JPH02204946A - Cathode-ray tube for video projector - Google Patents

Abstract

PURPOSE:To lessen the dia. of crossover formed by three polar part and enhance the focusing characteristic in the range from low to high brightness by forming No.1 and No.2 grid electrode from magnetic substance, and by using a magnetic field generating means to form an electromagnetic lens in the gap of each electrode mating with an electron beam passage hole. CONSTITUTION:A magnet ring 7 is formed of a ring-shaped permanent magnet surrounding the periphery of a neck part 2 in such an arrangement that the G1 electrode 11b side corresponds the N pole and G2 electrode 12b side to the S pole. The G1 electrode 11b and G2 electrode 12b are both formed from a magnetic substance, so that a path for magnetic flux is formed leading from the N-pole of the magnet ring 7 to its S-pole 7 via the G1 electrode 11b and G2 electrode 12b. This arrangement forms an electromagnetic lens in the gap of the two electrodes 11b, 12b where electron beam passage holes 19, 20 are facing. The effect of this electromagnetic lens will suppress increase in the dia. of crossover produced near the gap between the G1 electrode 11a and G2 electrode 12a.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a cathode ray tube used as a light source tube for a video projector, and particularly relates to a cathode ray tube for a video projector with improved focusing performance at high brightness. .

[Prior Art] Conventionally, as cathode ray tubes for video projectors, electromagnetic focusing type cathode ray tubes with excellent focusing performance have been mainly used. FIG. 3 is an enlarged cross-sectional view of the neck of an electromagnetic focusing cathode ray tube, in which (2) is the neck, and inside this neck (2) there is ) electrode (l1g),
G2 (second grid) electrode (12a), G3
(3rd grid) electrode (13), and cathode (1
An electron gun (lO) consisting of 4) is housed. (4)
is an electromagnetic focus coil that is disposed around the outer periphery of the neck portion (2) and forms an electromagnetic focus lens (18). (8) is an electron beam emitted from an electron gun (lO), and this electron beam (8) is transmitted through an electromagnetic focus lens (!
8) on the cathode ray tube screen (not shown).

Electromagnetic focus cathode ray tubes like this have been used for applications that require high resolution due to their excellent focusing performance, but when used as cathode ray tubes for video projectors, they achieve high brightness. When large current operation is performed to achieve this, a problem has arisen in that the electron beam characteristics of the S pole, which is the electron beam generation source, deteriorate. This will be explained below.

[Problem to be solved by the invention] In a cathode ray tube, large current operation is required in order to obtain high brightness on the screen, but the S pole part (IIg),
(12a), the electron beam extracted from (13) (
8) increases (for example, a current of 5 mA or more),
The size of the crossover (9) near the gap between G1 electrode 1 (lla) and G2 electrode (12a) is
Ia) and G2? [It becomes significantly large due to the aberration and space charge effect of the S-pole lens formed by the beam passage hole with the pole (12a).

The size of this crossover (9) corresponds to the object point diameter when viewed from the electromagnetic focus lens (18), and has a large effect on the image point diameter formed on the screen of the cathode ray tube. Therefore, in order to reduce the diameter of the crossover (9), for example, a G1 electrode (lla) with a small diameter hole through which the electron beam (8) passes has been adopted.

However, if the diameter of the electron beam passage hole is made smaller, the S-pole lens aberration will increase when the amount of electron beam (8) extracted from the cathode (14) increases, and the electromagnetic focus coil ( When focusing with the lens (18) made in 4), the beam diameter at the lens (18) also became large, making it impossible to reduce the diameter of the image spot on the screen when a large current was applied. For this reason, G
There is a limit to reducing the diameter of the electron beam passage hole of one electrode (lla), and a compromise design with the value of the electric trench to be used had to be made. Therefore, the crossover diameter in the low current range becomes large, resulting in deterioration of the video projector's medium to low brightness focus characteristics.

