AOI (Automated Optical Inspection) is an acronym for Automated Optical Inspection, a quality control technique commonly used in the electronics manufacturing process.The mode of operation of AOI usually consists of the following steps:

1. Image Acquisition: The AOI system uses a high resolution camera or optical sensor to acquire images of the circuit board to be inspected. These images can be top, bottom or side views of the board, as well as magnified views of specific areas.

2. Image processing: The acquired images are processed by image processing algorithms to extract key features and target areas on the board. Image processing algorithms can include techniques such as edge detection, colour analysis, shape matching, etc. for detecting components, pads, printed marks, etc. on the board.

3. Defect Detection: The AOI system will detect defects in components and pads in the image according to pre-set rules and standards. Common defects include missing components, offsets, wrong polarity, shorted pads, open circuits and so on. The detection algorithm can make judgement based on the characteristics and location of the components.

4. Result Determination: The AOI system will make a determination based on the inspection results, and classify the board into qualified and non-qualified products. Qualified products can continue to enter the next step of the production process, while non-conforming products need to be repaired or remanufactured.

5. Data analysis and recording: AOI system will analyse and record data on the inspection results, including defect type, location, quantity and other information. This data can be used for quality traceability, statistical analysis and production optimisation.

It should be noted that different AOI systems may have different operation modes and functions, and the specific operation process may vary. However, in general, the operation mode of AOI mainly includes image acquisition, image processing, defect detection, result determination and data analysis.