CARE AND FEEDING OF LAW ENFORCEMENT ELECTRONICS
Tips on use and maintenance for best performance and longest life
Part Two of Two
As is becoming traditional, here are this issue's words of wisdom offered for your edification and amusement:
"Of all the statues in all the cities,
One must be in a certain frame of mind to sit down and crank out a quality article. If that particular mental state doesn't exist, an author can no more force it than he can force a urine sample that doesn't want to happen.
See Spot run.
Most agencies have budget problems. Doesn't it make the most sense, then, to get the maximum performance and life out of the equipment you fought so hard to get in the first place? On top of which, the jobs this stuff is supposed to do for you tend to be important. Why, then, do so many agencies treat their equipment as if they were mad at it?
This month we'll discuss night vision equipment. There's a lot of grant money running around and several thousand pieces a year are being purchased by police agencies. Judging by the feedback we get from users, most agencies don't have much understanding of what makes these things tick. For the most part, night vision is fairly rugged, but can be destroyed in an instant by innocent mishandling. Next issue we'll cover night vision in great detail. But for now let's get back to care and feeding.
The number one thing to remember about night vision is that they can, and likely will, be damaged by too much light. The amplification of a top grade image intensifier (the tube that does all the work in a night vision device) might be 50,000 to 60,000 times. Remember this: do not ever (never!) turn on a night vision device unless it is in very low light. Daylight or even bright office light can damage the device beyond repair - and damage it in a fraction of a second. We don't even like to see lens caps taken off in the light.
The equipment also can be damaged by someone turning a headlight on or by some such other bright light appearing in the field of vision of a scene under observation. Be aware of this possibility, try to anticipate such, and be prepared to take action if it happens. We have found that bright images are less likely to burn themselves into the tube if you keep the night vision device constantly moving. You don't have to move it much, but at least every minute or so shift the thing slightly a few degrees. The idea is to try to keep the thing from amplifying a fixed scene for long periods. If there are no direct light sources or bright reflections in the area you are observing then you don't need to worry about this. But we have found in the majority of our surveillances that there are streetlights, exterior building lights, etc., in the area we were watching. It's free to show some mercy to the intensifier tube, and expensive to ignore it.
I must confess that I may overemphasize the importance of certain precautions. This is a conscious effort. By the time the warnings are watered down I want them still to be strong enough to be effective.
Brad Meyers (B.E. Meyers Company) developed and patented a circuit known as "Image Guard" for his Dark Invader line of night vision. This option consists of a photocell which reads the light levels reaching the intensifier tube. Excessive levels will power down the unit, protecting it to a large extent against damage. Like a safety on a firearm, though, don't count on it to provide absolute protection against ignorance.
The Image Guard works but it is still far better not to count on it to rescue the equipment from abuse or accident. As a matter of fact, I generally don't recommend Image Guard to our clients because a quick blast of light, from whatever source, will temporarily shut the piece down. A certain amount of idiotproofing is not a bad idea, but I really prefer not to have the equipment doing my thinking for me. The few Image Guard equipped pieces I've operated in the field annoyed me when they slammed shut. In a tactical situation I personally would prefer to consider the equipment expendable rather than risk the possibility of it shutting down at a critical moment (some of you with military backgrounds may remember the "Battle Short" switches on the electronics).
Once I was prone on a rooftop videotaping a tactical situation through a Dark Invader and had reflections from the chopper searchlight as well as beacons from the radio cars shut the piece down. As I recall, I stole a piece of electrical tape off a connector on the video system and covered up the photocell for the remainder of the operation. In all fairness, though, a feature such as the Image Guard would be great to have if your night vision piece is likely to be used by untrained or careless operators.
A very good option to order for your night vision, if available, is a daylight filter. This filter blocks, I would estimate, about 99% of the visible light. The filter threads onto the business end of the objective lens and allows the piece to be operated in full daylight with total safety. Obviously this accessory would be very desirable for daytime training on the night vision, and essential for sighting in a weapons-sight night vision during the day. Current price for this day filter is about $100, and as far as I know is available only for the Dark Invader line of night vision. We include one filter with every weapons-sight capable Dark Invader we sell.
Speaking of training - there's a lot more to using these pieces than knowing how to drop in the batteries and knowing which end to look into. I don't have the space this issue to do justice to the topic - maybe next time. I get bent, though, when I run into someone who handles a piece for the first time and considers himself an expert 5 minutes later. Many vendors who "sell" night vision literally never have seen one in the flesh.
Please be careful whose advice you accept, as there is a plethora of misinformation being offered by people who talk a good game. I've seen new equipment ruined because the salesman was incapable of explaining to the new owner how to operate it properly. It's more difficult to unlearn false information than it is to train a man properly the first time. Sound familiar to any of you weapons trainers?
Night vision operating at full gain will show some sparklies in the image. If there's enough light you won't see sparklies - and it's unusual not to have enough light if you're outdoors. It just doesn't get dark enough in most areas to be a problem what with ambient light from streetlights, skyglow, the moon, etc. Of course, if you're inside a warehouse or something at night then these pieces have to work for a living. Try to keep the manual gain below maximum if you can. Usually you can observe just as well with less than maximum gain, and your tube will last significantly longer that way.
