JPH0683468B2 - Mixed circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a mixing circuit for superimposing.

[Outline of Invention]

The present invention is a mixed circuit for superimposing channel numbers and the like on a television screen, and by connecting a high-pass capacitor to a predetermined connection, NTS
Superimpose is possible for any composite color video signal of C, PAL, or SECAM format.

[Conventional technology]

For example, there is a remote control type television receiver in which, when a channel is switched, an image of a newly selected channel is displayed and at the same time, the number of the new channel is digitally displayed by superimposing. Also in VTR, when timer reservation is made, when inputting channel and time etc. for timer recording,
There are also those that allow the numbers to be displayed on the TV screen by superimposing.

When displaying characters (including numbers, symbols, etc.) on a general television screen by superimposing, circuits shown in FIGS. 3 to 5 are considered as circuits for that purpose.

That is, in the circuit shown in FIG. 3, the video signal (composite color video signal) Sv and the character signal Sc are voltage-added by the resistors Rv and Rc, and the added output is replaced by the video circuit (instead of the signal Sv. 1) is supplied to the signal Sv
The white character by the signal Sc is superimposed and displayed on the color screen by.

In the circuit shown in FIG. 4, the video signal Sv from the clamp circuit (2) and the DC voltage Ew equal to the white level are selected by the signal Sc in the switch circuit (3), and the switch output is the video circuit. It is supplied to (1) and the characters are displayed.

Further, in the example shown in FIG. 5, the video signal Sv is
The low-pass filter (4) and the band-pass filter (5) separate the luminance signal Sy and the carrier color signal Ss,
As for the signal Sy, the voltage Ew is changed by the signal Sc as in the example of FIG.
Is added, and the signal Sy and the signal Ss having this voltage Ew are converted into the video signal Sv again by the adder circuit (6) and then supplied to the video circuit (1) to display characters.

[Problems to be solved by the invention]

However, in the circuit of FIG. 3, the video circuit (1)
In the input signal of, the level may drop below the pedestal level in the part other than the signal Sc, so that the television screen becomes unsightly at the character part and becomes unsightly.

Further, in the circuit of FIG. 4, the input signal of the video circuit (1) has the carrier color signal Ss disappearing in the character portion. Therefore, in the case of the SECAM system, the carrier color signal Ss is replaced by limiter noise or false noise. Which produces a color signal component of
Colors and rashes appear on the characters on the TV screen, making it unsightly.

Further, in the circuit of FIG. 5, since the luminance signal Sy and the carrier color signal Ss are separated and the processing of mixing the character signal Sc is performed, the above-mentioned dragging, color, or blurring does not occur. However, the circuit is complicated and the cost increases.
Further, since the signal Sy and the signal Ss are separated from the signal Sv and then synthesized again, it is necessary to match the time of both signals Sy and Ss.

Further, since the character signal Sc is formed by the character generator in any circuit, the video circuit (1)
The rising and falling edges of the character signals Sc and Ew supplied to are very sharp. Therefore, even the band components of the carrier color signal Ss are included, so that the displayed characters are cross-colored.

Furthermore, for example, as shown in FIG. 2, a television screen (7)
When the channel number (8) is displayed on the screen and the brightness of the surrounding area (9) is lowered at the same time, the circuits of FIGS. 3 to 5 become more complicated.

The present invention is intended to eliminate the above problems.

[Means for solving problems]

Therefore, in the present invention, the signal line of the video signal Sv is constructed as shown in FIG. 1, for example.

[Action]

The voltage of the character signal is added to only the luminance signal, and at this time, unnecessary high frequency components of the character signal are removed.

〔Example〕

In the example shown in Fig. 1, this circuit is built into the VTR, and when switching channels etc., the image of the new channel and its channel number (8) are displayed on the TV screen (7), timer reservation etc. In the case of, the corresponding character (8) is displayed and at the same time, the brightness of the surrounding area (9) is lowered.

