JPH0278388A - Electronic display device - Google Patents

Abstract

PURPOSE:To prevent occurrence of a disturbed picture or the like due to an external magnetic field by detecting an external magnetic field at a detector arranged in the vicinity of a vacuum package and applying a signal from the detector to a magnetic field generating coil so as to generate a magnetic field cancelling the external magnetic field. CONSTITUTION:When an external magnetic field HR is generated at the outside of the lower part of a funnel 3 of the vacuum package 1, a detector 12b detecting the field inputs a detection signal proportional to the intensity and direction of the external magnetic field HR to an amplifier 13b, which amplifies the detection signal. The amplified detection signal is applied to one coil 14b for generating the magnetic field, and the coil 14 generates a magnetic field Hc having an intensity and direction to cancel the external magnetic field HR. A residual magnetic field Hr applied to the detector 12b is expressed as Hr= HR.1/(1+G), where G is the gain in the closed loop (magnetic field H detector 12b amplifier 13b coil 14b magnetic field H) and the external magnetic field is reduced to 1/(1+G) clearly in general by the automation control theory.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electronic display device such as a display electron tube used in a television receiver or a display of a computer terminal. Display electron tube (hereinafter referred to as rcRTJ) designed to prevent image disturbance, color shift, or color unevenness caused by magnetic fields
It is related to.

[Prior Art] FIG. 3 is a cross-sectional view showing the main parts of a conventional CRT, as shown in, for example, the Electronic Information and Communication Handbook (edited by the Institute of Electronics, Information and Communication Engineers, published by Ohmsha, 1988 edition).

In the figure, (1) is a vacuum envelope made of glass,
It is formed by a panel face part (2), a funnel part (3), and a neck part (4). (5) is a three-color mosaic fluorescent film of red, green, and blue formed on the inner surface of the panel face (2), and (6) is a shadow mask, which is placed at a predetermined distance from the fluorescent film (5). and is attached to a mounting frame (7) of a similar shape. (8) is an internal conductive film, which is formed on the inner surface of the funnel part (3) by graphite coating.

(9) is a pair of deflection coils attached to the boundary between the neck part (4) and the funnel part (3), and (10) is a tip-shaped anode button. 3), and its inner end face overlaps with and is electrically connected to the internal conductive film (8).

(11) is an electron gun, and the neck part (1) of the vacuum envelope (1) is
4) It is housed within. (16) is the deflection coil (9)
is a deflection signal amplifier connected to the

Since the conventional CRT is configured as described above, a predetermined voltage is applied to each electrode of the electron gun (11), and
2 to the internal conductive film (8) via the anode button (lO).
By applying a high voltage of 0 to 30 KV, thermionic electrons B, which are emitted from the electron gun (11) and accelerated, proceed toward the fluorescent film (5).
) is deflected in a predetermined direction by a deflection coil (9) provided at the boundary between the funnel part (3) and the funnel part (3). For example, in Fig. 3, thermionic electron B at point a is
It is deflected to point b by the energy due to the mutual force H between the energy F given by 1), the charge held by the thermoelectron B, and the magnetic field generated by the deflection coil (9), and collides with the fluorescent film (5). Images such as documents and images can be obtained on this fluorescent film (5).

[Problems to be Solved by the Invention] Since the conventional CRT is configured as described above, when a television receiver using this CRT is installed in a room etc. where indoor power wiring is installed, Image disturbances, color shifts, or color unevenness are likely to occur due to external magnetic fields generated in indoor power wiring or external magnetic fields such as terrestrial magnetism.
1) A magnetic shield is placed inside or outside the device, or a permanent magnet is used to adjust the magnetic field distribution, but in either case, it is sufficient to just shield the external magnetic field or adjust the magnetic field distribution. It was not a good countermeasure.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a CRT that can prevent image disturbance, color shift, color unevenness, etc. caused by external magnetic fields.

[Means for Solving the Problems] A display electron tube according to the present invention includes an external magnetic field detector disposed near a vacuum envelope to detect an external magnetic field, an amplifier for amplifying a detection signal of this detector, and an amplifier for amplifying a detection signal of this detector. The device is characterized in that it includes a magnetic field generating coil that is energized by the amplified detection signal and generates a magnetic field that cancels out an external magnetic field.

[Operation] The external magnetic field detector according to the present invention detects an external magnetic field in the vicinity of the vacuum envelope, and the amplifier amplifies this detection signal. The magnetic field generating coil is energized by this amplified detection signal and generates a magnetic field that cancels out the external magnetic field, so it is possible to prevent image disturbance, color shift, color unevenness, etc. caused by the external magnetic field.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described based on the drawings.

In Fig. 1, (12a) and (12b) are a pair of external magnetic field detectors (hereinafter referred to as "detectors") that detect external magnetic fields.
), these two detections 2'A (12a), (1
2bl is an electric gun (11) installed outside the vacuum envelope (1) near the funnel part (3) of the vacuum envelope (1), that is, inside the neck part (4) of the vacuum envelope (1). The thermoelectron B emitted from and accelerated advances toward the fluorescent film (5).The funnel part (3) surrounds the course from the electron gun (11) to the fluorescent film (5). , are arranged to detect the strength and direction of the vacuum envelope (+1 magnetic field component in the tube axis direction and a 1'' magnetic field component perpendicular to the tube axis).

