still sufficient to illuminate the target), it may be necessary to reduce the sight illumination from that required for the brighter environment to a lower level of sight illumination that will not interfere with the ability of the operator to perceive him dimly-lit target.

Thus, a radio-luminescent tube 1 (analogous to

tubes

23, 24, etc.) as indicated in FIG. 4 may be enclosed (to intercept useful illumination) by rotatable filter CF adapted to provide selectable levels of emanating brightness on the linear sight markings. Filter CF is adapted to be rotated relative to tube 1' selectably interposing optical filters of varied opacity between the radio-luminescent phosphor source and the illuminated marking across the given field of view (angular field Fo V indicated). A radio-luminescent tube 1' may be understood as constructed generally along the lines of tube 1 in FIG. 5, comprising radio-luminescent slug 5' surrounded by transparent encapsulation tube 3 (or as comprising radio-luminescent material suspended in transparent solid plastic), which in turn is surrounded by filter CF (at least across field Fo V). Filter CF is provided with various strip portions or segments S1, S2, S3, etc. of selected, different opacities as known in the art and is made rotatable with respect to the enclosed radio-luminescent tube. Thus, for instance, when a given angular sector of the tube is exposed across the field FoV (e.g. as defined by the mask provided by plate 21' in FIGS. 2A, 28) then a prescribed, selected light-attenuating strip 8-3 of prescribed opacity will be interposed to set the level of illumination as selected by the operator. For a different illumination, the filter CF may be shifted (by mechanical means known in the art but not shown) to interpose another filter strip of dif ferent corresponding opacity. The adjustable linear illumination may also be provided by coating the tube with segments of a transparent material of varying opacity in each segment and then providing for the entire coated tube to be rotated, exposing the each segment to the unshielded portion of the mounting.

The means for mounting the luminescent tube and its surrounding filter so as to be rotatable with respect thereto in a given gunsight configuration will be apparent to those skilled in the art and will not be dwelt upon here. Filter CF may, for instance, comprise an arcuate segment of film spanning the length of the luminescent tube, with the strips of varying opacity each being long enough to cover the exposed window (field Fo V) involved in the subject mounting arrangement.

A further modification for varying the emanating intensity is shown (very functionally) in FIG. 6 where an exemplary radio-luminescent tube 10 (understood as along the lines of those described before and adapted to emit light of a given original intensity from its exposed head portion not shown but generally indicated as light rays P focused at marking spot (CH). Tube 10 is adapted to project radiant energy at a given original intensity to be focused (by optics not shown, but well understood in the art) onto a prescribed spot CH portion of a sighting screen or reticle F. Spot Cl-I will, for instance be the functional analog of the spot of light projected by the end of tube 33 in the embodiment of FIG. 1 and adapted to define the center of the sighting axis SA in the given sighting arrangement. Also shown is an intensity adjusting filter means F comprising a generally-circular disc having (quadrant) sections FS-l, FS-2, etc. of different selectable opacities, filter F being rotatable as indicated (e.g., by the operator) to interpose one of the sections FS between radioluminescent source 10 and the operators eye and thereby allow a selectable adjustment of the intensity of the light projected as spot CI-I. One may use a like arrangement employing a filter belt. Thus, it will be apparent that where the embodiment involves a sighting spot CH on the gunsight of a rifle used in low illumination situations (night fighting) for a target T the rifleman/operator may rotate filter F to provide a sighting spot CH of an intensity selected to most closely suit the level of target illumination at a particular time. Obviously, filter F may include virtually any number of selectable filter sections having different opacities andlor filtering characteristics (e.g., color) and may take the form of other analogous devices for selectably attenuating the level of illumination projected from the radio-luminescent source.

Those skilled in the involved art will readily understand that the subject invention may take other analogous forms still falling within the spirit and scope of the subject invention as defined by the appended claims for instance, involving variations in structure, materials, or processes used. For instance, radio-luminescent devices of the type described may obviously be used in defining the markings of other sighting or like arrangements while in certain cases, other phosphors and/or other radio-isotope materials may in certain instances be apt for achieving the indicated results and performing at least some of the described unique functions.

