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Would it be possible to get a "white" lighting of a subject by using 3 different lasers (R, G and B)

If so, which wavelengths and proportions should be used ?

  • Why use lasers? Mixing R G and B LEDs can look fairly good. LEDs have a much wider spectrum than a laser. Though the calibration will be tricky since as @Michael Nielsen said, humans and cameras will see the mix differently. – Phil Jan 11 '13 at 17:01
  • To light the subjects with coherent, monochromatic light. – Skippy Fastol Jan 11 '13 at 17:03
  • Are you making a color hologram? – Phil Jan 11 '13 at 17:06
  • @Phil: I confess I am not. – Skippy Fastol Jan 11 '13 at 17:09
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    Your problem has an infinite number of solutions. Basically, almost any R, G and B wavelengths can be combined to make almost any white. The problem is is that, although your white source will have the intended color, it will also have a catastrophic color rendering index – Edgar Bonet Jan 14 '13 at 10:47
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You can get white LED lights that like monitors do actually create white from combinations of very narrow bands of R, G and B light - we perceive it as white of a certain "Kelvin" balance, but if you use a spectrometer, you will see spikes.

http://www.ecse.rpi.edu/~schubert/Light-Emitting-Diodes-dot-org/chap20/chap20.htm

The same goes for fluorescent lights:

http://web.ncf.ca/jim/misc/cfl/

Compared to old light bulbs and halogen the benefit is that they don't emit IR light, ie. waste so much power on heat, which is why we see them as brighter at lower watts. However, cameras will see them as really dim, because the integration of the sensor's sensitivity curve times the emitting source curve ends up rather small, with all those spikes.

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No. "White" light contains all wavelengths of light - the Kelvin temperature just affects the proportions of each wavelength. Three lasers will have just three specific wavelengths so can't possibly reproduce the full spectrum of light that is in white light.

  • Could you please expand a little bit more ? How would a person lit with equal proportions of R, G and B lasers look different from it she were lit with a white light ? Would the CCD sensor of a camera be able to "feel" the difference ? If that is not possible, then how are monitors able to display color images from only red, green and white pixels ? – Skippy Fastol Jan 11 '13 at 16:00
  • Maybe this will help: photo.stackexchange.com/questions/10385/… – David Rouse Jan 11 '13 at 16:15
  • What if your lasers very closely matched the primaries used by the R, G, B filters in your camera? – mattdm Jan 11 '13 at 17:20
  • @mattdm: how may I know about those filter's frequencies ? – Skippy Fastol Jan 14 '13 at 17:21
  • @Skippy: Good question! I imagine it varies slightly from sensor model to sensor model. – mattdm Jan 14 '13 at 17:35

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