As I sit here in front of my laptop, I am amazed by this piece of technology that reveals what is interpreted as my actions on this keyboard and mouse. I am talking about the display. Have you ever wondered how these things that are less than a centimetre thick work? We are here to discuss the basics of these marvelous inventions. Before we get our hands dirty, it is necessary to understand the properties of a display. In a display, a pixel is the smallest unit which can be modified. Pixel density is the number of pixels in a given surface area. Refresh rate is defined as the number of times the output from the pixel can be changed.
CRT (Cathode Ray Tube)
This is the oldest type of display. It consists of a vacuum tube with an electron gun at the end of the tube. The gun bombards the screen with electrons which causes the phosphor dyes on the screen to be illuminated. This requires its traditionally large size. However, due to the absence of a backlight and bleeding lights, the contrast ratio (the ratio in between the luminosity of the brightest white and the darkest black) is enormous. Still popular among some graphics professionals, this technology is being quickly phased out due to its bulky size and relatively low pixel density.
DLP Projection
Digital Light Processing projectors are a marvel of modern technology, courtesy of Texas Instruments and their signature DLP chip. Their chip consists of millions of little micro-mirrors. These micro-mirrors serve as the individual pixel and control the intensity of reflected light. This technology is highly preferred due to its high refresh rate (as compared to LCD projection).
LCD
Liquid Crystal Displays (LCD) use a very simple mechanism. They consist of a backlight with two perpendicular polarizers in front. These polarizers cut out the light coming from the backlight. Between the two polarizers lie liquid crystals which rotate the polarization of the light coming from one of the polarizers. Depending on the electric field, the intensity of transmitted light in each pixel can be modified. The problem with this technology is that no polarizer is perfect and there is light bleed, leading to a lowered contrast ratio (as the blacks are partially illuminated and therefore not truly black).
LED LCD (also referred to as LED)
Essentially a regular LCD except backlit by light emitting diodes rather than a fluorescent lamp. That’s it… Seriously! We decided to add this to the list due to confusion to the point where people (they were actually in engineering before you start pointing fingers) have attempted to argue with us that current LED displays sold have nothing to do with LCDs. Calling them LED was for sales purposes and would have been like calling previous LCDs fluorescent lamps. The main advantages of LED backlit LCDs over other LCDs is a reduction in their thickness, decrease of power consumption, and, best of all, an increase in contrast ratio.
OLED
The future that may already be in your pocket–organic light emitting diodes (OLED) are already showing up on portable devices thanks to battery life savings due to no backlight. OLEDs contain a organic compound layer that produces light (colours vary depending on the organic compound) when an electrical current is run through it. OLEDs are thinner, lighter, more flexible, consume less power and boast a much a higher contrast ratio compared to that of LED LCDs. There are two reasons why their use isn’t more widespread: 1) Cost; though, like many technologies when they are first introduced, the cost of OLEDs are slowly declining, and 2) Low availability of supplies.
E-INK
E-ink displays are one of the latest developments to be deployed on an end-user product as a viable display technology. E-ink uses millions of charged nanospheres with one side coloured black and the other side white. The black side is attracted to negative charges while the white side is attracted to positive charges. This is used in many low-power purposes such as the Sony Reader, Amazon Kindle and the Motorola F3. The advantages of this display is the low power requirement and no backlight is needed. However, the reason for it not being widely used in other applications is ghosting due to its low refresh rate.
MIRASOL
Imagine a display that looks as crisp as paper, does not have a backlight and delivers a low-power and coloured alternative to LCD screens and e-ink displays for electronic book interfaces. Mirasol is a trademarked technology from the electronics giant Qualcomm. It uses Micro Electro Mechanical Systems (MEMS) to produce interference fringe-based colours. Each pixel consists of a Fabry-Perot interference etalon which reflects a certain wavelength of light depending on the thickness of the etalon. This thickness is modified by the application of an electric field in each pixel. This provides a vibrant display without the need for power consumption (except for when the displayed features are to be changed).
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