In FIG. 1, the input terminal T ₁ of the video signal Sv is connected to the emitter of the transistor Q ₁ through the clamp capacitor C ₁ , and the bias resistors R ₁ and R ₂ and the bypass capacitor C ₁ are connected to the base of the transistor Q _{1. 2} are connected to form a clamp circuit (11). And terminal T ₁
, The video signal Sv is supplied with a negative sync polarity, and its sync tip is clamped to the emitter potential of the transistor Q ₁ .

Further, the connection point between the capacitor C ₁ and the emitter is connected to the base of the transistor Q ₂ through a high cut filter (12) that removes unnecessary super high frequency components and prevents oscillation. The emitter of the transistor Q ₂ is grounded through the resistor R ₃ to serve as an emitter follower.

The emitter of the transistor Q ₂ is connected to the base of the transistor Q ₃ through the series circuit of the resistor R ₄ and the capacitor C _3, and is also connected to the base of the transistor Q ₃ through the resistor R ₅ . This transistor is an emitter follower composed of a resistor R ₆ ,
The emitter output is supplied to the video circuit (1) through the oscillation preventing resistor R ₇ .

Further, the input terminal T ₂ of the character signal Sc is connected to the base of the transistor Q ₄ via the capacitor C ₄ . This transistor Q ₄ is provided with a predetermined base bias by resistors R ₈ and R ₉ , and resistors R ₁₀ and R ₁₁ are connected in series between its emitter and ground to form an emitter follower. There is. The connection midpoint of the resistors R ₁₀ and R ₁₁ is connected to the base of the transistor Q ₃ through the switching diode D ₁ and further through the coil L ₁ . The character signal Sc is a signal that becomes "1" level in the character (8) portion.

Further, the terminal T ₃ is an input terminal of the background signal ▲ ▼ which reduces the brightness of the background area (9), and this is through the capacitor C ₅ and further through the speedup capacitor C ₆ and the resistor R ₁₂ to the transistor Q ₅ Connected to the base of.
This transistor Q ₅ is for shaping and phase inversion,
The emitters are grounded by the collector resistors R _{14 to} R _16, and the connection midpoint of the resistors R ₁₅ and R ₁₆ is connected to the base of the switching transistor Q ₆ through the resistor R ₁₇ , and the emitter is connected to the transistor. It is connected to the emitter of Q ₄ and its collector is connected to the junction of diode D ₁ and coil L ₁ . A resistor R ₁₈ is connected in parallel between the base and emitter of the transistor Q ₆ .

Further, the connection midpoint of the resistors R ₁₄ and R ₁₅ is connected to the connection point of the elements D ₁ , L ₁ and Q ₆ through the emitter follower transistor Q ₇ and the switching diode D ₂ . The background signal ▲ ▼ is a signal that becomes “0” level in the background area (9).

Also, in this example, when the tape is played at a speed different from that at the time of recording for reproduction, that is, at the time of variable speed reproduction, the pseudo vertical synchronizing pulse Pv is transmitted from the terminal T ₄ to the capacitor C ₇
Through the emitter follower to the base of transistor Q ₈ and its emitter connected to the emitter of transistor Q ₃ through resistor R ₁₉ . In addition, a transistor Q ₉ is provided whose base is connected to the base of transistor Q ₁ and whose emitter is connected to the emitter of transistor Q ₃ . The pseudo vertical sync pulse Pv has a negative sync polarity and is located immediately before the vertical sync pulse in the video signal Sv.

Also, as an example, R ₃ = 1 kΩ, R ₄ = 47 Ω, R ₅ = 560 Ω C ₃ = 120 pF, L ₁ = 47 μH.

According to such a configuration, the diode D ₁ has the voltage obtained by dividing the emitter potential of the transistor Q ₄ by the resistors R ₁₀ and R ₁₁ and the emitter potential of the transistor Q _{2 to} the elements R ₅ and L _1.
It is biased by the voltage difference from the voltage supplied through. Then, the signal Sc at the terminal T ₂ is taken out in phase to the emitter thereof through the transistor Q ₄ . Therefore, Sc
In the case of = “0” (when the character (8) is not displayed), the emitter voltage of the transistor Q ₄ is low, which causes the diode D ₁ to be reverse biased and off.

