The optical aids technique involves illumination of the objects surface with light. The reflected light is then examined using visual aids, usually at magnification. Visual examination can reveal gross surface defects, cleanliness, foreign objects, surface condition, mismatches and any other discrepancies. Visual techniques are easy to apply and are considered to be the most effective and the least expensive NDE techniques.

Composite Materials
Fatigue cracks.

Rod Rigging
Fatigue cracks on coldheads

Other
Weld cracks & heat treatment cracks.

Optical aids can only be used on surface-breaking defects and areas in plain view.