This invention was made to solve the above-mentioned problems, and it provides a cathode ray for video projectors that improves focus characteristics from low brightness to high brightness by reducing the diameter of the crossover formed by the S pole part. The purpose is to provide pipes.

[Means for Solving Problem n] This invention provides a first degree grid electrode and a second grid electrode constituting an electron gun, each formed of a magnetic material, and a gap in which the electron beam passing holes of each of the electrodes face each other. A magnetic field generating means for forming an electromagnetic lens is provided in the part.

As a magnetic field generating means, for example, a magnet ring made of an annular permanent magnet is used, and this magnet ring is connected to a #polar ray tube so that one side of the first grid electrode and the ￥%2 grid electrode is N8i and the other side is the S pole. Place it around the outer circumference of the neck.

[Function] In the cathode ray tube for a video projector of the present invention,
1st. Since the second grid electrodes are all made of magnetic material, a magnetic flux path is formed from the magnetic field generating means to each electrode, and a magnetic lens 'M' is provided in the gap where the electron beam passage hole of the picture electrode faces. It is formed. This one! 3 magnetic lenses
By being superimposed on the electrostatic lens formed by part a, S
The power of the extreme lens is strengthened. As a result, even if the amount of electron beam increases, the effect of the electromagnetic lens allows the first
, the diameter of the crossover between the second grid electrodes is suppressed. Furthermore, the diameter of the electron beam within the main lens of the electromagnetic focus lens is also reduced, and aberrations in the main lens portion are improved.

[Embodiments of the invention] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing a cathode ray tube for a video projector according to an embodiment of the present invention. In the figure, (1)
is a cathode ray tube, and (2) is an electron gun (1) that generates an electron beam.
0), (3) is a stem base part equipped with a lead wire for applying a predetermined voltage to each electrode of the electron gun (lO), and (4) is a stem base part that houses the neck part (2). An electromagnetic focus coil (5) is a deflection yoke for deflecting the electron beam emitted from the electron gun (10).
(6) is a 7' to 13'' class screen coated with phosphor, and (7) is a magnet placed at a predetermined position on the outer periphery of the neck (2) corresponding to the electron gun (10). It's a ring.

FIG. 2 is an enlarged sectional view of the electron gun section in FIG. 1. In FIG. 2, (14) is a cathode coated with an oxide cathode material (15) that emits electrons, and this cathode (14) is heated to about 800° C. by a heater (not shown). (llb) is Gl (first grid) 1! arranged so as to surround the cathode (14). It is extreme.

Conventionally, this Gl electrode (llb) was made of nonmagnetic stainless steel (for example, 5US304), but in this embodiment, it is made of a magnetic material (for example, Fa-Ni 42% alloy).
It is formed of. In addition, the electron beam passage hole (19) of the G1 electrode (llb) is selected to have the minimum dimension value (here, 0.5φ) within the allowable value of the cathode load in order to reduce the crossover diameter created by the S pole. ing.

(12b) is the G2 (second grid) electrode placed opposite to the Gl electrode (llb), and the Gl electrode (11b)
It is made of the same magnetic material. (20) is the electron beam passage hole. On the other hand, G3 (3rd grid)
The electrode (13) is made of the same non-magnetic stainless steel as the conventional one. The G3 electrode (13) has the same high voltage (
For example, 30-35 KV) is applied and the G2 electrode (1
2b) and the G3 electrode (13) a strong electrostatic prefocus lens is formed. This pre-focus lens serves as a front lens of the electromagnetic focus lens formed by the electromagnetic focus coil (4) (see FIG. 1).

By the way, the aperture lens in front of the cathode (14) that occurs near the electron beam passage holes (19) and (20) of both the G1 electrode (ttb) and the G2 @ pole (12b) is connected to the cathode (14) and the Gl electrode (llb ), the voltage applied to each of the G2 electrodes (12b) (for example, 200V, OV, 100OV, respectively) "t' is determined, and the strength of the conoa aperture lens is determined by the solid line (1
It is determined by the magnitude of the curvature of the equipotential lines as shown in 6).

