PPT INCLUDES COLOR SIGNAL TRANSMISSION AND RECEPTION DETAILS ,CAMERA ,COLOR PICTURE TUBE AND ITS TYPES ,COLOR TV CAMERA

1. CHAPTER 2
COLOR SIGNAL
TRANSMISSION AND
RECEPTION
SUBJECT:VIDEO ENGINEERING
By-Miss S U. Revankar
Assistant Professor,
Dept. of E & TCE,
SITCOE,Yadrav,Ichalkaranji

2. COLOR T.V CAMERA

4.  It essentially consists of three camera tubes in
which each tube receives selectively filtered
primary colors.
 Each camera tube develops a signal voltage
proportional to the respective color intensity
received by it.
 Light from the scene is processed by the objective
lens system. The image formed by the lens is split
into three images by means of glass prisms.
 These prisms are designed as diachroic mirrors.

5.  A diachroic mirror passes one wavelength and
rejects other wavelengths (colors of light).
 Thus red, green, and blue color images are formed.
 The rays from each of the light splitters also pass
through color filters called trimming filters.
 These filters provide highly precise primary color
images which are converted into video signals by
image-orthicon or vidicon camera tubes.

6.  Thus the three color signals are generated.
 These are called Red (R), Green (G) and Blue (B)
signals
 Simultaneous scanning of the three camera tubes
is accomplished by a master deflection oscillator
and sync generator which drives all the three tubes.


7.  The three video signals produced by the camera
represent three primaries of the color diagram.
 By selective use of these signals, all colors in the
visible spectrum can be reproduced on the screen
of a special (color) picture tube.

8. COLOR PICTURE TUBE:
 Delta Gun Color Picture Tube
 Gun-in-Line or Precision-in-line Color Picture Tube
 Single gun or Trinitron Color Picture Tube

9. DELTA GUN COLOR PICTURE TUBE

10.  Radio Corporation of America RCA
 3 separate guns for 3 colours.
 Guns equally spaced at 120 ,tilted towards axis.
 Screen coated with 3 different phosphors for R, G,
B.
 Triad contains 1 dot of each colour.
 3,33,000 triads.
 Eye integrates 3 colour information to give a
sensation of combined hue.
 Shadow mask.
 One hole per triad.
 All stray electrons (80%) get collected by mask.

11. DISADVANTAGE OF DELTA GUN TUBE:
 Convergence is difficult.
 Very elaborate arrangements to overcome it.
 Focus not sharp over entire screen.
 Mask passes only 20% of electrons.

12. PRECISION IN LINE COLOR PICTURE TUBE

13.  3 Guns in line simplifies convergence adjustment.
 Colour phosphors in form of vertical stripes.
 Distance same as in Delta gun.
 More efficient.
 Larger % of electrons pass through mask.
 Fewer convergence adjustments. Most widely
used.

14. TRINITRON PICTURE TUBE

15.  By Sony Corporation, Japan
 Single gun having three cathodes.
 Simplified construction as only one electron
assembly.
 Three phosphor triads arranged in vertical strips.
 Each strip is few thousandth of a cm.
 A metal aperture grill has one slot each triad.
 Grill has greater electron transparency.
 Three beams appear to emerge from same point.

16. PURITY AND COVERGENCE
 PURITY:

17.  Each beam must fall at center of corresponding dot.
 Irrespective of position of triad on screen.
 Circular magnets called purity magnets on neck of
yoke does the alignment.
 If all tabs moved together, they change direction of
field.
 If tabs are separated, magnetic field reduces.
 2, 4, 6 pole magnets to achieve collective or
individual beam deflection.
 Error may also occur if yoke is not positioned
properly.

18.  CONVERGENCE :

19.  Technique that all electrons hit the same part of the
screen to produce 3 coincidental rasters.
 Convergence occurs due to Errors–
 Non-coincidental convergence plane.
 Non-uniformity of deflection field.
 Flat surface of picture tube screen.

20.  Proper convergence is achieved by positional
adjustment of the individual beams. It falls into two
parts referred to as (i) static and (ii) dynamic
convergence
 Static and dynamic convergence.
 Static convergence by permanent magnet.
 Once correctly set, brings the beam into
convergence in the central area of the screen
 Dynamic convergence converges beam over rest of
the screen.

21. DEGAUSSING
 Due to Earth magnetic field and other nearby
magnetic fields, mask and mounting frame may get
magnetized.
 Will cause purity error causing in colour patches.
 Can be repaired by influencing the screen by an
alternating magnetic field which gradually reduces
to zero.

22. AUTOMATIC DEGAUSSING

23.  At switch ON, thermistor is cold and has high
resistance.
 More AC passes through coil and varistor, causing
alternating magnetic field.
 Thermistor gradually heats up, reducing its
resistance.
 More current flows through thermistor. Lesser
current through coil and varistor. Heats thermistor
further •.

24.  This continues till current through thermistor
becomes maximum.
 Current through varistor and coil gradually reduces
to zero.
 Components chosen to give initial surge of
4ampere to D.Coil.
 Final current less than 25mA in less than a second

25. COLOR MIXING THEORY
 Additive color mixing theory
 Subtractive color mixing theory

26. ADDITIVE COLOR MIXING THEORY

27.  Additive color mixing theory deals with mixing
of light.
 The primary colors red, blue and green can be
paired to form white (red, blue and green), magenta
(red and blue), yellow (red and green) and cyan
(green and blue).

