JP3271089B2 - Television equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television apparatus for reproducing a video signal.

[0002]

2. Description of the Related Art Conventionally, in television broadcasting, so-called γ correction is performed so that an output signal is proportional to the (1 / γ) power of an input signal, as shown in a graph on the left side of FIG. . This is because the relationship between the input signal of a CRT (cathode ray tube) used in many television devices and the display luminance is such that the luminance is proportional to the γ-th power of the input signal, as shown in the middle graph in FIG. Non-linearity (γ characteristic)
It is because it has. As a result of this γ correction, as shown in the right graph in FIG. 7, a linearity proportional to the input signal is secured in the display luminance on the CRT.

However, the gamma characteristic of a CRT is
It differs depending on the characteristics and the like of the phosphor constituting the RT. Further, in a television device configured to have a display device other than a CRT, such as an LCD (Liquid Crystal Display Device), instead of a CRT, a light emission characteristic and a transmission characteristic with respect to an input signal are different from γ characteristics of the CRT. It has become.

For this reason, conventionally, a television apparatus is provided with a gamma compensation circuit, and the gamma compensation circuit is configured to electrically compensate for the linearity of a display luminance with respect to an input signal as shown in FIG. Have been proposed.

An amplifier used for amplifying a primary color signal sent to a CRT in the above-mentioned television apparatus is configured as a variable gain amplifier as shown in FIG. That is, this amplifier has four transistors Q ₁ , Q ₂ , Q ₃ , and Q ₄ . The input signal Vin, the bias voltages _{V 1} is applied. The transistor _{Q 1} represents a NPN type, the input signal Vin
Is input to the base terminal. The transistor _{Q 1} is,
Is connected to the output terminal of the diode D ₁ to the collector terminal, a current source 2I ₁ to the emitter terminal via the resistor R ₁ is connected. The input terminal of the diode D _1, the bias voltage V ₂ is applied. Further, the transistor Q
₂ is an NPN, the bias voltage _{V 1} is applied to the base terminal. The transistor Q ₂ is the output terminal of the diode D ₂ to the collector terminal is connected, the current source 2I ₁ is connected via a resistor R ₁ to the emitter terminal. Input terminal of the diode D ₂ is applied to the bias voltage V _2.

[0006] Then, the transistor Q _3, the base terminal is connected to the collector terminal of the transistor Q _2. The transistor Q ₃ are applied a bias voltage V ₃ to the collector terminal, the current source 2I ₂ to the emitter terminal
Is connected. Further, the transistor Q ₄ are, the base terminal connected to the collector terminal of the transistor Q _1. The transistor Q ₄ are, is applied a bias voltage V ₃ collector terminal via the resistor R _2, the current source 2I ₂ is connected to the emitter terminal. The collector terminal of the transistor _{Q 4} are, the capacitor _{C 1}
And an output terminal from which the output signal Vout is taken out.

In this amplifier, the transistor Q
₁ is supplied with the input signal Vin, and the transistor Q
When ₁ and current _{i 1} by the resistance _{R 1} between the transistor _{Q 2 flows, i 1 = Vin / R 1} ······ ( Equation 1) is satisfied. Therefore, each of the diodes D ₁ and D ₂
Are I ₁ + i ₁ and I ₁ −i ₁ , respectively. Further, the output current _{i 2} that is defined as Vout ₌ i 2 · _{R 2,} current flowing through the respective transistors _Q 3, _{Q 4, respectively,} the _{I 2 + i 2, I 2} -i 2.

[0008] Here, V _BE of the transistor is V _BE
= V _T · In (Ic / Is)
_Assuming that V _BE of each of the transistors Q ₁ , Q ₂ , Q ₃ , Q ₄ is V _B1 , V _B2 , V _B3 , V _B4 ,
Hereinafter _{As, V B1 + V B4 = V} B2 + V B3 V T · In (I 1 + i 1 / Is) + V T · In (I 2 -i 2 / Is) = V T · In (I 1 -i 1 / Is) + _VT · In (I ₂ + i ₂ / Is) (I ₁ + i ₁ ) (I ₂ −i ₂ ) = (I ₁ −i ₁ ) (I ₂ + i ₂ ) i ₁ · I ₂ = i ₂ · I ₁ i ₂ = i ₁ · I ₂ / I ₁ (Expression 2) By substituting this Expression 2 into the above Expression 1, the following can be obtained: i ₂ = (Vin / R ₁ ) · I ₂ / I ₁ Become. When Vout is obtained, the following input / output characteristics are obtained: Vout = i ₂ · R ₂ = Vin · I ₂ · R ₂ / (I ₁ · R ₁ ) = A · Vin (Equation 3) Here, A is defined as input / output characteristics. In this amplifier, if you want a gain variably may be changed current i _2.