If bright light does lunch your tube, all may not be lost. We've had a certain amount of success rescuing tubes that weren't too badly damaged. I'll be giving away a magician's secret, but try this before you send out for hemlock: Get about 5 sets of new batteries for your piece. With the lens cap on, or otherwise with the night vision device in absolute darkness, install fresh batteries, turn the piece on to maximum gain, and forget about it. By looking through the eyepiece (with the lens cap on) you should see sparklies if the batteries aren't dead yet. Let the batteries run down, put in a new set, and repeat the process maybe 5 times. Keep in mind that good alkaline, mercury or lithium batteries may power the piece 20, 30 or even 40 hours depending on temperature and some other factors.
Obviously, then, this effort at rejuvenation may take a week or more to complete. With luck, after this exercise you should notice significantly fewer blemishes on the image. We've had success maybe 25% of the time bringing a sick tube back to life using this technique. Some of the pieces we've rescued were written off by the manufacturers, who were amazed when the bad tube rose, like a phoenix, from the ashes. Please let me know the results if you try this, along with any suggestions you may have. If the advice in this paragraph saves you the multi thousand dollar purchase of a new tube please put a portion of the savings either into a lifetime subscription (our life, not yours) to Police & Security News, or send a donation for the office Christmas party care of us.
Remember MAD Magazine's money back guarantee? If you're not satisfied with your subscription to this magazine, return the unread portion of the magazine and we'll refund the unspent portion of your money...
If the particular lens you're using with your night vision has an adjustable F stop (iris), run it at the lowest setting (highest number). This will not only make it easier on the tube but will provide a greater depth of field. We're not discussing optical theory here, but remember that the smaller the F stop the greater the depth of field. This is true whether for video, film, night vision, and so forth.
Depth of field is described as the ranges from the lens at which a scene is in focus. With little depth of field it will be necessary to refocus every time you move from a closer scene to a further one, and vice versa. With great depth of field you may not have to focus at all. The basic idea is to try to keep the iris as small as possible. This makes a good argument for using fast film or a low light video camera even when there is plenty of light. You can demonstrate this easily with any auto iris video system. The more light there is the less critical the focusing. Same holds true for night vision. Small F stop openings are also safer for the intensifier tube if a lot of light should happen unexpectedly.
Cleaning the optics - this section will apply equally to night vision, video, film cameras, weapons optics, binoculars, eyeglasses, or anything else with quality lenses.
Many people don't take the proper care of their optics. Good lenses are expensive - sometimes comprising almost the total cost of a piece of equipment. Don't touch anything made of glass with your fingers. Handle filters by their edges only. Not only will your fingerprints degrade the performance of the lens, but the oil from your fingerprints is corrosive. If left uncleaned, an old fingerprint literally can etch itself into the surface of a lens permanently. Try not to grunge up anything to start with, but if it happens be sure to clean things up at the first opportunity.
Do NOT use your handkerchief or necktie to polish the optics. Special cloths are sold for this purpose, and are cheap. Using material with the wrong fibers will put thousands of small scratches on the glass, permanently reducing performance and creating a microscopically rough surface that will capture even more crap. The more finely polished a surface the better it will reflect or refract light, and you are causing problems when you scrub the things down with your shirttail. Use lint free cloths and cleaning fluid specifically designed for cleaning optics. They're cheap and readily available, so there's no excuse not to maintain an ample supply. Don't keep cleaning materials in your desk drawer. Keep them right in the case with the equipment so your guys have no excuse.
We have found a very good cleaning wipe for optics to be the OPTIC PAD from Texwipe. These are little packages about the size of a pack of matches you tear open, unfold, use once and discard. They come in boxes of a hundred and have a long shelf life. I have been very happy using them on our night vision devices and highly recommend them for any professional optics maintenance program. One distributor is UAS, available at 1-800-842-8200. Ask for the security products division. They will take orders over the phone from government agencies. It takes me about a dozen OPTIC PADS to thoroughly clean a night vision piece.
On a night vision piece, you need to keep the front and back surfaces of the intensifier tube clean as well as both ends of the eyepiece and objective lens. Try not to take either lens off any more than is necessary. When you do have an eyepiece or objective lens off, keep the naked end of the night vision pointed down, or preferably covered, so room dust or other garbage doesn't settle on the tube. If you see dust on the image when you're looking through the night vision, unscrew the eyepiece, objective lens, relay lens or whatever a half turn at a time. By watching which one moves the dust you'll know where you need to clean. If you're cleaning the tube surfaces, be especially careful. No fingers, and proper cleaning materials only. Your breath and a kleenex are not cool. Don't glop so much cleaning fluid on that it rolls around in there looking for somewhere to cause damage. The OPTIC PAD is really the best as it has a measured amount of fluid on it when you open it.
Anyway, the deadline doth approach, so I'm going to wrap it up for this time. All the shows are screwing everybody's schedules up and the entire industry seems to be a week late. Even the chickens are acting up. Running around partying and raising a ruckus, and you should see what they done to ol' Duke. Next year I'm planting corn...
Copyright (C) October 1988 by Steve Uhrig, SWS Security