WO2014167276A1

WO2014167276A1 - Apparatus for use with a telescopic sight

Info

Publication number: WO2014167276A1
Application number: PCT/GB2014/000145
Authority: WO
Inventors: Derek Kenneth ROSE; David Edward Rose
Original assignee: Rowan Engineering Limited
Priority date: 2013-04-11
Filing date: 2014-04-11
Publication date: 2014-10-16
Also published as: GB2512915A; GB201306605D0

Abstract

Apparatus (101) for use with a telescopic sight (102) of a gun, the telescopic sight (102) comprising an adjustable lens for providing parallax adjustment. The apparatus (101) comprises an encoder (105) for detecting the position of the adjustable lens within the telescopic sight, a data processing device (106) configured to receive input data derived from the encoder (105) representative of the position of the adjustable lens, and having access to reference data, and a display device (107) configured to receive an input from the data processing device (106) and to generate a display output in response. The data processing device (106) is configured to compare input data derived from the encoder (105) with the reference data to determine a range value indicating the range to a target in focus and to supply an input to the display device (107) in response. The apparatus (101) may be provided for retrofitting to a telescopic sight (102), or for inclusion in the original manufacture of a telescopic sight (102).

Description

APPARATUS FOR USE WITH A TELESCOPIC SIGHT

Field of the Invention

The present invention relates to apparatus for use with a telescopic sight of a gun.

Background of the Invention

Field Target (FT) shooting is an outdoor air gun discipline in which air rifles are used.

A typical target comprises an upright metal faceplate, which may have a simple geometrical shape or the shape of a small game animal, in which a circular hit zone of a predetermined size is defined (typically 25mm or 40mm). To aid visibility, the hit zone is often displayed in a different colour to the faceplate. The faceplate is hinged to a base, and is arranged to fall backwards in response to a strike within the hit zone. The target is provided with a pull cord to enable the knocked down faceplate to be reset into the vertical position from a distance.

A typical target course comprises a plurality of targets, grouped into lanes. The targets are located at different distances within a predetermined range of distances from a firing line (typically 8 yards/7.32m to 55 yards/50.29m). The targets may be positioned on the ground, for example on the flat or a slope, or may be elevated above ground, for example up in a tree.

In competition, the range of each target is not provided to the marksman. The marksman is allowed only a single shot at each target. A time restriction may be imposed for each lane. In addition, the marksman may be required to adopt a particular designated to a lane, for example a standing position or a seated or kneeling position.

When preparing to fire at a target, the marksman must consider a variety of factors, including: the range of the target, the inclination angle of the target relative to horizontal range, elevation compensation for the trajectory of the projectile over the range to the target, temperature compensation and wind compensation.

Similar considerations exist in field hunting and other forms of rifle shooting. Summary of the Invention

According to a first aspect, there is provided apparatus for use with a telescopic sight of a gun, the telescopic sight comprising an adjustable lens for providing parallax adjustment, said apparatus comprising: position sensor means adapted to detect the position of said adjustable lens, a data processing device configured to receive input data derived from said position sensor means representative of the position of said adjustable lens, and having access to reference data, and a display device configured to receive an input from said data processing device and to generate a display output in response; said data processing device configured to compare input data derived from said position sensor means with said reference data to determine a range value indicating the range to a target in focus and to supply an input to said display device in response.

In one embodiment, said adjustable lens is a focus lens, the position of said focus lens is adjustable by rotating a rotatable element, and said position sensor means is configured to detect the angular position of said rotatable element. In an example, said rotatable element is a rotatable shaft extending from one side of said telescopic sight. In an alternative example, said rotatable element is a rotatable wheel mounted to a rotatable shaft extending from one side of said telescopic sight.

In an alternative embodiment, said adjustable lens is an objective lens, the position of said objective lens is adjustable by rotating a rotatable element, and said position sensor means is configured to detect the angular position of said rotatable element. In an example, said rotatable element is a rotatable ring on the objective bell of said telescopic sight.

The apparatus may further comprise one or more of: a temperature sensor, an inclination sensor, a barrel resonance sensor, a projectile velocity sensor, a projectile azimuth sensor.

The apparatus may be provided for retrofitting to a telescopic sight, or for inclusion in the original manufacture of a telescopic sight.

The apparatus may be provided for use with a telescopic sight of an air gun. In an embodiment, the apparatus is provided for use with a telescopic sight of an air rifle.

According to a second aspect, there is provided a telescopic sight of a gun, comprising apparatus as described the first aspect above. Brief Description of the Drawings

For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which:

Figure A shows a prior art rifle scope with rotatable parallax adjustment side wheel;

Figure B is a schematic of the lens assembly arrangement of the prior art rifle scope with rotatable parallax adjustment side wheel of Figure A;

Figure 1 shows apparatus for use with a rifle scope having an adjustable lens for providing parallax adjustment;

Figure 2 shows the apparatus of Figure 1 in further detail;

Figure 3 illustrates steps in a range calibration routine;

Figure 4 illustrates steps in a temperature calibration routine;

Figure 5 illustrates a step in an elevation calibration routine;

Figure 6 shows an example display output;

Figure 7 shows a gun barrel attachment of the apparatus;

Figure 8 shows further features of the apparatus with gun barrel attachment;

Figure 9 shows further example display outputs;

Figure 10 is a schematic of an example user menu layout,

Figure 11 is a schematic of an example graphical display of data uploaded from the apparatus to a further data processing device;

Figure 12 shows a plan view of the apparatus mounted to a rifle scope having a side parallax adjustment knob;

Figure 13 shows a plan view of the apparatus mounted to a rifle scope having a parallax adjustment ring on the objective bell;

Figure 14 shows a display feature of the apparatus;

Figure 15 is a schematic of a lens assembly arrangement for providing the display feature of the apparatus illustrated in Figure 14; Figure 16 is a schematic diagram illustrating ballistic trajectories of shots taken at a range of angles of elevation and associated bullet drops; and

Figure 17 is a graph of bullet drop against slant range to target for shots taken at horizontal, vertical and intermediate angles of elevation.