What is claimed is:

1. In a sighting arrangement including sight marking means and supporting means, the arrangement being adapted to enable an operator to position the supporting means so as to align the marking means along a prescribed sighting axis, extending between a point of origin and a target point, this arrangement including an elongate chamber arranged along a portion of the axis wherein at least one reference point along the axis is to be indicated by one or more marking segments, the improvement therein comprising:

. at least one illumination arrangement comprising a translucent housing containing radio-luminescent means adapted to project an illumination beam to delineate at least one of said marking segments, said radio-luminescent means comprising a matrix of clear plastic material in which are relatively homogeneously suspended particles of a phosphorescent material emitting light in the visible red spectrum, and particles of Promethium-l47 isotope 2. The combination recited in claim 1 wherein said phosphorescent material comprises a zinc sulfide type phosphor.

3. The combination as recited in claim 1 wherein the sighting arrangement comprises a gunsight for a weapon.

4. An optical marking device for defining an alignment pattern under low-illumination conditions comprising at least one radio-luminescent capsule, this capsule comprising container means, luminescent means comprising a matrix of clear plastic material in which are relatively homogeneously suspended particles of 5; sorbed within ceramic microspheres, such as the synthetic zeolites, and the rinsed, loaded spheres then fired to fix Pm O inside, with surface activity thereafter being removed with an acid leach. Of course, in

using Pm-l47 it should be b orne in mind that lightin tensity wiT cayio liapproximately of the initial b is tness u about five years i 9 1 4 7 13 @2- year half-life.

Accordingly, with our preferred embodiment, indisated abov Pm-147 ist 12. use binsdw a red-phosphorescent material. Preferably, a zinc-sulfide phosphor and the Pin-147 microspheres are mixed together, the sizes of both particles typically ranging from to 50 microns.

Using the foregoing mixture of promethiumimpregnated ceramic microspheres and zinc sulfide phosphor particles we have found the following relat on be w n Put-14 on o an re u tant brightness, as measured in microlamberts to be illustrative of what may be expected:

TABLE I Pm-l47 Concentration Brightness" (mCi) (UL) milli-curics of Promethium I47 brightness in microlamberts as compared to a white, certified standard phosphorescent light source brightness ola red zinc sulfide phosphorescent system in an 6-inch glass tube, tG-inch long; all other values are for white zinc sulfide systems as circular flat spots, 3/32-inch in diameter.

Of course, brightness can be varied from a few microlamberts (about the intensity of a watch dial) up to a few millilamberts for the white system (the intensity of the typical television receivers cathode ray tube is on the order of several hundred millilamberts; similarly for typical military instrument dials, pushbuttons, etc.). We prefer to keep the brightness of the red system to the order of 199 250 microlamberts, as measured with a photometer that has been calibrated with a similar zsz tk wn bri htne s s n a niqs. P-. 47. "l mspheres and a white phosphor.

As a modification of the foregoing radio-luminescent composition, a red rare-earth phosphor may be impregnated in the microspheres along with the P n-147 to ac liie ve ahigh er conversion efficiency. In most cases, the Pm-l47/red-phosphor mixture embedded in tiny ti'ansparent tubes which are, in turnfaffixed as marking segments" on the sight will be the preferred embodiment because of their desirable performance in low-illumination situations. For certain instances, one

can prepare an isotope-phosphor mixture of the type described in conjunction with a paint vehicle and simply spread it as a painted marking on the surface or critical edge of the sight. However, this will obviously expose the radio-luminescent mixture to risks of weathering and associated deterioration, accidental abrasion and removal, etc. Thus, the encapsulation of the mixture sealed within a tiny transparent glass (or plastic, etc.) tube or suspended in a solid transparent plastic tube of the type described, exposing only the end or side of the tube to describe the desired configuration segment (i.e., the illuminated dot or line) avoids this problem.

