CA1118831A - Device comprising a television camera tube and television camera for such a device - Google Patents
Device comprising a television camera tube and television camera for such a deviceInfo
- Publication number
- CA1118831A CA1118831A CA000321220A CA321220A CA1118831A CA 1118831 A CA1118831 A CA 1118831A CA 000321220 A CA000321220 A CA 000321220A CA 321220 A CA321220 A CA 321220A CA 1118831 A CA1118831 A CA 1118831A
- Authority
- CA
- Canada
- Prior art keywords
- anode
- aperture
- electrode
- cathode
- diameter
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
- H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
- H01J29/48—Electron guns
- H01J29/484—Eliminating deleterious effects due to thermal effects, electrical or magnetic fields; Preventing unwanted emission
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J31/00—Cathode ray tubes; Electron beam tubes
- H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
- H01J31/26—Image pick-up tubes having an input of visible light and electric output
- H01J31/28—Image pick-up tubes having an input of visible light and electric output with electron ray scanning the image screen
- H01J31/34—Image pick-up tubes having an input of visible light and electric output with electron ray scanning the image screen having regulation of screen potential at cathode potential, e.g. orthicon
- H01J31/38—Tubes with photoconductive screen, e.g. vidicon
Landscapes
- Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
- Electrodes For Cathode-Ray Tubes (AREA)
Abstract
ABSTRACT
A television camera tube having an electron gun to generate an electron beam, which electron gun comprises, centred along an axis. successively a cathode, a first electrode having an aperture, a second electrode having an aperture, and a focus-ing lens to focus the electron beam on a photosensitive layer pro-vided on a signal plate. A potential distribution can be formed on the photosensitive layer by projecting an optical image on it and the signal plate provides electric signals corresponding to the optical image by scanning the photosensitive layer with an electron beam. The diameter of the aperture in the first electrode, which forms a first anode, is at least twice as large as the dia-meter of the aperture in the second electrode, which forms a second anode. The aperture in the first anode is so small that d lens field is formed between the first and second anodes which has nearly no influence on the cathode emission. A positive vol-tage of a few tens of volts is applied to the first anode and a positive voltage which is at least ten times higher and which is at least 100 volts is applied to the second anode.
A television camera tube having an electron gun to generate an electron beam, which electron gun comprises, centred along an axis. successively a cathode, a first electrode having an aperture, a second electrode having an aperture, and a focus-ing lens to focus the electron beam on a photosensitive layer pro-vided on a signal plate. A potential distribution can be formed on the photosensitive layer by projecting an optical image on it and the signal plate provides electric signals corresponding to the optical image by scanning the photosensitive layer with an electron beam. The diameter of the aperture in the first electrode, which forms a first anode, is at least twice as large as the dia-meter of the aperture in the second electrode, which forms a second anode. The aperture in the first anode is so small that d lens field is formed between the first and second anodes which has nearly no influence on the cathode emission. A positive vol-tage of a few tens of volts is applied to the first anode and a positive voltage which is at least ten times higher and which is at least 100 volts is applied to the second anode.
Description
~ 383~
4-1-1979- i PHA 20'791 ~'Dcvice comprising a tele~ision camera tube and television camera tube`~or such a device".
~.
:~ ~ The invention relates to a device com- -prising a television camera tube having an electron gun to generata an electron beam, which electron ~In - comprises, centred along an axis, successively a ~ S cathode, a first electrode having an aperture~ a . seoond electrode havillg an aperture, and a focusing lens to focus the electron beam on a photo~sensitive layer provided on a signal plate, a potential distri-bution being ~ormed on said photosensiti.ve layer by projecting an optical image on it, ~aid signal plate providing electric signals corresponding -to the sai.d optical image by scanning the pnotosensitive .layer by means of the electron beam.
; The invention also relates to a television camera tube ~or such a device~
The said potential distribution, sonletimes termed potential ima~r3, is formed in t~at the photosen-sitive layer may be considered as being composed o~ a ; large nwnb,3r o~ picture elernellts. Each picture ,element . rnay ~e corl~idered as a capa"itor to which:-ls connected in parallel a current source whose currerlt str-ength:i.s : substantiall.y E)roportional to t]l~i3 li,~ht in.tensity OD.
the picture element. So th.e ohar~e o~ eacll capacl,~or decreases linearly with -kime at, con,;tan~ light in,,ensi-ty.
,: ., ~ . ... , :. ,".. , , , , ,, .. : . . ..
, :
;~ ,, ., ., , , .................................. ,~æ
.
