Abstract:
A reticle of a projectile weapon aiming system such as a riflescope includes a primary aiming mark adapted to be sighted-in at a first selected range and further includes a plurality of secondary aiming marks spaced apart below the primary aiming mark. The secondary aiming marks are positioned to compensate for ballistic drop at preselected incremental ranges beyond the first selected range, for a selected group of ammunition having similar ballistic characteristics. Angles subtended by adjacent aiming marks of the reticle can be adjusted by changing the optical power of the riflescope, to thereby compensate for ballistic characteristics of different ammunition. In some embodiments, the reticle includes a set of windage aiming marks spaced apart along at least one secondary horizontal axis intersecting a selected one of the secondary aiming marks, to facilitate compensation for the effect of crosswinds on the trajectory of the projectile.

Description:
RELATED APPLICATION  
       [0001]     This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 60/626,967, filed Nov. 10, 2004. 
     
    
     COPYRIGHT NOTICE  
       [0002]     ©2004 Leupold &amp; Stevens, Inc. A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 37 CFR § 1.71(d).  
       TECHNICAL FIELD  
       [0003]     This application relates to projectile weapon aiming systems such as riflescopes, to reticle configurations for projectile weapon aiming systems, and to associated methods of compensating for ballistic characteristics.  
       BACKGROUND OF THE INVENTION  
       [0004]     Projectile weapon aiming systems are discussed herein principally with reference to their use on rifles and embodied in telescopic sights commonly known as riflescopes. It will become apparent, however, that projectile weapon aiming systems may include aiming devices other than riflescopes, and may be used on weapons other than rifles, which are capable of propelling projectiles along substantially predeterminable trajectories, e.g., handguns, crossbows, and artillery.  
         [0005]     A factor that must be taken into account in long-range shooting is the curved trajectory traversed by a bullet or other projectile as it falls from its initial trajectory while traveling the distance from the gun to the target, i.e., “range.” An aiming line of sight emanating from a reticle aiming mark of a riflescope rigidly affixed to the gun is straight, and hence the line of sight can intersect the curved trajectory only at a discrete range. At other ranges the projectile will pass below the aiming line of sight, necessitating the use of elevation adjustments for aiming.  
         [0006]     A challenge in a long-range shooting environment is ranging a fairly small target at long distances. Typically, an operator looks for a target of a known height. For example, a operator may search for a target of approximately one meter in height or length, or other known target sizes that can be easily superimposed or divided to provide a one meter target. The target is then bracketed between reticle aiming marks which represent angularity. The known target height is divided by the bracketed angular value which may be measured in milliradians to provide a range. A ranging reticle may have a 10 milliradian scale to range a one meter target within an average effective range of 100 meters to 1000 meters. The scale is non-linear and the ranging process is easily implemented to 500 meters. In practice, a one meter target will subtend 10 milliradians at 100 meters, and two milliradians at 500 meters. At 1000 meters, the target will subtend one milliradian and the operator must perform 50% of the effective range estimation within the span of 1 milliradian. This becomes a difficult task due to the lack of scale resolution and because the target is further away.  
         [0007]     A “mil-dot” reticle was developed by the U.S. Marine Corps in the late 1970s as an aid for a soldier in estimating distances. The mil-dot reticle has since become the military standard for range estimating within all branches of the service. The term “mil-dot” refers to milliradian, and the dot is spaced in 1 mil increments on the crosshairs. By using a formula, a table is generated based on the sized of the target being range-estimated. The viewed target is bracketed between the dots and the generated table is consulted. The round or football-shaped dots of a mil-dot reticle often obstruct viewing in long ranges. Furthermore, as with other conventional reticles, the mil-dot reticle does not provide sufficient scale resolution for ranges exceeding 500 meters.  
         [0008]     U.S. Pat. No. 6,032,374 of Sammut and U.S. Pat. No. 5,920,995 of Smith, propose reticles having a series of secondary aiming marks spaced below a primary aiming mark at predetermined intervals for compensating for bullet drop. Sammut and Smith further include a rangefinder offset from the crosshairs for determining or estimating an observed range based on an object&#39;s height. The rangefinder has evenly spaced marks at a scale to assist in long distance estimation. After determining a range, the shooter selects the secondary aiming mark most closely corresponding to the observed range. However, the rangefinders are separate from the crosshairs and cannot be used for ballistic drop compensation or for horizontal leading. The secondary aiming marks of Sammut and Smith are not scaled to assist in accurately estimating ballistic drop and horizontal leading for distances greater than 500 meters.  
