What are LCD and LED?
LCD stands for liquid crystal display. Liquid crystal is a kind of material that is neither liquid nor a solid, it comes in between these two states of matter. It has properties similar to that of the crystallised solid. The arrangement of molecules is in a fixed pattern however they are not fixed in shape or form.
LED stands for light-emitting diode and it is a semiconductor light source that emits light when current flows through it.
It is a type of flat-panel display that uses an array of light-emitting diodes as pixels for displaying images.
It comprises two sheets of polarising material with a liquid crystal solution between them.
Full-Form of LCD and LED
LCD stands for liquid crystal display.
LED stands for light-emitting diode.
This technology is used in laptops, digital clocks, watches, digital cameras, watches, etc.
There are three types of LCD TVs
Front projection LCDs
Rear projection LCDs
They are usually found in smartphones, televisions, computer monitors and instrument panels and use a liquid crystal display panel to control where the light is displayed on your screen.
There are 3 types of LEDs based on their backlighting methods:
Dynamic RGB LEDs
Working Principle of LCD Monitor
To display anything on the screen, three major components are necessary, they are
Light: A source through which you see the objects.
Colour: To view the objects in different colours otherwise everything on the screen will appear white.
A way to control the light and colour on the screen.
These three components are found in LCD.
LCD uses liquid crystals in its main form of functioning to produce a visible image.
It is a type of flat-panel display technology that uses diodes, small cells and ionised gases for the production of images.
LCD works on the principle of blocking light.
It also works on the modulating property of light where light modulation is the technique of sending and receiving the signal through the light.
A light is non-polarized by nature when passed via a plane. It scatters in different directions and phases as you can see in the image below:
(Image will be uploaded soon)
On placing the polarization filter (either horizontal or vertical) and passing the same light through this filter.
The filter would polarise the light in one phase and produce a clean polarised light which you can see on your computer and TV screens.
The image below shows the polarised light:
(Image will be uploaded soon)
In LCD displays, light emitted from the backlight passes via a vertical polarisation filter after going through the liquid crystal element, this liquid crystal element twists this light wave. The vertically polarised light then turns to a horizontally polarised light. This horizontally polarised light passes via the horizontal polarisation filter allowing the passage of light. Hence the light is visible to us. The voltage we apply to the LCD is applied in such a way that the crystal mechanism of the light is removed and the light acquires a straight pattern. Due to this, the vertically polarised light will come out vertically only, however, the horizontally polarised light will be blocked and we won’t see any light in this case. This is how LCD works on the principle of blocking light.
The image below shows the working of LCD:
(Image will be uploaded soon)
Difference between LCD and LED
Applications of LCD and LED
Here are some applications of LCD:
Portable electronic games
As viewfinders for digital cameras and camcorders
In video projection systems
Here are some applications of LED:
Bulbs and tubes
Automotive heat lamps
Burglar alarms systems
FAQs on Difference Between LCD and LED
1. What is the liquid in the LCD screen?
Liquid crystal displays (LCDs) is a technology comprising liquid crystals that are activated by electric current. The basis of this technology is the liquid crystal, a substance made of complicated molecules (crystallized solids). Like water, liquid crystals are solid at low temperatures, and they melt as you heat them.
2. What are the advantages and disadvantages of using LCD TVs?
There are several advantages and disadvantages of using LCD TVs that are as follows:
They are lightweight, thin, and compact when compared to bulky CRT displays.
It has no geometric distortion.
Perfect sharpness and no bleeding or smearing.
The screens are perfectly flat.
No screen burn-in effect.
Low power consumption. It uses less than half of the power a CRT monitor of the same size would.
Little heat is emitted during operation because of less consumption of power.
Unaffected by magnetic fields.
The ability to have little or no flicker depends on backlight technology.
Emits almost no undesirable electromagnetic radiation.
Can be made in almost any size or shape.
No theoretical resolution limit. Each additional LCD panel increases the total resolution of the display.
Can be made in large sizes of over 80-inch.
LCD grids mask the effects of spatial and grayscale quantization, making the image quality feel higher.
Lifespan gets affected by Direct current flow. Therefore, an Alternating current is supplied for its longevity.
In high-temperature environments, the contrast gets affected.
More electricity consumption.
Not suitable for very bright environments like in sunlight, you can’t view the perfect images.
Displays only one native resolution.
Limited viewing angle, especially in some older or cheaper monitors. This causes colour, saturation, contrast and brightness to vary with the position of the user viewing it.
Dead or stuck pixels may occur after a period of use.
Uneven backlighting in some monitors.
Black levels may not be as dark as required as the liquid crystals are unable to totally block all of the backlights from passing through.
Fixed bit depth (also called colour depth).
Input lag, because the LCD's A/D converter waits for each frame to be completely put out before drawing it to the LCD panel.
Constant use can cause thermalization where part of the screen gets overheated and begins to discolour compared to the rest of the screen.
Loss of brightness and much slower response times in low-temperature environments.
Loss of contrast in high-temperature environments.
3. Which is better: LCD or LED?
Since the power dissipation is less in LED TVs. They can run with greater energy efficiency. They provide a clearer and better picture than the general LCD TVs because these TVs work with a colour wheel or distinct RGB (red, green, blue) coloured lights to produce more realistic and sharper colours.
4. When was the LCD invented?
Liquid Crystal Display was invented in 1968 by electrical engineer George Heilmeier, then working at the RCA laboratories, and his team of scientists. Heilmeier developed the first operational liquid-crystal display based on the dynamic scattering mode (DSM), as he termed it.
In the late 1960s, George William Gray and his team at the University of Hull discovered cyanobiphenyl liquid crystals that had the correct stability and temperature properties for application in LCDs.
In 1970 in Switzerland, Hoffmann-LaRoche, along with inventors Wolfgang Helfrich and Martin Schadt filed for the patent for the twisted nematic field effect (TN) in liquid crystals. They licensed the invention to Swiss manufacturer Brown, Boveri & Cie, which then produced TN displays for wristwatches and other applications for the international markets. Following this, the Japanese electronics industry soon produced the first digital quartz wristwatches with TN-LCDs and numerous other products.
In 1980, the first color LCD televisions were developed as handheld TVs in Japan. Hattori Seiko's R&D group started developing color LCD pocket televisions back then.
In 1984, Epson released the ET-10, the first full-color, pocket LCD television. The same year, Citizen Watch, introduced the Citizen Pocket TV, a 2.7-inch color LCD TV, with the first commercial TFT LCD display.
After a lot of pioneering work and innovations throughout the world in the 80s and 90s, in 2007 the image quality of LCD TVs finally surpassed the image quality of cathode-ray-tube-based (CRT) TVs.
5. What is a dead pixel in an LCD?
Display devices (televisions, computer monitors, smartphones etc.) comprise thousands or millions of individual pixels, depending on the type of display. The pixels perform their intended function by changing colour in response to the image being projected. But at times a pixel can die.
This means that the pixel on the display device can no longer change colour. Dead pixels remain black, regardless of the image that is being displayed. Dead pixels easily stick out and can be spotted by turning the display to a white or bright image.
Mostly the dead pixels are a result of a failed power connection. Pixels require power to change colour. If the power connection to a pixel is cut off, it will become black, and thus a dead pixel.
Dead pixels are different from stuck pixels. Stuck pixels also don’t change colour, just like the dead pixels, but are still receiving energy. So they generally tend to fix themselves over time. While dead pixels are black, the stuck pixels are generally red, green or blue.
Stuck pixels are generally a result of LCD screen manufacturing defects, technical errors, or compatibility issues with some software applications. Old or unused TVs also could develop stuck pixels.