4-1-'i979 ~ P~ 20791 , ' As a result of the scanni~g t'he electron beam pas~ses each picture element periodically and then charges th~s capacitor, that is to sa~ that the voltage across each picture element is brought periodically at approximat-S ely 45 Volts. The quantity oP charge n0cessary to per-iodically charge a capacitor is proportional to tha light intensity on the'relevant picture elementc The associated current flows via the signal plate which is common to all the picture elements through a si~nal resistor so that across the si~nal resistor a~oltage is formed which as a function of time represents the li~ht intensitr of the optical ima~e as a function of' the place. A television camera tube having the descri-bed effect is generally termed a vidicon.
One of the aspects of a device o~ tha above-described type îs the response rate, that is to say the velocity at which the device reacts to variat-~,~ ions of thelight~intensit~. The response rate i8 in-fluenced inter alia by the ~act that the charge which the electron beam supplies to the picture element in ; the short period o~ time in which it passes a givell picture element depends on~the ~elocity distribution of the elactrons in the electron beam. This influence of the response rate is termed beam current inertia.
The velocity distribution of the electrons leaving the cathode depends on the temperature o~ the catho~e and is referred to as Maxwell distribution. As a re-sult of e~ects to be m~ntioned hereina~ter, however,~
an excesso~ ~ast electrons ma~ arlse, that is to say, ' there are moYe~ast elect;rons in the bearn than corres-pon-lstO the Maxwell distribution.'This excess of fast electrQns causes a detrimental in~luence o~ the beam current inertia and hence of t;he response rate.
An e~fect by ~rhich rast electrons can 3S be formed is X~ray radiation as a result o~ electlons of the electron beam whic'h impinge on the anode. This ; X-ray radiation may release fast electrons from the cathode.
r ~; ' t~' ~-1-1979 3 PHA 20791 Another effect by which fast electrons can be ~or~ed is the formation of positive ions by the electrons of the electron beam, Said ions move towards the cathode and also release Yast elactrons there.
A third ef~ec-t by which fast electrons ~ ; can be formed is interaction between the electrons of ; the electron beam mutually. This latter ~ffect has been found to be a very important cause of an excess of fast electrons. Said interactions which may be compared with i 10 collisions take place, for example, between two elec-trons moving one behind the other which follo~s paths intersecting each other at an angle. By mutual repelling, the front electron will start mo~ing faster and the rear one will start moving more slowly 50 that an excess o~
fast electrons is formed.
~ : !
- The article "Een Kleine Experin~entela i Kleurentelevisiecamera" in Philips Technisch Tijdschrift vol. 29, 1968, No~ 11, describes a device in ~lich the electron beam which is generated by a triode electron g~un having a cathode, a grid and an anode, is focused ; in a so-called cross-over by tha electric field between , said electrodes. Said cross-over is situa~ed approximate-l~ at the area of the anode. The apertures in the grid and the anode have a cylindrical shape. The anode forms one assembly with th~ first electrode of the focusing lens and is at a positive voltage of 300 V. The said oross-over is displayed on a photoconductive layer by the focusing lens.
A device of the kind described in the flrst paragraph having a considerably smaller beam current inertia than the de~ice having~ a triode gu~ which ls described above is disclose~ in United ~tates Patent Spe-cification 3,831,058 (PHN 5070~. The clevice described in said Specification comprises a diode gun with centred along an axis, successi~ely, a cathode, an anode having an aperture to generate nn alectron beam and a focusing lens tc focus the electron beam on a photooonductive layer. During scalming the current de~lsity ~f the electron :. .
.. ..
~3 18~
i ~ -1979 4 Pl-~ 20791.
?
` beam in any point along the axls between the cathode and the anode in the diode gun described is at most three : times the current density in the point of intersection I of the axls with the cathode. In fact it has pro~red of ¦ . S importance for reducing the beam current inertia to restrict the number of interactions between the electrons o~ the electron beam mutually. In a triode ~un in which 1. a cross-over ls formed~ very many interactions take plac0 : in the proximity of said cross-over so that the beam current inertia i~ adversely influenced. By ensuring that the current density of the electron beam in a diode gun in the direction from the cathode to the anode does not increase or hardly increases and pre~erably even de-creases, the beam current inertia is considerably re-duced.
Neverthel.ess, however, s~ch a diode gun has a number of imperfections. In fact it has been found that when such a diode gun is used in camera tubes with magnetic focusing, an interference signal may occur 20 which i.s caused by f`ast second.ary electrons which are released by the returni.ng beam from the anode (the so-called return beam effect).
In addition it has been found that with dynamic beam current control by means of feedback coupling of the video.signal on the anode, it must be possible to i.ncrease the beam current temporarily b~r a factor 5 tb 10. In diode guns without the ~`ormation o~ a cross-o~er, ~or example as de~cribed in United States Patent Specifi-cations 3,811,058 and 3,~94,261, the beam current is pro-portional to the cathode curr0nt so that, when the beamcurrent increases by a factQr 5 to 10, the cathode current will also increa.se by the above-mentioned factor. This : results in a heavy load of th~ cathode~ In addition7 a rather large amplitude of the oontro}. signal is.required when dynamic beam current control is used.
