To be or not to be in Color: A 10 year study of the benefits and pitfalls of including color information in AOI systems

摘要

Imagine that you were choosing a camera for your AOI system. Should you opt for a black and white camera or a color camera? This seems like a no-brainer. Most of us would go for a color camera. As humans, we take for granted that our world is in color. Most people see a brilliant color world effortlessly and without much thought to how the brain creates these color images. Cheap consumer color megapixel cameras are popping up everywhere from digital cameras, cell phones, and web cams. In the consumer space, color adds significant benefits to our everyday life from online interactions to saving our memories.However, there are in fact hidden complexities in the choice of using color in the industrial space. Color cameras are typically slower than their monochrome counterparts. Color adds three times the information, which can slow down back-end processing. The quality of the image is highly dependent on the spectral characteristics of the illumination source. Furthermore, most AOI systems need to be able to resolve and measure small features accurately and reliably, and this resolution requirement can be at odds with how color cameras measure color attributes from the world. Even with the inclusion of a color camera in an AOI system, one must address how color can and should be used in AOI machines so that the system can identify defects and measure process attributes. Because of these and other considerations, it is not entirely obvious as to which camera system is best for a given AOI scenario.There are significant benefits and pitfalls to using color in automated inspection of printed circuit board and the use of color must be thought through carefully. Over the last 10 years we have studied the science, the technology, and the application of color in AOI. In this paper we bring to light important issues about color that are surprisingly little known except to a select community of color scientists. We also show how these issues aid and detract from AOI inspection. Finally we discuss how even with the adoption of color hardware, software can make or break its overall benefits to AOI inspection.