Patent Application
20110005119
This invention relates generally to firearms, and more particularly to sighting systems for firearms.
The depth of field of an optical system, including the human eye, is defined in part by the diameter of the “entrance pupil” to that optical system. The entrance pupil diameter is that dimension which is used, along with a lens focal length, to calculate a lens f-ratio, and which is in turn used to calculate depth of field. An entrance pupil is the projection along the optical axis, towards the first lens surface of an optical system, of an aperture which limits the entry of light beams into that optical system. For the human eye, the first lens surface is the surface of the cornea, and the entrance pupil of the unaided eye is the forward projection of the eye's pupil along the optical axis of the eye onto the cornea. Since the cornea is a converging lens, and the pupil is located slightly behind the surface of the cornea, the entrance pupil to the unaided eye is slightly larger than the true opening in the pupil. To an outside observer, the viewed size of the pupil of the eye is the entrance pupil size, the true size of the pupil being slightly smaller. For the purpose of this application, the size of the eye's pupil, and the size of the entrance pupil, created by the projection of the eye's pupil forward onto the cornea, can be treated as the same, and will be used interchangeably.
If an external aperture is placed in front of the eye, along the optical axis of the eye, it is the projection of the open area of that aperture, along the optical axis of the eye, onto the cornea, that defines the entrance pupil created by the external aperture. If several non-overlapping apertures are present in an optical system, each defining an entrance pupil, the smallest of the non-overlapping entrance pupils is the dominant entrance pupil which drives the depth of field of that optical system. Thus, if a round aperture is placed on the optical axis of the eye, in front of the eye, and if the opening of the aperture is oriented perpendicular to the axis of the eye, and if the diameter of the entrance pupil, created by projecting the aperture along the axis of the eye onto the cornea, is larger than the entrance pupil created by the eye's pupil, the eye's pupil, being smaller than the projection of the larger round aperture, will be the dominant entrance pupil of the eye.
If a round aperture is placed on the optical axis of the eye, in front of the eye, and its opening is oriented perpendicular to the axis of the eye, and the aperture diameter is smaller than the pupil of the eye, and therefore the entrance pupil created by that aperture is smaller than the entrance pupil created by the pupil of the eye, it will then be the external aperture, and not the eye's pupil that creates the dominant entrance pupil to the eye.
If several apertures, whose open areas overlap each other, are present along the optical axis of the eye, it is the projection of their common open area, along the optical axis of the eye, onto the cornea surface, that will define the entrance pupil created by those apertures. If the entrance pupil created by the eye's pupil is larger than the entrance pupil created by the common open areas of the apertures, the common open area of the apertures will be the dominant entrance pupil for the viewer.
If an irregularly shaped aperture is placed along the optical axis of the eye, in front of the eye, and is oriented with its opening perpendicular to the axis of the eye, the projection of that irregular aperture, along the axis of the eye, onto the cornea, will form an irregularly shaped entrance pupil of substantially the same dimensions and form as the irregularly shaped aperture itself. If the irregularly shaped entrance pupil created by the irregularly shaped aperture is smaller than the entrance pupil created by the eye's pupil, it is the irregularly shaped entrance pupil that will dominate the optical system of the eye.
If an irregularly shaped aperture is placed on the optical axis of the eye, in front of the eye, and its opening is oriented perpendicular to the axis of the eye, and the irregular aperture shape is such that the irregularly shaped entrance pupil created by the irregularly shaped aperture overlaps the entrance pupil created by the eye's pupil, it is the common open area of the irregularly shaped entrance pupil from the external irregularly shaped aperture, and the entrance pupil from the eye's pupil that will become the dominant entrance pupil for the viewer.
If an external aperture is placed along the optical axis of the eye, and such aperture is inclined to the optical axis of the eye, the entrance pupil created by the external aperture will be the projection of the open area of the inclined aperture along the optical axis of the eye onto the surface of the cornea. If the projection of the inclined aperture opening along the axis of the eye onto the cornea is smaller than the projection of the eye's pupil onto the cornea, the projected opening of the aperture will determine the entrance pupil of the eye. If the projection of the inclined aperture along the optical axis of the eye onto the cornea of the eye overlaps the projection of the eye's pupil onto the cornea, it is the common open area of the projection of the inclined aperture and the eye's pupil that will define the entrance pupil to the eye.
