JP2002357810A - Video display device and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video display device including at least a display element and a light source capable of improving the sense of incompatibility of a display video caused by the perception of the luminance change of the light source by controlling the emission luminance of the light source while suppressing deterioration of display fidelity due to the floating of the black level of a video. SOLUTION: An APL detecting part 11 detects the APL of an input video signal, and outputs it as an APL signal. An intermediate control signal preparing part 12 prepares an intermediate control signal changing by each unit field period following the change of the APL of the input signal based on the APL signal. A signal change control part 13 controls the changing speed of the intermediate control signal based on a set time constant, and converts the intermediate control signal into a signal having a slow changing speed, and outputs it as a light source control signal. A light source driving part 14 drives a light source 2 under a driving condition corresponding to the light source control signal, and changes the emission luminance of the light source 2. Thus, the emission luminance of the light source can be slowly changed regardless of the change of the video signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display apparatus and method, and more particularly, to a light source for a display element having a transmission type or reflection type light modulation function driven based on an input image signal. The present invention relates to an image display device and method for displaying an image by irradiating light from the image display device.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for image devices such as video tape recorders and video disk players, and image display devices that allow users to enjoy powerful images with the enhancement of image software.

Conventionally, a direct-view type liquid crystal display device or a projection type display device has been used as an image display device for displaying an image by spatially modulating light emitted from a light source with a display element having a transmission type or reflection type light modulation effect. There are things like devices. In a direct-view liquid crystal display device, a liquid crystal panel is used as a display element, and an image displayed on the liquid crystal panel is directly viewed. On the other hand, a projection display device uses a powerful light source to project an image displayed on a liquid crystal panel or another display element on a screen.

Comparing an image display device using a display element having such a light modulation function with an image display device using a self-luminous display element such as a CRT, a direct-view type liquid crystal display device has, for example, a bright scene. The problem was the lack of brightness and the black float in dark scenes. Therefore, attempts have been made to solve these problems.

[0005] In a direct-view type liquid crystal display device, as a method generally performed to improve display image quality, an electric signal such as contrast adjustment (adjustment of signal amplification gain) or black level adjustment is applied to an input video signal. This is a simple signal adjustment method. In addition to these electric adjustments, there is also an apparatus in which the luminance level of the light source can be changed in several steps. However, the adjustment of the light source luminance level is manually performed by the user, and the light source luminance thereafter is in a fixed state.

On the other hand, a display device having a function of adjusting the luminance level of a light source has been put to practical use in a projection display device, but in this case, unlike a direct-view display device,
The main objectives are to reduce the power consumption of the apparatus rather than to improve the display image quality, to adjust the brightness for setting an image with a brightness that is easy to see with respect to the screen size and environmental lighting conditions, and to extend the life of the light source. The adjustment of the light source luminance level is manually performed by the user similarly to the direct-view type liquid crystal display device, and the light source luminance thereafter is in a fixed state.

As described above, both the conventional direct-view type liquid crystal display device and the projection type display device have a lack of brightness in a bright scene and blackness in a dark scene as compared with a self-luminous display device such as a CRT. There is a strong demand for improved display image quality for floating. However, as described above, the light source luminance control method employed in the conventional direct-view type liquid crystal display device and the projection type display device is a static fixed control, and corresponds to a dynamic change of an input video signal. Not. Therefore, there is a problem that the display image quality of each scene of the input video signal cannot be improved.

Therefore, as one of the methods for improving the display image quality, there has been proposed a method of dynamically changing the light emission luminance of the light source according to the scene of the image. For example, Japanese Patent Application Laid-Open
The method is disclosed in, for example, Japanese Patent Application Laid-Open No. 127608 and Japanese Patent Application Laid-Open No. 6-160811.

In Japanese Patent Application Laid-Open No. 5-127608, features of an input video signal are detected from the maximum value, the minimum value, and the average value of the input video signal, and when the level difference between the maximum value and the minimum value is large, contrast control is performed. If the difference between the maximum and minimum values is small, raise the contrast control to increase the signal amplification gain and increase the average value of the maximum and minimum values to the specified value. In the case where the luminance of the display device is high, a method of lowering the luminance of the light source to make the luminance of the display device close to a constant value has been proposed.