[0009]

FIG. 9 shows a television apparatus having a gamma compensation circuit as described above, particularly a so-called three-tube video projector apparatus and an apparatus having an LCD as a display device. As shown,
The γ curves for the three primary colors of R (red), G (green), and B (blue) may not coincide with each other. In such a case, even if similar gamma compensation is performed for the three primary colors, as shown in FIG. 10, the linearity of the display luminance for each primary color with respect to the input signal cannot be ensured. Therefore, as shown in the graph on the right side in FIG. 10 showing the characteristics of the display luminance after the γ compensation with respect to the input signal, the white balance is adjusted at the cutoff adjustment point (point B) and the highlight adjustment point (point C). Even if the display luminance of each primary color is adjusted so as to be good, in the intermediate luminance part,
Good white balance cannot be obtained.

Further, in the amplifier as described above, there is a possibility that a good output signal may not be obtained with respect to the frequency characteristic (f characteristic) and the S / N ratio (signal noise ratio). That is, the frequency characteristic of the output signal is dominated by the parasitic capacitance C ₁ is connected to the collector terminal of the transistor Q _4. This parasitic capacitance C ₁ is determined by the additional resistance R ₂ and f _CO
A low-pass filter having a cutoff frequency of = 1 / (2πC ₁ R ₂ ) is formed, which is a factor of deteriorating the frequency characteristics.

As for the S / N ratio, it is necessary to consider shot noise due to emitter current and thermal noise due to base resistance as transistor noise. That is, these noise sources are equivalently output terminals (cathodes) of the diodes D ₁ and D ₂ as shown in FIG.
And the base terminal of each of the transistors Q ₃ and Q _4.
Degrades the N ratio.

Accordingly, the present invention has been proposed in view of the above-mentioned circumstances. For example, good γ compensation is performed for primary color signals such as R (red), G (green), and B (blue). In addition, an object of the present invention is to provide a television device capable of achieving good white balance from a cutoff level to a highlight level by performing amplification with good frequency characteristics and S / N ratio.

[0013]

SUMMARY OF THE INVENTION In order to solve the above problems and achieve the above objects, a television apparatus according to the present invention is provided corresponding to a primary color signal generated from a received or input signal. A gamma compensation circuit for performing gamma compensation on a corresponding primary color signal, and an amplifier provided corresponding to each primary color signal that has passed through the gamma compensation circuit, and the amplifier is supplied with the corresponding primary color signal. An amplification unit for amplifying the primary color signal; and an addition unit for adding and outputting the primary color signal and the primary color signal amplified by the amplification unit, and amplifying one corresponding primary color signal. Things.

[0014]

In the television device according to the present invention, since the gamma compensation circuit provided corresponding to the primary color signal performs gamma compensation on one corresponding primary color signal, the gamma characteristic differs for each primary color signal. Even so, an amplifier provided for each primary color signal performs optimal γ compensation, and an amplifier provided corresponding to the primary color signal is provided with an amplification unit to which a corresponding primary color signal is input and amplifies the primary color signal. An adding section for adding and outputting the primary color signal and the primary color signal amplified by the amplifying section, and amplifying the corresponding primary color signal, so that good frequency characteristics and S / N ratios are obtained for each primary color signal. , A good white balance can be realized over the highlight level from the cutoff level.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

[0016] As shown in FIG.
It has a tuner 2 for receiving broadcast radio waves such as VHF, UHF and BS via an antenna 1. The broadcast wave received by the tuner 2 is converted into an intermediate frequency by the tuner 2, sent to a video detection circuit 3, and demodulated into a composite video signal by the video detection circuit 3. This composite video signal is sent to the video switch 4. In addition to the composite video signal, a video signal sent from a recording / reproducing device such as a video tape recorder or a video disk player is input to the video switch 4 via a video input terminal.

Each video signal input to the video switch 4 is selected by the video switch 4, and the selected video signal is sent to a Y / C separation circuit 5. The Y / C separation circuit 5 separates the sent video signal into a luminance signal Y and a chroma signal C, sends the luminance signal Y to a luminance signal processing circuit 6, and sends the chroma signal C to a color demodulation circuit 7. send. The luminance signal Y is subjected to signal processing such as sharpness processing and DC transmission rate conversion in the luminance signal processing circuit 6 and then sent to an RGB matrix circuit 8. The chroma signal C is converted to BY, R by the color demodulation circuit 7.
The signal is converted into a color difference signal of −Y and sent to the RGB matrix circuit 8.