The depth of field for an optical system is defined relative to the plane in which the optical system is referenced. The degree to which an image can blur vertically is driven by the vertical dimension of the entrance pupil, while the degree to which an image can blur horizontally is driven by the horizontal dimension of the entrance pupil. The traditional paradigm of photography, and our experience with our own human vision, has the entrance pupil as being substantially round and perpendicular relative to the axis of the eye, thus blur in a photograph, or the eye, is typically equal in all directions. If the entrance pupil is not round, it is possible to have different depths of field, and different widths of resulting blur, in differing axes of the image. Examples of such an optical system are the pupils of cat's eyes, where the vertical slit shaped pupil will cause a greater depth of field in the horizontal direction, with less depth of field in the vertical direction. In the field of opthalmology, non-round entrance pupils are also created, using stenopaeic slits. These slits are narrower than the eye's pupil in one axis, but much wider than the pupil in the other axis, so as to create an increased depth of field only in 1 axis of the eye. By rotating the slit, the axis of a patient's astigmatism can be diagnosed.
The brightness of an image being viewed by the human eye is a function of the open area of the entrance pupil. If the entrance pupil is small, less light is able to pass, and the image will be dim. If the entrance pupil is large, more light will pass, and the image will be bright. If no smaller aperture is present, the pupil of the human eye will define a round entrance pupil, of varying diameter, depending on the brightness of ambient light. A typical human pupil in a well lit environment, outdoors, but not exposed to direct sun, is approximately 0.125 inches diameter. Since the pupil is close to the cornea surface, the entrance pupil defined by a 0.125 inches diameter pupil will also be approximately 0.125 inches.
In summary, if an aperture smaller than the pupil is placed along the eye's optical axis, in front of the eye, the smaller aperture will define the entrance pupil of the eye, and drive the depth of field of the eye, as well as the brightness of the image seen by the eye. If an aperture larger than the pupil is placed in front of the eye, the pupil will define the entrance pupil of the eye, and the aperture will not drive the depth of field of the eye, or the brightness of the image.
The United States military issues for service a pair of shoulder fired rifles, both chambered for the 5.56 mm NATO cartridge. One is designated the M16A2/M16A3/M16A4 rifle and the other is designated the M4/M4A1 carbine. Both weapons utilize a common sighting system comprising a rear sight having a leaf style aperture plate with a circular aperture therein and a front sight post. To properly aim the weapon, the horizontal top edge of the front sight post is centered horizontally and vertically on the target, and is also centered in the rear aperture.
Both weapons utilize a rear flip type dual leaf sight having two different aperture sizes from which to choose: a smaller aperture having a diameter of about 0.070 inches for longer ranges, and a larger aperture having a diameter of about 0.200 inches for shorter ranges, a greater field of view, and faster target engagement. The shooter flips the sight leaf having the correct aperture up into view based on the distance to the target. The larger aperture is for near targets, generally less than 200 meters, and the smaller aperture is for distant targets, generally greater than 200 meters.
The larger aperture permits a shooter to locate the front sight post and target in the rear aperture quicker than does the smaller aperture. Hence its suitability for near targets, wherein engagements are quicker. The smaller aperture does not permit the shooter to locate the front sight post and target therein as quickly as the larger aperture, but it does provide for more accurate aiming which is necessary at longer ranges. This is because the smaller aperture acts as a pinhole opening, creating a smaller entrance pupil to the eye, and improving the shooter's depth of field. The small vertical dimension of the smaller entrance pupil causes the horizontal top edge of the front sight post and any horizontal edges on the target to be more clearly focused, and the small horizontal dimension of the smaller entrance pupil causes the vertical side edges of the front sight post, and any vertical edges on the target, to be more clearly focused. This is in contrast to the larger aperture which does not focus the horizontal top edge of the front sight post, the vertical side edges of the front sight post, or the target as much, so they remain somewhat blurry to the shooter. Again, the larger aperture is for near targets, and so speed in aiming is paramount; even though the horizontal top edge and vertical side edges of the front sight post, and the target, are blurry, the sight picture is nonetheless sufficient to obtain accurate hits at closer ranges.
