JPH0526863Y2 - - Google Patents

Description

[Detailed Description of the Invention] The television receiver of the present invention will be explained according to the following items.

A. Industrial field of application B. Overview of the invention C. Prior art [Figures 3 and 4] D. Problems that the invention aims to solve [Figure 5] E. Means for solving the problems F. Examples [Fig. [Fig. 1, Fig. 2] a Circuit configuration [Fig. 1] b Operation [Fig. 2] c Effect d Modification G Effects of the invention (A. Field of industrial application) The present invention is applicable to a new television receiver, especially The present invention relates to a television receiver equipped with a display superimposition function for superimposing displays such as characters and symbols on images broadcast on television.

(B Overview of the invention) The television receiver of the present invention is a television receiver equipped with a display superimposition circuit that receives a display signal for superimposing a display on a reproduced image of a television broadcast and adds the display signal to a color signal transmission path. In order to relatively easily prevent the display from becoming brighter than the image brightness adjustment amount and degrading the display quality, it is possible to display the display while keeping the amplitude of the display signal applied to the color signal transmission path constant. The black level of the signal can be adjusted up or down according to the amount of adjustment for the brightness of the screen, and the color signal transmission path for colors other than specific colors is blanked using a blanking circuit to prevent the display color from changing depending on the background. It's something that happens when you don't have it.

(C. Prior Art) [Figures 3 and 4] Some television receivers are equipped with a character superimposition circuit that superimposes characters such as functions and channels on images broadcast on television. FIG. 3 shows a main part of an example of a conventional character superimposition circuit.
In the figure, a is a color signal reproducing circuit which receives the composite video signal and converts the primary color signals Rout,
Gout and Bout are generated and sent to a CRT display (not shown). VRp is a variable resistor for picture adjustment, and VRb is a variable resistor for brightness adjustment. Both terminals receive power supply voltage Vcc, and the divided output voltage is sent to the color signal reproduction circuit a as the picture master control voltage and brightness control voltage. Send. The color signal reproducing circuit a receives control voltages from variable resistors VRp and VRb, and controls the picture and brightness according to the control voltages. Ra, Rb, Rc are color signal reproduction circuit a
The primary color signals Rout, Gout, and Bout are sent to a CRT display (not shown) through the resistors Ra, Rb, and Rc.

b is a character superimposition circuit, which consists of an emitter follower transistor Qa that receives the character signal Sc through a capacitor Ca at its base, and its base potential is connected to the bleeder resistors Rd and Re when the character signal Sc is "low".
is held at a predetermined low level by. The emitter of the transistor Qa is connected to, for example, a green signal Gout output line of the color signal reproducing circuit a via a resistor Rf. Specifically, it is connected to the terminal of the resistor Rb on the opposite side to the side connected to the green signal output terminal.

When a character signal Sc of "1" is input to the character superimposition circuit b, the green signal Gout is forcibly raised to a predetermined high level as shown in Fig. 4, regardless of the presence or absence and the magnitude of the green component of the composite video signal input to the color signal reproduction circuit a. Therefore, when the character signal Sc arrives, green characters are superimposed on the image.

C is a blanking circuit that performs blanking for primary colors other than the character color (green in this example) when the character signal Sc arrives. Qb and Qc are resistance
Receive character signal Sc to base via Rg and Rh
It is an npn type transistor, and resistors Ri and Rj are connected between the base and ground. transistor
The collectors of Qb and Qc are the red signal Rout and the green signal Bout
connected to the output line. Specifically, it is connected to the terminals of the resistors Ra and Rc on the opposite side to the side connected to the red signal output terminal and the blue signal output terminal.
The emitters of transistors Qb and Qc are both resistors Rk,
It is connected to the output terminal of the resistor voltage divider circuit consisting of R1. This output terminal is set to a level equal to the pedestal level. Cb is a ripple absorbing capacitor connected in parallel to the resistor R1.

In this blanking circuit c, when a character signal sc is generated, transistors Qb and Qc are turned on, and the primary color signals Rout and Bout other than the character color are set to the pedestal level and blanking is performed for red and blue, making the character color completely green. I will make it happen.

Note that the simple type does not have a built-in blanking circuit c, so the color of the characters is not necessarily completely green, but changes depending on the red and blue components of the video signal. Figure 4 shows the character signal Sc and each primary color signal.
In the waveform diagrams of Rout, Gout, and Bout, the two-dot chain line indicates the waveform when the blanking circuit c is not provided.

(Problem to be solved by the D invention) [Figure 5] By the way, in conventional television receivers, the user can adjust the brightness using a variable resistor VRp, for example.
Even if the brightness of the characters displayed on the screen was changed by operating the VRb, the brightness of the characters displayed on the screen did not change at all as shown in Figure 5, which caused the problem that the quality of the characters deteriorated.

