Printed Circuit Board Inspection
| Application Type | Inspection |
| Image Characteristics | Monochrome |
| Machine Vision Tool(s) | Pattern Matching |
The printed circuit device inspection example uses the Pattern Matching function to determine if PCB components are present and in the correct location, and matches areas of inspection to a template of valid components. This application uses shift-invariant matching to inspect an oriented component (diode) and uses rotation-invariant matching to inspect a component (resistor) that may appear in multiple orientations.
Pattern Matching—Locates a specific diode component in the image of the PCB. The template used to locate the component is chosen so that it contains only the relevant parts of the component necessary for the location process. This avoids mismatches or positioning accuracy problems that may arise due to variations in the background of the component.
Because the orientation of the diode is important to the inspection process, shift-invariant pattern matching is used to locate the diode. The Pattern Matching function does not find the diode if it is present but incorrectly oriented, causing the inspection to fail.
Because you know the expected location of the diode before you begin the inspection process, you can specify a search region around the location of the diode, which speeds up the pattern matching process.
Pattern Matching—Locates a specific resistor component in the image of the PCB. The template used to locate the component is chosen such that it contains one of the relevant parts of the component needed to locate it. This avoids mismatches or positioning accuracy problems that may arise due to variations in the background of the component.
Because the orientation of the resistor is not important in the inspection process, rotation-invariant pattern matching is used to locate the resistor. The Pattern Matching function finds the resistor if it is present in the image at any orientation. Inspection fails only when the resistor is not present in the image.
Because you know the expected location of the resistor before you begin the inspection process, you can specify a search region around the location, which speeds up the pattern matching process.