NL8902374A - IMAGE DISPLAY DEVICE AND CATHODE BEAM. - Google Patents

Description

T.n.v. N.V. Philips' Incandescent lamp factories in Eindhoven "Image display device and cathode ray tube."

The invention relates to an image display device comprising a cathode ray tube which emits a screen, aside from the screen, means for generating a row of electron beams, each electron beam scanning a column of picture elements from the screen, and deflection means for scanning the electron beams to the screen to bend.

The invention also relates to a cathode ray tube suitable for use in an image display device.

An image display device of the type mentioned in the first paragraph is known from European patent application 0 288 095.

A color image display device is shown therein, in which emitting means are arranged to the side of the screen for generating a row of electron beams. The emitting means contain one (semiconductor) cathode for each electron beam. In operation, the electron beams are emitted at least substantially parallel to the screen. A color selection electrode is placed in front of the screen. A series of deflection strips is placed on a wall parallel to the color selection electrode. The electron beams are in operation between the deflection strips and the color selection electrode. By applying potentials to the deflection strips, it is possible to selectively deflect the electron beams to the screen so that the electron beams scan the screen in a direction transverse to the row of electron beams.

A problem that occurs with such tubes is that the paths of the electron beams can be influenced by magnetic fields. In the above-mentioned European patent application, the space between the deflection strips and the color selection electrode is surrounded by a magnetic screen, of which the color selection electrode forms part.

It is inter alia an object of the invention to provide an image display device of the type mentioned in the first paragraph for which the influence of magnetic fields on the paths of the electron beams is reduced. This makes it possible to omit or reduce the magnetic screen or to make it simpler or lighter.

To this end, the image display device according to the invention is characterized in that the deflection means comprise a first and a second electrode which are disposed at least substantially parallel to each other and between which there is a deflection space, the image display device means for adding a potential difference to these electrodes. and the emitting means are adapted to cause the electron beams to enter the deflection space at an acute angle to the parallel electrodes.

As will be made clear below, due to the symmetry of the parabolic paths that the electron beams travel in the deflection space, the influence of magnetic fields on the paths of the electron beams is greatly reduced and in some cases easy to compensate.

An embodiment of an image display device according to the invention, wherein the image display device is provided with a color selection electrode extending in front of the screen, is characterized in that one of said electrodes contains the color selection electrode and the emitting means are suitable for emitting a row of electron beam impellers and said angle is about 45 °.

At an angle of about 45 °, electron beams having the same kinetic energy and subject to the same electric field in the deflection space cross each other after traversing the deflection space in a first order approximation at the color selection electrode. Second order deviations from this can be easily corrected, either by a small difference in the kinetic energies of the electron beams, or by a small difference in the electric fields to which the electron beams are subjected, or by a combination of these measures. This allows a simplification of the image display device and reduces the influence of magnetic fields.

A further embodiment of the image display device according to the invention is characterized in that the emitting means are designed in such a way that the angles at which the electron beams enter the deflection space in the fans are symmetrical with respect to an angle of 45 °.

This makes it possible to further simplify the image display device.

A further embodiment of the image display device according to the invention is characterized in that the emitting means are suitable for simultaneously generating at least two of the fan-forming electron beams.

A color image can be constructed from successive images in the primary colors or from simultaneous images. For this purpose, the electron beams that form the impeller can be generated sequentially or simultaneously. Simultaneous display of images in the primary colors has the advantage that lower frequencies can be used to drive the emitting means and / or to supply the potential difference to the electrodes. Since only small differences have to be made in the kinetic energies, the image display device according to the invention is particularly suitable for this. Preferably, the emitting means are suitable for simultaneously emitting all the fan-shaped electron beams.

A still further embodiment of the image display device according to the invention is characterized in that the emitting means are suitable for generating electron beams, the energies of the electron beams differing so much from one another that the electron beams mutually differ at a given potential difference between said electrodes in the plane of cross the color selection electrode.

Yet a further embodiment of the image display device according to the invention is characterized in that the emitting means are provided with deflection electrodes.