A distinct disadvantage in using the smaller rear circular aperture is that less light is permitted to pass through the aperture. Thus, even though the horizontal top edge and vertical side edges of the front sight post and target are clearly focused, which enhances accuracy in aiming and hence accuracy in shot placement, the front sight post and target are nevertheless dim, which hinders accuracy in aiming ability and hence accuracy in shot placement.
In the case of the M-16 and its aforementioned derivative designs, regardless of any adjustments made to the sight, the rear sight leaf is presented to the shooter at an angle substantially perpendicular to the bore of the rifle, so the axis of the aperture is presented substantially parallel to the optical axis of the shooter's eye. As a result, the entrance pupil created by the aperture is substantially identical to the shape and size of the aperture created in the aperture plate.
The United States military also issues for service a shoulder fired rifle, designated the M-14. This rifle is based on the famous M-1 rifle, designed by John Garand, and issued to US troops starting in WWII, with continued use through the Korea and Viet Nam eras. The M-1 rifle was lauded by Gen. George Patton as the “greatest battle implement ever devised”. Both of these weapons share a common sighting system comprising a front sight blade and a rear sight aperture plate 0.125 inches thick having a 0.069 inches diameter circular aperture formed therein. One side of the circular aperture is chamfered with a 30 degree included angle to a depth of 0.105 inches such that the straight portion of the aperture which is presented to the eye is only 0.020 inches deep. This aperture plate differs from the sight leaf seen on the M-16, and derivative models A2, A3, A4, M4, and M4-A1, or similar rifles, in that the aperture plate of the M-14 and M-1 is mounted in a track which follows a curved path. The arc of said track falls in the same plane as the bore of the rifle, but the curved track has a center of rotation set vertically above the aperture of the rifle, and closer to the muzzle than the aperture. In its lower, or “zero” position, used for engaging targets at under 200 yards, the aperture is oriented substantially perpendicular to the bore so the eye is looking along the axis of the aperture. In this position, the round 0.069 inches diameter aperture projects a round 0.069 inches diameter entrance pupil to the eye.
When the aperture of the M-1 or M-14 rifle is raised to engage targets at greater distances, its swing along the arc of the track in which it travels, moves the aperture not only up, but also causes it to incline forward. As the aperture travels through its full range of motion in the curved track, the aperture will elevate relative to the bore of the rifle, which is the desired consequence to allow a rifle to be aimed at a greater distance, however due to the curved track, the aperture plate also pivots forward up to approximately 15 degrees relative to the shooter, so the aperture is presented to the eye at a 15 degree forward inclination to the bore. In the case of maximum inclination of the aperture leaf to the bore, the 0.020 inches deep by 0.069 inches diameter round aperture presents the eye with an entrance pupil which is a vertically compressed slit, made up of two elliptical arcs, and has dimensions of 0.069 inches wide×0.061 inches tall, so the height of the entrance pupil measured perpendicular to the bore is reduced by approximately 12% versus the diameter of the aperture as measured parallel to the aperture face. In this configuration, if the width of the entrance pupil is calculated as a function of its height, it can be said that the width is 113% of the height.
To properly aim any of the above described weapons, the horizontal top edge of the front sight post is centered horizontally and vertically on the target, and is also centered in the entrance pupil that is created by the aperture. In this configuration, the shooter's line of vision is substantially parallel to the bore. There is a small difference between the true axis of the bore, and the true line of sight of the shooter's eye when the eye is correctly aligned on the target. This small difference is due to the fact that the sights are offset from the bore, and also the difference in angle is adjusted to compensate for the drop of the bullet and wind drift during flight. The correct alignment of the sights is such that the line from the eye, through the center of the aperture, and past the top edge of the front sight will align with the point on the target where the bullet will impact. The correct alignment of the bore is such that it allows the bullet to be launched in a direction such that, allowing for wind drift and gravitational drop, the bullet will impact the target at the same point where the sights are pointed. The difference between the axis of the bore and the alignment of the sights is typically less than 1 degree, and in target shooting this difference is typically expressed in Minutes of Angle (MOA). In the following discussion, the small difference between these angles will be treated as being substantially zero. For the purposes of this discussion, the line of the sight of the shooter's eye while aiming a rifle will therefore be treated as being substantially parallel to the bore of the rifle.
