Arrangement of a sighting mark and a light-producing source of energy therefor

The invention relates to an arrangement of a sighting mark and a light-producing source of energy therefor in an optical sighting instrument, especially a telescopic sighting tube. The invention is characterized in that at least one light-emitting capsule, preferably at least one .beta.-ray transmissive capsule enclosing a .beta.-ray producing substance, is mounted in the telescopic sighting tube at a point on a circle which is centered on the longitudinal axis of the sighting instrument and disposed at an axial distance of between about 0 and 2 r counted from a plane perpendicular to the axis and passing through the center of the sighting mark, the distance to the center not exceeding 2 r, where r is the radius from the center to the periphery of the light opening in the sighting tube at the level of the plane. The capsule, whether it is mounted spaced from or in the plane, is positioned and directed to send at least a substantial proportion of the radiation from the capsule onto the sighting mark to make the latter luminous.

The present invention relates to an arrangement of a sighting mark, such as 
cross hairs or the like, and a light-producing source of energy to make 
the sighting mark luminous. 
In conventional optical sighting instruments of the telescopic sighting 
tube type, the sighting mark usually is in the form of so-called cross 
hairs. It is, however, difficult to distinguish the thin lines forming the 
cross hairs against the background during and after twilight, and 
therefore such sighting marks are no help at all for night shooting. 
In contrast to conventional telescopic sights, so-called luminous spot 
sights are provided with an arrangement for generating a luminous spot, 
i.e. a luminous sighting mark, and this known arrangement usually 
comprises a small electric battery, a light-emitting diode, and a 
translucent spherical mirror. If the mirror lies in the marksman's field 
of vision, which it usually does, the light intensity of the luminous spot 
sight, i.e. the admission of light through the sight from the target to 
the marksman's eye, is deteriorated to some extent. Using this known 
arrangement of luminous spot sights in connection with telescopic sights 
is difficult. So far, the arrangement has not been successfully applied to 
telescopic sights, in spite of the fact that the cross hairs of telescopic 
sights--however great the light-transmitting capacity of these sights may 
be--frequently cannot perceived by the marksman under certain light 
conditions, such as darkness and dusk, although the actual target area may 
be well visible. 
It is the object of this invention to overcome the above-mentioned problems 
by providing, for use in connection with sighting instruments of different 
types and especially for telescopic sighting tubes, an arrangement that 
enables the marksman, with a minimum of trouble, to perceive the sighting 
mark even in complete darkness. 
To this end, the invention provides an arrangement of a sighting mark and a 
light-producing source of energy therefor in a sighting instrument, 
especially a telescopic sighting tube, in order to make the sighting mark 
luminous. The arrangement is characterized in that at least one 
light-producing source of energy, especially a .beta.-ray transmissive 
capsule enclosing a .beta.-ray producing substance, is mounted in the 
telescopic sighting tube at a point on a circle centered on the 
longitudinal axis of the sighting instrument and disposed at an axial 
distance of between about 0 and 2 r from a plane perpendicular to said 
axis and passing through the center of the sighting mark, where r is the 
radius from the center to the periphery of the light opening in the 
sighting tube at the level of said plane, and in that means are provided 
to direct radiation from said capsule to the sighting mark. 
In a preferred embodiment according to the invention, use is made of 
.beta.-ray producing capsules disposed at a distance not exceeding 1 r 
from the plane of the sighting mark and most preferably 0 r, which means 
that each capsule is incorporated in the plane. In this case, the sighting 
mark is formed on or incorporated in a disc of optical material, and by 
mounting each capsule on the peripheral edge of the disc or incorporating 
the capsule in the material proper, the material will serve as a light 
transmitter leading directly to the sighting mark. Such an embodiment will 
eliminate all of the problems described above and, furthermore, will 
eliminate the need for disconnection of the source of energy when a 
sighting instrument equipped with the arrangement according to the 
invention is not being used. In this manner, the marksman avoids the 
problem of a complete discharge of a battery simply because he forgot to 
disconnect the battery after use of the sighting instrument. 