The angle at which an electron beam enters the deflection space and the energy of the electron beam can easily be influenced by means of deflection electrodes.

A further embodiment of the image display device according to the invention is characterized in that the electrodes are approximately rectangular and the distance between the electrodes is more than 1/4 the length of the electrodes when viewed in the direction of travel of the electron beams.

If the length ratio mentioned above is less than 1 / 4th, then it is not possible to make full use of the deflection space extending between the electrodes without an electron beam hitting an electrode.

Preferably, the distance between the electrodes is less than 0.40 times the length of the electrodes viewed in the direction of advancement of the electron beams.

A further increase in this distance means that a larger potential difference must be applied between the electrodes.

In a preferred embodiment of the image display device according to the invention, the length of the electrodes viewed in the direction of travel of the electron beams is smaller than the length viewed in a direction transverse to said direction.

This makes it possible to make the image display device relatively shallow and reduces the influence of magnetic fields.

A further preferred embodiment of the image display device according to the invention is characterized in that the quotient of the length of the electrodes in the direction of advancement of the electron beams and the length of the electrodes in a direction transverse to said direction is less than 3: 4.

Yet a further embodiment of the image display device according to the invention is characterized in that the said quotient is approximately 9:16.

Some embodiments of the image display device according to the invention are now described by way of example with reference to a drawing.

Herein shows

Figure 1 shows the known color image display device in cross section;

Figure 2 shows in section a color image display device according to the invention;

Figure 3 shows a detail of the color image display device shown in figure 2;

Figures 4a and 4b show a further detail of the color image display device shown in Figure 2;

Figure 5 shows a further detail of the color image display device according to the invention;

Figure 6 a deflection space.

The figures are schematic and not drawn to scale, with corresponding parts being generally designated with the same reference numerals in the various embodiments.

Figure 1 shows the known image display device in section. Color image display device 1 comprises in an cathode ray tube 2 an emitting means 3 with which a row of electron beams 4 is emitted in the deflection space 5 between the deflection strips 6 and the color selection electrode 7. At least one electron beam is emitted for each column of picture elements.

In operation, voltages are applied to the deflection strips 6, such that the electron beams initially describe a straight path parallel to the deflection strips 6 and the color selection electrode 7 after entering the deflection space 5. By applying a high voltage to one or more of the deflection strips, the electron beams are forced to deflect through an angle of 90 ° to the color selection electrode.

Magnetic fields cause deviations in the paths of the electron beams. These deviations can be at least partially reduced by containing the deflection space in a magnetic screen.

The color selection electrode in Figure 1 is part of the magnetic screen. Reducing the influence of the magnetic fields on the trajectories of the electron beams can make the magnetic screen simpler or lighter in design, or even omitted. The present invention provides an image display device in which the influence of magnetic fields on the paths of the electron beams is reduced.

Figure 2 shows a cross section of an image display device, in this example a color image display device 20 according to the invention. Color image display device 20 contains in an evacuated envelope 22 emitting means 23 for generating a row of impellers of, in this example three, electron beams 24, 25 and 26. It is noted that these emitting means 23 can be three different sources for the three electron beams or one common source for the three electron beams. The color image display device 20 further includes a deflection space 27 between a color selection electrode 28 and a flat electrode 29. In operation, an electric field E is applied in the deflection space 27 by a potential difference between the color selection electrode 28 and the flat electrode 29. The electron beams 24, 25 and 26 enter the deflection space 27 at an angle to the plane of the color selection electrode, i.e. at an angle α with the field lines of the electric field E. In the deflection space, the electron beams pass through parabolic paths. After traversing the deflection space, the electron beams 24, 25 and 26 pass through openings in the color selection electrode 28, diverge in the space between the color selection electrode 28 and a display 30 and strike the display 30.

The influence of the magnetic fields on the trajectories of the electron beams is given by the force Fg that the magnetic fields exert on the electrons in the electron beams. This power is given by

Fg = BXv, where B is the magnetic field and v is the velocity of the electrons and X is the vector product of B and v.

