JPS63161790A - Television receiver - Google Patents

Abstract

PURPOSE:To reduce the deterioration of a picture quality in one frame caused by simple double swing by adjusting the luminance level or the contrast of a video signal alternately in the horizontal scanning period of the video signal which is converted in double speed. CONSTITUTION:A bias circuit 5 is for giving a DC bias to picture tube driving circuits 9-11 and it is constituted of resistances R1-R3 and a transistor Q1, and the picture tube driving circuits 9-11 are constituted of a amplification transistor Q2, a collector resistance R4, an emitter resistance R5 and an emitter peaking capacity C1. And the DC voltage outputted from the bias circuit 5 decides the DC actuating point of the picture tube driving circuits 9-11 and sets the luminance level of the video signal. Thus, the deterioration of the picture quality in one frame caused by simple double swing can be reduced by changing the luminance level of an interpolation signal at the time of double scanning.

Description

DETAILED DESCRIPTION OF THE INVENTION [Objective of the Invention] (Industrial Application Field) The present invention relates to a television receiver whose horizontal scanning speed has been converted to (A speed), and particularly relates to an improvement of a video signal amplification circuit.

(Prior Art) Conventionally, some television receivers use a so-called double scan system, which doubles the horizontal scanning frequency and doubles the number of scanning lines within one field. In this double scan method, it is necessary to generate an interpolation signal to double the number of scanning lines using the original video signal. The simplest method for generating this interpolation signal is to use two line memories, and while a video signal for one horizontal scanning period is being written to one line memory, the video signal from another line memory is being written at twice the writing speed. This is a simple double-reverse method in which the video signal written in the previous scanning period is read out twice in succession at the same speed.

FIG. 3 shows line memory A of the above-mentioned twice-swiveling method.

The configuration of line memory A is shown in (a) when line memory A is in the write state and line memory B is in the read state.
indicates a read state and B indicates a write state. Figure 4 shows the read and write timing of line memories A and B, where (a) shows the input video signal, (bl)
, (b2) shows the write data and read data of line memory A, (cl), (c2), respectively.
) The figure shows the write data and read data of line memory B, respectively, and the figure (d) shows the combined output timing of line memories A and B. Figure 5 shows an example of the screen configuration of the receiver when double speed conversion is performed by line memories A and B, and Figure (a) shows the screen configuration of the first and second fields of the interlaced system. , (b) shows the screen configuration of the first field and second field of the double scan method.

(Problems to be Solved by the Invention) However, in the above-mentioned double-scan method using simple double-scanning, the following problems occur because the interlaced video signal that is originally sent is converted. .

That is, in the interlaced system, as shown in FIG. 5(a), one
One frame constitutes one image, and the picture signals are different in adjacent scanning lines (A, a, B, etc. in Fig. 5(a)) between the first and second fields. There are cases. Therefore, as shown in Figure 5(b), when the same picture is scanned twice in the same field using the double scan method, the scanning lines of the first and second fields overlap within one frame, and on a certain scanning line. In this case, the images in the first and second fields overlap, which may deteriorate the image quality.

In the case of Fig. 5, the scanning lines a and a of the interlaced signal are adjacent to each other, and when double-speed conversion is performed as shown in Fig. As shown in B1, the picture becomes a city, and the amount of information within one frame deteriorates.

This invention was made to solve the above-mentioned problem, and when reproducing captured signals on the screen using the double scan method, it is possible to reduce the deterioration in image quality within one frame due to simple double scanning. The purpose is to provide television receivers.

° [Configuration of the Invention (Means for Solving Problems) In other words, the television receiver according to the present invention uses two line memories to alternately write and read video signals, and when reading, write and read video signals. In a method of doubling the speed of a video signal by reading it out at a frequency that is twice the frequency, the system comprises an adjusting means for adjusting the brightness level or contrast of the video signal every other horizontal scanning period of the video signal that has been converted to the double speed. be done.

