JPS58172849A - Crt display - Google Patents

Abstract

PURPOSE:To reduce the deflection aberration in the periphery without deteriorating the spot characteristics at the screen center by providing an electron beam in a CRT and by applying a nearly paraboloidal shape signal in synchronism with a deflection signal to a control electrode. CONSTITUTION:A CRT 8 is provided with a heater 1, a cathode 2, the first grid 3, the second grid 4, an anode electrode 5, a focus coil 6, and a control electrode 7 controlling the divergence angle of an electron beam. In addition, it is provided with a deflection yoke 9, a deflection circuit 10 feeding the deflection current to the yoke 9, and a focus circuit 11 feeding the focus current to the coil 6. A synthetic circuit 14 synthesizes a nearly paraboloidal shape signal, and a control circuit 30 generates a signal applied to the electrode 7 together with the circuit 14. Accordingly, a synthetic paraboloidal signal in synchronism with the deflection scan and with a predetermined amplitude is applied to the electrode 7, thus the convergence angle of the electron beam is controlled and the deflection aberration can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-resolution cathode ray tube display device, and an object of the present invention is to provide a device that improves the spot characteristics at the periphery of the screen and achieves even higher resolution.

Cathode ray tube display devices used for computer terminal displays and the like require higher resolution than general NTSC televisions in order to display a large number of characters. For this reason, a cathode ray tube with a small spot diameter of the electron beam is used, but there is a phenomenon in which the beam spot is distorted and the resolution is degraded due to aberrations due to the non-uniformity of the deflection magnetic field distribution at the periphery of the screen, so-called deflection aberrations. This is because a non-uniform magnetic field is intentionally used to correct raster bin cushion distortion and to perform self-convergence in color cathode ray tubes. Further, even if a deflection coil is designed to have a uniform magnetic field distribution, there is a phenomenon in which some non-uniform distribution occurs due to non-uniform winding during manufacturing.

For this reason, it has conventionally been common practice to strengthen the prefocusing section of the electron gun to suppress the divergence angle of the electron beam, thereby reducing the diameter of the electron beam that enters the deflection magnetic field, thereby reducing the deflection aberration. However, this is not an optimal design for the electron beam at the center of the screen, and has the disadvantage that the beam spot diameter at the center becomes large.

There is still a method called quadrupole correction, which attempts to cancel the deflection aberration by distorting the electron beam in advance, but this requires installing a coil in the neck of the cathode ray tube that generates a quadrupole magnetic field synchronized with deflection scanning. Furthermore, a modulator and amplifier to supply signals to the coil are also required, making them extremely expensive.Furthermore, as mentioned above, deflection aberrations due to non-uniformity of the winding of the deflection coil are Since the symmetry varies depending on the location of the screen, the waveform of the signal for driving the four-pole correction coil becomes extremely complex, and it is not easy to generate that waveform.

As described above, conventional devices have drawbacks such as sacrificing the resolution at the center of the screen or making the circuitry complicated and expensive.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a cathode ray tube display device that eliminates such conventional drawbacks.

EMBODIMENT OF THE INVENTION Hereinafter, the present invention will be described in detail with reference to the drawings showing one embodiment thereof. First, a cathode ray tube having electrodes capable of controlling the divergence angle of the electron beam used in this apparatus will be explained with reference to FIG.

FIG. 1 is a sectional view showing only the electron gun section and focusing section of the neck section. In the figure, 1 is a heater, 2 is a cathode, 3 is a first grid, 4 is a second grid, 6 is an anode electrode, 6 is a focusing coil, and 7 is a control electrode for controlling the divergence angle of the electron beam B.

The control electrode 7 forms a prefocus lens with the anode electrode 6, and suppresses the divergence angle of the electron beam B incident on the focus coil 6, which is the main focus lens. Here, if the potential of the control electrode 7 is lowered, the prefocus lens becomes stronger and the divergence angle of the electron beam B is suppressed. Conversely, if the potential of the control electrode 7 is increased, the briss focus lens becomes weaker and the divergence angle of the electron beam B widens.

What is important here is that the cutoff characteristics and drive characteristics of the cathode ray tube are the cathode 2. 1st grid 3. 2nd grid 4
This point is determined by the dimensions and potential of the control electrode 7, and is almost unrelated to the potential of the control electrode 7. In other words, the control electrode 7 changes only the divergence angle of the electron beam B.

Although FIG. 1 describes an electromagnetic focusing cathode ray tube using a focusing coil 6, the control electrode 7 can also be applied to an electrostatic focusing cathode ray tube. In this case, the operation of the control electrode 7 is exactly the same as in the electromagnetic focusing method, except that the brismatic lens is formed between the control electrode and the focusing electrode.

In this device, a cathode ray tube having this control electrode 7 is used,
Near the center of the screen, the strengths of the pre-focus lens and main focus lens are optimized to narrow down the electron beam B, and at the periphery of the screen, the potential of the control electrode is lowered to suppress the divergence angle of the electron beam B. The objective is to realize a cathode ray tube display device with good resolution by reducing deflection aberration.