The electrons move in the plane of the drawing. The z-component of the velocity of the electrons, where z is the direction perpendicular to the plane of the drawing, is therefore 0. The x-component of the velocity of the electrons, where x is the horizontal direction, is a constant νχ. The y component of the velocity of the electrons varies between an initial value VyQ when entering the deflection space and a final value -VyQ. The magnetic field in the deflection space has components Βχ, By and Bz in the x, y and z directions, respectively. The resulting forces on the electrons in the x, y and z directions Fx, Fy and Fz are:

Fx = -vy®z Fy = -vxBz Fz = Bxvy-vxBy

The influence of forces or components of forces related to the velocity in the y direction (Fx and Bxvy) on the location where the electron beams strike the color selection electrode and on the angle at which the electron beams strike the color selection electrode is zero, since each effect of such a force on the first part of the electron orbit, i.e. up to the extremity of the electron orbit, is compensated by an opposite effect on the second part of the electron orbits.

FyI, the force in the y direction, is a constant and easily compensated by an extra constant potential difference between electrodes 28 and 29. Because the effect of Fv is zero and F ,, compensate, making the effect of Fy zero , the angle at which the electron beams strike the color selection electrode is not affected. Thus, only one component of the force in the z-direction Fz is important and this component also has a constant value and is therefore relatively easy to compensate. A magnetic screen, if present, therefore has to shield only one component of the magnetic field if desired.

In the known image display device, the influence of Fx and Βχν ^ is not zero since in the deflection space Vy varies from zero to a maximum value, and νχ is not constant but varies where the electron beams are deflected to the screen. Fv and F en therefore influence the angle with which the electron beams strike the color selection electrode. This results in color errors.

Furthermore, it is important that in the known image display device the electron beam is deflected towards the screen in a very small area in which large gradients occur in the deflection field. Calculations have shown that small deviations, due to the influence of the magnetic field, at the place where the electron beam enters the area where the electron beam is deflected to the screen, result in large deviations at the place where the electron beam hits the screen. Since the deflection field does not show gradients, the image display device according to the invention is much less sensitive to this effect. It is noted that part of the present invention is that the deflection space is used in combination with emitting means that emit a row of electron beams. The electron beams enter the deflection space almost directly from the emitting means. They do not first go through another deflection space to be deflected in a transverse direction (the z direction). Such an arrangement would largely nullify the intended effect.

In Figure 2, which shows a preferred embodiment of the image display device according to the invention, the angle with which the electron beams enter the deflection space is approximately 45 °. This angle α is 45 ° for electron beam 5. For the electron beams 4 and 6, the angle is 45 ° - δ and 45 ° + δ, respectively. After traversing parabolic orbits, the electron beams pass through the color selection electrode 8 and strike a display screen 10. δ, the angle that electron beams 4 and 6 make with electron beam 5 is generally small, on the order of a few tenths to a few degrees.

Figure 3 shows a detail of the color image display device shown in figure 2. Of the electron beams 24, 25 and 26, in figure 3 only electron beam 25 is shown. Electron beam 25 has a speed Vq, where Vq is proportional to the kinetic energy Ε ^ η of the electrons. The velocity in a direction perpendicular to the plane of the color selection electrode is Vyg = VQCOs (or); the velocity in a direction parallel to the plane of the color selection electrode is vxq - VQsin (a). In the deflection space, the electron beams experience an acceleration a directed from the flat electrode 29 to the color selection electrode 28. This acceleration is directly proportional to the field strength of the electric field E.

The distance in the direction parallel to the plane of the color selection Sx that an electron beam travels in the deflection space 27 is:

Sx = 2 * VQ / a * sin (a) cos (a) = constant * sin (2a)

Sy, the distance the electron beam travels in a direction transverse to the electrodes is given by:

Sy = 1/2 * VQ / a * sin2 (a)

Development of sin (2tr) to 45 ° (= π / 4 radians) gives (a expressed in radians): 9 sin (2cr) = 1 - 2 * (π / 4 - or) + higher order terms

This formula shows that for an angle of 45 ° in the first order approximation, the distance Sx for all three electron beams 24, 25 and 26 is equal if the electron beams 24, 25 and 26 have the same energy and are subject to the same electric field in the deflection space to be.

