How to Focus Helmet Mounted Night Vision
Focusing night vision may seem simple to some but there are many who are using their focus adjustments improperly or do not know proper focusing techniques. Focusing night vision is an essential task to preform to maximize the performance of your unit. Without properly focusing your device you can notice a severe degradation in image quality.
There are two focus adjustments on most helmet mounted night vision devices, the objective lens and the ocular lens. The objective lens is the lens furthest from the user’s eye and is used for distance focus. The ocular lens is the lens closest to the user’s eye and is used to focus the night vision device to the prescription of the user’s eyesight.
The first step to focusing your night vision is to focus the ocular lens. This is best done by turning the objective lens until the image appears as blurry as possible. This makes it easier to focus on the tube itself inside your unit. Next, while looking at the output screen on the actual tube inside your unit, focus the ocular adjustment until the tube is as clear as possible. To clarify the output screen is what you see if you look through your night vision when the unit is powered off. If you see any black spots in your tube you can use them to focus off of. If not, you may see a honeycomb pattern, and this can also be used to focus off of. It is very important to understand that during ocular focus you are not looking through your unit but rather at the output screen on the tube itself inside your unit. This is the same concept as adjusting an ocular adjustment on a day scope. You focus off of the reticle and not downrange.
One important note, when focusing the ocular adjustment take in account the amount ambient light present. When focusing the ocular lens, it is helpful to look at a plain background with enough ambient light that the tube is not struggling to gather light. This will make it easier to see the imperfections in the tube when focusing on the output screen.
Once your ocular adjustment is set correctly, your unit is set to the user’s eyesight. If you have binos you need to do each pod separately. It is helpful to close the opposite eye when focusing binos. Unless your ocular lens moves by accident or your prescription changes then the ocular adjustment does not have to be adjusted each time your unit is used.
The second and final focus adjustment is the objective lens. The objective lens controls distance focus and will be adjusted regularly depending on how you are using your unit. For outside use, the widest range of focus is infinity focus. Infinity focus is a great way to set your objective lens/lenses. This can be done by focusing on the stars or a far-off tree line. With infinity focus most of your image will be in focus with the exception of a couple feet in front of you.