Note: Descriptions are shown in the official language in which they were submitted.
PHN 8262 ~ ~
~g7485~ ~
The invention relates to a method of manu-
facturing a cathode ray tube for displaying coloured
pictures and comprising in an evacuated envelope means
~o generate a number of elec~ron beams~ a display
S screen compris;ng a large number of regions luninescing
in different colours, and colour selection means com-
prising a large number of apertures which associate
each electron beam with luminescent regions of one colour,: :~
which colour selection means comprise electrodes to Form
lU an electron lens in each aperture.
The invention also relates to a cathode ray
tube manufactured according to this method and tho the ~:.
colour selection means as used in such a cathode ray tube.
Such a cathode ray tube of the reFocusing
; 15 type is known From the United States Patent SpeciFication
3,398,309 which issued to The Rauland Corporation on ~ .
August 20, 1968. The object of refocusing is to increase
the br~ghtness of the displayed plcture by increasing the
transmission of the colour selection means. In tubes
2D wl~hout reFocusing a very great part, for example 80 to
~ 85%, of the electrons is intercepted by the so-called
:n shadow mask. By the use of refocusing the apertures
in the colour selection means can be enlarged since as
a result Qf the focusing in the apertures the electron . .
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spots on the screen are considerably smaller than the
apertures so that in spite of the increased si~e of
aperture sufPicient landing tolerance exists.
The electron lens which is formed in the
apertures of the shadow mask of the known tube is of the
unipotential type as a result of which a rather great
voltage difference is reqwired between the electrodes
which form the lens.
Another refocusing tube is described in the
United States Patent Specification 2,728,024 which issued
to Radio Corporation of America on December 20, 195~. In
this tube the electron beams pass successively through two
grids which consist of parallel conductors. The conductors
associated with different grids are at right angles to
each other. The result of this is that the electron beams
are successively focused by two electron-optical cylinder
lenses which are rotated 90 relative to each other. As
a resul~ of the action of both lenses together, the
electron beams are focused in one direction and are de-
focused ln a direction at right angles thereto.
Anokher drawback of this known tube is that a
rather large voltage difference for the focusing is
necessary. In addition, both grids do not form a mechani-
cal unit so that the vibration of the grid wires presents ~ -~
great problems. In addition it is necessary for the dis-
play screen to be flat.
It is the object of the invention to provide
' a method of manufacturing an improved cathode ray tube
; for displaying coloured pictures of the kind ment-ioned
in the preamble.
The invention makes it also possible to manu-
facture curved plate-shaped colour selection means of
a usual s~ze.
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3L~)74~52 PHN 8262
According to the invention, a method of the
kind mentioned in the ~irst paragraph is characterized in
that the colour selection means are manuFactured from a
few metal plates which are secured together with the inter- .
position of insulation material so that the plates do not
contact each other, and in which method at: least one of
the plates, prior to the plates being secured together, is
provided with a pattern which is composed of a number of
substantially parallel ridges between which a number of
strip-shaped regions are situated in which the plate has a
much smaller thickness than at the area of the ridges, the
material of said strip-shaped regions being removed after
securing the plates together.
As a result of the removal o~ the material of
the strip-shaped regions, the ridges remain which form
parallel conductive strips and are secured against the
other plate(s) while being separated by an insulator. In
; this manner the electrodes for forming an electron lens
aré formed.
The colour selection means may be manufactured : :
From two metal plates which one plate is provided with .
apertures and the other p1ate is provided with the said
relief pattern, the method including the step of position-
ing the plates together in such manner that the apertures . :
~5 on one plate become situated between the ridges of the
other plate, colour selection means are thus obtained
which are formed from a meta1 plate having the said
apertures with conductive strips between the apertures.
: The apertures may be provided in one plate already in
an earlier stage of the process or may be obtained
by etching together with the removal of the material ~- ~
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~LC~7 ~8~jZ PHN 8262
of the strip-shaped regions of the other plates by means of an
etching process. The ridges may be provided on two sides of
; the plate or only on one side which may then be remote from
the other plate or may iust be arranged against it.