In second order approximation, there is a small difference Δ between the place where beam 25 passes through the color selection electrode and the place where beams 24 and 26 pass through the color selection electrode. For bundle 25: sx25 ~ constant

For bundles 24 and 26:

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Sx24 26 = constant * (1 - 25),

It follows: Δ = Sx25 "Sx24.26 = δχ25 * 2 * δ2

An estimate of δ and thus of Δ can be made for a certain type of pipe using figure 4a. The electron beams 24, 25 and 26 intersect at the location of the color selection electrode 28. Then the electron beams diverge, in this example along straight lines.

The distance D between the spots of the electron beams on the display is D = 2 * 0 ^ 5 where D ^ is the distance between the color selection electrode and the display.

For example, if D ^ is 1 centimeter and the distance D is equal to the distance between phosphors on the screen (= 250 pm), then δ is 1/80 radial (= 0.7 °) and Δ is then Sxg * 3.124 * 10- ^. Δ is small and not shown in Figure 4a, but in some circumstances it is recommended to correct this difference. For a color image display device in which the display has a dimension of about 50 cm, Δ ranges from about 0 µm at one edge of the display to about 156 µm at an opposite edge, which is approximately equal to half the distance between phosphors on the screen. As the screen gets bigger, Δ increases.

The difference Δ is smaller if, for example, the electron beams are located at a distance from each other at the point where the electron beams enter the deflection space. In the above example, when the electron beams 24 and 26 enter the deflection space 78 µm from the electron beam 25, Δ across the display varies between about -78 µm and +78 µm, resulting in improved image display.

The difference Δ is smaller, and can even be fully compensated, if the constant given above for the electron beams 24 and 26 is a factor of 1 + 25 greater than the constant for the electron beam 25, for example if the electron beams 24 and 26 have the kinetic

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energy Ε ^ η a factor of 1 + 25 greater or the electric field strength is a factor of 1 + 25 weaker than for electron beam 25.

Figure 4a shows an arrangement in which the electrons follow a straight path between electrode 28 and the screen 30. It is also possible that a potential difference is applied between the electrode and the display so that the electrons are accelerated after they have passed through the color selection electrode 28. A so-called accelerator tube has the advantages that a relatively low voltage has to be applied between the electrodes 28 and 29 and that the heat supply by the electrons to the color selection electrode is smaller. Distortions of the color selection electrode as a result of temperature differences then occur less. Figure 4b shows a detail of such a color image display device. Because the electron beams are accelerated, they diverge less in the space between the color selection electrode 28 and the display 30 for a given angle 5. However, the distance between the electron beams on the display should be equal to D, the distance between the phosphors. Therefore, the angle 5 between the electron beams is larger, approximately a factor of 3 to 5. As a result, Δ increases approximately by a factor of 10 to 20. These factors and the values for D ^, D, 5 and Δ are only given here as an example and should not be considered limiting.

Figure 5 shows an arrangement with which the energy of the electron beams 24 and 26 can be increased in a simple manner and the angle with which the electron beams enter the deflection space can be influenced. The electron gun 40 contains an electron-emitting element 41, for example a p-n emitter, a set of electrodes 42, 43, 44, 45 and 46, which accelerate, deflect and focus an electron beam 47 emitted by the element 41. An electron beam 47 has a velocity v0, i.e. an energy Eq, when it leaves aperture 48. Behind aperture 48 are deflection electrodes 49 and 50, which are at the same voltage as aperture 48 for a period of time. The electron beam is then not deflected by the deflection electrodes. After leaving the electron gun 40, the electron beam 47 enters the deflection space, which deflection space is not shown in Figure 5. A potential difference is applied between electrodes 49 and 50 for a subsequent period. The electric field generated by this accelerates the electrodes in a direction transverse to the direction of travel of the electron beam. The electrons of electron beam 47a deflected at an angle δ have a kinetic 2 energy Eq * (1 + δ), if the electrons between aperture 48 and electrodes 49.50 are not accelerated. Furthermore, by applying a small potential difference of approximately Eq * (1 + δ) between the opening 48 and the electrodes 49.50, the kinetic energy can easily be increased by a further factor of 1 + δ. The following example shows that small potential differences between the electrodes suffice for this:

