Optic Information
Introduction:
There are many different configurations of night vision optics out there today. Those who have more experience with these devices will be more familiar with the terminology used in the night vision industry. I wanted to designate a portion of this site to those who do not have as much, if any experience with night vision devices, as a way for those who want to learn more to be able to do so. When I started BHO, I wanted to establish a company that is as transparent and straight forward as possible. In addition, I want to provide as much information as possible on the subject, so that anyone with the desire to purchase night vision will have all the relevant information at their fingertips. When researching night vision you can find a lot of varying opinions and even downright deceitful information out there. Here at BHO, we want our customers to make the most informed decision possible when placing an order with us. I am hoping that the topics discussed on this page will assist in furthering your understanding of night vision. If you have any specific questions that are not discussed here, send us an e-mail at brickhouseoptics@gmail.com.
When you hear the words night vision, or "nods," the first image that comes to the mind of most people are those quad tube panoramic GPNVG's made by L3. Night vision gets a lot of its hype from movies and video games; because of this, any time someone hears night vision or "nods" it can be difficult to separate fact from fiction. Night vision is not going to allow you to see at night the same way you would see in the daytime. In the daytime, we have the sun that gives us all the light we need to see clearly, at night we need the light to come from the moon and stars. For night vision to function, there has to be some level of light present. Light levels are measured in degrees of luminosity. During the day this means very little, but at night, the level of light, or luminosity, can be affected by the moon's cycle, cloud cover, smoke, elevation or location. Night vision will assist in magnifying existing light in the environment, and through the image intensifier, it will be presented to your eye for decoding.
There are a vast number of factors that affect night vision. Depending upon where you are using your night vision, you may run into man made obstacles like artificial light (car lights, streetlights, business billboards or flashlights); apart from these, nature can present its own challenges in the form of weather (cloud cover, snow, rain and fog). Anything that alters light in anyway is a variable to night vision users and should be taken into consideration when choosing a platform. In the pictures above, I have illustrated the three big categories of night vision that currently exist in the market (GPNVG, PVS-14, and PVS-31). Listed below is a discussion of each model and the prominent features of those platforms.
Optic Configuration: AN/PVS-14A
At Brick House Optics, we carry a stock of AN/PVS-14A (PVS-14) optics. This is a single tube night vision device that can be seen in the image to the right/above. Its image rendering capabilities rely upon its objective lens,
image intensifier and a diopter. Its structural parts include battery and image intensifier housings, as well as a manual gain adjustment knob, power switch and IR illuminator window. Most PVS-14 configurations run off of a single AA Lithium battery. Understanding this platform will give you a firm foundation moving forward with your pursuit of night vision.
This straightforward, single tube device is the backbone of modern night vision. The PVS-14 is one of the most reliable night vision platforms on the market to date. As a single tube, night vision aperture, it boasts more versatility than other designs. The single tube design allows it to work as a handheld, weapon-mounted, or helmet-mounted device. To mount the PVS-14 to a helmet requires a mounting setup specific for helmets. In addition, to mount this optic to a rifle, a completely separate rifle mount is required. Examples of helmet and rifle mounts can be found on our site in the product section.
FIGURE 1
Gain Adjustment
Objective Lens
Battery Box
IR Light Emitter
Battery Cap
FIGURE 2
Power Switch
Eye Cup
Diopter
Lanyard Attachment
When looking at the PVS-14 from tip to tail, the front of the optic starts with the objective lens pictured in Figure 1. This connects to the optic housing and battery compartment. The objective lens allows the user to adjust the site picture to their eye. In addition, the gain adjustment and diopter also serve as adjustable features to your site picture. Even though all three components allow you to adjust the optic to your eye, there are differences in their functions. The objective lens adjustment is designed to adjust the quality of the object that you are looking at. It accomplishes this by capturing the greatest amount of available light and provides it to the image intensifier. The image intensifier then renders the image to your eye. If the image is still too dim or too bright, you can adjust this aspect of the image quality by tuning the gain adjustment knob pictured in Figure 1. Adjusting this feature of the optic will adjust its sensitivity to light. If the image needs further adjustment, the diopter adjusts the sharpness of the image intensifier screen. You should adjust the diopter to a setting that creates the sharpest image for your eye. In its entirety, you must adjust all three components to obtain the clearest site picture possible. This process will allow you to customize your device to your vision needs.