The dimensions of the tube 1 (length, inside and outside diameters, etc.) may, of course, be adjusted as required by the specific configuration of the sight to be illuminated. In general, the front-sight will be adapted to provide a spot source mark (or glowing dot) by exposing only the end of a single radio-luminescent tube. The rear-sight will typically require one or more linear radio-luminescent segments (light sources; e.g., provided in the embodiment by exposing the side of tube 1) arranged to form a Vee", a U, a square, or similar geometries, within which the front spot is to be positioned (aligned with) during a typical sighting routine.

FIGS. 2 and 3 illustrate rear and front rifle sights, 20, 30 respectively along the lines of the embodiment in FIG. 1 but slightly modified and, of course, shown in somewhat greater detail and in enlarged scale. Thus, rear sight 20' is generally the same as sight 20 in FIG. 1 (except where indicated) and includes a cut-out (aperture) 22' in an opaque plate 21' with a pair of opposed, similar radio-luminescent-tube-receiving slots 24-8, 23-8 flanking aperture 22, each slot being aligned along (parallel to) the upper edges of sight 20, these edges being bevelled to comprise a V configuration, the arms of which originate from associated optical axis SA (as in the embodiment of FIG. 1). Plate 21' may assume any convenient dimensions (e.g., on the order of a few eighths of an inch square by a few sixteenths in thickness, with the radius of slots 24-8, 23-8 and cut-out 22' being a few sixty-fourths).

Front sight 30 is also generally the same as sight 30 in the embodiment of FIG. 1 except where specified, and includes a holder 31' (our mounting device) including a hole 33-8 for receiving the associated radioluminescent-tube. Mount 31 will be assumed as formed of metal, opaque plastic or the like and adapted to mask out any stray light from the glowing radioluminescent tube in hole 33-8, except for the light-spot projected back along optical axis SA toward rearsight 20 (as with the embodiment of FIG. 1). Holder 31' will be suitably dimensioned (e.g., cross-sectional dimensions of several thirty-seconds inch with a radius being cut-out across its base to provide for its being mounted on the barrel of the weapon.

INTENSITY ADJUST According to a further improvement and feature of novelty, the radio-luminescent tubes may be made adjustable in brightness (intensity of illumination). For example, this allows an operator to adjust brightness of the illuminated segment markings of his sighting device to suit the lighting conditions of his environment and relative to the brightness of the target T within his field of view at a particular time. If the environment surof said container means being sufficiently translucent to emit the requisite luminescence to define the said pattern appropriately for the conditions prevailing at the time of regulating the shielding, whereby durable utility for the marking device is attainable not merely throughout a variety of illumination conditions but also after significant decay of the radioisotope.

Claims

1. In a sighting arrangement including sight marking means and supporting means, the arrangement being adapted to enable an operator to position the supporting means so as to align the marking means along a prescribed sighting axis, extending between a point of origin and a target point, this arrangement including an elongate chamber arranged along a portion of the axis wherein at least one reference point along the axis is to be indicated by one or more marking segments, the improvement therein comprising: at least one illumination arrangement comprising a translucent housing containing radio-luminescent means adapted to project an illumination beam to delineate at least one of said marking segments, said radio-luminescent means comprising a matrix of clear plastic material in which are relatively homogeneously suspended particles of a phosphorescent material emitting light in the visIble red spectrum, and particles of Promethium-147 isotope material as an activating radio-isotope material.

2. The combination recited in claim 1 wherein said phosphorescent material comprises a zinc sulfide type phosphor.

4. An optical marking device for defining an ''''alignment pattern'''' under low-illumination conditions comprising at least one radio-luminescent capsule, this capsule comprising container means, luminescent means comprising a matrix of clear plastic material in which are relatively homogeneously suspended particles of phosphorescent material and particles of Promethium-147 sealed within said container means to provide initially a surplus amount of luminescence emitting light rich in the visible red spectrum and instantly regulatable shielding means for masking out a portion of said luminescence to define said pattern, at least a portion of said container means being sufficiently translucent to emit the requisite luminescence to define the said pattern appropriately for the conditions prevailing at the time of regulating the shielding, whereby durable utility for the marking device is attainable not merely throughout a variety of illumination conditions but also after significant decay of the radioisotope.