Page 275 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

264 CHAPTER 10 Video
disabled) while repositioning between the right end of one line to the beginning of the next line, much like a typewriter needs to reposition from the end of one line to the beginning of the next before writing.
10.2.4 The display
Displays come in many shapes and sizes. The first functional television displays were the CRTs (Figure 10.21). A CRT consists of a vacuum tube containing an electron gun projected upon a fluo- rescent screen. Within the tube is an electromagnet for steering the beam so as to project a full dis- play based upon the target painting of the electron beam upon the screen.
CRTs have given way to more advanced and efficient digital display screens such as liquid crystal displays (LCD), plasma screens, and organic light-emitting diode (OLED) displays. However, the basics of display elements are unchanged. With LCD, plasma, and other modern fixed-pixel screens (versus the floating pixel of the CRT), either specific direct addressing or multi- plex addressing is used to provide information to each pixel on the display. With specific addres- sing, each pixel (x/y) address is given specific detail for picture generation while multiplexing addresses the rows and columns, further breaking down the information by line and row. The infor- mation can then be transmitted (versus individual pixel addressing), allowing for larger screens with higher pixel counts with the same bandwidth of a smaller screen with specific addressing.
As an example, some of the benefits of LCD over CRT are as follows:
• Smaller footprint for LCD (approximately 15% of CRT footprint)
• Lighter weight (typically 20% of CRT weight)
• Lower power consumption (typically 25% of CRT consumption)
• Flat screen incurring no geometrical errors
• Sharper pictures due to digital precision and uniform colors
• No electromagnetic emission!
• Much larger screens are possible
• Longer useful life than CRT
FIGURE 10.21
Basic schematic of a CRT.
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