JPS58140955A - Projection television receiver - Google Patents

Abstract

PURPOSE:To facilitate the positional adjustment of an electromagnetic focusing coil by providing a control electrode adjacently to the second grid of a three- pole part which constitues an electron gun, and enabling two different voltages to be supplied to said control electrode alternately. CONSTITUTION:A control electrode 12 is added to the three-pole part of a projection cathode-ray tube 1 which consists of a cathode 4, the first grid 5 and the second grid 6 so as to enable two different power sources 13 and 14 to be connected to the control electrode 12 through a change-over switch 15. After a picture image is projected upon a fluorescent screen 10 by focusing and deflecting electron beams by means of an electromagnetic focusing coil 8 and a deflecting coil 9, the projected image is magnified with a lens system 2, and the magnified image is projected upon a screen 3. As a result, the spread of the electron beams can be suppressed by the profocus lens effect. In addition, the position of the focusing coil 8 can be exceptionally easily adjusted by clarifying the position of the reference electron beam by applying a low voltage to the control electrode 12 during the adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called projection television receiver that projects television images onto a cathode ray tube and enlarges and projects the images onto a screen using a lens or the like.
This invention relates to a device that uses electromagnetic focusing coils (or permanent magnets), which are often used in fields where image resolution is required, for focusing electron beams.

Figure 1 shows the principle of a conventional projection television receiver using an electromagnetic focusing coil.

Here, 1 is a projection tube, 2 is a projection lens system, and 3 is a screen. The three-pole portion of the projection tube 1 is composed of a cathode 4, a first grid 5, and a second grid 6, and the electron beam accelerated by the anode 7 is focused by an electromagnetic focusing coil 8, deflected by a deflection coil 9, and projected. An image is projected onto the fluorescent surface 1o of the tube 1. The image on the fluorescent surface 10 of the projection tube 1 is enlarged and projected by a projection lens system 2, and the projected image is displayed on a screen 3.

FIG. 2 shows the focused state of the electron beam inside the projection tube 1.
It is an explanatory view showing an enlarged extreme part. The trajectory of the central part of the electron beam 11 emitted from the cathode 4 is shown by a dotted line.
The trajectory of the peripheral part of the electron beam is shown by a solid line.

The electron beam 11 emitted from the cathode 4 is directed to the first grid 5
(e.g. Ov) and second grid 6 (e.g. 600V)
The most focused part of the electron beam, the so-called crossover, is created. Generally, this crossover point is set so that the main lens (for example, the fluorescent surface 1o of the photographic tube 1) aligns the fish to be collected.

An electron beam spot is formed on the fluorescent surface 10.

However, as can be seen from Fig. 2, the center of the cathode 4 is the crossover point of the electron beam (trajectory indicated by the dotted line) emitted from the vicinity, and the crossover point of the electron beam (drawn by the solid line) emitted from the periphery of the cathode 4. In general, the cross-over point of the trajectory shown in FIG. Therefore, in such a conventional lens, the adjustment method for the electromagnetic focusing coil 8 corresponding to the main lens is complicated, and therefore requires a lot of adjustment time.

The reason for this is that since the projection tube 1 and the electromagnetic focusing coil 8 are manufactured separately, the position of the electromagnetic focusing coil 8 that is most suitable for the electron beam 11 in the projection tube 1 is not clear. This means that the position of the electron beam 11 inside the projection tube 1 is 3.
This is because the inclination and eccentricity within the projection tube 1 of the electron gun constituted by the pole portions vary, and the electromagnetic focusing coil 8 must be adjusted to the optimum position accordingly.

What is the most suitable installation state for the electromagnetic focusing coil 8?

With the center of the electron beam 11 and the center of the electromagnetic focusing coil 8 coinciding, only the focusing effect works in this case. If this center shifts, not only a focusing effect but also a deflecting effect will be added.
The center of one screen will be shifted. As an adjustment method using this principle, an alternating current is superimposed on the electromagnetic focusing coil 8 so that the focusing action and the deflection action can be clearly distinguished.

That is, the position K of the electromagnetic focusing coil 8 may be adjusted while moving the position of the electromagnetic focusing coil 8 to the position where the deflection effect of the alternating current on the screen disappears (that is, the position where the screen no longer shakes). However, even with this method, there is a problem in that it takes a long time to make the adjustment, and in particular, it is difficult to make the adjustment with high precision.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a projection type television receiver that can solve these conventional problems and allow adjustment of an electromagnetic focusing coil to be performed easily and in a short amount of time.

Hereinafter, five embodiments of the present invention will be described with reference to the drawings.

FIG. 2a shows the configuration of a receiver according to an embodiment of the present invention. Note that the same parts as in FIG. 1 are given the same reference numerals.

What is different from the conventional configuration?

A control electrode 12 is added to the anode side of the second grid 6, and the voltage applied to this new control electrode 12 from the power supplies 3 and 14 can be switched by a changeover switch 15. .