         [0009]     The present inventors have recognized a need for an improved projectile weapon aiming system for accurately compensating for ballistic drop and windage for a variety of ammunition having different ballistic characteristics.  
       SUMMARY OF THE INVENTION  
       [0010]     In accordance with preferred embodiments, a reticle is located proximate a rear focal plane of a riflescope, an erector lens assembly and an ocular of the riflescope. The reticle is for use in a projectile weapon aiming system and includes a primary aiming mark and primary horizontal and vertical sight lines. The primary horizontal and vertical sight lines include a central portion extending radially from a primary aiming mark and a post portion extending radially from the central portion. The post portions may be at least three times thicker than the central portions to draw a shooter&#39;s eye to the thinner central portions.  
         [0011]     Secondary and tertiary marks are positioned on the sight lines to provide range finding and lead compensation for distances less than 500 meters. Tertiary marks may be disposed equidistantly between adjacent secondary marks to subdivide a unit of measure indicated by the secondary marks. Quaternary or long range marks are positioned on the sight lines and provide scale resolution for range finding and lead compensation at distances greater than 500 meters. The quaternary marks are positioned proximate to the post portions and remote from the primary aiming mark to reduce visual obstruction for short range targets. A plurality of quaternary marks may be disposed between a pair of secondary marks to indicate incremental units of measure. The secondary, tertiary, and quaternary aiming marks are further positioned to provide hold over compensation for ballistic drop at preselected incremental ranges for an elected group of cartridges. The secondary, tertiary, and quaternary aiming marks may have a thickness approximately equal to the central portions to reduce visual obstruction.  
         [0012]     Additional aspects and advantages of this invention will be apparent from the following detailed description of embodiments, which proceeds with reference to the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a side elevation view of a riflescope mounted on a rifle in accordance with a preferred embodiment.  
         [0014]      FIG. 2  is a schematic diagram showing optical elements of a riflescope in accordance with a preferred embodiment.  
         [0015]      FIG. 3  is a view of a reticle in accordance with a preferred embodiment as viewed through an ocular (eyepiece) of a riflescope.  
         [0016]      FIG. 4  is an enlarged view of the reticle of  FIG. 3 .  
         [0017]      FIG. 5  is an enlarged view of a portion of the reticle of  FIG. 4 .  
         [0018]      FIG. 6  is a view of a reticle of  FIG. 4  with indicated holdover compensation for indicated cartridges.  
         [0019]      FIG. 7  is a view of a reticle of FIG. with indicated holdover compensation for indicated cartridges. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0020]     Throughout the specification, reference to “one embodiment,” “an embodiment,” or “some embodiments” means that a particular described feature, structure, or characteristic is included in at least one embodiment. Thus appearances of the phrases “in one embodiment,” “in an embodiment,” or “in some embodiments” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.  
         [0021]     Furthermore, the described features, structures, characteristics, and methods may be combined in any suitable manner in one or more embodiments. Those skilled in the art will recognize that the various embodiments can be practiced without one or more of the specific details or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or not described in detail to avoid obscuring aspects of the embodiments.  
         [0022]      FIG. 1  is a side elevation view of a riflescope  10  mounted to a rifle  14  in accordance with a preferred embodiment.  FIG. 2  is a schematic diagram showing an arrangement of optical elements  16  of riflescope  10 , together with ray trace lines  18  indicating the path of light from an observed object (not shown) located to the left of the assembly of optical elements  16 , as the light travels through the optical system along an optical path. With reference to  FIGS. 1 and 2 , riflescope  10  includes a tubular housing  20  that supports at opposite ends an objective or objective lens assembly  22  and an ocular or ocular lens assembly  26  (sometimes referred to as an eyepiece or eyepiece lens assembly). Objective  22  focuses the image of an observed object at a first (front) focal plane  28  located medially of objective  22  and ocular  26 . An erector lens assembly  30  interposed between objective  22  and ocular  26  inverts the image and refocuses it at a second (rear) focal plane  32  between erector lens assembly  30  and ocular  26 . A preferred riflescope  10  may comprise, for example, a VARI-X° III brand riflescope sold by Leupold &amp; Stevens, Inc., Beaverton, Oregon, USA, modified according to various preferred embodiments to include a reticle  40  of the kind described below. At least a part of erector lens assembly  30  is movable in response to rotation of a power selector ring  34  or other power selector mechanism to adjust the optical power of riflescope  10  within a predetermined range of magnification. For example, the optical power of riflescope  10  may range between approximately 8.5× and 25× magnification, in accordance with a first preferred embodiment, or between approximately 6.5× and 20× magnification, in accordance with an alternative embodiment. Other embodiments may allow optical power adjustment within different ranges of adjustment, such as 4.5-14×, 3.5-10×, and 2.5-8×, for example, the optical zoom ratio in each instance being approximately 3:1. In yet other embodiments, the optical power of riflescope  10  may be fixed.  