In competition shooting with the U.S. service rifle, for example in NRA High Power rifle competition, it is customary to utilize a “6 o'clock hold.” This means that the horizontal top edge of the front sight post is placed at the bottom edge of the circular bull's eye of the target, i.e. at 6 o'clock. Experience has shown that the most important features to be in focus, for an accurate 6 o'clock hold, and hence, accurate target shooting, are the horizontal top edge of the front sight post, and the horizontal bottom edge of the target. The focus of the vertical side edges of the front sight post and of the vertical side edges of the target are less critical.
A problem with traditional round aperture sights is that once the aperture is reduced in size to provide optimal focus on the horizontal top edge of the front sight post and the horizontal bottom edge of the target, the amount of light passing through the opening is so limited that the target and the front sight post appear dim to the shooter. In other words, a sub-optimal focus must be accepted in order for the amount of light passing through the opening to be sufficient for the front sight post and target to appear bright to the shooter.
Accordingly, it is desirable to provide a rear aperture sight for a rifle which creates an entrance pupil to the eye that has a vertical dimension that is significantly smaller than the pupil, so as to cause the horizontal top edge of the front sight post and the horizontal bottom edge of the bull's eye to be as sharply focused as possible, but the entrance pupil must at the same time present the greatest amount of area to the shooter, so as to be the least restrictive of the amount of light able to pass through the aperture, so as to prevent the front sight post and target from being dim.
In one aspect, the present invention is a rear aperture sight for use in conjunction with a front sight post sight on a rifle, the front sight post having a horizontal top edge and vertical side edges. The rear aperture sight comprises a rear sight adapted to be mounted on the rifle. The rear sight has a horizontally elongated aperture formed therein having height and width dimensions. The width dimension is greater than the height dimension. The height dimension is of such a value that the aperture is adapted to cause the horizontal top edge of the front sight post and a horizontal edge of a target to be sharply focused. The width dimension is of such a value that the aperture is adapted to permit a sufficient amount of light to pass through the aperture so that the front sight post and the target are bright.
In another aspect, the invention is a rifle having a receiver and a barrel, and having the rear aperture sight and the front sight post sight of the above mounted on the receiver and barrel, respectively.
In another aspect, the invention is the combination of the rear aperture sight and the front sight post sight of the above.
The aperture of the rear sight can have a number of possible width-to-height aspect ratios, width and height dimensions, and shapes. The width dimension can be in a range of about 110% to about 500% of the height dimension; the width dimension can be in a range of about 120% to about 300% of the height dimension; the width dimension can be in a range of about 140% to about 160% of the height dimension. The height dimension can be in a range of about 0.010 inches to about 0.100 inches. The width dimension can be in a range of about 0.011 inches to about 0.20 inches. The aperture can be rectangular shaped, rectangular shaped with radiused corners, oval shaped, hexagonal shaped with vertices positioned at 3 o'clock and at 9 o'clock, and/or elliptical shaped. The rear sight can be a leaf sight.
The aperture can be defined by two arc segments s1 and s2, having identical chords c1 and c2, respectively, defined by included angles θ1 and θ2, respectively, of circles having radii R1 and R2, respectively. Radii R1 and R2 and angles θ1 and θ2 are selected such that chords c1 and c2 are of equal length. The circular segments are positioned such that the chords c1 and c2 are co-linear and oriented horizontally. In one aspect, R1=R2=R and θ1=θ2=θ. In another aspect, R1≠R2 and θ1 ≠θ2. In yet another aspect, w=c1=c2, where w is in a range of about 0.011 inches to about 0.20 inches, and h=h1+h2, where h is in a range of about 0.010 inches to about 0.100 inches. Alternatively the aperture can be defined by two overlapping circles having respective centers A and B, a distance between the centers A and B being AB, the overlapping circles having overlapping circular segments s1 and s2 which have chords c1 and c2, respectively, wherein the chords c1 and c2 are oriented vertically. In that case, w is equivalent to a sum of AB, R1, and R2, and h is equivalent to twice a greater of R1 and R2.