When the colour selection means according to the
invention are formed from two plates which are both provided
with the said relief pat~ern and the plates are secured to-
gether in such manner that the ridges enclose an angle of
approximately 90 with respect to each other, then, after
removing the strip-shaped regions, colour sèlection means
are formed in this manner which are formed from a grid con-
sisting o~ two sets of substantially parallel conductors
which cross each other, which conductors are insulated from
each other at the crossings and in which ~he conductors of
; 15 each set may be mutually interconnected. In this manner, by
applying a voltage difference between the sets, a quadrupole
lens is formed in each aperture of the said colour selection
means. Since the electric field is at right angles to the
- electron pathg quadrupole lenses are very strong as compared
with the said cylinder lenses so that much lower voltages
than in said cylinder lenses will suffice. That a quadrupole
lens focuses in one direction and defocuses in a direction at
right angles thereto is no drawback in principle when all
quadrupole have the same orientation. Therefore, the
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luminescent regions of the display screen preferably have the
shape of substantially parallel strip the longitudinal direc-
tion of which is substantially parallel to the de~ocuslng
direction of quadrupole lenses.
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The relief pattern is provided in the plates by
means of known technologies~ for example, etching, rolling,
spark ero~ion and moulding.
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The great advantage of such a method accordiny to
the invention is that the individual plates have a great
rigidity so that colour selection means of large dimensions
and a curved shape can be manufactured. Moreoverg the con-
ductive strips are provided against the other plate at the
desired distance from each other.
The embodiment of the method is that in which the
insultation material is glass which is provided on at least
one of the plates in the form of glass powder~ aFter which
n ;t is converted inbo solid glass by a thermal treatment and
the excessive glass, after removing the material of the said
strip-shaped regions, is removed.
The glass powder may be provided on the plates,
for example, by spraying, silk-screening, settling ~depositing)
or by means of tape containing glass powder and known com-
mercially as Vitta. In order to minimize the quality oP
excessive glass between these p~ates, for example, the area
not to be coated may be covered with a template during spraying
and depositing.
An elegant method of providing the glass is that
in which one of the plates which is provided with a relief
pattern ~s then covered with an insulator so that only the
ridges remain uncovered~ which ridges are then coated with glass
powder electrophoretically, after which the insulator is re-
moved, which glass powder is converted into solid glass by a
thermal treatment, after which the plate with the covered
` ridges is secured against a second plate. As suitable insula-
tors may be used inter alia methacrylate resins, polyimides,
beeswax or paraffin.
The electrophoretic coating with glass powder
is preferably carried out in an e1ectrophoresis bath which
contains as a carrier liquid an alcohol~ preferably
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PHN 8262
methanol, in which the glass powder is suspended.
The removal of the excessive glass may be carried
ou~ by means of powder blasting from both sides in which the
glass on the apertured plate or the glass at the crossings of
the grid is in the "shadow" of the conductive strips. Excens-
s;ve glass is the glass which has no adhering and insulating
functions, for example, the glass which is present on the
conductors, not at the crossings.
Other very suitable insulators for the method
according to the invention are re~ractory synthetic materials
so that another preferred embodiment of the method according
to the invention is characterized in that a refractory synthetic
foil ;s provided between the plates as an insulator and that
the excessive synthet;c material (no adhering and insulat;ng
function) and the material of the said regions are removed.
The synthetic material should be refractory because the cathode
ray tube reaches temperatures up to 500C during securing the
display window to the oone and during evacuating.
The synthetic foil may also be used read as an
adhesive for securing the plates together, when the synthetic
fo;l is wetted at least on one side with an adhesive for the
synthetic material of which the foil consists before it ;s
provided between the plates. A number of synthetic materials
adhere only after they have been subjected to a thermal treat-
ment. In said treatment gases are formed so that it is
recommendable to provide at least one of the plates with a
number of small apertures for the escape of the sa;d gases.
Very suitable synthetic materials are the polyi-
mides of which the poly~mide of 4-4' d;aminod;phenyl ether
and 1-~-4-5 benzenetetracarbonic ac;d dianhydr;de
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PHN 8262
proves to give particularly good satisfaction and is
available inter alia in a foil form under the name of
Kapton which is a registered trade mark of Dupont.