Further, the signal ( _{3) at} the terminal T ₃ is inverted in the transistor Q _{5 and} taken out as a signal Sb at its collector.
Therefore, when ▲ ▼ = "1" (when the brightness of the area (9) is not lowered), Sb = "0", and the diode D ₁
Element Q _7, D ₂ in the same manner as in the are off.

Furthermore, the divided voltage of the resistors R ₁₅ and R ₁₆ is also low, so that the transistor Q ₆ is also off.

That is, when Sc = "0", ▲ ▼ = "1", the element Q
₆ , D ₁ , D ₂ are all off and therefore coil L ₁
The lower side in the figure is equivalent to not connected.

Therefore, the video signal Sv of the terminal T ₁ is taken out to its emitter through the signal line of the clamp circuit (11) → filter (12) → transistor Q ₂ , and the luminance signal Sy and the carrier color of this taken out signal Sv are taken. Due to the difference in impedance between the elements R ₅ and R ₄ , C ₃ with respect to the signal Ss, the signal Sv
Among them, the carrier color signal Ss is mainly supplied to the transistor Q ₃ through the signal line of the resistor R ₄ → the capacitor C ₃ .
Mainly of the luminance signal Sy of the signal Sv is supplied to the transistor Q ₃ via a resistor R _5.

Then, in the transistor Q ₃ , the signals Ss and Sy supplied thereto are combined to form the original video signal Sv, which is taken out from the emitter and supplied to the video circuit (1). Therefore, when Sc = “0” and ▲ ▼ = “1”, the normal TV screen (7) without the character (8) and the area (9) is displayed.

On the other hand, when Sb = “1” (when displaying the character (8)), the emitter potential of the transistor Q ₄ increases due to Sb = “1”, and the diode D ₁ is turned on. Then, at this time, a signal Sc of a voltage Ew equal to the white level of the video signal Sv is taken out from the connection midpoint of the resistors R ₁₀ and R ₁₁ by selecting their resistance values in advance. The signal Sc passes through the diode D ₁ and
It is supplied to the transistor Q ₃ through the coil L ₁ and voltage-added to the luminance signal Sy from the resistor R ₅ .

Therefore, the video signal Sv having the luminance signal Sy and the character signal Sc of the white level Ew is taken out from the transistor Q ₃ , and this signal Sv is supplied to the video circuit (1).
On the television screen, the character (8) corresponding to the character signal Sc is displayed in white by being superimposed on the screen by the video signal Sv.

Further, in this case, since the output impedance of the emitter of the transistor Q ₂ is low, when the signal Sc is supplied to the transistor Q ₃ , the high frequency component included in the signal Sc, that is, the same band component as the carrier color signal Ss, Capacitor C ₃ → resistor R ₄
→ Bypassed through the emitter of transistor Q ₂ and not supplied to transistor Q ₃ . Therefore, the displayed character (8) is not cross-colored by the signal Sc.

Furthermore, ▲ ▼ = "0" in the case of (If lowering the luminance of the region (9)) is, Sb = the collector of transistor Q ₅ "1"
Therefore, the voltage at the connection midpoint of the resistors R ₁₅ and R ₁₆ becomes high and the transistor Q ₆ is turned on. Then, the base potential of the transistor Q ₃ is fixed to the emitter potential of the transistor Q ₄ through the transistor Q ₆ , so that the DC level of the signal Sv through the transistor Q ₃ drops to the emitter potential. Therefore, at this time, the luminance is lowered in the area (9).