Night vision is designed to work in environments with low luminosity (i.e. moon and stars). However, there are certain environmental conditions that eliminate or severely limit the available light to be enhanced. For this reason, IR light emitters are necessary to the basic function of night vision devices. The PVS-14 possesses an infrared light emitter for environments that have little to no light. The IR emitter is pictured in Figure 1. To turn the IR emitter on or off, you would use the power switch pictured in Figure 2. The IR light emitter produces infrared light up to 3 meters to aid in extreme lightless conditions. This IR emitter function is great for use in environments such as a home or office space.
A word of caution to anyone operating night vision for the first time: ANY extreme light or laser exposure will damage your device. This means, no fluorescent lighting, no daylight conditions, no nighttime laser tag, or other such shenanigans. When you test or adjust your optic it should be done in an appropriate setting with suitable lighting conditions. Do NOT test your optic by turning it on in a room with the light still on.
Optic Configuration: PVS-31
The PVS-31 optic pictured is a dual tube configuration. Dual tube platforms have the same structural components as the PVS-14 model discussed above. However, the way that those components are laid out will depend upon the configuration that you choose. There are a couple of different ways
that you can accomplish dual tube configurations. In the picture above, the dual tube unit uses two night vision tubes that have been connected with a powered bridge mount. This means that both tubes utilize the same power source, the same IR source, and the same mounting platform (which is the way that they attach to the helmet mount).
There are powered and unpowered bridges that allow for a number of dual tube configurations. A powered bridge is one that shares a singular power source, a singular gain adjustment knob, and a singular IR emitter between the two adjustment tubes. In addition, a powered bridge has the ability to extend the optics run-time with an increased battery capacity achieved through a battery pack. An unpowered bridge is one that allows the tubes to be mounted together while maintaining their own independent adjustments for power, gain adjustment, and IR light source. Thus, it is possible to take two PVS-14s and mount them to a bridge to achieve a dual tube configuration. In this type of configuration then, you would have to adjust each tube independently of the other. There also exists a subset of unpowered bridge mounts termed pano-bridges, these allow for independent tubes to be attached together and angled to achieve a wider viewing angle.
As you can see, there are a number of ways you can achieve a dual tube configuration. Each configuration will have its own host of advantages and disadvantages. It is important to note though that what might be considered an advantage to one person, may be considered a disadvantage to another. When it comes down to night vision, it is all about personal preference. What your desired outcome is has to be balanced with what your budget will allow, what your visual needs are, as well as your own environmental needs. The nice thing about night vision though is that you can always adjust or adapt your configuration as you determine your own preferences.
If your budget allows for dual tubes, they do offer a host of benefits that make them an appealing option. Dual tubes, when compared to single monocular tubes like the PVS-14, are more accurately balanced and distribute weight more evenly, thus limiting fatigue during use. However, the configuration you choose for your dual tubes will affect how well the unit distributes weight. The powered bridge dual tube design is more often than not configured with a battery pack that sits at the rear of the helmet. This configuration distributes the weight in a more balanced manner across the mounting apparatus. In comparison, in a configuration involving two PVS-14s, the weight sits in the front of the helmet exclusively. This means, that without adding a counterweight to the rear of the helmet, an individual using this configuration may experience premature fatigue based on weight. Again, this is all preferences. For some individuals whom might wear their optic minimally, this might not even matter to them.
Optic Configuration: GPNVG
The quad tube ground panoramic night vision goggles from L3 Harris Technologies, is arguably the pinnacle of night vision to date. The GPNVGs feature an unmatched 97 degree field of view compared to the 40 degree view achieve by traditional single and dual tube optics. With a $40,000 price tag,
this is easy to understand. The advantages that this optic offers focus upon greater situational awareness and additional operating capacity. Having a greater field of view, will always be an advantage. The increased field of view this optic affords is accomplished through a technology that is akin to a prism. It combines the center tube with the exterior tube in each section to create an overlapping display. This means that even though there four tubes, there are only two displays for your eyes to view. Despite the hype behind the quad tube design, the fundamental functions of the optic remain the same. If interlocking sectors of fire and team operations are not part of your plan, this may fall outside of your needs. That being said, there is no one on this planet that would turn down an affordable pair of these nods.