In other words, it is now possible to adjust the brightness of the screen of a television receiver to make it easier to view according to the surrounding brightness, personal preference, etc., but in the past, the brightness of the screen could be adjusted using the picture adjustment operation or the brightness adjustment. Even if it is changed by operation, the character signal remains unchanged as shown in Figure 5.
When Sc is "1", the level of the green signal Gout does not change and remains constant. Therefore, even if you reduce the picture brightness and darken the screen, the text will not become darker, so the brightness of the text will become extremely bright relative to the brightness of the screen, causing problems such as deterioration of quality. It was hot.

This invention was made to solve these problems, and the brightness of the display of characters etc.
Brightness changes depending on the amount of screen brightness adjustment, and its purpose is to prevent the relative relationship between screen brightness and display brightness from changing significantly so that the quality of the display that appears on the image does not deteriorate. It is something to do.

(E. Means for Solving Problems) In order to solve the above problems, the television receiver of the present invention receives a display signal that superimposes a display on a reproduced image of a television broadcast, and keeps the amplitude of the display signal constant. A display that changes this black level at a DC level according to the amount of screen brightness adjustment while maintaining the black level and sends it to the color signal transmission path of a specific color in the color signal transmission path as a signal to be added to that color signal. A superimposing circuit, and a blanking circuit that receives the display signal and forcibly substantially extinguishes color signals in the color signal transmission path other than the specific color to enable display in the specific color. It is characterized by

Therefore, according to the television receiver of the present invention,
Since the amplitude of the display signal is kept constant and its black level is raised or lowered according to the amount of brightness adjustment, the level opposite to the black level of the display signal can also be changed according to the amount of brightness adjustment. .
Therefore, the brightness of the display superimposed on the image can be changed according to the amount of adjustment for the brightness of the picture, etc., and the display quality will deteriorate as the brightness of the display becomes unrelated to the brightness of the image. You can eliminate fear.

Even if the black level of the display signal changes depending on the amount of screen brightness adjustment, as long as the black level itself is kept sufficiently lower than the pedestal level, the display signal will have no effect on the image. I don't get it.
Therefore, there is no fear that the image (the image in the area other than the display) will change due to a change in the black level of the display signal due to a change in the amount of adjustment of the brightness of the screen.

Then, by changing the black level according to the amount of brightness adjustment while keeping the amplitude of the display signal constant, the level opposite to the black level of the display signal is indirectly changed, so the display signal In order to realize changing the black level and the level opposite to the black level, an amplifier with a complicated circuit configuration is not required, and it can be realized with a simple clamp circuit without causing a significant increase in cost.

Further, since the color signals in the color signal transmission path other than the display color are substantially erased by the blanking circuit, the display color is completely unaffected by the background and becomes constant.

(Embodiment F) [Figures 1 and 2] The television receiver of the present invention will be explained below according to the illustrated embodiment.

(a. Circuit configuration) [FIG. 1] FIG. 1 shows the essential parts of an example of the implementation of the television receiver of the present invention.

In the figure, 1 is a color signal reproducing circuit that receives a video signal and generates primary color signals Rout, Gout, and Bout. Each primary color signal Rout, Gout, and Bout output from each output terminal of the color signal reproducing circuit 1 is Resistor R1,
The signal is sent to the CRT display through R2 and R3.

VRp is a variable resistor for picture adjustment, VRb is a variable resistor for brightness adjustment, and the power supply voltage Vcc is received between both terminals to form a voltage divider circuit with a variable voltage division ratio.The output voltage, that is, the pictureure control voltage , the brightness control voltage is sent to the color signal reproducing circuit 1 via resistors R4 and R5.

2 is a character superimposition circuit, C1 is a capacitor that receives the character signal Sc input to each character superimposition circuit 2, and Q
1 is a transistor that receives a character signal Sc via a capacitor C1, and bias resistors R6 and R7
is base biased by Transistor Q1 constitutes an emitter follower circuit, and its emitter is grounded via emitter resistor R8.
The output terminal of this emitter follower circuit is connected to the base of transistor Q2 via capacitor C2. The transistor Q2 constitutes an emitter follower circuit functioning as a buffer circuit, and its emitter is connected to the green signal Gout line via a resistor R9. Specifically, it is connected to the terminal of the resistor R2 on the opposite side to the side connected to the color signal reproduction circuit 1.

Q3 is the character signal at the base of transistor Q2
A transistor that clamps the level when Sc is "0" constitutes an emitter follower circuit, and its emitter is connected to the base of transistor Q2. R10 is an emitter resistor,
It is connected between the emitter of transistor Q3 and ground.

