IV YEAR ECE B SECTION TELEVISION AND VIDEO ENGINEERING BY G.SHANMUGAVADIVEL M.E., UNIT 1

UNIT-1 FUNDAMENTALS OF TELEVISION Television System and scanning Principles: Sound and picture transmission- scanning process, video signals, characteristics of human eye, brightness perception and Photometric qualities, Aspect ratio and Rectangular scanning, persistence of vision and flicker, vertical resolution, Kell factor, Horizontal Resolution and video bandwidth, Interlaced scanning. Camera tubes- camera lenses- auto focus systems, camera pick up devices, Image orthicon- vidicon - plumbicon- silicon diode array vidicon –CCDsolid state image scanners - Comparison of Camera tubes- camera tube deflection unit- video processing of camera signals- color television signals and systems 2

AIM & OBJECTIVE To Study the Fundamentals of Television and how the Signals are transmitted and received over a Long Distance and also working principle of Camera Tubes and their types. 3

Radio Spectrum 4

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190.5cm (75) Full HD 3D Smart Slim LED TV, USB Movie, HDMI, All Share, Built-in WiFi, 6D sound UA75ES9000R MRP Rs. 750,000/-* Rating is 5 out of 5 stars. 6

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APPLICATIONS Broadcast Television Videography Genome TV 11

DEFINITION OF TELEVISION Tele - Distance Vision - Seeing “Seeing from a long Distance” Broadcasting - To send in all direction 12

Cont., Picture (or) Scene - Optical in Nature Camera Tubes Picture Tubes 13

Television System and Scanning Principles Sound transmission Picture transmission 14

SOUND TRANSMISSION Mechanical Waves Frequency Range Microphone Radio Frequency Feed the RF Energy Amplifier Sound Reproducing Device 15

PICTURE TRANSMISSION Not Simple Space and Time of Brightness Retina Optical Nerves Sequential “Scanning” Technique 16

Scanning process movement of electron beam spot 525 horizontal scans in a frame Horizontal scanning frequency frames in one second (15625 lines ) Starts upper left of the picture area known as line1 Beam then proceeds horizontally to the upper right edge at a precise rate 17

Scanning a Frame The movement of electron beam spot from left to right Vertical (Slower) Horizontal (Faster) 18

TYPES OF SCANNING Horizontal Scanning –The movement of electron beam spot from left to right. Vertical Scanning –The number of views also called fields transmitted per second. 19

Cont., The left edge to a point 2 lines below the previous scan 52.5 microseconds to scan from left to right end 11 microseconds to return to the left again to begin scanning the next line 20

CAMERA PICK-UP DEVICES Lens System Photosensitive target Faceplate of Camera pickup tube Accurate and Well Defined Image 21

PHOTOELECTRIC CONVERSION variations in the intensity of Light - Variations in Electric Signals Photoemissive Surfaces –Iconoscope Photoconductive Coating (or) Layer –Vidicon and Plumbicon 22

VIDEO SIGNAL Picture Signal (25Hz -5MHz) Time Varying Electrical Signal Voltage Special Distribution of Brightness Frequency –Scanning Speed –Variations in the brightness Fast Scanning Rate 23

Characteristics of human eye Visual acuity or Resolution– Ability to Resolve Finer Details in a picture Persistence of Vision Brightness and Colour Sensation 24

Cont., 25

Cont., Retina – Rod and Cones –Primary Brightness Level –Colour Perception 6,500,000 Cones 100,000,000 Rods 800,000 Optic Nerve Fibres Sharpest vision - Fovea 26

Transmitter 27

Receiver 28

Vertical Resolution Proportional to # of vertical scan lines Theoretic maximum –Half of visible scan lines –Black lines alternate with white max. line pairs = video lines / 2 29

Vertical Resolution Actual limit lower than theoretical~ 10% of lines occur during retrace Returning beam from bottom to top of image Scan lines may not perfectly synchronize to high resolution object –Typically 525 lines yield ~185 line pairs Vertical Retrace 30

Bandwidth Bandwidth = [Horizontal Resolution] X [Video Lines] X [Frame Rate] cycles scan line lines frame frames sec cycles sec =X X 31

Horizontal Resolution Bandwidth [Horizontal Resolution] = [Video Lines] X [Frame Rate] Bandwidth = [Horizontal Resolution] X [Video Lines] X [Frame Rate] 32

