Small holes are important features that can be used very conveniently to locate complex objects. If holes are very small, 3 × 3 or slightly larger window operators can be used to locate them. If large and circular, the Hough transform may be suitable. If of intermediate size, special fast-acting methods may be useful. This chapter analyzes the situation and compares the available methods and their properties.
Look out for:
• the basic template matching method for hole detection.
• the lateral histogram method for hole detection.
• how ambiguities can be eliminated with the lateral histogram method.
• how speed of processing can be estimated.
• limitations of the lateral histogram method.
• how illumination sets a limit on detection ...