It is thsrefore an. object of the inven-tion to provide a device in which the above-~nentioned interference signal which i.s caused by the returning bea.n~
.
.
- .~
, .
4-1-1979 5 PHA 207;1 does not occur and in which with dynamic beam current control both the ahove-mentioned increase of the beam . current is achieved with a m~ch lower cathode load, and a control signal may be usecl ha~ing a smaller amplitude : S than in the known diode guns, in which device, however, the beam cu.rrent inertia nevertheless is as small as possible.
A device of the kind mentioned in the ' opening paragraph is characterized according to the in-~ention in that the diameter of the aperture in the first electrode which ~orms a first anode is at least twice as large as the diameter of the aperture in the second electrode which forms a second anode, which aperture in the first anode, however, is so small that a lens ~ield , 15 is formed between the first and the second anode which ~i has nearly no influence on the cathode emission and the :~ . device comprises means to apply a positive voltage of a few to a few tens o~ Volts to the first anode and a ' . positive voltage which is at lea.st ten times higher and . 20 which is at least 100 Volts to the second anode.
- In such a diode gun the second anode has a voltage f.i. of approximatwly 3OO Volts, exactly as in a known conventional triode gun and shows a cornpa-rable intensity of the said inter~erence signal as a result o* the returning b~am not obser~rable at the usual beaM current ad~ustment. In suoh a diode gun having a f'irst and a second anode, when the voltage at the fir~t anode is increasecl with the desoribed dynamic beam currerlt control~ the part of the beam having a larger ourrent densit~ mo~es in the directio~ of the second anode so that a lar,ger percentage o~ the cathode current passes throllgh the diaphragm in the second anode. As a result of t.his the beam ourrent increases more than pro-portional with the cathod.e current so that the increase ot` the beam current :is achiev0d with a considerably lower cathode load and a smaller control signal than in the known diode guns.
The diam~ter of the aperture in the ~ .
, .
, ~ ,, ,.,, . . ~ , .. ....... . .... .. . . ...... .. . .. . .. . .. .
! .
4- l-1979 6 PHA 20791 first anode is preferably approximately Pour times as large as the diameter of the aperture in the second anode.
' A television camera tube ~or a device I embodying the invention which has part:icularly good pro-5 perties is characterized in that the diameter of the aper-, ture in the first anode is approcimately O.Z mm., the diameter of the aperture in the second anode i.s approxi-j mately 0.05 mm, the spaoing between the cathode and the anode is approximately O.3 mm, and the spacing between 10 the first and the second anode is approximately O.7 mm.
The invention will now be described in greater detail with reference to the accompanying drawing of an embodiment, in which i ~igure 1 is a diagrammatic longitudinal 15 sectional view of a television camera tube embodying the invention, igure 2 sho~s diagrammatically a part of the eleetron gun of the tube shown in Figure l,~and - ~'igure 3 is a graphic representation - 20 of the velocity distribution of the electrons in the form of three accHptance curves of three di~ferent types of` guns. ~ ~
~, ~ The camera tube embodying the invention shown in Figure 1 is of the Plumbicon type and comprises 25 a glass envelope 1 having on one side a front plate 2 on which a ]ayer 3 is provided which consists of a photo-sensitive layer ~.i. a photoconduct~ve layer and a con-' ductive transparent signal plate between th~ photosensi-f tl~e layer and the said ~ront plate 2. The photoconduct-30 ive layer conslsts mainly of speciall~ activated lead monoxide and the signal plate corlsist~s QI~ conductive tin dioxicle. The conn~ction pins 4 o~ th~a tube are situated on the other sidH o~ the envelope 1. Centred along an axis 5, the camera tube corr~rrises an electron 3s gun 6 and a focusing lens 7. The tube furthermore com- ;
;Qrises a gauze electrode 8 to cause perpendieular land-ing of the electrons Oll the layer 3, as well as a set of deflection coils 9 which are sho~n diagrammatically.
~ . , i 4-1-1979 7 PX~ 20,91 These deflection coil~s serve to deflect the electron beam produced by the electron gun 6 in two mutually perpendicular directions and are situated around the envelope 1. The electron gun 6 comprises a cathode 10, a first anode 11 and a second anode l2. The correction of the said components and their connections to the con-nection pins 4 are not shown in the Figure to avoid com-plexity of the drawing. The first anode 11 has a small aperture 13. The aperture in the second anode 12 is closed partly by a plate 14 having an aperture 15 the diameter of which is only approximately 1/4 o~ the dia-meter of the aperture in the first anode. As a result of this~ a lens field is formed between the first and second anodes which has substantially no influence on the emission of the cathode 10. Focusing coil 16 fo-cuses the beam on the layer 3.
