camera tubes

8/9/2019 Camera Tubes

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Pick-up tubes

An image pick-up tube with aphotoconductive layer which acts as thephotosensitive surface.

Converts its light input to correspondingelectrical variations for the video signal.

“The camera tube is to video as themicrophone is to audio.”

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1. PHOTOEMISSION

Liberation of electronsfrom a material under theinfluence of illumination

2. PHOTOCONDUCTION

Changes of conductivity of asurface due to illumination

METHODS OF PRODUCING AN IMAGE WITHINTHE TUBE

3. PHOTOVOLTAIC ACTION

Generation of voltage due tochemical or physical changes

induced by illumination

http://www.amcoordination.com/index.html



1. LIGHT TRANSFER

CAPABILITY

Ratio of brightness variationsin the reproduced image tothe brightness variations in

the original scene

2. SPECTRAL RESPONSE

Same as the eye; colors are

rendered in their propertones

CHARACTERISTICS OF CAMERA TUBES

3. SENSITIVITY

Unit: Lumen; output photosignalper incident illumination




The light image is transformed into an electronic image,which can then be read from the back of the target by a

beam of electrons.

HOW CAMERA TUBES WORK

In a camera tube pickup device, the front of the tubecontains a layer of photosensitive material called a

target .The lens of a camerafocuses light from a

scene onto the front ofthe camera tube, and

this light causeschanges in the target

material.




This varying voltage is the electronic television signal.

HOW CAMERA TUBES WORK

The beam of electrons is produced by an electron gun atthe back of the camera tube.

The beam is controlled by a system ofelectromagnets that make the beamsystematically scan the target material.

Whenever the electron beam hits the bright partsof the electronic image on the target material, thetube emits a high voltage, and when the beam hits

a dark part of the image, the tube emits a lowvoltage.



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Nipkow Disk

Image Dissector

Iconoscope

Image Orthicon

Flying Spot Scanne r



Vidicon

Plumbicon

Saticon

Silicon Vidicon

Chalnicon

Newvicon



Also known as Scanning Disk

Paul Julius Gottlieb Nipkow (22August 1860 – 24 August 1940)

In 1884, Nipkow Disk wasdesigned.

Fundamental componentin mechanical television through the

1920 s.



A mechanically spinning disk of anysuitable material (metal, plastic,cardboard, etc.)



With a series of equally

distanced circular holes ofequal diameter.

The holes may also be squarefor greater precision.

Holes are positioned to form asingle-turn spiral (external radialpoint - center of the disk)



Image sensor can be as simple as asingle photocell or photodiode.

Maximum number of scan lines is muchmore limited.

Images are typically very small.

Devices using them were also noisy, heavyand picture quality was very low, with a lotof flickering.



also called a dissector tube ,

is video camera tube inwhich photocathode emissions create an"electron image " which is then scannedto produce an electrical signalrepresenting the visual image .

It is relatively insensitive , but it isuseful where a scene is brilliantlyilluminated.

The image dissector is useful onlywhere scene illumination exceeds200 foot-lamberts.



Max Dieckmann

Rudolf Hell



American television pioneer.

Electron Multipliers ( January 7,

1927) - a device that increased thenumber of electrons.

Multipactor ( March 3, 1930) -

could amplify a signal to the 60thpower or better .

August 25, 1934 - the world's firstpublic demonstration of a complete,all-electronic television system.



Caesium oxide

Electrostatic deflectingplates

Anode

Electron multiplier

Visual Image



Diamond Power Specialty Co. of

Lancaster, Ohio.

Monitor boilers in power plants.

The camera has its own count-down sync generator, with bothvideo and RF output.

Water gauge



A modern version of the electric eye.no " charge storage " characteristic.

It is a vacuum device with a photo-sensitive surface.

The resolution of it is high , fullyadequate for television .

Highly sensitive image storage device



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RCAmanufactured several types ofIconoscopes (types 1846, 1847, 1848, 1849,1850, 1850A, and 5527 ).

The 1846 and 1848 (introduced in 1940)were about 4 1/2 inches diameter, had an octal(8-pin) base with a metal shell.

The 1849 and 1850 (both introduced in1939) for film-to-video applications.

1850A (introduced in 1945) were about 6 1/2inches in diameter.

The 5527 (introduced in 1947) had a 2 inchdiameter tubular bulb



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Sanford Essig (1931) - The first

practical iconoscope was constructed.

Tedham and McGee (1932) - underthe supervision of Isaac Shoenberg

Emitron - a 405-linebroadcasting service employing theemitron began at studiosin Alexandra Palace.



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Lubszynski , Rodda, and MacGee(1934) - the british team formed byengineers developed the super-emitron(or super-iconoscope)

super-emitron- this new deviceis between ten and fifteen timesmore sensible than the originalemitron and iconoscope.