The acceleration a of the electrons in a direction transverse to the direction of movement between the electrodes 49 and 50 is: a = F / m = eE / m = eV / md (1) where F is the force on the electrons, E is the field strength between the electrodes, d is the distance between the electrodes, m is the mass of an electron and V is the potential difference between the electrodes 49 and 50;

The speed transverse to the direction of movement (here as the T

(transversal) direction defined) Vij. on leaving electrodes 49 and 50: vT = at = al / vQ (2) where t is the time the electrons spend between electrodes 49 and 50, 1 is the length of electrodes 49 and 50 in the direction of the electron beam 47 and Vq the speed of the electrons in the direction of the electron beam 47.

Furthermore holds: vT = δν0 (3) and 1 / 2irvq = eVele] ctron (4) where velelectron is the potential difference between the source from which the electrons came, in this example the element 41, and the average potential of electrodes 49 and 50.

Combination of formulas 1, 2, 3 and 4 gives:

'^ electron * “A

Therefore, for a Vgj ^ tron of about 2 KeV and a δ of about 1/80 radial (0.7 degrees) and a d: 1 ratio of about 1: 1, a potential difference between electrodes 49 and 50 of about 25 Volt appears to suffice . For an accelerator tube for which δ can be about 3 to 5 degrees, a potential difference of the order of 100 to 200 volts is sufficient.

Furthermore, a potential difference of about 0.3 V (or a few Volts for an accelerator tube) can be applied between the opening 48 and the electrodes 49 and 50 for the deflected electron beam 47a.

The energy of the electrons in the deflected electron beams is then a factor of 1 + δ greater than the energy of the non-deflected electron beam. The electron beams then intersect at the location of the color selection electrode.

It is also possible for the deflected electron beams for which the

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energy increased by a factor of 1 + δ, a slightly weaker electric field (weakened by a factor of 1 + δ) is applied in the deflection space. For example, if for the electron beam 47 the potential difference between the flat electrode and the color selection electrode is 1 KV, then for the diffracted electron beam 47a, the potential difference is about 0.15 V (and about 3 to 9 volts for an accelerator tube). It is noted that in all the above cases, the speed of the electrons in the x direction for the electron beams 47 and 47a is equal or nearly equal. As a result, the influence of magnetic fields on the electron beams is at least virtually the same.

In this example, the electron beams 47 and 47a are generated successively. The images in the different primary colors are therefore displayed successively. In an embodiment of the image display device according to the invention, the emitting means are suitable for simultaneously generating at least two of the electron beams of the fan. For example, the emitting means may contain three sources for a range of three electron beams, for example, electron beams 24 and 26 of Figure 2 are generated simultaneously. These electron beams intersect at the location of the color selection electrode 28. It is then possible to display at least two of the images in the primary colors simultaneously without the need for a difference in energies of the electron beams 24 and 26. As a result, the frequency (s) with which the emitting means or the electrodes 28 and 29 are driven is reduced. Preferably, all electron beams are generated simultaneously. They then all pass simultaneously through the deflection space. A further simplification of the color image display device is then possible. Corrections at the place where the electron beams pass through the color selection electrode can be effected by, for example, giving electron beam 25 a slightly lower energy compared to electron beams 24 and 26 or the place where electron beam 25 enters the deflection space relative to the place where electron beams 24 and 26 to enter the deflection space. The example given above can be compared with an image display device according to the invention in which the angle α is 20 °.

