JP2001197397A - Video display device and video display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video display device and a video display method, which can automatically correct the change of luminance in a cathode ray tube and by which a service man does not need to repair it. SOLUTION: The device is provided with a cathode ray tube 14 having plural grids, a luminance setting change means 20 changing the setting state of luminance in the cathode ray tube 14 by the operation of an operator, a display operation means 70 for displaying a luminance setting value changed by the setting change of luminance on the cathode ray tube 14, a luminance setting value holding means 100 holding the luminance setting value changed by the change of the setting state of luminance by the luminance setting change means 20 and a control means 80 detecting whether a state where the luminance setting value becomes a value out of a prescribed range elapses for prescribed time, judging whether the luminance correction of prescribe quantity is required from a detection result, controlling the application voltage of the cathode ray tube 14 to a second grid, correcting luminance and changing the luminance setting value in a direction opposite to the correction of luminance so as to cancel luminance correction by the control of application voltage to the second grid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device and an image display method used for, for example, a television receiver or a monitor device of a computer.

[0002]

2. Description of the Related Art A cathode ray tube as an image display unit of an image display device is used as a television receiver or a monitor device for a computer, and has a second cathode. As a means for avoiding the drift phenomenon of the luminance and the white balance of the cathode ray tube of this kind, a control circuit is configured such that a cathode current at a prescribed signal (for example, a pedestal period) becomes a constant value, and a so-called signal side cathode is formed. It is widely performed to change the offset voltage of the above voltage. FIG. 7 shows an example of a composite video signal in a normal cathode ray tube. This composite video signal is between the 220 V line indicating the black level side and the 0 V line indicating the white level side. In this composite video signal, the horizontal synchronizing signal S1 is output, for example, every 15.75 kHz. Horizontal synchronization signal S
1, there is a pedestal period t indicating a black signal level, and there is a video signal S2 between the horizontal synchronization signals S1.
In such a composite video signal, there is a horizontal blanking period t3 as a period sandwiching the horizontal synchronization signal S1. When the composite video signal S approaches the white level side by changing the offset voltage of the voltage of the cathode, the video displayed on the screen causes a so-called blackout state, and when the composite video signal S moves to the black level side, A so-called blackout phenomenon occurs in the image.

[0003]

When the cathode ray tube is used for a long period of time, the cathode ray tube is oxidized due to a change over time, and the amount of emission of the electron beam is reduced, so that the screen becomes dark. In many cases, the DC (direct current) level on the black side is automatically adjusted as this compensation. However, in this case, the dynamic range of the RGB output circuit is compressed, and the composite video signal S falls to the white level side, and the image is likely to be overexposed. There is a disadvantage that. When such a phenomenon occurs, it is necessary for the repairing service technician to repair the television receiver and the monitor device of the computer. It is necessary to modify the register value to adjust the cathode voltage using
There is a problem that it takes man-hours and time. Therefore, an object of the present invention is to solve the above-mentioned problems, and to provide a video display device and a video display method capable of automatically correcting a change in luminance in a cathode ray tube and requiring no repair by a serviceman. .

[0004]

According to the present invention, there is provided a cathode ray tube having a plurality of grids, a brightness setting changing means for changing a setting state of brightness in the cathode ray tube by an operation of an operator, and the brightness setting means. Display operation means for displaying the luminance setting value changed by the setting change on the cathode ray tube; and a luminance setting value for holding the luminance setting value changed by the change of the luminance setting state by the luminance setting changing means. Holding means for detecting whether a state in which the luminance set value has become a value outside a predetermined range has passed for a predetermined time, and judging that a predetermined amount of luminance correction is necessary based on the detection result; The luminance applied to the second grid is controlled by controlling the voltage applied to the second grid, and the luminance setting value is changed in the opposite direction to the luminance correction to control the applied voltage to the second grid. And control means for canceling the correction,
A video display device comprising:

According to the first aspect, the luminance setting change means changes the luminance setting state of the cathode ray tube by an operation of an operator. The display operation means is for displaying the luminance set value changed by the change of the luminance setting on the video display unit. The brightness setting value holding unit holds the brightness setting value changed by changing the setting state of the brightness by the brightness setting changing unit. The control means detects whether a predetermined time has elapsed from a state in which the luminance setting value is out of the predetermined range, and when it is determined from the detection result that a predetermined amount of luminance correction is necessary, the control to the second grid of the cathode ray tube is performed. By controlling the applied voltage, the luminance is corrected by this control. In addition, the control means cancels the luminance correction by controlling the voltage applied to the second grid by changing the luminance setting value in a direction opposite to the luminance correction.