Detailed Description of the Embodiments

There will now be described by way of example a specific mode contemplated by the inventor(s). In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures are not described in detail so as not to unnecessarily obscure the description.

Figure A

Figure A shows a prior art rifle scope 1. The rifle scope 1 enables a marksman to see longer distances more clearly than with the naked eye. The rifle scope 1 has an eye piece 2 with an ocular lens, through which a marksman can see a reticule 3 and also a target 4 in the field of view. The rifle scope will typically have a reticule focusing system to enable the marksman to move the ocular lens forwards or backwards to bring the reticule into sharp focus. At the other end of the rifle scope 1 is an objective bell 5 with an objective lens. The rifle scope 1 also has an adjustable magnification ring 6 to allow the marksman to zoom in and zoom out of a target 4 in the field of view.

The rifle scope 1 has a rotatable parallax adjustment knob 7. Parallax occurs when the optical plane of the image of a target is not coplanar with the optical plane of the image of the reticule. As a result of the offset between the two optical planes, the reticule can appear to move relative to the target when the marksman moves their eye around the centre of the reticule. This parallax error can result in a shift in the point of impact from firing. The parallax adjustment of a telescopic sight enables the marksman to eliminate optical error at different distances, by enabling the optical system to be adjusted to show the image of the target and the image of the reticule in the same optical plane. Field Target (FT) competitors typically use a high-magnification rifle scope (for example in the range 35x to 55x) with a rotatable parallax adjustment knob. In competition, the marksman is not informed of the range of a target from the firing line and is prohibited from using any direct range-finding device. A marksman may estimate the range of a target by eye; however, it is has been found that the rotatable parallax adjustment knob of a high-magnification scope can provide a way for a marksman to find the range of a target.

At high-magnifications, the depth of field of a telescopic sight is shallow and therefore a target will be out of focus unless the parallax control is adjusted precisely. When the parallax error is removed, the scope is at optimal focus. Once a target of a known range is in proper focus, the angular position of the rotatable parallax adjustment knob can be marked to visually associate the position of the rotatable parallax adjustment element with the known distance of the target, for future reference. This enables the marksman to focus in on targets of different known distances and apply corresponding markers to the rotatable parallax adjustment knob to, in effect, calibrate the rotatable parallax adjustment knob as a range finder. Thus, when a target of unknown distance is encountered, the marksman can bring the target into proper focus and read the marker from the rotatable parallax adjustment knob to find the range.

The rotatable parallax adjustment knob is too small to be marked with many different ranges. As shown in this Figure, the rifle scope 1 is provided with a side wheel 8 mounted to the rotatable parallax adjustment knob 7. The larger diameter of the side wheel 8 provides more space for markers, such as range marker 9, to be applied, and is easier for the marksman to rotate and read from when in use. The larger diameter of the side wheel 8 thus serves to increase the accuracy and resolution of the range finding markers. The rifle scope 1 has a side wheel reference marker 10 to facilitate reading a value.

A problem exists in that the distance between fixed increment range markers is not linear, and the distance between adjacent range markers decreases as the range magnitude increases. For example, in this Figure, the side wheel 8 is marked in increments of 5 yards/4.75m, and it can be seen that the distance between the range markers for 20 yards and 25 yards is greater than the distance between the range markers for 40 yards and 45 yards. A first aspect of the problem is the undesirable bunching up of range marks at higher ranges. A second aspect of the problem is that judging an intermediate range between successive range markers is not straightforward.

It is important for the marksman to know the range of the target in order to then determine and incorporate compensation values into the aim preparation.

Once the range is determined, the marksman will typically wish to apply an elevation compensation adjustment for the projectile drop of the trajectory of the projectile over the range to the target. The rifle scope 1 has a rotatable elevation turret 11 that provides vertical adjustment of the erector tube that carries the reticule 3 within the main tube of the scope. The rotatable elevation turret 11 is provided with markers, such as marker 12. The rifle scope 1 is provided with an elevation turret reference marker 13 to facilitate reading a value. The elevation adjustment is typically effected in fixed intervals, with each interval representing, for example, a ¼ minute of an angle. The markers may indicate distance or graduations (known as 'clicks').

The marksman will typically wish to apply a windage compensation adjustment for the effect of wind on the projectile over the range to the target. The rifle scope 1 has a rotatable windage turret 14 that provides horizontal adjustment of the erector tube that carries the reticule 3 within the main tube of the scope.

The marksman may also wish to apply a temperature compensation adjustment, for the effect on the optical system of a change in temperature from the temperature at which the side wheel 8 of the rifle scope 1 was calibrated. A change in temperature from the temperature at which the side wheel 8 of the rifle scope 1 was calibrated will result in the expansion or contraction of the optical system, which will introduce a change in the focus point for a particular range. A marksman may therefore use a thermometer with the scope, to enable temperature compensation adjustments to be made.

In addition, a target may be above or below horizontal. The marksman may therefore estimate the angle of inclination by eye or use a pendulum protractor 16 or other device to enable a cosine (vertical angle) compensation adjustment to be made.

Another factor for the marksman to consider is cant error, which is caused by the marksman not holding the rifle bore axis and the rifle scope axis in a vertical plane, or by not maintaining the same canted position between shots. The marksman may therefore use a bubble spirit level 17 or other device to endeavour to eliminate any unwanted tilt. Yet further factors to be considered by the marksman include projectile velocity, which can change between shots due to a change in power applied to successively fired projectiles, hold, and barrel tuning. The projectile velocity is a factor to consider in determining the effect of gravity on the projectile over the range to the target. The degree of hold by the marksman can affect the amount of recoil experienced, which can affect the point of impact. Tuning the barrel to minimise vibration can also affect the accuracy of the shot. Further considerations include the actual equipment used and apparatus set up.

