Is mixed light the same as interfered light?

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Mixed light, such as that from an RGB LED or multiple IR LEDs, is not the same as interfered light because it lacks coherence, which is essential for producing clear interference patterns. In a Fourier Transform Infrared Spectroscope, coherent light is necessary to achieve the desired results from the Michelson interferometer setup. Using non-coherent light would result in overlapping interference patterns, leading to a blurred outcome rather than distinct signals. Therefore, the complex system of mirrors is crucial to maintain coherence and obtain accurate spectral data. Coherent light sources are essential for effective interference in spectroscopic applications.
hsherwood68
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Hey all!

I'm building a simple low cost Fourier Transform Infrared Spectroscope as a summer project. for those unaware, the process involves a Michelson-style interferometer which takes a coherent source and splits it. One ray is reflected directly back whereas the other ray has a path difference introduced by a mirror at a different distance. The mirror is moved by small amounts and the combined and interfered light is passed through the sample. on the other side the signal has an FFT algorithm applied to it and a plot of wavelength vs. absorbance can be recovered.

My question is about light. I was planning to use an RGB LED or a series of IR LEDs of different wavelengths and change their brightness like so:



Is mixing different wavelengths of light the same as interfering light? is there any chance that I could avoid this complex system of mirrors and go for LEDs instead?

Thanks!
 
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I don't think so. I don't believe your light would be coherent, which is what you need to see the interference pattern. I think non-coherent light just makes a bunch of overlapping interference patterns with the end result being a big blur.
 
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