The operation of this control electrode 12 will be explained with reference to FIGS. 4 and 6. FIG. 4 illustrates the locus of the electron beam 11 emitted from the cathode 4, with the locus of the central portion of the electron beam 11 being shown by a dotted line and the locus of the peripheral portion thereof being shown by a solid line. In this example, the voltage of each electrode is OV for the first grid 5, 600 V for the second grid 6, and 80 V for the control electrode 12.
0 to 1 oOov, and the anode 7 is set to 30 kV. Then, the current of the electromagnetic focusing coil 8 is adjusted to form an optimal electron beam on the fluorescent surface 10.
The difference from the one in Figure 2 is that the angle at which the electron beam 11 diverges (the divergence angle) is small.

The diameter of the electron beam 11 is small, and in particular, the peripheral part of the electron beam passes through the center more than in the past. This is because the prefocus lens effect formed by the control electrode 12 and the anode electrode 7 can suppress the spread of the electron beam 11 when it enters the electromagnetic focusing coil 8, which is the main lens. Therefore, the electron beam 11 passes near the center of the inner diameter of the electromagnetic focusing coil 8, and the aberration as a lens becomes a little smaller, and the spot diameter of the electron beam 11 also becomes smaller by /J's.

As a result, a high-resolution image can be projected on a 1° fluorescent surface.

Next, a method of adjusting the position of the electromagnetic focusing coil 8 will be explained. As mentioned above, the ideal position of the electromagnetic focusing coil 8 is when the center axis of the electron beam 11 and the center axis of the magnetic field of the electromagnetic focusing coil 8 coincide. The deflection action by the electromagnetic focusing coil 8 is eliminated, the center of the screen does not move, and the focusing action is performed with the tri aberration being minimized. This means that if you know the position of the spot of the electron beam 11 in a state where it is not deflected by either the focusing coil 8 or the deflection coil 9, you can simply adjust the position of the electromagnetic focusing coil 8 so that the spot is at that position. Become. However, conventionally, if the electromagnetic focusing coil 8 is not operated, the electron beam 11 diverges and does not form a beam spot on the fluorescent surface 10, so the exact position of the electron beam 11 cannot be determined. Ta. It's 1.
If the electromagnetic focusing coil 8 is operated in an unadjusted state, its optimum position is not known, so an unnecessary deflection effect will occur, and the spot position of the electron beam 11 will be moved. , it was not possible to determine the position of the electron beam 11 when there was no deflection effect at all. Therefore, in a single receiver, by switching the switch 16 and applying a low voltage of about 300 V to the control electrode 12, Even if the lens 8 is not operated, a beam spot can be formed on the fluorescent surface 1o, although the kana aberration is large. This state is shown in FIG. This requires a strong electrostatic focusing lens (
A so-called pi-potential lens) is formed, and although the lens is only local and has large aberrations, the position of the electron beam 11 is sufficient to form a beam spot of the size of a stamp on the fluorescent surface 1o. Therefore, the position of the beam spot in this state is recorded in advance by marking it on the fluorescent surface 10 or the screen 3, and then the voltage of the control electrode 12 is switched to the normal level of about 900V using the switch 16. , by running a focusing current through the electromagnetic focusing coil 8 and adjusting the position of the electromagnetic focusing coil 8 so that the position of the beam spot generated at this time matches the position of the beam spot in the above-mentioned state. , adjustment to an ideal position free from the deflection effect of the electromagnetic focusing coil 8 can be easily and simply done in a short time 9,-.

If the beam spot is not located 1° above the phosphor surface or at the center of the screen 3, it is advisable to adjust the direction of the electron beam to the center using an alignment 16 (coil or permanent magnet) in advance. Thereafter, the position can be adjusted in the same way by applying current to the electromagnetic focusing coil 8 as described above.

As described above, according to the present invention, a control electrode is added to the three-pole portion of the projection tube, and two different voltages can be switched and supplied to the control electrode. By applying an appropriate voltage to the electromagnetic focusing coil, it is possible to obtain a projection screen with high resolution.Also, during adjustment, applying a low voltage allows the projection screen to be projected onto the fluorescent surface without the action of the electromagnetic focusing coil. It is possible to form a beam sporatra, so that the position of the reference electron beam can be easily determined, and the position adjustment of the electromagnetic focusing coil can be made very easily and in a short time.

[Brief explanation of drawings]

1o, - Fig. 1 is a side view showing the principle of a conventional example of a projection type television receiver, Fig. 2 is an enlarged sectional view of its main parts, and Fig. 3 is a projection type television according to an embodiment of the present invention. A side view showing the principle of the digital receiver, and FIGS. 4 and 5 are enlarged sectional views of the main parts thereof. 1... Projection tube, 2... Lens system, 3.
...Screen, 4...Cathode, 6.
...First grid, 6...Second grid, 7...Anode, 8...Electromagnetic focusing coil, 9...Deflection coil, 1o... Fluorescent surface. 11... Electron beam, 12... Control electrode, 13°14... Power supply, 16... Switch. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] A projection tube has an electron gun, which includes a triode consisting of a cathode, a first grid electrode, and a second grid electrode, and a control electrode added to a corner of the second grid; It is characterized by comprising an electromagnetic focusing device for focusing, and an adjusting device for adjusting the positional relationship between the projection tube and the electromagnetic focusing device, and a power source capable of supplying two different voltages to the control electrode is connected. A projection television receiver.