Optic Modifications:
Not only are there a wide variety of optic platform choices for an individual to choose from, there also exists a large number of modification technology that can be coupled with your optic as well. This modification technology encompasses lights, lasers, power-packs, magnification, and thermal enhancements. Each of these potential modifications brings with it a distinctive benefit, that when coupled with your optic set-up, expands your capabilities.
Lights:
Coupling a flashlight with night vision may seem counterintuitive based on our previous discussion about optic lighting sensitivities. However, your optic will work extremely well when couple with an IR capable flashlight. The key here is that we are talking about an IR capable flashlight and NOT a regular white light flashlight. You still want to avoid shining the light into your optic. DON'T look into a mirror and
turn the light towards yourself. This may still result in damage to your optic. While you cannot see IR light with the naked eye, it is perceivable under night vision enhancement. These lights are used to illuminate your environment when the situation requires more illumination than the 3 meters your standard IR light is capable of producing. This means, if you are trying to find animals in the dark, or trying to identify targets while not alerting them to your presence, the IR spectrum flashlight is an invaluable tool. It is important to note though, that this particular modification does not attach directly to your optic. This tool is attached to your weapon system and activated either directly by manipulating the flashlight itself, or by using a remote pressure switch.
Lasers:
A laser modification to your optic set-up allows you to aim faster than you would otherwise be able to if you utilized a red dot or scope. This simultaneously acts as a faster aiming device, it also allows you draw attention to a point of interest if you are working in a group. Just like the light modification above, a laser modification is also not attached directly to your optic. Instead, the laser is attached to your weapon system.
Power Packs:
Power packs (battery packs) allow you to enhance the overall capacity of your optic's operating ability by providing more power and a longer overall run time to your optic. They serve the dual function of providing power, as well as a counterweight when utilizing a helmet mounted optic setup. You would only use a power pack if you are utilizing a helmet mounted system. Power packs are connected to your optic through a power cord.
Magnification:
Optic magnification can be achieved in a multitude of ways. Night vision optics utilize a 1x magnification as their default. One way this can be modified is by coupling the optic with a secondary magnification unit. Currently, there exists 3x, and 5x additional magnification units. Either of these additional magnification units can be attached to the front of the night vision device by directly threading it into
the front focal lens. You can also achieve greater optic magnification with the use of a scope. By mounting the night vision device behind a scope, you can take advantage of the magnification properties of that scope.
Thermal:
Thermal technology is another one of those per your preference type of modifications. Some individuals love it, others prefer not to use it. Thermal optics allow you to broaden the visible spectrum available to your optic. Thermal technology allows you to see the heat signature of your surroundings. This will allow you to pick out living targets in absolute darkness and in conditions that would hamper traditional night vision. This also includes the ability to detect slight heat signatures, such as animals or vehicle tracks. Thermal devices come in many forms. They can come in the form of a specific device that may attach to the bridge and replace one of the night vision tubes of your optic. The AGM pictured in this section is capable of performing that function. Thermal optics may also take the form of a clip-on attachment (the Ecoti image pictured is an example of a clip-on attachment). Finally, you may also find it necessary to use a thermal scope in certain circumstances (for example the Steiner and Sig Sauer thermal scopes). Ultimately, your personal preference dictates everything. Thermal optics have their own strengths and weaknesses. There is hot debate about the efficacy of combining thermal technology with night vision technology. Some people report issues relating to the refresh rate of current gen thermal technology, while others state that the two technologies compete and they have a hard time focusing between the two. Other users report no such issues on either front.