In Japanese Patent Application Laid-Open No. Hei 6-160811, the maximum value of an input video signal is detected. If the maximum value is high, the brightness of the light source is increased. If the maximum value is low, the brightness of the light source is reduced. There has been proposed a method of increasing the relative contrast ratio between when the maximum value is high and when the maximum value is low by making the luminance signal amplitude when the value is low smaller than the luminance signal amplitude when the maximum value is high.

[0011]

Problems to be Solved by the Invention
The technique proposed in Japanese Patent Application Laid-Open No. H8-108 is to dynamically control the light source luminance according to the input scene as described above. However, the purpose is to make the display brightness constant, and there is a problem that the black floating is not improved for dark scenes such as movie software. In addition, since the control of the light source luminance is performed based on the average value of the maximum value and the minimum value of the input video signal, in an input scene where the maximum value is locally high or the minimum value is low, the input scene There is a problem that the luminance of the light source is adjusted inappropriately without being able to capture the features. Furthermore, since the adjustment of the light source luminance is performed discontinuously, there is a problem that the screen luminance greatly changes at the time of the change of the light source luminance, giving a sense of incongruity to the viewer.

On the other hand, the technique proposed in JP-A-6-160811 also dynamically controls the light source luminance in accordance with the input video signal as described above. Since the luminance of the light source is controlled accordingly, in the case of an input scene in which the maximum value is locally high despite the low APL, the luminance of the light source becomes high, and rather, black floating occurs in a dark part of the image. There is a problem. In addition, discharge-type light sources such as xenon lamps and high-pressure mercury lamps used in projection-type display devices are subject to stable lighting such as instability of lighting start-up and flickering during steady-state lighting by repeating sudden changes in driving conditions. However, there is a problem that the reliability of the lamp is lowered due to the deterioration of the performance and the life characteristic.

Therefore, an object of the present invention is to realize an image display with a sense of contrast by changing the luminance of a light source according to an input video signal, while displaying the image due to a sudden change in the luminance of the light source. It is an object of the present invention to provide an image display device and a method capable of preventing a sense of discomfort, and improving the life characteristics of a light source.

[0014]

A first aspect of the present invention is to irradiate light from a light source to a display element having a transmissive or reflective light modulation function driven based on an input video signal. An APL detecting means for detecting an average luminance level of the input video signal, and an emission luminance of the light source based on the average luminance level detected by the APL detecting means. Light source control signal generating means for generating a light source control signal for dynamically controlling according to the luminance level, and light source driving means for driving the light source in accordance with the light source control signal generated by the light source control signal generating means And a light source control signal generation unit that determines whether the amount of change in the level per unit time in the light source control signal is related to the change in the average luminance level detected by the APL detection unit. So that a predetermined amount or less, and generates a light source control signal.

As described above, according to the first aspect of the invention, the amount of change in the light emission luminance of the light source is set to a predetermined amount or less irrespective of the variation in APL. Can be suppressed from changing. Also,
By reducing the change in the luminance of the light source, the life of the light source can be improved.

According to a second aspect of the present invention, in the first aspect, the predetermined amount is a change amount to such an extent that the luminance change of the light source is hardly perceived.

As described above, according to the second aspect, the amount of change in the light emission luminance of the light source is set so as not to be perceived by the viewer. Video display without discomfort is possible.

A third invention is characterized in that, in the second invention, the predetermined amount is a change amount that requires at least 0.3 seconds to change the light emission luminance of the light source with the maximum control width.

As described above, according to the third aspect, the predetermined amount of the light emission luminance of the light source is set to a change amount that requires at least 0.3 seconds to change the light emission luminance with the maximum control width. The viewer does not feel the change in the light source luminance, and when the light emission luminance of the light source is dynamically controlled, a video display without a sense of incongruity can be realized.

