JP2572464B2 - Color signal processing circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal processing circuit suitable for use in a video tape recorder, a television receiver, and the like, and more particularly, to a color signal for adjusting the hue of a screen. It relates to a processing circuit.

[Prior Art] The hue of a screen is different depending on the viewer, and differs depending on the environment in which the television receiver is placed. For this purpose, the television receiver is provided with a color signal processing circuit which can adjust the hue of the screen by the user. Also, when displaying the screen of the playback signal of the video tape recorder, the desired hue is displayed on the screen by the playback signal of the video tape recorder even if the hue adjustment is performed on the reception screen by the used television receiver. May not be obtained. In such a case, the video tape recorder may be provided with a color signal processing circuit capable of adjusting the hue, so that the user can adjust the hue.

By the way, as described in 7.3.1 (1) of “NHK Color Television Textbook [Upper]” edited by the Japan Broadcasting Corporation, published by Japan Broadcasting Publishing Association, pp.199-200, pp.199-200,
This can be performed by changing the relative phase relationship between the carrier chrominance signal and the reference chrominance subcarrier for demodulating the carrier chrominance signal. The reference color subcarrier is synchronized in frequency and phase with the color burst signal added to the carrier color signal, and is generated from the color burst signal.

An example of a specific color signal processing circuit for adjusting the hue of the screen in this manner is described in pp. 226-228 of the above-mentioned document. In the process of demodulating a carrier color signal, a color burst signal is extracted from the carrier color signal, the phase of the color burst signal is adjusted by an amount corresponding to the hue adjustment amount, and supplied to an APC (automatic phase control) circuit. Then, a reference color subcarrier whose frequency and phase are synchronized with the phase-adjusted color burst signal is formed. The carrier chrominance signal is demodulated by the reference color subcarrier, but the phase of the extracted color burst signal is changed by changing the hue adjustment amount, and accordingly, the reference color subcarrier and the reference color subcarrier are changed. The hue of the screen changes due to a change in the relative phase relationship with the carrier color signal.

[Problems to be Solved by the Invention] In a video tape recorder, a color information signal is output as a carrier color signal to which a color burst signal is added. Other television devices such as a television receiver may output a color information signal in a similar signal form. In such a television device, if the hue adjustment can be performed using the above-described conventional color signal processing circuit, the hue adjustment is performed in the demodulation process in the color signal processing circuit. The color information signal output from the color signal processing circuit is a demodulated color difference signal. As described above, in order to make the output color information signal of the television device a carrier color signal to which a color burst signal is added, demodulation is performed. It is necessary to further perform a process of performing quadrature two-phase modulation on the color difference signal and adding a new color burst signal.

As described above, if the above-described conventional color signal processing circuit is provided in a television device that outputs a carrier color signal to which a color burst signal is added as a color information signal, and it is intended to enable hue adjustment of a screen with this television device, The color signal processing circuit includes not only means for adjusting the hue, but also a circuit for changing the carrier color signal, a demodulation circuit and a burst addition circuit, and the circuit configuration becomes complicated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a color signal processing circuit which can solve such a problem and can adjust the hue of a screen with a simple circuit configuration.

[Means for Solving the Problems] In order to achieve the above object, a first aspect of the present invention is to output a non-inverted signal and an inverted signal of an input signal obtained by adding a color burst signal to a carrier color signal. Means, a series circuit of a resistor and a variable capacitance device connected between the output terminal of the non-inverted signal and the output terminal of the inverted signal in the first means, and a capacitance of the variable capacitance device A second means for changing the value in a direction opposite to each other between a color burst signal period and a carrier color signal period of the input signal with respect to a predetermined reference capacitance value, and a connection point between the resistor and the variable capacitance device. And an output signal is obtained from

Also, the present invention provides a first means for outputting a non-inverted signal and an inverted signal of an input signal obtained by adding a color burst signal to a carrier chrominance signal; A first series circuit of a first resistor and a first variable capacitance device connected between an output terminal and an output terminal of the inverted signal; and an output terminal of the non-inverted signal by the first means And a second series circuit of a second resistor and a second variable capacitance device connected between the first and second variable capacitance devices and a capacitance value of the first and second variable capacitance devices. A second means for changing the reference capacitance value in the opposite direction to each other, a signal obtained from a connection point between the first resistor and the first variable capacitance device, the second resistor and the second resistor. One of the signals obtained from the connection point with the variable capacitance device is selected during the color burst signal period of the input signal. Constituted by a third means for selecting the other to carrier chrominance signal period of the input signal.