~ igure 2 is a diagrammatic sectional view of a pa~t of an electron gun shown in Figure 1.
The electrodes are connected together in known manner by means of metal braces 17 and glass rods 18. The electron gun comprises a cathode 10, a first anode 11 having an aperture 13 therein of a diameter of 0.2 mm.
The spacing taken along the axis 5 batween the cathode 10 and the first anode 11 is 0,3 mm. The diameter o~
the aperture 15 in plate 14 of the second anode ?~ is 0.05 mm. The spacing between the first anode and the second anode i.s 0.7 mm. At the potentials shown in the Figure on the cathocle, the first anode and the second anode, this electron gun operates optimally.
~igure 3 shows a few acceptance curves.
Acceptance curve is to be understood to mean herein the curve which represents the rèlationship between the current intensity which the photosensitive la~er accepts and the voltage which the photoconductive layer has 3s relative to the cathode. The acceptance curve is closely related to the v~locity distributlon of the electrons in the beam. In fact, the complete beam current is accepted for a sufficiently large positive voltage of the photo-., ... ., ..... ...... ~ . ......... . . . . , . . . , : . ~
~.
, sensitive layer. The lower the voltage o~ the photo-sensitive layer (the more negati~-e) the faster the elec-trons ha~e to be to be able to reach the photosensitive layer and thus the smaller becomes the accepted current strength. If for the acceptance curve the logarithm of the accepted current is plotted against the voltage of the photosensitive layer, the acceptance curve for a true Maxwell distribution consists of a straight portion ; having a slope which is determined by the temperature of to the cathode changing with a bend into a straight portion which indicates -that the whole beam currant is accepted.
The steeper the first mentioned section i5, the lower is the associated cathode temperature. An excess of fast electrons gives a so-called tail to the acceptance curve at low voltages so that the photosensitive la~er can even be charged negatively. The central curve in ~he ~igure (T = 1300K) is the acceptance curve of the device embodying the invention. The voItage of the photosensi tive layer is plotted on the horizontal axis (one unit is 0.2 Volt) on a linear scale and the accepted current in Ampères is plotted on the vertical on a logarithmic scale. The acceptance curves of the known devices are also shown in the Figure for purposes o~ comparison. The left-hand curve is the acceptance curve of a triode gun (T = 1900 K) and the right-hand curve is the acceptance curve of the known diode gun (T _ 1200K). So it may be seen that the gun embodying the invention will be compa-rable to the known diode gun as regards the response rate~
However, as a rcsult of the high voltage at the second anode the interference signal which is caused by the re-turnirlg beam is substantially not present, as in a triode gun. Moreover, dynamic ~eam current control may take place with Q considerably lower cathode load and with a smaller control signal than would be necessary in a diodo gun accordillg to the constluction Icnowrl so far.
'.
.,
4-1-1979- i PHA 20'791 ~'Dcvice comprising a tele~ision camera tube and television camera tube`~or such a device".
~.
:~ ~ The invention relates to a device com- -prising a television camera tube having an electron gun to generata an electron beam, which electron ~In - comprises, centred along an axis, successively a ~ S cathode, a first electrode having an aperture~ a . seoond electrode havillg an aperture, and a focusing lens to focus the electron beam on a photo~sensitive layer provided on a signal plate, a potential distri-bution being ~ormed on said photosensiti.ve layer by projecting an optical image on it, ~aid signal plate providing electric signals corresponding -to the sai.d optical image by scanning the pnotosensitive .layer by means of the electron beam.
; The invention also relates to a television camera tube ~or such a device~
The said potential distribution, sonletimes termed potential ima~r3, is formed in t~at the photosen-sitive layer may be considered as being composed o~ a ; large nwnb,3r o~ picture elernellts. Each picture ,element . rnay ~e corl~idered as a capa"itor to which:-ls connected in parallel a current source whose currerlt str-ength:i.s : substantiall.y E)roportional to t]l~i3 li,~ht in.tensity OD.
the picture element. So th.e ohar~e o~ eacll capacl,~or decreases linearly with -kime at, con,;tan~ light in,,ensi-ty.
,: ., ~ . ... , :. ,".. , , , , ,, .. : . . ..
, :
;~ ,, ., ., , , .................................. ,~æ
.
