Abstract:
A marksmanship training device is disclosed for simulating long range  weas so as to train a marksman in the use of the particular weapon being simulated. The marksmanship training device comprises a laser transmitter mounted within the weapon being simulated which, when activated by the marksman, broadcasts at a target a square wave beam of laser light having a predetermined frequency. A receiver, mounted upon the target, will sense only a square wave laser light beam having the predetermined frequency mentioned above and activate a buzzer so as to indicate that the marksman has scored a hit upon the target.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to weapons training simulators. In particular, this invention relates to a weapons training simulator which utilizes a laser transmitter at the firing point, and a receiver at the aiming point so as to provide an efficient hit indication of the target aimed at by a trainee marksman. 
     2. Description of the Prior Art 
     In training military and other personnel in the use of long range weapons, rifles, and the like, the military, as well as civilian agencies concerned with such training, have utilized laser emissions instead of live ammunition at the firing point, and a form of detector apparatus at the target or aiming point combined with some audible or visible indication that a hit has been scored upon the target. 
     One such device of the prior art utilizes an array of solar cells combined with transformers, detectors, and other electronic amplifying equipment affixed directly to the target such that when the target is impinged by a laser beam from the firing point, at least one of the detectors will detect its presence, and generate an alarm through the solar cell pick-up and electronic amplifying equipment to activate a hit indicator. 
     Still another device of the prior art utilizes a target having mounted on the front portion thereof a reflective surface which reflects therefrom an incoming laser beam all the way back to the firing point where a detector is located. The detector, in turn, picks up the retroreflected laser beam and then provides an audible and/or visible indication that a hit has been scored upon the target. 
     While satisfactory for their intended purpose of marksmanship training, the aforementioned devices of the prior art ordinarily leave something to be desired, especially from the standpoints of aiming accuracy at long distances, safety, and complexity in design. In addition, the aforementioned devices of the prior art are designed for use at limited distances. 
     SUMMARY OF THE INVENTION 
     The subject invention overcomes some of the disadvantages of the prior art, including those mentioned above, in that it comprises a relatively simple long range weapons fire simulation system which is responsive to laser light pulses from a laser transmitter rather than being responsive to ordinary light or other less coherent, concentrated, and intense types of radiant energy. Consequently, it is far more sensitive which, in turn, makes it far more efficient and accurate in its response, in that it more closely simulates the aiming accuracy of a long range weapons system. 
     Included in the subject invention is the aforementioned laser transmitter which broadcasts therefrom a square wave beam of laser light, and a receiver mounted upon a target adapted for detecting the aforementioned square wave beam of laser light, and for providing in response to the detection of the square wave beam of laser light thereby, a hit indicator signal. 
     The transmitter comprises timing circuit means for providing a fundamental clock signal having a predetermined frequency and switching circuit means for activating a laser light source in response to the aforementioned fundamental clock signal. The laser light source, in turn, emits therefrom the aforementioned square wave beam of laser light, the frequency of which is the same as the frequency of the aforementioned fundamental clock signal. 
     The receiver comprises a sensor element adapted to detecting the square wave beam of laser light and for providing, in response to the detection of the square wave beam of laser light, a square wave signal having a frequency the same as the frequency of the square wave beam of laser light, a variable gain amplifier for amplifying the square wave signal, and a phase lock loop circuit for producing in response to the square wave signal the aforementioned hit indicator signal. The hit indicator signal, in turn, activates a buzzer so as to indicate that a hit has been scored upon the target. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a pictorial representation of a typical situation in which the subject invention may be utilized to an advantage; 
     FIG. 2 is an electrical schematic diagram of the system constituting the subject invention; 
     FIG. 3 is an ideal graphical representation of some of the signals produced at the outputs of some of the electrical components of FIG. 2; and 
     FIG. 4 is an expanded graphical representation of one of the signals of FIG. 3 and other internal component output signals of the system of FIG. 2 coordinated therewith. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment of the subject invention will now be discussed in some detail in conjunction with all of the figures of the drawing, wherein like parts are designated by like reference numerals, insofar as it is possible and practical to do so. 
     Referring now to FIG. 1, there is shown a tank 11 having a barrel 13 in which is mounted a laser transmitter 15. As tank 11 is aimed for direct fire maneuvers at a tank 17, barrel 13 of tank 11 is moved in azimuth and elevation by trainees 19, 21, and 23. Tank 11 is fired in simulation by trainee 19 activating a three position selector switch 25, which is the trigger mechanism of the subject invention and which, when activated by trainee 19, energizes laser transmitter 15 such that laser transmitter 15 will broadcast along a predetermined optical or light path a square wave beam of laser light 27. 