         [0023]     Reticle  40  is located in the optical path between objective  22  and ocular  26  and more preferably between erector lens assembly  30  and ocular  26 , at or adjacent second focal plane  32 . By way of example, reticle  40  may be used in a riflescope  10  in a configuration of certain riflescopes sold by Leupold &amp; Stevens, Inc., Beaverton, Oregon, USA under the trademarks LPS®, VARI-X®, VX®, and others. However, the reticles described herein are not limited to use in riflescopes or with rifles, but may also be used in various other types of sighting devices and projectile weapon aiming devices and may be used to aim one or more of a variety of projectile weapons, such as rifles, pistols, crossbows, artillery, and others.  
         [0024]      FIG. 3  is a pictorial representation of an embodiment of reticle  40  as viewed through ocular  26  of riflescope  10 . Reticle  40  is preferably formed on a substantially flat disc of optical quality material, such as glass or plastic, and includes a primary aiming point  50  defined by the intersection of a primary horizontal sight line  52  and a primary vertical sight line  54 . While primary sight lines  52  and  54  and other indicia, described below, may be marked on the surface of a transparent reticle disc, they may also be embodied in other forms, such as reticle wires, iron sights, illuminated reticle devices, projected targeting displays, head-up displays, simulated reticle images, and the like. Thus, the terms “reticle”, “mark”, “marking”, “marks”, “lines”, and the like are not limited to permanent inscriptions on a physical object, but are intended to also include all kinds of visually perceptible patterns, signs, and symbols, regardless of the way in which they are created and regardless of whether their elements are permanent or transitory in nature, or a combination of both permanent and transitory elements.  
         [0025]     The primary horizontal and vertical sight lines  52 ,  54  include central portions  56 ,  58  respectively that extend radially from primary aiming point  50 . Primary horizontal and vertical sight lines  52 ,  54  further include one or more widened post portions  60 ,  62 , respectively, that extend radially from a corresponding central portion  56 ,  58 . Post portions  60 ,  62  may be one and a half times thicker than central portions  56 ,  58  of primary horizontal and vertical sight lines  52  and  54 , and may be at least three times thicker, to draw a shooter&#39;s eye to the thinner central portions  56 ,  58  and thereby help the shooter to locate primary aiming  50 . In some embodiments, innermost ends  64  of widened post portions  60 ,  62  may serve as reference points for range estimation or windage compensation.  
         [0026]     Referring to  FIG. 4 , an enlarged pictorial representation of a portion of the reticle  40  of  FIG. 3  is shown. Reticle  40  includes secondary horizontal aiming marks  66   a - e  equidistantly spaced along the horizontal central portions  56 . The secondary horizontal aiming marks  66   a - e  are spaced to compensate for wind effect and to lead a moving target. Reticle  40  further includes secondary vertical aiming marks  68   a - e  equidistantly spaced along the vertical central portions  58 . The secondary aiming marks  66   a - e ,  68   a - e  have a thickness that is approximately equivalent to or less than their respective central portions  56 ,  58  and are finer than the circular, oval, or football shapes of conventional mil-dots. Accordingly, the secondary aiming marks  66   a - e ,  68   a - e  are less likely to obscure targets at long ranges. As can be appreciated, finer marks afford greater target visibility and more accurate shot placement. In the depicted embodiment, each central portion  56 ,  58  includes five secondary aiming marks  66   a - e ,  68   a - e  that divide the central portions  56 ,  58  into milliradians. The fifth secondary aiming mark  66   e ,  68   e  terminates the respective central portion  56 ,  58 . A corresponding widened post portion  60 ,  62  extends proximate from the fifth secondary aiming mark  66   e ,  68   e.    