; The plates may not contact each other even when
the intermediate insulation materials become soft and
must remain insulated relative to each other. This can
be done by securing them together at the desired distance
in a very defined manner. It can be done in a very simple
manner by keeping the plates at the said desired distance
; lO by means of spacing elements. The spacing elements may,
for example, be spherical and bear between the ridges.
The provision of an insulating layer may also
be done quite differently. IF at least one of the plates
consists of aluminium at a surface, which sur~ace is at
least partly anodized, a suitable insulator layer of
A1203 is obtained. -
When the material of the strip-shaped regions
is not entirely removed, edges are Formed at the ridges
which provide a screening of the insulation material
for the electron beams and/or possible barium parts `
originating from a getter.
; Fmbodiments of the invention will now be
described by the way of example with reference to the
diagrammatic drawings in which:
Figure 1 shows a cathode ray ~ube manuFactured
by a method embodying to the invention,
Figure 2 shows the operation of a quadrupole
lens denoted diagrammatically,
Figures 3a, b and c show the manufacture in
` 30 steps of a plate having a relief pattern,
Figure 4 shows ~wo plates as illustrated in
Figure 3c secured together,
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~1374~3S~ ~
PHN 8262
F;gure 5a shows a part of a cross grid su;table for
colour selection means,
Figure 5b shows the operation of such a cross grid,
Figure 6a and 6b and 7a, 7b and 7c show a few other
possible relief patterns,
Figure 8 shows diagrammatically a method of electro-
phoretic coating with glass powder, ~ .
Figures 9 and 10 show the manufacture of a part ofa cross grid by means of glass powder,
Figure 11 shows an apertured relief plate,
Figures 12 and 13 show spacing elements,
Figure 14 shows a suction plate for securing the
plates together,
Figures 15a, b and c show an anodized aluminium
plate and,
I Fiyures 16a and b show an apertured plate provided with conductive strips.
. The cathode ray tube shown in Figure 1 comprises
:~, a glass envelope 1, means 2 to generate three electron beams
3, 4 and 5, a display screen 6, colour selection means 7 and
deflection coils 8. The electron beams 3, 4 and 5 are gen~
erated in one plane, the plane of the drawing of Figure 1,
and are deflected over the display screen 6 by means of the
deflection coils 8. The display screen 6 consists of a large
number of phosphor strips luminescing in red, green and blue
of approximately 0.13 mm wide, the longitudinal direction
of which is at right angles ~o the plane of the drawing of
Figure 1. During normal operation of the tube the phosphor
strips are vertical and Figure 1 hence is a sectional view of .
3U the tube at right angles to the phosphor strips. The colour ~ ~
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~1:37~5Z
PHN 8262
selection means 7 comprise a large number o~ apertures 9
which are shown diagrammatically only in Figure 1. The
three electron beams 3, 4 and 5 pass through the apertures
9 at a small angle to each other (the so-called colour
selection angle) and consequently each impinge only upon
phosphor strips of one colour. The ape~tures 9 in the
colour selection means 7 are thus very accurately posi-
tioned relative to the phosphor strips of the display
screen 6.
In the nowadays generally used shadow mask
tube, in which the colour selection means consist of a
metal plate having circular or slot-like apertures, the
electron beams 3, 4 and 5 are not focuses upon passing
`~ through the apertures 9. It has been suggested to use
lS post deflection focusing by means of a potential difference
between the colour selection means 7 and the display screen
6 in which, however, annoying effects of secondary electrons
!
are experienced.
