tv transmitters & receiver

TV Transmitter&

Receiver

By: Shirke P.Y.

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Basic Monochrome Television Transmitter

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Basic Monochrome Television Receiver

TV Camera Heart of a TV camera is a Camera tube Camera tube – converts optical information into corresponding

electrical signal Amplitude proportional to brightness Optical image is focused by a lens assembly to a rectangular glass face-

plate Transparent conductive coating at the inner side of the glass face-plate On which is laid a thin layer of photoconductive material – having a

very high resistance when no light falls on it. Resistance decreases when the intensity increases Electron beam – used to pick up the picture information available on

the target plate in terms of varying resistance Beam is formed by an electron gun – deflected by a pair of deflection

coils kept mutually perpendicular on the glass plate - to achieve scanning of the entire target area

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Vidicon: Improvement of contrast

Improvement of signal to noise ratio

High image lag

Plumbicon Lower image lag (follow up of organ motions)

Higher quantum noise level

Solid state camera based on CCD Digital fluoroscopy spot films are limited in resolution, since they depend on

the TV camera .

Types of Camera Pick Up Tube

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Camera tube have a diameter of approximately 1 inch and a length of 6 inches.

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Simplified cross-sectional view of aVidicon TV camera tube

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Vidicon

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Working of Vidicon

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Vidicon Target & Equivalent ckt of Pixel

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Application of vidicon

Close circuit TV system Earlier type of vidicon were used only where

there was no fast movement , because of inherent lag

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Dark Current

Vidicon Lag

Beam Lag

Photoconductive Lag

Persistence Lag

Characteristic of Vidicon

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Lower image lag.It has fast response and produce high quality pictures at low

light level.It has small size and light weight and has low power operating

characteristics .It is similar to vidicon tube except small change in target plate

Plumbicon

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Plumbicon

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Plumbicon Target & Equivalent ckt of Pixel

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Solid state camera based on CCD

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Solid state camera based on CCD Equivalent ckt

•Charge-Coupled Devices (CCDs)

• 1980s CCD were developed and replaced TV tubes and miniaturized imaging devices.

• Light photons enter the silicon layer, ionization of the light separates the e-. A layer of microscopic electrodes beneath the silicon acts as a ground for the freed electrons. Movement of charges can be measured by a circuit.

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Each electrode is connected to a storage capacitor (TFT)

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Colour Science

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Colour Camera tube

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Colour Camera tube

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Picture Tube

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Construction of picture tube

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What is inside picture tube ?

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•Monochrome Picture Tube

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•DEFLECTION YOKEIt may be noted that a perpendicular displacement results because the magnetic field due to each coil reacts with the magnetic field of the electron beam to produce a force that deflects the electrons at right angles to both the beam axis and the deflection field.

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•Deflection Yoke

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PARTS AND WORK PRINCIPLE CRT COLOURED

1. Electron guns  

2. Electron beams

3. Focusing coils

4. Deflection coils

5. Anode

6. Mask

7. Phosphor layers

8. Close-up of the phosphor

Parts CRT colour

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•Delta-gun colour picture tube

(a) guns viewed from the base (b) electron beams, shadow mask and dot-triad phosphor screen (c) showing application of ‘Y’ and colour difference signals between the cathodes and control grids

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The screen has a number of phosphorus that will be fluorescent when exposed to fire electrons produced by electron gun.

This electron beam be turned by magnetic field that controlled by vertical spool and horizontal (spool yoke).

Magnified view of a shadow mask color CRT

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PRECISION-IN-LINE (P.I.L.) COLOUR PICTURE TUBE

(a) in-line guns (b) electron beams, aperture grille and striped three colour phosphor screen(c) mountings on neck and bowl of

the tube.

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Electron at shoot off and will hit dots phosphor will produce bright light and can be seen in the screen.

Tube also have mask color, to place phosphor's dots so correct electron beams.

There 3 circles phosphor that is red, blue and green. when described based on sequence the colour, so seen to like picture.

Magnified view of an aperture grille color CRT

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Basic Monochrome Television Transmitter

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Monochrome TV Transmitter

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Basic Monochrome Television Receiver

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Monochrome Television Receiver

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• 12190.pdf

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