Since a good image is essential to the successful performance of every machine vision system, it comes as no surprise that LED lighting controllers can help deliver the best results. Jools Hudson of Gardasoft Vision explains the key considerations for machine vision lighting control.
A good lighting controller will provide the careful and reliable control of illumination intensity that is needed to get the best out of a machine vision system. It can bring enhanced performance, greater versatility and better integration of the lighting system. Key areas of performance enhancement include LED overdriving capabilities and providing outstanding stability of LED intensity output. Added versatility comes through the ability to facilitate the imaging of fast moving products through strobing as well as precision trigger sequencing between vision cameras, lights and other system elements (such as rotary encoders) to allow the automation of complex lighting and imaging sequences. The provision of Ethernet connectivity greatly simplifies system integration, while built-in safety features automatically protect the LEDs from possible damage.
Double bonus from pulsing
LED light controllers allow LEDs to also be operated in pulsed mode where the lighting is switched on only when required. Pulsing enables users to eliminate motion blur from the sensor, thereby freezing the image of fast-moving objects – a crucial requirement in many production line environments. Gardasoft light controllers allow fine adjustment of the pulse timing, which is often more flexible than adjusting the camera timing. Another important benefit that pulsing brings for users is the possibility of ‘overdriving’ the LED. At their specified current rating, LED lights output 100 per cent brightness, but it is possible to increase that by driving short pulses at more than the manufacturer’s current rating. This is particularly useful where light levels are low, such as imaging fast moving objects with very short camera exposure times where additional light intensity is needed to produce good quality images. Using LED lighting control to provide accurate overdriving is a powerful technique for machine vision, but it must be done safely. Gardasoft’s patented SafeSense™ technology does just this. When a light is connected, the SafeSense™ technology determines the actual rating of the light and imposes safe working limits based on the pulse width and duty cycle for overdriving, thus providing full protection. This is particularly important in the high power controllers needed for the latest high power LEDs, given that controllers in the Gardasoft range have options of strobing up to 20A on each channel.
Versatile triggering topologies
The versatility of precision trigger sequencing between the lighting controller, cameras, and other components such as rotary encoders offers a variety of camera triggering topologies. These include traditional triggering arrangements where the camera is triggered by a sensor at the infeed of the manufacturing sub-process, or the sensor triggering the light controller which then triggers the camera. Lighting controllers also make it possible to individually trigger multiple lights at different intensities and durations in a predefined sequence to highlight different features in different images. This allows multiple measurements to be made using a single camera station instead of needing multiple stations.
Find out more
Get a free white paper on the practical use of lighting controllers: http://www.gardasoft.com/practical-use-of-controllers/.