Ring lights for industrial machine vision

1. Lens opening: will the lens fit through?

Ring lights are incident-light lights: they sit around the lens and illuminate the part from the camera side. The inner opening is the first knock-out criterion. It has to take the lens, the filter mount and the lens hood without clipping the optical path; a ring that is too small cannot be made up for with more power. Across the catalogue it ranges from 6 mm to 330 mm.

Almost every light carries the opening as a manufacturer figure. Where it appears in no document, we leave the field empty and show the light under „not stated by the manufacturer" rather than borrowing a number from a neighbouring model. If your lens is a tight fit, ask us for the opening of the specific model and we will clarify it with the manufacturer.

2. Outer diameter: will the light fit the space?

The outer diameter drives the mount, the clearance to neighbouring assemblies and access to the station. The catalogue ranges from 20 mm to 430 mm; the figure is documented for nearly every light. A larger ring does not light better by itself: it moves the LEDs further out and changes the angle at which the light meets the part.

3. Light color and wavelength

The light color is documented throughout: white, blue, red, green, UV and infrared. For some models the manufacturer also states the peak wavelength, from 365 nm to 940 nm; white lights carry a color temperature instead.

Color is not chosen on its own but against material and camera: what matters is whether the feature separates from the background at that wavelength. With infrared and UV, sensor sensitivity, lens suitability, filters and the safety notes of the model come on top.

4. Angle of incidence: the direction, not the lighting technique

„Angle of incidence" says where the light comes from: direct front light steeply from above, angled front light more from the side. It is described for only some of the lights; for most, the manufacturer says nothing. Because so many lights would have been left blank, the angle of incidence is no longer a filter as of 17 September 2026; it sits in the technical data, and filtering runs over the beam angle.

It does not mean the lighting technique, bright field or dark field. Whether an edge is imaged bright or dark depends on the interplay of incidence angle, surface and camera position, not on the form factor alone. A shallow-angle ring can look dark-field-like, but it is not a dark-field light.

5. Operating mode and controller

Where the operating mode is documented, the manufacturer releases the light for continuous operation, for strobe operation or for both. A light the manufacturer releases for strobe only must not be powered continuously; that is not a detail, that is its service life.

Many models name a recommended controller. No manufacturer in this category states for any model that none is needed; where nothing is stated, the question is open, not answered. Light, controller and connection therefore belong in one inquiry.

6. Beam distribution and angle

Most lights carry a beam angle between 0° and 120°, and some a statement on beam distribution (diffuse or highly diffuse). Both are manufacturer figures: manufacturers measure the angle differently: half angle, full angle or the tilt of the LED row. Two numbers from two catalogues are therefore not directly comparable, and we do not convert them.

For a shortlist, a photo of the installation space, good and bad parts and the camera and lens data help. Where a figure is missing, be it working distance, IP rating or controller, we clarify it before you order instead of borrowing it from a neighbouring model.