In this post, we will tell you what is a liquid crystal display (LCD)? And how does it work? We will explain to you in very easy language.
A liquid crystal display is a thin, flat panel used for the electronically displayed information. It is an electronically modulated optical device made-up of any number of pixels filled with liquid crystal. LCD is a type of light modulating display device. LCD technology does not directly emit light in order to create visualizations, it rather modifies the transmission of light to represent images. On the other hand plasma displays, CRT led devices are light-emitting display devices.
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Parts of LCD (Liquid Crystal Display)
1)Liquid crystal: A liquid crystal is a state between a solid and a fluid. For example, a liquid crystal can flow like a liquid, but its molecules can be oriented like a crystal so that polarization of light can be used to display objects.
2) CCFL Backlight: Cold cathode fluorescent lamp. The backlight is a series of light tubes located behind the screen. The LCD screen does not emit light by itself. It only acts as a filter to block light on a per-pixel basis.
3) Polarizer: A polarizer is an optical filter that allows light waves of a specific polarization to pass and blocks light waves of other polarizations. It can convert a beam of undefined or mixed polarization light into a beam of well-defined polarization, which is polarized light.
Working of LCD (Liquid crystal display)
The LCD works on the principle of blocking light. When manufacturing the LCD, a mirrored mirror is arranged at the rear.
Pixel on
Step1: With no voltage applied across the pixels, the LC plates are joined by rubbing of the glass plates.
Step 2: The light entering the first polarization turns and exits the second polarization “pixel is on”
Step 3: As a result, a little light is allowed to pass the polarized glass through a particular area of the LCD. Thus that particular area will become dark compared to others.
Step4: When there is no current, the light passes through the front of the LCD it will be reflected by the mirror and bounced back.
Pixel off
Step1: The principle behind the LCD’s is that when a voltage applied across the pixels, the LC molecules untwist to align with the electric field.
Step2: Light entering the first polarizer cannot exit the second polarizer “pixel is OFF” and low light.
Types of LCD (Liquid Crystal display)
Passive matrix: scanned one pixel at a time.
- Only used in low-resolution displays such as a watch, a calculator.
- Slow response time.
Active matrix: scanned one row at a time.
- Used in high-resolution displays such as Laptop and TV
- Faster response time
| Advantages | Disadvantages |
|---|---|
| Screen shape: completely flat screen | Costly as compared to CRT |
| Thin and compact. | Poor contrast color due to poor black level |
| Lower power consumption | Resolutions are fixed |
| Provides excellent contrast | In high temperature environments there is loss of contrast. |