4-1-'i979 ~ P~ 20791 , ' As a result of the scanni~g t'he electron beam pas~ses each picture element periodically and then charges th~s capacitor, that is to sa~ that the voltage across each picture element is brought periodically at approximat-S ely 45 Volts. The quantity oP charge n0cessary to per-iodically charge a capacitor is proportional to tha light intensity on the'relevant picture elementc The associated current flows via the signal plate which is common to all the picture elements through a si~nal resistor so that across the si~nal resistor a~oltage is formed which as a function of time represents the li~ht intensitr of the optical ima~e as a function of' the place. A television camera tube having the descri-bed effect is generally termed a vidicon.
One of the aspects of a device o~ tha above-described type îs the response rate, that is to say the velocity at which the device reacts to variat-~,~ ions of thelight~intensit~. The response rate i8 in-fluenced inter alia by the ~act that the charge which the electron beam supplies to the picture element in ; the short period o~ time in which it passes a givell picture element depends on~the ~elocity distribution of the elactrons in the electron beam. This influence of the response rate is termed beam current inertia.
The velocity distribution of the electrons leaving the cathode depends on the temperature o~ the catho~e and is referred to as Maxwell distribution. As a re-sult of e~ects to be m~ntioned hereina~ter, however,~
an excesso~ ~ast electrons ma~ arlse, that is to say, ' there are moYe~ast elect;rons in the bearn than corres-pon-lstO the Maxwell distribution.'This excess of fast electrQns causes a detrimental in~luence o~ the beam current inertia and hence of t;he response rate.
An e~fect by ~rhich rast electrons can 3S be formed is X~ray radiation as a result o~ electlons of the electron beam whic'h impinge on the anode. This ; X-ray radiation may release fast electrons from the cathode.
r ~; ' t~' ~-1-1979 3 PHA 20791 Another effect by which fast electrons can be ~or~ed is the formation of positive ions by the electrons of the electron beam, Said ions move towards the cathode and also release Yast elactrons there.
A third ef~ec-t by which fast electrons ~ ; can be formed is interaction between the electrons of ; the electron beam mutually. This latter ~ffect has been found to be a very important cause of an excess of fast electrons. Said interactions which may be compared with i 10 collisions take place, for example, between two elec-trons moving one behind the other which follo~s paths intersecting each other at an angle. By mutual repelling, the front electron will start mo~ing faster and the rear one will start moving more slowly 50 that an excess o~
fast electrons is formed.
~ : !
- The article "Een Kleine Experin~entela i Kleurentelevisiecamera" in Philips Technisch Tijdschrift vol. 29, 1968, No~ 11, describes a device in ~lich the electron beam which is generated by a triode electron g~un having a cathode, a grid and an anode, is focused ; in a so-called cross-over by tha electric field between , said electrodes. Said cross-over is situa~ed approximate-l~ at the area of the anode. The apertures in the grid and the anode have a cylindrical shape. The anode forms one assembly with th~ first electrode of the focusing lens and is at a positive voltage of 300 V. The said oross-over is displayed on a photoconductive layer by the focusing lens.
A device of the kind described in the flrst paragraph having a considerably smaller beam current inertia than the de~ice having~ a triode gu~ which ls described above is disclose~ in United ~tates Patent Spe-cification 3,831,058 (PHN 5070~. The clevice described in said Specification comprises a diode gun with centred along an axis, successi~ely, a cathode, an anode having an aperture to generate nn alectron beam and a focusing lens tc focus the electron beam on a photooonductive layer. During scalming the current de~lsity ~f the electron :. .
.. ..
~3 18~
i ~ -1979 4 Pl-~ 20791.
?
` beam in any point along the axls between the cathode and the anode in the diode gun described is at most three : times the current density in the point of intersection I of the axls with the cathode. In fact it has pro~red of ¦ . S importance for reducing the beam current inertia to restrict the number of interactions between the electrons o~ the electron beam mutually. In a triode ~un in which 1. a cross-over ls formed~ very many interactions take plac0 : in the proximity of said cross-over so that the beam current inertia i~ adversely influenced. By ensuring that the current density of the electron beam in a diode gun in the direction from the cathode to the anode does not increase or hardly increases and pre~erably even de-creases, the beam current inertia is considerably re-duced.
Neverthel.ess, however, s~ch a diode gun has a number of imperfections. In fact it has been found that when such a diode gun is used in camera tubes with magnetic focusing, an interference signal may occur 20 which i.s caused by f`ast second.ary electrons which are released by the returni.ng beam from the anode (the so-called return beam effect).
In addition it has been found that with dynamic beam current control by means of feedback coupling of the video.signal on the anode, it must be possible to i.ncrease the beam current temporarily b~r a factor 5 tb 10. In diode guns without the ~`ormation o~ a cross-o~er, ~or example as de~cribed in United States Patent Specifi-cations 3,811,058 and 3,~94,261, the beam current is pro-portional to the cathode curr0nt so that, when the beamcurrent increases by a factQr 5 to 10, the cathode current will also increa.se by the above-mentioned factor. This : results in a heavy load of th~ cathode~ In addition7 a rather large amplitude of the oontro}. signal is.required when dynamic beam current control is used.