In a cathode ray tube manufactured by means of
one of the methods according to the invention, a quadrupole
lens is ~ormed in each aperture o~ the colour selection
means 7. Flgure 2 shows diagrammatically such a quadrupole
lens with a part of the colour selection means 7 and one
of the apertures 9. The potential variation along the edge
2~ of aperture 9 is denoted by ~a ~~ +~ - in such manner that
a quadrupole field is formed. The electron beam which
passes through the aperture 9 is focused in the horizon-
tally drawn plane and is defocused in the vertically drawn
plane so that, when the display screen is exactly in the
horizontal focus, the electron spot 10 is formed. It is
recommendable not to focus exactly on the display screen 6
as a result of which a slightly wider electron spot is ~
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3~7 ~35 Z
PHN 8262
obtained. It is only a minor effect on the focusing when
the electron beam passes through the aperture 9 at a small
angle; as a result of this the colour selection of the three
electron beams 3, 4 and 5 takes place in a manner qu;te
analogous to that in the known shadow mask tube. As a result
of this strong focusing, however, the aperture 9 may be
much larger than in the known shadow mask tube so far more
electrons impinge upon the display screen 6 and a brighter
picture is obtained. The defocusing in the vertical direction
need not be any objection when the phosphor strips are used
which are parallel to the longitudinal direction of the
spot 10.
Figures 3a, b and c diagrammatically show a plate
provided with a relief and used in the invention can be
obtained by etching. Figure 3a is a plan view of a part of
such a plate, Figure 3b is the associated sectional view
and Figure 3c is a perspective view of the result. The
parts of a metal plate 11 which may not be etched away
are covered with an etchant-resistant material 12 which
is provided on the plate in the desired pattern. A relief
pattern as shown in Figure 3c is now obtained by etching,
in which a number of ridges 13 (for example approximately
100 /um thick) are separated by a number of strip-shaped
regions 14 having a smaller thickness (~or example 30 /um).
The relief pattern can also be provided by moulding it in
~he plate, by spark erosion or during a rolling process.
In Figure 4, two of such plates as in Figure
3c are secured together with the ridges 13 facing each other.
It is also possible ~o secure the plates toge~her with the
ridges remote from each other. In certain cases this may
even be more favourable since the plates can more easily --
be bent in a direction at right angles to the direction
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PHN 8262
of the ridges. The connection is ef~ected by means of an
insulator 15 and in such manner that the plates do not contact
each other. How this can be done will be explained herein-
after. ey etching away the strip-shaped regions 14 a cross
grid as is shown in Figure 5a is obtained which consists of
two sets of parallel conductive strips 16 and 17 which are
separated from each other at the crossing by an insulator 15
and which are secured together. The provision of the in-
sulator 15 will be described hereinafter.
Figure 5b shows the operation of such a cross
grid. The colour selection means 7 consist of two sets o~F
parallel conductive strips. Of the first set are shown the
horizontally drawn conductive strips 17 and of the second
set are shown the vertically drawn conductive strips 16.
Together they determine one of the apertures 9. The strips
16 are insulated from the strips 17 by means of an insulator
15. On the display screen 6 the three phosphor strips
associated with the aperture 9 are ;ndicated by R (red),
(green), and B (blue). In the Figure only a few rays of
the central electron beam 4 are shown which ~orm electron spot
10 on the phosphor strip G. The horizontal conductive strips
17 are connected together and are at a higher potential than
the interconnected conductive strips 15 so that the quadru-
pole lens shown diagrammatlcally in Figure 2 is ~formed in
each aperture 9.
- The following results were obtained with
colour selection rr~ans as shown in Figure 5 mounted in a
display tube and having conductive strips 16 and 17 having
a width o~ 0.2~ mm and a mutual pitch of 0.80 rrlm so that the -:
transmission of the colour selection rrleans was appraximately
50%. With a potential of the display screen 6 of 25 kV and
a potential of the horizontal conductors of 25,5 kV and of
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~7~ 5Z
PHN 82~2
the vertical conductors of 24,5 kV, the focal distance of
the quadrupole lenses was 18.0 mm in the centre of the
display screen with perpendicular incidence and was 12.7 mm
with an incidence at 37 in the corners of the display
screen. The distance of the colour selection means 7 to
the display screen 6 was 15 mm in the centre and 10 mm at
the edge so that the focus of the quadrupole lens was every-
where just slightly beyond the display screen. As a result
o~ this a so-called ~ocus ring was not visible on the dis-
play screen. The electron spots are 0.10 mm wide in the
centre o~ the display screen and 0.09 mm in the corners.
A suitable width of phosphor strips R, G and B was found to
be 0.13 mm, the remainder of the surface of the display
screen may or may not be coated with a light-absorbing mater-
ial.