     Mounted upon tank 17 is a receiver 28 which will detect the square wave beam of laser light 27 broadcast by laser transmitter 15. Whenever receiver 28 detects the square wave beam of laser light 27 broadcast by laser transmitter 15, receiver 28 will activate a buzzer 29, FIG. 2, located in tank 17. This, in turn, indicates to an instructor, not shown, seated in tank 17 that trainees 19, 21, and 23 have scored a hit upon tank 17. 
     At this time, it may be noted that a variety of weapons such as a bazooka 31 may be utilized with the subject invention by mounting laser transmitter 15 therein. This, in turn, allows trainees 33 and 35 to aim and fire bazooka 31 in simulation at tank 17. 
     Referring now to FIG. 2, there is shown a schematic diagram of laser transmitter 15 comprising a master clock 37, the output of which is connected to the input of an inverter 39, with the output thereof connected to the input of a counter 41. The output of counter 41 is, in turn, connected to the input of a counter 43 and the trigger input of a flip-flop 45. 
     The output of counter 43 is connected to the trigger input of a flip-flop 47, the Q output of which is connected to the first input of three position selector switch 25. In addition, the Q output of flip-flop 45 is connected to the second input of selector switch 25, with the third or neutral input thereof being left unconnected. 
     The output of selector switch 25 is connected through a resistor 49 to the base of an NPN transistor 51, the collector of which is connected to the output of a positive direct current voltage source 53, and the emitter of which is connected to the emitter of an NPN transistor 55. In addition, the base of NPN transistor 51 is connected through resistor 49 and a resistor 56 to the output of a positive direct current voltage source 57. 
     The output of positive direct current voltage source 53 is connected through a resistor 58 to the input of a laser light source 59 which emits therefrom, when activated, the aforementioned square wave beam of laser light 27. The output of laser light source 59 is, in turn, connected to the collector of NPN transistor 55, the base of which is connected through a resistor 61 to the input of a diode 63. The output of diode 63 is connected to the input of a diode 65, the output of which is connected to the input of a diode 67, with the output thereof connected to a ground 69. In addition, the base of NPN transistor 55 is connected through resistor 61 and a resistor 71 to the output of positive direct current voltage source 53. 
     The emitters of NPN transistors 51 and 55 are connected to the collector of an NPN transistor 73, the base of which is connected through a resistor 75 to ground 69. The emitter of NPN transistor 73 is connected through a variable resistor 77 to the output of a negative direct current voltage source 79. In addition, the emitter of NPN transistor 73 is connected through a resistor 81 to the output of a diode 83, the input of which is connected to the base of NPN transistor 73. 
     It should be noted that the combination of NPN transistor 73, resistors 75 and 81, diode 83, variable resistor 77, and negative direct current voltage source 79, when combined in the manner described above, form a constant current source 84, the operation of which will be described more fully below. 
     Spatially disposed downstream from laser light source 59 along optical light path 27 is a fiber optics bundle 85 which, along with laser light source 59, is commercially available from RCA of Lancaster, Pa., with the model number being C86010E. 
     Spatially disposed downstream from fiber optics bundle 85 along optical light path 27 is a lens 86. Lens 86 is positioned such that the focal point thereof is located at the end of fiber optics bundle 85. 
     Spatially disposed downstream from lens 86 along optical light path 27 is receiver 28 which includes a lens 87 positioned downstream from lens 86. Spatially disposed downstream from lens 87 is a photodiode sensor 89 which is positioned at the focal point of lens 87. 
     The output of a negative direct current voltage source 91 is connected to the input of photodiode sensor 89, the output of which is connected to the input of an amplifier 93, with the output thereof connected to the input of a variable gain amplifier 95. The output of variable gain amplifier 95 is, in turn, connected to the input of a phase lock loop circuit 97, the output of which is connected to the aforementioned buzzer 29. 
     At this time it may be noteworthy to mention that the series combination of photodiode sensor 89 and amplifier 93 may be, for example, a hybrid receiver, Model MDA 7705, manufactured by Meret, Inc., of Santa Monica, Calif. In addition, it may be noted that phase lock loop circuit 97 may be a frequency selective phase lock loop assembly, Model RE 8001, manufactured by Meret, Inc. 
     Affixed to laser light source 59 is a temperature probe 99, the first terminal of which is connected to the first terminal of a temperature monitor 101 and the second terminal of which is connected to the second terminal of temperature monitor 101. Positioned adjacent laser light source 59 is a cooler element 103, the output of which is connected through a variable resistor 105 to the output of direct current voltage source 53. 
     It may be noted at this time that cooler element 103 may be a thermo-electric module, Model 930-71, manufactured by Borg-Warner, Inc., of Des Plaines, Ill. In addition, temperature monitor 101 may be an Omegatemp Temperature Monitor manufactured by Omega Engineering, Inc., of Stamford, Conn. 
