Video display system
- 1. Video display system By Nihad Mohammed Abdul-Aziz Lecturer name: Hassan K. Rasheed University of Zakho College of engineering Mechanical department Jan 2018
- 2. 2 Introduction: The video display system of PC has two main components, (1) Monitor (2) Video adapter. The monitor display text or graphics information on the screen of Cathode Ray Tube (CRT) or Liquid Crystal Display (LCD). Monitors of desktop use CRT , and laptop use LCD. Monitors today are available in different size like (14-15-17 and 21) inches. (Mathivanan, 2005) LCD Monitors: The LCD are mostly used portable system. Where the screen image is generated on a flat plastics disks that consists of millions of liquid crystal elements for the pixels transistor for switching on and off that pixels LCD types: The LCD elements are switched on and off by different ways to display an image on the screen. There are two types of LCD screens. They are Passive-matrix (PMLCD), and Active-matrix (AMLCD). In Passive-matrix LCD, each LCD element is placed between two electrodes and arranged in rows and columns in X-Y matrix format. The bottom electrodes of each rows elements are connected together and the top electrodes of each column elements are connected together. The elements in row are controlled by a row-driver and the element in column by a column-driver. this is shown in figure(1) below. An image is created on the screen by activating a row-driver and activating a column-driver in sequence like scanning a line. ''(Mathivana, 2005, p.294) Figure(1)
- 3. 3 Active-matrix LCD use in transistor driver for each LCD element. The transistor are arranged in the matrix forma as shown in Figure(2) it allows the current from electric through individual elements to be switched on and off quickly with sufficient current to get good contrast. CRT display: The CRT display uses the same technology as the television. Figure(3) shows the basic components of the CRT. The vacuum glass tube has at the end of its neck a heated filament. The electrons emitted are attracted towards the face of the screen by the electric field created by the high tension (HT) voltage applied between the cathode and the anode. For a 12-inch monitor, this voltage is about 1200V. The beam of electrons passes through the focusing and deflection electrostatic plates or coils along the way. The screen is coated with a thin phosphor layer which emits light when impacted by an electron at that point. Figure(2) Figure(3)
- 4. 4 The different betweenCRT & LCD : CRT LCD This screen is broad and curved This screen is slim and flat Have a low quality and rough image Have a higher quality and softer image Have less visible area Have more visible area (for example a 15'' LCD have visible area of 17'' CRT at the same size) Consume more power Consume less power RCT monitors are cheaper and have many resolution LCD monitor are expensive and limited resolution Can change the appearance of pixel very quickly by switching on and off the electron beams Isn't fast enough to display the fast changing image
- 5. 5 Reference: Mathivanan, N. (2005) 'Microproccessors, PC Hardware and Interfacing'. New Delhi: Prentice-Hall of India private limited McLoughlin I. (2011) Computer Peripherals, Nanyang Technological University (Singapore)