In another aspect, the present invention is a rear aperture sight for use in conjunction with a front sight post on a rifle, the front sight post having a horizontal top edge and vertical side edges. The rear aperture sight comprises a rear sight adapted to be mounted on the rifle. The rear sight has an aperture plate of some thickness with a round aperture of some dimension formed therein, the aperture axis is formed perpendicular to the face of the aperture plate, and the aperture plate is presented to the shooter in an orientation so the axis of the aperture is inclined at some angle to the rifle bore, and also to the optical axis of the eye. Due to the said inclination of the aperture axis, and also the thickness of the aperture plate, the open area of the aperture, projected along the optical axis of the eye onto the cornea, will create a horizontally elongated entrance pupil to the eye, said entrance pupil having height and width dimensions. The width dimension of the entrance pupil is greater than the height dimension. The height dimension of the entrance pupil is of such a value that the entrance pupil is smaller than the pupil of the eye, and will cause the horizontal top edge of the front sight post and horizontal edges of a target to be more sharply focused than if viewed with the naked eye, or if viewed through an identical aperture which were presented to the eye in an orientation so the axis of the aperture was substantially parallel to the bore of the rifle and the axis of the eye. The width dimension of the entrance pupil, being larger than the height dimension, will allow more light to pass through the aperture, so that the front sight post and the target are brighter, than if they were viewed through an entrance pupil which was round and with a diameter equivalent to the height dimension of the entrance pupil.
In another aspect, the present invention is a rear aperture sight for use in conjunction with a front sight post on a rifle, the front sight post having a horizontal top edge and vertical side edges. The rear aperture sight comprises a rear sight adapted to be mounted on the rifle. The rear sight has an aperture plate of some thickness with a round aperture of some dimension formed therein, the axis of the aperture opening is formed at an angle to the face of the aperture plate which is different from perpendicular. The aperture plate is presented to the shooter at an angle substantially perpendicular to the rifle bore, so the axis of the aperture is at an angle different from parallel to the optical axis of the eye. Due to the inclination of the aperture axis at said angle to the aperture plate, and the thickness of the aperture plate, the common open area of the aperture, projected along the optical axis of the eye onto the cornea, will create a horizontally elongated entrance pupil to the eye, said entrance pupil having height and width dimensions. The width dimension of the entrance pupil is greater than the height dimension. The height dimension of the entrance pupil is of such a value that the entrance pupil is smaller than the pupil of the eye, and will cause the horizontal top edge of the front sight post and a horizontal edge of a target to be more sharply focused than if viewed with either the naked eye. The width dimension of the entrance pupil, being larger than the height dimension, is of such a value that the open area of the aperture is adapted to permit a sufficient amount of light to pass through the aperture so that the front sight post and the target are brighter than if they were viewed through an entrance pupil which was round and with a diameter equivalent to the height dimension of the entrance pupil.
In another aspect, the present invention is a rear aperture sight for use in conjunction with a front sight post on a rifle, the front sight post having a horizontal top edge and vertical side edges. The rear aperture sight comprises a rear sight adapted to be mounted on the rifle. The rear sight has at least two aperture plates with apertures formed therein, each aperture having height and width dimensions, and all aperture plates are presented substantially perpendicular to the axis of the eye, but positioned such that the apertures are displaced relative to one another in a vertical direction that is radial to the axis of the bore, such that the projection of their common open areas along the axis of the eye onto the cornea creates an entrance pupil to the eye which is horizontally elongated, said entrance pupil having height and width dimensions. The width dimension of the entrance pupil is greater than the height dimension. The height dimension of the entrance pupil is of such a value that the entrance pupil is smaller than the pupil of the eye, and will cause the horizontal top edge of the front sight post and a horizontal edge of a target to be more sharply focused than if viewed with the unaided eye. The width dimension of the entrance pupil is of such a value that the aperture is adapted to permit a sufficient amount of light to pass through the aperture so that the front sight post and the target are brighter than if they were viewed through an entrance pupil which was round and with a diameter equivalent to the height dimension of the entrance pupil. Examples of aperture shapes which might be utilized in this example are two round apertures, whose vertically overlapped shapes would create a horizontally elongated slit shaped entrance pupil, like a cat's eye. Another example might be the vertical overlap of two square apertures, whose vertically overlapped shapes would create a horizontally elongated rectangular entrance pupil. Other aperture shapes can also be used, such that the effect of a vertical misalignment of the two apertures creates an entrance pupil which is horizontally elongated, relative to its height.
