Machine vision systems rely on high-quality images to provide accurate, reliable and repeatable part inspection. The best way to obtain these images is to optimize the lighting of the part being inspected.

Optimal lighting maximizes feature contrast so the camera can easily locate a specific shape, mark or surface feature. Poor lighting produces uneven illumination of the part, increasing processing time.

Many factors must be considered to achieve optimal lighting. These include the color, angle, type and amount of light needed; part size, surface features and geometry; if the part is moving or stationary; and the size of inspection area to be lighted. The vision system’s capabilities and the manufacturer’s specific production requirements also must be considered.

Our Nerlite lighting series can be used in a wide range of part-inspection applications. The following tips offer manufacturers eight ways to use this lighting to optimize vision system performance. 

A vision system can detect missing material in a part. The system also can detect when an insufficient quantity of material has been injected into a mold. This condition, known as a short shot, produces parts with unsealed surfaces.

Application: Detecting Short-Shot Plastic Bottles.

A plastic-bottle manufacturer had trouble detecting short shots, which were causing customer complaints. To better detect short shots, the manufacturer now uses a Nerlite DOAL (diffuse on-axis light) illuminator.

On a good bottle, the DOAL reflects brightly off the flat sealing surface and presents the camera with a well-defined bright annular area. In contrast, the short-shot bottle’s flat specular surface scatters light away from the camera, creating dark areas.