Image Intensifiers:
Image intensifiers are the heart of night vision systems. Good image intensifiers are not cheap and cheap image intensifiers are not good. That saying is at the heart of all night vision purchases. The average cost for an image intensifier tube, independent of all other costs associated with the optic, is $2,000. Some optics contain generation 1 or generation 2 image intensifiers. They will be cheaper than generation 3 image intensifiers because they are older technology. It is important for you to understand the technology in your optic so that you know what you are purchasing. I have had numerous individuals reach out to me trying to discuss optics they have acquired from others because the optic is not performing to their expectations. Most of the these individuals do not understand FoM (Figure of Merit), SNR (Signal to Noise Ratio), RES (Resolution LP/MM), Halo, or EBI (Equivalent Background Illumination) parameters. This means that when they purchase an optic, they often envision one thing, and then are disappointed to find that they bought another. Most of the time, some of the specs associated with an image intensifier are listed on the site you are purchasing the optic, or image intensifier, from. However, other specs, like FoM information will have to be specifically requested. The problem is, most people do not know the lingo listed, or how to interpret the specs displayed for the unit. Having an understanding of this information is important before making an optic purchase.
To aid in your understanding of the following discussion, we need to clearly define the terminology used within the night vision community in reference to image intensifiers. Below are terms relevant for your understanding:
Resolution (LP/MM): This number represents the image intensifier's ability to differentiate objects in close proximity. This will be listed as center resolution more often than not. This tells us how well an image is seen in the center of the optic. The average number for resolution is approximately 65. However, newer tubes are producing higher numbers in the mid-70s and early 80s. This poses an issue as the higher resolution numbers make up for lower SNR numbers and can produce a higher FoM number with poor performance overall. If your resolution number is lower than 65, and your SNR number is lower than 25, your optic will have issue with objective focus. The low SNR will increase static/scintillation distortion in your field of view.
Signal to Noise Ratio (SNR): The SNR figure represents the amount of noise or static that can occur in the optic depending on light conditions. To gain a better picture of what this noise or static represents, think of the grainy image resolution that was tied to old movies. Now, compare that grainy resolution to Blue-ray DVDs made today. This hazier image quality is a big deal when you are using an optic to see at night. A quality SNR number is a matter of personal preference though and differs from individual to individual. However, in my experience, image intensifiers possessing a SNR number lower than 25 have a noticeable performance degradation. A good SNR is usually anything above 30.
Figure of Merit (FoM): When looking at a spec sheet for the image intensifier, the FoM number is calculated as Resolution x SNR. The FoM number is intended to be an overall representation of the image intensifier's performance. It is the culmination of the image intensifier's resolution and signal to noise capabilities. A higher FoM number is meant to indicate better image quality. However, as I will illustrate below, it is more important to know the individual SNR and resolutions figures.
When browsing for night vision, more often than not, you run across optics being sold that tout a high FoM number. Little data is provided aside from this number. This creates a level of confusion for anyone that does not know what they are looking for. This practice ignores crucial pieces of data, such as signal to noise ratio and resolution rate. The resolution and SNR numbers are crucial to determining the performance of the image intensifier. It is possible to acquire image intensifiers that possess similar FoM ratings that produce drastically different performance results. For example, a FoM tube with a rating of 2,200 could mean a resolution rate of 81 and a SNR of 27.16. This is a higher than normal resolution rate and a standard SNR rate. You can compare this to an image intensifier possessing a 2,200 FoM rating consisting of a resolution rate of 73 and a SNR rate of 30.13. The two tubes having the same FoM will give drastically different results. The lower resolution but higher SNR tube will produce significantly greater results. The image resolution maybe higher in the first tube, but the distortion of that image by the available light renders the higher resolution advantage, mute. The lower resolution image displayed in the second example will have less static corruption and will therefore be more functional than its counterpart.
In another example, you might have an optic that has a resolution rate of 81 and a low SNR number of 24, which yields a FoM number of 1,944. Now compare this optic to an optic that has a 67 resolution and a 29 SNR, you end up with a 1,943 FoM. In this case, the second optic will outperform the first despite the fact that the FoM number is lower for the second optic. This is because the resolution and SNR numbers are better balanced in the second optic. As you can see, the SNR is one of the most valuable figures you can look at when searching for a quality image intensifier. The FoM number alone should not be your only focus for consideration.
Equivalent Background Illumination (EBI): This figure illustrates how accurately your image intensifier tube can form images in low light conditions. The lower the EBI number, the better. EBI is effected by temperature; lower weather inhibits EBI and colder weather enhances EBI. EBI is crucial if you are going to be working in extremely dark environments (in the woods, at night, in heavy cloud cover). This number is provided on the spec sheet provided with your image intensifier. An EBI of 2 or below is considered to be good. An EBI of 2.1 or above is not desirable.