A specific example of a circuit for performing such an operation will be explained with reference to FIG. In FIG. 2, the same parts as in FIG. 1 are given the same numbers and their explanations will be omitted. In FIG. 2, 8 is a cathode ray tube as described above, 9 is a polarization [hJ yoke, 10 is a deflection circuit that supplies a deflection type FIF to the deflection yoke 9, and 11 is a focus circuit that supplies a focus current to the focus coil 6. be.

12 is a variable resistor that adjusts the DC voltage applied to the second grid electrode. 13 is a variable resistor that adjusts the DC voltage of the control electrode 7. 14 is a synthesis circuit for synthesizing signals having a substantially parabolic waveform applied to the control electrode 7; 15 is a transistor for amplifying the vertical parabolic waveform voltage; 16 is a coupling capacitor; and 17 is a variable resistor for adjusting the amplitude of the vertical parabolic waveform voltage. , 1s coupling capacitor, 19.20i
j is the bias resistance of the transistor 15; 21 is the emitter resistance of the transistor 16; Another transistor 22 of the synthesis circuit 14 is a transistor for amplifying the horizontal parabolic waveform voltage, 23 is a coupling capacitor, 24 is a variable resistor for adjusting the amplitude of the horizontal parabolic waveform voltage, 26 is a coupling capacitor, 26°27 is the bias resistance of the transistor 22, and 28 is the emitter resistance of the transistor 22. 29 is a common collector resistor of the transistors 15 and 22, and a voltage having a waveform obtained by adding the horizontal parabolic waveform voltage and the vertical parabolic waveform voltage is generated in the resistor 29.

30 is a voltage amplification circuit, which together with the synthesis circuit 14 forms a control circuit that generates a signal to be applied to the control electrode 7. Here, 31 is a transistor that operates as an emitter follower, 32 is an emitter resistance of transistor 31, 33 is a coupling capacitor, 34 is a voltage amplification transistor, 35.3
6 is a bias resistance of the transistor 34, 37 is a collector resistance of the transistor 34, and 38 is an emitter resistance of the transistor 34. 39 is a coupling capacitor, and 4o is a coupling transformer, which applies a synthetic parabolic waveform voltage generated on the secondary side of the transformer 4o to the control electrode 7 through the coupling capacitor 41.

With the above configuration, the deflection aberration can be reduced by applying a composite parabolic signal of a predetermined amplitude synchronized with the deflection scanning to the control electrode 7 and controlling the divergence angle of the electron beam B.

FIG. 3 shows an example of the synthesized parabolic waveform.

The optimal value for the maximum amplitude varies depending on the characteristics of the electron gun, the magnitude of the asymmetry component of the magnetic field, the characteristics of the raw focus lens, etc.
300~ for the cathode ray tube 8 and deflection yoke 9 used in the experiment.
It was 400 Vp-p. However, since the impedance of the control electrode 7 is naturally extremely high and only the voltage needs to be amplified, the impedance of the circuit can be set high and the power consumption of the voltage amplification circuit 30 is small.

Furthermore, if the deflection aberration occurs only in either the horizontal or vertical direction, the combining circuit 14 is not necessary, and the voltage amplifying circuit 30 alone can be used.

The above describes an example of the electromagnetic focusing method, but the electromagnetic focusing method has a large aperture of the main focus lens and has little spherical aberration, so it has good spot characteristics, but because it is used with a small lens ratio, the deflection magnetic field is The diameter of the incident electron beam is large, and deflection aberration due to a slight non-uniform deflection magnetic field generated during manufacturing becomes a problem.However, by applying the present invention, deflection aberration can be reduced without sacrificing the center spot characteristics. It is possible to do so, and it has great effects.

Further, the present invention can be applied to an electrostatic focusing method, and in this case, it is particularly effective for a deflection yoke in which the deflection magnetic field has a strong asymmetric component.

As explained above, according to the present invention, it is applicable to both electromagnetic focusing type and electrostatic focusing type, and can deflect the peripheral area without impairing the characteristics of the spot in the center of the screen with a relatively simple configuration. This makes it possible to realize a cathode ray tube display device with high practical value that can reduce aberrations.

[Brief Description of the Drawings] Fig. 1 is an enlarged sectional view of the neck of a cathode ray tube having electrodes for controlling the divergence angle of an electron beam used in a cathode ray tube display device according to an embodiment of the present invention, and Fig. 2 is the same. The specific circuit diagram of the device, Figure 3, shows the electrodes that control the electron beam divergence angle.
FIG. 3 is a waveform diagram of an applied voltage signal. 6... Anode electrode, 6... Focusing coil, 7... Control electrode, 8... Cathode ray tube, 1o
... Deflection circuit, 12.13 ... Variable resistor, 14 ... Synthesis circuit, 3o ... Voltage amplification circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 2

Claims (2)

[Claims] (1) A cathode ray tube including an electrode for controlling the divergence angle of an electron beam and an electron beam focusing means, a deflection yoke attached to the neck of the cathode ray tube, and a deflection circuit that supplies a deflection signal to the deflection yoke. , and a control circuit that applies a signal having a substantially square laboratory waveform to the electrodes in synchronization with the deflection signal. (2) The cathode ray tube display device according to claim 1, characterized in that an electromagnetic focusing device is used as the electron beam focusing means.