The RGB matrix circuit 8 generates three primary color signals R, G, B of red, green, and blue from the sent luminance signal Y and color difference signals BY, RY, and sends them to the gamma compensation circuit 9. . The gamma compensation circuit 9 is a circuit that performs uniform gamma compensation for each primary color signal.

The gamma compensation is performed to ensure such linearity when the display luminance of a display device such as a CRT is not linear with respect to an input signal only by so-called gamma correction in television broadcasting. Electrical processing. That is, the γ characteristic of the CRT
Since it differs depending on the characteristics and the like of the phosphor constituting T, unless γ compensation is performed, the linearity of the display luminance with respect to the input signal cannot be ensured.

The primary color signals subjected to the gamma compensation by the gamma compensation circuit 9 are amplified by a CRT drive circuit 10 and sent to a CRT 11 which is a video display device.

Then, in the television device according to the present invention, as shown in FIG. 2, instead of the γ compensation circuit 9, a γ compensation is performed for only the red primary color signal R.
A color γ compensation circuit 12 including a dγ compensation circuit 12R, a Green γ compensation circuit 12G for performing γ compensation only for the green primary color signal G, and a Blue γ compensation circuit 12B for performing γ compensation only for the blue primary color signal B is provided. . Each gamma compensation circuit 1 constituting the gamma compensation circuit 12 for each color
As shown in the center graph in FIG. 11, 2R, 12G, and 12B have different compensation characteristics according to the γ characteristics of the phosphors of the corresponding colors among the phosphors for each color constituting the CRT 11. Perform gamma compensation.

That is, in this television device, the gamma characteristic of each color phosphor in the CRT 11 is
As shown in FIG. 9, even if they do not match each other, FIG.
As shown in the middle graph, gamma compensation can be performed for each of the three primary colors by individual compensation characteristics. Therefore, as shown in the right graph of FIG. Linearity can be ensured. Therefore, as shown in the graph on the right side of FIG. 11 showing the characteristics of the display luminance after the γ compensation with respect to the input signal, the primary colors are adjusted so that the white balance is good at the cutoff adjustment point and the highlight adjustment point. If the display luminance of the signal is adjusted, a good white balance can be obtained even in the intermediate luminance part.

[0023] The television device according to the present invention comprises:
As shown in FIG. 3 and FIG. 4, both the γ compensation circuit 9 and the color-specific γ compensation circuit 12 may be provided. In this case, the color-specific compensation circuit 12 may be interposed between the gamma compensation circuit 9 and the CRT drive circuit 10 as shown in FIG. 3, or as shown in FIG. ,
A connection may be made between the RGB matrix circuit 8 and the γ compensation circuit 9. Also in these cases, gamma compensation can be performed for the three primary colors by individual compensation characteristics.

Further, in this television device, as shown in FIGS. 5 and 6, the primary color signals R,
A gamma compensation circuit for performing gamma compensation may be provided for only one or two of G and B. In this case, as shown in FIG. 5, it is not necessary to use the γ compensation circuit 9 for performing uniform γ compensation for each of the primary color signals, and as shown in FIG. 6, the γ compensation circuit 9 is used together. May be.

That is, in the example shown in FIG. 5, each primary color signal R,
Of the G and B, the red primary color signal R and the green primary color signal G are sent to the CRT drive circuit 10, and only the blue primary color signal B is sent to the Blue γ compensation circuit 12B. This B
The blue γ compensation circuit 12B performs γ compensation only on the blue primary color signal B and sends the result to the CRT drive circuit 10. Further, in the example shown in FIG.
The red primary color signal R and the green primary color signal G are sent to the CRT drive circuit 10 among the primary color signals R, G, and B which have been uniformly compensated for γ by the
This is sent to the lue compensation circuit 12B. The Blue γ compensation circuit 12B further performs γ compensation only on the blue primary color signal B and sends it to the CRT drive circuit 10.

Note that the television device according to the present invention
The present invention is not limited to the one having the CRT 11 as shown in the above-described embodiment.
The CRT 11 may be replaced by a so-called three-tube video projector including three single-color projectors.

The amplification of the primary color signals in the CRT drive circuit 10 of the television apparatus according to the present invention is performed separately for each primary color signal by an amplifier. That is, in the CRT drive circuit 10,
The amplifier is provided in three sets corresponding to the respective primary color signals.

As shown in FIG. 12, the amplifier is supplied with an input signal Vin which is the primary color signal, and has an amplifier 13 for amplifying the input signal Vin. And
In this amplifier, the input signal Vin is also sent to the adder 14. The adder 14 is supplied with an amplified signal that has been amplified and output from the amplifier 13. The adder 14 adds the input signal Vin and the amplified signal to each other and outputs the result as an output signal Vout.

