Sunday, May 5, 2013

Does LED size matter?

The machine vision industry is pretty small, so when it comes to developing new technology we tend to hang on to the coattails of the big boys. Lighting is a good example. I think I’m right in saying that no one is developing LEDs for machine vision. Instead, the vision lighting companies have to utilize what’s being churned out for the higher volume applications, like industrial and residential lighting.

These days it seems LED manufacturers are working on ever bigger LEDs, and many are finding their way in to machine vision lights, like the Monster series from Spectrum Illumination. The problem I have with these is that they are prone to creating hot spots. Interestingly, judging by the lens optics diagrams on their website, smartvisionlights has recognized this problem and tries to shape the light to reduce the problem.

Some engineers I work with take the view that a sufficiently thick diffuser is all that’s needed to smooth out the light, but in my view that wastes photons by reducing the total output. I would rather see a higher density of small LEDs, which is the approach taken by CCS in most of their lights. You might notice though that even they’ve jumped on the high intensity – big LED bandwagon.

Now I appreciate that mounting LEDs takes time, which it probably why CCS’s lights are among the more expensive, but I’ve also found the light they put out to be some of the most uniform. I guess you get what you pay for, and I’m willing to pay extra to get more even illumination from a higher quantity of lower output LEDs.

1 comment:

Brian Durand said...

Spectrum Illumination has long offered various lens options as well. For example, most lights are available with 12, 30, or 50 degree optics at no additional charge. Or you can choose wide angle or even line generating optics.

I tend to recommend the large LED "engines" when greater intensity is needed for flooding larger areas, as in robotics. But small fields of view often mean precise inspections demanding a more even illumination source.