Second, image analysis converts an image into measurements, such as the package's size and location. For example, image analysis is used to characterize the size and shape of particles trapped on a PWB to determine whether a high-quality solder joint can be produced. In machine vision, measurements such as color, size and distance between edges are used to evaluate various package parts and reject those with defects. The primary components involved include cameras, lighting, one or more vision controllers or frame grabbers and machine vision software running on a computer. The goal is to find the combination of techniques that results in the best possible image.
Front lighting illuminates the area in front of a part.
The result is a pattern that is created by the part intersecting the light. Backlighting places the light source behind the object of interest so that a silhouette is created. Structured lighting uses sheets of light to determine the shape or dimensions of a part by observing the pattern made when the part intersects the structured light. Finally, strobe lighting allows high-speed processes to be monitored by providing a short burst of light, typically in the microsecond range. Within these four categories are a dozen or more specific types of lighting techniques.