I used to have a GBA that didn’t have any brightness, I don’t understand how that works, if you turned of the lights you couldn’t see anything. I also don’t get why isn’t it used in modern devices, like using that technology to make a kindle with a colored screen would be cool and useful.
In: Engineering
GBA screens and modern TN LCD screens operate on the same principles, the difference is that the older Game Boy screens had no backlight. Instead they used a reflective layer that backlit the display from ambient light. Modern LCD screens are usually “LED backlit”, meaning there’s an array of LEDs behind the display that provide light through the image.
The reason we don’t use this type of screen much anymore is that it loses utility in low-light environments, and LED-backlit screens have largely become the *de facto* “base level” screen. Reflective LCD screens might be a bit cheaper, but I don’t know that it would be enough to justify the loss of usefulness.
LCD screens work in by blocking light. Modern screens have a backlight that shines outward through a color filter and an LCD filter. All the LCDs do is alter the liquid crystal orientation to block more or less of the backlight.
The Nintendo Gameboy had to deal with being a portable system that ran on AA batteries. The engineers could add a backlight (increasing the size, weight, and cost of the system), but would either have to sacrifice play time before the batteries died or make the system use more batteries*. Instead they opted to use a mirror. The “backlight” is just reflected light. That’s why it didn’t have adjustable brightness, but also why you could play it in full daylight with no issues. The color quality of these screens was not very good. Good color from filters needs a bright source light with plenty of the color you are wanting. A reflective LCD only has the light color available in its environment, so the color quality would change drastically based on where you were at. You need a steady source to guarantee the proper quality and brightness to get a good color image.
Even though this setup is very power efficient, it’s still not as efficient as the Kindle’s e-ink screen. The kindle just uses power to change the displayed image. Once its on the screen, no power is needed to keep it there. An LCD has to continually feed power to the screen to maintain an image.
*Sega took the route of having a backlight and color screen for the Game Gear. It used ~~8~~ 6 AA batteries compared to 4 for the Gameboy, still had worse battery life, and was way larger and harder to carry around.
The modern Light Emitting Diode (LED) technology is based on having tiny little LEDs act as individual light-emitting red/green/blue pixels. The default is “black” with everything off, but adding more power adds brightness to each pixel, and the right combination can get you any color even up to bright whites.
The older Liquid Crystal Display (LCD) technology worked by using a polarized optical filer and tiny crystal cells that would deform under electricity to twist the polarization of light. Basically, light passing through the crystals would be polarized, and if the polarization lined up with the built-in polarizing filter all of that light would come through, but if it were lined up in the perpendicular direction you’d block all the light, and changing the amount of electricity to the crystals would change to what extent you were blocking light from 0% to 100%. This can work either with a white backlight, or by white ambient light coming in (partially blocked) hitting a mirror and coming back out (again partially blocked).
Unfortunately, that old LCD tech isn’t great for things like making a “Kindle color” because the crystals required constant electricity to maintain a given orientation. This is different from modern ePaper technology which uses electricity to move around some little pigment molecules inside a little pixel/cell, but which requires no electricity once those pigments have been parked in place (and is precisely why they have such great battery life, not just the “no backlight” thing). Not all hope is lost, though, as ePaper companies are very much actively working on the technologies needed to incorporate more pigment colors in their displays. It’s just still new and expensive technology and not quite as high-resolution as the more common black-and-white ePaper seen in Kindle screens now.
Only OLED screens are an array of lights, where each pixel is its own light.
Older LCD screens worked more like filters, where each pixel filtered out colors from a backlight or reflector. The original Gameboy and Gameboy Color didn’t have a backlight, and just used a reflective surface to reflect ambient light (similar to what a lot of calculators use). The Gameboy Advance SP was the first one to add an actual backlight.
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