Variable resistors VRp and VRb are connected to transistor Q3.
A picture control voltage and a brightness control voltage are applied. D1 and D2 are diodes for preventing the picture control voltage and brightness control voltage from influencing each other in the character superimposition circuit 2, and their anodes are connected to the movers of the variable resistors VRp and VRb. , the cathode is resistor R11,
It is connected to the base of transistor Q3 via R12. R13 is a resistor connected between the base of transistor Q3 and ground. Resistance R1
1, R12 and R13 are control voltage and primary color signal
This is for level adjustment with Gout.

3 is a blanking circuit, Q4 and Q5 are resistors R
14, receives the character signal Sc through R15, and when the character signal Sc is "1", the red signal Rout and the green signal
Force Bout to pedestal level (i.e.
Virtually eliminates the signal. ). R18 and R19
is a resistor forming a resistor voltage divider circuit for obtaining the pedestal level, and a capacitor C3 for ripple removal is connected in parallel to the resistor R19. The emitters of transistors Q4 and Q5 are connected to the output terminal of the resistor voltage divider circuit. Further, the collectors of the transistors Q4 and Q5 are connected to the output lines of color signals Rout and Bout other than the character color.

(b Operation) [Figure 2] The character signal Sc input to the character superimposition circuit 2 is at the "0" level most of the time, and is at the "1" level only occasionally, that is, for a short time when characters should be displayed. Become. Therefore, for convenience, the character signal Sc is set to "0".
The time when the level is reached is called the normal time. Normally, the base level of transistor Q2 is determined by the higher value of the picture control voltage or the brightness control voltage. That is, the base level of transistor Q2 is clamped by the picture control voltage or the brightness control voltage. Therefore, for convenience, the one to be clamped out of the two control voltages will simply be referred to as the control voltage.

When the character signal Sc becomes "1", the base level of the transistor Q2 becomes higher by the amplitude of the character signal Sc than when it is "0", and as a result, the level of the green signal Gout is also forcibly increased. ,
A green display will be displayed on the screen.

By the way, the level of the green signal Gout when the character signal Sc is "1" is determined by the control voltage as shown in Figure 2, and the lower the control voltage, the lower the level of the green signal Gout when the character signal Sc is "1". green traffic light
Gout's level will also be lower. This is because under normal conditions, the base side of transistor Q2 is maintained at a level approximately equal to the level of the base of transistor Q3 that receives the control voltage (strictly speaking, the level is lower than the base level of transistor Q3 by a base-emitter voltage of about 0.7V). The level changes depending on the control voltage, and the lower the control voltage, the lower the level on the base side of the transistor Q2. When the character signal Sc is applied to the base of the transistor Q2 through the capacitor C1, the emitter follower transistor Q1, and the capacitor C2, the base level of the transistor Q increases by the amplitude of the character signal Sc, as described above. Therefore, the base level when the character signal Sc is "1" is also determined by the control voltage, and becomes lower as the control voltage is lower. Therefore, the brightness of the characters displayed on the screen also changes depending on the control voltage, and if the picture control voltage and brightness control voltage are lowered so that the screen becomes darker, the brightness of the characters will also decrease accordingly. Note that the signal whose level fluctuates at the base of the transistor Q2 is referred to as a character signal Sca.

In addition, since the base level of transistor Q2 under normal conditions, that is, when the character signal Sc is "0", is set to a level sufficiently lower than the pedestal level, fluctuations in the base level due to the control voltage will cause the characters in the video to change. There is no fear that this will affect areas that are not displayed.

Furthermore, when the character signal Sc becomes "1", transistors Q4 and Q5 turn on, forcing the red signal Rout and the green signal Bout to the pedestal level and blanking out colors other than green, so the characters are completely green. become.

(c) Operation In this manner, according to the above-described television receiver, the base side of the emitter follower transistor Q2 which transmits the character signal Sc to the signal line which transmits the color signal which is the same as the color of the characters is clamped to a level corresponding to the picture control voltage or the brightness control voltage,
The base level of this transistor Q2 (character signal
Sca) due to the character signal Sc, the amount of fluctuation (in other words, the amplitude) is made constant, so the character signal Sc
The base level (character signal Sca) of the transistor Q2 when is "1", and further the level of the color signal of the same color as the color of the character (i.e., the green signal Gout in this embodiment) can be changed by the picture control voltage or the brightness control voltage. Therefore, the brightness of the character can be automatically adjusted according to the adjustment amount of the brightness of the screen.
This prevents the text from remaining bright even when the screen is adjusted to be dark.