Figures 6a and 6b and Figures 7a, b and c
are sectional views of a number of possible shapes of relief
patterns. With the relief pattern shown in Figure 7a,
strip-shaped conductors as shown in Figure 7b can be obtained
with edges 20. These edges are chosen to be so that the ~`
electron beams passing through the apertures 9 do not touch
the insulation material so that charging o~ the insulator
at the crossings by the electron beam is prevented. Besides
it can be prevented that barium originating from a barium
getter present in the cathode ray tube deposits on the
insulation material and causes shortcircuit there.
A particularly suitable insulator 15 both
to secure the sets o~ conductive strips 16 and 17 together
and to connect a set ~f conductive strips to an apertured
metal plate is glass. Suitably the glass is provided in
powder form and is then converted into solid glass by heating.
The glass powder may be provided by spraying it on thle plate,
the places not to be coated bein~ screened b~ means of a
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L 1374~3~2
PHN 8262
template. The glass powder may alternatively be provided
: to means of a silk-screening process, by settling (deposit-
ing in a bath) or by securing the glass powder against the
metal plate by means of a tape comprising glass powder.
It is alternatively possible to provide glass in foil form
and to heat the plates with the intermediate foi1 so that
~ adhesion of the glass to the plate occurs. After removing
- the material of the strip-shaped regions, the excessive
glass is removed, for example, by etching or powder blast-
ing.
Figure 8 shows diagrammatically a par-
ticularly suitable method of providing the glass powder 18,
namely el~ectrophoretic coating. An electrophoresis bath
21 contains a liquid, preferably an alcohol 23 (for example
methanol) in which glass powder 18 is suspended. Two
electrodes 22 and 24 are in the bath. Electrode 24 is
formed by a ridged plate which comprises a relief and is to
be coated with glass powder 18. The glass particles are
changed electrically in that ions of a suitable electrolyte
present in the bath adhere to the glass particles. Depen-
dent on the positive or negative charge, a given voltage is
applied between the electrodes 22 and 24 so that the glass
particles 18 will move towards the electrode 24. The
parts not to be coated are covered with a layer of suitable
insulator 199 for example, methacrylate resin, polyimide,
beeswax or paraffin. With a voltage between the electrodes
22 and ~4 of approximately 100 volts and a distance between
the electrodes of 1 cm, a layer of glass powder 18~ thick-
ness approximately 60 /um, would be deposited on an elec-
trode surface of 10 sq. cm in 90 seconds.
By etching away3 dissolvdng, evaporating
or removing the insulator 19 in a different manner and con-
verting the glass powder into solid glass by heating, a
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PHN 8262
ridged plate is obtained which comprises a re1ief and has a
layer of solid glass on the ridges. Such a plate may then
be placed against an apertured plate or a~ainst another plate
comprising a relief, as has been described above. When the
insulator 19 is a polyimide, it can be rleadily dissolved in
a solution of approximately 10 normal solution lye, prefer-
ably KOH, or in N2H4. H20 (hydrazine hydrate).
In Figure 9, two plates comprising a relief
and coated with glass in the above-described manner are
provided one on top of the other. The shape of the relief
pattern is approximately equal to that shown in Figure 7a.
The plates are secured together by heating. By removing
the strip-shaped regions 14, for example by etching, the
grid is obtained as is shown in Figure 10. It is alter-
natively possible to secure the plates together with the
ridges remote from each other instead of, as in Figure 9,
with the ridges facin~seach other. In that case the glass
powder should be provided on the surfaces 25 not comprising
a relief, may also be done non-electrophotoretically.
The securing together o~ the plates when
glass is used as an insulator will as a rule be carried out
at elevated temperature. Dependent on the kind of glass and
the material oF the plates used, this will be done in a
reducing or oxidizing atmosphere. In order to contact the
reducing or oxidizing atmosphere with the insulator material
it is recommendable to provide the plate(s) with a number
of apertures 26 as is shown in Figure 11. Said apertures 26
are also desired when a synthetlc foil wetted with an
adhesive is used as an insulator, but in this case they are
desired for causing any gases formed during heating to flow
away. Said gases occur notably when a foil is used of
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PHN 8262
a polyimide of 4--4' diaminodiphenyl ether and 1, 2, 4, 5
benzenetetracarbonic acid dianhydride which is wetted with
a solution of a polyimide of the same materials, in which
gases are formed during polymerisation in which the poly-
amide is converted into the polyimide.