At this time, since Sc = “1”, the elements Q ₇ and D ₂
Is turned on, so that even if the DC level of the signal Sv of the transistor Q ₃ drops, the element Q ₇ clamps the scanning section of the signal Sv so as not to drop below the pedestal level.
Further, in the case of Sc = "1" at ▲ ▼ = "0" (if the character (8) is displayed in the area (9)), ▲ ▼ = By a "0" the transistor Q ₆ is turned on However, when Sc = “1”, the emitter potential of the transistor Q ₄ becomes high and the transistor Q ₆ is reverse-biased and turned off. Then, at this time, the signal Sc turns on the diode D ₁ , and at the connection midpoint of the resistors R ₁₀ and R ₁₁ , a signal Sc of the white level Ew is obtained, which passes through the diode D ₁ and further through the coil L ₁ . Supplied to transistor Q ₃ . Therefore, in this case, the brightness of the area (9) is lowered and the character (8) is displayed in white there.

Furthermore, during variable speed playback, a pseudo vertical sync pulse is applied to terminal T _4.
Pv is supplied, which is inserted into the video signal Sv from the transistor Q ₃ through the transistor Q ₈ . At this time, the pulse Pv inserted in the signal Sv by the transistor Q _{9 is}
However, it is clamped so that it does not fall below the sync tip level.

Thus, according to the present invention, it is possible to display the character (8) on the television screen (7) and further reduce the brightness of the background area (9). In this case, in particular, according to the present invention, Luminance signal Sy and carrier color signal in video signal Sv
The luminance signal Sy and the carrier color signal Ss are separated by the difference in impedance of the elements R ₅ and R ₄ , C ₃ with respect to Ss, the character signal Sc is voltage-added to the separated luminance signal Sy, and the added luminance is added. Since Sy and the carrier color signal Ss are mixed to form a video signal having a character signal, the character signal does not cause a dragging.

Further, although the character signal Sc of the white level Ew is added, since the carrier color signal Ss does not disappear in the portion of the character signal Sc, color and blurring do not occur even in the SECAM system.

Further, the signal Sv is separated into the signal Sy and the signal Ss, and the signal Sy is added with the signal Sc and then mixed, but the signals Sy and Ss are mixed.
Is performed by utilizing the difference in the impedances of the elements R ₅ and C ₃ with respect to the signals Sy and Ss, the configuration is simple.

Moreover, in that case, since the capacitor C ₃ separates the carrier color signal Ss and at the same time bypasses the high frequency component of the signal Sc in cooperation with the output impedance of the transistor Q ₂ , the displayed character (8) appears. No cross color is generated.

Further, since the brightness of the background area (9) only decreases, the image in the background area (9) can be identified.

Furthermore, the video signal Sv is a transistor of opposite polarity.
Since the character signal Sc taken out through Q ₂ and Q ₃ and added to the signal Sv is formed by the transistor Q ₄ and the diode D ₁ , the changes in the DC level of both signals due to the temperature change become equal, and the temperature change Will be corrected. Further, the pedestal clamp by the transistor Q _{7 is} similarly corrected by the transistor Q ₇ and the diode D ₂ , and the pulse Pv is also similarly corrected by the transistors Q ₃ , Q ₉ . Note that the voltage that determines the brightness of the region (9) is determined only by the emitter potential of the transistor Q ₄ , and therefore the amount of change with respect to temperature changes is insufficient compared to other signals, but it is the voltage that simply decreases the brightness. , There is no display problem.

In the above, the case of VTR, when displaying a character signal from a personal computer,
It can also be applied to video equipment such as video disc players. A resistor may be used instead of the coil L ₁ .

〔The invention's effect〕

According to the present invention, the luminance signal Sy and the carrier color signal Ss are separated by the difference in the impedances of the elements R ₅ and R ₄ , C ₃ with respect to the luminance signal Sy and the carrier color signal Ss in the video signal Sv, and these are separated. Since the voltage of the character signal Sc is added to the luminance signal Sy, and the added luminance Sy and the carrier color signal Ss are mixed to form a video signal having a character signal, no dragging due to the character signal occurs.

Further, although the character signal Sc of the white level Ew is added, since the carrier color signal Ss does not disappear in the portion of the character signal Sc, color and blurring do not occur even in the SECAM system.

