RAZOR VISION: Vortex Razor Uh-1 Holographic Sight
The Vortex Razor AMG UH-1 offers a holographic 65 MOA circle and 1 MOA center dot reticle that is renowned for speed. To address the short battery life inherent in holographic sights, Vortex integrated on-mount recharging. This article explores its electrical and optical properties, as well as its improvements upon iron sights.
A holographic sight differs from a red dot sight in its ability to present complex reticles using a laser diode; the latter can only reflect the dot of a light emitting diode (LED) into the eye of the user. The optical implications of this fundamental difference are reserved for a later section, while the battery life ramifications are discussed here. The laser diode of a holographic sight draws considerably more power than an LED. Red dot sight battery life can be measured in years, while holographic sight battery life can be measured in hundreds of hours.
To address this, Vortex integrated on-mount charging capability for the UH-1. A Micro-B USB cable can be connected to the mount to recharge LFP123A batteries when indicated by a flashing reticle. Internal circuits prevent accidental charging of CR123A batteries. In the absence of a battery, the sight can be used with only USB power. The expected battery life of lithium CR123A is 1,600 hours and 800 hours for the rechargeable LFP123A. The battery is placed transverse to avoid stressing the contact springs with recoil forces.
Lastly, the UH-1 is equipped with a 14-hour auto shutoff, which the user can disable. This feature complements a nightstand firearm from dusk till dawn. The reticle can be turned on before bed and remains ready throughout the night, while the 14-hour timer conserves the battery should the user forget to power down the UH-1. The USB port has all five pins and can be used by the manufacturer to perform diagnostics, although there are no plans to interface with other electronics.
The UH-1 has a built-in, lower one-third co-witness Picatinny rail mount that places the reticle above the front sight post of an AR-15 rifle. The quick-detach mount is secured with one lug and clamping pressure is applied via a locking lever. The right side features the Micro-B USB charging port and coin-slotted reticle adjustment dials. Although the adjustments are neither recessed nor locking, the author did not experience accidental alterations. The left side contains a lanyard-retained battery cap while the rear presents two brightness-adjustment push buttons that can be depressed together to power down the sight.
The UH-1 measures 5.3cm wide (including the battery cap), 5.8cm tall, 9.3cm long and weighs 340 grams. While the sight is somewhat oversized for a compact firearm, like the MP5K, it balances perfectly on an AR-15 rifle.
The UH-1 features a 65 MOA circle and 1 MOA dot reticle similar to the EOTech pattern, with the notable exception that Vortex features a triangle at the 6 o’clock position for use as a holdover mark inside 10m. When using red dot sights, the author has occasionally forgotten to aim at the hairline for a centered headshot; he found the triangle of the UH-1 to be a useful reminder. And, unlike a red dot sight, the finesse of the holographic center dot is limited only by the user’s visual acuity. This fine point of aim is helpful against small and distant targets. When used with both eyes open, the UH-1 housing disappears to give an unobstructed view.
The reticle brightness has fifteen levels of adjustments but is incompatible with night-vision equipment. The default brightness level at power-on is appropriate for use indoors and under artificial lighting, but it is too bright for a moonless night. This is useful for a nightstand firearm should the user choose to only activate the sight when required. With the reticle adjusted too brightly, the author observed blooming as well as two additional ghost reticles above and below, but the reticle remained useable.
It is normal to perceive a grainy reticle due to the construction of the human retina. The centered position of the reticle excites the cone cells—each of which is responsive only to short (blue), medium (green) or long (red) wavelengths. As the reticle is red and only excites a portion of the cones, this leads to a perceived grainy image. The degree of pixilation differs from user to user as both the numerical and positional distributions of the cones are unique and vary among the population.
As previously discussed, the UH-1 presents a hologram reticle with the collimated illumination of a laser diode. Since a hologram is recorded as the interference pattern between a light source (often planar waves) and the reflections of the object illuminated by the same light source, the reconstructed image has less polarity diversity than that found in the natural world. The author found his polarized sunglasses negatively interfered with the reticle such that some parts appeared dim. To explain this effect, assume the light source (sight) and filter (sunglasses) are linearly polarized and 90-degrees apart in slant. No energy can pass the filter, as the dot product is zero.
The author observed pockets of null primarily on the left side of the view window where the reticle is very dim; this effect does not change with eye relief. Since only the reticle is polarized, the worldview remains unaffected. It is important to note that this polarization interference effect is inherent in the design of holographic sights and the effect is dependent on the polarization slant of the sunglasses.
Holographic sights possess superior optical quality, and the Vortex UH-1 is no exception. A red dot sight requires a coating on the objective lens, tuned to the LED wavelength, to reflect the reticle into the eye. The reflecting glass must also be concave, to place the LED at the optical center. This impacts the image quality, as the coating costs transmission efficiency and the concave lens can create distortions. A holographic sight has neither of these defects. The UH-1 has no detectable color cast in use, with only a slight blue-green tint under close inspection against a white background and no discernible optical distortion. The UH-1 is a good example of the superb optical quality of the holographic design.
To quantify the speed advantage of a holographic sight over traditional iron sights, the author timed himself shooting a rack of six, six-inch diameter plates at 15 yards with an MP5K-PDW. Three repetitions were made with the UH-1 and three with the notch-and-post iron sights. The results in seconds are tabulated below as averages. 2s (95-percent confidence) data is presented in brackets.
The Vortex UH-1 marginally improved the first shot and split times, which combined to significantly improve the total time by 20 percent. The author experienced natural lateral alignment with the iron sights but still needed to consciously perform vertical alignment. With the UH-1, the author practically performed a continuous sweep and fired as the reticle swept past the plate. The large view window allowed one to easily find the reticle, and it better tolerated head-position errors. This combination of advantages provided a discernible improvement over the iron sights.
The Vortex UH-1 is an optically superb holographic sight with worthwhile improvements to the renowned circle dot reticle. The integrated mount is set at the popular lower one-third co-witness height. The short battery life inherent in the laser design is mitigated with the integrated Micro-B USB charging port. The default brightness upon powering on and the optional 14-hour automatic shutoff are well suited for use on a nightstand firearm. The Vortex UH-1 presents a well-integrated sighting package that vastly improves the target engagement speed.