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[0001] Not Applicable
[0002] Not Applicable
[0003] Not Applicable
[0004] This invention relates generally to targeting devices used to aim firearms and the like, and more specifically to a riflescope that calculates a trajectory and indicates a compensated aim point.
[0005] Since the introduction of firearms, users have struggled to compensate for the effects of gravity. Gravity acting on the projectile during its time-of-flight causes a vertical drop. The time-of-flight is a function of the horizontal target distance, initial velocity, and deceleration due to the aerodynamics of the projectile and drag imparted by the air resistance. This problem has become increasingly challenging as modern improvements in firearms and ammunition have increased their effective range.
[0006] Originally firearms were constructed with iron sights. This made targeting difficult at longer ranges. The problem was partially solved through the introduction of riflescopes with telescopic sights; these provided a detailed view of the target at longer ranges. However this introduced a new problem, the need to adjust the aim point to compensate for the effects of gravity on the projectile. Initially shooting enthusiasts used a sight-in method where the projectile trajectory was determined at several ranges. This method proved problematic since the user was required to estimate the horizontal target distance and manually adjust the aim point. In an attempt to improve the target range estimation riflescopes were introduced with mil-dot reticles. Although this provided a better method of estimating target distance, it still required the user to manually adjust the aim point.
[0007] Thereafter, inventors proposed more advanced firearm range estimation and compensation devices. A search of prior art did not disclose any patents that read directly on the claims of the instant invention. U.S. Pat. No. 5,771,623 to Pernstich et al. (Jun. 30, 1998) discloses a complex telescopic sight that integrates the laser transmitter, laser receiver and measured range display into the visual sight path. Although this device as described provides a method for accurately measuring the line-of-sight range it is still prone to inaccuracies because it requires the user to estimate the affects of uphill/downhill shooting, variations in muzzle velocity, and variations in ballistic coefficient. In addition, the incorporation of the laser transmitter and display into the visual sight path requires a more complex alignment and assembly resulting in a fragile arrangement that is costly to manufacture.
[0008] U.S. Pat. No. 6,252,706 to Kaladgew (Jun. 26, 2001) discloses a range compensating telescopic sight with automatic aiming and adjustment. Although this device as described indicates the use of a stepper motor to automatically adjust the original position of the sight to the required point of aim. As proposed the device actually moves the entire riflescope assembly, this is more complicated than necessary and thus more expensive. The simpler method of adjusting the aim point is to couple the stepper motor directly to the manual elevation adjustment knob contained on conventional riflescopes.
[0009] U.S. Pat. No. 6,269,581 to Groh (Aug. 7, 2001) discloses a range compensating riflescope that calculates and automatically indicates an impact point with a display integrated into the visual sight path. As described the display indicates the calculated impact point with a horizontal line, however to provide the necessary accuracy this display would need a very fine resolution resulting in higher component costs. In addition, the optical alignment and mounting of the display to provide an adequate level of accuracy would be complex and costly to manufacture. As with the previous invention, this prior art fails to identify a method to compensate for the affects of shooting uphill or downhill. As described the invention uses the bullet weight as the parameter of interest to determine the deceleration due to drag from air resistance. However, the actual parameter that characterizes the deceleration due to drag from air resistance is the bullets commonly published ballistic coefficient. In addition, the invention describes the calculation is based on a user input parameter of elevation to factor in the air pressure and resulting resistance. However, air pressure is dependent on elevation, current weather conditions, and temperature. Therefore a much simpler and more accurate method is to incorporate a barometric pressure and temperature sensor to calculate the current air density.
[0010] While several features exhibited within these references are incorporated into this invention, alone and in combination with other elements, the present invention is sufficiently different so as to make it distinguishable over the prior art.
[0011] Accordingly, several objects and advantages or my invention are:
[0012] (a) to provide increased effective range in a compact form factor by utilizing the large visual sight path objective aperture to collect a greater amount of reflected laser light;
[0013] (b) to provide improved accuracy for uphill and downhill operation by incorporating laser range finding technology and inclination angle measurement to calculate the horizontal distance to the selected target;
[0014] (c) to provide improved accuracy by calculating the compensated aim point with user entered muzzle velocity;
[0015] (d) to provide improved accuracy by calculating the compensated aim point with user entered ballistic coefficient;
[0016] (e) to provide improved accuracy by calculating the compensated aim point using a barometric pressure and temperature sensor to determine the air density and resulting drag;
[0017] (f) to provide improved accuracy by automatically adjusting the elevation reticle to indicate the compensated aiming point;
[0018] (g) to provide an improved targeting device that can be used in a manner identical to that of a conventional riflescope in the event of battery failure or if so desired;
[0019] Further objects and advantages are to provide an improved targeting device that is lightweight, compact and easy to use. Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.
