Black Boxing Night Vision: Why & How To Do It
Black boxing is the process of evaluating a night vision image intensifier tube in a completely dark, light-sealed environment with no ambient light whatsoever. This technique reveals characteristics of the tube that are impossible to see under normal operating conditions and provides valuable information about tube quality, health, and cosmetic condition.
Why Black Box Your Night Vision?
Under normal use, the ambient light being intensified by the tube dominates the image, masking the tube's inherent background noise and cosmetic imperfections. When you remove all external light, you strip away the signal and can observe only the tube's internal characteristics: the equivalent background illumination (EBI), scintillation patterns, bright spots, dark spots, and other blemishes.
Black boxing is particularly useful in these situations:
- Receiving a new device: When you first receive a night vision device, black boxing it allows you to inspect the tube for blemishes and defects and compare what you see against the tube data sheet. This is your baseline for future reference.
- Evaluating a used device: If purchasing a used night vision device, black boxing can reveal tube wear and degradation that might not be obvious during normal use.
- Comparing tubes: If you have access to multiple devices, black boxing them side by side lets you compare their noise levels, EBI, and cosmetic quality on a level playing field.
- Monitoring tube health: Periodically black boxing your device over its life allows you to track any changes in performance that could indicate degradation.
How to Black Box Your Night Vision
Step 1: Create a Light-Sealed Environment
Find or create a space with absolutely zero light. A windowless interior closet or bathroom is often sufficient. Turn off all lights and electronic devices with indicator LEDs. Use towels or tape to seal any light leaks around doors. The goal is total darkness. Even a tiny pinpoint of light can contaminate your observations.
Step 2: Allow Your Eyes to Adapt
Sit in the dark room for at least five minutes before turning on the night vision device. This allows your eyes to dark-adapt so you can better perceive the faint details in the tube's background.
Step 3: Cap the Objective Lens and Power On
With the objective lens cap firmly in place (to ensure no light enters the tube), power on the device. What you see through the eyepiece is now purely the tube's internal output with no external light signal.
Step 4: Observe and Document
Look through the eyepiece and observe the following:
- EBI glow: You should see a very faint, uniform glow across the image area. This is the equivalent background illumination. A lower (dimmer) EBI indicates a better tube.
- Scintillation: The sparkling or grain visible in the image. Lower scintillation indicates higher signal-to-noise ratio.
- Bright spots: Fixed bright points in the image that do not move. These are cosmetic imperfections in the MCP or phosphor screen.
- Dark spots: Fixed dark points or areas. These are non-functional or blocked channels in the MCP.
- Edge glow: Some tubes exhibit brighter areas around the edges. Minor edge glow is normal; excessive glow can be distracting.
Step 5: Compare to Spec Sheet
Reference the tube's data sheet. The blemish count and locations should roughly correspond to what you observe. If you see significantly more defects than listed, contact your vendor.
What Is Normal?
No image intensifier tube is cosmetically perfect. Minor bright and dark spots, particularly in the outer zones (Zone 2 and Zone 3) of the image, are common and within military specification. A few small spots in the peripheral areas of the tube will not affect practical performance. What you want to avoid is large clusters of blemishes in the center of the image (Zone 1) or any defect that creates a noticeable blind spot during normal use.
Questions about your tube's black box results? Contact us at [email protected].