[Operation] In the first aspect of the present invention, an output signal is obtained from a connection point between the resistor and the variable capacitance device in the series circuit, thereby forming a phase shift circuit including the resistor and the variable capacitance device. The phase shift amount changes according to the capacitance value of the variable capacitance device. Accordingly, this output signal is obtained by shifting the phase of the input signal by the phase shift amount corresponding to the capacitance value of the variable capacitance device.

Therefore, when the capacitance value of the variable capacitance device is changed from a predetermined reference capacitance value in the color burst signal period and the carrier chrominance signal period of the input signal in the opposite directions to each other by the second means,
The color burst signal and the carrier chrominance signal of the output signal are further phase-shifted in opposite directions about the phase shift amount by which the input signal is shifted according to the reference capacitance value. As a result, a different phase relationship occurs between the color burst signal and the carrier color signal in the input signal, and the hue on the screen changes.

In the second aspect of the present invention, the first and second series circuits constitute a phase shift circuit in the same manner as the series circuit. Then, the capacitance values of the first and second variable capacitance devices in the first and second series circuits are changed by the second means in a direction opposite to each other with respect to a predetermined reference capacitance value. The output signals of the transfer circuit are further phase-shifted in opposite directions about the amount of phase shift of the input signal in accordance with the variable capacitance value.

Therefore, one of these output signals of the phase shift circuit is selected by the third means during the color burst signal period of the input signal,
When the other of these output signals of the transfer circuit is selected during the carrier color signal period of the input signal, the output signal of the third means becomes the first signal.
Similarly to the present invention, the color burst signal and the carrier chrominance signal are further phase-shifted in opposite directions about the phase shift amount of the input signal in accordance with the reference capacitance value. As a result, a different phase relationship occurs between the color burst signal and the carrier color signal in the input signal, and the white phase on the screen changes.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of a color signal processing circuit according to the present invention, wherein 1 is an input terminal, 2 is a non-inverting amplifier,
3 is an inverting amplifier, 4 is a resistor, 5 is a variable capacitance device, 6 is an output terminal, and 7 is an input terminal.

In the figure, an input signal a to an input terminal 1 is obtained by adding a color burst signal to a carrier chrominance signal, and is supplied to a non-inverting amplifier 2 and an inverting amplifier 3 having the same gain.
A resistor 4 and a variable capacitance device 5 are connected in series between the output terminals of the non-inverting amplifier 2 and the inverting amplifier 3.
The connection point between the resistor 4 and the variable capacitance device 5 is connected to the output terminal 6. The non-inverted signal of the input signal a output from the non-inverting amplifier 2 is supplied to the resistor 4, and the inverted signal of the input signal a output from the inverting amplifier 3 is supplied to the variable capacitance device 5.

Here, the non-inverted signal output from the non-inverted amplifier 2 is
v _i, and the output signal at the output terminal 6 and v _0, the inverted signal output from the inverting amplifier 3 is -v _i. Therefore, the resistance value of the resistor 4 R, and the capacitance value of the variable capacitance device 5 is C, the following relationship holds between the non-inverted signal v _i and the output terminal v _0.

(However, ω = 2πf, where f is the frequency of the input signal)
The gain of the non-inverting amplifier 2 and the inverting amplifier 3 is A,
Assuming that the input signal a is v _I , v _i = Av _I , so the above equation (1) is expressed as follows.

Therefore, the transfer function between input terminal 1 and output terminal 6 is
According to the above equation (2), Becomes

The phase characteristic of the transfer function represented by equation (3) is And the gain characteristic is Becomes

As is apparent from the equations (4) and (5), the input signal a is represented by the resistance value R of the resistor 4 and the capacitance value C of the variable capacitance device 5.
, But the amplitude is not affected by the resistance value R and the capacitance value C. Therefore, by changing the resistance value R or the capacitance value C,
The phase shift amount θ can be changed without changing the amplitude.

Therefore, in FIG. 1, the capacitance value C of the variable capacitance device 5 is changed by the control voltage b from the input terminal 7, and the capacitance between the color burst signal period and the carrier color signal period of the input signal a is changed. The direction in which the value C changes is the reverse direction with respect to a reference capacitance value (hereinafter referred to as a reference capacitance value C ₀ ). Thereby, the color burst signal of the output signal v ₀ and the carrier chrominance signal undergo different phase shifts, and the phase difference between the color burst signal of the input signal a and the carrier chrominance signal differs between these signals. Relationships arise. Thereby, the hue of the screen according to the output signal v ₀ is different from the hue of the screen according to the input signal a, so that the hue can be adjusted.