[0020] In accordance with the present invention a trajectory compensating riflescope that is comprised of an otherwise traditional riflescope that incorporates measurements to determine the horizontal target distance and air density. In addition, a user interface is provided to enter firearm and ammunition specific parameters such as muzzle velocity and ballistic coefficient. These measurements and parameters are applied to calculate and automatically adjust the elevation reticle to a compensated aim point.
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[0094] A preferred embodiment of the trajectory compensating riflescope, hereinafter riflescope
[0095] As shown in
[0096] As shown in
[0097] As shown in
[0098] As shown in
[0099] As shown in
[0100] As shown in
[0101] As shown in
[0102] As shown in
[0103] As shown in
[0104] As shown in
[0105] Operation—
[0106] Once the trajectory compensating riflescope is mounted to the firearm the user must perform a zeroing calibration operation, this procedure is identical to that used for conventional riflescopes. The manual elevation adjustment knob
[0107] When the electronics are not enabled, the manner of using the automatic trajectory compensating targeting riflescope is identical to that for riflescopes in present use. The operation as a normal riflescope is necessary to ensure useful operation in the event of battery failure.
[0108] To make use of the automatic compensation mode, the user must toggle the power switch
[0109] The user then views the intended target through eyepiece
[0110] The laser light is then reflected off the target, objective lens
[0111] As shown in
[0112] Lastly, the micro-controller signals the stepper motor driver circuit
[0113] Advantages
[0114] From the descriptions above, a number of advantages of my trajectory compensating riflescope become evident:
[0115] (a) The integration of the laser receiver system into the viewing optics reduces the overall form factor and weight. In addition, using the large aperture of the objective lens to collect the reflected laser light provides for lower light level detection and thus greater effective range.
[0116] (b) Incorporating the user settable muzzle velocity value provides a critical parameter in calculating the time over which the projectile will be influenced by gravity thus resulting in a more accurate determination of the final impact point.
[0117] (c) Incorporating the user settable ballistic coefficient value provides a critical parameter in calculating the time over which the projectile will be influenced by gravity thus resulting in a more accurate determination of the final impact point. This value indicates how well a specific bullet can overcome air resistance and maintain flight velocity.
[0118] (d) Incorporating the measurement of the barometric pressure and temperature values provides a critical parameter in calculating the time over which the projectile will be influenced by gravity thus resulting in a more accurate determination of the final impact point. These two values are applied to the ideal gas law equation to calculate the actual air density thus factoring in the air resistance that will affect the flight velocity.
[0119] (e) Gravity only affects the projectile over the horizontal distance traveled. Implementing both the line of sight laser distance measurement and inclination angle provides a method to determine the horizontal distance when shooting uphill or downhill.
[0120] (f) Indicating the compensated aim point by automatically adjusting the elevation reticle eliminates the need to guess at the adjusted aim point.
[0121] (g) Providing operation as a conventional riflescope ensures useful functionality in the event of battery failure.
[0122] (h) The manual windage and elevation adjustments provide a mechanism to calibrate the zero aim point at a given target distance thus compensating for variability in mounting position on the firearm.
[0123] Conclusion, Ramifications, and Scope
[0124] Thus the reader will see that the trajectory compensating riflescope of the invention provides a compact, lightweight, yet economical device that is highly accurate and easy to use.
[0125] While my above description contains many specificities, these should not be construed as limiting the scope of the invention, but rather as exemplification of one preferred embodiment thereof. Many other variations are possible. For example, the laser transmitter could also be integrated into the visual sight path. The range finding apparatus could be modular and not integrated into the visual sight path. The laser distance measurement method could implement a phase shift method instead of pulsed time of flight method. The material choices could vary for each of the individual components. The use of a conventional riflescope could be eliminated to change the overall device form factor. The accuracy could be sacrificed by eliminating the barometric pressure, temperature, and inclination angle sensors to reduce overall cost. The user interface could be simplified or eliminated to reduce cost. The user specific parameters such as muzzle velocity and ballistic coefficient could be entered using a computer interface or preset at the factory. The user input could be simplified by using a lookup table to identify the muzzle velocity and ballistic coefficient values for entered firearm and ammunition types. Although not implemented due to the additional cost, an anemometer could be added to measure the head wind and compensate for the additional drag thus providing greater accuracy. In addition, an anemometer that measures and compensates for crosswind could be added and used to automatically adjust the windage reticle. The method of indicating the compensated aim point could consist of a secondary elevation and/or windage reticle.
[0126] Accordingly, the scope of the invention should be determined not by the embodiment(s) illustrated, but by the appended claims and their legal equivalents.