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Disclaimer: I am not an electrical engineer, and nowhere near studying it either. This is just a curious question which I got and couldn't find an answer to.

I am aware of how several pixels are used to make up a television screen. Each pixel consists of 3 LEDs; one red, one blue, and one green. By varying the intensity of either the red, green, or blue; it's possible to bring about any possible color that exists.

My question is, what are the wavelengths of the light that these blue, green and red LEDs emit? Does it depend on TV to TV or is it general?

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    \$\begingroup\$ You would have to read the datasheet of the product to figure it out. \$\endgroup\$
    – PlasmaHH
    Nov 2, 2017 at 9:46
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    \$\begingroup\$ Most TV screens do not use RGB LEDs, they use white LEDs as backlight and an LCD screen used as color filter to make the colors. On this page: en.wikipedia.org/wiki/Color there is a table showing which wavelength corresponds to which color. The emitted wavelength of any LED depends on how it is build up (materials used etc). There cannot be one answer as there are more combinations possible to make a color range. As PlasmaHH says you can find what an LED emits in its datasheet. \$\endgroup\$ Nov 2, 2017 at 9:52
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    \$\begingroup\$ Despite what you may have heard, a combination of three colours RGB DOES NOT make any colour. It is still only a mix of three colours. Your eye, and brain, interpret that mix as different colours, and the RGB mix gives you a reasonable facsimile. If you add yellow into the mix, the facsimile is better. Ultimately, you would need all wavelengths to be truly life-like. \$\endgroup\$
    – Trevor_G
    Nov 2, 2017 at 15:39
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    \$\begingroup\$ @Bimpelrekkie, OLED TVs are in stores now. Time to throw out your old set and buy a new one. bestbuy.com/site/clp/learn-about-oled/… \$\endgroup\$ Nov 2, 2017 at 16:57
  • \$\begingroup\$ @jameslarge I know that's why I wrote "Most TV screens..." Sure let's create even more E-waste by all replacing our TVs. I do not see the need. My LCD TV is good enough. OLED is too expensive anyway. \$\endgroup\$ Nov 2, 2017 at 18:24

2 Answers 2

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First off, leds typically transmit on a narrow band of wavelengths, shown below are the curves for a blue, green and red LED.

enter image description here

You can see how they match up to the response of the human eye, so with only three colors, you can cover a wider range of colors. Usually with a TV they use an LED that covers more wavelengths than a standard LED.

They also go through the effort to match brightness and calibrate the LED's to a known color standard so that the color you see from the matches that of the media played and the camera that recorded the media.

enter image description here

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  • \$\begingroup\$ Wait a minute, are you saying that by calibrating the LED, you can shift the wavelengths at which it emits? \$\endgroup\$ Nov 2, 2017 at 16:13
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    \$\begingroup\$ Nope, but you can adjust the brightness of the LED and the way your eye perceives that color. Some TV's have a calibration mode, some are better than others \$\endgroup\$
    – Voltage Spike
    Nov 2, 2017 at 16:13
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By varying the intensity of either the red, green, or blue; it's possible to bring about any possible color that exists.

That's not quite true.

enter image description here

Figure 1. The CIE colour space and the colour space available with RGB sources marked at the vertices of the triangle.

  • If we had green and red light sources as shown above then we could vary the relative intensity of each to simulate any wavelength (colour) along the line from green to red. We are not generating the colour in question - it's just that the eye perceives it as such.
  • If we now add in a blue light source we can generate any colour within the triangle but not outside it.

My question is, what are the wavelengths of the light that these blue, green and red LEDs emit? Does it depend on TV to TV or is it general?

It will vary. If you look at an LED datasheet you will see, for example, that the manufacturer offers "binned" LEDs. These LEDs have been graded after manufacture for light intensity and colour tolerance. A better display will have well matched LEDs and, for maximum range of colours, will have the R, G and B points as far apart in the colour space as they can for the target price.

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