In a fourth aspect based on the first aspect, the light source control signal generating means is sequentially output immediately before by the light source control signal generating means in accordance with the average luminance level detected by the APL detecting means. The light source control signal is generated by adding or subtracting a predetermined amount to or from the level of the light source control signal.

As described above, according to the fourth aspect, the current light source control signal is created by adding or subtracting a predetermined amount to or from the level of the light source control signal created immediately before, so that the light source luminance can be easily obtained. Can be limited.

In a fifth aspect based on the first aspect, the light source control signal generating means generates an intermediate control signal for generating an intermediate control signal which fluctuates in response to a change in the average luminance level detected by the APL detecting means. Means and signal change control means for controlling a change in the level of the intermediate control signal created by the intermediate control signal creation means to generate a light source control signal.

As described above, according to the fifth aspect, first, an intermediate control signal that fluctuates in accordance with a change in the average luminance level detected by the APL detecting means is generated, and then the level change is controlled. Thus, the amount of change in the light source control signal can be controlled.

According to a sixth aspect based on the fifth aspect, the signal change control means includes a signal change control means for comparing the light source control signal output immediately before by the signal change control means with the intermediate control signal generated by the intermediate control signal generation means. When the level difference is larger than the predetermined error amount, the predetermined amount is added to or subtracted from the level of the light source control signal output immediately before this, and output as a light source control signal. When the value is smaller, the intermediate control signal is output as it is as the light source control signal.

As described above, according to the sixth aspect, when the current light source control signal is created by adding or subtracting a predetermined amount to or from the level of the light source control signal created immediately before, Oscillation of the level can be avoided.

In a seventh aspect based on the first aspect, the light source control signal generating means is configured such that, when the switching of the input video signal occurs, regardless of the state of the light source control signal generated immediately before the switching occurs. , A light source control signal corresponding to the current average luminance level detected by the APL detecting means.

As described above, according to the seventh aspect, when the switching of the input video signal occurs, the control state of the light source luminance immediately before the switching affects the control state after the switching, and the display video It is possible to avoid a problem that the user feels strange.

According to an eighth aspect of the present invention, there is provided an image display apparatus for displaying an image by irradiating light from a light source to a display element having a transmissive or reflective light modulation function driven based on an input image signal. APL detecting means for detecting an average luminance level of an input video signal, and a light source control signal for dynamically controlling light emission luminance of the light source in accordance with the average luminance level detected by the APL detecting means Light source control signal creating means, and light source driving means for driving the light source according to the light source control signal created by the light source control signal creating means, wherein the light source control signal creating means is used to reduce the light emission luminance of the light source. The light source control signal is generated such that the level of change in the level of the light source control signal per unit time is greater than the amount of change when increasing the light emission luminance of the light source.

As described above, according to the eighth aspect, the amount of change when controlling the light emission luminance of the light source in a direction in which the light emission luminance decreases is as follows.
By making the luminance larger than when controlling in the direction in which the emission luminance increases, the unnaturalness due to the luminance change of the light source when the video scene changes from a dark scene to a bright scene is suppressed. When it changes,
By lowering the light emission luminance of the light source earlier, deterioration of display quality such as floating of black caused by high light emission luminance of the light source can be improved, and the quality of the displayed image can be improved as a whole.

A ninth aspect of the present invention is an image display apparatus for displaying an image by irradiating light from a light source to a display element having a transmission type or reflection type light modulation function driven based on an input image signal. APL detecting means for detecting an average luminance level of an input video signal, and based on the average luminance level detected by the APL detecting means, light emission luminance of a light source is dynamically controlled in accordance with the average luminance level. Light source control signal generating means for generating a light source control signal for, and light source driving means for driving the light source based on the light source control signal generated by the light source control signal generating means,
The light source control signal generating means executes dynamic control of the light source at least for a second time period each time a state in which the light emission luminance of the light source is controlled at an intermediate level other than the maximum level and other than the minimum level continues for the first predetermined period. A light source control signal is generated so as to be interrupted for a predetermined period.

As described above, according to the ninth aspect, it is possible to prevent the life of the light source from deteriorating by continuously changing the luminance of the light source over a long period of time. Further, in particular, since the control of the luminance of the light source is interrupted when the luminance of the light source changes in the intermediate state for a predetermined period or more, the interruption of the control of the luminance of the light source is minimized while improving the display quality. It is possible to do with.

In a ninth aspect based on the ninth aspect, the light source control signal creating means is configured such that the average luminance level detected by the APL detecting means is detected after a lapse of a second predetermined time from the interruption of the dynamic control of the light source. The dynamic control of the light source is restarted when the level difference from the average luminance level at the time of interruption is within a predetermined difference.

As described above, according to the tenth aspect, A
Since the control is resumed after the level difference between the average luminance level detected by the PL detection means and the average luminance level at the time of interruption is within a predetermined difference, control of the interrupted light source is suddenly performed. It is possible to eliminate a sense of incongruity in the image display due to the restart of the operation.

According to an eleventh aspect of the present invention, there is provided an image display method for displaying an image by irradiating light from a light source to a display element having a transmissive or reflective light modulation function driven based on an input image signal. An APL detecting step of detecting an average luminance level of the input video signal;
Light source driving step of dynamically driving the light source according to the average luminance level detected by the detection step,
In the light source driving step, the light source is driven such that the amount of change in the level of light emission luminance per unit time of the light source per unit time is equal to or less than a predetermined amount regardless of the change in the average luminance level detected by the APL detection step. .

As described above, according to the eleventh aspect, the amount of change in the light emission luminance of the light source is equal to or less than the predetermined amount regardless of the change in APL. Can be suppressed from changing. Further, the life of the light source can be improved by reducing the change in the luminance of the light source.

According to a twelfth aspect, there is provided an image display method for displaying an image by irradiating light from a light source to a display element having a transmissive or reflective light modulation function driven based on an input image signal. An APL detecting step of detecting an average luminance level of the input video signal;
Light source driving step of dynamically driving the light source according to the average luminance level detected by the detection step,
The light source driving step drives the light source such that the amount of change in the level of light emission luminance of the light source per unit time when the light emission luminance of the light source is reduced is larger than the amount of change when the light emission luminance of the light source is increased. It is characterized by doing.

As described above, according to the twelfth aspect, the amount of change when controlling in the direction in which the light emission luminance of the light source decreases is made larger than when controlling in the direction in which the light emission luminance increases. While suppressing the unnaturalness due to the change in luminance of the light source when the video scene changes from a dark scene to a bright scene, the light source can be reduced by reducing the light emission luminance of the light source earlier, especially when the video scene changes to a dark scene. , The degradation of display quality such as floating of black due to the high light emission luminance can be improved, and the quality of the displayed image can be improved as a whole.

According to a thirteenth aspect, there is provided an image display method for displaying an image by irradiating light from a light source to a display element having a transmissive or reflective light modulation function driven based on an input image signal. An APL detecting step of detecting an average luminance level of the input video signal;
A light source driving step of dynamically driving the light source based on the average luminance level detected by the detection step, wherein the light source driving step is controlled at an intermediate level other than the maximum level and the emission level of the light source other than the minimum level. The light source is driven such that the dynamic control of the light source is interrupted at least for the second predetermined period each time the state of the light source continues for the first predetermined period.

As described above, according to the thirteenth aspect, it is possible to prevent the life of the light source from being deteriorated due to the luminance of the light source being continuously changed over a long period of time. Further, in particular, since the control of the luminance of the light source is interrupted when the luminance of the light source changes in the intermediate state for a predetermined period or more, the interruption of the control of the luminance of the light source is minimized while improving the display quality. It is possible to do with.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a block diagram showing a configuration of a video display device according to a first embodiment of the present invention. FIG.
, The video display device includes a display element 1, a light source 2,
Reflecting mirror 3, condenser lens 4, projection lens 5, screen 6, APL detector 11, intermediate control signal generator 1
2, a signal change control unit 13, a light source driving unit 14, a video signal processing unit 21, a display element driving unit 22, and a system control unit 31.

