GB2220081A - Periscope apparatus - Google Patents

Abstract

A gunsight comprises a periscope including a main prism 10, an eyepiece prism 11 and an intermediate portion 12 therebetween arranged to give an elongate field of view through a viewing aperture about 120 mm wide by 50 mm high at the eyepiece; and a reference device including a graticule prism 13 joined to one end of the main prism 10, a beam splitter 14 at the end of the portion 12 adjacent to the eyepiece prism 11, and a lens device 15 between a beam splitter feed prism 16 and a graticule 17 on the prism 13. The eyepiece prism 11 and its associated housing, are pivotally carried by a support arranged to counter rotate the eyepiece about axis 20 as the portion 12 is swung about a mounting axis (22), Fig 2 (not shown), to vary the elevation of periscope. <IMAGE>

Description

A PERISCOPIC SIGHT This invention concerns periscopic apparatus such as periscopes and periscopic sights, e.g. gunsights for armoured fighting vehicles (AFV's).

Such apparatus may be of simple, e.g. non-magnifying form, or of more complex, e.g. magnifying, form, but all such forms generally comprise an objective portion, including an objective reflector (and optionally an objective lens or lenses) and an eyepiece portion including an eyepiece reflector (and optionally an eyepiece lens or lenses), which said portions are joined together by an intermediate portion which provides an internal light transmissive path (and optionally an additional lens, lenses and/or, in the case of a panoramic sight, a dove prism).

However, such forms of apparatus can give rise to problems of cost, complexity, inconvenience of use and restriction or distortion of the vista afforded the user under some circumstances and for certain purposes, especially where it is necessary to provide for variation of angular elevation of the apparatus or to provide a sighting graticule or equivalent reference device in the apparatus.

The task of the invention is to enable at least some of said problems to be reduced or avoided.

According to a first aspect of the present invention there is provided periscopic apparatus comprising an objective portion joined to an intermediate portion to direct light received by the objective portion along a light path extending longitudinally of the intermediate portion, and an eyepiece portion disposed to receive light from the intermediate portion; wherein said portions are arcuately movable about a mounting axis transverse to the longitudinal direction of said light path, and wherein said eyepiece portion is connected to a mechanism responsive to angular movement of said objective and intermediate portions about said mounting axis to move said eyepiece portion in the opposite rotary direction about an offset axis generally parallel to said mounting axis.

The invention further provides a periscope installation in which an objective portion can be swung in elevation about a nominally horizontal mounting axis, an eyepiece portion swingable in unison with said objective portion, and a mechanism responsive to movement of the objective portion about the mounting axis to move the eyepiece portion arcuately about an offset axis generally parallel to said mounting axis, so that the included angle between the direction of light from the objective portion and the direction of light from the eyepiece portion is reduced as the angular elevation of the objective portion is increased.

The mechanism is preferably arranged so that the rotation about the offset axis is about half the angle of rotation about the mounting axis.

According to a further aspect of the invention there is provided a periscopic sight in or for a weapon or weapon installation having an elevatable firing direction, wherein the sight has an objective portion movable in alignment or parallel with the firing direction, an eyepiece portion movable arcuately about an offset axis transverse to said firing direction, a reference device movable with the objective portion, and a lens device which is adjustable to shift an image of the reference device in the eyepiece.

The invention further provides a periscopic sight comprising an objective portion, an intermediate portion, a reference device, an eyepiece portion and a lens device, wherein the objective portion comprises a main prism and the reference device secured alongside the main prism; wherein the intermediate portion comprises a beam splitter and a lens device to insert a reference image of the reference device into the path of light from the main prism to the eyepiece portion, and characterised by any one or more of the following:: (a) the lens device is adjustable to shift the reference image in the field of view through the main prism; (b) the view through the aperture is elongate and the reference image is offset towards one end of the aperture, preferably to appear in one half of the view presented by the eyepiece portion; (c) the reference device comprises a graticule on a graticule prism arranged to be illuminated by light received from the field of view, from part of said field or from above said field; (d) the main prism, reference device and beam splitter are secured together in a common casing, separate from the eyepiece portion; and/or (e) the eyepiece portion is angularly movable about an axis offset from the intermediate portion and transverse to the path of light from the main prism to the beam splitter.

The invention includes an AFV turret provided with a periscopic sight of the invention, and a weapon adjustable in elevation, wherein the or a mechanism is responsive to weapon elevation to adjust the angular position of the eyepiece portion relative to the objective portion of the periscopic sight.

The mechanism, in a simple form, may comprise gearing or a mechanical linkage between the eyepiece portion and a mounting of the weapon or of the periscopic sight.