(+3a), (13bl is a rain detector (12al,
a pair of amplifiers for amplifying the detection signal of (112b);
(11, (14b)' is a rain detector (12al, (1
A pair of coils for generating a magnetic field are placed near the coils t14al and t14bl.
This is energized.

Next, the operation will be explained.

Now, in FIG. 1, an external magnetic field 11. is applied to the outside of the funnel part (3) of the vacuum envelope (1). occurs, one of the detectors T12bl that detects this is exposed to the external magnetic field 11.
Amplifier f13b detects No. 4a proportional to the strength and direction of 8.
) to human power and amplifier! +3bl amplifies this detection signal. This amplified detection signal is applied to one coil (14b) for generating a magnetic field, and the coil (14) generates a magnetic field H1 of strength and direction without canceling the external magnetic field H. Closed loop [Magnetic field 11 → detector (+2bl-amplifier (1
If the amplification degree in the 3bl-coil (+4bl→magnetic field I+) is G, the residual magnetic field H applied to the detector (+2b) is expressed as It,"IL ・I/ (+ +G), and according to automatic control theory It is generally clear that the external magnetic field can be canceled by 1/(++G).

Further, the other detector 8 (12a), amplifier (13a), and coil +14Fl) perform similar operations and have similar effects.

In addition, in the above embodiment, a pair of coils (14
a detector (12a) for each of al, (14bl)
, (12bl and amplifier t13al, (13b
), but a pair of coils (1
A similar effect can be obtained by providing a common detector and amplifier for 4a) and (14b).

FIG. 2 is a sectional view showing C111' of another embodiment of the present invention, where t121 is a detector for detecting an external magnetic field, and this detector (12) is arranged near the funnel part (3). It is configured to detect the strength and direction of the magnetic field component Hx in the direction perpendicular to the tube axis Z of the It empty surrounder 1). (151 is the detection 43 of the detector (12)
The operation of this differential amplifier will be explained next.

Now, assuming that an external magnetic field IIF is generated outside the F part of the funnel part (3) of the empty surroundr (1), the detector (12) detecting this generates the external magnetic field 11. A signal proportional to the strength and direction of Amplify the difference signal.

By applying this amplified difference signal to the deflection coil (9), the magnetic field generated by the deflection coil (9) is
The external magnetic field is corrected, and the accelerated electrons B emitted from the electron gun (11) travel toward the fluorescent film (5) on the same trajectory as when there is no external magnetic field HH.

In addition, in the above embodiment, the case where the pair of deflection coils (9) is provided with the detector (12) and the differential amplifier (15) is explained, but each of the pair of deflection coils (9) is provided with a detector (12) and a differential amplifier (15). A similar effect can be obtained by providing a differential amplifier.

In addition, in each of the above embodiments, an electromagnetic deflection method was described in which the electron beam is deflected by the magnetic field of a deflection coil provided at the neck of the vacuum envelope (1). Similar effects can be obtained even with an electrostatic deflection system in which the electron beam is deflected by the electrostatic field of the deflection plate.

Furthermore, in each of the above embodiments, the display electron tube (CR)
Although the case of T) has been described, it goes without saying that the present invention can also be used in electronic display devices other than CRTs in which image disturbance, color shift, color unevenness, etc. occur due to external magnetic fields.

[Effects of the Invention] As described above, according to the present invention, the coil is placed near the vacuum envelope to detect an external magnetic field, and this detection signal is applied to the magnetic field generating coil to generate a magnetic field that cancels the external magnetic field. This configuration has the effect of providing an electronic display device that can prevent image disturbance, color shift, color unevenness, etc. caused by external magnetic fields.

[Brief explanation of the drawing]

- Fig. 1 is a sectional view showing a display electron tube according to one embodiment of the present invention, Fig. 2 is a sectional view showing a display electron tube according to another embodiment of the invention, and Fig. 3 is a sectional view showing a conventional display electron tube. FIG. (1)...Vacuum envelope, (3)...Funnel part,
(9)--deflection coil, (12), (12a)
, (tzb)--external magnetic field detector, (13a),
(13b)--Amplifier, (14a), (L4b
) - Coil, (15) Differential amplifier. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A detector placed near the funnel part of the vacuum envelope to detect an external magnetic field, an amplifier to amplify the detection signal of this detector, and a magnetic field generating coil to which the amplified detection signal is energized. An electronic display device comprising: a magnetic field generating coil that generates a magnetic field that cancels out the external magnetic field. (2) Equipped with a differential amplifier that uses the deflection signal fed to the deflection coil and the detection signal detected by the external magnetic field detector, and feeds the difference signal to the deflection coil to generate a deflection magnetic field that corrects the external magnetic field. 2. The electronic display device according to claim 1, wherein the electronic display device is configured to allow