However, the light-producing device may, of course, be a light-emitting 
diode and an electric miniature battery of the same type as is being used 
for luminous spot sights, but in this instance the present invention 
eliminates the use of a semispherical mirror for producing the sighting 
mark, and although the arrangement in this instance also may require a 
microswitch for disconnecting the battery, the power supply from the 
battery may lie at such a low value that a complete battery discharge will 
take so long that neglecting to disconnect the battery will make no 
difference, unless the discharge is allowed to continue over a period of 
months. 
With the arrangement according to the invention, accurate sharpshooting can 
be carried out under all dusk and darkness conditions during which the 
target area is at all perceivable, and furthermore the arrangement 
according to the invention makes it possible to take aim in complete 
darkness at targets which are not visible but may be perceived in some 
other manner, for instance by hearing. 
It should be mentioned in particular that the arrangement according to the 
invention is eminently suitable for activities such as still-hunting fox 
from ambush on a moonless night, which has hitherto not been possible for 
this popular hunting form.

FIG. 1 shows a circular lens or disc 1 of glass or like optical material, 
said disc incorporating a sighting mark having the form of a cross, 
so-called cross hairs, 2 which may be scored in the disc material, and 
four light-producing sources of energy 3. The light-producing sources 3 
preferably are incorporated in said disc, as shown. Each source 3 may 
consist of a small glass capsule containing a .beta.-radiation active 
substance and constructed to convert the energy of the .beta.-particles 
into light. Miniature radiation sources of this type are available on the 
market, usually under the designation "beta-light". 
The .beta.-ray emitting substance may be radioactive tritium gas, and for 
effective transformation of a substantial part of the energy into light 
for making the sighting mark luminous, the .beta.-particles have to be 
decelerated before arriving at the sighting mark proper. Therefore, the 
distance through which the energy is transmitted from the emitting source 
to the sighting mark, such as through the glass disc, is important, as 
will be explained below. 
The glass disc 1 may consist of two thin glued-together glass discs with 
recesses for the light-producing capsules 3 and with the cross hairs 2 
scored into either one of the two abutting surfaces. Alternatively, the 
capsules 3 may be incorporated in the glass disc by molding. 
A reflector 4 in the form of a thin rail of U-shaped cross-section is 
mounted on the periphery of the glass disc, said reflector reflecting 
light towards the interior of the glass disc. The glass disc transmits the 
light, and the walls of the cross hairs shown will then appear in the form 
of thin luminous lines of essentially the same fineness as the scored 
lines constituting the cross hairs. The embodiment as disclosed in FIGS. 1 
and 2 is thus characterized by one or more very small so-called 
beta-lights which are disposed within or at least recessed into the glass 
disc near the periphery thereof and which, by inner reflection from the 
planar surfaces of the glass disc and from the polished outer edge of said 
disc, possibly amplified by means of a reflector 4, render the sighting 
mark, such as aimed cross hairs, luminous. 
It should be noted that the sighting marks, such as cross hairs, are shown 
on an exaggerated scale in FIG. 1 and the following Figures for 
illustrative purposes only. 
In the embodiment according to FIGS. 3 and 4, the light-producing source 
consists of a tube 3a curved to circular shape and having a small 
cross-sectional area. The tube encloses a glass disc 1a which may be in 
the form of a glass body having a greater axial length than the disc 1 in 
FIGS. 1 and 2. Like the capsules 3 in FIGS. 1 and 2, the tube 3a contains 
a radioactive substance emitting .beta.-particles. The tube 3a is 
surrounded by a reflector 4a which may have semicircular cross-sectional 
shape and which tightly encloses the tube 3a. 
In the embodiment according to FIGS. 5 and 6, the light is generated by a 
light-emitting diode 3b tightly secured to the peripheral edge of the 
glass disc 1b, and connected to electric wires 5 and a small battery (not 
shown). The light transmitted through the glass disc 1b is internally 
reflected by the planar sides of the disc and the peripheral surface of 
the disc and will appear as luminous lines in the cross hair scores 2b. 