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The optical image is focused onto the target

The target is scanned

Electron beam – two sets of deflection coils

Signal plate- very thin sheet of micaMosaic- silver elements

The bright regions of the image

Electron beam repeatedly scans

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Application:

To television it replacesmechanical scanning equipmentand several stages of

amplification.The whole system is entirely

electrical.

Act as an electric eye



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A television camera tube in whichelectrons, emitted from a photo

emissive surface in proportion to theintensity of the incident light, arefocused onto the target causingsecondary emission of electrons.

Developed by the RCA Corporation inthe early 1940s

It changes light from the scene being

televised into electronic si gnals.



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An image orthicon consists of three parts:

photocathode

electron gun

multistage electron multiplier



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RCA IMAGE ORTHICON



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First usable Image Orthicon producedby RCA's Rose, Law and Weimer in 1945

RCA 3" Image Orthicon 5820



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Flying spot scanner

A form of television pickupdevice, used to record imagesfrom film transparencies, eitherstill or motion-picture.

implemented by DuMontLaboratories in 1956.

1920s.



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Cathode Ray TubePhoto beamDichronic Mirrors

Red- Green- Blue sensitive photomultipliers

P

ARTS



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is a video camera tubedesign in which the targetmaterial is a photoconductor.

developed in the 1950s atRCA by P. K. Weimer, S. V.Forgue and R. R. Goodrich



is a storage-type camera tube in which a charge-densitypattern is formed by the imaged scene radiation on aphotoconductive surface which is then scanned by a beam

of low-velocity electrons.

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The fluctuating voltage coupled out to a videoamplifier can be used to reproduce the scene beingimaged.

The electrical charge produced by an image willremain in the face plate until it is scanned or untilthe charge dissipates.

Pyroelectric photocathodes can be used to

produce a vidicon sensitive over a broad portion ofthe infrared spectrum.



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A registered trademark of Philips for its Lead Oxide(PbO).

Used frequently in broadcast camera applicationsthese tubes have low output, but a high signal-to-noise ratio.

They had excellent resolution compared to Image

Orthicons, but softer.

CBS Labs invented the first outboard edgeenhancement circuits to sharpen the edges ofPlumbicon generated images.

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Compared to Saticons, Plumbiconshad much higher resistance to burn in,and comet and trailing artifacts from

bright lights in the shot. Saticons though,usually had slightly higher resolution.

Plumbicon tubes remain a stapleimaging device in the medical field.

Narragansett Imaging is the onlycompany now making Plumbicons, and itdoes so from the factories Philips built

for that purpose in Rhode Island, USA.



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Saticon was developed byHitachi(japan) in 1973 as acamera tube suitable forbroadcast. It consists ofselenium, arsenic, andtellurium and hence the nameSaticon.



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Constrution of Saticon

Construction of face plate, signal plate (tin oxide),electron gun, focusing and deflecting devices is thesame as in vidicon

Saticon’s target plate consists mainly of seleniumwhich is the first chemical element that was tried in TVcamera tubes



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The transparent tin-oxide layer allows light tofall on the target but being an electricalconductor, it connects the current path to theload resistor through the conducting ring.



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Silicon vidicon - is lesssusceptible to damage byexcessive brightness of thescene. It has high sensitivity

and lower lag. It sensitivitycovers infrared region.



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The target plate consists of a very thin n-type silicon wafer. A thinsilicon dioxide layer is applied over the wafer.

Then by photomasking and etching processes p-type material (boron)is diffused into the wafer at various openings, resulting in an array ofsilicon photodiodes.

A fine layer of gold is deposited for connection on the p-type layer.

This tube is useful in high light environment which produces imagelag in an ordinary vidicon.

Total number of diodes are 540x540 (about 300k). The diodes are

reversed biased by applying +10v to the signal plate.

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trademark of Toshiba Electric Co. Ltd.

multilayer arrangement consisting ofTin oxide, Cadnium Selenide and ArsenicTrisulfide.

features a high sensitivity over therange of visual spectrum

typically more laggy than a Newviconbut provide higher resolution.



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trademark of Matsushita Electric.

made of Amorphous Zinc Selenide.

originally developed by Philips as an

improved form of Vidicon.

high light sensitivity



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a registered trademark of theHeimann division of EG&G.

This is a highly sensitive camera tubewith low dark current and excellent signaluniformity and resolution.

Its surface consists of CadmiumSelenide (CdSe)



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Resistron is a Vidicon type camera tube.

It is suited for routine diagnostic procedures, since itprovides high contrast with excellent resolution

High Sensitivity, Good Resolution.Antimony Trisulfide cathodeEspecially useful in high radiation environmentsElectrostatic focusing, magnetic deflectionWorks in standard vidicon camerasTube diameter: 25.8 mm length: 158 mm

Standard 8- pin socket.



The Primicon is a high quality medicalgrade tube developed by Thomson.

Primicon tubes have high resolution andgood lag characteristics .

camera tubes

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