Shadow-free illumination is a special form of reflected lighting in which diffuse light falls on the test object from all directions. This allows the creation of completely shadow-free illumination. To achieve this effect, the object is not illuminated directly by the light source. The light shines into a dome-shaped reflector and is directed onto the test object from all directions. The dome-shaped reflector also gives the lighting its name, dome lighting.
This lighting scenario is best compared to a cloudy day. On a cloudy, bright day, it temporarily appears as if the light is coming from all directions. The position of the sun cannot be made out. The clouds act as a diffuser and reflector and create uniform illumination from all directions. This prevents the usual shadows from being cast. For this reason, this type of lighting is often referred to as cloudy day lighting.
Dome lighting is particularly suitable for:
- Surface inspection, even of curved objects
- Inspection of diffuse, but also highly reflective and specular surfaces
- Detection of placement, type and position
- imprint inspection
- code reading
- OCR/ OCV
Shadow-free lighting is especially suitable for the high-quality imaging of glossy surfaces with a complex structure. One example use is creating homogeneous lighting for highly reflective packaging with buckling and irregularities, so as to enable print quality inspection.
The limitation when using this type of lighting ist the working distance. To ensure shadow-free illumination, this distance must be kept as short as possible. Convex and globe-shaped objects may even need to be fully enclosed by the lighting setup.