     The operation of the subject invention will now be discussed briefly in conjunction with all of the figures of the drawing. 
     Referring first to FIG. 1, there is shown tank 11, the barrel 13 of which is being aimed in azimuth and elevation by trainees 19, 21, and 23 for direct fire maneuvers at tank 17. Tank 11 is then fired in simulation by trainee 19 activating three position selector switch 25 which, when activated by trainee 19, energizes laser transmitter 15 such that laser transmitter 15 will broadcast square wave light beam 27 at tank 17. Whenever receiver 28 detects the square wave beam of laser light 27 broadcast by laser transmitter 15, receiver 28 will activate buzzer 29, FIG. 2. This, in turn, indicates to the aforementioned instructor, not shown, seated in tank 17 that trainees 19, 21, and 23 have scored a hit upon tank 17. 
     As mentioned above, a variety of weapons, such as bazooka 31, may be utilized with the subject invention by mounting laser transmitter 15 therein. Because the subject invention operates in the same manner when laser transmitter 15 is mounted in barrel 13 of tank 11 as when laser transmitter 15 is mounted in bazooka 31, and for the sake of keeping this disclosure as simple as possible, only the operation of the subject invention with respect to tank 11 will be described. 
     Referring now to FIG. 2, there is shown clock 37 which generates a master clock signal having a preset frequency of 786 kilohertz similar to that depicted in FIG. 3(A). The clock signal of FIG. 3(A) is supplied to the input of inverter 39 which inverts the aforementioned clock signal so as to provide at the output thereof a clock signal similar to that illustrated in FIG. 3(B). The clock signal of FIG. 3(B) is then supplied to the input of counter 41 which divides the frequency thereof by four so as to provide at the output thereof a clock signal similar to that depicted in FIG. 3(C). 
     The clock signal of FIG. 3(C) is supplied to the trigger input of flip-flop 45, which divides the frequency thereof by two so as to provide at the Q output thereof a clock signal similar to that illustrated in FIG. 3(D), the frequency of which is 98.25 kilohertz. 
     To facilitate the better understanding of that portion of the mode of operation of the invention to be discussed now, it would appear to be noteworthy to mention at this time that the signal waveform of FIG. 4(A) is, in fact, identical to that of FIG. 3(C). However, in the portrayal of the signal waveform of FIG. 4(A), the time frame represented by the abscissa has been greatly reduced so as to provide a frame that will permit the disclosure of the other signals shown in FIG. 4(B) and FIG. 4(C). 
     The signal of FIG. 4(A) which emanates from the output of counter 41 is supplied to the input of counter 43, which divides the frequency thereof by six so as to provide at the Q output thereof a clock signal similar to that illustrated in FIG. 4(B). The clock signal of FIG. 4(B) is then supplied to the trigger input of flip-flop 47, which divides the frequency thereof by two so as to provide at the Q output thereof a clock signal similar to that illustrated in FIG. 4(C), the frequency of which is 16.375 kilohertz. 
     At this time it may be noteworthy to mention that the clock signal of FIG. 4(C) is to be utilized by the subject invention since receiver 28 is adapted to detect a square wave beam of laser light having a frequency of 16.375 kilohertz, as will be explained more fully below. In addition, it may be noted at this time that the clock signal of FIG. 3(D) is adapted for utilization with a receiver element described in U.S. patent application Ser. No. 199,156, entitled Weapons Training Apparatus for Simulating Long Range Weapons, by Albert H. Marshall, Gary M. Bond, and Bon F. Shaw, filed concurrently with this application. 
     The clock signal of FIG. 4(C) which emanates from the Q output of flip-flop 47 passes through selector switch 25 and resistor 49 to the base of transistor 51 so as to activate transistor 51. Whenever the base of transistor 51 is in the logic &#34;1&#34; state, or in response to each clock pulse of the clock signal of FIG. 4(C), the direct current voltage signal provided by positive direct current voltage source 53 will pass through transistors 51 and 73, and variable resistor 77 to the output of negative direct current voltage source 79. This, in turn, inactivates transistor 55, which is now reverse biased at the base to emitter junction thereof, thereby inactivating laser light source 59 so as to prevent laser light source 59 from broadcasting square wave laser light beam 27, as will be discussed more fully below. 
     Whenever the clock signal of FIG. 4(C) is in the logic &#34;0&#34; state, transistor 51 is inactivated, thereby activating transistor 55 which is now forward biased at the base to emitter junction thereof, as will be discussed more fully below. This, in turn, allows the direct current voltage signal provided by direct current voltage source 53 to pass through resistor 58, light source 59, and transistor 55 so as to activate light source 59. Light source 59, in response to the direct current voltage signal provided by direct current voltage source 53, provides a stream of laser light. Thus, in response to the clock signal of FIG. 4(C), laser light source 59 will broadcast along the above mentioned predetermined optical light path, square wave beam of laser light 27. 
