OPTICALLY TRACKED PROJECTILE

Abstract

A projectile, that can be tracked optically, which is coated with a fluorescent die or affixed with rearward facing retro-reflectors. Laser emitted radiation forms a cone of light that intersects and illuminates the ballistic path of the projectile. It is possible to manual measurement techniques, spotters or automated tracking of the illuminated projectile. The optically tracked projectile allows for the adjustment subsequent shots using a manual or automated optical tracking.

Claims

1. An ammunition projectile configured to be fired from a weapon, said projectile having an elongate circular body with side and rear surfaces and a photo-luminescent material, disposed on the rear surface, that re-emits radiation at when excited by receipt of radiation from a radiation source.

2. The ammunition projectile defined in claim 1, wherein said photo-luminescent material is additionally disposed on a side surface of the projectile body.

3. The ammunition projectile defined in claim 1, wherein said photo-luminescent material is a fluorescent dye.

4. The ammunition projectile defined in claim 3, wherein said fluorescent dye responds to excitation in one of the UV, visual and IR spectral bands.

5. The ammunition projectile defined in claim 3, wherein said fluorescent dye responds preferentially to the laser light illumination in a narrow frequency range.

6. The ammunition projectile defined in claim 3, wherein the fluorescent dye forms a coating on the projectile body.

7. The ammunition projectile defined in claim 3, wherein said projectile includes a transparent material disposed on the projectile body covering said fluorescent dye.

8. The ammunition projectile defined in claim 7, wherein said fluorescent dye forms a coating on an inside surface of said transparent material.

9. An ammunition projectile configured to be fired from a weapon, said projectile having an elongate circular body with side and rear surfaces a retro-reflective element, disposed on the rear surface, that preferentially reflects radiation received from a radiation source in the direction of the radiation source.

10. The ammunition projectile defined in claim 9, wherein said retro-reflective element is additionally disposed on a side surface of the projectile body.

11. The ammunition projectile defined in claim 9, wherein said retro-reflective element is affixed to the projectile body.

12. The ammunition projectile defined in claim 9, wherein said retro-reflective element is coated on the projectile body.

13. The ammunition projectile defined in claim 9, wherein said projectile includes a transparent material disposed on the projectile body covering said retro-reflective element.

14. The ammunition projectile defined in claim 13, wherein said retro-reflective material forms a coating on an inside surface of said transparent material.

15. The ammunition projectile defined in claim 9, wherein said projectile further includes a protective material that covers the retro-reflective element to protect the retro-reflective element while exposed to propellant gases.

16. The ammunition projectile defined in claim 15, wherein the removable protective shield is a combustible material.

17. The ammunition projectile defined in claim 9, wherein said retro-reflective element is positioned and oriented on the projectile body to allow for the rearward travel of reflected light, notwithstanding a yawing motion of the projectile during flight.

18. The ammunition projectile defined in claim 9, wherein said retro-reflective element is selected from the group consisting of corner cube reflectors, cat eyes and phase conjugated mirrors.

19. The ammunition projectile defined in claim 9, wherein said retro-reflective material is a metal form fitted to, embedded or formed into the projectile's rear housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0066] FIGS. 1A, 1B and 1C illustrate a Monte Carlo simulation of the impact location (against a vertical target) of shots for traced and untraced .308 projectiles fired at a range of 1500 meters. The figures show how the impact points for a number of tracer shots differ from the impact points for projectiles with standard pyrotechnic tracers.

[0067] FIGS. 2A and 2B depict an ammunition projectile with retro-reflectors affixed at the rear and the sides of the projectile body. that reflects incident light rearward.

[0068] FIG. 2C is a detailed illustration of retro-reflectors, as applied to a projectile, that reflect incident light rearward.

[0069] FIG. 2D illustrates how retro-reflectors are affixed to compensate for the conning motion in projectiles in ballistic flight.

[0070] FIG. 3 is a diagram showing a weapon and the trajectory of a projectile fired from a weapon.

[0071] FIG. 4 is a diagram showing a cone of illumination of strobe light emitted by a laser source that intersects the ballistic flight path of a projectile fired from a weapon. The laser aim is slightly depressed from the bore sight for optimized intersection with the projectile's trajectory within the dispersion of the light cone.

[0072] FIG. 5 is a diagram showing a radiation (e.g., optical) detector which receives a light reflection from a retro-reflector on the projectile.

[0073] FIGS. 6A and B are perspective views of a weapon having a laser source illuminating the projectiles in flight and a detector for receiving reflected radiation.