According to the above embodiment, the transistor Q
Even if the base level (Sca) when the character signal Sc of 2 is “0” varies depending on the control voltage,
Since the level itself is sufficiently lower than the pedestal level, it has no effect on the image (the part of the image where no characters are displayed).
Therefore, there is no possibility that a change in the base level Sca of the transistor Q2 when the character signal Sc is "0" will adversely affect the image.

Then, the base level (character signal
By changing the black level of Sca) according to the control voltage for screen brightness, the base level (character signal Sca) when the character signal Sc is "1" is indirectly raised or lowered according to the control voltage. Therefore, the brightness of the characters can be changed according to the amount of adjustment to the brightness of the screen using a simple clamp circuit without using an amplifier having a particularly complicated circuit configuration.

(d Modification) In the above embodiment, the color of the displayed characters is green, but it may be red or blue. For example, if the text is to be colored red, the text signal Sca may be added to the line that transmits the red signal Rout. Furthermore, it is not always necessary to use the primary colors for the characters. In that case, the line to which the character signal Sca is added is, for example, a red light.
It is sufficient to use a plurality of lines, such as the Rout transmission line and the green signal Gout.

In this embodiment, what is displayed on the tube surface is characters, but the display is not limited thereto, and may be a mark or the like.

(G. Effect of the invention) As described above, the television receiver of the invention receives a display signal that superimposes a display on a reproduced image of a television broadcast, and maintains the amplitude of the display signal constant while adjusting the black level. a display superimposition circuit that sends a signal changed at a DC level according to the amount of adjustment of screen brightness to a color signal transmission path of a specific color in a color signal transmission path as a signal to be added to the color signal; and a blanking circuit that receives a signal and forcibly substantially extinguishes color signals in the color signal transmission path other than the specific color to enable display in the specific color. be.

Therefore, according to the television receiver of the present invention,
Since the amplitude of the display signal is kept constant and its black level is raised or lowered according to the amount of brightness adjustment, the level opposite to the black level of the display signal can also be changed according to the amount of brightness adjustment. .

Therefore, the brightness of the display superimposed on the image can be changed according to the amount of brightness adjustment, and there is a risk that the display will have a brightness that is unrelated to the brightness of the image and the quality of the display will deteriorate. can be eliminated.

Even if the black level of the display signal changes depending on the amount of screen brightness adjustment, as long as the black level itself is kept sufficiently lower than the pedestal level, the display signal will have no effect on the image. I don't get it.

Therefore, there is no fear that the image (the image in the area other than the display) will change due to a change in the black level of the display signal due to a change in the amount of adjustment of the brightness of the screen.

Then, by changing the black level according to the amount of brightness adjustment while keeping the amplitude of the display signal constant, the level opposite to the black level of the display signal is indirectly changed, so the display signal There is no need for an amplifier with a complicated circuit configuration to change the black level and the opposite level.
This can be achieved with a simple clamp circuit without causing a significant increase in cost. In other words, it is possible to keep the black level of the display signal constant and change its amplitude as a means of changing the brightness of the display, but in that case, the A display signal amplification amplifier whose amplification degree changes is required. Further, such an amplifier has a complicated circuit configuration, leading to an increase in cost.
However, according to the present invention, since the amplitude of the display signal is kept constant while the black level is varied, a simple clamp circuit is required, and an unnecessary increase in cost can be avoided.

Furthermore, since it has a blanking circuit that substantially eliminates color signals in the color signal transmission path other than the display color by setting them to a pedestal level when a display signal is received, the display color depends on the background color. Since it is not affected, it is possible to obtain a constant color (the above-mentioned specific color) without any turbidity.

[Brief explanation of the drawing]

Figures 1 and 2 show an example of the implementation of the television receiver of the present invention. Figure 1 is a circuit diagram showing the main parts, and Figure 2 is a waveform of a display signal and a color signal of the same color as the display. Figure 3 is a circuit diagram showing a conventional example, Figure 4 is a waveform diagram of a display signal and each primary color signal, and Figure 5 is a character signal showing problems in the conventional example and the same color as the character. It is a waveform diagram of a signal. Explanation of symbols, 2...Display superimposition circuit, Sc, Sca...
...display signal.

Claims (1)

[Claim for Utility Model Registration] Receiving a display signal that superimposes a display on a reproduced image of television broadcasting, while keeping the amplitude of the display signal constant, the black level is adjusted to a DC level according to the amount of adjustment of screen brightness. a display superimposition circuit that sends the changed signal to a color signal transmission path of a specific color in the color signal transmission path as a signal to be added to the color signal; and a display superimposition circuit that receives the display signal and transmits a color signal other than the specific color. A television receiver comprising: a blanking circuit that forcibly substantially extinguishes a color signal on a path to enable display in the specific color.