Fundamental testing of a vision systems code-reading tools
John Stamos, 12-26-2012
To evaluate industrial code reading tools, start by measuring the vision system’s reading speed. To do this, present a well-marked code to the vision system and have it read the code hundreds of times under pristine conditions to determine the number of reads per minute. Make sure the read rate under these optimized conditions is 100%, or you may face problems later when conditions might be less than ideal. For example, at a production line speed of 2,000 parts per hour, a read rate of 99.7% would fail to read the ID codes on 48 parts in just one eight-hour shift!
After establishing the system’s reading speed, you should run a more challenging read rate test to determine the impact of factors such as line vibration, variable lighting conditions, and extremely high line speeds on the vision system’s reading performance in your application. To do this, present a large sample of codes of good, bad, and marginal quality to the vision system. At the same time, simulate vibration and motion blur by shaking the part and sliding it back and forth beneath the camera as it acquires an image. This test will provide a good initial assessment of how well the vision system’s read rate will hold up under real-world production conditions.