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LED Lighting and Control

CONTROLLING MACHINE VISION LIGHTING

Lighting Controllers Enhance Measurement Reliability

Illumination is the most critical component of machine vision systems because a poor-quality image makes it more difficult to get reliable data. Gaining precise control of your lighting can be crucial, particularly since factors such as the direction, wavelength and intensity of the illumination can all affect the captured image.

Controlling Machine Vision Lighting

Consistent light levels are essential to guarantee repeatable results in Machine Vision systems. Typical systems that monitor, regulate, check, analyse, sort or classify products need high precision and repeatability, and in many industries, only 1 in 100,000 reject products can be tolerated. To meet such high tolerances, the reliability of the system measurements needs to be even better. For example, if you are making a simple caliper measurement then a 10% reduction in light level can typically cause a change in the measured values of around 0.5% which can severely affect the reliability. For this reason, light intensity must be closely regulated.

A number of factors will affect the intensity of LED lighting. These include the age and temperature of the light and external factors such as ambient light or dirt on the light. Although some machine vision lights have a voltage rating, their light output is actually controlled by the current through the LED and not the voltage across it. In fact, a very small voltage change will cause a much larger change in brightness. For example, a 1% decrease in voltage can cause a 10% reduction in light output. For this reason, a lighting system that is driven by a voltage source will be inherently susceptible to any electrical interference or variation in power supply.

Gardasoft controllers drive lighting with a constant current drive which will give stable and repeatable light output. For simple applications involving a single light, the entry level RC120 will provide stable and repeatable illumination for machine vision systems. This controller has an Ethernet interface and can be easily configured using its internal webpages.