Setting up task-optimal illumination automatically for inspection purposes

Illumination with correct intensity and direction can help solving even very complicated inspection and measurement problems by hiding unnecessary information and by enhancing the contrast where it is needed. The 'wave and look' approach used widely in the vision industry requires knowledge about different illumination techniques and the measurement problem. One illumination is not optimal for all tasks performed using one vision system and so even more complex illumination combinations can be expected, particularly on small-batch production lines. We describe approaches for producing flexible light sources for machine vision purposes. Our devices allow one to change the scene illumination by software. Often only one programmable light source is needed per one vision system despite very different illumination needs. We also describe an automated tuning approach that controls programmable light sources on-line to correct the image seen by the sensor to maximize the illumination uniformness, contrasts, or even the part measurement robustness. The paper also shows the results of test cases and discusses ways to further improve them.