It is thsrefore an. object of the inven-tion to provide a device in which the above-~nentioned interference signal which i.s caused by the returning bea.n~
.
.
- .~
, .
4-1-1979 5 PHA 207;1 does not occur and in which with dynamic beam current control both the ahove-mentioned increase of the beam . current is achieved with a m~ch lower cathode load, and a control signal may be usecl ha~ing a smaller amplitude : S than in the known diode guns, in which device, however, the beam cu.rrent inertia nevertheless is as small as possible.
A device of the kind mentioned in the ' opening paragraph is characterized according to the in-~ention in that the diameter of the aperture in the first electrode which ~orms a first anode is at least twice as large as the diameter of the aperture in the second electrode which forms a second anode, which aperture in the first anode, however, is so small that a lens ~ield , 15 is formed between the first and the second anode which ~i has nearly no influence on the cathode emission and the :~ . device comprises means to apply a positive voltage of a few to a few tens o~ Volts to the first anode and a ' . positive voltage which is at lea.st ten times higher and . 20 which is at least 100 Volts to the second anode.
- In such a diode gun the second anode has a voltage f.i. of approximatwly 3OO Volts, exactly as in a known conventional triode gun and shows a cornpa-rable intensity of the said inter~erence signal as a result o* the returning b~am not obser~rable at the usual beaM current ad~ustment. In suoh a diode gun having a f'irst and a second anode, when the voltage at the fir~t anode is increasecl with the desoribed dynamic beam currerlt control~ the part of the beam having a larger ourrent densit~ mo~es in the directio~ of the second anode so that a lar,ger percentage o~ the cathode current passes throllgh the diaphragm in the second anode. As a result of t.his the beam ourrent increases more than pro-portional with the cathod.e current so that the increase ot` the beam current :is achiev0d with a considerably lower cathode load and a smaller control signal than in the known diode guns.
The diam~ter of the aperture in the ~ .
, .
, ~ ,, ,.,, . . ~ , .. ....... . .... .. . . ...... .. . .. . .. . .. .
! .
4- l-1979 6 PHA 20791 first anode is preferably approximately Pour times as large as the diameter of the aperture in the second anode.
' A television camera tube ~or a device I embodying the invention which has part:icularly good pro-5 perties is characterized in that the diameter of the aper-, ture in the first anode is approcimately O.Z mm., the diameter of the aperture in the second anode i.s approxi-j mately 0.05 mm, the spaoing between the cathode and the anode is approximately O.3 mm, and the spacing between 10 the first and the second anode is approximately O.7 mm.
The invention will now be described in greater detail with reference to the accompanying drawing of an embodiment, in which i ~igure 1 is a diagrammatic longitudinal 15 sectional view of a television camera tube embodying the invention, igure 2 sho~s diagrammatically a part of the eleetron gun of the tube shown in Figure l,~and - ~'igure 3 is a graphic representation - 20 of the velocity distribution of the electrons in the form of three accHptance curves of three di~ferent types of` guns. ~ ~
~, ~ The camera tube embodying the invention shown in Figure 1 is of the Plumbicon type and comprises 25 a glass envelope 1 having on one side a front plate 2 on which a ]ayer 3 is provided which consists of a photo-sensitive layer ~.i. a photoconduct~ve layer and a con-' ductive transparent signal plate between th~ photosensi-f tl~e layer and the said ~ront plate 2. The photoconduct-30 ive layer conslsts mainly of speciall~ activated lead monoxide and the signal plate corlsist~s QI~ conductive tin dioxicle. The conn~ction pins 4 o~ th~a tube are situated on the other sidH o~ the envelope 1. Centred along an axis 5, the camera tube corr~rrises an electron 3s gun 6 and a focusing lens 7. The tube furthermore com- ;
;Qrises a gauze electrode 8 to cause perpendieular land-ing of the electrons Oll the layer 3, as well as a set of deflection coils 9 which are sho~n diagrammatically.
~ . , i 4-1-1979 7 PX~ 20,91 These deflection coil~s serve to deflect the electron beam produced by the electron gun 6 in two mutually perpendicular directions and are situated around the envelope 1. The electron gun 6 comprises a cathode 10, a first anode 11 and a second anode l2. The correction of the said components and their connections to the con-nection pins 4 are not shown in the Figure to avoid com-plexity of the drawing. The first anode 11 has a small aperture 13. The aperture in the second anode 12 is closed partly by a plate 14 having an aperture 15 the diameter of which is only approximately 1/4 o~ the dia-meter of the aperture in the first anode. As a result of this~ a lens field is formed between the first and second anodes which has substantially no influence on the emission of the cathode 10. Focusing coil 16 fo-cuses the beam on the layer 3.