The distance traveled Sx for electron beam 25 is then:

Sx = constant * sin (2 * 20 °) = constant * sin (40 °) for electron beam 24:

Sx = constant * sin (40 ° + 26) constant * (sin (40 °) + 2 * cos (40 °) * 5) and for electron beam 26:

Sx = constant * (sin (40 °) - 2 * cos (40 °) * 5)

The electron beams, provided that the electron beams have the same energy and are subject to the same electric field in the deflection space, will not intersect at the location of the color selection electrode, the distance between the outer electron beams 24 and 26 is approximately 2 * 2 * cot (40 °) * ö * Sx. If Sx as in the above calculation example is 50 cm and δ is about 1/80 radial, then this distance is about 2 cm. This is approximately a factor of 100 more than 156 µm as followed from the example given above. Therefore, if one wants to correct these deviations, either an approximately 100 times greater potential difference between the opening 48 and the electrodes 49 and 50 must be applied, or an approximately 100 times greater variation of the potential difference between the flat electrode 29 and the color selection electrode. 28 than shown above. However, such large potential differences have a number of drawbacks. A large potential difference between the opening 48 and electrodes 49 and 50 will cause a varying lens field to form between these electrodes, causing differences in the shape of the electron beams, which is undesirable. Moreover, there is a relatively large difference in the energies of the electron beams entering the deflection space. Deviations due to magnetic fields depend on the speed of the electron beams. If the angle is 45 ° then these deviations are approximately the same for all electron beams, because the speeds differ only slightly. If the energy differences are increased, differences in the deviations due to magnetic fields for the different beams occur. It will be clear that this is also undesirable.

It is noted that the idea of allowing the impellers of electron beams to enter the deflection space at an angle of 45 ° and the resulting advantages do not in themselves depend on the way the electron beams are generated or the shape of the emitting means and therefore in generally apply to image display devices in which a range of electron beams is deflected in a deflection space between two planar electrodes.

Likewise, the idea of influencing the energies of the electron beams forming the impeller to intersect at the location of the color selection electrode and the resulting benefits per se does not depend on the way the electron beams are generated or the shape of the electron beam. emitting means and therefore generally for image display devices in which a variety of electron beams enter and deflect at an angle into the deflection space.

Figure 6 schematically shows the deflection space. This is an approximately box-shaped space 60 defined by ribs a, b and c. The ribs a and b approximately correspond to the sides of the electrodes 28 and 29 (Figure 2), the rib c corresponds to the distance between the electrodes 28 and 29. In operation, electron beams 61 run approximately parallel to the rib b on the rib a enter the deflection space. The lengths of the ribs a and c are proportional to 1: x where x is chosen such that the length of the rib c is slightly greater than the maximum distance between the base surface 62 of the box-shaped space 60 and the extremum 63 of an electron path (in Figure 6 indicated by Sy).

For an entrance angle α equal to 45 degrees, the distance Sy mentioned above is approximately equal to 1/4 times the distance traveled parallel to the ground plane 62 (denoted by Sx in Figure 6). If x is less than 1 / 4th it is not possible to make full use of the deflection space. The maximum value for Sx should then be less than the length of rib a. Preferably x does not exceed 0.40. A larger value for x means that the image display device becomes larger and that a larger potential difference must be applied across electrodes 28 and 29. In order to make the image display device as flat as possible, the length of the rib a is preferably less than the length of the rib b. In one embodiment, the ratio of the lengths of the ribs a and b is less than 1: 1,333, for example, 9:16.

For an image display device with an image area of, for example, 45 by 80 cm (and therefore a diagonal of about 1 meter), the length of rib c is about 12 cm. The "depth" of the image display device may then be limited to about 15 to 20 cm. A further advantage is that the influence of disturbing magnetic fields is small. The shorter the distance traveled in the deflection space, the less influence magnetic fields have on the trajectories of the electron beams.