[0006] Accordingly, when a predetermined time has elapsed from the state where the luminance setting value is out of the predetermined range, the control means determines from the detection result that the luminance setting is not in a good state and requires a predetermined amount of luminance correction. Then, the voltage applied to the second grid of the cathode ray tube is automatically controlled. When a predetermined amount of luminance correction is performed by controlling the voltage applied to the second grid in this way, the predetermined amount of luminance correction is rewritten to a new luminance setting value. The luminance correction by the control of the second grid voltage is canceled by changing the luminance setting value. By doing so, a new luminance setting state in which a predetermined amount of luminance correction has been performed by control can be displayed on the cathode ray tube. For example, after that, the user can change the desired luminance setting to the cathode ray tube after the predetermined amount of correction is performed. It can be performed within the range of the displayed luminance display. Therefore, even if the user tries to adjust the luminance, the dissatisfaction or stress that the luminance display cannot reach to 95% because the luminance display cannot be adjusted is reduced or eliminated.

Accordingly, the control means automatically controls the second grid voltage, so that there is no need for a service person to remove the cabinet of the video display device and make adjustments. Further, since such a change over time of the cathode ray tube can be relieved, the production yield of the cathode ray tube is improved, the number of steps for inspecting the cathode ray tube is reduced, or an aging step for finding a defective cathode ray tube becomes unnecessary.

According to a second aspect of the present invention, in the video display device according to the first aspect, the control of the voltage applied to the second grid is performed by transmitting data corresponding to the predetermined amount of luminance correction to be corrected. The data transmitted from the bus and the internal bus are performed through a conversion unit that performs digital-to-analog conversion.

In the present invention, the control of the voltage applied to the second grid is performed via an internal bus for transmitting data corresponding to a predetermined amount of luminance correction to be corrected. In this case, the data transmitted from the internal bus is subjected to digital-to-analog conversion, so that a voltage applied to the second grid is supplied.

According to a third aspect of the present invention, in the video display device according to the first aspect, the brightness setting change unit is disposed on a front side of a housing of the video display device or on a remote control transmitter side.

According to a fourth aspect of the present invention, in the video display device according to the second aspect, the setting state of the luminance is displayed for a predetermined time in a partial area of the cathode ray tube.

According to a fifth aspect of the present invention, the luminance setting state of the cathode ray tube is changed by an operation of an operator, and the luminance set value changed by the change of the luminance setting is displayed on the cathode ray tube, and the luminance setting is performed. A video display method configured to retain a luminance set value changed by a change of the luminance setting state by a change unit, wherein a state in which the luminance set value has become a value outside a predetermined range has elapsed for a predetermined time. A time detecting step of detecting whether or not the correction has been performed, and a voltage controlling step of performing a correction of the luminance by controlling a voltage applied to the second grid of the cathode ray tube by determining that a predetermined amount of luminance correction is necessary based on the detection result. A luminance operation step of changing a luminance setting value in a direction opposite to the luminance correction to cancel luminance correction by controlling a voltage applied to the second grid. It is a video display method.

According to a fifth aspect of the present invention, when a predetermined time has elapsed from a state where the luminance set value is out of the predetermined range, it is determined from the detection result that the luminance setting is not in a good state and a predetermined amount of luminance correction is required. Thus, the second grid voltage of the cathode ray tube is automatically controlled. When a predetermined amount of luminance correction is performed by controlling the voltage applied to the second grid in this manner, the luminance correction state of the predetermined amount is rewritten to a new luminance setting value. By changing the luminance setting value, the luminance correction by controlling the voltage applied to the second grid is canceled. By doing so, a new luminance setting state in which a predetermined amount of luminance correction has been performed by the control can be displayed on the cathode ray tube. For example, the video display unit after the user has corrected the desired luminance setting by the predetermined amount Can be performed within the display range of the luminance displayed on the screen. Therefore, even if the user tries to adjust the luminance, the dissatisfaction or stress that the luminance display cannot reach to 95% because the luminance display cannot be adjusted is reduced or eliminated.

[0014] Thus, since the control of the voltage applied to the second grid is automatically performed, there is no need for a serviceman to remove the cabinet of the video display device and make adjustments. Further, since such a change over time of the cathode ray tube can be relieved, the production yield of the cathode ray tube is improved, the number of steps for inspecting the cathode ray tube is reduced, or an aging step for finding a defective cathode ray tube becomes unnecessary.

According to a sixth aspect of the present invention, in the video display method according to the fifth aspect, the control of the voltage applied to the second grid is performed by transmitting data corresponding to the predetermined amount of luminance correction to be corrected. The data transmitted from the bus and the internal bus are subjected to digital-analog conversion. In the sixth aspect, the control of the second grid voltage is performed via an internal bus that transmits data corresponding to a predetermined amount of luminance correction to be corrected. In this case, the data transmitted from the internal bus is subjected to digital-to-analog conversion, so that a voltage applied to the second grid is supplied.

[0016]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limits are given, the scope of the present invention is not limited to these modes unless otherwise specified in the following description.

FIG. 1 shows a preferred embodiment of the video display device of the present invention. The video display device 10 is, for example, a television receiver or a monitor device of a computer. The image display device 10 includes the cabinet 1
2 and a cathode ray tube (CRT) 14 and the like. Below the cabinet 12, a brightness setting changing means 20 for manual operation is provided. In addition, a display area 30 for displaying when changing the setting of the luminance can be displayed for a certain time on a part of the cathode ray tube 14.

FIG. 2 shows an example of the brightness setting changing means 20. The brightness setting changing means 20 is of a so-called joystick type, for example. The brightness setting changing means 20 is operated by an operator such as a user.
It can be operated in one direction and the direction of R2, and can also be operated by pushing in the pushing direction R3.

FIG. 3 shows a display surface 14 of the cathode ray tube 14 shown in FIG.
3 shows an example of a display area 30 in FIG. The display area 30 is displayed for a certain period of time, for example, 3 seconds from the time when the operation unit 22 of the brightness setting change unit 20 in FIG. 2 is operated by the control of the display operation unit 70 shown in FIG. Then, the display surface 14 of the cathode ray tube 14 is automatically
It disappears from A. The display area 30 for adjustment displays, for example, luminance 32 and contrast 34, a horizontal frequency 36 of a currently input signal, and a vertical frequency 38 of a currently input signal as display items. Luminance 32 is 0% to 100% of luminance 32 in display bar 33
The percentage up to can be displayed. Contrast 34
Can be displayed on the display bar 35 as a percentage from 0% to 100%.

FIG. 4 shows a cathode ray tube 14 of the video display device 10 of FIG. 1 and an example of an attached circuit. Video display device 10
Has a cathode ray tube 14, an amplification unit 40, a control circuit unit 50, and a luminance setting change unit 20 roughly. The amplifying unit 40 has amplifiers 61, 62, 63 and a regulator 60 for controlling the second grid voltage. The cathode ray tube 14 has a display section (panel surface) 14A and a funnel section 14B, and the funnel section 14B has a first grid G1,
Second grid G2, third grid G3, and cathode K
R, KG, and KB. The first grid G1 is grounded, and the second grid G2 is connected to a regulator 60 for controlling the second grid voltage of the amplifier 40. The cathodes KR, KG, KB are connected to the amplifiers 61, 62, 63 of the amplifier 40, respectively.
The input sides of these amplifiers 61, 62, 63 are connected to the display operation means 70, and supplied with an R (red) video signal, a G (green) video signal, and a B (blue) video signal, respectively. It has become so.

Next, the control circuit unit 50 of FIG. 4 includes a display operation unit 70, a control unit 80, a digital-analog conversion unit 9
0, a RAM (random access memory) 100 as a luminance setting value holding unit, an internal bus 110, and a ROM (read only memory) 120. RAM 100
The brightness setting value holding means is a memory for holding the currently set brightness value or for holding the brightness setting value changed by changing the brightness setting state by operating the brightness setting changing means 20. The ROM 120 is the RAM 10
0, a memory for storing a program for controlling the control means 80 and the like. RAM 100, ROM 12
0, and the control means 80 are connected via an internal bus 110 and exchange data with each other.

The internal bus 110 is connected to the digital-to-analog conversion unit 90, and receives data D1 or D2 relating to the luminance of the digital value given from the internal bus 110.
Is converted into an analog value by the digital-analog converter 90, and then supplied to the second grid voltage control regulator 60. When the luminance control voltage DT is supplied to the second grid voltage control regulator 60 in this manner, the second grid voltage control regulator 60 for controlling the voltage applied to the second grid G2 is controlled by the second grid voltage control regulator DT. By controlling the grid current flowing through the grid G2,
By adjusting the cathode currents of the cathodes KR, KG, KB, the brightness of the image on the display surface 14A can be adjusted.

The control means 80 shown in FIG. 4 includes a luminance setting value range detecting section 81, a luminance correction judging section 82, a time detecting section 83,
A luminance setting value changing unit 84 is provided. The brightness setting value range detection unit 81 determines that the brightness setting value is within a predetermined range (for example, 30
%) (A range of% to 90%). The luminance correction determination unit 82 determines whether a predetermined amount of luminance correction is required at the present time based on the detection result of the luminance setting value from the range detection unit 81. The time detecting section 83 is a section for detecting whether or not the state in which the luminance set value has become a value outside the predetermined range has passed for a predetermined time, for example, one week, in the luminance set value range detecting section 81.

The luminance setting value changing section 84 is based on the judgment from the luminance correction judging section 82, and performs the data D1 or D2 relating to the luminance of the digital value for changing the luminance setting value when performing a predetermined amount of luminance correction. Is supplied to the digital-analog conversion unit 90 via the internal bus 110. The RAM 100 serving as the brightness setting value holding unit stores, for example, the brightness setting value changed by the brightness setting changing unit 20 by changing the brightness setting state or the brightness by the internal control changed by the control of the brightness setting value changing unit 84. Holds the setting change value. The display operation means 70 has a function of displaying an adjustment display area 30 as shown in FIG. 3 on the display surface 14A of the cathode ray tube 14 when the luminance setting change means 20 is operated by an operator such as a user. have. When the display operation means 70 is operated, the luminance setting value changing section 84 is operated to change the setting such as luminance and contrast in a manual manner.

Next, with reference to FIGS. 5 and 6, a description will be given of how to change the luminance setting in the video display method according to the embodiment of the present invention. First, a case in which the user manually operates the operation unit 22 of the brightness setting change unit 20 in FIG. 2 while looking at the display surface 14A to perform a normal brightness setting change will be described. The user operates the operation unit 22 shown in FIG. 2 of the brightness setting change unit 20 shown in FIG.
Is operated, a display area 30 for adjustment is displayed on the display surface 14A of FIG. The user can arbitrarily adjust the value of the luminance 32 in FIG. 3 according to the type of the image displayed on the display surface 14A of the cathode ray tube 14, and the like. For example, if the operation unit 22 shown in FIG.
2 becomes smaller as the percentage in the display bar 33 decreases, and the operation unit 22 moves in the direction of R2 in FIG.
Is operated, the percentage of the luminance 32 in the display bar 33 of FIG. 3 increases, and the image becomes brighter.

Next, when the cathode current density flowing through the cathodes KR, KG, KB of the cathode ray tube 14 of FIG. 4 is reduced or the cathode current density is increased due to the aging of the cathode ray tube 14. Next, a case in which an appropriate cathode current density for a specified drive voltage is not obtained will be described. That is, the brightness on the display surface 14A of the cathode ray tube is outside a certain upper limit value and a certain lower limit value, that is, the current brightness setting value on the display surface 14A is out of the predetermined range. Therefore, in this case, the control means 80 in FIG. 4 automatically performs a process for resetting an appropriate luminance by internal control.

Starting at a start step ST0 in FIG. 5, in a luminance setting value range confirmation step ST1, it is determined whether or not the current luminance setting value is outside a predetermined range, for example, by power-on of the video display device 10 in FIG. The process starts when it is desired to monitor the luminance set value. In the example of FIG. 5, the predetermined upper limit of the luminance setting value of the cathode ray tube 14 is, for example, 90%, and the predetermined lower limit is 30%. If the cathode current density is reduced, the luminance exceeds a predetermined upper limit of 90%. When the cathode current density increases, the luminance falls below a predetermined lower limit of 30%. Further, in the brightness setting value range confirmation step ST1, the brightness setting value range detection unit 81 in FIG.
Is the current brightness setting exceeds a predetermined upper limit,
Alternatively, it is determined whether the current luminance setting value is lower than a predetermined lower limit value. If the luminance setting value falls between the predetermined upper limit value and the predetermined lower limit value, step ST1 is repeated.

On the other hand, if the luminance setting value exceeds the predetermined upper limit value of 90%, or if the luminance setting value is lower than the predetermined lower limit value of 30%, the next time detecting step is performed. Proceed to ST2. In step ST2, if the luminance setting value is above the predetermined upper limit value or the luminance setting value is below the predetermined lower limit value,
The time detection unit 83 starts from the time when such a luminance set value reaches a value outside a predetermined range, and determines whether a predetermined time, for example, one week has elapsed.

Next, in the time detecting step ST2 of FIG. 5, if the time has not elapsed for a fixed time, for example, one week, the process returns to the step ST1, but if the time has elapsed, the process returns to the voltage control step ST3. Move on. In the voltage control step ST3, by controlling the voltage of the second grid G2, the grid current of the second grid G2 is adjusted, and the luminance of the display surface 14A is corrected.

FIG. 6 shows an example of the voltage control of the second grid G2. In the state A, the current luminance exceeds 90% which is a predetermined upper limit of the luminance set value. In state B, the current luminance is a predetermined lower limit value of 3
An example in which it is lower than 0% is shown. In state A,
When the display of the current luminance is, for example, 95%, FIG.
The luminance correction determination unit 82 determines that it is necessary to perform luminance correction, and increases the voltage of the second grid G2. That is, the luminance correction determination unit 82 supplies data for increasing the voltage of the second grid G2 to the digital-analog conversion unit 90 via the internal bus 110. As a result, the data D1 is converted into the digital-analog
The control value is converted to an analog value at 0, and the control voltage DT is supplied to the regulator 60 for controlling the second grid voltage. Second
The regulator 60 for grid voltage control has a control voltage D
By controlling the voltage of the second grid G2 based on T,
By adjusting the grid current flowing through the second grid G2, the luminance on the display surface 14A is forcibly increased by internal control.

Then, the brightness setting value converter 84 in FIG.
In the luminance correction operation step ST4 in FIG. 5, the luminance setting value is changed, that is, the luminance is inversely corrected. That is, in the state A of FIG. 6, the display of the luminance setting is reset to, for example, 50% for the convenience of the user. This allows
A 50% luminance reset state can be set.
The state of the reset of the luminance of% is shown in the display bar 33 of the luminance 32 in FIG.
Can be displayed.

On the other hand, in the voltage control step ST3 of FIG. 5, in the case of the state B of FIG. 6, if the current luminance is 25% which is lower than a predetermined lower limit value of 30%, for example, as shown in FIG. The luminance correction determining unit 82 determines that it is necessary to perform luminance correction. Then, the luminance correction determining unit 82
Supplies data D2 to the digital-analog conversion unit 90 via the internal bus 110. The data D2 is converted into an analog value by the digital-analog converter 90, and the control voltage DT is supplied to the second grid voltage control regulator 60. The regulator 60 for controlling the second grid voltage lowers the voltage of the second grid G2 to reduce the current flowing through the second grid G2 based on the control voltage DT, thereby forcing the brightness on the display surface 14A to the internal level. Decrease by control. Then, in the brightness correction operation step ST4 of FIG. 5, the brightness setting is reset to 50% for the convenience of the user. That is, in the display bar 33 of the brightness 32 in the display area for adjustment of FIG. 3, the display of 50% is reset.

As described above, in a television receiver using a cathode ray tube or a monitor device for displaying computer output, a change (drift phenomenon) of the reference luminance for a long period (more than several days) is automatically corrected. Next, after the voltage of the second grid G2 is changed from digital to analog, control is performed using an analog amount.

FIG. 3 is a set value indicator of the brightness of the user.
Is within a prescribed range (for example, 30 to 90).
%), The control means 80 of FIG. 4 does nothing. However, if the current luminance value is out of the specified range due to the aging of the cathode of the cathode ray tube and the state exceeds the specified period, the output of the polarity in which the indicator returns to within the specified range. Controls the register value for the second grid control.

According to the present invention, as a user control means capable of converting luminance in a manual manner, up / down (addition, subtraction) is performed by an operation unit 22 or buttons as shown in FIG.
This is particularly effective when the method is used. The user can change the contrast, brightness, and other screen sizes by operating the operation unit 2.
2 and buttons, and the control result is displayed in the display area 3 of the screen.
0 is fed back to the user.

Therefore, even if the user attempts to adjust the luminance, the inconvenience or stress that the luminance cannot be adjusted because the luminance display reaches 95% is reduced or eliminated. This eliminates the need for a serviceman to remove and adjust the cabinet of the video display device. Further, since such a change over time of the cathode ray tube can be relieved, the production yield of the cathode ray tube is improved, the number of steps for inspecting the cathode ray tube is reduced, or an aging step for finding a defective cathode ray tube becomes unnecessary. According to the embodiment of the present invention, since the change with time of the CRT can be relieved, the production yield of the CRT can be improved, the man-hour for the inspection of the CRT can be reduced, and the aging process for finding the defective CRT becomes unnecessary. By the way, the present invention is not limited to the above-described embodiment. For example, as shown in FIG. 2, not only a brightness setting change unit is provided on the front side of a cabinet, but also a remote control transmitter side for remotely operating a video display device. May be provided with a brightness setting changing means.

[0037]

As described above, according to the present invention,
The change in brightness in the cathode ray tube can be automatically corrected, and there is no need for repair by a service person.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an image display device of the present invention.

FIG. 2 is an enlarged perspective view showing a brightness setting changing unit of the video display device of FIG. 1;

FIG. 3 is a diagram showing a display area for adjustment of the video display device in FIG. 1;

FIG. 4 is a diagram illustrating a circuit configuration example of a video display device.

FIG. 5 is a diagram showing an image display method in the image display device, that is, an example of correction of luminance.

FIG. 6 is a diagram specifically showing an example of correction of luminance.

FIG. 7 is a diagram illustrating an example of a commonly used composite video signal.

[Explanation of symbols]

10 image display device, 14 cathode ray tube, 20
..Luminance setting changing means, 30... Display area for adjustment,
70 ... display operation means, 80 ... control means, 81
.. A luminance setting value range detecting unit, 82: a luminance correction determining unit, 83, a time detecting unit, 84, a luminance setting value changing unit, 90, a digital-analog converting unit (digital- Analog conversion means), 100 RAM (brightness setting value holding means)

Claims (6)

[Claims] A cathode ray tube having a plurality of grids; a luminance setting change unit for changing a luminance setting state of the cathode ray tube by an operation of an operator; and a luminance setting value changed by the luminance setting change. Display operation means for displaying on the cathode ray tube; brightness setting value holding means for holding a brightness setting value changed by changing the brightness setting state by the brightness setting changing means; and Detecting whether the state of the value outside the range has passed for a certain period of time, determining that a predetermined amount of luminance correction is necessary from the detection result, and controlling the voltage applied to the second grid of the cathode ray tube. Control means for performing luminance correction and changing luminance setting values in a direction opposite to the luminance correction to cancel luminance correction by controlling a voltage applied to the second grid. The video display apparatus comprising: a. 2. The control of a voltage applied to the second grid includes an internal bus for transmitting data corresponding to the predetermined amount of luminance correction to be corrected, and a digital-to-analog conversion of data transmitted from the internal bus. The video display device according to claim 1, wherein the conversion is performed through a conversion unit that performs the conversion. 3. The video display device according to claim 1, wherein the brightness setting change unit is disposed on a front side of a housing of the video display device or on a remote control transmitter side. 4. The image display device according to claim 2, wherein the setting state of the luminance is displayed for a predetermined time in a partial area of the cathode ray tube. 5. A brightness setting value in said cathode ray tube is changed by an operation of an operator, and a brightness setting value changed by said brightness setting change is displayed on said cathode ray tube, and said brightness by said brightness setting changing means is displayed. A brightness setting value changed by changing the setting state of the video signal, and detecting whether a state in which the brightness setting value has become a value outside a predetermined range has elapsed for a predetermined time. A voltage detection step of determining that a predetermined amount of luminance correction is necessary based on the detection result, and controlling a voltage applied to a second grid of the cathode ray tube to correct the luminance; and correcting the luminance. A luminance operation step of canceling luminance correction by controlling a voltage applied to the second grid by changing a luminance setting value in a direction opposite to the above. 6. The control of a voltage applied to the second grid includes an internal bus for transmitting data corresponding to the predetermined amount of luminance correction to be corrected, and a digital-to-analog conversion of data transmitted from the internal bus. The video display method according to claim 5, wherein the video display method is performed via a conversion unit that performs the conversion.