~ igure 2 is a diagrammatic sectional view of a pa~t of an electron gun shown in Figure 1.
The electrodes are connected together in known manner by means of metal braces 17 and glass rods 18. The electron gun comprises a cathode 10, a first anode 11 having an aperture 13 therein of a diameter of 0.2 mm.
The spacing taken along the axis 5 batween the cathode 10 and the first anode 11 is 0,3 mm. The diameter o~
the aperture 15 in plate 14 of the second anode ?~ is 0.05 mm. The spacing between the first anode and the second anode i.s 0.7 mm. At the potentials shown in the Figure on the cathocle, the first anode and the second anode, this electron gun operates optimally.
~igure 3 shows a few acceptance curves.
Acceptance curve is to be understood to mean herein the curve which represents the rèlationship between the current intensity which the photosensitive la~er accepts and the voltage which the photoconductive layer has 3s relative to the cathode. The acceptance curve is closely related to the v~locity distributlon of the electrons in the beam. In fact, the complete beam current is accepted for a sufficiently large positive voltage of the photo-., ... ., ..... ...... ~ . ......... . . . . , . . . , : . ~
~.
, sensitive layer. The lower the voltage o~ the photo-sensitive layer (the more negati~-e) the faster the elec-trons ha~e to be to be able to reach the photosensitive layer and thus the smaller becomes the accepted current strength. If for the acceptance curve the logarithm of the accepted current is plotted against the voltage of the photosensitive layer, the acceptance curve for a true Maxwell distribution consists of a straight portion ; having a slope which is determined by the temperature of to the cathode changing with a bend into a straight portion which indicates -that the whole beam currant is accepted.
The steeper the first mentioned section i5, the lower is the associated cathode temperature. An excess of fast electrons gives a so-called tail to the acceptance curve at low voltages so that the photosensitive la~er can even be charged negatively. The central curve in ~he ~igure (T = 1300K) is the acceptance curve of the device embodying the invention. The voItage of the photosensi tive layer is plotted on the horizontal axis (one unit is 0.2 Volt) on a linear scale and the accepted current in Ampères is plotted on the vertical on a logarithmic scale. The acceptance curves of the known devices are also shown in the Figure for purposes o~ comparison. The left-hand curve is the acceptance curve of a triode gun (T = 1900 K) and the right-hand curve is the acceptance curve of the known diode gun (T _ 1200K). So it may be seen that the gun embodying the invention will be compa-rable to the known diode gun as regards the response rate~
However, as a rcsult of the high voltage at the second anode the interference signal which is caused by the re-turnirlg beam is substantially not present, as in a triode gun. Moreover, dynamic ~eam current control may take place with Q considerably lower cathode load and with a smaller control signal than would be necessary in a diodo gun accordillg to the constluction Icnowrl so far.
'.
.,
Claims (3)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A device comprising a television camera tube having an electron gun to generate an electron beam, which electron gun comprises. centred along an axis, successively a cathode, a first electrode having an aperture, a second electrode having an aper-ture, and a focusing lens to focus the electron beam on a photosensitive layer provided on a signal plate, a potential distribution being formed on said photo-sensitive layer by projecting an optical image on it, said signal plate providing electric signals correspond-ing to the said optical image by scanning the photo-sensitive layer by moans of the electron beam, character-ized in that the diameter of the aperture in the first electrode which forms a first anode is at least twice as large as the diameter of the aperture in the second electrode which forms a second anode, which aperture in the first anode, however, is so small that a lens field is formed between the first and second anodes which has nearly no influence on the cathode emission and the device comprises means to apply a positive voltage of a few tens of volts to the first anode and a positive voltage which is at least ten times higher and which is at least 100 volts to the second anode.
2. A television camera tube for a device as claimed in Claim 1, characterized in that the diameter of the aperture in the first anode is approximately four times as large as the diameter of the aperture in the second anode.
