This invention relates to a display device comprising a cathode ray tube, the cathode ray tube having an electron gun comprising a pre-focusing lens portion, for generating a pre-focusing lens field, and a main lens portion, for generating a main lens field.
This invention also relates to a cathode ray tube and an electron gun for use in such a display device.
A display device as described above in the opening paragraph is for example disclosed in the patent document WO 02/45120. This document essentially discloses a display device having an electron gun, comprising a pre-focusing lens portion, for generating a pre-focusing lens field, and a main lens portion, having means for generating a main lens field.
However, recently there has been an increasing demand for slim or even super-slim cathode ray tubes. In order to achieve this, shorter electron guns are desired. One way of achieving a shorter electron gun is to increase the strength of the main lens. However, in order to achieve this, a lower potential Vfoc needs to be applied to the main lens, which may be disadvantageous. Also, in many cathode ray rube concepts, a regulated astigmatism (high or low) is desired, commonly resulting in complex mechanical constructions. An example of this is disclosed in
Hence, it is an object of this invention to provide a display device having a relatively short electron gun, which may be utilized either to make the display slimmer or to reduce the deflection angle realizing the same depth.
An alternative object is to provide a display device having an electron gun with a tunable astigmatism, so that an electron gun may be achieved, having either comparatively high or low astigmatism.
Yet another object of this invention is to provide a display device with an electron gun having a mechanically simple construction.
The above and other objects are at least in part achieved by the display device according to the invention as defined in claim 1. The invention is based on the realization that a potentially shorter gun with a tunable astigmatism may be achieved by adding an additional lens close to the main lens, and in that way obtain an effective lens with higher strength than the main lens.
This is achieved by a display device by way of introduction, being characterized in that the electron gun further comprises an additional grid, being positioned in proximity with said main lens portion, whereby a potential Vgx is arranged to be applied to said additional grid, for generating, together with one of the potentials Vfoc or Vdyn, an additional lens field in proximity with said main lens field, whereby, in operation, the main lens field and the additional lens field is arranged to cooperate to form an effective main lens field.
The potentials Vfoc and Vdyn are understood to be electric potentials applied to an electrode of the main lens portion, said potentials defining the main lens field in cooperation with at least an anode voltage Va. In case the electron gun is a non-DAF gun, a static electric potential Vfoc is applied to the electrode of the main lens portion, whereas in the case of a DAF-type electron gun a dynamic electric potential Vdyn is applied.
By using a simple grid insert in the electron gun, a wide range of astigmatism may be achieved, using a simple mechanical construction. Moreover, as the additional lens field will cooperate with the main lens field, an efficient main lens field will be achieved being stronger than the main lens itself. Thereby a shorter gun may be realized, still avoiding the drawback of applying a lower Vfoc to a main lens grid and according to the invention, a conventional main lens may be used.
Preferably, said pro-focusing lens portion comprises a first electrode and a second electrode, whereby the potential Vgx applied to said additional grid is equal to the potential Vg2 applied to said second electrode, the potential Vg2 being in the range of 350-1500 V, preferably about 700 V. Thereby, a potentially short gun with a tunable astigmatism, may be realized using a commonly used, readily available voltage.
In a preferred embodiment, a so-called bleeder gun has a main lens portion that comprises a distributed composed field lens. In such a gun, the main lens portion comprises at least three electrodes, and the main lens field is also defined by an electric potential Vgi applied to an intermediate electrode of said at least three electrodes.
In this case, preferably, the potential Vgx applied to said additional grid is equal to the potential Vgi applied to the intermediate grid of the distributed composed field lens, wherein Vgi is within the range of 40% to 60% of the potential Va. Preferably, Vgi has a value of about 50% of the potential Va, being the anode voltage. Also in this case, a potentially short gun with a tunable astigmatism, may be realized using a commonly used, readily available voltage in the electron gun.
Suitably, the additional lens field generated by the additional grid is arranged to be an astigmatic lens field. The strength of the additional lens in the horizontal direction and the amount of astigmatism may be designed independently. Moreover, said electron gun further suitably comprises a dynamic astigmatism and focus portion, and said additional grid is arranged between the dynamic astigmatism and focus portion and the main lens portion. Alteratively, said electron gun further comprises a dynamic astigmatism and focus portion, and said additional grid is arranged between the dynamic astigmatism and focus portion and the pre-focussing lens portion, in close profanity with the dynamic astigmatism and focus portion. Preferably, the electron gun also comprises a dynamic beam forming section.
The above and other objects of the invention is at least in part achieved by a cathode ray tube device for use in a display device as described above and by an electron gun for use in a device as described above.
These and other aspects of the invention will be apparent from and elucidated by way of non-limiting examples with reference to the drawings and the embodiments of the invention hereinafter described.
In the drawings:
a is a schematic view of the basic concept for a non-DAF electron gun with a CFL main lens, in accordance with prior art, while
a is a schematic view of the basic concept for a DAF-DBF electron gun with a CFL main lens, in accordance with prior art, while
a is a schematic view of the basic concept for a non-DAF electron gun with a DCFL main lens, in accordance with prior art, while
a is a schematic view of the basic concept for a DAF-DBF electron gun with a DCFL main lens, in accordance with prior art, while
a and 7b is a schematic drawing illustrating the basic principle behind the present invention, where
The basic construction of a prior art display device, with an electron gun, in which the invention may be implemented will hereinafter be described with reference to
A display tube 1, shown in
The electron gun 6 in accordance with the invention will hereinafter be closer described, from the starting point of a prior art non-DAF electron gun, having a CFL main lens as disclosed in for example
In accordance with the invention, three embodiments of which is disclosed in
In the first embodiment (non-DAF gun) disclosed in
In the second embodiment (DAF-DBF gun) disclosed in
In the third embodiment (DAF-DBF gun) disclosed in
Moreover, the invention may also be applied to so called intermediate bleeder guns. Examples of prior art intermediate bleeder guns are disclosed in
In a fourth embodiment (non-DAF gun) disclosed in
In a fifth embodiment (DAF-DBF gun) disclosed in
In a sixth embodiment (DAF-DBF gun) disclosed in
In all of the above-described embodiments of the invention, an additional lens is formed in front of the main lens, as is schematically shown in
The present invention should not be considered as being limited to the above-described embodiments thereof, but rather includes all possible variations covered by the scope defined by the appended claims. Especially it shall be noted that the additional lens is to be positioned in proximity with, or in close proximity with, the main lens. This shall be construed as a positioned being at a comparatively large distance from the pre-focussing section of the electron gun. Moreover, it shall be noted that, it is possible to apply other potentials to the additional grid than the once exemplified above, in order to form the additional lens. For example, the potential applied to the first grid G1 may be used.
It shall also be noted that the term “electron gun” as used in this document shall not be construed in a limiting sense. Especially, it shall be noted that both electron guns generating a single electron beam (in a monochromatic tube) as well as electron guns generating a plurality of electron beams (such as in the color display tube described above), is to be included by this term.
Number | Date | Country | Kind |
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02080367.2 | Dec 2002 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP03/14476 | 12/12/2003 | WO | 1/10/2006 |