JPS593070B2 - TV show - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Some television receivers are of a projection type, in which an image reproduced on a fluorescent surface of a picture tube is projected onto a screen for viewing.

FIG. 1 shows an example of such a projection television receiver. A color video signal from a terminal 1 is supplied to a low-pass filter 2 to extract a luminance signal, and this luminance signal is passed through an amplifier 3 to a matrix circuit 4R to At the same time, the color video signal from the terminal 1 is supplied to the bandpass filter 5 to extract a carrier color signal, and this carrier color signal is supplied to color demodulation circuits 6R to 6B to convert red, green, and blue. The color difference signals are demodulated, and these color difference signals are supplied to matrix circuits 4R to 4BVC.

In this way, from the matrix circuits 4R to 4B, red, green,
The blue primary color signals are taken out and these primary color signals are sent to the amplifier 7.
The red, green, and blue color light images are supplied through the R-TB to the picture tubes 8R to 8B and reproduced, and these color light images are optically combined and projected onto the screen 10 by the lens systems 9R to 9B. The image is reproduced on the screen 10. In this case, the picture tubes 8R to 8B have, for example, 10
As shown in FIG. 2, in an ordinary color picture tube, the phosphor is a monochromatic phosphor, and the electrode for determining the arrival position of the electron beam is removed.

That is, to represent the picture tube 8R for red color, in the example shown in FIG. 3 are provided in the same horizontal plane, and in front of these cathodes 1 to 3, first to fifth grids G1 to G (5 are provided in common, and further grids G
In front of 5, 20 a pair of inner deflection electrodes Cl, C2 and a pair of outer deflection electrodes Cs, C as convergence means.
4 is provided, and the screen Svc is coated with a phosphor that emits red color light. Therefore, a predetermined voltage of 5 VC is supplied to the cathode 1 to 3 and the grid G1 to 25
As a result, a unipotential main electron lens is formed, and the electron beams B1 to B3 emitted from 1 to 3 to the cathode intersect at approximately the center of the main electron lens.
Further, by applying a convergence voltage 30 between the deflection electrodes Cl, C2 and Cs, C4, the electron beams B1 to B3 converge on the screen S.
Emits red colored light. At this time, the red primary color 35 signal is supplied to the cathode from the output emitter follower transistor Q of the amplifier □R through the radiation prevention resistors R1 to R3, and therefore the red primary color signal is supplied to the screen S. A colored light image is reproduced. Similarly, green and blue color images are reproduced in 1ιι frames for the other picture tubes 8G and 8B, respectively.

In this way, even when the picture tubes 8R to 8B each emit monochromatic light, if each of the picture tubes 8R to 8B is made to have multiple beams, the beam current per beam B1 to B3 can be reduced, and therefore, the beam current per beam B1 to B3 can be reduced. Since the diameters of the beams B1 to B3 can be reduced, focus can be improved.

However, in this case, the grid voltage Vgl of grid G1
Cathode current 1k1-I of cathodes K1-K3 for
Since the characteristics of k3 vary as shown by curves A1 to A3 in FIG. 3, the beam currents of beams B1 to B3 vary.

If the beam current varies, the diameters of beams B1 to B3 also vary, and the spot size on the screen S is determined by the beam diameter of the maximum beam current. The focus is determined by the beam and cannot be improved. In view of these points, the present invention aims to improve the focus by eliminating variations in the beam currents of the beams B1 to B3 even if the characteristic curves A1 to A3 vary.

For this reason, in the present invention, as shown in FIG. 4, cathodes K, .about.
Variable resistors VRl to VR3 are connected between K3 and ground.

According to such a configuration, by adjusting the variable resistors VRl to VR3, the AC level and DC level of the video signals supplied to the cathodes K1 to K3 can be changed. The magnitudes of the beam currents can be made to match each other, thus improving focus.

Moreover, the configuration for that purpose is extremely simple, as it only requires following the variable resistors VRl to VR3. In the example shown in FIG. 5, the AC level and DC level of the primary color signals supplied to the cathodes K1 to K3VC can be changed independently.
is supplied to the cathode K1 through.

The transistor Qc is considered to be an emitter follower, and the output impedance seen from the emitter is low.
Further, since VRa is less than VRb, the gain of the transistor Qa is approximately Ra/VRa, and therefore, by adjusting the variable resistor VRa, the AC level of the video signal supplied to the cathode K can be changed. In this case, the emitter potential of the transistor Qc is almost constant, the value of the variable resistor VRa is small, and the voltage between its terminals is small, so even if the variable resistor VRa is changed, the DC level of the primary color signal remains the same.
Almost no change. On the other hand, when variable resistor VRb is changed, the voltage between its terminals must be approximately equal to the base potential VBB of transistor Qc, so the magnitude of the DC current flowing through variable resistor VRb changes, and As a result, the collector current of the transistor Qa also changes, and its collector potential changes, so that the DC level of the primary color signal supplied to the cathode K1 changes.

In this way, the alternating current level and direct current level of the primary color signals supplied to the cathode Kl of the picture tube 3R can be changed independently.

Similarly, the primary color signals supplied to the cathodes K2 and K3VC of the picture tubes 3R and the cathodes K1 of the picture tubes 3G and 3B are
The AC level and DC level of the primary color signals supplied to K3 can also be changed independently. Therefore, this can improve focus. For example, in the example of FIG. 4, any one of the variable resistors VRl to VR3 may be a fixed resistor.

[Brief explanation of drawings]

Fig. 1 is a system diagram of an example of a projection type television receiver, Fig. 2 is a connection diagram of a conventional example, Fig. 3 is a characteristic diagram for explaining the same, and Figs. 4 and 5 are examples of the present invention, respectively. FIG. Q is an output transistor.

Claims (1)

[Claims] 1 Using a picture tube that emits electron beams from a plurality of cathodes and converges them onto a monochromatic phosphor surface, and also supplies a common input signal to the plurality of cathodes to produce a monochrome image on the monochromatic phosphor surface. In the television receiver for reproducing the above, a variable device is provided between each of the plurality of cathodes and the signal source of the input signal for adjusting the beam currents of the electron beams emitted from the plurality of cathodes to be equal to each other. Television receiver with voltage means.