Television System EE 3414 May 9, 2003 Group Members: Jun Wei Guo Shou Hang Shi Raul Gomez
Overview Basic Components of TV Camera Transmission of TV signals Basic Components of TV Reception of TV signals TV Standards Interlaced and Progressive Scan Different Types of TV Video devices The future of TV Impact on Society
Basic Components of TV Camera Lens Collects light from scene to form a sharp image Dichroic Mirrors Split the full-color image into 3 separate primary color images Image Sensors (3) Each has an electron gun that shoots a beam of electrons to scan the image A separate electronic signal for each of the three primary colors is created by the scanning process Encoder Combines the three primary color signals to produce a full-color picture on the TV screen. Microphone Picks up sounds and changes them into audio signals
Transmission of TV signals
Basic Components of TV Tuner Selects only the signal from the station the viewer wants to receive Decoder Changes video signal into primary color signals Picture Tube Transforms the primary color signals into patterns of light that duplicate the scene in front of the camera Images are created when an electron beam scans back and forth across the back side of a phosphor-coated screen Phosphor-coated screen Three phosphors arranged as dots or stripes to emit red, green and blue light Three colored phosphors blend together to produce the colors of the original scene
Reception of TV signals
TV Standards NTSC (National Television System Committee) Used in U.S., Japan, and several Asian countries Made up of 525 lines (262.5 odd-numbered and 262.5 evennumbered lines) Produces 525 lines per frame at 30 frames per second PAL (Phase alternating lines) SECAM (Sequence electronique couleur avec memoir) PAL is originated from Germany SECAM is originated from France Made up of 625 lines per frame at 25 frames per second
Interlaced and Progressive Scan Interlaced Scan Used by NTSC, PAL, and SECAM video Screen shows every odd line at one scan of the screen, with the even lines in a second scan Screen shows 1/2 of the frame every 1/60 of a second (30fps) Flicker or artifacts Progressive Scan Used by most Digital TV and some DVD players Displays the entire frame in a single scan Screen shows whole frame every 1/60 of a second (60fps) Eliminates flickers, smoother picture
Interlaced Vs. Progressive
Different Types of TV Direct-View TV Front-Projection TV Rear-Projection TV Flat-Panel TV
Direct-View TVs Conventional Curved Screen Built around a single large Cathode Ray tube (CRT) Flat Screen Curved screen reflects glare at all angles Flat screen reflects glare in only 1 direction, allows watching at different angles
Projection TVs Front-Projection TV Rear-Projection TV Usually built with 3 CRTs (one each for red, green, and blue) project the image onto a mirror, which reflects it onto the screen Front Projection TV: consists of a separate projector and a screen, allows watching at different angles in a dark room Rear Projection TV: Picture looks best when viewed straight on, dimmer if viewing from the side, allows watching in different lighting conditions
Flat-Panel TVs Plasma TV LCD TV Plasma: Emissive" display panel is self-lighting Each pixel is composed of three gasfilled cells or sub-pixels (one each for red, green and blue) Plasma (ionized gas) reacts with phosphors in each sub-pixel to produce light (red, green and blue) LCD: Transmissive" display light created by light bulb, shines light through the display Use red, green and blue color filters in place of phosphor dots
Video Devices TV (Back View) VCR (Back View) S-video jack DVD Player (Back View) 75 Ohm Coaxial Cable RCA A/V Cable S-Video Cable Component Video Cable
The Future of Television Digital Television System of transmitting and receiving TV signals in digital codes, and displaying those signals on a digital TV set, such as a HDTV All TV stations required to begin digital broadcasting by Dec.2006 All TV sets sold in the U.S. to be include digital tuners by 7/31/2007 HDTV (High Definition TV): Type of digital television that offers a greater number of scanning lines (1080i or 720p) Picture and Sound quality comparable to movie theater
Impact on Society TV PROS Good source for news, entertainment, and communications Good for economy by offering many job opportunities (actors, directors, writers technicians and engineers) TV CONS Takes away time from other activities (social gatherings, exercise) Televised violence encourages aggressive behavior Give viewers false impressions