     At this time it should be noted that the series combination of resistor 71 and diodes 63, 65, and 67 form a voltage divider circuit such that the base of transistor 55 is biased at a constant voltage. This, in turn, assures that the base to emitter junction of transistor 55 is forward biased whenever transistor 51 is inactivated by the clock signal of FIG. 4(C). 
     Whenever selector switch 25 is in the neutral position, so as to prevent the clock signal of either FIG. 3(D) or FIG. 4(C) from passing therethrough, the direct current voltage signal provided by direct current voltage source 57 will pass through resistors 56 and 49 to the base of transistor 51 such that the base of transistor 51 will be in the logic &#34;1&#34; state. This, in turn, as discussed previously, activates transistor 51 such that the direct current voltage signal provided by direct current voltage source 53 will pass therethrough so as to inactivate laser light source 59, thereby preventing laser light source 59 from broadcasting square wave beam of laser light 27. 
     At this time it may be noteworthy to mention that the direct current voltage signal provided by direct current voltage source 53 is maintained at a constant current level of approximately two hundred milliamps by constant current source 84 so as to maintain the power output of square wave laser light beam 27 at a constant power level of two milliwatts. A negative direct current voltage signal provided by direct current voltage source 79 flows from ground 69, through resistor 75, diode 83, resistor 81, and variable resistor 77, to direct current voltage source 79, such that the voltage drop from the base of transistor 73 to the emitter thereof remains at a constant value. This, in turn, will cause the direct current voltage signal provided by direct current voltage source 53 to remain at the aforementioned current level of approximately two hundred milliamps. 
     In addition, it should be noted that an increase in the resistance of variable resistor 77 will decrease the current level of the direct current voltage signal provided by direct current voltage source 53, while a decrease in the resistance of variable resistor 77 will increase the current level of the aforementioned direct current voltage signal. This, in turn, allows for the variation of the output power level of square wave laser light beam 27 broadcast by laser light source 59. 
     Also, it may be noteworthy to mention that diode 83 is utilized within the subject invention to compensate for temperature variations within transistor 73 such that when transistor 73 is active, the direct current passing therethrough will remain constant. 
     Further, it should be noted that temperature probe 99 continuously monitors the temperature of laser light source 59. Temperature probe 99 then supplies to temperature monitor 101 an analog signal proportional to the temperature of laser light source 59 monitored thereby. Temperature monitor 101, in response to the aforementioned analog signal, will provide trainees 19, 21, and 23, FIG. 1, with a visual indication of the temperature of laser light source 59 so as to allow one of the aforementioned trainees to adjust variable resistor 105, thereby either increasing or decreasing the cooling capacity of cooler element 103. This, in turn, insures that the temperature of laser light source 59 will remain at a constant value so as to make certain that the output power level of square wave laser light beam 27 broadcast by laser light source 59 will remain at the aforementioned value of two milliwatts. 
     Referring now to FIGS. 1 and 2, whenever tank 11 is fired in simulation by trainee 19 activating three position selector switch 25, light source 59 broadcasts through fiber optics bundle 85, square wave laser light beam 27. Fiber optics bundle 85, in turn, integrates square wave laser light beam 27 such that the square wave laser light beam 27 which appears at lens 86 is circular in shape, thus simulating a live round. Lens 86 collimates square wave laser light beam 27, which is then transmitted along the above mentioned optical light path to lens 87 of receiver 28. 
     Lens 87 focuses square wave laser light beam 27 upon photodiode sensor 89 which, when activated by the negative direct current voltage signal provided by negative direct current voltage source 91, will detect square wave laser light beam 27 broadcast by laser light source 59. Photodiode sensor 89 will then provide at the output thereof, in response to the square wave laser light beam 27 sensed thereby, a square wave signal, the frequency of which is 16.375 kilohertz. The square wave signal provided by sensor 89 is supplied through amplifiers 93 and 95, which amplify the aforementioned signal to a more useful voltage level, to the input of phase lock loop circuit 97. 
     Phase lock loop circuit 97 is preset to provide at the output thereof a hit indicator signal, which is a direct current voltage signal, upon receiving at the input thereof a square wave signal having a frequency of 16.375 kilohertz. Thus, whenever the square wave signal provided by sensor 89 is received at the input of phase lock loop circuit 97, phase lock loop circuit 97 will supply to the input of buzzer 29 the aforementioned hit indicator signal. This, in turn, activates buzzer 29 so as to indicate to the instructor seated within tank 17 that tank 11 has scored a hit thereon. 
     From the foregoing, it may readily be seen that the subject invention comprises a new, unique, and exceedingly useful marksmanship training device for simulating long range weapons which constitutes a considerable improvement over the known prior art. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.