Night Vision for Commercial Vehicles: How to Read Lux and IR Specifications

Starting with lux

Lux measures illuminance — how much light falls on a surface. Camera datasheets quote two figures: the minimum illumination for colour operation, and the minimum for black-and-white operation with infrared.

A camera rated at 0.1 lux produces a usable colour image down to roughly a well-lit street at night. Below that it switches to infrared, producing a black-and-white image illuminated by the camera’s own LEDs. "0 Lux with IR" means the camera can see with no ambient light at all, because it is supplying the light itself — which is a much narrower claim than it first appears.

What "0 Lux with IR" leaves out

• How many LEDs. Four LEDs reach a few metres; eighteen or twenty-four reach considerably further and cover a wider area. The count is a fair proxy for both reach and evenness of illumination.
• The wavelength. 650 nm produces a faint visible red glow at the camera. 850 nm is nearly invisible to the human eye and therefore less conspicuous, but slightly less efficient. Our 650 nm arrays are visible; if covert operation matters, check the wavelength before ordering.
• IR range in metres. Some datasheets state a distance — our AI camera, for example, reaches ≤ 15 m with four high-power IR LEDs. This is the number that determines whether IR is useful on a 12-metre trailer or only for close manoeuvring.
• Evenness of coverage. A ring of LEDs produces a bright centre and a dark surround. A dot-matrix board produces a more uniform field, which matters more than peak brightness for actually recognising what is in the image.

Backscatter: the most common night image problem

Infrared illumination reflects off particles close to the lens — dust, spray, fog, or a dirty lens cover — and returns to the sensor before it reaches the subject. The result is a milky white veil over the image, sometimes with visible bright specks. Drivers describe it as a foggy picture on clear nights.

Three things cause it, and all three are design or maintenance issues:

1. The LEDs sharing an optical chamber with the lens. Light reflects directly off the front glass back into the lens. A dual-chamber housing, such as our JPC-171, physically isolates the LED board from the lens and eliminates this path.
2. A dirty or scratched lens cover. Even a thin film of grime scatters IR back into the camera. Cleaning the cover is the cheapest fix available and it resolves the majority of complaints.
3. A spray or dust cloud in front of the camera. No housing design fixes this; the answer is mounting the camera where it is outside the spray pattern, or accepting that in heavy rain the image will be limited.

IR is not the only option

For long-range night vision, infrared LED illumination is fundamentally limited: the light falls off with distance and it is scattered by anything in the air. Beyond roughly fifteen to twenty metres, LED systems stop being useful.

• Thermal imaging detects emitted heat rather than reflected light, so it has no range limitation of the same kind. Our thermal range detects a person at under 85 m with the wide lens and under 250 m with the 10 mm lens, with no illumination at all.
• High-power LED work lights, as integrated into the JPC-146 agricultural camera, extend visible-light range where the vehicle electrical system can support them.
• OSRAM long-range illumination on specialist units — the PTZ inspection camera reaches beyond 100 m with the right configuration.

Specifying night vision sensibly

1. Decide the required distance first. Close manoeuvring needs a few metres; highway or yard detection needs tens of metres. That single decision selects the technology.
2. For under 15 metres, an IR camera with a good LED count and a dual-chamber housing is the cost-effective answer.
3. Beyond 20 metres, specify thermal. IR will not deliver, whatever the LED count says.
4. Check the housing. Dual chamber, dot-matrix LEDs and a metal lens barrel are the three features that separate a good night image from a poor one.
5. Plan for cleaning. Every camera loses night performance when its lens cover is dirty. Include the lens cover in the vehicle walk-around check.