[0074] FIG. 7 is a representational diagram showing an error imparted by a fire control device which uses ballistic tables and metrological sensors to calculate a predicted hit point (gunner aiming point). Typically, a sniper will observe the impact point of a shot and provide an improved shot placement for a subsequent shot.

[0075] FIG. 8 is a representational diagram showing how the system of the present invention identifies the X and Y location of the detected reflected signals against the sky or backdrop.

[0076] FIG. 9 is a representational diagram showing how the system of the present invention (the view from fire control device at gunner's position) using reflected laser light to allow for registration of the prior shot. The image shows how the an accelerometer or other sensors measures post shot movement of the optical detector such that post shot movement is measured and the actual X and Y coordinates of an observed shot are corrected.

[0077] FIG. 10 is a representational diagram showing how the system of the present invention is used, post firing, to shift fields of view. The system measures the angular changes of the platform or camera at the same moment that the tracer's strobe signal is detected.

[0078] FIG. 11 is a representational diagram showing how the fire control computer calculates a new aiming solution after measuring actual drift and drop of an observed strobe tracer projectile.

[0079] FIGS. 12 and 13 are block diagrams of two systems, respectively, that use an algorithm to compute a bore sight adjustment and/or automatically adjust the aim point of subsequently fired projectiles.

[0080] FIGS. 14A-14E are detailed diagrams of a projectile with a retro-reflective rear surface.

[0081] FIG. 15 is a time diagram of laser-induced fluorescence showing the delay in response to excitation.

[0082] FIG. 16 is a representational diagram showing an ammunition projectile having a fluorescent dye at its rear surface.

[0083] FIG. 17 is a diagram showing an optical detector which receives a light emission from a laser-illuminated fluorescent dye on an ammunition projectile.

[0084] FIG. 18 is a block diagram of the system, similar to the systems of FIGS. 12 and 13, which uses an algorithm to compute a solution for bore sight adjustment and/or automatically adjusts the aim point of subsequently fired projectiles.

[0085] FIGS. 19A and 19B depict the linear beam divergence (in side view and top view) of 3 m rads and the ballistic trajectory of a .50 caliber (12.7 mm) projectile fired at 500 meters.

[0086] FIGS. 19C and 19D depict the transposed linear beam divergence (side view and top view) of 3 m rads and the ballistic trajectory of a .50 caliber (12.7 mm) projectile fired at 2000 meters.

[0087] FIG. 20 is a table illustrating the time of flight of a projectile to a target at ranges from 100-2000 meters. The 3.sup.rd column identifies the number of projectiles in an automatic volley when a machine gun is firing at 800 shots per minute rate of fire.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0088] The preferred embodiments of the present invention will now be described with reference to FIGS. 1-20 of the drawings.

[0089] Identical elements in the various figures are designated with the same reference numerals.

First Preferred Embodiment

[0090] According to a first preferred embodiment of the present invention, a projectile is fitted with retro-reflectors on its rear surface. An emitter is incorporated into a weapon system or into a stand-alone a spotter's scope. The emitter is slightly depressed from the axis of the barrel and focuses a cone of light in a tight beam that coincides with the ballistic trajectory of the projectile. The emitter illuminates the projectile's path in the spectrum allowing a spotter or sensors to precisely measure the ballistic trajectory. The system may also provide the capability to use automated tracking of the retro-reflectors affixed to a projectile. The invention is a kit that when mounted or incorporated into a weapon or spotting scope provides a methodology to adjust fires.

[0091] Cone of Illumination and Retro-Reflectors:

[0092] An illuminator emits UV, visual, NIR or MWIR light that illuminates the ballistic trajectory of the projectile. When attached to a weapon, the axis of the cone of illumination is slightly depressed from the center of axis of the barrel. When using the technique to illuminate an entire cone of light, the dispersion of the light emission and the angle of depression illuminate the projectiles ballistic flight path. The resulting depressed angle and dispersion is calculated for the caliber of the weapon system. Where a MEMs steerable laser beam is used, the laser search zone is limited to the light cone intersecting the ballistic path of the projectile. When incorporated into a sniper's scope the scope is pointed at the target and the zone of illumination is elevated above the target. The optical radiation traverses the space between the emitter and the projectile and light is reflected from reflected off the retro-reflectors affixed to the projectile. The retro-reflectors are affixed to the trajectory to with a geometry to return the incidence of light rearward during the trajectory of flight considering the yaw of the projectile and angle of attack. The signal may be continuous or emitted and reflected from the cat's eye or corner cube retro-reflective material affixed to the projectile.

