From what I understand a computer monitor can output lots (couldn't think of a better word) of colours. Is it possible for a computer monitor (television etc) to output light invisible to the human eye?
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\$\begingroup\$ your TV remote does, why not the TV itself. Hey, CRTs output a small amount of X-ray radiation! \$\endgroup\$– KortukCommented Jan 11, 2012 at 17:03
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\$\begingroup\$ Hi Kortuk, that's what I was thinking. I'm wondering whether computer monitors could output infra red (I don't think they can), but maybe a range of light close to infra red? Thanks for the comment. \$\endgroup\$– Alex KeySmithCommented Jan 11, 2012 at 17:05
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2 Answers
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It depends on what kind of monitor you are talking about. Modern LCD screens use a backlight to produce the light, which is then filtered through the LCD panel. The backlight for most displays is a mini-CCFL, or "cold cathode fluorescent lamps." These can differ in output spectrum, but the do produce a significant amount of infrared radiation outside of human vision.
For instance, here's a spectrum plot for a flourescent light, like you'd find in an office environment:
The spectrum for human vision is listed below:
answered Jan 11, 2012 at 17:13
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\$\begingroup\$ Gallamine - good comment. But, despite the out of band components when a CFL backlight is used, I think you'll agree that the LCD itself will laregly remove any non visible components and that any that it does not remove are not there intentionally and are not part of the formal display process. No? \$\endgroup\$– Russell McMahon ♦Commented Jan 11, 2012 at 22:24
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\$\begingroup\$ @RussellMcMahon you're probably correct. I can't find my spectrometer, or else I'd take a measurement now. It wasn't clear to me whether the OP was asking about whether the display intentionally could source non-visible light, or they were just asking if it were possible. \$\endgroup\$ Commented Jan 11, 2012 at 22:56
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\$\begingroup\$ @Gallamine - I think we are generally in agreement :-). I was also unsure whether he meant it as part of planned/controlled output or not, but decided for the former. Correctly as it trns out, but that was happenstance. \$\endgroup\$– Russell McMahon ♦Commented Jan 11, 2012 at 23:26
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\$\begingroup\$ I stumbled over this question/answer when I was searching for information about blue filter glasses. Probably many of us are working at a desk for many hours per day and I notice my eyes adapt to this situation.. however, I stumbled over so-called blue filter glasses which are designed for office people. But when I see a spectrum like above I'm not sure whether they make sense as the emission of blue light isn't so much compared to the other wavelengths. What do you think? \$\endgroup\$– BenCommented Dec 29, 2018 at 11:52
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The actual screen cannot and does not purposefully output light which is not visible to a normal human eye.
As Kortuk notes, there may be some secondary emissions caused by effects which are unrelated to inyended display generation. I do not understand that to primarily be what you mean.
You could argue that the screen gets warm and emits invisible infrared radiation (and it does, at a variable rate depending on the technology used) but this is a second order effect not intentionally related to the display process.
It would be possible to design a monitor using some technologies which could output invisible light. For example, a phosphor could be used which was IR or UV emitting.
The colours emitted for display purposes by all standard screens are inside the colour space which a normal human eye can see.
Then, there's Octarine :-)
Gargoyle knows.
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This is a truly vast and complex subject. I have been dabbling in the shallow s for many years with respect to colour printing, colour photography and video display and always find that the depths of specialist knowledge involved is beyond what sanity allows an information omnivore to assimilate - it is a full time task for those who wish to be so involved.
As a starter
From Wikipedia Gamut
- A typical CRT gamut. The grayed-out horseshoe shape is the entire range of possible chromaticities, displayed in the CIE 1931 chromaticity diagram format (see below). The colored triangle is the gamut available to a typical computer monitor; it does not cover the entire space. The corners of the triangle are the primary colors for this gamut; in the case of a CRT, they depend on the colors of the phosphors of the monitor. At each point, the brightest possible RGB color of that chromaticity is shown, resulting in the bright Mach band stripes corresponding to the edges of the RGB color cube.
Gamuts are commonly represented as areas in the CIE 1931 chromaticity diagram as shown below, with the curved edge representing the monochromatic (single-wavelength) or spectral colors. The accessible gamut depends on the brightness; a full gamut must therefore be represented in 3D space - see Wikipedia ref for 3D drawings.
Excellent overview here
Sharp aims at increasing colour gamut displayavle with 5 colour display (2009) here
TV & monitor phosphors
Film coverage
Human eye coverage - typically
Vast amounts here - each image linked t a page - many relevant to some extent.
Related / interesting
Light, colour and human vision
answered Jan 11, 2012 at 17:09
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\$\begingroup\$ Thanks for the great response, +1 from me. You're right I'm more after whether it is possible to purposefully output non visible light. Maybe even writing a program to output it... but that's for another day / another question :-) \$\endgroup\$ Commented Jan 11, 2012 at 19:12
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\$\begingroup\$ @Ruslan I assume they came from the Sharp article - link broken :-( - maybe not. | Koday Prophoto gamut is wider BUT no guarantee any filme covered it. A quick look around tiurned up no good results on any actual films. Will try to find something better. \$\endgroup\$– Russell McMahon ♦Commented Mar 28, 2020 at 12:24