Diffuse On-Axis Lighting (DOAL) provides the ultimate lighting solution for inspection of highly-reflective shiny objects, particularly when the reflective surface has bright specular highlights caused by structures that have a concave shape pointing toward the camera.

Highly Diffuse Light generated from an internal powerful LED array is reflected downward toward the object through a 50% transmissive beam splitter mirror. The camera is positioned above the mirror, peering directly downward toward the subject, orthogonal to the surface. Since the camera and the illumination are along the same Z axis, shadows that can plague off-axis illumination are eliminated. 

The images below show a comparison between a RING LIGHT illumination and DIFFUSE ON-AXIS LIGHT illumination, for resolving barcodes stamped into a metallic sample well. Note the bright saturated regions and shadowing in the ring light image on the left. The shadows and specular highlights are eliminated in the image on the right, rendering the 2D barcode pattern clearly readable.