Laser-based shooting simulation systems for small arms are commonly used in both civil applications such as tactics and shooting games, and in gunnery and skills training for military trainees. The firearm simulators used in such systems emulate fire shots by sending a light beam, such as a laser beam, of short duration when they are triggered by a user.
To make the military training realistic, and to take soldiers as close to the experience of firing live rounds as possible, real firearms using blank cartridges are often used as such firearm simulators. Thereby, the military trainees experience the sound, the burst and the visual impression of real combat equipment, bringing them as close as possible to a true shooting sensation. In this case, a laser unit, often referred to as a “simulator”, is detachably connected to the barrel of the firearm for generating a laser beam when the firearm is triggered. Modern laser units, such as the Small Arms Transmitter (SAT) from Saab Training Systems, are also often arranged to communicate wirelessly with an information collection unit carried by each participant of the laser-based military training exercise. All firing events may then be transmitted to the information collection unit and can subsequently be used during exercise evaluation.
In order to determine when the laser beam shall be generated, the fire shot event, i.e. the event of a user activating the triggering mechanism of the firearm, has to be detected by the laser unit. Normally, the occurrence of a fire shot event is established by determining when the explosion caused by the blank cartridge has taken place. There are mainly three detection principles used in the art for establishing the occurrence of such an explosion: flame detection, sound detection, and shock detection.
The principle of flame detection utilizes the muzzle flame generated by the exploded cartridge to detect the fire shot event. By equipping the laser unit with an IR sensor that measures the intensity of the flame, the laser unit can establish that a fire shot event has taken place in case the measured intensity value exceeds a predetermined threshold value.
The principle of sound detection utilizes the sound generated by the explosion of a cartridge to detect the fire shot event. The laser unit may in this case be equipped with a microphone and if the sound level registered by the microphone exceeds a predefined limit, a fire shot event is assumed to have taken place.
The principle of shock detection utilizes the shock caused by the exploded cartridge to detect the fire shot event. By measuring the acceleration of the firearm caused by the exploded cartridge with an accelerometer disposed in the laser unit, a fire shot event can be established if the acceleration of the firearm exceeds a predefined value.
All three of the above principles hence use an absolute limit for a measured physical quantity and when the signal measured by a suitable sensor in the laser unit exceeds said limit, the occurrence of a fire shot event in the firearm is “proved” and the laser unit generates a laser beam emulating a fire shot.
All the detection principles explained above suffer from drawbacks.
For example, there is training ammunition which does not cause any muzzle flame when fired. This renders the flame detection principle useless. Furthermore, shooting in cold weather decreases the intensity of the muzzle flame making the flame detection principle uncertain. Although the sound detection principle and the shock detection principle may be used with non-flame generating ammunition, these principles are also prone to errors resulting in high false detection rate. When using the sound detection principle, it is hard to determine whether a sonic boom is caused by the explosion of a blank cartridge in a particular firearm, or caused by something else in the immediate surroundings of said firearm. As a result, a fire shot event may be falsely detected and a laser beam generated by a laser unit mounted on a firearm in the proximity of, e.g., another firearm being fired. The high false detection rate when using the shock detection principle is due to the fact that the firearm is often exerted to heavy acceleration whenever it is bumped against something. Each time the acceleration registered by the accelerometer in the laser unit exceeds the predefined threshold value, the bump will erroneously be considered as a fire shot event in the firearm and a laser beam will be generated. During military training exercises, the firearm is often subject to rough handling, leading to frequent detection of such false fire shot events.
Furthermore, all the above detection principles invite the military trainees to “cheat” during military exercises. When using the flame or sound detection principle the military trainees can fool the laser unit to produce a laser beam by simply directing a light emitting or sound producing device towards the pertinent sensor of the shot detection device. Each time the intensity of the emitted light or the produced sound exceeds the predetermined threshold value the laser unit generates a laser beam. Thereby, the military trainees obtain an endless supply of “ammunition”. When using the shock detection principle, the same is achieved by bumping the firearm against any accessible object, or simply tapping the laser unit.
To make cheating more difficult and to provide a more robust detection, two or all of the above detection principles are often combined. This, however, makes the laser unit bigger, more power consuming and more expensive.