FIGS. 7 and 8 illustrate a variant of the embodiment according to FIGS. 5 
and 6, and in this variant the sighting mark is not in the form of cross 
hairs, but in the form of a small dot 2c which is rendered luminous in the 
same manner as the cross hairs described above. The dot 2c may consist of 
a very small cavity in the center of the glass disc 1c, but the dot-shaped 
sighting mark may also be produced by reflection from a small prism 6 
which is formed for example by providing the glass disc on one side with a 
small recess of triangular or other shape. 
The glass disc shown in FIG. 9 has a sighting mark in the form of cross 
hairs 2d which, in the embodiment illustrated, are augmented by a 
dot-shaped central sighting mark I. The glass disc 1d has, in parallel 
with the central line of the cross hairs, a number of horizontal lines 
designated II-V in FIG. 9 and spaced from the horizontal line of the cross 
hairs and from one another by distances corresponding to different 
distances to a target, for example the distance 100 meters for the central 
line of the cross hairs, 150 meters for the line II, 200 meters for the 
line III, etc. In addition, these horizontal lines are provided with a 
number of dots on either side of the vertical line of the cross hairs, 
such as the dots X, XI, XII. These dots may be used as sighting dots if 
the firearm, upon use of the dot I or the dots lying on the vertical line 
of the cross hairs, should prove to be aimed incorrectly in the lateral 
direction. 
All of these lines and dots in FIG. 9 can be made luminous by means of a 
light-producing device of the type mentioned above or described below. 
FIGS. 10 and 11 illustrate an arrangement according to the invention in 
which the glass disc 1e is provided with cross hairs 2e and a channel 3e 
near the periphery of the disc 1e. The cross hairs 2e and the channel 3e 
may be formed in one or both sides of two glass discs which are then glued 
together to form communicating channels. These channels are filled with, 
for example, radioactive gas, such as tritium gas, rendering the channels 
luminous. 
FIGS. 12 and 13 illustrate a variant of the embodiment according to FIGS. 
10 and 11, and in this embodiment the glass disc 1f is surrounded by a 
circularly curved tubular glass capsule 3f containing radioactive tritium 
gas or some other suitable light-producing substance. 
In the two embodiments as last described, the channels 2e, 3e and the tube 
3f, respectively, may be provided with a gas-filling device 7. 
The embodiments described above merely serve to illustrate the invention, 
and many modifications may occur. The sighting mark may be of different 
shape, such as dot-shaped, cross-shaped, etc. and can be provided in some 
other manner than by scoring. In order to produce a luminous sighting 
mark, the light can be received and transformed into visible light, for 
example on the walls defining scored lines or recesses or, according to 
FIGS. 10 and 11, by means of gas-filled luminous channels. It should be 
noted, however, that a sighting mark in the form of cross hairs, for 
example, can be produced by means of thin wires glued together between two 
glass discs-for example, in the embodiment according to FIGS. 5 and 6. 
Thus, light-reflecting wires may have the same function as 
light-reflecting scored lines. 
The thick glass body 1a illustrated in FIG. 4 may be advantageous in that 
it changes the angles from the light-producing source towards the scored 
lines of the cross hairs so that these can be illuminated to a greater or 
lesser extent also in the axial direction in order to be more intensely 
reflect by the side walls of the scored lines. 
The invention also makes it possible to use numbered luminous scales, as in 
the embodiment shown in FIG. 9, for the lines II, III etc. and for the 
dots X, XI etc. Use may also be made of an LC technique, in which case a 
current source may be used for activation. 
For embodiments similar to the one shown in FIGS. 12 and 13, use may be 
made of a glass capsule 3f which on its inner side, or a part thereof, has 
a fluorescent coating activated by radioactive tritium gas. 