The invention will be described further, by way of example, with reference to the accompanying diagrammatic drawings, wherein FIGURE 1 is a two-part diagram showing the general arrangement of optical components of periscopic apparatus of the invention in side and rear elevation; FIGURE 2 is a three-part diagram showing said components in two extreme positions of elevation and in an intermediate position, and indicating pivot points of a mechanism; FIGURE 3 is a part-sectional diagram showing parts of the apparatus, a mounting and a modified form of mechanism.

The apparatus is constructed as a gunsight and comprises a periscope including a main prism 10, an eyepiece prism 11 and an intermediate portion 12 therebetween arranged to give an elongate field of view through a viewing aperture about 120 mm wide by 50 mm high at the eyepiece; and comprises a reference device including a graticule prism 13 joined to one end of the main prism, a beam splitter 14 at the end of the portion 12 adjacent to the eyepiece prism 11, and a lens device 15 between a beam splitter feed prism 16 and a graticule 17 on the prism 13. As indicated in FIGURE 1 the beam splitter 14 is interposed in the light path 19A between the right hand halves of the prisms 10 and 11, leaving a clear path 19B between the left hand halves, so that the reference or graticule image 18 (which is focused at infinity by the device 15) is presented only to a user's right eye, and affording the user simultaneous use of the left eye to observe the view.

The eyepiece prism 11 and its associated housing, filters etc are pivotally carried by a support (e.g. arms 30 one of which is shown in FIGURE 3) which is preferably mounted on a housing (e.g. the casing 31 shown in FIGURE 3) containing and supporting the aforementioned optical elements 10,12,13,14,15,16 and 17, so that the eyepiece prism and its housing are movable about an offset axis 20 passing through said prism 11 and transverse to the path 19 (A,B) a light from the prism 10 to the beam splitter 14, to permit the angle at which the view is presented by the eyepiece for observation to be varied relative to the direction of said path.

For use as a gunsight in an AFV having a turret, the apparatus is carried by a part 32 of the turret e.g. as indicated in FIGURE 3, so that the viewing direction 21 through the main prism is closely parallel to the firing direction of a weapon co-mounted on the turret to be adjustable in elevation therewith about a mounting axis 22 parallel with the axis 20; and a mechanism is provided to move the eyepiece prism about the axis 20 as the elevation of the viewing direction 21 is varied.

As indicated in FIGURES 1 and 2 the viewing direction 21 is movable in elevation through about 75 of arc from a depressed limit of 15 depressed below a nominal horizontal to a elevation of 600 above that horizontal, and the prism optics are arranged so that in a mid-position the path 19 is nominally vertical and the direction 21 is elevated at about 22 to 230. The provision of an obtuse angle between the direction 21 and the path 19 is advantageous. The optics of the graticule prism are arranged to collect light from a direction about 13 above the direction 21.

The mechanism is arranged to counter-rotate the eyepiece prism about the axis 20 to reflect light from the beam-splitter along an image path 23 which is thereby maintained near to the horizontal. The mechanism is arranged to give a reduction of about 2 to 1 in the relationship between arcuate movements about the axis 22 to the movement about the axis 20 so that at the the mid-position the angle between the paths 19 and 23 is about 900, with a progressive reduction of that angle to about 71 at maximum depression (as indicated in chain lines in FIGURE 1) and a progressive increase to about 109 at maximum elevation (as indicated in broken lines in FIGURE 1).The mechanism may comprise a linkage, as partially indicated in FIGURE 2, in which a static reference pivot 24 has a nominally horizontal separation X from the axis 22, an actuating pivot 25 has a separation of 2X from the axis 20 and is fixed to the eyepiece prism, and in which a link 26 connects said pivots. The link may be adjustable in length to vary said angular relationships between the paths 19 and 23.

In a form of the apparatus having an overall height (in the midposition) of about 265 mm, the geometry indicated in FIGURE 2 results in the eyepiece prism moving through a shallow arc, between the positions maximum depression and elevation, of about 170 mm in horizontal distance and 30 mm vertical distance.

Such distances are particularly easily accommodated by head movements of a user, and, because of the maintenance of a near horizontal viewing angle, such movements are near linear and do not involve any inconvenient, awkward or stressfully distracting angular head movements.

In the modification shown in FIGURE 3, the mechanism comprises gearing including a fixed gear 33, co-axial with a trunnion or pivot 34 carried by the part 32 to carry the casing 31 for movement about the axis 22; a driven gear 35 fixed to co-axial stub shafts 36 which are pivotally carried by the arms 30 via bearings 37 and are fixed to the housing 38 of the eyepiece prism 11 co-axial with the axis 20; and an idler or planet gear 39 mounted on the casing via a pivot 40.