Luminous Gain: (aka brightness gain) This represents the number of times the image intensifier can multiply the light that it is exposed to. A good range is anything above 70,000. A medium range is between 60,000-70,000. A poor performing image intensifier will have anything below 60,000.
Halo: When you look through your optic, a halo is the bloom effect that occurs in your optic image around a light source. The halo metric should be below 1 on your spec sheet. The lower the halo number the better. The halo number can mean the difference between a light blooming to the size of a baseball or a beachball in your image.
Photocathode Sensitivity (response): This number indicates the image intensifier's efficiency in converting light. The higher the number, the more efficient your image intensifier is. The best range would be 2,200 and above. A mid-range would be 1,800- 2,200. Anything below 1,800 would be undesirable.
Mill-spec: Calling an image intensifier mill-spec implies that it meets the minimum specs outlined in the Omni contract. This means that image intensifiers labeled as mill-spec meet a mandated level of minimal performance. Most often, you will see retailers say mill-spec in place of saying Omni VIII minimums. For example, the mill-spec Omni VIII minimums currently are 1,600 FoM (64 resolution, 25 SNR), photocathode 2,000, EBI 3.0, gain 25,000-110,000, and halo 1.0. Given, these specifications compared to what I have said above with respect to EBI, you can see that the term mill-spec does not mean that an image intensifier is better. This term is not something that you will see on your image intensifier spec sheet. It is a designation that is used for marketing purposes by whatever retailer you are getting your image intensifier or optic from and may be listed in the product description.
Commercial: This term represents all image intensifiers that do no meet the Omni VIII standards. This term is not something that you will see on your image intensifier spec sheet. It is a designation that is used for marketing purposes by whatever retailer you are getting your image intensifier or optic from and may be listed in the product description.
Spots: (aka "blems" or blemishes) Your spec sheets will disclose any spots that may be present in the image intensifiers you are purchasing. Your image intensifier field of view is broken down into three zones that resemble the structure of your eye. Zone 1 is at the absolute center of the optic image. Zone 2 is between the absolute center and the outer ring. Zone 3 is between zone 2 and the wall of your optic. You will often see image intensifiers listed with a spot or blem designation. Depending on the location of the blemish, or spot, will dictate the discount you will receive when purchasing it. Spots can occur in any zone and in any size. A spot in zone 3 is better than a spot in zone 1. Mill-spec requirements are more restrictive with respect to the spots that can be present in an image intensifier. The mill-spec requirements dictate that there are fewer spots present than what may be found in commercial grade image intensifiers. The spec sheet for your image intensifier will tell you if there are any spots present in the image intensifier you are buying and what zones those spots are found in. This is why it is important for you to see the spec sheet for your image intensifier prior to purchasing the intensifier, or your optic.
At BHO, we do everything we can to avoid using any tubes with any spots. We figure that if your are going to spend thousands of dollars on a piece of equipment, it should be defect free. I have seen so many individuals dissatisfied with their optic purchase because they did not know that the optic they were purchasing came with an image intensifier that had blemishes. Again, this is why it is important for you to see and understand the spec sheet associated with your image intensifier.
Night Vision Categories:
In general, image intensifiers fall into two categories: 1. green phosphorus, and 2. white phosphorus. Image intensifiers are further delineated into filmed, thin-filmed, and unfilmed categories. Each of the terms discussed above apply to image intensifiers regardless of phosphorus color or film. A green phosphorus image intensifier renders a neon green color when it displays an image. A white phosphorus image intensifier displays an image with a muted blue hue. Both green and white image intensifiers can be filmed, thin-filmed, or unfilmed.
