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Chris Farris
TEAM SWFA - Admin swfa.com Joined: October/01/2003 Location: Texas Status: Offline Points: 8024 |
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Posted: October/26/2005 at 17:13 |
Click here to see a simulation of an EOTech sight in action
In hostile environments it is often essential to remain undetectable to the enemy. Stealth maneuvers deliver a huge tactical advantage and provide a force multiplier in a great deal of hostile situations. The tools operators deploy with should also remain stealth, including their electronic weapon optics. Elimination of any muzzle side, position revealing signature is key in remaining unexposed. The HWS provides a huge advantage here. It is one of most covert electronic sights on the market today, and provides distinct advantages over the conventional red dot sighting systems.
Figure 1:Muzzle side signature images of the HWS
This muzzle side, position revealing signature can come in 3 core areas:
• Light emitting or escaping.• Reflective glare from optical surfaces.• Audible noise from manual operation of the weapon sight.
Light escaping signature: Relating to signature, all red dot sights have a fundamental optical design flaw. The LED light source is pointed downrange, toward the objective lens and unfortunately, the enemy. In a day light environment this is difficult to pick up, but in night vision situations the forward projecting LED can be seen as a beacon at certain viewing angles. Obviously this is not desirable and can greatly increase the chance of incoming fire. Conversely, the HWS’s optical design contains all of the light within its optical core and the main housing of the sight’s body. (see figure 2). No forward projected light is emitted that can be viewed. While in the NV mode of operation, the HWS offers no position revealing signature, even to adversaries searching with night vision devices. The HWS is a completely passive weapon sight, a most important feature for today’s operators. Figure 1 clearly shows this, displaying both a C-More red dot optic and an HWS in a side by side comparison. This is viewed through an ITT PVS14 night vision system at a distance of 10 feet away from the muzzle side. We think this is a vitally important comparison to note.
Figure 2: Cross section of HWS
Reflective Glare signature: A lot of optical devices such as binoculars and rifle scopes have curved, convex shaped optical surfaces on their muzzle side lenses. To improve viewing performance it is also common that a highly reflective coating is applied to these surfaces. Red dot sights are no different and also need a highly reflective red coating on the objective lens, allowing the “dot” to appear at the target scene. This coating is required and is fundamental to a red dot sight’s operation. One main disadvantage to this older technology is that light can reflect off these optical surfaces and create a “kick back” optical reflection that can give away the operators position. Variations of this light can include any white lights, street lights, or most commonly sun light.
To combat this, a user deploys with an anti-reflective device (ARD), which is a black, non reflective “honeycomb” piece sometimes called a “kill flash” filter (see figure 3). These filters are manually screwed on to the objective lens of the optic by the operator in the field, each time the situation or environment requires it. These filters will do the job and eliminate the reflective glare but will also add to other problems in tactical field operations. First, the user will lose a minimum of 15% light loss. This may not be an issue during the day, but in low light or dark situations, it will significantly darken the target scene making it more difficult to identify potential threats. Secondly, the ARD’s honeycombed cell design can easily collect dirt, snow or mud that can block the viewing aperature. This design is much like a cheese grader and is a natural magnet for these elements. If the holes get filled, an operator will be unable to see through it to effectively acquire and engage his targets. Lastly, this device can add around $30-50 in cost per unit and the soldier must carry this extra piece and instantly attach or remove it when the environment changes. To eliminate this or the possibility of losing this piece, a permanent solution integrated into the sight is more reliable and effective in today’s ever-changing urban battlefield.
Figure 3: Anti-reflective device
In contrast, the HWS eliminates any reflective glare signature issue through its core optical design, and solves this on a permanent basis, where the operator does not need to add or take off filters. The optical design incorporates flat, distortion free viewing windows. A permanent anti reflective coating is applied to all exposed optical surfaces with no degradation to light loss. The HWS retains a photopic light transmission of about 90% across its entire viewing window. The optical surfaces are impervious to reflective glare signature; therefore, the HWS does NOT need these external “kill flash” filters.
Audible Signature: It is also crucial that an operator and his equipment remain free of audible signature. This includes even the smallest of noises that can give away their position or heighten their vulnerability. Most red dot systems incorporate a mechanical dial type knob to control the brightness intensity of the reticle. This configuration forces the operator to manually turn the knob, creating an audible click as it passes each brightness setting. Also, it is vital for an operator to instantly adapt to changing environments. When seconds count, he cannot afford to manually dial down from a bright level to a night vision level to complete his mission. & |
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