28. SUBTRACTIVE COLOR MIXING THEORY

29.  Subtractive color mixing theory deals with pigments
or dyes with three primary colors magenta, yellow
and cyan - which can be mixed together to form
colors in the visible light spectrum.
 By mixing the primaries the subtractive secondaries
black (magenta, yellow and cyan), red (magenta
and yellow), blue (magenta and cyan) and green
(cyan and yellow) can be made

30. CHARACTERISTICS OF COLOR
 There are three qualities which are used to describe any one color.
 These are hue, saturation, and brightness.
 HUE:
Hueisaqualitywhichisusedtoidentifyanycolorunderconsideration,
suchasred,blue,oryellow.Ahueisapurecolorthathasnotbeen shadedwithblack
ortintedwithwhite.
 SHADE: A hue mixed with black
 TINT: A hue mixed with white
 TONE: A hue mixed with both black and white

31.  SATURATION: Saturation, also called "chroma," is a
measure of the purity of a color or how sharp or dull the
color appears.
 BRIGHTNESS: Brightness, also called "luminance" or
"value," is the shade (darkness) or tint (lightness) of a
color. Areas of an evenly colored object in direct light
have higher brightness than areas in shadow.

32. CHROMATICITY DIAGRAM
 What is chromaticity
the quality of a color as determined by its dominant
wavelength and its purity.
 Chromaticity diagram is a convenient space
coordinate representation of all the spectral colors
and their mixtures.

35. NTSC COLOR TV SYSTEM
 NTSC (National Television Standards Committee) is the
oldest existing standard, developed in the USA and first
used in 1954. It's parameters are as follows:
Lines: 625
Frame rate: 29.97 Hz
Picture resolutions: 720 x 480; 704 x 480; 352 x 480;
352 x 240
The Countries that support NTSC video are as follows:
Antilles, Netherlands, Bahamas, Barbados, Belize,
Bermuda, Bolivia, Burma, Canada, Chile, Columbia,
Costa Rica, Cuba, Dominican Republic, El Salvador,
Ecuador, Grenada, Guatemala, Honduras, Jamaica,
Japan, Mexico, Panama, Peru, Philippines, Puerto
Rico, South Korea, Surinam, Taiwan, Tobago,
Trinidad, United States of America, Venezuela.

36. NTSC TRANSMITTER DIAGRAM

37. NTSC RECEIVER

38. PAL COLOR TV SYSTEM
 PAL (Phase Alternating Line) was developed in 1967 by the United
Kingdom & Germany. PAL standard utilizes a wider channel bandwidth
than NTSC which allows for better picture quality. It's Parameters are as
follows:
Lines: 525
Frame rate: 25 Hz
Picture resolution: 720 x 576; 704 x 576; 352 x 576; 352 x 288
The countries that support PAL are as follows:
Algeria, Andorra, Angola, Argentina, Australia, Austria, Bahrain,
Bangladesh, Belgium, Botswana, Brazil, Brunei, Cameroon, China,
Denmark, Ethiopia, Fiji, Finland, Germany, Ghana, Gibraltar, Hong Kong,
Iceland, India, Indonesia, Ireland, Israel, Italy, Jordan, Kenya, Kuwait,
Lesotho, Liberia, Luxemburg, Malawi, Malaysia, Maldives, Malta,
Mozambique, Namibia, Netherlands, New Zealand, Nigeria, Norway,
Oman, Pakistan, Papua New Guinea, Paraguay, Portugal, Qatar,
Rumania, Seychelles, Sierra Leone, Singapore, Somalia, South Africa,
Spain, Sri Lanka, Sudan, Swaziland, Sweden, Switzerland, Syria,
Tanzania, Thailand, Turkey, Uganda, United Arab Emirates, United
Kingdom, Uruguay, Yemen, Yugoslavia, Zambia, Zimbabwe

39. PAL ENCODER

40. PAL DECODER

41. SECAM COLOUR TV SYSTEM
 SECAM (Squentiel couleurmmoire) was developed in France
in 1967. SECAM uses the same bandwidth and resolution
(720x576) as PAL but transmits the color information
sequentially. Take note that only a handful of products support
SECAM.
 The countries that support SECAM are as follows:
Afghanistan, Benin, Burkina Faso, Bulgaria, Burundi, Central
African Republic, Chad, Congo, Czechoslovakia, Djibouti,
Egypt, France, French Guiana, Gabon, Greece, Guadalupe,
Guinea, Gyprus, Haiti, Hungary, Iran, Iraq, Ivory Coast,
Lebanon, Libya, Madagascar, Mali, Martinique, Mauritius,
Mauritania, Monaco, Morocco, Niger, North Korea, Poland,
Russia, Rwanda, Saudi Arabia, Senegal, Syria , Togo, Tunisia,
Vietnam, Western Samoa, Zaire.

42. SECAM ENCODER

43. SECAM DECODER

44. DIFFERENCE BETWEEN NTSC PAL AND SECAM

45. COMPATIBILITY CONSIDERATION

47. ENERGY BUNDLE

48. FREQUENCY INTERLEAVING PROCESS
INTERLEAVING OF COLOR SIGNAL

49. INTERLEAVING OF ENERGY BUNDLE

50.  Video signal band bears a definite relation with
scanning frequencies.
 Energy content of video signal is contained in
individual energy “bundles”.
 Bundles occur at harmonics of line
frequency.15625Hz
 Components of each bundle separated by multiple
of field frequency. 50, 100, 150…

51. THANK YOU