Gun sight

A gun sight comprises a block of transparent material having a line of sight therethrough between a target end and a viewing end. A graticule pattern is mounted to the, in use, top surface of the sight whereby it may be illuminated by light from the sky generally above the sight. The block has a first internally reflecting surface disposed below the graticule pattern and aligned to reflect light therefrom to a second reflecting surface, which in turn is aligned to reflect light from the graticule to a partially reflective doublet lens system in the line of sight. The partially reflective doublet pattern reflects said doubly reflected light to form a virtual image of the graticule at infinity in the line of sight.

The present invention relates to a gun sight. More particularly, it relates 
to a collimator gun sight of the type in which a target is viewed along an 
axis of the sight and the image of a graticule pattern is reflected within 
the sight to lie also on this axis. 
Collimator gun sights of the above type are well known from, e.g. British 
patents nos. 2049118 and 2056634. One disadvantage with these gun sights 
is that the optics are arranged so that the graticule aiming pattern is 
illuminated by ambient light from the area adjacent to the target. This 
has hitherto been thought advantageous since the illumination level of the 
graticule patter varies automatically with the ambient light level in the 
region of the target. However, where the target is located e.g. beneath a 
tree or the like, the level of illumination for the graticule pattern is 
reduced. This is clearly disadvantageous. 
It is an object of the present invention to provide a gun sight which 
overcomes the above disadvantage and allows an increased amount of light 
to illuminate the graticule aiming pattern. 
According to the present invention there is provided a gun sight of the 
type in which a target is viewed along an axis of the sight and the image 
of a graticule pattern is reflected within the sight to lie also on said 
axis, in which the graticule pattern is mounted to the, in use, top 
surface of the sight whereby it may be illuminated by light from the sky 
generally above the sight. 
Preferably the sight has an additional reflecting surface below the 
graticule pattern whereby the remaining optics of the sight may be 
substantially conventional. 
The graticule pattern may be a transmissive graticule, optionally a 
transmissive film graticule. 
The graticule is advantageously rectangular in overall shape to increase 
the aperture and give improved illumination.

Referring now to the drawings, the sight is formed of an optically 
transparent material such as a suitable glass. It comprises a number of 
parts cemented together to form a block which, after assembly, is painted 
with black epoxy paint, except for entry and exit faces and a graticule 
illumination face. 
Light from the target enters at face 1, while the user looks through face 
2. Faces 1 and 2 are parallel one to the other and normal to a line of 
sight through the sight. Thus, light from the target passes through the 
gun sight without deviation. 
A graticule 3, shown in more detail in FIG. 1, is disposed on the top 
surface (in use) of the sight close to the entry face. The graticule 3 is 
a transmissive film graticule and may be illuminated by means of light 
from the sky above the gun sight. An image of the graticule is reflected 
firstly by angled lower face 4 of sight main block 5. Face 4 is firstly 
aluminised before being painted so as to make it reflective, and is angled 
at 45.degree. to the lower surface of the block 5 so that the image of the 
graticule is reflected to rear surface 6 which is similarly aluminised 
before painting. The surface 6 is angled at approximately 96.6.degree. 
with respect to the base of block 5 so that the image of the graticule is 
reflected therefrom to a concave partially reflecting surface 7. Surface 7 
is formed within a doublet pair of lenses having a transmission of between 
20 and 25%. The image is then reflected by the concave partially 
reflecting surface to the viewing face 2. 
When the graticule is located at a distance, after reflections, from the 
concave surface which substantially equals or approximates the focal 
length of the concave partially reflective surface, the image of the 
graticule seen by the user appears to be substantially at or near 
infinity. 
As can be seen, the graticule is rectangular and therefore the horizontal 
aperture is increased. Furthermore, since the graticule faces upwardly, it 
is illuminated by light from above and therefore the level of illumination 
is increased, since light from above is usually brighter than that from 
the target area. This means that the graticule pattern may be picked up 
more readily by users of the sight. 
As can be seen from FIG. 2, main block 5 has its end faces at an angle so 
that reflecting face 6 may reflect the graticule image to concave 
partially reflective surface 7, which is also angled with respect to block 
5 so that the resultant image appears in the line of sight. In order to 
ensure that the target image passes directly through the sight, faces 1 
and 2 are formed on patch plates 8 and 9 respectively, to give parallel 
ends normal to the line of sight. 
The sight described above may be made shorter than conventional sights of 
this type, since the graticule image is reflected off two plane faces and 
the concave surface as opposed to the hitherto known single reflective 
surface and the concave surface. Since the sight is shorter, it finds 
particular utility with pistols, although other uses may be easily 
envisaged. 
The sight is designed to take graticule illumination from the sky and 
thereby improve graticule recognition by the user. However, of course, for 
use at night, some form of illumination must be provided. For example, a 
betalight of possibly 800 microlamberts may be used. In the connection, 
the position of the graticule 3 makes use of such illumination devices 
easier.