The control voltage b for this will be described below with reference to FIG.

FIG. 2A shows one horizontal period of the input signal a. The color burst signal BS and the carrier chrominance signal are provided for each horizontal period.
CS and time line up.

So as to obtain a screen by the input signal a when the hue adjustment is not performed, the control voltage b is a constant voltage indicated by the solid line in FIG. 2 (b) (hereinafter referred to as reference voltage) held in the b ₁ Is done. Control voltage b is the reference capacitance C ₀ capacitance value C of the variable capacitance device 5 when a reference voltage b _1, the amount of phase shift of the output signal v ₀ for the input signal a at this time theta ₀ Is referred to as a reference phase shift amount. In this case, the phase shift amounts of the color burst signal and the carrier chrominance signal of the output signal v ₀ are both equal to the reference phase shift amount θ _0, and the transfer relationship between these signals is the same as that of the input signal a. Therefore,
No hue change occurs on the screen.

If the hue adjustment is made different from the screen by the input signal a hue, as shown by the broken line b ₂ in FIG. 2 (b),
Control voltage and the color burst signal BS period and carrier chrominance signal CS period b is varied in different directions from the reference voltage b _1. Thereby, the capacitance value C of the variable capacitance device 5 becomes Δ
C ₁ and ΔC ₂ are both positive values and C
Assuming that ₀ ± ΔC ₁ , C ₀ ΔC ₂
Becomes Accordingly, assuming that the phase shift amount θ _B of the color burst signal in the output signal v ₀ with respect to the color burst signal in the incoming signal a is θ ₀ ± Δθ ₁ , the input signal of the carrier color signal in the output signal v ₀ The phase shift amount θ _C for the carrier color signal at a is θ
₀ [Delta] [theta] _2, and the change in opposite directions to each other in the center phase shift is a reference phase shift theta ₀ of the color burst signal and the carrier chrominance signal. For this reason, the phase relationship between the color burst signal and the carrier chrominance signal in the output signal v ₀ is more than the same phase relationship in the input signal a, θ _B −θ _C = ± (Δθ ₁ + Δθ ₂ ) (6) ), And the hue of the screen changes accordingly.

FIG. 3 is a graph showing the phase characteristics of the equation (4) with the CR value on the horizontal axis and θ on the vertical axis.
Is set to 1 when RωC = 1. As is clear from this figure, when CR = 1, θ = −90 °, and this point is the center of the region of the phase characteristic curve with good linearity.
Therefore, by setting the reference phase shift amount θ ₀ = −90 °, the hue can also be changed to the greatest extent with respect to the change amount from the reference voltage b ₁ (FIG. 2B) of the control voltage b. .

Note that f = ω / 2π in the equation (4) is, in the case of the NTSC system,
Set to 3.58 MHz chrominance subcarrier frequency. If the reference phase shift amount θ ₀ in this case is −90 °, the resistance value R of the resistor 4 and the capacitance value C of the variable capacitance device 5 are, for example, 2 k
Ω, 20 pF.

As described above, in this embodiment, the carrier chrominance signal to which the color burst signal is added can be directly transferred to change the transfer relationship between the color burst signal and the carrier chrominance signal. The signal and the carrier color signal can be simultaneously phase-shifted in opposite directions.
For this reason, the circuit configuration is simplified by eliminating the need for modulation and demodulation means, and the change in the phase relationship can be increased to enable a wide range of hue adjustment.

Further, there is no change in the amplitude of the color burst signal or the carrier chrominance signal, so that the degree of saturation on the screen does not change.

FIG. 4 is a diagram showing a specific circuit example of the embodiment shown in FIG. 1, wherein 8 is a differential amplifier, 9 and 10 are transistors,
11 and 12 are resistors, 13 is a transistor, 14 is a resistor, 15 is a variable resistor, 16 is a differential amplifier, 17 is a switch, 18 is an input terminal, and portions corresponding to FIG. Is attached.