[0093] Automated Optical Detection with Pulsed Signals:

[0094] Where the signals are pulsed at predetermined times (T1, T2, T3, etc.) following the time of firing (T0), an optical detector incorporated into the weapon or aligned with the spotting scope detects the angular geometry (projectile location in the sky) of the radiation reflected from the projectile as well as the duration (time length) of this reflected strobe in its field of view. The laser strobe emitter emits light at precise time intervals after launch or cartridge setback. The computer calculates the actual flight position at these precise post-firing intervals to the location that is forecasted by the original solution algorithm. The collected image is digitally processed and X and Y coordinates of the projectile's reflected strobe signal are identified by the laser's illumination of the projectile at predetermined time intervals. The delta positions are recorded (stored/registered). When a gunner subsequently wishes to engage new targets, the computer associated with the system uses an algorithm to identify a precise aim point solution using the observed trajectory of previous shots, thereby re-measuring and re-calibrating the distance and relative target elevation for subsequent firing of the weapon.

[0095] Table 1 is a time diagram illustrating the sequence of tracking when using strobe illumination signals where a shot where p is the required processing time for a subsequent fire control solution.

TABLE-US-00001 TABLE 1 Sequence of Measurements with Pulsed Signals Sequence of Measurement Methodology T0 a Fire Control Displays solution or aim point provided to gunner. T0 b Measurement of (a) radial Azimuth/Elevation Barrel Centerline and (b) elevation of barrel/fire control if not aligned T0 c Firing Pin Trigger pull (or hammer fall sensor) where a, b and c are lengths of time before T0 T0 Set Back of Cartridge Launch T1 Laser emits short pulse Retro-reflectors on the projectile reflect light back in the general direction of the origin of the shot The illuminated retro-reflectors on the projectile are observed. T1 + p If an automated system is utilized, the system provides an improved firing solution for the next shot. T2 Laser emits short pulse Retro-reflectors on the projectile reflect light back in the general direction of the origin of the shot The illuminated retro-reflectors on the projectile are observed. T2 + p If an automated system is utilized, the system provides an improved firing solution for the next shot. T3 Laser emits short pulse Retro-reflectors on the projectile reflect light back in the general direction of the origin of the shot The illuminated retro-reflectors on the projectile are observed. T3 + p If an automated system is utilized, the system provides an improved firing solution for the next shot.

[0096] Automated Optical Detection with Continuous Signal Tracing:

[0097] New tracking technology includes MEMS steerable lasers that allow for continuous X and Y adjustment of a micro laser illuminating a projectile affixed with a retro-reflector.

[0098] FIGS. 1A-1C respectively show a Monte Carlo simulation of sierra ball and tracer .308 bullets. Tracer bullets are normally fired in a set mix ball to tracer. The mean impact points and dispersion of tracers differs from ball projectiles. FIG. 2A shows the dispersion with standard .308 cartridge ammunition without tracers. FIG. 2B shows the dispersion of .308 ball tracer cartridges. FIG. 2C shows the dispersion with a mixed ball and tracer cartridge combination.

[0099] FIG. 2A depicts an ammunition projectile 10 having a retro-reflective coating at (42) the base of the projectile or a set of retro-reflectors (43) inset into the projectile body.

[0100] FIG. 2B depicts a projectile 10 having a retro-reflective coating (42) and (43) in ballistic flight where the projectile exhibits both conning motion comprised of pitch and yaw amplitude that vary over the flight time (44). The retro-reflectors (45) affixed to the projectile are positioned so that a sufficient surface area of the retro-reflectors have, during ballistic flight, a rearward angle of incidence to light emitted from the location of the weapon thereby reflecting light beams (46) to return to the vicinity of the weapon system or spotting scope. The positioning of retro-reflectors accommodates the normal pitch and yaw of a projectile.

[0101] FIG. 2C shows a detail of the retro-reflectors.

[0102] FIG. 2D is a perspective view depicting an emitter 18, illuminating a light cone 20 that intersects the ballistic path of a projectile in flight 10. The reflected incident light 46 is returned to the optical detector 24.

[0103] The system of the present invention is shown generally in FIGS. 3, 4 and 5. FIG. 3 shows a weapon 12 capable of firing projectiles in the direction of a target 14. The projectiles impact in the region of the target in a dispersion zone 16. FIG. 4 shows a laser source 18 mounted on the barrel of the weapon emitting light in a cone of illumination 20 that intersects the projectile 10. FIG. 5 shows light 22 reflected from the retro-reflectors 42, 43 on projectile reaching an optical detector 24 on or near the weapon 12. This arrangement is illustrated in perspective in FIGS. 6A and 6B.

