The document discusses liquid crystal displays (LCDs), explaining their function, advantages, and disadvantages. LCDs are thin panels that modify light to display images and can produce a wide range of colors through sub-pixels. Compared to CRTs, LCDs are more space-efficient, consume less power, and have a longer lifespan, but face challenges with contrast, motion artifacts, and viewing angles.

1. LIQUID CRYSTAL AND
DISPLAY APPLICATIONS
MONIKA
M.SC. APPLIED PHYSICS
Topic: Display Applications

2. What is LCD??
Liquid crystal display (LCD) is
 a thin, flat panel used for electronically displaying
information such as text, images, and moving pictures.

3. LCD does not directly emit light in order to create
visualizations, it rather modifies the transmission of light
to represent images.
Light EMITTING
Display Device Light MODULATING
Display Devices.
Plasma displays, CRT and OLED devices

4. How this Stuff Works??

5. Working…
No Voltage applied across the pixel
Molecules twist to align the rubbing of the glass plates.
Light entering 1st polarizer is twisted and can exit the 2nd polarizer
Pixel is ON
Voltage applied across the pixel
Molecules untwisted to align with electric field.
Light entering 1st polarizer cannot exit the 2nd polarizer
Pixel is OFF

6. Color Display
Each pixel has three sub-pixels: Red, Green and Blue.
Different intensities of the sub-pixels give perception of
whole spectrum of colors.
If each red ,green and blue sub-pixel can display 256
different intensity of their respective color , then each pixel
can produce a possible palette of 16.8 million
(256*256*256) colors

7. Types of LCD
 Passive Matrix
 Active Matrix
Passive Matrix Liquid Crystal Display
Uses a grid of vertical and horizontal conductors comprised of Indium Tin Oxide
(ITO) to create an image
Each pixel must retain it’s state without a steady electric charge
Scanned one pixel at a time
Poor contrast, and very slow response times
Only used in low-resolution displays (such as watch, calculator)

8.  Cross talk occurs when neighboring pixel voltages affect each
other, reducing the gray scale, contrast, and viewing angle.
 Submarining occurs when slow-to-respond LC materials cannot
respond quickly enough and the picture can disappear temporarily.
 One Solution: placing a switch at each pixel, such as a transistor or
diode --> pixel matrix becomes “active.”
Passive Matrix Display Problems

9. Active Matrix Liquid Crystal Display
 It is based on Thin Film Transistor (TFT) Technology
 Switching element at each pixel. Individual pixels isolated from each other.
 Each row line is activated sequentially (Scanned one row at a time)
 Used in computer displays
 A switching device and a storage capacitor are integrated at the each cross
point of the electrodes.

10. Advantage of Active Matrix Display
• Higher sizes
• Higher contrast
• Higher gray scale
• Higher resolution
• Higher viewing angle
• Faster response.
• Better control of the color

11.  Smaller size —LCDs occupy approximately 60 percent less space than CRT
displays.
 Lower power consumption—LCDs typically consume about half the power and
emit much less heat than CRT displays.
 Lighter weight —LCDs weigh approximately 70 percent less than CRT displays of
comparable size.
 No electromagnetic fields —LCDs do not emit electromagnetic fields and are not
susceptible to them. Thus, they are suitable for use in areas where CRTs cannot be
used.
 Longer life —LCDs have a longer useful life than CRTs.
Advantage Of LCD Over CRT

12. Disadvantages of LCD
Aspect Ratio aspect ratio and resolution are fixed.
Black-Level Not proficient at producing black and very dark grays. In a "standard"
configuration, not appropriate for use in dimly lit and dark conditions.
Contrast Lower contrast than CRTs due to a poor black-level.
Motion Artifacts
Slow response times and scan rate conversion result in severe motion
artifacts and image degradation for moving or rapidly changing
images.
Resolution procedures which can cause considerable deterioration of the image.
Viewing Angle Restricted viewing angles. Viewing angles affect the brightness,
contrast and colors shown.

14. Bibliography
 http://bootstrike.com/Articles/LCDvsCRT
 http://www.explainstuff.com/lcdtv.html
 http://www.slideshare.net/
 https://www.youtube.com/watch?v=Bf3547WB5qs
 Liquid Crystal Displays: Fundamental Physics and Technology by Robert H. Chen