Background Theory > PCB Design > Automated Pick and Place > How does Pick and Place Machine Vision Work

The machine vision system of a pick and place machine plays a crucial role in ensuring accurate placement of components onto a PCB. Here's an overview of how it works:

Image Capture

The vision system starts with an image capture device, usually a high-resolution camera. The camera captures images of the component after it's been picked up by the machine's head. In some sophisticated systems, there might be multiple cameras to capture different angles or both sides of the component and the PCB.

Lighting

Adequate lighting is essential for capturing a good image. Different types and orientations of lighting can help to highlight certain features or contrasts in the component. The lighting system can include direct lighting, back lighting, or diffused lighting, depending on the specific requirements.

Image Processing

Once the image is captured, it's processed using a range of techniques. The goal is to extract key information from the image, such as the component's position, orientation, and condition. Digital image processing techniques such as edge detection, blob analysis, and pattern matching are often used. The system can also compare the captured image with a stored image to verify that the correct component has been picked.

Fiducial Recognition

Fiducials are markers that are added to the PCB and used as reference points. By identifying these fiducials, the vision system can correct for any slight misalignment of the PCB and ensure that the components are placed in the correct position. The fiducials are usually small solid circles, crosses or squares that can be easily identified by the vision system.

Feedback

The results of the image processing can then be used to adjust the placement of the component. For example, if the vision system determines that the component is slightly rotated, it can instruct the machine to adjust the rotation before placing the component. The feedback loop is fast enough to correct any errors in real-time.

Quality Control

In addition to assisting with component placement, the vision system can also be used for quality control. For example, it can check that the components have been placed correctly and are properly aligned. Any discrepancies can be logged for further inspection.

Overall, the machine vision system is an integral part of modern pick and place machines, providing accuracy, speed, and quality control. It allows the machine to quickly adapt to the different types of components and PCB designs.