         [0027]     The reticle  40  may further include horizontal and vertical tertiary aiming marks  70   a - d ,  72   a - d  disposed on corresponding central portions  56 ,  58 . The tertiary marks  70   a - d ,  72   a - d  subdivide the measure between the secondary aiming marks  66   a - e ,  68   a - e  into equal halves. Accordingly, a single tertiary aiming mark  70   a - d ,  72   a - d  is disposed equidistant between two adjacent secondary aiming marks  66   a - e ,  68   a - e . In the depicted embodiment, a tertiary aiming mark  70   a - d ,  72   a - d  measures 0.5 milliradians from an adjacent secondary aiming mark  66   a - e ,  68   a - e . As with the secondary aiming marks  66   a - e ,  68   a - e , the tertiary aiming marks  70   a - d ,  72   a - d  have a thickness that is approximately equal to or less than the respective central portions  56 ,  58 . The tertiary aiming marks  70   a - d ,  72   a - d  may have a length less than the secondary aiming marks  66   a - e ,  68   a - e  to indicate the measure of a lesser unit value.  
         [0028]     The reticle may further include horizontal and vertical quaternary aiming marks  74   a - d ,  76   a - d  disposed on corresponding central portions  56 ,  58 . The quaternary aiming marks  74   a - d ,  76   a - d  further subdivide the measure between adjacent secondary aiming marks  66   a - e ,  68   a - e . The quaternary aiming marks may also be  74   a - d ,  76   a - d  referred to as long range aiming marks as they provide a scale for distances at greater than 500 meters. The quaternary aiming marks  74   a - d ,  76   a - d  indicate less unit value than the tertiary aiming marks  70   a - d ,  72   a - d . Thus, a plurality of quaternary aiming marks  74   a - d ,  76   a - d  may be incrementally disposed between secondary aiming marks  66   a - e ,  68   a - e . The quaternary aiming marks  74   a - d ,  76   a - d  may indicate 0.2, 0.25, and 0.33 value of a measure between a pair of adjacent secondary aiming marks  66   a - e ,  68   a - e . With secondary aiming marks  66   a - e ,  68   a - e  spaced one milliradian apart, the quaternary aiming marks  74   a - d ,  76   a - d  may indicate 0.2, 0.25, or 0.33 milliradians. The quaternary aiming marks  74   a - d ,  76   a - d  have a thickness that is approximately equal to or less than the respective central portions  56 ,  58 . The quaternary aiming marks  74   a - d ,  76   a - d  may have a length less than the secondary aiming marks  66   a - e ,  68   a - e  and the tertiary aiming marks  70   a - d ,  72   a - d  to indicate the measure of a lesser unit value. Although milliradians have been referenced herein, alternative units may be used to reference an angle subtend, such as minute of angle (MOA) wherein 1 MOA= 1/60th degree.  
         [0029]     The secondary and tertiary aiming marks  66   a - e ,  68   a - e ,  70   a - d ,  72   a - d  provide ranging and leading reference for distances up to 500 meters. For distances greater than 500 meters, the quaternary aiming marks  74   a - d ,  76   a - d  provide scale resolution for increased ranging and leading precision. The finer increments of the vertical quaternary aiming marks  76   a - d  enhance the ability to use the reticle for projectile drop compensation at greater distances. The finer increments of the horizontal quaternary aiming marks  74   a - d  can be used at greater distances to accurately estimate windage deflection trajectory and to effectively lead moving targets. The finer thickness of marks  66   a - e ,  68   a - e ,  70   a - d ,  72   a - d ,  74   a - d ,  76   a - d  reduces visual obstruction of a target and facilitates ranging and leading techniques. The thickness of the marks  66   a - e ,  68   a - e ,  70   a - d ,  72   a - d ,  74   a - d ,  76   a - d  is sized appropriately to the magnification for which the reticle is designed. In operation, the scale provided by the reticle  40  may be subdivided and/or combined by a trained operator to produce reference combinations for target ranging, leading, and holdover precision.  
         [0030]     The primary aiming point  50  may be embodied as a transparent aperture with the central portions  56 ,  58  terminating prior to their intersection. So embodied, the primary aiming point  50  reduces obstruction for improved target acquisition at long ranges.  
         [0031]     In the depicted embodiment of  FIG. 4 , five secondary aiming marks  66   a - e ,  68   a - e  are sequentially disposed on corresponding central portions  56 ,  58 . As can be appreciated, the number of secondary aiming marks  66   a - e ,  68   a - e  may vary depending on reticle size and anticipated ranging and leading needs. A tertiary aiming mark  70   a ,  72   a  is disposed between the primary aiming point  50  and the first secondary aiming marks  66   a ,  68   a . Similarly, a tertiary aiming mark  70   b - d ,  72   b - d  is disposed between second, third, and fourth secondary aiming marks  66   b - d ,  68   b - d . Quaternary aiming marks  74   a - d ,  76   a - d  are disposed between the fourth and fifth secondary aiming marks  66   d - e ,  68   d - e.    
