We've recently written about new
OLED TVs,
Nano Lighting LED screens, and other improvements in display technology. One of the advantages the Nano Lighting LED screens poses over OLED is that it's theoretically easier to integrate into existing manufacturing processes. A
new innovation in color filters for LCD displays is hoping to capitalize on this same advantage.
Researchers at the University of Michigan, lead by L. Jay Guo, have designed an optical film that transmits more light, improving the display's power consumption. Here's how it works.
The liquid crystals of
traditional LCD displays are an arrangement of rod-shaped molecules that react to an electric current in predictable ways. Based not he amount of current, the liquid crystals twist to allow more or less light through. In a reflective display, the film of liquid crystals is sandwiched between two layers of perpendicularly polarized glass. In a simple digital watch, for example, light from an external source (the sun or a lamp) is passed through the top level cover of glass, through the polarized layers and liquid crystal film, and reflected off of a mirror back out at you. The liquid crystals react to an electrode in the shape of the blocky number 8 and, depending on the time, parts of that shape are turned off so as to not allow light to pass through. The numbers that you're looking at are actually outlined by light.
In backlit displays—the more common type that we find in our laptops, TVs, phones, etc.—work in one of two ways. In passive-matrix LCDs, red, green, and blue pixels are arranged in a giant grid and the liquid crystals twist when a circuit is created by a positive voltage applied vertically with a ground connection activated horizontally. Active-matrix LCD, the superior and more common design, works by applying voltages to transistors and capacitors arranged on a surface under the liquid crystal film which receive and store voltages. A white light source behind the layers of film shine through and colors are created by carefully controlling the voltage applied to the red/green/blue pigmented subpixels. Unfortunately, a lot of light (and therefore energy) is lost in this process.
The University of Michigan color filters allow 36 percent of the light to pass through the LCD, in contrast to the typical 8 percent of current LCDs. Guo and company's design produces color not by applying charge to activate pigmented pixels, but by controlling the amount of light that passes through tiny slits of various widths arranged in a grid.
It essentially works like the refraction experiment in a science classroom that shows that white light, when passed through a slit, actually separates into its different color (wavelength) components. Guo's research has produced a way to do this efficiently and predictably on a nano-scale. And instead of blocking the light that passes through the top layer of polarized glass, the light is reflected back to a mirror and re-used in the display.
Because it handles light more efficiently, the design requires less energy and would be a welcome addition to battery-based displays. And if the technology really takes off in home electronics, it might mean less money is absorbed by your power bill.