Therefore, the electron beam passing hole (
19), the aperture lens also becomes stronger, and the electron beam (8) emitted from the cathode (14)
As the amount increases, the equipotential line curvature of the aperture lens is small, so it is subject to lens aberration, and the electron beam diameter within the main lens, which becomes the electromagnetic focus lens, increases.

However, the Gl electrode (llb) and the 02 electrode (12b)
) A magnet ring (7), which is a magnetic field generating means, is installed on the outer periphery of the neck part (2) corresponding to the neck part (2). It is intended to be reduced.

That is, the magnet ring (7) is formed of an annular permanent magnet that surrounds the outer periphery of the neck part (2), and the G1 electrode (llb) side is the N pole, and the G2 electrode 8i (12b) side is the S pole.
It is arranged to be a pole. Here, as mentioned above, since both the Gl electrode (llb) and the G2 electrode (12b) are made of magnetic material, the magnet ring (7)
from the N pole to the GIN pole (llb) and the G2 electrode (12b
) is formed to form a magnetic flux path to the south pole of the magnet ring (7). By this, both 'Il poles (llb),
(12b) Electron beam passing holes (19), (20)
An electromagnetic lens is formed in the gap where the two face each other. The distribution of isoelectric lines showing the effect of this electromagnetic lens is
It is shown in the figure by a dotted line (17).

In this way, in the above embodiment, the electromagnetic lens is superimposed in addition to the electrostatic lens formed by the S pole, so the force of the S pole lens becomes stronger, and the electron beam (
8) Even if the amount of
It is possible to suppress an increase in the diameter of the crossover formed near the gap between the 1 electrode (lla) and the 02 electrode 1 (12a).

Therefore, the degree of increase in the crossover diameter is flattened from low brightness to high brightness. Furthermore, it is possible to reduce the electron beam diameter within the main lens of the electromagnetic focus lens, and aberrations in the main lens portion can also be improved.

As a result of the above, it is possible to improve the focusing performance of the video projector from low brightness to high brightness.

In addition, in the above embodiment, an example was shown in which a permanent magnet was used as a magnetic field generating means, but the present invention is not limited to this, and an electromagnet may be used instead of a permanent magnet. .

Further, in the above embodiment, the magnetic field generating means is arranged outside the neck of the cathode ray tube, but it can also be arranged inside the neck.

[Effects of the Invention] As described above, according to the present invention, the first. The second grid electrode is formed of a magnetic material, and the magnetic field generating means forms an electromagnetic lens in the gap where the electron beam passage holes of each electrode face each other, so even if the amount of electron beam increases, the electromagnetic Due to the action of the lens, the diameter of the crossover formed in the gap does not become unnecessarily large, and the diameter of the electron beam in the main lens of the electromagnetic focus lens is also reduced, making it possible to improve aberrations in the main lens. As a result, the focus performance from low brightness to high brightness is improved, and it is possible to provide a cathode ray tube for a video projector that is bright and has excellent focus performance.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a cathode ray tube for a video projector according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of the electron gun section in FIG. 1, and FIG. FIG. 3 is an enlarged sectional view of the neck portion. (1)...Cathode ray tube, (2)...Neck part, (7)
... Magnet ring, (8) ... Electron beam, (10)
...Electron gun, (llb)...G1 electrode, (12
b)...G2 electrode, (19), (20)...electron beam passage hole. In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) Magnetic field generating means for forming the first grid electrode and the second grid electrode constituting the electron gun from a magnetic material, and for forming an electromagnetic lens in the gap where the electron beam passage holes of each electrode face each other. A cathode ray tube for a video projector, characterized in that it is provided with: (2) In the cathode ray tube for a video projector according to claim 1, the magnetic field generating means is constituted by a magnet ring made of an annular permanent magnet, and this magnet ring is connected to the first grid electrode and the second grid electrode. One side is N pole,
A cathode ray tube for a video projector, characterized in that the cathode ray tube is arranged around the neck of the tube so that the other side becomes the south pole.