Common causes and improvement methods of poor night vision
From the four aspects of infrared, lens, installation, and environment, we explain the specific solutions to the problem of white, dark, and unclear images at night.
Problem classification and processing
| Phenomena | Cause | Treatment |
|---|---|---|
| The whole picture is white and overexposed | Strong reflection at close range or too strong infrared | Turn on smart infrared / reduce infrared intensity / adjust the angle |
| The surroundings are dark (vignetting) | The angle between the lens and the infrared light does not match | Replace with a matching model (telephoto with narrow-angle light) |
| It’s all white and nothing can be seen | Infrared is reflected by the glass | Move the glass / stick to the glass / turn off infrared |
| There are web-like bright spots | Spider webs and dust reflect at close range | Clean the lens and shield |
| The more it is used, the darker it becomes | The infrared light attenuates | Replace the equipment or install an external fill light |
| The night vision distance is not enough | The nominal distance is falsely high/the lens focal length does not match | Estimate based on nominal 60%, or use laser/external fill light instead |
Lens and installation factors
- The focal length is too short: The distant target is too small in the frame and looks "clear". This is not a night vision problem.
- The angle of depression is too large: The angle between the direction of infrared illumination and the direction of the lens is large, and the reflected light is insufficient.
- Blocking: Branches, billboards, and awnings block the path of infrared radiation.
- Opposite interference: Two cameras emit infrared light opposite each other, causing each other to be overexposed.
Ambient fill light
- Need Night color picture: use warm light/white light to fill the light (starlight level + low light fill light is better).
- Only black and white night vision is required: infrared is the most economical. If you pay attention to concealment requirements, choose 940nm without red burst.
- Large-area scenes: Consider adding street lights or ambient lighting, which is more effective than simply increasing infrared.
- Do not install the fill light directly above the lens to avoid attracting insects and causing reflections.
Parameter adjustment
- At night, the shutter speed can be appropriately lowered (such as 1/25s) to increase the brightness, but moving images will smear, so this needs to be weighed.
- The noise reduction level can be increased at night, but too high will cause smearing.
- It is recommended to turn off wide dynamic range in pure infrared scenes at night to avoid introducing additional noise.
- The infrared switching threshold should be reasonable to avoid repeated switching at critical illumination.
Acceptance Suggestions
Night-time acceptance should be carried out in complete darkness and check:
- Whether the brightness of the target area is uniform, without obvious dark corners and overexposure.
- Whether key targets (faces, license plates, passages) are identifiable.
- Observe continuously for more than 30 minutes to confirm that there is no frequent switching or flickering.
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