Certain compensation values may be determined by a marksman by mental calculation or by reference to a compensation charts. It is to be appreciated that the marksman has many different parameters to consider before finally taking aim and firing, and that since compensation values are interrelated, any error in calculating one or more of the parameters can have a compound effect in the final compensation value and actual point of impact.

Figure B

Figure B is a schematic of the lens assembly arrangement 30 of the prior art rifle scope 1. In the lens assembly 30, a focus lens 31 is located between an ocular lens 32 and an objective lens 33. The relative distance between the focus lens 31 and the objective lens 33 is adjustable, for providing parallax adjustment. In addition, erector lenses 34, 35 are located between the ocular lens 32 and the focus lens 31. The relative distance between the erector lenses 34, 35 and the objective lens 33 is adjustable, for providing magnification adjustment.

In the lens assembly 30 of the prior art rifle scope 1 , the focus lens 31 is adjustable and the objective lens 33 is fixed. The focus lens 31 is movable, in a direction indicated by arrow 36, towards and away from the objective lens 33. The position of the focus lens 31 relative to the objective lens 33 is therefore adjustable.

In the shown arrangement, the rotatable parallax adjustment knob 7 of the rifle scope 1 is mounted to a rotatable shaft 37, which is operably connected to the focus lens 31 by a linkage 38. The linear position of the focus lens 31 is adjustable by rotating the rotatable parallax adjustment knob 7. A change in the rotational position of the rotatable parallax adjustment knob 7 translates to a displacement of the focus lens 31 in a direction indicated by arrow 36. The position of the rotatable parallax adjustment knob 7 thus indicates the linear position of the focus lens 31.

Range markers can thus be applied to the rotatable parallax adjustment knob 7 to visually associate the relative distance between the focus lens 31 and the objective lens 33 with a known distance of a target in proper focus.

Figure 1

Apparatus for use with a telescopic sight of a gun, the telescopic sight comprising an adjustable lens for providing parallax adjustment will now be described. The apparatus comprises an encoder for detecting the position of said adjustable lens, a data processing device configured to receive input data derived from the encoder representative of the position of the adjustable lens, and having access to reference data, and a display device configured to receive an input from the data processing device and to generate a display output in response; the data processing device configured to compare input data derived from the encoder with the reference data to determine a range value indicating the range to a target in focus and to supply an input to said display device in response.

The apparatus provides an electronic range-finder for finding a range from the position of the adjustable lens for providing parallax adjustment of a telescopic sight. The apparatus may be used with a rifle scope comprising an adjustable focus lens for providing parallax adjustment or with a rifle scope comprising an adjustable objective lens for providing parallax adjustment.

Figure 1 shows apparatus 101 for use with a rifle scope 102 comprising an adjustable focus lens for providing parallax adjustment. The position of the focus lens of the rifle scope 102 is adjustable by rotating a rotatable shaft 103 extending from one side of the rifle scope 102. In the shown arrangement, the rotatable shaft 103 extends from the left side of the rifle scope 102, but may alternatively extend from the right side of the rifle scope 102. In the arrangement shown in Figure 1 , a rotatable wheel 104 is mounted to the rotatable shaft 103 of the rifle scope 102.

Apparatus 101 comprises an encoder 105 as a position sensor for detecting the position of the adjustable focus lens of rifle scope 102. The position of the adjustable lens may be detected directly or indirectly. In this illustrated embodiment, the encoder 105 is configured to detect the angular position of the rotatable wheel 104. It is to be appreciated that the angular position of the rotatable wheel 104 is related to the angular position of the rotatable shaft 103, which in turn is related to the position of the adjustable focus lens relative to the objective lens of the rifle scope 102.

Apparatus 101 further comprises a data processing device 106 and a display device 107. The display device 107 is configured to receive an input from the data processing device 106 and to generate a display output in response.

In this embodiment, the data processing device 106 and display device 107 are housed within a housing 108 mounted upon the rifle scope 102. The housing 108 is shown located on the top of the rifle scope 102, but may be located at any position for convenient viewing by a marksman. In an example, the housing 108 is mounted on the opposite side of the rifle scope 102 to the rotatable wheel 104.

In this embodiment, the encoder 105 comprises an encoder track 109 carried on the rotatable wheel 104 and an encoder track position sensor 110.

It is to be understood that the encoder may take any suitable form. For example, the encoder may comprise an optical sensor, a magnetic sensor, a resistance sensor, a capacitance sensor, a Hall effect sensor or analogue position sensor. The encoder may be configured to sense a rotational position or a linear position.

Apparatus 101 may be provided for retrofitting to a telescopic sight but may alternatively be provided for incorporation into a telescopic sight during original manufacture.

Regarding example retrofit arrangements, an encoder track may be provided for fitting to a rotatable wheel, or a rotatable wheel with a fitted encoder track may be provided for mounting to a rotatable element for rotating the adjustable lens, and an encoder track position sensor, data processing device and display device may be provided therewith for appropriate mounting to the rifle scope. In an application, apparatus 101 is provided for mounting to a standard 25mm telescopic sight or a standard 30mm telescopic sight. In an application apparatus 101 is provided for mounting to a telescopic sight having a larger diameter with the use of an appropriate mounting adaptor. Regarding example original manufacture arrangements, the encoder may be operably connected to a rotatable element for rotating the adjustable lens, or the encoder may be operably connected to the focus lens assembly. The encoder may therefore comprise any suitable arrangement that provides sufficient measurement resolution and is appropriately sized for fitting to or fitting in a telescopic sight.

Figure 2

Figure 2 shows apparatus 101 in further detail.

The data processing device 106 comprises a programmable circuit board (PCB) 201 provided with a microcontroller 202 having a memory. The data processing device 106 is configured to be battery powered. The display device 107 is electrically connected to the microcontroller 202.

The data processing device 106 is configured to receive input data derived from the encoder 105 representative of the position of the adjustable lens, and has access to reference data. The data processing device 106 is configured to compare input data derived from the encoder 105 with the reference data to determine a range value indicating the range to a target in focus and to supply an input to the display device in response. Apparatus 101 provides a function of displaying a range value to a marksman preparing to take a shot at a target.