3. A television camera tube for a device as claimed in Claim 2, characterized in that the diameter of the aperture in the first anode is approximately 0.2 mm, the diameter of the aperture in the second anode is approximately 0.05 mm, the spacing between the cathode and the anode is approximately 0.3 mm and the spacing between the first and the second anode is approximately 0.7 mm.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US87708078A | 1978-02-13 | 1978-02-13 | |
| US877,080 | 1978-02-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1118831A true CA1118831A (en) | 1982-02-23 |
Family
ID=25369206
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000321220A Expired CA1118831A (en) | 1978-02-13 | 1979-02-08 | Device comprising a television camera tube and television camera for such a device |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS54129871A (en) |
| CA (1) | CA1118831A (en) |
| DE (1) | DE2904865A1 (en) |
| FR (1) | FR2417182A1 (en) |
| GB (1) | GB2015817B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5774948A (en) | 1980-10-29 | 1982-05-11 | Nippon Hoso Kyokai <Nhk> | Electron gun |
| US4549113A (en) * | 1981-02-06 | 1985-10-22 | U.S. Philips Corporation | Low noise electron gun |
| US4540916A (en) * | 1981-10-30 | 1985-09-10 | Nippon Hoso Kyokai | Electron gun for television camera tube |
| US4701679A (en) * | 1985-08-23 | 1987-10-20 | Hitachi, Ltd. | Method of and apparatus for controlling amount of electron beam in image pickup tube |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3374379A (en) * | 1964-03-02 | 1968-03-19 | Nippon Columbia | Low second grid voltage electron gun |
| BE759247A (en) * | 1969-11-22 | 1971-05-21 | Philips Nv | DEVICE EQUIPPED WITH AN ELECTRONIC TUBE, AND ELECTRONIC TUBE INTENDED FOR SUCH A DEVICE |
| NL167801C (en) * | 1970-09-04 | 1982-01-18 | Philips Nv | DEVICE WITH A TELEVISION CAMERA TUBE AND TELEVISION CAMERA TUBE FOR SUCH A DEVICE. |
| BE785749A (en) * | 1971-07-02 | 1973-01-02 | Philips Nv | TELEVISION CAMERA TUBE (VIDICON) IN WHICH THE ADVERSE INFLUENCE OF THE RETURN BEAM IS COUNTERLED |
| US3831058A (en) * | 1971-08-30 | 1974-08-20 | Roosmalen J Van | Device comprising a television camera tube and television camera |
| US3894261A (en) * | 1973-07-09 | 1975-07-08 | Hughes Aircraft Co | No-crossover electron gun |
| GB1444062A (en) * | 1974-06-08 | 1976-07-28 | English Electric Valve Co Ltd | Camera tubes |
-
1979
- 1979-02-02 JP JP1053579A patent/JPS54129871A/en active Granted
- 1979-02-08 CA CA000321220A patent/CA1118831A/en not_active Expired
- 1979-02-09 GB GB7904587A patent/GB2015817B/en not_active Expired
- 1979-02-09 DE DE19792904865 patent/DE2904865A1/en active Granted
- 1979-02-12 FR FR7903490A patent/FR2417182A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0213416B2 (en) | 1990-04-04 |
| GB2015817B (en) | 1982-06-03 |
| JPS54129871A (en) | 1979-10-08 |
| DE2904865A1 (en) | 1979-08-16 |
| FR2417182A1 (en) | 1979-09-07 |
| GB2015817A (en) | 1979-09-12 |
| DE2904865C2 (en) | 1987-12-10 |
| FR2417182B1 (en) | 1984-02-24 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0966752B1 (en) | Correction device for correcting the lens defects in particle-optical apparatus | |
| CA1140197A (en) | Unipotential lens assembly for charged particle beam tubes and method for applying correction potentials thereto | |
| US3548250A (en) | Apparatus having a television camera tube and television camera tube for use in such an apparatus | |
| US3928784A (en) | Television camera tube with control diaphragm | |
| CA1118831A (en) | Device comprising a television camera tube and television camera for such a device | |
| EP0114714B1 (en) | Device comprising a cathode ray tube having low noise electron gun | |
| US3831058A (en) | Device comprising a television camera tube and television camera | |
| US4388556A (en) | Low noise electron gun | |
| US3866079A (en) | Television camera tube in which the detrimental effect of the return beam is counteracted | |
| US2760096A (en) | Television pickup tube | |
| US2939954A (en) | X-ray shadow microscope | |
| US2213179A (en) | Television transmitting device | |
| US3433996A (en) | Storage system | |
| US2152825A (en) | Braun tube | |
| US2619531A (en) | Pickup tube for television and the like | |
| US3883773A (en) | Device comprising a television camera tube | |
| GB2097182A (en) | Picture display device | |
| NL8204185A (en) | CATHED BEAM TUBE. | |
| EP0084915B1 (en) | Television camera tube | |
| US3870002A (en) | Television camera tube with three electrode focusing lens | |
| US3179840A (en) | Method of obtaining uniform response from a television camera device | |
| US3453484A (en) | Storage device | |
| US3243646A (en) | Cylindrical compensating electrode for electrostatic lens of cathode ray tube | |
| JPH01220341A (en) | Image tube | |
| US2845561A (en) | Tube for storage of images |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |