Using Structured Illumination

This is Section 11.3 of the Imaging Resource Guide

Illumination is a critical component of any machine vision system, and can often be the difference between a good imaging system and a great one. Not only does the illumination position and wavelength need to be uniquely considered for each application, but certain systems require structured illumination to maximize system performance.

Structured illumination utilizes specific patterns of light to determine the geometric shape and depth of objects. An effective 3D system can be constructed by illuminating objects with different patterns, such as grids, dots, or lines, while minimizing cost, components, and complexity.

Since a well-calibrated system increases measurement accuracy, it is important to understand that structured illumination is not universal, and certain structures should be used to obtain certain measurements. For example, a dot grid pattern may suffice to inspect a few points on an object, but a line or multiple line pattern is required to measure an object’s three dimensional profile.

The table below demonstrates common structured illumination patterns and their ideal applications.

Common Structured Illumination Patterns
Structured Illumination	Method of Determination	Purpose
	Triangulation Based	Determining the dimensions of most objects while the object is scanned
	Shadow and Triangulation Based	Determining the dimensions of refractive objects while the object is scanned
	Distortion Based	Determining the depth information at multiple discrete points in a single exposure