JP3263864B2 - Brightness adjustment method and adjustment device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for adjusting brightness of a color cathode ray tube.

[0002]

2. Description of the Related Art A conventional brightness adjusting device will be described below with reference to FIG. In a color receiver having a wide video frequency band, it is difficult to increase the amplitude of the video signal, and there is no room for the power supply voltage. Therefore, it is difficult to adjust the brightness with the DC voltage component of the video signal. Therefore, as shown in FIG. 7A, in a color cathode ray tube, cathodes K _R for red, blue and blue electron beams,
K _G, red K _B, green and blue video output signals R, G, and supplies the B, cathodes K _R, K _G, to K _B, the separate control grid G _1R respectively, G _1G, G _1B is provided, and the brightness is adjusted by varying the control voltage applied to each of the grids G _1R , G _1G , and G _1B .

FIGS. 7 (B) and 7 (C) show cathodes K _R , K
_G, the video output and the grid G is respectively supplied to the K _B
Control voltages supplied to _1R , G _1G , and G _1B are shown.
Note that the beam cut-off cathode voltage E of the color cathode ray tube is
kco is the same for red R, green G, and blue B. FIG.
(B) shows the video output of each color when the white balance is maintained, and the amplitude (DRIVE) becomes smaller in the order of red, green and blue.

When adjusting the brightness, the grid G _1R ,
_Assuming that the maximum variable ranges of the control voltages applied to G _1G and G _1B are equal, when the brightness is adjusted from the minimum to the maximum, the red, green, and blue control voltages each have seven levels.
It is configured so that it can be changed in eight stages and nine stages.

[0005] In practice, the amplitude of the three-color video output rarely changes significantly, the adjustment range of brightness is not so large, and when the brightness is low, the color on the surface of the color cathode ray tube is difficult to understand. For example, the white balance collapse based on the brightness adjustment in the conventional brightness adjustment circuit did not cause much problem.

[0006]

However, with the sophistication of color receivers and the expansion of the brightness adjustment range, brightness adjustment can be performed without deteriorating the white balance regardless of the video output level of each color. The demand for brightness adjustment circuits has increased. In view of the above, the present invention provides a brightness adjustment method in which a brightness control is performed by applying each color control voltage to each color control grid provided corresponding to each color cathode to which each color video output of a color cathode ray tube is supplied. Another object of the present invention is to propose an adjustment device capable of performing brightness adjustment without deteriorating white balance regardless of the level of each color video output.

[0007]

According to a first aspect of the present invention, there are provided three cathodes of a color cathode ray tube having three cathodes and three control grids respectively corresponding to the three cathodes. Supply video signal,
In a brightness adjustment method in which control voltages of three primary colors according to brightness adjustment are supplied to three control grids, a gain coefficient of three primary colors and a contrast of three primary colors according to contrast adjustment are applied to input video signals of three primary colors, respectively. The output video signals of the three primary colors obtained by multiplying the coefficients using the first multiplication means of the three primary colors are supplied to three cathodes, respectively, and the gain coefficients of the three primary colors and the brightness of the three primary colors according to the brightness adjustment. The coefficient is multiplied by means of multiplying means for three primary colors, using first multiplying means for the three primary colors and second multiplying means for the three primary colors, respectively, and the output of the second multiplying means for the three primary colors. To the voltage,
This is a brightness adjustment method in which control voltages of three primary colors obtained by adding background voltages of three primary colors that change in accordance with background adjustment of three primary colors are supplied to three control grids.

[0008] The second invention is a three-cathode and its three
Three video output circuits for supplying output video signals of three primary colors to three cathodes of a color cathode ray tube having three control grids respectively corresponding to the three cathodes;
In a brightness adjustment circuit having three control circuits for supplying control voltages of three primary colors according to the brightness adjustment to three control grids, three video output circuits are respectively provided.
The first three primary color output video signals are obtained by multiplying the three primary color input video signals by the three primary color gain coefficients and the three primary color contrast coefficients according to the contrast adjustment, respectively.
, And three control circuits each having three gains corresponding to gain coefficients and brightness adjustment of three primary colors.
Multiplying means of three primary colors for multiplying the brightness coefficient of the primary colors, the first multiplying means of the three primary colors and the second multiplying means of the three primary colors, respectively, and the output voltage of the second multiplying means of the three primary colors And a variable DC power supply for the three primary colors that obtains a control voltage for the three primary colors by adding a background voltage for the three primary colors that changes according to the background adjustment for the three primary colors. According to a third aspect, in the brightness adjusting apparatus according to the second aspect, the first multiplying means for the three primary colors multiplies the input video signal of the three primary colors by a gain coefficient of each of the three primary colors. And a second multiplier of the three primary colors for multiplying the contrast coefficient of the three primary colors according to the contrast adjustment, and the second multiplication means of the three primary colors is dual with the first multiplier of the three primary colors, respectively. This is a brightness adjusting device including a third multiplier of three primary colors.

[0009]

According to the second aspect of the present invention, the three primary color input video signals are provided to the three primary color input video signals in accordance with the three primary color gain coefficients and the contrast adjustment, respectively, by the three primary color first multiplication means provided for the three video output circuits. The output signals of the three primary colors are obtained by multiplying the contrast coefficients of the three primary colors by the second multiplying means of the three primary colors provided in the three control circuits, respectively, according to the gain coefficient and the brightness adjustment of the three primary colors. 3
The brightness coefficients of the primary colors are multiplied, and the variable DC power supplies of the three primary colors provided in the three control circuits respectively multiply the three by three.
The control voltage of the three primary colors is obtained by adding the background voltage of the three primary colors, which changes according to the background adjustment of the three primary colors, to the output voltage of the second multiplication means of the primary colors.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.
This will be described in detail. In FIG. 1, 1R, 1G and 1B are
Red, green and blue video output circuits, respectively.
The output of each color image is the color cathode shown in FIG.
Each cathode K of the wire tube_R, K _G, K_BSupplied to 2
R, 2G and 2B are red, green and blue control circuits, respectively.
The respective color control voltages from these circuits are the same as those shown in FIG.
Each grid G of color cathode ray tube_1R, G_1G, G_1BSupplied to
You.

In the red video output circuit 1R, a red input video signal (R-VIDEO) is supplied to a multiplier M1 to change a red gain.
(R-GAIN) Multiplies that red gain voltage (coefficient) from potentiometer VR3 which generates a voltage. The multiplier M
1 is supplied to the multiplier M3, and the voltage (coefficient) of the contrast voltage from the potentiometer VR1 through the amplifier Aa, which generates a contrast (CONT) voltage (coefficient) that changes in accordance with the contrast adjustment, is supplied to the multiplier M3. The red output video signal obtained by multiplying and passing the red video signal from the multiplier M3 through the amplifier A1 is shown in FIG.
Supplied to the red cathode K _R of the color cathode ray tube of (A).

In the green video output circuit 1G, the green input video signal (G-VIDEO) is supplied to a multiplier M4 to change the green gain.
(G-GAIN) Multiply that green gain voltage (coefficient) from potentiometer VR5 to generate the voltage. The multiplier M
4 is supplied to the multiplier M6, and the voltage (coefficient) of the contrast voltage from the potentiometer VR1 through the amplifier Aa from the potentiometer VR1 that generates the contrast (CONT) voltage (coefficient) that changes in accordance with the contrast adjustment. The green output video signal obtained by multiplying the green video signal from the multiplier M6 through the amplifier A3 is shown in FIG.
Supplied to the green cathode K _G of the color cathode ray tube of (A).

The blue video output circuit 1B supplies a blue input video signal (B-VIDEO) to a multiplier M7 to change the blue gain.
(B-GAIN) Multiplies that blue gain voltage (coefficient) from potentiometer VR7 which generates a voltage. The multiplier M
7 is supplied to the multiplier M9, and the voltage (coefficient) of the contrast voltage from the potentiometer VR1 through the amplifier Aa from the potentiometer VR1 that generates the contrast (CONT) voltage (coefficient) that changes in accordance with the contrast adjustment. The blue output video signal obtained by multiplying and passing the blue video signal from the multiplier M9 through the amplifier A5 is shown in FIG.
Supplied to the blue cathode K _B of the color cathode ray tube of (A).

In the red control circuit 2R, an amplifier Ab for the brightness voltage from a potentiometer VR2 for generating a brightness voltage that changes in accordance with the brightness adjustment.
Is supplied to a multiplier M1 and a multiplier M2 which is dual with the red gain voltage (coefficient) from the potentiometer VR3. The voltage from the multiplier M2 is supplied through an amplifier A2 to a variable DC power supply VR4 that generates a red background (R-BKG) voltage that changes in accordance with the background adjustment, and the red background voltage is added. The supplied red control voltage is supplied to the control grid G _1R of the color cathode ray tube shown in FIG.

In the green control circuit 2G, an amplifier Ab of the brightness voltage from a potentiometer VR6 that generates a brightness voltage that changes in accordance with the brightness adjustment.
Is supplied to a multiplier M4 and a dual multiplier M5 to multiply the green gain voltage (coefficient) from the potentiometer VR5 described above. The voltage from the multiplier M5 is supplied to a variable DC power supply VR6 that generates a green background (G-BKG) voltage that changes in accordance with the background adjustment through an amplifier A4, and the green background voltage is added. green control voltage to the control grid G _1G of the color cathode ray tube shown in FIG. 7 (a) a.

In the blue control circuit 2B, an amplifier Ab of the brightness voltage from a potentiometer VR2 that generates a brightness voltage that changes in accordance with the brightness adjustment.
Is supplied to a multiplier M7 and a dual multiplier M8 to multiply the blue gain voltage (coefficient) from the potentiometer VR7 described above. The voltage from the multiplier M8 is supplied through an amplifier A6 to a variable DC power supply VR8 that generates a blue background (B-BKG) voltage that changes in accordance with the background adjustment, and the voltage is obtained by adding the blue background voltage. and supplies the green control voltage to the control grid G _1B of the color cathode ray tube of FIG. 7 (a).

The multipliers M1 to M9 can be considered as amplifiers, in which case the multiplier becomes a gain.

Next, referring to FIGS. 2 to 4, the operations of the video output circuit and the control circuit will be described with reference to the red video output circuit 1R.
And the red control circuit 2R as an example. Incidentally, brightness voltage is shown in FIG. 1 and FIG. 2 red video signal (R-VIDEO), the red output image signal to be supplied to the cathode K _R of the color cathode ray tube, it is supplied to the multiplier M2,
Represents a red control voltage output from the amplifier A2, and represents a red gain voltage.

To simplify the description of the operation, the multiplier M
It is assumed that the amplitude of the red video signal supplied to 1 and the voltage difference between the maximum and minimum brightness voltages from the potentiometer VR2 are both equal to 0.7V. As described above, the multipliers M1 and M2 have a dual circuit configuration. Thus, as shown in FIG. 2, since the red gain voltages supplied to the multipliers M1 and M2 are common, the amplitudes of the red output video signal and the red control voltage are 0.7 A and 0.7 A ', respectively. Here, gain A = red output video signal ÷ red video signal, gain A ′ = red control voltage ÷ brightness voltage. Therefore, the amplitudes of the red output video signal and the red control voltage are proportional. For this reason, the brightness voltage is not limited to 0.7 V, and whatever the voltage is, the red output video signal and the red control voltage have a linear relationship.

Each cathode K _R , K _G ,
Red supplied to K _B, green and blue output video signals, red, respectively, since it is multiplied by the mutually independent coefficients green and blue input video signal (gain), respective amplitudes are different from each other. However, the red, green, and blue output video signals have a linear relationship with the red, green, and blue control voltages supplied to the control grids G _1R , G _1G , and G _1B of the color cathode ray tube, respectively, as described above. Therefore, as shown in FIGS. 3A and 3B, even if the amplitudes of the red, green, and blue output video signals are different, the red, green, and blue control voltages respectively have their brightness (BRT) variable ranges (BRT). (The minimum voltage to the BRT maximum voltage) are proportional to the amplitudes of the red, green, and blue output video signals, respectively.

FIG. 4 shows FIG. 3 as a cut-off operation. Since the beam cutoff cathode voltage Ekco of the color cathode ray tube is determined by the potential difference between the voltage of the output video signal supplied to the cathode of the color cathode ray tube and the control voltage supplied to the control grid, the red, green and blue control is performed. Assuming that the black level is cut off when the voltage is the maximum BRT, the red, green, and blue output video signals are cut off at five gradations from black when the BRT is the minimum, and the red, green, and blue outputs are output. The brightness ratio of the luminance signal of the video signal is adjusted without changing the luminance ratio, and the white balance is not lost.

FIG. 5 shows a specific circuit (gain tracking type brightness adjustment circuit) of the embodiment of FIG. In FIG. 5,
Shows a portion of a red video output circuit 1R and a red control circuit 2R,
The parts of the green and blue video output circuits 1G and 1B and the green and blue control circuits 2G and 2B are not shown.

The multiplier M1 includes a differential transistor Q1,
Q2, the collector of the transistor Q1 is connected to the positive power supply, the collector of the transistor Q2 is connected to the positive power supply through the resistor R1, and the emitters of the transistors Q1 and Q2 are respectively connected through the diodes D1 and D2, respectively. The source transistor Q3 is connected to a negative power supply through a collector and an emitter and a resistor R2. The red input video signal is supplied to the base of the transistor Q3, the red gain voltage is supplied to the base of the transistor Q1 through the amplifier Aa, and the multiplying power from the collector of the transistor Q2 is supplied to the multiplier M3, and the contrast through the amplifier Aa is supplied. The voltage is multiplied.

The multiplier M2 includes a differential transistor Q7,
Q8, and the collector of the transistor Q7 is connected to the positive power supply.
The collector of the transistor Q8 passes through the resistor R5.
Connected to the positive power supply and the transistors Q7 and Q8
Mitters pass through diodes D5 and D6, respectively.
And the collector and the emitter of the current source transistor Q9.
And through a resistor R6. amplifier
The brightness voltage through Ab is the voltage of transistor Q9.
And the red gain voltage is transferred through the amplifier Aa.
The transistor Q8 is supplied to the base of the transistor Q8.
Multiplying calculation power from the collector is supplied to the variable DC power supply VR4
Is done. The base of transistor Q9 is blank during the flyback section.
Switcher SW- to complete King (BLK)
1 to the positive power supply. Transistor Q8
The collector of transistor Q10 through resistor R8.
And its emitter is negative through resistor R9.
Connected to power supply. Direct control voltage between positive and negative power supplies
Cut to adjust cutoff by shifting flow components
The series circuit of the OFF variable resistor VR4 'and the resistor R7 is connected.
The connection midpoint is connected to the base of transistor Q10.
Connected. Red system from the collector of transistor Q10
The control voltage is the red control grid G of the color cathode ray tube _1RApplied to
It is.

Next, the operation of the multiplier will be described using the multiplier M1 as an example. FIG. 6C shows the multiplier M1. First, the double-end type multiplier shown in FIG. The base input voltage of the transistors Q1 and Q is Vbe
₁ , Vbe ₂ and Vbe ₁ −Vbe ₂ = Vid ‥‥‥‥‥‥‥‥‥ (1).

The emitter current Ie ₂ of the transistor Q2 is expressed by the following equation. Ie ₂ = I ₀ / {1 + exp (Vid / h}} (2) where h = kT / q (k: Boltzmann constant, T: junction temperature, q: electron charge) Collector of transistor Q2 The relationship between the current Ic ₂ and the emitter current Ie ₂ is represented by the following equation: Ic ₂ = h _FB2 · Ie ₂ ‥‥‥‥‥‥‥‥‥‥ (3) From equations (2) and (3), The following equation is obtained: Ic ₂ = h _FB2 · I ₀ / {1 + exp (Vid / h}} (4)

The rate of change of the collector current Ic ₂ of the transistor Q2 with respect to the change of the input voltage Vid by differentiating the equation (4), obtained as follows. _{dIc 2 / dVid = (h FB2} / h) I 0 · exp (Vid / h) / {1 + exp (Vid / h} 2 = g m [Ω] ‥‥‥‥‥‥‥‥‥‥‥‥‥‥‥ ‥‥ (5) where g _m is the transconductance.

G at the operation center point (Ie ₁ = Ie ₂ )
_{If m0} is Vid → 0 in the equation (5), the following equation is obtained. g _m0 = h _FB2 · I ₀ / 4h (6) The gain G at the operation center point is expressed by the following equation. G = ΔV _od / ΔV _id = g _m0 (Rc ₁ + Rc ₂ ) = q · h _FB2 · I ₀ (Rc ₁ + Rc ₂ ) / 4kT = h _FB2 · I ₀ (Rc ₁ + Rc ₂ ) · V _id / 4h ‥ ‥‥ (7)

Accordingly, the output _Vod obtained between the collectors of the transistors Q1 and Q2 is expressed by the following equation. V _od = h _FB2 · I ₀ · (Rc ₁ + Rc ₂ ) · Vid / 4h ‥‥ (8)

FIG. 6B is obtained by converting FIG. 6A into a single-ended multiplier. In equation (7),
If Rc ₁ = 0, the following equation is obtained. V _od = h _fb2 · I ₀ · Rc ₂ · Vid / 4h ‥‥‥‥‥‥‥ (9) where h _fb2 is h _FB2 at the time of single end. That is, the output voltage V _od comprises the product of the input voltage and the constant current I _0.

Therefore, when the constant current I ₀ is replaced by a variable current source that linearly corresponds to the input video signal, the gain of the output video signal can be controlled by the DC voltage _Vid . FIG.
(C) illustrates this. Here, the constant current I ₀ is represented by the following equation. _{I 0 = (Vvideo -V BE)} / R E ‥‥‥‥‥‥‥ (10) (10) Substituting equation in expression (9) the following equation is obtained. _{V od = h FB2 · (Vvideo} -V BE) · Rc 2 · Vid / 4h · R E = C · (Vvideo -V BE) · Vid = C · Vvideo · Vid however, C is a constant. Therefore, the input video signal has a gain V
It can be seen that the signal is amplified by id and output as the output video signal _Vod .

[0032]

According to the first aspect of the present invention, the three primary colors are output to the three cathodes of a color cathode ray tube having three cathodes and three control grids respectively corresponding to the three cathodes. Supply video signal,
In a brightness adjustment method in which control voltages of three primary colors according to brightness adjustment are supplied to three control grids, a gain coefficient of three primary colors and a contrast of three primary colors according to contrast adjustment are applied to input video signals of three primary colors, respectively. The output video signals of the three primary colors obtained by multiplying the coefficients using the first multiplication means of the three primary colors are supplied to three cathodes, respectively, and the gain coefficients of the three primary colors and the brightness of the three primary colors according to the brightness adjustment. The coefficient is multiplied by means of multiplying means for three primary colors, using first multiplying means for the three primary colors and second multiplying means for the three primary colors, respectively, and the output of the second multiplying means for the three primary colors. To the voltage,
The control voltages of the three primary colors obtained by adding the background voltages of the three primary colors, which change in accordance with the background adjustment of the three primary colors, are supplied to the three control grids, respectively. Irrespective of this, the brightness can be adjusted without breaking the white balance, and the gain adjustment and the contrast adjustment in the output video signals of the three primary colors supplied to the three cathodes of the color cathode-ray tube and the three cathodes are superimposed. Since the gain adjustment and the brightness adjustment at the control voltages of the three primary colors supplied to the three control grids respectively corresponding to the three control grids are performed by using the multiplying means, respectively, without adversely affecting other circuits, Each adjustment and superimposition can be performed, and the background voltage of the three primary colors can be controlled at the control voltage of the three primary colors. Brightness adjustment method which can superimpose be adjusted can be obtained. According to the second aspect of the present invention, output video signals of three primary colors are supplied to three cathodes of a color cathode ray tube having three cathodes and three control grids respectively corresponding to the three cathodes. In a brightness adjustment circuit having three video output circuits and three control circuits for supplying control voltages of three primary colors according to brightness adjustment to three control grids, three video output circuits each have three primary colors. Are multiplied by the gain coefficients of the three primary colors and the contrast coefficients of the three primary colors in accordance with the contrast adjustment, respectively, to provide first primary color multiplication means for obtaining an output video signal of the three primary colors. Multiplying means for multiplying the control circuit by the gain coefficient of the three primary colors and the brightness coefficient of the three primary colors according to the brightness adjustment; The output voltage of the second multiplying means of the three primary colors, each of which is dual with the first multiplying means, and the output voltage of the second multiplying means of the three primary colors, the background voltage of the three primary colors changing according to the background adjustment of the three primary colors And a variable DC power supply for the three primary colors that obtains control voltages for the three primary colors is provided, so that the brightness can be adjusted without breaking the white balance regardless of the level of the video output of each color. In addition, superimposition of gain adjustment and contrast adjustment in output video signals of three primary colors supplied to the three cathodes of the color cathode ray tube, and control voltages of the three primary colors supplied to three control grids respectively corresponding to the three cathodes Since the gain adjustment and the brightness adjustment are both performed using the multiplication means, adverse effects on other circuits may occur. Ku, can be performed each adjusting and superimposing, also in the control voltage of the three primary colors, it is possible to obtain a brightness adjustment device that can also superimposed background adjustment of the three primary colors. It should be noted that the same effect as that of the second invention can be obtained by the third invention.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a waveform chart of an embodiment (1).

FIG. 3 is a waveform diagram of an embodiment (2).

FIG. 4 is a waveform diagram of an embodiment (3).

FIG. 5 is a circuit diagram showing a specific circuit of the embodiment.

FIG. 6 is a circuit diagram showing a multiplier used in the embodiment.

FIG. 7 is a waveform diagram of a conventional example.

[Explanation of symbols]

K _R, K _G, K _B cathode G _1R, G _1G, G _1B grid 1R, 1G, 1B video output circuit 2R, 2G, 2B control circuit M1~M9 multiplier VR1, VR2 potentiometer A1 to A6, Aa, Ab amplifier

Claims (3)

(57) [Claims] 1. A color cathode ray tube comprising three cathodes and three control grids respectively corresponding to the three cathodes, the three cathodes being supplied with output video signals of three primary colors, respectively. In a brightness adjustment method for supplying a control voltage of three primary colors to three control grids according to brightness adjustment, a gain coefficient of three primary colors and a contrast coefficient of three primary colors according to contrast adjustment are respectively applied to input video signals of three primary colors. Are respectively multiplied by using first multiplication means of three primary colors, and the output video signals of the three primary colors are supplied to the three cathodes, respectively, and the three primary colors are adjusted according to the gain coefficient and brightness adjustment.
The brightness coefficient of the primary colors is multiplied by three primary colors, and each of the three primary colors is dual with the first multiplication means of the three primary colors.
The multiplication is performed by using the second multiplication means of the primary colors, and the output voltage of the second multiplication means of the three primary colors is added to the background voltage of the three primary colors which changes according to the background adjustment of the three primary colors. And a control voltage for the three primary colors is supplied to each of the three control grids. 2. A three-video system for supplying output video signals of three primary colors to the three cathodes of a color cathode ray tube having three cathodes and three control grids respectively corresponding to the three cathodes. A brightness adjustment circuit having an output circuit and three control circuits for supplying control voltages of three primary colors according to brightness adjustment to the three control grids, wherein each of the three video output circuits has three primary color inputs. A first multiplication means for three primary colors is provided to multiply the video signal by a gain coefficient of the three primary colors and a contrast coefficient of the three primary colors according to the contrast adjustment to obtain an output video signal of the three primary colors. The three primary color multiplying means for multiplying the control circuit by the three primary color gain coefficients and the three primary color brightness coefficients according to the brightness adjustment. The output voltages of the first multiplying means of the three primary colors and the second multiplying means of the three primary colors, respectively, are changed in accordance with the background adjustment of the three primary colors. 3
A brightness adjusting device, comprising: a variable DC power supply of three primary colors for obtaining a control voltage of the three primary colors by adding a background voltage of the primary colors. A first multiplier for multiplying the input video signal of each of the three primary colors by a gain coefficient of each of the three primary colors; and a first multiplier for the three primary colors and a three primary color multiplier corresponding to the contrast adjustment. A second multiplier of three primary colors for multiplying a contrast coefficient; and a second multiplier of the three primary colors, a third multiplier of the three primary colors each being dual with the first multiplier of the three primary colors. 3. The brightness adjusting device according to claim 2, comprising a multiplier.