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Backlight illumination - diffuse

Technique positioning a diffuse illuminator behind the object to produce a silhouette.

A technique positioning a diffuse illuminator behind the object to give a silhouette. This technique is normally used if 'through holes' or shapes are of interest, or the object is generally opaque with darker/brighter variations in the areas of interest.

The images show how the fill level of a bottle is being checked. The first image was taken under normal domestic lighting while the second image was captured using a high intensity backlight to create a clear image of the liquid surface which shows up as a dark line in the camera image that is then very easily detected by the software.

It is not easy to check the fill level of a brown bottle under normal domestic lighting.

Bottle captured using a high intensity backlight to create a clear image of the liquid surface.

Another common use for backlights is part presence verification. In the images the component has been transformed into a binary image that is much easier to examine for simple defects such as bent or missing connectors or for major damage.

Example 2 without backlight illumination diffuse

Example 2 with backlight illumination diffuse