In the figure, an input signal a composed of a color burst signal and a carrier chrominance signal input from an input terminal 1 is supplied to a differential amplifier 8. The differential amplifier 8 has a function of the non-inverting amplifier 2 and the inverting amplifier 3 in FIG. 1, the non-inverted signal v ₁ of the input signal a and the inverted signal -v ₁ is generated. The non-inverted signal v ₁ passes through a transistor 9 constituting an emitter follower together with a resistor 12 and is supplied to a resistor 4. Further, the inverted signal -v ₁ passes through the transistor 10 constituting the Emitsutahorowa with resistor 11, variable capacitance device 5
Supplied to Signal obtained at the connection point between the resistor 4 and the variable capacitance device 5 passes through the transistor 13 constituting the Emitsutahorowa with resistor 14, is output from the output terminal 6 as an output signal v _0.

On the other hand, the resistance value of the variable resistor 15 changes according to the operation of a hue adjustment knob (not shown), and a voltage corresponding to the resistance value is generated and supplied to the differential amplifier 16. The differential amplifier 1 outputs _two voltages V ₁ and V ₂ and supplies them to the switch 17. This switch 17 is controlled by a burst gate pulse synchronized with an input signal a from an input terminal 18 and outputs the output voltages V ₁ , V _{2 of the} differential amplifier 16 during the color burst signal period of the input signal a.
Is selected, and the other of the output voltages V ₁ and V ₂ is selected during the carrier color signal period of the incoming journey new a. The output voltage of the switch 17 is the control voltage b and is supplied from the input terminal 7 to the variable capacitance device 5.

When the resistance value of the variable resistor 15 is a specific reference resistance value, the output voltages V ₁ and V ₂ of the differential amplifier 16 are both equal to the reference voltage value b ₁ indicated by a solid line in FIG. At this time, the control voltage b is also the reference voltage b ₁ fixed. But,
When the resistance value of the variable resistor 15 is changed from the reference resistance value in one direction (for example, in a direction in which the resistance value increases), the output voltages V ₁ , V
₂ changes in the opposite direction from the reference voltage b ₁ and changes the resistance value of the variable resistor 15 from the reference resistance value in the other direction, the output voltages V ₁ and V ₂ change in the above directions respectively. Reverse each other. That is, if the resistance value of the variable resistor 15 is not the reference resistance value, the output voltages V ₁ and V ₂ have different voltage values deviated from the reference voltage b _{1 in} opposite directions. It was but connexion, control voltage b at this time is as indicated by a broken line b _2, for example FIG. 2 (b), becomes different from the voltage value and the input and the new a color burst signal period of the carrier chrominance signal period.

According to such a specific circuit, the variable capacitance device 5 can have a small capacity, and the variable capacitance device 5 and a transistor and a resistance element have a simple circuit configuration. It will be good.

FIG. 5 is a block diagram showing another embodiment of the color signal processing circuit according to the present invention, wherein 4A and 4B are resistors, 5A and 5B are variable capacitance devices, 8A and 8B are differential amplifiers, 19A and 19B. Is a variable phase shifter, 20
Is a switch, and 21 is an input terminal. Portions corresponding to the above-mentioned drawings are denoted by the same reference numerals, and redundant description is omitted.

In the figure, a variable phase shift circuit 19A comprising a differential amplifier 8A, a resistor 4A and a variable capacitance device 5A and a variable phase shift circuit 19B comprising a differential amplifier 8B, a resistor 4B and a variable capacitance device 5B are shown in FIG. It has the same configuration, but only the variable capacity device 5A
One output voltage V ₂ of the differential amplifier 16 as a control voltage of
Other output voltage V ₁ of the differential amplifier 16 respectively used as a control voltage of the variable capacitance device 5B. The output signals of the variable phase shift circuits 19a and 19B are supplied to a switch 20.
Is controlled by a burst gate pulse synchronized with the input signal a from the input terminal 21, selects one of the output signals of the color burst signal period variable phase shift circuits 19A and 19B of the input signal a, and carries the input signal a. Color signal period variable phase shift circuit 19A, 19
Select the other of the B output signals.

The output signal of the variable phase shift circuit 19A is
Only transfer amount of one corresponding to the output voltage V ₂ of the differential amplifier 16 are transferred, the output signal of the variable transfer circuit 18B also, the input signals a, according to the other output voltage V ₁ of the differential amplifier 16 The phase is shifted by the transferred amount. Therefore, the resistance value of the variable resistance value 15 is equal to the reference resistance value, and the output voltage of the differential amplifier 16 is
When V ₁ and V ₂ are equal, the transfer amounts of the output signals of the variable phase shift circuits 19A and 19B from the input signal a are equal, and the output signal v ₀ obtained from the switch 20 to the output terminal 6 is the same as the color burst signal. It has the same phase relationship as the input signal a with the carrier color signal. However, the resistance value of the variable resistor 15 is different from the reference resistance value, whereby the output voltages V ₁ , V
When ₂ are different, different transfer amount with respect to the input signal a variable phase circuit 19A, 19B output signal, Therefore, in the output signal v _i obtained at the output terminal 6, the color burst signal and the carrier chrominance signal The input signal a and the transfer relationship are different between them.

