Stop integrated infrared light from reflecting back into the dome

Source facts: the camera can illuminate its own obstruction

Axis Communications’ white paper, IR reflections in dome cameras, explains that integrated infrared illumination can reflect back into the lens and produce foggy, blurry, mirrored, or severely degraded nighttime video. The common causes are nearby surfaces, material on the dome, outside light directed toward the camera, and infrared light leaking past the seal around the lens.

Walls, ceilings, eaves, poles, windows, and other close objects may sit outside the visible image yet still enter the wider cone of infrared light. Light or glossy surfaces generally reflect more than dark or matte ones. This is why a daytime view that appears clear of obstruction does not prove that the nighttime illumination path is clear.

Dirt, dust, spider webs, water droplets, snow, and ice can return the camera’s own IR light directly toward the lens. External IR from another camera and visible light from a nearby fixture can create similar effects. Tilting an internal lens too far may also separate or deform the rubber light barrier that is intended to keep the LEDs optically isolated from the lens.

Source facts: common corrections have tradeoffs

Axis recommends keeping the IR beam away from reflective objects, reducing weather exposure, cleaning the dome correctly, redirecting outside light, minimizing internal lens tilt, and preserving the lens seal. Adjustable IR intensity and a beam that follows the field of view can reduce stray illumination. A semi-smoked dome may reduce visible reflections, but it also reduces light sensitivity and should not be treated as a free correction.

A clean daytime image, an open-camera bench test, or a live view before the LEDs activate cannot validate these conditions. The dome, gasket, desiccant where applicable, lens position, illuminator, and final mounting environment must all be in their production state.

DSE recommendation: perform a complete nighttime acceptance test

Inspect the beam path. Check the space beside and above the visible frame for walls, conduit, brackets, soffits, signs, foliage, glass, and reflective trim that the wider IR beam may reach.

Inspect the optical surfaces. Remove protective film, fingerprints, packing residue, dust, and installation debris. Use only manufacturer-approved cleaning materials and replace scratched or damaged domes.

Verify assembly. Confirm the lens seal is present, undamaged, correctly seated against the dome, and not displaced by excessive tilt. Follow the model’s installation limits rather than forcing the view.

Test in real darkness. Allow the camera to enter its production night mode. Record a person moving through near, middle, and far test points with all nearby lighting and cameras operating normally.

Add realistic contamination. When safe and appropriate, repeat after rain or irrigation and inspect under common seasonal conditions. A dry commissioning night cannot prove resistance to droplets, snow, insects, or condensation.

Tune only after correcting geometry. Move or redirect the camera, light, or reflective object before simply reducing IR output. Lower intensity may hide the reflection while under-lighting the required target.

DSE recommendation: diagnose the pattern, not just the symptom

A bright arc or patch near one edge often points to a nearby reflective surface. A general haze may indicate a dirty, wet, or scratched dome. A reflection that changes when another camera enters night mode may come from the neighboring illuminator. Leakage near the lens position can indicate a seal or tilt problem. Preserve before-and-after clips and record the corrective action.

If a smoked dome, separate illuminator, different mount, or different camera form factor is proposed, retest pixel density, exposure, motion, and target visibility. A cosmetic improvement is not sufficient if it shortens usable range.

DSE recommendation: make darkness part of maintenance

Add a nighttime image review to preventive maintenance. Check dome cleanliness, scratches, seal contact, water paths, insect activity, nearby vegetation, new signs or fixtures, IR intensity, and representative recorded playback. Compare the view with the accepted reference clip.

The useful handoff is not “IR enabled.” It is evidence that the assembled camera can illuminate and record its required scene after dark without reflecting its own light back into the lens.

Official references

Axis Communications, IR reflections in dome cameras, May 2021.