1. The light source of AOI machine consists of red, green, and blue LEDs, which use the three-color principle of color to combine different colors and combine the mirror reflection, diffuse reflection, and oblique reflection in the optical principle to display the PCB chip components and soldering conditions in the form of images.
2. weights imaging data difference analysis system is through an image rasterization, analysis of each pixel color distribution of the location coordinates, imaging raster between (color) excessive relationship and other imaging details, listed a number of function formula, and then through the same area size of a number of similar pictures for data extraction, and analysis and calculation, the calculation results according to the software set by the weight relationship and the initial image pixel color, coordinates This image is called the "weight image", and its main digital information contains the graphic outline of the image, the distribution of colors, the weight relationship that allows changes, etc., for later analysis and processing.
3. Similarity principle. The light-dark relationship of the image is used to form the shape contour of the target object, and the degree of resemblance between the shape contour and the standard contour is compared. The method is more effective in detecting missing components and omission of paste.
4. color extraction. Any color can be used red, green, blue three primary colors in accordance with a certain ratio of the mixture. Red, green and blue form a three-dimensional color cube. Color extraction is in this color cube to crop a small color cube, which corresponds to the range of colors we need to select, and then calculate the detected image to meet the proportion of the color cube to the number of colors in the whole image, check whether to meet the required set range. In the case of red, green and blue light, the method is most suitable for the detection of resistors, capacitors and other solder.
5. Image comparison. In the testing process, the device through the CCD camera system to capture the image on the circuit board under test, after the image digitization process into the computer internal, and the standard image for computing comparison (comparison items include the size of components, angle, offset, brightness, color and location, etc.), and the comparison results exceed the rated error threshold of the image through the monitor output, and display its specific location on the PCB .
6. Binarization principle. The target image is converted to grayscale image in a certain way, and then a certain brightness threshold is selected for image processing, and those below the threshold are directly converted to black, and those above the threshold are directly converted to white. Make the characters, IC short circuit, etc. directly separated from the original image.
Through the above methods, the automatic optical detector can complete the detection of defects such as lost components, component polarity, placement accuracy, solder paste printing or solder joint quality, component labeling, etc.
