Table 8 Characteristics of different lighting methods and applicable occasions.

Coaxial illumination

Reduces shadows and reflections on the surface of the object to be detected

Complex design and higher costs

Scratches and cracks on metal surfaces and internal defects on transparent or translucent objects such as glass and plastics.

Backside illumination

Highlight the outline features of the object so that it contrasts with the background

Light source blocking, limited range of application

Character recognition, object contour extraction, etc.

Ring illumination

Uniform illumination with no visible projections or shadows

Obstructed field of view, uneven illumination on large flat or curved objects

Printed matter, circuit boards, and other objects requiring detection of surface details and minute features

Parallel illumination

Provides high brightness lighting effects

Limited scope of application and higher costs

Dimensional measurement, positional positioning, and other applications requiring high precision and clarity