In this embodiment, the encoder track position sensor 110 is electrically connected to the microcontroller 202.

Apparatus 101 further comprises a temperature sensor 203, and the data processing device 106 is configured to receive input data derived from the temperature sensor 203. The data processing device 106 is configured to determine a temperature value indicating a sensed temperature and to supply an input to the display device 107 in response. Preferably, the data processing device 106 is configured to process received input data derived from the temperature sensor 203 to determine a temperature adjusted range value and to supply an input to the display device 107 in response. The temperature sensor 203 is electrically connected to the microcontroller 202. Apparatus 101 provides a function of displaying a temperature value and/or a temperature compensated range value to a marksman preparing to take a shot at a target. Apparatus 101 also comprises an inclination sensor 204, and the data processing device 106 is configured to receive input data derived from the inclination sensor 204. The data processing device 106 is configured to determine an inclination value indicating an angle of inclination and to supply an input to said display device 107 in response. The inclination sensor 204 is electrically connected to the microcontroller 202. The inclination sensor may take any suitable form. For example, the inclination sensor may comprise at least one accelerometer and a gyroscope, or an inclinometer. In this embodiment, the inclination sensor 204 comprises a 3-axis gyroscope and a 3-axis accelerometer. The inclination sensor 204 is configured to sense vertical inclination from horizontal range. Preferably, the data processing device 106 is configured to process received input data derived from the inclination sensor 204 to determine a cosine compensation value and to supply an input to said display device in response. Apparatus 101 provides a function of displaying an inclination value and/or an elevation compensation value and/or an inclination compensated range value to a marksman preparing to take a shot at a target.

Optionally, and in this embodiment, the inclination sensor 204 is configured to sense roll from vertical alignment. Preferably, the data processing device 106 is configured to process received input data derived from the inclination sensor 204 to determine a canted position value and to supply an input to said display device in response. Apparatus 101 thus also provides a function of displaying a canted position value to a marksman preparing to take a shot at a target.

Optionally, and in this embodiment, the inclination sensor 204 is configured to sense a property of recoil. In this embodiment, recoil is sensed by an accelerometer. Optionally, and in this embodiment also, the data processing device 106 is programmed to perform a timer routine and to supply an input to said display device in response.

Optionally, apparatus 101 may comprise a projectile azimuth sensor. The data processing device 106 is configured to receive input data derived from the projectile azimuth sensor, which may take any suitable form. For example, the projectile azimuth sensor may comprise a magnetometer sensor or digital compass. In this embodiment, the projectile azimuth sensor comprises a digital compass integrated circuit incorporated into the programmable circuit board (PCB) 201 of the data processing device 106.

The housing 108 defines a battery compartment 205 for containing a battery in electrical connection with the programmable circuit board (PCB) 201. In this embodiment, a dedicated battery voltage regulator is provided that functions to lower or increase the battery voltage to a suitable magnitude for the programmable circuit board (PCB) 201 and other devices as appropriate.

The housing 108 defines a display aperture 206 and a plurality of menu button apertures 207. The programmable circuit board (PCB) 201 carries the display device

107 and a corresponding plurality of menu buttons 208. The menu buttons 208 may include a power on/off button 209.

Apparatus 101 also comprises a mounting bracket 210, for mounting the housing

108 to a rifle scope.

Figure 3

Figure 3 shows steps in a range calibration routine 301.

At step 302, the marksman views a target of known range and adjusts the position of the adjustable lens for providing parallax adjustment of the telescopic sight until the target is in proper focus. A reading is then taken to associate the position of the adjustable lens for providing parallax adjustment of the telescopic sight with the known range of the target, and this is then stored by the data processing device as an item of reference data.

At step 303, the marksman views a target of a different known range and adjusts the position of the adjustable lens for providing parallax adjustment of the telescopic sight until the target is in proper focus. A reading is then taken to associate the position of the adjustable lens for providing parallax adjustment of the telescopic sight with the known range of the target, and this is then stored by the data processing device as a further item of reference data.

Step 303 is then repeated a suitable number of times to calibrate the rotatable element at fixed intervals across a range of distances.

The data processing device is programmed to store the reference data items obtained during the range calibration routine. The data processing device is also programmed to perform an interpolation algorithm to provide a range value of a range falling between fixed intervals.

The apparatus described herein advantageously overcomes the requirement for physical markers to be shown on a range-finding wheel, since an associated range is displayed by the display device during use. This is particularly beneficial when the marksman wishes to perform recalibration of the range-finding wheel, since it also overcomes the requirement to reposition the markers. In addition, the range-finding wheel can be reduced in size, facilitating storage within a gun bag and reducing spindle strain on the rotatable element for adjusting the position of the adjustable lens for providing parallax adjustment of the rifle scope. The apparatus described herein further advantageously provides a range value for an intermediate range between successive fixed intervals.

Figure 4

Figure 4 shows steps in a temperature calibration routine 401.

At step 402, the marksman views a target of known range and at a known temperature and adjusts the position of the adjustable lens for providing parallax adjustment of the telescopic sight until the target is in proper focus. A reading is then taken to associate the position of the adjustable lens for providing parallax adjustment of the telescopic sight with the known range of the target for the known temperature, and this is then stored by the data processing device as an item of reference data.

At step 403, the marksman views a target of the same known range and at a different temperature and adjusts the position of the adjustable lens for providing parallax adjustment of the telescopic sight until the target is in proper focus. A reading is then taken to associate the position of the adjustable lens for providing parallax adjustment of the telescopic sight with the known range of the target for the known temperature, and this is then stored by the data processing device as a further item of reference data.

Step 403 is then repeated a suitable number of times to calibrate the rotatable element at fixed intervals across a range of distances.

The data processing device is programmed to store the reference data items obtained during the temperature calibration routine. The data processing device is also programmed to perform a temperature compensation algorithm to determine a temperature adjusted range value. Fiqure 5

Figure 5 shows a step in an elevation calibration routine 501.

At step 501 the magnitude of the rotational graduations of the elevation turret of the rifle scope is associated with a known angle of inclination.

The data processing device is programmed to perform an elevation compensation algorithm to determine an effective horizontal range from data derived from the encoder (indicating slant range) and data derived from the inclination sensor (indicating elevation). In an embodiment, a calculation of slant range (R_s) multiplied by the cosine of the elevation angle (cos (a)) is performed to provide an equivalent horizontal range

The data processing device may further be programmed to store input data items derived from empirical testing by a user, which may be processed in combination with algorithm derived data. In this embodiment, the data processing device is programmed to store user input data relating to an offset for a particular range and angle combination, for example to compensate for the height of the rifle scope relative to the gun barrel.

Figure 6

An example display output of the display device 107 is shown in Figure 6. Display 601 is a shoot preparation data display.

A range value is displayed in region 602, in the form of a numerical value. A cosine compensation value is displayed in region 603, in the form of a numerical value indicating the number of clicks to turn the elevation turret by. A cosine compensation value is also displayed in region 604, in the form of a graphical display of a reticule position. One or both of the cosine compensation values as displayed in regions 603 and 604 may be displayed. It is to be appreciated that a range adjusted value, incorporating cosine compensation will be displayed in region 602. A change in a cosine compensation value will therefore alter the displayed range value.

A sensed elevation angle, from which the cosine compensation is determined, is displayed in region 605. A sensed temperature, from which any temperature compensation is determined, is displayed in region 606. A canted position value is displayed in region 607, in the form of a graphical bubble spirit level. A time value is displayed in region 608. The displayed time indicates the time remaining for the marksman to fire at a target. The timer function will typically take the form a countdown timer.

Numerical values displayed by the display unit 107 may be accompanied by units of measurement.

Figure 7

Further optional features of apparatus 101 are shown in Figure 7. The apparatus 101 comprises a gun barrel attachment 701.

Apparatus 101 comprises a barrel resonance sensor 702. The data processing device 106 is configured to receive input data derived from the barrel resonance sensor 702. The barrel resonance sensor may take any suitable form. For example, the barrel resonance sensor may comprise an accelerometer, or an accelerometer gyroscope, and a pair of sensors to detect exiting of the projectile from the gun barrel. The barrel resonance sensor 702 senses vibration of the barrel at the moment the projectile exits the barrel. Apparatus 101 provides a function of displaying a barrel resonance waveform.

Apparatus 101 further comprises a projectile velocity sensor 703. The data processing device 106 is configured to receive input data derived from the projectile velocity sensor 703. The projectile velocity sensor may take any suitable form. For example, the projectile velocity sensor may comprise a second pair of sensors, spaced apart from the pair of sensors to detect exiting of the projectile from the gun barrel of the barrel resonance sensor, arranged to provide a chronograph function. Apparatus 101 provides a function of displaying a projectile velocity.

Figure 8

Figure 8 shows apparatus 101 comprising gun barrel attachment 701 in further detail.

The gun barrel attachment 701 comprises a programmable circuit board (PCB)

801 provided with a microcontroller 802 having a memory. The rifle barrel attachment 701 is configured to be battery powered. A battery 803 is provided on the programmable circuit board (PCB) 801.

A plurality of timing gate sensors 804 are provided and are electrically connected to the microcontroller 802. The accelerometer 805, or accelerometer gyroscope, of the barrel resonance sensor is also electrically connected to the microcontroller 802.

Apparatus 101 comprises a first transceiver unit 806 on the programmable circuit board (PCB) 201 of the data processing device 106 and a second transceiver unit 807 on the programmable circuit board (PCB) 801 of the gun barrel attachment 701. This allows control signals to be transmitted from the data processing device 106 to the gun barrel attachment 701 and for data to be transmitted from the gun barrel attachment 701 to the data processing device 106.

The transceiver unit 806 on the programmable circuit board (PCB) 201 of the data processing device 106 also allows stored data to be transmitted to another data processing device, such as a desk top computer, mobile telephone or tablet. In an embodiment, the apparatus is provided with a slot for a memory card.

Optionally, apparatus 101 may comprise a projectile azimuth sensor. The data processing device 106 is configured to receive input data derived from the projectile azimuth sensor. The projectile azimuth sensor may take any suitable form. For example, the projectile azimuth sensor may comprise a magnetometer sensor or digital compass. In an embodiment, the projectile azimuth sensor is provided on the programmable circuit board (PCB) 201 of the data processing device 106.

Figure 9

Figure 9 shows further example display outputs of the display device 107.

Display 901 is a projectile velocity data display. A numerical value is displayed in region 902, indicating the velocity of the last shot. Optionally, if the projectile velocity for a number of successive shots is recorded, a numerical value is displayed in region 903, indicating the average projectile exit velocity over a sequence of shots and/or a graph is displayed in region 904 indicating the velocity of each of a sequence of shots. The display may also display a shot counter, indicating the number of shots taken since the function was reset. Display 905 is a barrel resonance measurement data display. A graph is shown in region 906, indicating the barrel resonance waveform. This facilitates tuning of the barrel by the marksman, to improve shooting accuracy, which is achieved by adjusting the position of a tuning weight or weights forwards or rearwards along the barrel. The display of the barrel resonance waveform advantageously allows the marksman to tune the barrel without requiring a test range to be set up.

Display 907 is a steady shot data display. A graph is shown in region 908, indicating movement of the rifle in the X and Y directions, and showing the X and Y positions at the point 909 when the shot was fired. A graph is shown in region 910 indicating a property of recoil in the Z direction. This provides an indication of the reaction of the rifle to the degree of hold or grip by the marksman.

Figure 10

Figure 10 is a schematic of an example user menu layout 1001. Upon power up, the display device shows a start screen 1002, from which a shoot screen 1003, set-up screen 1004, shot history data screen 1005 and data link screen 1006 are accessible. Further screens may be accessible from a selected screen. For example, an options screen 1007 and a calibration screen 1008 are accessible from the set-up screen 1004.

The menu may allow any one or more of the following functions to be accessed by the user: display (shoot preparation data, projectile velocity data, barrel resonance measurement data, steady shot data); shot timer (time, reset), shot counter (reset), chronograph (on/off); projectile weight input; system parameters (units of measurement, auto off time delay, save data to memory, data buffer size, power level warning, screen brightness); calibration functions and parameter input (rotatable wheel; temperature sensor; inclination sensor; projectile velocity sensor; barrel resonance sensor); data link (connect to selected device).

Figure 11

Data from apparatus 101 may be uploaded to a further data processing device, such as computer 1101. The uploaded data may then be displayed in a tabular form, as shown at 1102, or in a graphical form, as shown at 1103. The uploaded data can then be analysed by the marksman, or an appropriate computer program, for the purpose of obtaining performance indications useful to the marksman to understand and develop consistency of shot.

Figure 12

Figure 12 shows a plan view of apparatus 101 mounted to rifle scope 102 comprising an adjustable focus lens for providing parallax adjustment. The arrangement of the encoder track 109 and encoder track position sensor 110 are shown in this Figure, in which the encoder track 109 is mounted to the rotatable side wheel 104 and the encoder track position sensor 110 is mounted to extend from the main body of the rifle scope 102. As previously mentioned, the rotatable wheel 104 may be located to either side of the rifle scope 102, to suit the handedness of a particular marksman.

Figure 13

Figure 13 shows a plan view of apparatus 101 mounted to a rifle scope 1301 comprising an adjustable objective lens for providing parallax adjustment.

The position of the objective lens of the rifle scope 1301 is adjustable by rotating a rotatable ring 1302 on the objective bell 1303 of the rifle scope 1301. The arrangement of the encoder track 109 and encoder track position sensor 110 are shown in this Figure, in which the encoder track 109 is mounted to the rotatable ring 1302 and the encoder track position sensor 110 is mounted to extend from the main body of the rifle scope 1301.

Figure 14

As illustrated in Figure 14, apparatus 101 may comprise an optional display feature that allows a marksman to view data displayed within a region 1401 of the field of view. This advantageously allows a marksman to view data without having to move to view a display located externally of the field of view. As shown in this Figure, the data is overlaid on the image of the reticule 1402. Fiqure 15

Figure 15 is a schematic of a lens assembly arrangement 1501 for providing the display feature illustrated in Figure 14. In the lens assembly 1501 , a beam splitter 1502 is located between the ocular lens 1503 and the objective lens 1504. The beam splitter 1502 is mounted in the optical path to divert an image from a display screen 1505 towards the eye of the marksman. A separate lens assembly will typically be positioned between the beam splitter 1502 and the display screen 1505 to size the image from the display screen 1505 for display within the field of view. The display screen 1505 is effectively at the second focal plane and will be in focus with the data displayed over on the image of the reticule.

Hunting mode

As well as the FT (Field Target) mode of the apparatus, described above, further embodiments comprise a "Hunting" mode, which is either substitutable for the FT mode, or hardware or software facilities are provided to switch between the two. The Hunting mode is designed for use in field hunting, for example shooting vermin, for which the requirements are slightly different from those of the competition FT mode.

The Hunting mode will in particular utilise the electronic compass/azimuth sensor arrangement described above as an optional component for the data processing device 106, in the context of Figures 2 and 8. The Hunting mode will normally employ the reticule display 604 illustrated and described in Figure 6, producing an aim point displayed on the reticule 604, with the offset of the aim point being calculated on the basis of range, elevation, projectile velocity, etc., as in the FT mode. The Hunting mode will also employ a wind compensation function. The marksman may enter a known wind direction and wind strength (quantitatively or in semi-qualitative units such as the Beaufort scale) from weather forecasts or observations in the field, allowing an algorithm programmed into the data processing device 106 to calculate a windage offset. Alternatively, the marksman may enter his or her own wind offset values into the apparatus, based on a series of test shots in the field at known ranges and wind strengths. The apparatus will sense the direction in which a shot is being taken, measuring the azimuth using the electronic compass or alternatively a magnetic compass. The data processing device 106 will then calculate the wind vector, relative to the shot, using an inbuilt algorithm or by using the settings entered by the marksman. The apparatus then displays, on the reticule display 604, the aim point that the marksman must place over the target (or quarry), in order for the shot to hit the desired point of impact. (Corresponding data may be superimposed over the view through the scope using the display features illustrated in Figures 14 and 15, either to provide numerical data in region 1401 or to superimpose such an aim point on the image of the reticule 1402).

As the marksman alters the elevation, range and/or azimuth of the shot, these data and the aim point shown on the reticule 604, 1402 will update in real time.

The apparatus in Hunting mode is fully capable of interpolating in between user set values for any given range, elevation, temperature, wind values and so forth that fall within the "map" of data made available.

In the Hunting mode, range can still be conveniently set by the marksman using the FT technique, based on range determination from focus position and position of the respective lens. Alternatively, if the marksman prefers, the range may be set by visually estimating the range, by the use of known reference points in the field or shooting arena, by using conventional laser range finders or by any other external method. These externally-determined ranges may then conveniently be input to the apparatus of the present invention by turning the side parallax knob 7, side wheel 8, 104, ring 1302, lever, etc., until the apparatus displays this predetermined range to target on the relevant display 602, 1401 , together with a corrected aim point on the reticule display 604, 1402, calculated by the data-processing device 106 using this externally-derived range data. Backlash

One problem in the FT discipline is that the telescopic sights generally used in FT shooting tend to have a certain amount of "backlash". This means that the indicated range may be different, depending on which way the focus knob, wheel, etc., was turned when bringing the image into focus. It is therefore common practice for an FT shooter as far as possible to set the focus position by adjusting the lens in the same direction as the original calibration was undertaken. However, on occasions, a marksman will still inadvertently focus in the opposite direction (for example if needing to take a hurried shot), which would normally result in an inaccurate reading, the range being offset by the effect of the telescopic sight backlash. The apparatus of the present invention therefore preferably has a backlash compensation function. A known backlash value can be entered by the marksman, and the data processing apparatus 106 of the apparatus will be provided with an appropriate algorithm to calculate the effective focus position and hence the correct range, whenever the wheel has been moved in the wrong direction as the last step in the focusing process. Figures 16 and 17

In a preferred embodiment of the present invention, a more sophisticated algorithm is employed to compensate for elevated shots and the different effects of bullet drop under gravity at different shot elevation. As described above, the compensation can be based on the co-sine rule, otherwise known as the Rifleman's Rule. This calculation provides a reasonable approximation to actual trajectories, but is insufficiently accurate at close ranges or for shots taken at high angles of elevation.

Figure 16 illustrates a series of shots taken at different angles of elevation, to illustrate this effect. Line 1600 represents a vertical axis. As line 1601 , it also represents the trajectory of a shot at 90° elevation, i.e. vertically upwards. Dashed line 161 1 represents the trajectory of a shot taken at an elevation of 65°, dashed line 1621 represents the trajectory of a shot taken at an elevation of 35°, and dashed line 1631 represents the trajectory of a shot taken at an elevation of 0° (i.e. with a horizontal barrel). In each case, the trajectory of the projectile has deviated significantly from a corresponding solid line 1612, 1622, 1632 representing a linear extension of the barrel centreline for the respective shot. The bullet drop 1623, 1633 represents the apparent offset of the projectile when it has arrived at the range of the target. As shown, the bullet drop is most usefully measured at right-angles to the respective barrel centreline. (It should be noted that in this respect it is the measured slant range to the target, determined by focusing the lens within the telescopic sight, that is important to the shooter; horizontal distances to the target and vertical measurements of bullet drop are not the most useful measures when calculations, adjustments and offsets are all being referred back to the line of sight directly between the scope and the target - except, of course, for the special case of a horizontal shot, when the horizontal range and the slant range are identical).

As can be seen, for a horizontal shot, the ballistic trajectory of the projectile is a close approximation to a parabolic curve. For vertical shots, the trajectory is vertically up and vertically down; there is no offset between the barrel centreline and the projectile trajectory, and hence (by the definition of bullet drop herein), bullet drop is zero for a vertical shot. For the shots taken at intermediate angles, the curve of the respective projectile trajectories 1611 , 1621 is intermediate between a true parabolic curve and a straight line. The apparatus of the present invention calculates the bullet drop for any given range and angle of elevation, together with a "click value". This is best illustrated by transforming the relevant data into an alternative set of coordinates as shown in Figure 17.

The "click value" as referred to in the description of Figure A above, refers to the number of fixed intervals by which the rotatable elevation turret 11 on the scope 1 must be rotated to provide the correct vertical offset (vertical in the reference frame of the scope and gun) to bring the projectile onto the desired target. As described above, this elevation adjustment using the turret 11 is typically effected in fixed intervals, with each interval representing, typically, a ¼ minute of an angle, the turret 11 being provided with markers to indicate either distance or graduations, which are conventionally referred to as "clicks".

In Figure 17, the vertical axis of the graph 1703 actually represents bullet drop, i.e. data corresponding to bullet drops 1623, 1633 from Figure 16. The horizontal axis of the graph 1702 corresponds to distance to target or the slant range, thus corresponding to the lengths of the lines of sight to the target/barrel centrelines 1612, 1622, 1632 in Figure 16. Thus, line 1713 corresponds to a vertical shot with no bullet drop, line 1733 corresponds to a horizontal shot with corresponding sizeable bullet drop YZ, and dashed line 1723 corresponds to a shot taken at an intermediate angle of elevation having a bullet drop YW, intermediate between those of the vertical and horizontal shots. Point 1724 represents the point of impact of the projectile at the measured slant range. The angle 1725 (also labelled Ό') is the angle subtended by the bullet drop YW at the slant range to the target. The computation performed by the data-processing device 106 is based on the range determined from the adjustable lens position, as discussed at length above, together with an inclination sensor reading to provide the angle of elevation of the barrel. The principles of the computation are as follows:

(a) bullet drop YZ at the respective target range is known

(b) factor A is calculated as 1 - (sine (90 - inclination angle in degrees))

(c) actual drop YW equals drop YZ multiplied by factor A

(d) the angle O subtended by bullet drop YW at the target range is

calculated

(e) A number of clicks N is calculated from the angle O, multiplied by 60 to convert from degrees to minutes, multiplied by the known number of clicks per Minute of Arc (MOA) for the particular telescopic sight elevation turret 11.

A suitable algorithm is as follows: float x1 ,y1 ,x2,y2,x3,y3,mm,cc,d,yz,a,A,B,C,theta,drop,denom;

d= (float)menu1 itemvalues[ENCODERMENU][3]/100; //distance

// X1 ,Y1 = Second zero dist and drop mm

// X2,Y2= End point of ballistic curve max distance and drop in

x1 =0;

y1 =0;

x2=systemparam[ELECOMPCURVEDIST1];

y2=systemparam[ELECOMPCURVEDROP1];

x3=systemparam[ELECOMPCURVEDIST2];

y3=systemparam[ELECOMPCURVEDROP2]; denom = (x1 - x2) * (x1 - x3) * (x2 - x3);

A = (x3 * (y2 - y1) + x2 * (y1 - y3) + x1 * (y3 - y2)) / denom;

B = (x3*x3 * (y1 - y2) + x2*x2 * (y3 - y1) + χΓχ1 * (y2 - y3)) / denom;

C = (x2 * x3 * (x2 - x3) * y1 + x3 * x1 * (x3 - x1) * y2 + x1 * x2 * (x1 - x2) * y3) / denom;

yz= A*(d*d) + B*d + C;

// total mm drop on the ballistic curve at current range.

a=1 -sin((float)abs(90-(menu1 itemvalues[ACCELMENU][1 ]))/(180/PI));

// compensation ratio due to angle

mm= yz*a;

// mm compensation factor Ά'

theta=atan(mm/(d*1000))*180/PI;

// calculate angle in degrees from drop in mm at range

cc=theta*60*(systemparam[CLICKSPERMOA]/systemparam[MOA]);

// convert degrees on to MOA

// cc= clicks compensation.

A calibrated click value was previously entered into the memory of the apparatus, and the number of clicks N provided at step (e) is subtracted from this previously entered value, to provide a final displayed compensated click value, displayed to the marksman so that he may then adjust the elevation turret 11 accordingly.

Following this procedure, the known geometry of the telescopic sight and gun will produce the correct offset of the barrel centreline so that, at the desired target slant range and angle of elevation, the bullet trajectory will intercept the target as desired. This will give much more reliable results than the Rifleman's Rule when shooting at close ranges or at high angles of elevation.

A similar calculation is made in Hunting mode, in which case the calculated elevation compensation value is used to compute the correct aim point offset for display on the reticule display 604, 1402.

Components of the apparatus described herein may be fabricated from any suitable material or combination of materials, and be fabricated using any suitable process or combination of processes.

It is to be appreciated that the apparatus described herein advantageously provides an electronic range-finding device for a telescopic sight having an adjustable lens for providing parallax adjustment, and provides further beneficial features.

Claims

Apparatus for use with a telescopic sight of a gun, the telescopic sight comprising an adjustable lens for providing parallax adjustment, said apparatus comprising: position sensor means configured to detect the position of said adjustable lens within said telescopic sight,

a data processing device configured to receive input data derived from said position sensor means representative of the position of said adjustable lens, and having access to reference data, and a display device configured to receive an input from said data processing device and to generate a display output in response;

said data processing device being configured to compare input data derived from said position sensor means with said reference data to determine a range value indicating the range to a target in focus and to supply an input to said display device in response.

Apparatus as claimed in claim 1 , wherein :

said adjustable lens is a focus lens,

the position of said focus lens within the telescopic sight is adjustable by rotating a rotatable element, and

said position sensor means is configured to detect the angular position of said rotatable element.

3. Apparatus as claimed in claim 2, wherein said rotatable element is a rotatable shaft extending from one side of said telescopic sight.

Apparatus as claimed in claim 2, wherein said rotatable element is a rotatable wheel mounted to a rotatable shaft extending from one side of said telescopic sight.

Apparatus as claimed in claim 1 , wherein :

said adjustable lens is an objective lens,

the position of said objective lens within the telescopic sight is adjustable by rotating a rotatable element, and

Apparatus as claimed in claim 5, wherein said rotatable element is a rotatable ring on the objective bell of said telescopic sight.

Apparatus as claimed in any one of the preceding claims, wherein said position sensor means comprises an encoder.

Apparatus as claimed in any one of the preceding claims, further comprising a temperature sensor, said data processing device being configured to receive input data derived from said temperature sensor.

Apparatus as claimed in any one of the preceding claims, wherein said data processing device is configured to determine a temperature value indicating a sensed temperature and to supply an input to said display device in response.

Apparatus as claimed in claim 8, wherein said data processing device is configured to process received input data derived from said temperature sensor to determine a temperature adjusted range value and to supply an input to said display device in response.

11. Apparatus as claimed in any one of the preceding claims, further comprising an inclination sensor, said data processing device being configured to receive input data derived from said inclination sensor.

Apparatus as claimed in claim 11, wherein said data processing device is configured to determine an inclination value indicating an angle of inclination and to supply an input to said display device in response.

Apparatus as claimed in claim 11 , wherein said inclination sensor is configured to sense vertical inclination from horizontal range.

Apparatus as claimed in claim 13, wherein said data processing device is configured to process received input data derived from said inclination sensor to determine at least one of: a cosine compensation value and an inclination compensated range value, and to supply an input to said display device in response.

Apparatus as claimed in any one of claims 11 to 14, wherein said inclination sensor is configured to sense tilt in the cant direction.

Apparatus as claimed in claim 15, wherein said data processing device is configured to process received input data derived from said inclination sensor to determine a canted position value and to supply an input to said display device in response.

Apparatus as claimed in any one of the preceding claims, wherein said data processing device is configured to perform a timer routine and to supply an input to said display device in response.

Apparatus as claimed in any one of the preceding claims, further comprising a barrel resonance sensor, said data processing device being configured to receive input data derived from said barrel resonance sensor.

19. Apparatus as claimed in any one of the preceding claims, further comprising a projectile velocity sensor, said data processing device being configured to receive input data derived from said projectile velocity sensor.

20. Apparatus as claimed in any one of the preceding claims, further comprising a projectile azimuth sensor, optionally comprising electronic compass means.

21. Apparatus as claimed in any one of the preceding claims, wherein said data processing device is configured to store data relating to at least one property of a shot.

22. Apparatus as claimed in claim 21, wherein said data processing device is configured to store data relating to said at least one property of each of a plurality of successive shots.

23. Apparatus as claimed in any one of the preceding claims, said apparatus being selectively switchable between a plurality of operating modes for alternative purposes, each said mode taking in different input data and/or producing different output results.

24. Apparatus as claimed in any one of the preceding claims, adapted to be retrofitted to said telescopic sight.

25. Apparatus as claimed in any one of the preceding claims, adapted to be included in said telescopic sight during original manufacture.

26. Apparatus as claimed in any one of the preceding claims, for use with a telescopic sight of an air gun.

27. Apparatus as claimed in claim 26, wherein said air gun is an air rifle.

28. A telescopic sight of a gun, comprising apparatus as claimed in any one of the preceding claims.