The illuminator is positioned behind the target-object, aimed directly back towards the sensor, and the resulting silhouette can be inspected for dimension and shape control. The brightness is low.

• Advantages: does not supply surface characteristics. Facilitates the diameter measurement of round objects. Shows presence or absence of holes.
   
• Disadvantages: illuminator positioning behind object may result difficult. Does not analyse object surfaces. The illumination area must be larger than then inspection area.

Typical applications include object sorting according to shape and dimensions, measurement of spacing between chip leads, inspection of object holes or cracks.