Individual LEDs may have narrow spectral bandwidth, but multiple LEDs can be chosen so that their resultant spectra is broad.
Why manufacturers do not build spectrophotometers with LED sources, given their high stability, quick stability time, low cost, and small size, with no heating issues? Why still halogen, tungsten, xenon, krypton, etc are used?
Additional: If there is any problem with using LEDs, any suggestion how it can be addressed?
Probably difficult to mix them and collimate them collinearly... unless fibre coupled.
Heyy!!
Warm greetings
I just googled to if there are any LED based spectrophotometers and found some website which mention that there are a few spectrophotometers which use LED clusters specially in Fluorescence Spectroscopy. Please check these links.
http://www.olisclarity.com/led-sources
http://oceanoptics.com/product-category/led-sources/
Hey Raghu
I have seen these products. These are individual light sources. What I am looking for is a way to 'mix' the light from various sources and then channel it towards, say a cuvette.
Probably difficult to mix them and collimate them collinearly... unless fibre coupled.
According to what you say, individual LED's have a narrow bandwidth; to perform as a white light source, you need a continuous of LED's at different wavelengths for them to perform as a white light source. It looks a bit cumbersome, if possible to achieve at all. You can try to do the math of how many you need in order to cover the spectrum you are interested in.
To mix light sources of different wavelengths you can use dichroic mirrors. That is fairly standard; but these mirrors are normally expensive.
So, I guess that is a reasonable explanation; it would be too expensive, and it would be too cumbersome to align everything, for a gain that doesn't seem to crucial, right?
Light can always be mixed by diffusive coatings..its something else which we might be missing. What'd you say?
Dr. Peter
Yes, I do respect their answers. What I mean by 'missing' is that I am missing something which is so obvious why manufacturers don't use LEDs.
Yes, the factors listed down by you are all relevant, along with stability (or wavelength drift).
What I'm chasing is a multi-LED source, which can solve the problem of waiting for warm-up time, unnecessary heating and second order overlapping (on first order).
Carratino's answer is interesting. You probably can try it out and get the math part right.
UV LED and VIS LED may requires different approach for controlling them. Fruthermore even if they have good intensity they have large aperture and it is therefore very difficult to combine them in an optical fiber .
On our side we have developped a LED spectrometer but with direct illumination in the media in order to avoid loosing light : http://indatech.eu/spot4line-led-spectrometer-2/
See: Article Method for building a portable near infrared photometer base...
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