In this amplifier, assuming that the gain in the amplifying section 13 is B, the output signal Vout can be expressed by the following equation: Vout = (1 + B) · Vin (4)

As shown in FIG. 14, the amplifier comprises first to seventh seven transistors Q ₁ , Q ₂ , Q
_{3, Q} 4, _{Q 5,} can be constituted by using a _Q 6, Q _7. The input signal Vin includes a first bias voltage V
₁ is applied. The first transistor _{Q 1} is, NP
An N-type input signal Vin is input to a base terminal. Transistor to Q ₁ first, the output terminal of the first diode D ₁ is connected to the collector terminal, a first current source 2I ₁ via a twelfth resistor R ₁ is connected to the emitter terminal. The input terminal of the first diode D _1,
The second bias voltage V ₂ is applied. Further, the second transistor Q ₂ are a NPN type, said first bias voltage V ₁ is applied to the base terminal. Transistor Q ₂ of the second, the output terminal of the second diode D ₂ is connected to the collector terminal, an emitter terminal first
Current source 2I ₁ the first through the resistor R ₁ of is connected. Above the second diode D ₂ input terminals, the second bias voltage V ₂ is applied.

[0031] Then, the transistor _{Q 3} of the third,
Base terminal is connected to the second collector terminal of the transistor Q _2. Transistor _{Q 3} of the third,
The collector terminal and the base terminal of the fifth transistor Q ₅ is connected to the collector terminal, a second current source 2I ₂ is connected to the emitter terminal. The fifth transistor Q
₅ through a _third resistor R3.
Bias voltage V ₃ is applied. In addition, the fourth
Transistor Q ₄ of the base terminal is connected to the collector terminal of the first transistor Q _1. The transistor Q ₄ are, are applied to the third bias voltage V ₃ via the second resistor R ₂ to the collector terminal, the second current source 2I ₂ is connected to the emitter terminal.

The amplifying unit 13 is configured by such a configuration including the _{first to} fourth transistors Q ₁ , Q ₂ , Q ₃ , and Q ₄ .

[0033] The base terminal of the transistor Q ₅ of the fifth is connected to the base terminal of the transistor Q ₆ in the sixth. Transistor Q ₆ in the sixth, the emitter terminal via a fourth resistor to the third bias voltage V
₃ , the collector terminal is an output terminal from which the output signal Vout is taken out. Further, the sixth to the collector terminal of the transistor Q ₆ is of, via a resistor R ₅ of the fifth, the emitter terminal of the seventh transistor Q ₇ is connected. Transistor Q ₇ in the seventh, the input signal Vin is supplied to the base terminal, a collector terminal is grounded.

As described above, the seventh transistor Q ₇
The adding section 14 is configured by the configuration including the above.
That is, in this amplifier, flows to the output current i ₂ is the fifth resistor R ₅ by a current mirror circuit consisting of transistors Q _5, Q ₆ of the fifth and sixth of the amplifier unit 13. The fifth resistor R _5, similar to the resistor R ₂ in the conventional amplifier shown in FIG. 15, and has a load resistance role. Therefore, when R ₂ in the above (Equation 3) is replaced with R ₅ , the gain of the amplifier 13 is obtained. Then, the input signal Vin is passed through a buffer transistor Q ₇ of the seventh, is output at the original levels, the fifth through the resistor R _5, and is summed with the output of the amplifier unit 13 the output signal Vout.

A = 1 + B B = A−1 (Equation 5) holds. Therefore, the gain in the amplifier 13 of this amplifier may be smaller by -1 than the conventional amplifier. For example, if the gain of the whole amplifier is 2,
The gain of the amplifier 13 is 1.

[0036] Thus, in this amplifier, it is possible to lower the second resistance value of the resistor _{R 2} is a factor that determines the gain, cut-off frequency of the amplifier unit _{13 f CO = 1 / (2πC} 1 R ₁ ) can be raised. That is, the frequency characteristics are improved.

Considering the S / N ratio, the noise source in this amplifier is equivalently equivalent to the output terminals of the first and second diodes D ₁ and D ₂ and the noise source as shown in FIG. The noise sources V _N1 , V _N2 , V _N3 , V _N3 are connected to the base terminals of the third and fourth transistors Q ₃ , Q ₄ , respectively.
_N4 will be present. These noise sources V _N1 ,
_Assuming that a value obtained by geometrically averaging V _N2 , V _N3 , and V _N4 is V _N, and a noise level in the output signal Vout is V _N0 , V _N0 = V _N · R ₂ / 2r _E (equation) 6) Here, r _E is the third and fourth transistors Q
_3, the emitter resistance of _{Q 4.} Here, _assuming that the noise level in this amplifier is V _N0 ′, the amplification unit 1
Since the gain B of _No. 3 is A (the gain of the conventional amplifier) -1, from the above (Equation 6), V _N0 ′ = V _N0 (A-1) / A (Equation 7) ). That is, the noise level has been reduced.