[0104] FIG. 6A illustrates how a narrow beam emitter or laser 18 illuminates a conical area 20 illuminating the projectile 10. The retro-reflectors affixed to the projectile 10 reflects light rearward from the projectile to return to the vicinity of the shot. In this perspective the emitter 18 and the detector 24 are mounted on the weapon 12.

[0105] FIG. 6B illustrates how a MEMS steered laser beam 19 is emitted in a light cone 20 illuminating the projectile 10. The retro-reflectors affixed to the projectile 10. Light from the retro-reflectors affixed to the projectile (not show) reflect light rearward from the projectile to return to an optical detector 24. In this perspective the emitter 18 and the detector 24 are mounted on the weapon 12.

[0106] FIG. 7 depicts a solution and actual impact generated by current generation of fire-control devices use ballistic tables and limited metrological sensors to calculate a predicted hit point (gunner aiming point). Some fire control systems allow users to input manual drift and elevation offsets, but these manual offsets are generally linear. Unsolved contributing errors that diminish the fidelity of fire control solutions as many unmeasured errors are omitted from the aiming solution. The omitted aiming errors devices include (a) bore sight misalignment, (b) lot-to-lot errors, (c) occasion-to-occasion errors and (d) limitations in existing wind sensor technology. The inability to measure unsolved errors degrades the accuracy and precision of weapon fire control solutions, as illustrated in FIG. 7.

[0107] FIGS. 8, 9, 10 and 11 depict use of a pulsed technique (from the viewpoint of the gunner or optical detector) where a pulsed light strobe signal is emitted at predetermined times after set back during the flight path of the projectile and reflected back to the location of the gunner or spotter. The fire control device associated with the weapon optically identifies the x and y position during ballistic flight. Where a strobe technique is utilized, the measured time is at T1, T2, T3, Tn. Post firing resonance depicted in FIG. 10 can create shifting fields of view so a system will measures the angular changes of the platform or optical detector at the same moment that the projectile's strobe signal is recorded.

[0108] It should be noted, that the human in the loop remains a formable influence as spotters remain critical to the sniper profession. Accordingly, where manual calculations are used the invention provides for improving the observation and registration of shots as the methodology of reflecting optical emission from a projectile in flight until impact enhanced the spotter and sniper's ability to observe and correct errors using current practices. The registered information provides both an improved manual shooting technique and, where automation is available a methodology to track the projectile and improve the placement of subsequent shots.

[0109] FIG. 12 depicts the system for an automated system where the optical detector 36 and image processor 38 register the X and Y observation positions and where a sensor 34 measures the shot and post shot positions of the optical detector. A clock 48 initiates emitter illumination. The projectiles reflect the emission at T1, T2, T3, Tn and are reflected to the optical detector 36. The computer 40 and software 42, calculate the actual registered X and Y position of the ammunition at specific time. The device is equipped with a fast clock 48 to time stamp shot, images and sensor measurements. Fire control computer calculates a new fire control solution after measuring actual drift and drop of an observed strobe tracer projectile, as illustrated in FIG. 10. Sensor 34 may include air temperature, pressure, firing geometry and standard muzzle velocity. The measurement of observed projectile drift and vertical drop are obtained by an image processor 38 to isolate the strobe tracer's position. Simultaneously, angular changes in the detector are measured by sensors 34. The image processor search and detects the strobe images at pre-set intervals after firing. The optical detector 40 can be any type of image capturing device, for example a CCD, video camera, infrared camera or the like. It produces electronic signals representing the images and passes them to a signal processor 42. The processor 42 determines X,Y location and as well as the time duration of each received response from a projectile in flight. This information is passed to the computer 40 for calculating a lateral correction and a vertical correction in the aim of the weapon 12. An algorithm 46 written in the software code 42 computes a solution for bore sight adjustment and/or automatically adjusts the aim point of subsequently fired projectiles. The adjusted aim point is calculated and rendered in an output 51.

[0110] FIG. 13 shows an alternative to the manual measurements or optical strobe measurements, wherein the system can use a steerable MEMs laser, where a laser initiates a search pattern within a zone corresponding to the ballistic flight path and, when illuminating the retro-reflectors, an optical detector.

[0111] The system allows the fire control computers to readily observe and calculate fire control solutions that reduce or eliminate (1) occasion-to-occasion errors, (2) ammunition lot-to-lot errors, and (3) bore sight misalignment.

[0112] Fire control computers can readily adjust aim points using sensors to measure air temperature, pressure, firing geometry and standard muzzle velocities; however, practical considerations still limit the accuracy of calculated solutions. Lot-to-Lot ammunition variations along with occasions-to-occasion errors still result in limitations in the accuracy of fire control solutions. These errors also include those errors that result from varying wind conditions. Hence, measurement of the actual observed projectile drift and drop is necessary to allow fire control systems to provide improved aiming solutions.