The gear train 33,39,35 is arranged so that there is a 2 to 1 step down ratio to the driven gear 35 and so that the movement about the axis 20 is contrary to the direction of rotation of the casing 31 about the axis 22.

The invention is not confined to details of the foregoing example, and includes and provides within its scope a weapon, apparatus or an installation incorporating a periscope or sight having any novel feature or part, or novel combination of features and/or parts, disclosed herein and/or in the drawings, and mechanical or functional equivalents thereof.

For example, the periscope with adjustable eyepiece prism may be employed without any reference device, or the sight may be of monocular form in which the left hand halves of the main and eyepiece prisms and the intermediate portion in line therebetween are omitted.

The lens device 15 may be a doublet lens and may be presettable or adjustable. The eyepiece prism may be carried by or linked to the casing 31 to swing therewith, and may be provided with an electronically or otherwise controlled mechanism to move the eyepiece prism about the axis 20 in response to elevational movements of the apparatus in relation to a structure in or on which the apparatus is disposed. The intermediate portion may comprise an optically transparent body to which the beam splitter and objective or main prism are bonded to form a rigid structure within the casing. The angles mentioned herein are by way of example and may be varied to a considerable extent. The relationship between the arcuate movements about the axes 20 and 22 may be non-linear and only approximate to 2 to 1. In a vehicle such as an AFV the users seat may be powered to move fore and aft in the viewing direction in unison with the eyepiece prism (and the weapon).

The periscope sight is robust, easy to manufacture, simple to install and extremely convenient and effective to use.

Claims (9)

1. Periscope apparatus comprising an objective portion joined to an intermediate portion to direct light received by the objective portion along a light path extending longitudinally of the intermediate portion, and an eyepiece portion disposed to receive light from the intermediate portion; wherein said portions are arcuately movable about a mounting axis transverse to the longitudinal direction of said light path, and wherein said eyepiece portion is connected to a mechanism responsive to angular movement of said objective and intermediate portions about said mounting axis to move said eyepiece portion in the opposite rotary direction about an offset axis generally parallel to said mounting axis.

2. A periscope- installation in which an objective portion can be swung in elevation about a nominally horizontal mounting axis, an eyepiece portion swingable in unison with said objective portion. and a mechanism responsive to movement of the objective portion about the mounting axis to move the eyepiece portion arcuately about an offset zL, axis generally parallel to said mounting axis, so that the included angle between the direction of light from the objective portion and the direction of light from the eyepiece portion is reduced as the angular elevation of the objective portion is increased.

3. An apparatus or installation as claimed in Claim 1 or 2 wherein the mechanism is arranged so that the rotation about the offset axis is about half the angle of rotation about the mounting axis.

4. A periscopic sight in or for a weapon or weapon installation having an elevatable firing direction, wherein the sight has an objective portion movable in alignment or parallel with the firing direction, an eyepiece portion movable arcuately about an offset axis transverse to said firing direction, a reference device movable with the objective portion, and a lens device which is adjustable to shift an image of the reference device in the eyepiece.

5. A periscopic sight comprising an objective portion, an intermediate portion, a reference device, an eyepiece portion and a lens device, wherein the objective portion comprises a main prism and the reference device secured alongside the main prism; wherein the intermediate portion comprises a beam splitter and a lens device to insert a reference image of the reference device into the path of light from the main prism to the eyepiece portion, and characterised by any one or more of the following:: (a) the lens device is adjustable to shift the reference image in the field of view through the main prism; (b) the view through the aperture is elongate and the reference image is offset towards one end of the aperture, to appear in one half of the view presented by the eyepiece portion; (c) the reference device comprises a graticule on a graticule prism arranged to be illuminated by light received from the field of view, from part of said field or from above said field; (d) the main prism, reference device and beam splitter are secured together in a common casing, separate from the eyepiece portion; and/or (e) the eyepiece portion is angularly movable about an axis offset from the intermediate portion and transverse to the path of light from the main prism to the beam splitter.

6. An AVF turret provided with a periscopic apparatus, installation or sight as claimed in any preceding claim, and a weapon adjustable in elevation, wherein the or a mechanism is responsive to weapon elevation to adjust the angular position of the eyepiece portion relative to the objective portion.

7. A turret as claimed in Claim 6 wherein the mechanism comprises gearing or a mechanical linkage between the eyepiece portion and a mounting of the weapon or of the periscopic sight or apparatus.

8. A periscopic sight, apparatus or installation substantially as hereinbefore described with reference to FIGURES 1 and 2, or FIGURES 1 to 3 of the accompanying drawings.

9. An AVF turret provided with a periscopic gunsight as claimed in Claim 8.