Difference between LCD and CRT

Key Difference: LCDs (Liquid Crystal Display) are displays that use liquid crystals sandwiched between two sheets of polarizing material. The images are displayed when electrical charge is applied to the crystals. CRTs (Cathode Ray Tube) are vacuum tubes that use electron guns and fluorescent screens to display images. CRTs and LCDs vary greatly and LCDs are replacing CRTs in today’s world. LCDs are lighter, slimmer and consume less power compared to CRTs. However, CRTs have a sharper image quality compared to LCDs.

LCDs (Liquid Crystal Display) are displays that use liquid crystals sandwiched between two sheets of polarizing material. The images are displayed when electrical charge is applied to the crystals. An LCD uses a select type of liquid crystal known as twisted nematics (TN), which are twisted in shape. Applying a current to these crystals causes them to unwind to a certain degree depending on the voltage. A LCD is in a layer formation, it starts with a mirror on the back for reflection, followed by a piece of glass that has a polarizing film on the bottom side, and a common electrode plane made of indium-tin oxide on top. After that is a layer of liquid crystals, followed by another piece of glass with an electrode and another polarizing film, which is at a right angle to the first one. The LCD is then hooked up to power source that provides a charge to the crystals and causes them to create an image on the screen. LCDs also have a backlight that makes the image visible to the user.

CRTs (Cathode Ray Tube) are vacuum tubes that use electron guns and fluorescent screens to display images. A heated filament or ‘cathode’ is in a vacuum in a glass tube, while an electron gun pours electrons into the tube and the electrons are attracted by the positive anode in the tubes. The screen is coated with phosphor, which glows after is hit by the electron gun. Color CRTs have three different electron guns, one for each primary color. A shadow mask, thin metal screen filled with holes, is used to control the points where the electron beams passes to focus on a single point on the CRT’s phosphor surface. Another method is an aperture-grill, which uses tiny vertical wires. Aperture-grill displays are more expensive compared to shadow mask CRTs. However, CRTs are becoming obsolete as it is being replaced by LCDs, OLEDs, Plasmas, etc.

CRTs and LCDs vary greatly and LCDs are replacing CRTs in today’s world. LCDs are lighter, slimmer and consume less power compared to CRTs. LCDs also give off less radiation compared to CRTs. However, CRTs have a sharper image quality compared to LCDs. LCDs can face with the problems of dead pixels, where a pixel dies and leaves small dot on the screen that does not change; whereas CRTs can face with burn-in problems. Other differences are listed below:

 

LCD

CRT

Size (screen viewable size)

Viewable size is reduced by 0.1”

Viewable size is reduced by 0.99” to 1”

Thickness

Minimum 1 inch; Pretty slim

Bulky due to the heavy back

Weight

Lighter

Heavier

Image Quality

Slightly less sharp images

Sharper images

Energy Consumption

Consumes less energy

Consumes more energy

Refresh Rate

Needs refresh rate (72hz minimum)

No refresh rate (fixed at 72hz)

Screen Flatness

100% 90 degree flatness

Only Mitsubishi and Sony’s aperture grille are 100% flat, rest are not

Radiation

Small amount of radiation

Has a significant amount of radiation

Glare

Less glare

More glare

Automatic Readjustment

Auto resize button; readjusts the pixels

The Auto-fit does not properly readjusts the image

Burn-In

Doesn’t not face burn-in; but susceptible to image persistence

Burn-in can occur

Running Temperature

Cooler than CRT

The back gets warm

Dead / Stuck Pixel

Can happen

Doesn’t happen as images are “painted”

Price

Expensive compared to CRT

Cheaper

Resolution

Native resolution works best, other resolutions may lose image quality

Can be used till max resolution without losing image quality; has multiple resolutions

Contrast

15000:1

Ratio changes according to types. Can range from 150:1 to 250:1

Life Span

60,000 hours

Approximately 43,800; depends on usage

Colors

32 bit

8-bit max, 16.7 million colors.

Viewing Angle

Depends on the technology

Wide viewing angle

Blackness

Blackness varies from dark gray to gray

True black

Benefits

Panels weigh less than plasma; use less energy; light; thinner; emits less electromagnetic radiation; no bleeding or smearing

Easy to move as cannot be wall mounted; good picture quality; cheaper; wide viewing quality; sharper image quality; multiple resolutions

Limitations

Picture slightly less natural and "filmlike" than plasmas; slower refresh rate; limited viewing angle; blacks are brighter; susceptible to burn-out and image persistence; dead or stuck pixels may appear

Heavier, small screens; old technology (obsolete); susceptible to burn-ins

Image Courtesy: cnet.com, clickbd.com

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