TV Interlacing Frame scanned in two passes, first the odd lines then the even –One frame takes 1/30th second –avoids flicker Each pass called a field –takes 1/60th second 33

FRAME: An image created by 2 successive fields 2 fields = one frame Field 1 scans all the odd numbered lines Field 2 scans all the even numbered lines 1st Field (Odd lines)2nd Field (Even lines) = += One Frame 1/60th sec. 1/30th sec. 1/60th sec. + 34

Interlaced Frame Sweeps the image as two fields that are interlaced to form a given frame Field one Field two 35

Cont., Aspect Ratio Ratio of width to Height of the picture image Retrace –Horizontal retrace beam returned to left side of screen –Vertical retrace beam returned to the top of screen –Turns off video during retrace Vertical Retrace Horizontal Retrace 36

Example 37

Converts light to coded electrical signal Camera Tube Vidicon cheapest / compact / laggy Plumbicon enhanced vidicon / less lag CCD Semiconductor not a tube Camera Tubes TV Camera Light electrical signal 38

Vidicon TV Pick-up Tube 39

Image Orthicon 40

Plumbicon 41

Charge Coupled Device (CCD) Semiconductor device –not vacuum tube Stores charge in small discrete wells Transfers charge to readout device one line at a time No readout beam, focusing or deflection coils Shorter than vidicons Resolution limited by number of scan lines (element array) 42

Colour Fundamentals  Primary colors  Secondary colors Red, Green, and Blue are primary colors Magenta, Yellow, and Cyan are secondary colors White is the combination of all colors Black is the absence of light 43

Colour Fundamentals Additive ColoursSubtractive Colours 44

Basic Colour Properties Luminance or brightness: Amount of light received by eye regardless of colour Hue(color itself): Predominant spectral purity of colour light Saturation: intensity of the color Chrominance: combination of hue and saturation 45

Chromaticity Diagram 46

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Colour circle 48

CAMERA TUBES  Vidicon  Plumbicon  Saticon  Newvicon  Chalnicon  Silicon Diode Array

VIDICON  Small Size  Principle  Target Plate – Intensity of Light  Construction 1.Photo Conductive Target Plate 2.Scanning Section 3.Electron Gun Section 50

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PHOTO CONDUCTIVE TARGET PLATE  Antimony or Selenium Compounds  Face Plate – Transparent, Conductive Film  Signal Electrode  DC Supply 52

SCANNING SECTION  Electron Beam  Deflection Coil  Alignment Coil  Deaccelerating Field (Grid No 4) Secondary Emission 53

ELECTRON GUN SECTION  Heater  Cathode  Control Grid  Focusing Coil  Accelerating Anodes 54

Principles  Photo Conduction  cm – 20MOhm  2Mohm  Pattern of Positive Potential – Photo Layer  Charge Image  High Illumination - +39V  Low Illumination - +35V on the Beam Side  Leaky Capacitor  Capacitor with Light dependent Resistor  +40v  Electrons – Unterminate end of Capacitor  Load Resistance 55

Cont.,  Advantages  Resolution is High  Long Life and Small in Size  Vary Target Voltage – Different Levels of Sensitivity  Gamma Cancellation Circuit is not necessary  Disadvantages  High Dark Current  Poor Sensitivity  High Image lag 56

PLUMPICON ► Outer Surface – SnO 2 (Tin Oxide) ► Inner Surface – Pure Pb0 (Lead Monoxide) ► Outer Surface – Dopped Pb0 ► 15 *

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WORKING PRINCIPLE ► Capacitor – Reverse Bias Light Dependent Resistor ► +40V Supply ► Reverse Bias – High Resistance ► Current & Voltage - R L 59

Cont., ► ADVANTAGES  Reduced Lag  Higher Sensitivity  Medium Size & Compact ► DISADVANTAGES  High Cost  Spectral Response is Poor for Red Colour Region 60

SILICON DIODE ARRAY Vidicon N- type Silicon Wafers Trade name SiO 2 - Insulating Layer Etching & Masking Process cm & 1.5 cm – 540*540 photo diodes 61

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ADVANTAGE –Low Dark Current –Good Resolution –High Sensitivity –Long Life & Lightly Overloaded DISADVANTAGE –Speed of response is not good –Dark Current is temperature Dependent 63