After folding the plates together they may
not contact each other. For that purpose, during assembly
so-called suction plates may be used the operation of which
will be explained with reference to Figure 14. It consists
of a stain1ess steel plate 34 of a fen cms thickness which
.. has been made tension free and has the correct shape and
flatness within the desired accuracy. The suction plate
comprises a number o~ slots 35 which can be made to communi-
cate with a vacuum line 36 via a duct. The plates secured
one on top of the other are sucked on such suction plates
and provided on each other at the desired distance, with
. . .
the interposition of the insulator 15, and heated to a ..
temperature which is sufficiently high for the insulation
material so that the adhesion is produced. ...
As shown in Figures 12 and 13 in two parts of :
sectional views through two plates 27 and 28 comprising a
relief and secured together at an angle of 90, the correct
distance can also be obtained by using spacing elements
between said plates in the form of a sphere 29 or a rod 30,
rPspectively, which spheres or rods are removed together
with the strip shaped regions.
Figure 15a is a sectional view of a part of
a plate having a relief pattern which consists at least at
surface of aluminium. By anodizing the parts 31 of the
: 3~ ridges 13 consisting of aluminium at least at the surface,
said aluminium is converted at that area into an A1203
layer 31 which, as is known, is an insulator. Another plate
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~LO 7 ~3~jZ PHN 8262
32 is secured against the anodized layers and the strip-shaped
regions are removed again (Figure 15c). Said plate 32 may
also be a plate having a relief pattern or may be an apertured
plate. In order to ensure the screening of the electron beams
from the earth's magnetic field, at least one of the plates of
the colour selection means 7 preferably consists of a ferro-
magnetic material, for example Fe, Co, Ni or alloys of or with
said metals.
Figures 16a and b show a part of colour selection
means which comprise a plate 33 having apertures 9. A plate
having a relief is secured against said plate by means of an
insulator 15 so that the ridges 13 become situated between the ~ .
apertures 9. By removing the strip-shaped regions 14 the .
colour selection means as shown in Figure 16a are obtained.
The operation thereof is shown in Figure 16b. The three
phosphor strips associated with the aperture 9 are shown on
the display screen 6 in the same manner as in Figure 5b.
; The conductive strips 17 are connected together and are at a
lower potential~than the plate 33 so that the desired
. 20 quadrupole lens is formed in the aperture as a result of which
the electron beam is displayed as a spot 10. .
A display screen for a tube according to the in-
vention can be manu~actured by means of a known exposure
method in which the colour selection means are displayed on
~S a photosensitive layer on a window portion of the tube. Small
variations in the distance between the conduc~ive strips of
set 16 cause defects in the width of the phosphor strips. ~ .
The method according to the invention prevents such variations
in that during the manufacture of the colour selection rneans
the distance between the conductive strips (ridges 13) is ~.
fixed by the strip-shaped regions 14.
. In connection with the great transrnission of the .
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,5zl
PHN 8262
colour selection means according to the invention, the
exposure method used should be suitable to display the aper-
ture 9 in a conslderably narrowed manner to get the phosphor
strips with the right width. An exposure method suitable
for this purpose uses two or more light sources at some
distance from each other, as described in German patent
application 2,2~8,878 by Sony and published on April 19,
1973. Of course, a tube according to the invention is also
excellently suitable for so-called electronic exposure in
which the sensitive layer on the window portion is
"exposed" by means of an electron beam.
It will be obvious that constructions in which
more than two plates are secured together with the inter-
position of an insulator also fall within the scope of the
present invention. According to the method of the invention,
for example, not one plate but two plates having a relief
pattern may be secured against a plate having apertures 33
as shown in Figure 16a, so that a set of parallel strips is
formed on two sides of the apertured plate. Very symmetrical
quadrupole lenses can be obtained with such a construction.
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