[0113] System Overview:

[0114] As illustrated in FIG. 8, the system according to the invention reflects strobe laser light emissions at predetermined post firing (post set-back or launch) time windows. The retro-reflectors reflect light pulses that are collected by the radiation detector 24 (e.g. a camera, spotting scope or optical detector) and are manually or digitally recorded. At each pre-set time window the device records changes in the X and Y orientation of the reflected light. The system's image processing software measures the X and Y location of the optical strobe emission at the pre-set time window.

[0115] The system's signal processor identifies the X,Y location of the detected strobe signal against the sky or backdrop, as shown in FIGS. 9 and 10, thereby determining the actual drift and drop of the projectile 10 as seen from the gunner's position.

[0116] The measurement of observed projectile drift and vertical drop are obtained by an image processor to isolate the strobe tracer's position. Simultaneously, angular changes in the detector are measured. The image processor search and detects the strobe images at pre-set intervals after firing.

[0117] After detecting the actual observed azimuth drift and drop of a cartridge with an emitted light (FIG. 9), a spotter, gunner or the weapon's fire control system can utilize multiple methodologies to provide improved fire control solutions. The fire control system can (1) reset subsequent fire control solutions to use actual observed drift and drop, or (2) establish a correction factor which modifies the calculated fire control solution. Hence, use of actual observed data provides for a more accurate fire control solution.

[0118] Fire control computer calculates a new fire control solution after measuring actual drift and drop of an observed strobe tracer projectile, as illustrated in FIG. 10.

[0119] The diagram of FIG. 11 shows projectile strobe signals from the next subsequently fired projectile as viewed from a gunner's position with the hit point corresponding to aim point.

[0120] The system and methodology according to the invention allow fire control devices to adjust the aim point (in azimuth and elevation) so that subsequently fired cartridges hit the intended target by using actual observed azimuth drift and vertical drop. With the actual drift observed by the fire control's optical sensor, the fire control computer calculates improved solutions for new engagements. As subsequent volleys are fired, the coded regressive algorithm improves the fire control solution as it repeatedly measures the actual trajectory of cartridge with an increasing sample size.

[0121] One should also note that the invention can be incorporated into spotting scopes where the observed shot methodology and hand-held calculators currently used by snipers is also improved.

[0122] In the system shown in FIGS. 12 and 13 an algorithm 46 coded to software 42 with a computer 40 refines the aiming solution.

[0123] FIGS. 12 and 13 show a system comprising an emitter 33, 61 one or more sensors 34, an optical detector 36, an image or signal processor 38. The sensors 34 identify various parameters of the weapon 12. A clock, 48 time stamps all inputs. Such sensors may include various types including position sensors, sensors for gun elevation and the like. In FIG. 12, the emitter 33 is either a focused light source or laser which is triggered by the computer 40 to produce a strobe of light.

[0124] In FIG. 13, after a projectile is fired, a sensor initiates a search track for the MEMS laser emitter 61. When the MEMS emitter 61 initiates searches a pattern illuminating a narrow beam in a cone 20 until it receives reflected light from the projectile's retro-reflector 10, 42, 43.

[0125] After acquiring the target, the computer 40 and software 42 directs the steerable MEMS laser 61. During the projectile's flight, the laser X and Y azimuth and elevation corresponds to the steered MEMS laser 61. The X and Y location of the X and Y MEMS laser azimuth and elevation is recorded with specific clock time (48) stamps. The computer then runs a coded sub-routine with the regressive algorithm and passes registration data output 51 to the fire control device for refinement of the aim point for the next projectile to be fired. Where a return is lost, the device reinitiates a search track from the vicinity of the previous contact in a pattern in the cone 20.

[0126] FIGS. 14A-14E show a projectile 60 which may be used with the system in accordance with this first preferred embodiment of this invention.

[0127] FIG. 14A depicts the projectile with a tapered section 61 in the rear. As shown in FIG. 14B the rear surface of the projectile is covered a removable disc 62 which, when removed prior to firing, reveals a retro-reflector 64.

[0128] FIG. 14C shows the projectile in flight with the retro-reflective surface 64. As indicted in the enlarged view of FIG. 14D, the retro-reflector is formed in a pattern that generally reflects light in the direction from whence it came. This pattern, shown in greater detail in FIG. 14E, comprises a grid of star shapes surrounded by diamond shaped patterns of reflective planes. The retro-reflector is held in place on the projectile 60 by four tabs 66.

Second Preferred Embodiment

[0129] According to a second preferred embodiment of the present invention, the projectile has a layer of photo-luminescent material, instead of retro-reflective material, on its rear surface. This embodiment of the invention provides for a method and means collecting optical location signals emitted by the luminescent material on the projectile while in flight after firing from a weapon, and for simultaneously recording movement and/or acceleration. These optical signals are transmitted from a projectile in either the visual, ultraviolet and infra-red spectrum. The signals are re-emitted from the projectile at predetermined times (T1z, T2z, T3z, etc.) following the time of firing (T0). An optical detector incorporated into the weapon launcher or on an associated platform detects the angular geometry (projectile location in the sky) of the radiation re-emitted by the photo-luminescent material on the projectile as well as the duration (time length) of this re-emitted strobe in its field of view.

[0130] FIG. 15 is a time diagram illustrating the time delay of fluorescence in response to excitation by laser light. As may be seen, there is a delay of about 3 milliseconds between excitation and response. This period of delay is designated hereinafter by the letter z.

[0131] The operating sequence of the system according to the invention is depicted in Table 1 below.

TABLE-US-00002 TABLE 2 Sequence of Measurements Sequence of Measurement Methodology T0 a Fire Control Displays solution based on solution derived from algorithm (based on previous measurement) T0 b Measurement of (a) radial Azimuth/Elevation Barrel Centerline and (b) elevation of barrel/fire control if not aligned T0 c Firing Pin Trigger pull (or hammer fall sensor) where a, b and c are lengths of time before T0 T0 Set Back of Cartridge Launch T1 Laser emits short pulse T1 + z Response of dye on projectile time z later T1 + z Camera image (x1, y1) of strobe response and camera position (xx1, yy1) T2 Laser emits short pulse T2 + z Response of dye on projectile time z later T2 + z Camera image (x2, y2) of strobe response and camera position (xx2, yy2) T3 Laser emits short pulse T3 + z Response of dye on projectile time z later T3 + z Camera image (x3, y3) of strobe response and camera position (xx3, yy3) Tn + z Camera image (xn, yn) of strobe response and camera etc. position (xxn, yyn)

[0132] FIG. 16 shows an ammunition projectile 110 having a fluorescent dye 111 applied to its rear surface. The fluorescent dye preferably has a transparent or translucent coating to protect against damage or it is covered by a plastic shield or the like attached to the rear of the projectile.

[0133] The system according to the invention has the capability to detect the laser-induced fluorescence (LIF) of a projectile while in flight. The re-emission in response to the LIF occurs the short period of time (z) after transmission of the laser strobe excitation.

[0134] When a phosphor is included with the projectile dye, the system can utilize phosphor thermometry. By measuring this re-emitted light duration (z) the system can use temperature differences observed on projectiles in flight to further differentiate between and among the locations of multiple projectiles when the rate of fire is such that multiple projectiles are in flight at the same time.

[0135] The system of the present invention is shown generally in FIG. 17. FIG. 17 shows light 122 re-emitted by the fluorescent dye 111 on the projectile 110, reaching an optical detector 124 on or near the weapon 112.

[0136] The laser strobe emits light at precise time intervals after launch or cartridge setback. The weapon fire control system compares the actual flight position at these precise post-firing intervals to the location that is forecasted by the original solution algorithm. The delta positions are recorded (stored/registered) and the fire control provides a gunner with new corrected aim points using the registered shots.

[0137] The optical signals emitted by the fluorescent dye material on the projectile are collected by an optical detector, such as an IR camera, co-located with the weapon. The image is digitally processed and X and Y coordinates of the projectile's strobe signal are identified by collection at the predetermined time intervals. When a gunner subsequently wishes to engage new targets, the computer associated with the system uses an algorithm to identify a precise aim point solution using the observed trajectory of previous shots, thereby re-measuring and re-calibrating the distance and relative target elevation for subsequent firing of the weapon.

[0138] Optical emissions include light in the ultraviolet, infra red and visual wavelengths. The weapon's fire control unit has the capability to emit a cone of light (modulated to strobe at a set time) that intersects with the ballistic path of the projectile. Normally, the laser emission will be aligned vertically. The laser's horizontal alignment will drop slightly at an inclination so the top edge of the laser light illumination cone is aligned horizontally with the centerline of the barrel. This geometry allows the laser light cone to cover the entire ballistic drop of the projectile.