         [0032]     Quaternary aiming marks  74   a - d ,  76   a - d  are preferably disposed remote from the primary aiming point  50  and proximate to the widened post portions  60 ,  62 . The distance proximate to the post portions  60 ,  62  is referred to herein as the corner areas  78 . In  FIG. 4 , the corner area  78  may be defined as between the pair of secondary aiming marks  66   d - e ,  68   d - e  which are the closest to the post portions  60 ,  62 . Enhanced resolution for drop and lead compensation at great distances is typically desired in corner areas  78 . Thus, quaternary aiming marks  74   a - d ,  76   a - d  are not disposed between the primary aiming mark  50  and a first secondary aiming mark  66   a ,  68   a  or between secondary aiming marks  66   b - d ,  68   b - d  proximate to the primary aiming point  50 .  
         [0033]     In  FIG. 4 , the tertiary aiming marks  70   a - d ,  72   a - d  provide 0.5 milliradian subdivisions between the secondary aiming marks  66   a - d ,  68   a - d  which provide 1 milliradian subdivisions of the central portions  56 ,  58 . The quaternary aiming marks  74   a - d ,  76   a - d  provide 0.2 milliradian subdivisions on remote or corner areas  78 , of the reticle scale to facilitate accurate ranging beyond 500 meters.  
         [0034]     As can be appreciated,  FIG. 4  is provided for illustrative purposes only and numerous variations in reticle design may be employed and still be within the scope of the invention. For example, the number of secondary aiming marks  66 ,  68  may vary. Quaternary aiming marks  74 ,  76  may also be disposed between third, fourth, and fifth secondary aiming marks  66   c - e ,  68   c - e . However, as the quaternary aiming marks  74 ,  76  are for long distances, they are not disposed between the primary aiming mark  50  and the horizontal and vertical aiming marks  70   a ,  72   a  closest to the primary aiming mark  50 . In such a location, the quaternary or long distance aiming marks  74 ,  76  obstruct target viewing. Tertiary and quaternary aiming marks  70 ,  72 ,  74 ,  76  may also be disposed between the same pair of secondary aiming marks  66 ,  68 .  
         [0035]     Referring to  FIG. 5 , an expanded view of a portion of  FIG. 4  is depicted to illustrate one example of length measurements of secondary, tertiary, and quaternary aiming marks  66   a - e ,  68   a - e ,  70   a - d ,  72   a - d ,  74   a - d ,  76   a - d . The secondary aiming marks  66   a - e ,  68   a - e  may have a length  80  of 0.40 milliradians. The tertirary and quatnerary aiming marks  70   a - d ,  72   a - d ,  74   a - d ,  76   a - d  may have a length  82  of 0.15 milliradians. Such lengths  80 ,  82  are one example of a configuration to facilitate mark and subdivision recognition. The thickness of the marks  66   a - e ,  68   a - e ,  70   a - d ,  72   a - d ,  74   a - d ,  76   a - d  and the central portions  56 ,  58  may vary from about 0.02 milliradians to about 0.06 milliradians. As can be expected the reticle dimensions disclosed herein may vary from an initial view depending on increased or decreased magnification. Nevertheless, ratios between marks  66   a - e ,  68   a - e ,  70   a - d ,  72   a - d ,  74   a - d ,  76   a - d , central portions  56 ,  58 , and posts  60 ,  62  remain constant.  
         [0036]     Referring to  FIGS. 6 and 7 , reticle  40  is shown with holdover markings for four military cartridges. If the time to place a shot is imminent, an operator can compensate for projectile trajectory using predetermined holdover markings. To facilitate better holdover accuracy, vertical marks  68 ,  72 ,  74  provide increments that correlate to any ballistic trajectory. When needed, an operator may forgo ranging, estimate the distance, and use a corresponding mark. In a similar manner, horizontal marks  66 ,  70 ,  74  may be used to estimate windage or movement and lead a target.  
         [0037]     Projectile weapon aiming systems have been described herein principally with reference to their use with rifles and embodied as riflescopes. However, skilled persons will understand that projectile weapon aiming systems may include aiming devices other than riflescopes, and may be used on weapons other than rifles, which are capable of propelling projectiles along substantially predeterminable trajectories, e.g., handguns, crossbows, and artillery. Thus, it will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. The scope of the present invention should, therefore, be determined only by the following claims.