Screens
Type of screens
LCD
Liquid Crystal Device (or Display). Liquid Crystals are long thin, rod-like molecules that have physical properties that depend on direction, but can flow like a liquid. Application of an electric field causes the liquid crystal to align in the direction of the applied field. Contact with an appropriate surface also aligns the molecules in some predetermined direction. A conventional LCD operates by ensuring that the optical appearance of the surface aligned liquid crystal is different to that of the field aligned state. For example, one state may be bright and the other dark, thereby giving optical contrast.
OLED
Organic Light Emitting Diodes. There has been much interest in the emergence of OLEDs and Light Emitting Polymers (LEPs) that perform in a similar fashion to the LEDs used in early digital wristwatches but with lower power consumption and easier fabrication methods.
PLED Polymer Light Emitting Diode is one type of OLED based on polymeric organics
STN
Supertwist Nematic is used in most mobile phones and PDAs today. A type of LCD display technology. STN uses less power and is less costly than TFT technology, but at the expense of image quality and response time.
TFD
Thin Film Diode. A type of LCD display technology. TFD technology combines the excellent image quility and fast response times of TFT, with the low power consumption and low cost of STN.
TFT
Thin-Film Transistors are used to generate the appropriate signal at each pixel in Active Matrix Displays.
ZBD
Zenithal Bistable Device is a new type of Passive Matrix LCD that has an appearance at least equivalent to Active Matrix LCDs, combined with substantially lower operating power and image storage. It uses a grating surface capable of defining two or more different stable states in which the liquid crystal molecules have different orientations in the plane normal to the cell (the zenithal plane).
Screen quality factors
Active/Passive
A display is said to be passive when applying appropriate signals to the edges of the panel can create the image.
For example, the STN type of display used in most PDAs is passive matrix: voltages are applied to the rows and the columns so that a high voltage appears at some pixels and a low voltage appears at others.
The voltage difference is related to the number of lines addressed, so display complexity of conventional Passive Matrix modes is limited. One solution is to use Active Matrix, where a thin-film transistor (TFT) is fabricated directly onto the glass substrate behind each pixel
Color Quality
1 bit - Black and white
4 bit - 16 colors
8 bit - 256 colors
12 bit - 4096 colors
16 bit - 65 536 colors
18 bit - 262144 colors
24 bit - 16 777 216 colors
32 bit - 4 294 967 296 colors
a simple counting som can get you to the number: 2^bit. There is no reason to enhance the 32bit screen due to the Human eye that can see only a diversion of 2-3 million colors.
Resolution
When working with screen resolution we talk about pixels. Pixels are simply blocks of color (R/G/B) arranged in a grid. The grid makes up whatever image you are looking at.
A screen and an image can both be measured in pixels. We use the term ppi or Pixels Per Inch. This specifies how many pixels represent a linear inch of an image or monitor screen.
With mobile phones (due to the small amount) we don't use ppi but just say the amount of pixels on the horizontal line and the line down. You get something like 160x128
Size
How big the visable display is measured in cm or inch.
Reaction time
If pixels change intensity/color at the same time it takes some time to change the light intensity. On high-end TFT-screens this reaction time is between 20 milliseconds and 40 milliseconds. On the cheaper models the reaction time is 50 milliseconds or even more (like STN). If the reaction time is greater then 40 milliseconds the display in fast action scenes will be slowed.
Contrast/Brightness
When the flatpanel has to show a black background the pixels don't pass light but in practice it never works 100%. Because that the black images are more very dark gray. A TFT get a 300:1 rate wile a CRT gets 500:1 contrast rate.
Brightness or how much light is emited or cd/mІ. the backlight is most reponsable for STN screens.
Source: Kristof.Vanriet from the mobile-review.com forums
LCD
Liquid Crystal Device (or Display). Liquid Crystals are long thin, rod-like molecules that have physical properties that depend on direction, but can flow like a liquid. Application of an electric field causes the liquid crystal to align in the direction of the applied field. Contact with an appropriate surface also aligns the molecules in some predetermined direction. A conventional LCD operates by ensuring that the optical appearance of the surface aligned liquid crystal is different to that of the field aligned state. For example, one state may be bright and the other dark, thereby giving optical contrast.
OLED
Organic Light Emitting Diodes. There has been much interest in the emergence of OLEDs and Light Emitting Polymers (LEPs) that perform in a similar fashion to the LEDs used in early digital wristwatches but with lower power consumption and easier fabrication methods.
PLED Polymer Light Emitting Diode is one type of OLED based on polymeric organics
STN
Supertwist Nematic is used in most mobile phones and PDAs today. A type of LCD display technology. STN uses less power and is less costly than TFT technology, but at the expense of image quality and response time.
TFD
Thin Film Diode. A type of LCD display technology. TFD technology combines the excellent image quility and fast response times of TFT, with the low power consumption and low cost of STN.
TFT
Thin-Film Transistors are used to generate the appropriate signal at each pixel in Active Matrix Displays.
ZBD
Zenithal Bistable Device is a new type of Passive Matrix LCD that has an appearance at least equivalent to Active Matrix LCDs, combined with substantially lower operating power and image storage. It uses a grating surface capable of defining two or more different stable states in which the liquid crystal molecules have different orientations in the plane normal to the cell (the zenithal plane).
Screen quality factors
Active/Passive
A display is said to be passive when applying appropriate signals to the edges of the panel can create the image.
For example, the STN type of display used in most PDAs is passive matrix: voltages are applied to the rows and the columns so that a high voltage appears at some pixels and a low voltage appears at others.
The voltage difference is related to the number of lines addressed, so display complexity of conventional Passive Matrix modes is limited. One solution is to use Active Matrix, where a thin-film transistor (TFT) is fabricated directly onto the glass substrate behind each pixel
Color Quality
1 bit - Black and white
4 bit - 16 colors
8 bit - 256 colors
12 bit - 4096 colors
16 bit - 65 536 colors
18 bit - 262144 colors
24 bit - 16 777 216 colors
32 bit - 4 294 967 296 colors
a simple counting som can get you to the number: 2^bit. There is no reason to enhance the 32bit screen due to the Human eye that can see only a diversion of 2-3 million colors.
Resolution
When working with screen resolution we talk about pixels. Pixels are simply blocks of color (R/G/B) arranged in a grid. The grid makes up whatever image you are looking at.
A screen and an image can both be measured in pixels. We use the term ppi or Pixels Per Inch. This specifies how many pixels represent a linear inch of an image or monitor screen.
With mobile phones (due to the small amount) we don't use ppi but just say the amount of pixels on the horizontal line and the line down. You get something like 160x128
Size
How big the visable display is measured in cm or inch.
Reaction time
If pixels change intensity/color at the same time it takes some time to change the light intensity. On high-end TFT-screens this reaction time is between 20 milliseconds and 40 milliseconds. On the cheaper models the reaction time is 50 milliseconds or even more (like STN). If the reaction time is greater then 40 milliseconds the display in fast action scenes will be slowed.
Contrast/Brightness
When the flatpanel has to show a black background the pixels don't pass light but in practice it never works 100%. Because that the black images are more very dark gray. A TFT get a 300:1 rate wile a CRT gets 500:1 contrast rate.
Brightness or how much light is emited or cd/mІ. the backlight is most reponsable for STN screens.
Source: Kristof.Vanriet from the mobile-review.com forums
mobilelife - 2004-12-30 19:07
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