PC Monitors: The Evolution of LED Backlights | Hacker News Reader

PC Monitors: The Evolution of LED Backlights

pcmonitors.info

86 pointswalterbell25 comments

Seems like most common backlight is WLED. WLED seems to use bluelight diodes and phosphor. "called ‘white’ LEDs they actually emit a blue light which passes through a yellow phosphor "

This does not sound that good in the light that Chemist recently discovered that blue light speeds up blindness. Hacker News, Phys.org. Maybe a reason why for example submarines uses red light at night.

"Chemists discover how blue light speeds blindness" https://phys.org/news/2018-08-chemists-blue.html https://news.ycombinator.com/item?id=17724995

The red light on subs is there to make it easier on your eyes to adjust to the dark and help with your night vision for looking through the periscope at night.

The reason is your night vision relies on rhodopsin, a compound very sensitive to light but not red light. So red light will give you night vision using the cone cells instead of consuming the rhodopsin in the rods of your retina.

Which is the same reason why astronomers use red lights when using telescopes and most of astronomy related software have modes where the screen have a red filter all over it.

the amount of blue light you get from a monitor pales in comparison to other sources of light, as discussed on HN last week.

> This does not sound that good in the light that Chemist recently discovered that blue light speeds up blindness.

This is a nice example of Chinese whispers at work. No proof was presented that blue light speeds up blindness, and besides that the amount of blue light in normal sunlight pales in comparison with the output of your average monitor. Sunlight is about 1 KW/sq meter, an LCD display is a very small fraction of that (which is why most displays except for e-ink are impossible to read in full sunlight).

It is not blue light but blue LCD. They triggers reactions in retinal molecules that destroy photosensors in the eye.

Surely the light from the sun is a much more damaging? Not to mention computer screens have existed for decades in some form now. I understand the connection with sleep, but Im not sure how much it really damages the eyes compared to other light sources.

Or course sun'rays are damaging, and it is why sunglasses exist. But if you are in front of a computer screen for 7/8 hours a day, you are exposed to blue LEDs which, unlike green and red LEDs are also damging for the eyes.

the amount of blue light in normal sunlight pales in comparison with the output of your average monitor.

Did you mean to write that the other way around?

Yep. Thank you!

It would have been useful to illustrate even just in passing the typical transmission spectrum of the LCD panels themselves. That would help understanding bit more how the spectrum of the backlight impacts the final image.

This article doesn't explain why I dislike looking at the LED backlights in my life whereas I'm fine with looking at my old CCFL backlights for many hours at a time.

It's probably the massive blue peak around 450nm. This wavelength maximally activates cryptochrome protein which might influence the circadian rhythm. In CFFLs the blue is more spread around in the spectrum.

Is there anything special about 450nm?

Literally the second sentence.

For those curious about advancement in LEDs to bring them up to par with the legacy tech described in this article, take a look at Lumenari. (Disclosure: we're investors.) Using software methods to discover and grow novel phosphors to increase color gamut and transmissibility. http://www.lumenariinc.com

Important field as the world transitions slowly -- and then all at once -- to solid state lighting.

Cadmium Free Quantum Dots - I have been wondering if that is something Apple is using on their Retina iMac. The 5K and 4K DCI P3 panels aren't available anywhere else. And they mentioned previous 4K solution had environmental issues which they overcome.

Overall I am still hoping MicroLED could take shape. OLED 's colour accuracy over time, burn in, etc just doesn't seems solvable at the moment.

It will take 10 years before MicroLED screens of monitor or living room sizes are commercially competitive. If it ever happens

I don’t understand what’s wrong with using red, green, and blue LEDs at the edge of the monitor. It should be more energy efficient, since phosphors are inherently lossy. It’ll drastically reduce the accuracy of colors rendered by “white” light coming from white images displayed, but I don’t think users will care much.

The red, green, and blue LEDs will age at different rates. I remember reading that RGB was used in the early days of using LEDs for interior lighting, and that software was being used to compensate and at the same time enable the feature of choosing the white balance.

A paper that discusses these things: http://focs.eng.uci.edu/papers%20for%20GaN/White%20LED/Red,%...

There are deployed lighting systems that internally measure the LED output to compensate for aging. Lumenetix makes one, for example.

Edit: I read the paper you linked. It’s pretty old (2002), and it indeed discusses closed-loop control. Perhaps the technology is just a bit too expensive to put in a monitor.

P.S. the paper also suggests PWM-driving an LED at 120 Hz. This is a horrible thing to do. The frequency needs to be much higher to avoid giving people headaches.

why should I go for a specialist monitor when I can buy a 4k TV?

Panel quality - dead pixels aren't as much an issue if you're 10 feet away.

I would like to see a similar evolution in paperwhite displays. To have a 17" or larger display with a tiling window manager stacked with urxvt terminals running zsh and vim.

I think this would be a great alternative UI conducive to concentrating on coding. And give my eyes a break from a glowing screen. It would also be useful outdoors which might open up new possibilities for sustained outdoor programming.

Reply on news.ycombinator.com