It is noted that the ideas regarding the dimensions of the deflection space and the resulting advantages do not per se depend on the manner in which the electron beams are formed or the number of electron beams or the shape of the emitting means and therefore also for other types of image display devices in which an electron beam entering the deflection space at an angle of about 45 ° and diffracting therein may apply.

It will be clear that many variations are possible for the skilled person within the scope of the invention. For example, the invention is not limited by the shape of the envelope shown here, not limited by the number of electron beams, not limited by any particular embodiment of the emitting means, other than that the emitting means are suitable for emitting a row of electron beams, noting that some of the embodiments underlie ideas which, as noted above, are understood to be applicable per se to other types of image display devices, not limited to an entrance angle of 45 ° unless otherwise stated, and for those embodiments in which the entrance angle is approximately 45 ° is not limited to an embodiment in which the entrance angles are located symmetrically with respect to an angle of 45 °. For example, the number of electron beams can be two, one electron beam making an angle of 45 ° - 5, and one electron beam making an angle of 45 ° + δ with the plane of the color selection electrode. If three electron beams are emitted, the angles that the electron beams make with the plane of the color selection electrode can be 45 ° - δ, 45 ° + δ, and 45 ° + 3δ. Four electron beams can be emitted at angles of 45 ° -25, 45 ° -5, 45 ° + 5, and 45 ° +25. As mentioned above, the electron beams can enter the deflection space at a small distance from each other, or at the same point. The emitting means may contain one source for each electron beam, or a common source for a variety of electron beams.

In the examples given here, the image display device includes a color selection electrode. In other embodiments, the color selection electrode may be absent. The display may then be provided with a conductive layer and the deflection space formed between this conductive layer and the flat electrode 29.

Claims (13)

An image display device comprising a cathode ray tube comprising a screen, side-by-screen emitting means for generating a row of electron beams, each electron beam scanning at least one column of picture elements from the screen, and deflection means for deflecting the electron beams to the screen characterized in that the deflection means comprise a first and a second electrode which are arranged substantially parallel to each other and between which there is a deflection space, the image display device comprises means for applying a potential difference to these electrodes and the emitting means are suitable to allow the electron beams to enter the deflection space at an acute angle to the parallel electrodes. Image display device according to claim 1, wherein the image display device is provided with a color selection electrode extending in front of the screen, characterized in that one of said electrodes contains the color selection electrode and the emitting means are suitable for emitting of a row of electron beam impellers and said angle is about 45 °. Image display device according to claim 2, characterized in that the emitting means are designed such that the angles at which the electron beams enter the deflection space in the impellers are symmetrical with respect to an angle of 45 °. Image display device according to claim 2 or 3, characterized in that the emitting means are suitable for simultaneously generating at least two of the fan-forming electron beams. Image display device according to claim 4, characterized in that the emitting means are suitable for simultaneously emitting all the fan-forming electron beams. Image display device according to claim 2, 3, 4 or 5, characterized in that the emitting means are suitable for generating electron beams, the energies of the electron beams differing so much that the electron beams mutually differ at a given potential difference between said cross electrodes in the plane of the color selection electrode. Image display device according to claim 2, 3, 4, 5 or 6, characterized in that the emitting means are provided with deflection electrodes. Image display device according to any one of the preceding claims, characterized in that the electrodes are approximately rectangular and the distance between the electrodes is more than 1/4 the length of the electrodes when viewed in the direction of travel of the electron beams. Image display device according to claim 8, characterized in that the distance between the electrodes is less than 0.40 times the length of the electrodes when viewed in the direction of travel of the electron beams. Image display device according to any one of the preceding claims, characterized in that the length of the electrodes viewed in the direction of advancement of the electron beams is less than the length viewed in a direction transverse to said direction. Image display device according to claim 10, characterized in that the quotient of the length of the electrodes in the direction of travel of the electron beams and the length of the electrodes in a direction transverse to said direction is less than 3: 4. Image display device according to claim 11, characterized in that said quotient is approximately 9:16. Cathode ray tube suitable for use in an image display device according to one of the preceding claims.