The display element 1 has a light modulation function, and has a light source 2
Illuminates the display element 1. The reflecting mirror 3, the condenser lens 4, and the projection lens 5 are illumination optical systems, and
Reflects the light emitted from the light source 2,
Collects the light emitted from the light source 2 and the light reflected by the reflector 3, and the projection lens 5 enlarges and projects the image displayed on the display element 1 onto the screen 6. A video signal is input to the APL detection unit 11, detects an APL of the input video signal, and outputs a detection result as an APL signal. The intermediate control signal creation unit 12 creates an intermediate control signal that is a source of a light source control signal for controlling the light emission luminance of the light source 2 based on the APL signal output from the APL detection unit 11. The signal change control unit 13 controls a change in the level of the intermediate control signal output from the intermediate control signal generation unit 12 to generate and output a light source control signal for controlling the light emission luminance of the light source 2. The light source driving unit 14 drives the light source 2 under conditions according to the light source control signal from the signal change control unit 13. The video signal processing unit 21 processes the input video signal into a form suitable for displaying on the display element 1. The display element driving unit 22 drives the display element 1 based on the video signal processed by the video signal processing unit 21. The system control unit 31 controls each control unit described above.

FIG. 2A shows an example of a time change of the APL signal output from the APL detecting section 11, and FIG.
FIG. 2B shows a temporal change in the light emission luminance of the light source 2 driven by the light source control signal created based on the APL signal shown in FIG.

Hereinafter, with reference to FIGS. 1 and 2, the operation of the video display apparatus according to the present embodiment, in particular, the operation relating to the emission luminance control of the light source 2 will be described in detail. Since the operations of the video signal processing unit 21 and the display element driving unit 22 are well known, the description will be omitted.

The APL detection unit 11 performs an APL detection for the luminance signal component of the input video signal every unit field period.
And outputs the detection result as an APL signal. The intermediate control signal generator 12 converts the level of the APL signal output from the APL detector 11 for each unit field period according to a set conversion function or conversion table, and generates an intermediate control signal. The intermediate control signal is a signal that is a source of a light source control signal for finally controlling the light emission luminance level of the light source. The intermediate control signal is generated so that the light emission luminance of the light source 2 increases when the APL is high, and the light emission luminance of the light source 2 decreases when the APL is low. here,
The conversion function and the conversion table may be incorporated in the intermediate control signal creation unit 12 in advance, or may be appropriately set by the system control unit 31. The intermediate control signal is
Since the signal is directly generated from the APL of the video signal, the signal changes every unit field period following the change in the APL of the video signal. The signal change control unit 13 controls the change speed of the intermediate control signal that changes every unit field period,
By controlling based on the set time constant, the intermediate control signal is converted into a signal having a slowly changing speed and output as a light source control signal. The detailed operation of the signal change control unit 13 will be described later. The light source driving unit 14 changes the light emission luminance of the light source 2 by driving the light source 2 under driving conditions according to the light source control signal.

By the way, for reference, the signal change control unit 1
The case where the intermediate control signal is directly input to the light source driving unit 14 without using the light source 3 to control the light source 2 will be considered. in this case,
As described above, since the intermediate control signal is a signal directly reflecting the change in the APL of the video signal, the light emission luminance of the light source 2 also changes every unit field period accordingly. As described above, if the light emission luminance of the light source 2 is controlled in such a manner that the change in the APL is reflected as it is, the change in the light emission luminance is too fast, the image looks like a flicker, and the display quality deteriorates. Further, the light source driving unit 14 and the light source 2
Since there is a time constant for a change in the control state, a change in luminance is delayed with respect to a change in APL. Therefore, for example, when the scene suddenly changes from a bright scene to a completely dark scene, the screen luminance suddenly changes suddenly behind the change of the scene, resulting in a very uncomfortable image. On the other hand, the light source 2 can frequently change the light emitting state by controlling the light emission luminance of the light source 2 in such a manner that the change in the APL is reflected as it is. This leads to a decrease in reliability.