In this amplifier, since the adder 14 is constituted by a resistance matrix, no noise is generated in the adder 14, and the noise level of the entire amplifier becomes _VNO 'described above. Therefore, in this amplifier, the noise level when the output signal Vout is constant is reduced, and the S / N ratio is improved.

The amplifier is connected to each of the current sources I ₁ ,
Not an I ₂ can only be used as a variable gain amplifier as a variable, these current sources I _1, I ₂ as a fixed, may also be used as a constant-gain amplifier.

[0040]

As described above, in the television apparatus according to the present invention, since the gamma compensation circuit provided corresponding to the primary color signal performs gamma compensation on one corresponding primary color signal, each primary color signal Even if the γ characteristics are different for each,
Optimum γ compensation is performed on each of the primary color signals, and an amplifier provided corresponding to the primary color signal is provided with an amplifying section which receives a corresponding primary color signal and amplifies the primary color signal, and the primary color signal and the amplification. And an addition unit for adding and outputting the primary color signals amplified by the unit, and amplifying the corresponding primary color signal, so that good frequency characteristics and S / N ratio are amplified for each primary color signal. And a good white balance over the highlight level than the cutoff level.

That is, according to the present invention, good γ compensation is performed for primary color signals such as R (red), G (green), B (blue), and the frequency characteristics and the S / N ratio are good. By performing the amplification, it is possible to provide a television device capable of achieving a good white balance from a cutoff level to a highlight level.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a television device.

FIG. 2 is a block diagram illustrating a configuration in the vicinity of a color-specific γ compensation circuit that is a main part of the television device according to the present invention.

FIG. 3 is a block diagram showing an example in which a color-dependent γ compensation circuit, which is a main part of the television device according to the present invention, is provided in a different part from the example shown in FIG. 2;

FIG. 4 is a block diagram illustrating a main part of an example in which the television device according to the present invention is configured using a conventional gamma compensation circuit together.

FIG. 5 is a block diagram showing an example in which a television apparatus according to the present invention is provided with a gamma compensation circuit for only one primary color signal.

FIG. 6 is a block diagram showing an example in which a television apparatus according to the present invention is configured using both a gamma compensation circuit for only one primary color signal and a conventional gamma compensation circuit.

FIG. 7 is a graph illustrating the principle of gamma correction performed in broadcast radio waves.

FIG. 8 is a graph illustrating the principle of gamma compensation performed in a television device.

FIG. 9 is a graph illustrating a difference in γ characteristics of each color phosphor in a CRT of a television device.

FIG. 10 is a graph illustrating a problem that occurs when γ compensation is uniformly performed on each color primary color signal.

FIG. 11 is a graph illustrating the principle of gamma compensation in the television device according to the present invention.

FIG. 12 is a block diagram illustrating a configuration of an amplifier according to the present invention.

FIG. 13 is an equivalent circuit diagram showing a position of a noise source in the amplifier.

FIG. 14 is a circuit diagram showing a configuration of an amplifier according to the present invention.

FIG. 15 is a circuit diagram showing a configuration of a conventional amplifier.

[Explanation of symbols]

9 γ compensation circuit, 10 CRT drive circuit, 11 C
RT, 12 color γ compensation circuit, 12R Red γ compensation circuit, 12G Green γ compensation circuit, 12BB Blue γ
Compensation circuit, 13 amplifier, 14 adder

Continuation of the front page (56) References JP-A-4-269078 (JP, A) JP-A-4-114591 (JP, A) JP-A-50-27458 (JP, A) JP-A-61-295786 (JP) , A) JP-A-4-287592 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 9/44-9/78

Claims (1)

(57) [Claims] 1. Generation from a received or input signal
One primary color signal provided corresponding to the primary color signal
Comprising a γ compensation circuit for performing γ compensation for items, and an amplifier provided corresponding to each primary color signal subjected to the γ compensation circuit, the amplifier, one primary color signals corresponding is input amplifying the primary color signals primary color signal amplified by the amplifying unit and the raw color signal and amplifying unit adds to the have an addition unit for outputting, that intends rows amplified for the corresponding one primary color signal JP to
Television apparatus according to symptoms.