When you talk about filmed vs. unfilmed technology, what you are talking about is the ion barrier technology incorporated within the image intensifier tube. The ion barrier film is in place to protect the Micro Channel Plate (MCP) from stray ions during the light conversion and amplification process. As image intensifier technology has progressed, the ion barrier film has become no longer necessary. Filmed or unfilmed image intensifiers function in much the same way with similar lifespans. It is cheaper for manufacturers to produce filmed image intensifiers. However, the performance of the unfilmed image intensifier renders a brighter performing optic with a higher image quality. The decision of whether to buy a filmed vs. an unfilmed optic centers on personal preference and budgetary constraint. Unfilmed image intensifiers are going to be more expensive because of the technology involved. Some individuals do not like how bright the image is rendered with an unfilmed image intensifier so they opt for a thin-filmed or filmed option depending on their personal preference.
The pinnacle of image intensifier technology is the white phosphorus, unfilmed image intensifier. This may not be the case in your personal experience. The industry though says white is better than green because the white phosphorus image intensifier is supposed to alleviate eye strain under prolonged use. Unfilmed image intensifiers are the most sought after because of their incredible performance in extreme low light conditions (i.e. forests, fields, marshes, and swamps). The unfilmed image intensifier amplifies light more efficiently in worse conditions than its traditional filmed or thin-filmed counter parts. However, some individuals may not have a need for unfilmed image intensifiers in their optic. Even though unfilmed image intensifiers are sought after, individuals who live in urban or sub-urban environments may find the unfilmed technology to present unique challenges. Due to the nature of the technology, hypersensitivity can cause excessive halo or bloom in the image the optic renders. This is something to be mindful of when you are choosing an image intensifier. Your specific circumstances may dictate your decision on this topic.
Optic Cleaning, Maintenance, and Storage:
Night vision optics can represent pretty expensive pieces of equipment. Just like with anything else, to make it last, it is important to take care of it. The internal components of night vision are extremely sensitive to debris and humidity. These are the hardest things to control in the average environment. This is why there is such a strong warning against disassembling the optic as it allows contaminants to enter the body of the optic and possibly damage the sensitive components within. However, you do need to take certain steps to maintain your optic's functionality. You should not disassemble your optic in any way to clean it outside of the disassembly needed to clean/replace your demist shield or sacrificial window. Your optic was sealed and purged before shipping, and any disassembly of your optic beyond the sacrificial window or demist shield will result in optic damage, or any warranties that may have been provided with your optic becoming void.
The external surfaces of the optic may be cleaned using canned air or a wet Q-tip and a lint free cloth. If necessary, a very lightly damp cloth may be used. Your demist shield and sacrificial window may both be cleaned with a wet Q-tip and a lint free cloth. Major debris can be removed with canned air.
CAUTION: DO NOT USE AN OVERTLY WET CLOTH AS IT MAY ALLOW EXCESSIVE MOISTURE AND DEBRIS TO MAKE CONTACT WITH EITHER LENSE, OR IT MAY PUSH DEBRIS INTO THE THREADED HELMET MOUNT ON THE HOUSING CASE. THIS MAY DAMAGE YOUR OPTIC.
CAUTION: DO NOT PUT ANY WATER, DEBRIS OR CLENSER ON THE DIOPTER OR OBJECTIVE LENS. THESE AREAS SHOULD BE CLEANED WITH A LENS BRUSH, OR A SCOPE BRUSH AND A LINT FREE CLOTH. THESE ACTIONS SHOULD ONLY BE PERFORMED IF THE LENS IS FREE FROM DEBRIS OR POSSIBLE DAMAGE MAY OCCUR. THIS MAY ALSO VOID ANY WARRANTIES THAT MIGHT HAVE BEEN PROVIDED WITH YOUR OPTIC.
CAUTION: DO NOT USE ANY CLEANERS ON YOUR OPTIC (THIS INCLUDES GLASS CLEANERS).
Storage Methods:
Properly storing your night vision optic is critical to its longevity and function. Ensuring that the optic is stored in a cool, dry place, away from children and animals is best. It is also important to make sure that your optic has been cleaned prior to storage. Make sure that any moisture on your optic has dried or been removed before storing it. It is also important to make sure that your optic has been turned off prior to storage or battery removal.
When storing your optic after use, make sure to remove the battery. Once the battery is removed, check it for signs of wear or damage. If the battery is damaged, or looks sub-optimal, discard it per manufacturer instructions.
WARNING: DO NOT STORE ANY BATTERIES IN YOUR OPTIC WHEN IT IS NOT IN USE.