As described above, in this embodiment, the same effects as in the embodiment shown in FIGS. 1 and 2 can be obtained.

The embodiments of the present invention have been described above, but the present invention is not limited to only these embodiments. For example, in the above embodiment, the variable capacitance devices 5, 5A, and 5B are used, and these capacitance values are changed. However, as is clear from the above equation (4), the variable capacitance devices 5, 5A, and 5B Instead, a fixed capacitance device may be used, and the resistances 4, 4A, and 4B may be variable resistors, and their resistances may be changed.

In the above embodiment, the input signal a is supplied to the resistor with the non-inverted signal, and the inverted signal is supplied to the variable capacitance device. Conversely, the non-inverted signal is supplied to the variable capacitance device, and the inverted signal is supplied to the resistor. You may make it supply. However, in this case,
The phase characteristic curve is symmetric with respect to the phase characteristic curve shown in FIG. 3 with respect to the horizontal axis of the CR value.

Furthermore, although numerical values have been specifically shown above, these are merely shown for convenience of explanation.

[Effects of the Invention] As described above, according to the present invention, it is possible to change the phase between the color burst signal and the carrier color signal while maintaining the carrier color signal to which the color burst signal is added. The hue of the screen can be adjusted with a simple circuit configuration that does not require a modulation and demodulation circuit, and the color burst signal and the carrier chrominance signal are in opposite directions with respect to a phase shift amount as a reference. , The phase relationship can be changed, and the hue can be adjusted over a wide range.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a color signal processing circuit according to the present invention, FIG. 2 is an explanatory diagram of a control voltage of the variable capacitance device in FIG. 1, and FIG. 3 is an embodiment shown in FIG. FIG. 4 is a specific circuit diagram of the embodiment shown in FIG. FIG. 5 is a block diagram showing another embodiment of the color signal processing circuit according to the present invention. 1 ... input terminal, 2 ... non-inverting amplifier, 3 ... inverting amplifier, 4, 4A, 4B ... resistor, 5, 5A, 5B ... variable capacitance device, 6
... output terminal, 7 ... control voltage input terminal, 8, 8A, 8B ...
… Differential amplifier, 20… Switch.

Claims (2)

(57) [Claims] 1. A color signal processing circuit using a carrier chrominance signal to which a color burst signal is added as an input signal, a first means for outputting a non-inversion signal and an inversion signal of the input signal, and the first means. A series circuit of a resistor and a variable capacitance device connected between the output terminal of the non-inverted signal and the output terminal of the inverted signal, and the capacitance value of the variable capacitance device with respect to a predetermined reference capacitance value. A second means for changing the color burst signal period of the input signal and the carrier chrominance signal period in mutually opposite directions, and comprising a color burst in an output signal obtained from a connection point between the resistor and the variable capacitance device. Color signal processing characterized in that the relative phase relationship between the signal and the carrier color signal can be made different from the relative phase relationship between the color burst signal and the carrier color signal in the input signal. circuit. 2. A color signal processing circuit using a carrier color signal to which a color burst signal is added as an input signal, a first means for outputting a non-inverted signal and an inverted signal of the input signal, and the first means. A first series circuit of a first resistor and a first variable capacitance device connected between the output terminal of the non-inverted signal and the output terminal of the inverted signal in the first means; A second series circuit of a second resistor and a second variable capacitance device connected between the output terminal of the non-inverted signal and the output terminal of the inverted signal, and A second means for changing a capacitance value of the variable capacitance device in a direction opposite to each other with respect to a predetermined reference capacitance value; a signal obtained from a connection point between the first resistor and the first variable capacitance device; Either a second resistor or a signal obtained from a connection point of the second variable capacitance device is used as the input signal. A third means for selecting during the color burst signal period and selecting the other during the carrier chrominance signal period of the input signal, wherein the color burst signal and the carrier chrominance signal in the output signal obtained from the third means are selected. A color signal processing circuit configured to make a relative phase relationship different from a relative phase relationship between a color burst signal and a carrier color signal in the input signal.