Further, the signal Sv is separated into the signal Sy and the signal Ss, and the signal Sy is added with the signal Sc and then mixed, but the signals Sy and Ss are mixed.
Is performed by utilizing the difference in the impedances of the elements R ₅ and C ₃ with respect to the signals Sy and Ss, the configuration is simple.

Moreover, in that case, since the capacitor C ₃ separates the carrier color signal Ss and at the same time bypasses the high frequency component of the signal Sc in cooperation with the output impedance of the transistor Q ₂ , the displayed character (8) appears. No cross color is generated.

Further, since the brightness of the background area (9) only decreases, the image in the background area (9) can be identified.

Furthermore, the video signal Sv is a transistor of opposite polarity.
Since the character signal Sc taken out through Q ₂ and Q ₃ and added to the signal Sv is formed by the transistor Q ₄ and the diode D ₁ , the changes in the DC level of both signals due to the temperature change become equal, and the temperature change Will be corrected. Further, the pedestal clamp by the transistor Q _{7 is} similarly corrected by the transistor Q ₇ and the diode D ₂ , and the pulse Pv is also similarly corrected by the transistors Q ₃ , Q ₉ . Note that the voltage that determines the brightness of the region (9) is determined only by the emitter potential of the transistor Q ₄ , and therefore the amount of change with respect to temperature changes is insufficient compared to other signals, but it is the voltage that simply decreases the brightness. , There is no display problem.

[Brief description of drawings]

FIG. 1 is a connection diagram of an example of the present invention, and FIGS. 2 to 5 are diagrams for explaining the same. Q _{1 to} Q ₉ are transistors, D ₁ and D ₂ are diodes, R _{1 to} R ₁₉
Is a resistor, and C _{1 to} C ₇ are capacitors.

Claims (2)

[Claims] 1. A transistor of a first emitter follower supplied with a composite color video signal and the first emitter follower transistor.
A resistor connected in series between the emitter of the transistor of the emitter follower and the next stage, a capacitor connected in parallel to the resistor, a transistor of the second emitter follower to which a character signal is supplied, A second emitter follower transistor has an emitter circuit of the transistor and an output side end of the resistor, and has a diode and a coil or resistor element connected in series, and the luminance signal in the composite color video signal. Is mainly supplied to the next stage from the transistor of the first emitter follower through the resistor, and the carrier color signal in the composite color video signal is
Mainly supplied from the transistor of the first emitter follower to the next stage through the capacitor, and when the character is displayed by the character signal, the diode is turned on by the character signal, and the diode and the element of the coil or the resistor. A mixing circuit in which the character signal is added to the luminance signal from the resistor through the high frequency component included in the added character signal is bypassed through the capacitor and the transistor of the first emitter follower. 2. A transistor of a first emitter follower supplied with a composite color video signal and the first emitter follower transistor.
A resistor connected in series between the emitter of the transistor of the emitter follower and the next stage, a capacitor connected in parallel to the resistor, a transistor of the second emitter follower to which a character signal is supplied, Between the emitter circuit of the transistor of the second emitter follower and the output side end of the resistor, a diode and a coil or resistor element connected in series and a background signal for reducing the brightness of the background region are supplied. The third transistor and the second
Of the emitter follower transistor and a switching element connected between the output side end of the diode and the luminance signal in the composite color video signal is mainly transmitted through the resistor. The carrier color signal in the composite color video signal supplied from the transistor of the emitter follower to the next stage is
Mainly supplied from the transistor of the first emitter follower to the next stage through the capacitor, and when the character is displayed by the character signal, the diode is turned on by the character signal, and the diode and the element of the coil or the resistor. The character signal is added to the luminance signal from the resistor through, and the high frequency component included in the added character signal is bypassed through the capacitor and the transistor of the first emitter follower, and the background signal is A mixing circuit, which is supplied to the switching element through the third transistor, and when the switching element is turned on, the brightness of the background region is reduced according to the potential of the second emitter circuit.