FIG. 14 shows a preferred modification wherein the sighting mark is again 
in the form of so-called cross hairs 2f, but in this modification the 
cross hairs are freely suspended in the hollow center of an annular 
support 11 by being fixed at their four outer ends to the support 11 
which, in turn, is fixed to the inner side of a tubular member 12 of a 
telescopic sighting tube 10. An array of beta-lights of the kind described 
above (for example, four beta-lights as in FIG. 1) are fixed in angularly 
spaced relationship on the inner side of an annular support 4g designed to 
serve as a reflector. The annular reflector 4g is fixed to or formed as a 
part of the tubular member 12, and unlike the reflector 4 shown in FIG. 1, 
the reflector 4g supports the array of beta-lights 3g, which are coaxial 
in relation to but axially spaced from the cross hairs support 11 and the 
sighting mark 2f. In the embodiment shown in FIG. 1, the radial distance 
from the capsules 3 to the center of the sighting mark 2 is approximately 
1r, where r is the radius of the free light-passage through the annular 
reflector 4. Thus, the light from the capsules must travel a distance 
which will approximately amount to 1r to reach the center of the sighting 
mark. Experiments have shown that for most optical materials used in the 
sighting arrangement (e.g., glass) the energy emitted from a so-called 
beta-light capsule of the standard type available on the market (and of a 
volume suitable to be incorporated peripherally in relation to a sighting 
mark of the cross hairs type in a telescopic sighting tube of normal 
dimensions for use on a firearm), will be efficiently transformed into 
visible light on or in the sighting mark to make the mark luminous, 
provided that the travelling distance through the material amounts to at 
least the distance 1r mentioned above. In several cases, r is also 
equivalent to the radius of a normal sighting mark the form of cross hairs 
of the type shown in, for example, in FIGS. 1 and 14. 
In the embodiment shown in FIGS. 3 and 4, the ray path in the optical 
material 1a is elongated in that scored lines 2a which form the cross 
hairs, are cut into the glass body or lens 1a at an axial distance from 
the plane of the lens where the latter is encircled by the tubular member 
3a which contains the .beta.-ray producing substance. Thus, the path for 
transforming energy into visible light from the source of energy to the 
center of the cross hairs in FIG. 4 is about r/sine 45.degree., which is 
about 1.4r. Experiments have shown that if this value is exceeded too far 
there is a risk that a damping effect, which will counteract the desired 
energy transforming effect, will dominate when the material in question is 
glass or some other optical material. In a gas, such as air, the distance 
from the energy producing source, such as the beta-capsule 3g in FIG. 14, 
i.e. the ray path, may be somewhat longer. However, the current theory is 
that the optimal distance lies between about 0 and 2r counted from a plane 
perpendicular to the axis of the instrument 10 or tube 12 through the 
center of the sighting mark, e.g. the sighting mark 2f in FIG. 14, and 
between about 1r and 2r counted from the periphery of the light passage 
opening through the tube 12, i.e. the supporting ring 11, to said center. 
As has been mentioned above, r is the normal radius of the light opening 
in the instrument in the plane wherein the sighting mark is disposed, i.e. 
in the case of FIG. 14 the opening through the supporting ring 11 and in 
the case of FIG. 1 the lens 1 encircled by the reflector 4. 
As will appear from the above description, the light from the light source 
is, in the preferred embodiment, substantially or completely transmitted 
within a body of optical material, usually glass, and is subjected to 
inner reflection against the sides and edges of the glass body with 
insignificant radiation loss. In this manner, and because the light 
intensity and energy can be held at very low levels, the light will 
interfere with the marksman's eye to an insignificant extent only, and the 
source of energy will have a long life. However, in another preferred 
embodiment, shown in FIG. 14, the transmission path may extend through a 
gas, such as air, and may be slightly longer within the preferred limits 
mentioned above, to make the sighting mark luminous, and in this latter 
case it is preferred to use a sighting mark of thin plastic strips or thin 
metal wires provided with a highly light-reflective surface.