SOLID STATE IMAGE SCANNERS 64

CCD IMAGE SENSORS 65

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PMTFilmCCDCMOS Dynamic Range >1000<100>10,000>5,000 Detection Speed fastestslow fast Quantum Efficiency 5-20% 25-95%15-35% Multi- channel noyes Real-timeyesnoyes Spectral Sensitivity nm nm Dark Signalgoodpoorbest Read Noisegood best 68

CCD Image Plate ADVANTAGES –No Need of Electron Gun &n Electron Beam –No need For High Voltage –No need for Vaccum Envelope 69

Comparison of camera tubes 70

S.NoCharacteristicsImage OrthiconVidiconPlumbicon 1Light TransferEmission BasedPhoto Conductive 2SensitivityVery HighHigh 3S/N ratio80 db50 db 4SpeedNo Halo lagHigh halo lagLow Halo lag 5Spectral responseEquivalent to eyeGoodLess in Red 6OperationBit toughEasy 7CostHighLowBit High 8SizeBigSmallMedium 71

Pick up tube deflection unit  Focusing Coil  Axial Magnetic Field  Divergent Electrons  Focus Nodes or Lobes  Deflection Coil  Pair Of Coils  Vertical Field & Horizontal Field  1/10 th of the Focusing Coil  Alignment Coil  Outside the Limiting Aperture  Magnetic Field at right angles 72

Deflection coil unit data 73

VIDEO PROCESSING OF CAMERA SIGNALS Video Signal – Target Plate Pre – Amplifier –300 nA –Head Amplifier –Cable Equalizer Co-Axial Cable Loss Of High Frequency – Passive Equalizer Network Length of Cable 74

Aperature Correction & Image Enhancement Aperature Correction –Restore the Depth Of Modulation –400 lines- 40 lines Resolution Image Enhancement –A Delay Line Transversal Filter –High Frequency boost Without Phase shift 75

GAMMA CORRECTION Gamma =1 Gamma < 1 – Low Upwards Gamma > 1 – Low Downwards 76

Clampling circuits –DC Component –AC Coupled Amplifier –RESTORER White Clip –Normal Amplitude 1V (0.7 – 0.3) 0.7 V – 100 IRE Units 0.3 V – 40 IRE Units 77

White clip Black Clipper – Blanking Adder Sync Adder –Sync Mixer or Adder Circuit Shading Correctors Polarity Reversal 78

Colour television signals & systems 79

Colour fundamentals  Primary colors  Red, Green, and Blue  Secondary colors  Magenta, Yellow, and Cyan White is the combination of all colors Black is the absence of light 80

Cont., Additive Colours Subtractive Colours 81

Basic Colour Properties Luminance or brightness: Amount of light received by eye regardless of colour Hue(color itself): Predominant spectral purity of colour light Saturation: intensity of the color Chrominance: combination of hue and saturation 82

Chromaticity Diagram 83

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Colour circle 86

Possible 2 marks 1.Mention the major function of the camera tube? 2.What do you refer by persistence of eye? 3.Define visual acuity? 4.Define aspect ratio? 5.Define luminous intensity? 6.what do you mean by resolving power or resolution? 7.Mention some important characteristics of human eye? 8.Define luminance? 9.What do you understand by illuminance 10.Define luminous flux? 87

11.What are rods and cones? 12.Give the relationship between eye parameters? 13.How will you solve the flickering problem? 14.What do you mean by interlaced scanning? 15.Why is scanning necessary in television system? 16.What do you understand by flicker? 17.Define vertical resolution? 18.What is horizontal resolution? 19.State grassman’s law. 88

21.Explain the significance of generating colour difference signals 22.Define peak-white level? 23.What is the main function of the blanking pulses? 24.What do you understand by Hue? 25.Define Brightness. 26.What do you mean by saturation? 27.List any three requirements to be satisfied for compatibility in television systems. 28.What are per the post equalizing pulses? 29.What is additive mixing? 30.What is meant by video signal? 89

31.What is meant by Luminosity 32.Define Rectangular Scanning 33.What is Focal Length & Power? 34.Give the Formula for Viewing angle Of Lens? 35.Define Lens Speed & Depth of Field? 36.What is Clamping Circuits? 37.What is Gamma Correction? 38.Define Polarity Reversal 90