[0139] The laser emitter adjacent the weapon transmits a short, intense light strobe signal at predetermined times after set back during the flight path of the projectile. This occurs at T1=(time of emission+z), T2=(time of emission+z), T3=(time of emission+z), Tn=(time of emission+z) where z is the time delay in milliseconds. Using this technique it is possible to select dye combinations where the laser strobe transmits strobe signals at a given frequency and the dye's optical response differs in its response frequency. This is used by the optimize system to preclude detection by potential adversaries. It is possible, in fact, to harness the heat of the projectile to change the spectral response of the dye.

[0140] The transmission of electromagnetic (optical) signals differs under certain atmospheric conditions and frequencies. The delay (z) between the laser's production of a light strobe and the tracer's fluoresced re-emitted response, as well as the length (duration) of the response signal, are used by the fire-control detection software to eliminate detection of stray reflective light that occurs when the laser beam strobe signal reflects off of objects and to distinguish between multiple projectiles.

[0141] Projectile flight geometry provides for reflection of light rearward to the gunner's position at pre-set intervals though the entire flight path. The fire control device associated with the weapon optically identifies the position (T1=position x1, y1, T2=position x2, y2, T3=position x3, y3, . . . Tn=position xn, yn) of the projectile at set intervals.

[0142] The invention provides for a system to collect optical location signals from a projectile in flight which are excited by an optical light source (visual, ultraviolet and infra-red). The fire control uses observed time-location and angular observation data to compute an improved ballistic solution.

[0143] The system allows the fire control computers to readily observe and calculate fire control solutions that reduce or eliminate (1) occasion-to-occasion errors, (2) ammunition lot-to-lot errors, and (3) bore sight misalignment.

[0144] Fire control computers can readily adjust aim points using sensors to measure air temperature, pressure, firing geometry and standard muzzle velocities; however, practical considerations still limit the accuracy of calculated solutions. Lot-to-Lot ammunition variations along with occasions-to-occasion errors still result in limitations in the accuracy of fire control solutions. These errors also include those errors that result from varying wind conditions. Hence, measurement of the actual observed projectile drift and drop is necessary to allow fire control systems to provide improved aiming solutions.

[0145] The current generation of fire-control devices use ballistic tables and metrological sensors to calculate a predicted hit point (gunner aiming point). Some fire control systems allow users to input manual drift and elevation offsets, but these manual offsets are generally linear. Hence, the current generation fire control devices continue to provide inaccurate aim points due to the fact that they only calculate a limited number of inputs while many unsolved sources of errors are not factored in. Unsolved errors include (a) bore sight misalignment, (b) lot-to-lot errors, (c) occasion-to-occasion errors and (d) limitations in existing wind sensor technology. All unsolved errors degrade the accuracy and precision of weapon fire control solutions.

[0146] The projectile's stimulated dye response occurs at discrete intervals (at T1+z, T2+z, T3+z, . . . Tn+z, where z is the response delay) that are observed by fire control devices equipped with optical sensors. The dye's strobe response to laser illumination identifies the position of the projectile at set time intervals after set-back (time T0). The system according to the invention optically collects the strobe light emissions at predetermined post firing (post set-back or launch) time windows. The projectile's fluorescent dye emits light strobe pulses that are collected by an optical detector (e.g. a camera) and digitally recorded. At each pre-set time window the device also records changes in the X and Y orientation of dye emission. The system's image processing software measures or signal processing algorithms calculate the X and Y location of the optical strobe emission at the pre-set time window.

[0147] The system's signal processor identifies the X,Y location of the detected dye strobe signal against the sky or backdrop, thereby determining the actual drift and drop of the projectile as seen from the gunner's position.

[0148] The measurement of observed projectile drift and vertical drop are obtained by an image processor to isolate the strobe tracer's position. Simultaneously, angular changes in the detector are measured. The image processor search and detects the strobe images at pre-set intervals after firing. Alternatively, the signal processor detects the signal at pre-set intervals after firing.

[0149] Post firing resonance can create shifting fields of view. The system measures the angular changes of the platform or optical detector (camera) at the same moment that the projectile's strobe signal is recorded.

[0150] After detecting the actual observed azimuth drift and drop of a cartridge, a weapon's fire control system can utilize two methods to provide improved fire control solutions. The fire control system can (1) reset subsequent fire control solutions to use actual observed drift and drop, or (2) establish a correction factor which modifies the calculated fire control solution. Hence, use of actual observed data provides for a more accurate fire control solution.

[0151] Fire control computer calculates a new fire control solution after measuring actual drift and drop of an observed strobe tracer projectile.