(Function) 1- In a television receiver using structural acid, when the inter-interval signal and the original signal overlap within one frame, reducing the brightness or contrast of the inter-interval signal as much as possible will prevent deterioration in image quality. It is possible to suppress the Extremely 100
If the level of the interlaced signal is reduced, the original interlaced screen will be created, and the image quality deterioration will be completely eliminated, but the effect of double scanning will also be eliminated, and by adjusting this level arbitrarily, an optimal image can be obtained.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows its configuration, and FIG. 2 shows input and output waveforms of its main parts. The input terminal 1 is supplied with the water N1tAFC pulse shown in FIG. 2(a).

This pulse is applied to the CP terminal of the J- type flip-flop 2. This flip-flop 2 is a general type, and can be used for the large CP input shown in FIG. 2(a).
As shown in b), a Q output that is inverted in one horizontal scanning period is obtained. This Q output is supplied to a bias circuit 5 through a parallel circuit of a variable resistor 3 and a speed-up capacitor 4.

This bias circuit 5 is a picture tube drive circuit 9゜10.1
1 to give a DC bias to the resistor R1-R
3 and a transistor Ql. In other words, resistance R
1 and R2 are inserted in series between the power supply terminal VCC2 and ground for setting the base voltage of the transistor Q1. An emitter follower resistor R is attached to the emitter of transistor Q1.
3 is connected, and a DC voltage higher than the base voltage by the base-emitter junction potential VBE is extracted.

On the other hand, the picture tube drive circuits 9 to 11 are composed of an amplifying transistor Q2, a collector resistor R4, an emitter resistor R5, and an emitter peaking capacitor Fa C1, and input terminals 6 to
The primary color signals R, G, and B supplied to the base of the transistor Q2 via the transistor Q2 are amplified to drive the cathode electrode of the picture tube 15 via the protective resistors 12 to 14.

In the above configuration, the DC voltage output from the bias circuit 5 determines the DC operating point of the picture tube drive circuit, and sets the brightness level of the video signal. For this reason, the second
As shown in Figure (C), the base voltage of the transistor Ql of the bias circuit 5 is set to 3i by the Q output of the flip-flop 2.
11, it is possible to change the DC operation level of the picture tube drive circuits 9-10 and change the brightness level.

By the way, the interpolation signal for double scan is created every other horizontal period. Therefore, as shown in FIG. 2(C), if the brightness level is changed using the signal Q obtained by counting down the horizontal AFC pulse by the flip-flop 2,
It is possible to correct the brightness of the interpolated signal. In other words, by adjusting the iiJ variable resistor 3, the brightness correction level of the interpolation signal can be arbitrarily set, so that the optimum screen can be adjusted.

Therefore, the television receiver having the above configuration can reduce the deterioration in image quality within one frame due to simple swing twice by changing the brightness level of the interpolation signal during double scanning.

Incidentally, in the above embodiment, the case where the brightness level is corrected has been described, but the same effect can be obtained even if the contrast is corrected using a similar method.

[Effects of the Invention] As described in 1- below, according to the present invention, when reproducing the captured signal on the screen using the double scan method, it is possible to reduce the deterioration in image quality within one frame due to the rat pure double swing. Television receivers can be provided.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of a television receiver according to the present invention, Fig. 2 is a waveform diagram showing input and output waveforms of the main parts of the same embodiment, and Fig. 3 is a double scan circuit using line memory. FIG. 4 is a read/write timing diagram of the line memory in FIG. 3, and FIG. 5 is a diagram for explaining the screen configuration by double scan. 2... J-type flip-flop, 3... Variable resistor, 4... Speed-up capacitor, 5... Bias circuit, 9-11... Picture tube drive circuit, 12
~14...Protection resistor, 15... Picture tube. Applicant's agent Patent attorney Takehiko Suzue (a) (b) Figure W45

Claims (1)

[Claims] In a television receiver that uses two line memories to alternately write and read video signals, and when reading, the video signal is read at a frequency twice the writing frequency to convert the video signal to double speed, the double-speed converted video is 1. A television receiver comprising adjustment means for adjusting the brightness level or contrast of a video signal every other horizontal scanning period of the signal.