The dark-field ring lights are available in different inner- and outer-diameters. The inner-diameters vary from 40 to 136mm and the outer-diameters vary from 74mm to 174mm.
The LLA series is very compact, only 20mm high and works best with working distances ranging form 5 to 10mm. EVT can also provide diffusion filters and polarization filters.
The rays of the dark-field illumination are refracted from the object. Therefore not all light rays reach the camera lens directly.
EVT Eye Vision Technology - www.evt-web.com