In another aspect, the present invention is a rear aperture sight for use in conjunction with a front sight post on a rifle, the front sight post having a horizontal top edge and vertical side edges. The rear aperture sight comprises a rear sight adapted to be mounted on the rifle. The rear sight has at least two aperture plates with apertures formed therein, the aperture plates having apertures of differing shapes. The aperture plates are presented to the eye such that the projection of their common open area along the axis of the eye onto the cornea forms an entrance pupil to the eye that is horizontally elongated, even though all apertures lie on the optical axis of the eye. For instance, an aperture of the shape of an equilateral triangle pointed “up” can be superimposed on an aperture of the shape of an equilateral triangle pointed “down.” The combination of their collective total areas would form a six pointed star, but the projection of only their common open areas along the axis of the eye onto the cornea would form a horizontally elongated hexagonal entrance pupil with vertices at 3 o'clock and 9 o'clock.
In another aspect, any of the afore described apertures can be created by adding an opaque mask to a transparent substrate, such as a lens, so as to create an aperture for light, without actually creating a hole in the aperture plate.
In another aspect, any combination of any of the above described aperture plates, with aperture holes of differing shapes, formed perpendicular to, or at an angle to the face of the aperture plate, can be presented along the axis of the eye with various aperture plates being presented perpendicular to the axis of the eye, and other aperture plates being presented at an inclination to the optical axis of the eye, and with some apertures being offset from the optical axis of the eye in a vertical direction perpendicular to the bore of the rifle, such that the projection of their common open area along the axis of the eye onto the cornea will form an entrance pupil to the eye which is horizontally elongated relative to its height, said entrance pupil having height and width dimensions. The width dimension of the entrance pupil is greater than the height dimension. The height dimension of the entrance pupil is of such a value that the entrance pupil is smaller than the pupil of the eye, and will cause the horizontal top edge of the front sight post and a horizontal edge of a target to be more sharply focused than if viewed with either the naked eye, or if viewed through an identical aperture which were presented to the eye in an orientation substantially perpendicular to the bore of the rifle. The width dimension of the entrance pupil is of such a value that the aperture is adapted to permit a sufficient amount of light to pass through the aperture so that the front sight post and the target are brighter than if they were viewed through an entrance pupil which was round and with a diameter equivalent to the height dimension of the entrance pupil.
In another aspect, the invention is a rifle having a receiver and a barrel, and having the rear aperture sight and the front sight post sight of any of the above descriptions mounted on the receiver and barrel, respectively.
In another aspect, the invention is the combination of the rear aperture sight and the front sight post sight of any of the above descriptions.
The entrance pupil created by the aperture of the rear sight can have a number of possible width-to-height aspect ratios, width and height dimensions, and shapes. The width dimension can be in a range of about 125% to about 500% of the height dimension; the width dimension can be in a range of about 150% to about 400% of the height dimension; the width dimension can be in a range of about 200% to about 300% of the height dimension. The height dimension can be in a range of about 0.010 inches to about 0.100 inches. The width dimension can be in a range of about 0.0125 inch to about 0.20 inch. The entrance pupil can be oval or elliptical shaped, slit shaped, like a cat's eye, rectangular shaped, rectangular shaped with radiused corners, and/or hexagonal shaped with vertices positioned at 3 o'clock and at 9 o'clock, etc. The apertures used to create the entrance pupil can be round, square, triangular, rectangular, elliptical, oval, and/or comprised of two overlapping circular holes whose centers are displaced horizontally from one another, etc.
The aperture plate can have different thicknesses. The thickness can be in the range of about 0.0005 inches to about 0.500 inches, the thickness can be in the range of about 0.001 inches to about 0.250 inches, the thickness can be in the range of about 0.002 inches to about 0.125 inches.
These above defined shapes of the entrance pupil to the eye can be created by creating an aperture in the aperture plate, or an aperture in an insert which is held by the aperture plate, such that the axis of the aperture or the axis of the insert is held at an angle different from perpendicular to the aperture plate, said aperture plate is then presented to the eye at an angle essentially perpendicular to the bore of the rifle barrel. As used in the claims, “an aperture plate having an aperture formed therein” shall be deemed to embrace an aperture formed in an insert which is held by the aperture plate.
These above defined shapes of the entrance pupil to the eye can be created by creating an aperture in an aperture plate, or an aperture in an insert which is held in an aperture plate, such that the axis of the aperture or the axis of the insert is substantially perpendicular to the aperture plate, said aperture plate is then presented to the eye at some inclination to the axis of the bore of the rifle barrel.
