Automated optical inspection (AOI) is a system that is able to visually inspect products to see if they are perfect or faulty. AOI systems are used on a variety of products, such as car parts, food and labels. The most intensive automated optical inspection system is used in the printed circuit board (PCB) industry, because of the variety of small problems that can compromise a PCB’s effectiveness. An AOI program uses a combination of light and either a scanner or camera to capture information about the product, and then compares it either to a master or to digital data. While this is much faster than manually inspecting a product, industries that create products with much variation may not find AOI very useful, because this system can only handle similar products.
In the past, when a product was made, employees were hired to look at the product. They would manually search for defects and ensure all the parts were placed correctly on the product. While effective at the time, manual inspection is much slower and less accurate than automated optical inspection. This is because the AOI system, unlike human inspectors, will not get eyestrain or accidentally forget where a part is supposed to go.
Automated optical inspection is available for many different products, and each product receives its own set of inspection instructions. For example, if inspecting fruit, an AOI system will check for color variation or bumps; for car parts, an AOI system will check to ensure the part is the right size, is modeled correctly and has no manufacturing flaws. The most advanced type of AOI is used with PCBs, because of their complexity. AOI systems must check for proper soldering, that all the parts are present, and that no defects are present.
To check a product, automated optical inspections make use of light and a camera or scanner. Light is needed to reduce visual noise and to make sure the camera or scanner can see the product without interference. A camera is less efficient in this arena, because more than one may be needed for proper inspection. Scanners digitize the visual information and can easily compare it to templates or data.
Ensuring the product is perfect means the automated optical inspection system must know what a perfect product is. One way of doing this is to use a master template, which involves continuously scanning a perfect product template and comparing it to the inspected product. The second way is by putting computer-aided design (CAD) data into the system, so it can check the product against the perfect data.