The advantages of using LEDs in machine vision lighting systems

Q. Why are more machine vision systems using LEDs for illumination?
A.  In recent years LEDs (light-emitting diodes) have played a major role in machine vision lighting systems and their use is growing all the time, as cost decreases and performance increases.
Over the years machine vision designers have used cold light sources with fibre optics or high intensity, high-frequency fluorescence illumination. Cold light sources and fibre optics can be ideal in some microscopy applications, where one cannot illuminate the object with a hot light source because it will change the characteristics of the sample, for example in biomedical applications.  However, for machine vision applications these lights are an expensive option and the need for regular bulb replacement in the light source makes the running costs higher and results in down time for planned maintenance.

Q. I see, so its cost. That’s the reason why LEDs are used so much now?
A. Partly, in most machine vision applications you require a constant and uniform light source and this is easer and less expensive to achieve with LEDs than with cold light or fluorescent tubes.

Q. Are LEDs more flexible to use than other types of lighting.
A. Yes. LEDs offer the designer great flexibility. A robust array of LEDs can be manufactured in almost any shape or size cheaper than any other form of lighting system. A solid package of LEDs can be designed to focus its light exactly where you want it in applications where this is required. Incandescent and fluorescent sources often require an external reflector to collect light and direct it in a useful manner.

Q. How does the power consumption of LEDs compare with other systems?
A. They require much less power than other lighting systems. This means they do not need bulky or expensive power supplies and LEDs can produce more light per watt than other types of illumination. 

Q. Are LEDs better for producing stable coloured lighting?
A. Yes. LEDs are available in many different colours so the colour of the light can be tailored to the application. With cold light sources this was only available by using filters. Direct coloured light is more effective and can reduce costs. If a machine vision application requires different levels of light an array of LEDs will not change its colour unlike incandescent lights which changes its colour balance with intensity.

Q. What about lifetime of LEDs?
A. This is another advantage of LEDs. Typically the life time is well over 100,000 hrs. This long life of LEDs compares with fluorescent tubes typically rated at about 10,000 hours, and incandescent light bulbs at 1,000-2,000 hours. LEDs can be pulsed and this does not seem to affect there life in contrast say to fluorescent lamps which tend to burn out quicker if subjected to rapid cycling. Usefully, pulsing LEDs can increase the practical peak light output.

With stable, uniform light and extremely long-life, LEDs are ideal for most machine vision applications. 

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