The invention thus provides a rear aperture sight for a rifle which creates an entrance pupil to the eye that is elongated horizontally relative to its height, and whose height is smaller than the pupil of the eye, so as to more sharply focus the horizontal top edge of the front sight post and the horizontal bottom edge of the target than if viewed by the unaided eye, while at the same time permitting sufficient light to pass therethrough, so that the front sight post and target are brighter than if viewed through a round aperture with a diameter equal to the entrance pupil height.
These, and other features and advantages of the present invention, will become more readily apparent during the following detailed description taken in conjunction with the drawings herein, in which:
Application Ser. No. 11/619,953 sets forth the benefits of a rear sight utilizing various designs of horizontally elongated apertures, all of which are created using an aperture plate, similar to that being used on an M-16 rifle, or one of it's derivative designs A2, A3, A4, M4, M4-A1, or similar rifles, such aperture plate being presented substantially perpendicular to the bore of the barrel and also substantially perpendicular to the axis of view of the shooter. The '953 application teaches that when a horizontally elongated aperture, whose height is less than the diameter of the pupil, is oriented with its axis substantially parallel to the optical axis of the eye, it will create a horizontally elongated entrance pupil to the eye of substantially the same size and shape as the aperture, and will thus aid the eye in focusing on the horizontal edge of the front sight post, and on the horizontal edge of the target, while allowing more light to pass than if the aperture were round with a diameter of the vertical dimension of the elongated aperture, thereby keeping the image brighter than the described round aperture would allow.
This continuation application teaches various methods by which a horizontally elongated entrance pupil can be created for the eye, by creating various forms of horizontally elongated apertures, which are presented in an aperture plate with the aperture plate being substantially perpendicular to the eye and the axis of the aperture being substantially parallel to and co-linear with the optical axis of the eye. This continuation application also teaches how a horizontally elongated entrance pupil can be created for the eye by methods other than by creating a horizontally elongated aperture in an aperture plate. These methods will create a horizontally elongated entrance pupil to the eye, so as to provide improved depth of field and improved focus on horizontal edges being viewed, while allowing more light to enter the eye, and creating a brighter image, than if a round aperture were used whose diameter is equal to the vertical dimension of the horizontally elongated aperture.
Referring to
It will be appreciated that many different shapes, other than round, which are not horizontally elongated, could be used for the aperture 11, as described in
It will be appreciated that in
Preferably, for a horizontally elongated aperture, the width w is in a range of about 110% to about 500% of the height h. More preferably, the width w is in a range of about 120% to about 300% of the height h. Most preferably, the width w is in a range of about 140% to about 160% of the height h. Other width w to height h aspect ratios can of course be used, and the invention is not to be limited to the values specified herein.
Preferably, for a horizontally elongated aperture, the height h is in a range of about 0.010 inches to about 0.100 inches. Preferably, the width w is in a range of about 0.011 inches to about 0.20 inches. Other width w and height h dimensions can of course be used, and the invention is not to be limited to the values specified herein.
The aperture 31, can be rectangular shaped as shown in
Referring now to
Alternatively, with the chords c1 and c2 oriented vertically as in
The horizontally elongated entrance pupils created by the invention of
Preferably, the height of the entrance pupil h, is in a range of about 0.010 inches to about 0.100 inches. Preferably, the width of the entrance pupil w, is in a range of about 0.011 inches to about 0.20 inches. Other width w, and height h, dimensions can of course be used, and the invention is not to be limited to the values specified herein.
The entrance pupil 80, can be slit shaped, as shown in
Those skilled in the art will readily recognize numerous adaptations and modifications which can be made to the present invention which will result in an improved aperture sight for a rifle, yet all of which will fall within the spirit and scope of the present invention as defined in the following claims. For example, the rear sight could be any structure capable of having an aperture formed therein, and not just the aperture plate shown in the drawings. Accordingly, the invention is to be limited only by the scope of the following claims and their equivalents.
This application is a continuation-in-part of application Ser. No. 11/957,963, which is a continuation-in-part of application Ser. No. 11/619,953, and a continuation-in-part of application Ser. No. 11/619,953, both of which are hereby incorporated by reference herein as if fully set forth in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11957963 | Dec 2007 | US |
| Child | 12837082 | US | |
| Parent | 11619953 | Jan 2007 | US |
| Child | 11957963 | US |