[0152] The system and methodology according to the invention allow fire control devices to adjust the aim point (in azimuth and elevation) so that subsequently fired cartridges hit the intended target by using actual observed azimuth drift and vertical drop. With the actual drift observed by the fire control's optical sensor, the fire control computer calculates improved solutions for new engagements. As subsequent volleys are fired, the fire control may use commonly known mathematical algorithms to further improve the precision of the corrected aim point as it repeatedly measures the actual position of cartridge drift and azimuth with a larger sample size.

[0153] In the system shown in FIG. 18 an algorithm computes a solution for bore sight adjustment and/or automatically adjusts the aim point of subsequently fired projectiles.

[0154] The algorithm develops fire control solutions (aim points) using actual, observed azimuth and elevation.

[0155] FIG. 18 shows a system 130 according to the invention for a weapon 112 comprising an emitter 133, one or more sensors 134, an optical detector (e.g. camera) 136, a signal processor 138 and a computer 140 operating with software 142.

[0156] The sensors 134 are used to identify various parameters of the weapon 112. Such sensors can be of various types, for example, position sensors, sensors for gun elevation, optical sensors and the like. The emitter 133 is a high-powered laser which is triggered by the computer 140 to produce a strobe of light.

[0157] The optical detector 136 can be any type of image capturing device, for example a video camera, infrared camera or the like. It produces electronic signals representing the images and passes them to a signal processor 138. The processor 138 determines X,Y location and as well as the time duration of each received response from a projectile in flight. This information is passed to the computer 140 for calculating a lateral correction and a vertical correction in the aim of the weapon 112.

[0158] The fire control device measures the angular position of the weapon 112 when the weapon fires a projectile aimed at a target. This angular position information includes a radial azimuth/elevation barrel centerline and elevation of barrel/fire control elevation, The angular position is measured by the sensors 134 and this information is also passed to the computer 140.

[0159] The computer determines the drift and drop of the fired projectile and passes this data to the fire control device for adjusting the aim point of for the next projectile to be fired.

[0160] The time delay (z) of the re-emitted signal allows the computer 140 to disregard reflections received by the detector 138 from stray objects. The time duration of the re-emitted signal allows the computer to distinguish between multiple projectiles in flight which have been rapidly fired successively by the weapon 112. Closer (and therefore hotter) projectiles will have shorter duration re-emissions that the projectiles that are further away (and therefore cooler).

[0161] Comparison of Systems in First and Second Embodiments:

[0162] The first embodiment of the present invention concerns a optically trackable projectile fitted with a retro-reflective tracer. Such a system may be coupled to an apparatus allowing for the recording of the projectile's flight path and may be coupled with a methodology for improving the fidelity of aiming solutions in weapons using projectiles with one or more retro-reflectors. In the second preferred embodiment the projectile uses a projectiles with photo-luminescent material (e.g., a fluorescent dye) applied to the projectile body to provide laser-induced fluorescence. Like a projectile fitted with a retro-reflector, the projectile may be coupled with a apparatus that allows for the recording of the projectile's flight path.

[0163] In the discussion above, when referring to times T1+z, T2+z, TN+z, z was the time addition (in milliseconds) from re-emission delay, post illumination of the laser induced fluorescence. When applying the same methodology to retro-reflective tracers it is possible to use the same formulas, but in such a case it is useful to use a definition of z whereby z is the time it takes for light to travel (2 back and forth) over the distance after emission. For example, the light from an emitter (with a target at 500 meters) will travel back and forth (1000 meters) in 3.33 micro-seconds. In this circumstance, the technique allows for obtaining distinct range data of the projectiles (in flight) which can be useful for regressive algorithms. This is also useful for distinguishing among the many projectiles in flight with a machine gun firing continuously at 800 rounds per second.

[0164] FIGS. 19A and 19B illustrate linear beam divergence (in side view and top view) for a .50 caliber projectile fired at a target at 500 meters. FIGS. 19C and 19D illustrate linear beam divergence for a .50 caliber projectile aimed at a target 2000 meters away. As may be seen, the system employed in FIGS. 19C and 19D has a steerable MEMS laser emitter that follows the path of the projectile in flight.

[0165] FIG. 20 is a table illustrating the time of flight of a projectile to a target at ranges from 100-2000 meters. The third column identifies the number of projectiles in a automatic volley when a machine gun is firing at an 800 shots per minute rate of fire.

[0166] There has thus been shown and described a novel trackable ammunition projectile which fulfills all the objects and advantages sought therefor. Many changes, modifications, variations and other uses and applications of the subject invention will, however, become apparent to those skilled in the art after considering this specification and the accompanying drawings which disclose the preferred embodiments thereof. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention, which is to be limited only by the claims which follow.