In order to solve the above-mentioned problem, the intermediate control signal is passed through a low-pass filter,
It is conceivable to reduce the change in the light emitting state of the light source.
However, the time constant of the low-pass filter composed of electric components is at most about 0.1 second, and the light source 2
The change in screen luminance due to the change in luminance is still detected, which is insufficient to solve the problem of poor display quality.

Therefore, in the present embodiment, the signal change control section 13 is provided in order to solve the problem of deterioration of display quality due to the perceived change in screen luminance as described above. The change speed of the intermediate control signal is determined by the signal change control unit 1.
The control by 3 reduces the change speed of the light emission luminance of the light source 2 to a level that is not perceptible. Therefore, it is possible to perform display with high contrast while preventing deterioration of display quality. In addition, as a result of reducing the change speed of the light emission luminance of the light source, the number of changes in the light emission state of the light source 2 decreases, and it is possible to prevent the reliability of the light source 2 from lowering. In order to prevent the display quality from deteriorating due to a perceived change in the light emission luminance of the light source 2, as shown in FIG. 2B, the light emission luminance of the light source 2 is temporarily reduced to the minimum light emission luminance L1.
From the maximum emission luminance L2 to the maximum emission luminance L2, and from the maximum emission luminance to the minimum emission luminance linearly, the time T0 required is at least 0.3 seconds, and preferably at least longer. It was experimentally required that the brightness of the light source 2 be changed slowly.
In this case, the degree of the desired change speed is the time required for linearly changing the luminance of the light source from the highest light emission luminance to the lowest light emission luminance, and the case where the light source luminance is linearly changed from the lowest light emission luminance to the highest light emission luminance. Is only indirectly expressed by the time it takes to do so. It goes without saying that the speed of change is important in actually controlling the luminance of the light source.

Hereinafter, the signal change control unit 13 which controls the change speed of the light source luminance will be described in detail. FIG. 3 is a block diagram illustrating a configuration of the signal change control unit 13. The signal change control unit 13 includes a comparator 301
, Adder 302, subtractor 303, selector 304
, A difference calculator 305, a comparator 306, and a selector 307. Hereinafter, the operation will be described.

The signal change controller 13 receives the intermediate control signal generated by the intermediate control signal generator 12. In the signal change control unit 13, a light source control signal is created based on the intermediate control signal and output from the selector 307. The light source control signal output from the selector 307 is supplied to the comparator 301, the adder 302, and the subtractor 3.
03 is fed back. The signal change control unit 13
The light source control signal before one unit field period is added to the adder 30.
The light source control signal is sequentially updated and output every unit field period by adding or subtracting the change amount setting signal from the system control unit 31 in the second or subtractor 303. As described above with reference to FIG. 2, the change amount setting signal is set to such a change amount that the change speed of the light emission luminance of the light source 2 is not perceived. The input intermediate control signal is compared by the comparator 301 with the light source control signal one unit field period earlier, and the selector 304 selects either the output of the adder 302 or the output of the subtractor 303 according to the comparison result. Is output.
For example, when the level of the intermediate control signal in the current unit field period is higher than the level of the light source control signal one unit field period ago, the output of the adder 302, that is, the light source control signal one unit field period ago. A predetermined change amount is added and output from the selector 304.
Here, by arbitrarily setting the change amount setting signal from the system control unit 31, the change speed of the light source control signal can be freely controlled. It is to be noted that the rate of change of the light source control signal can be further reduced by setting the update interval of the light source control signal not at every unit field period but at every plural unit field periods. This is because the change speed of the light source control signal is proportional to the change amount set by the change amount setting signal divided by the update interval of the light source control signal.

The difference detector 305 calculates the difference between the output from the selector 304 and the intermediate control signal. The difference output from the difference detector 305 is compared in a comparator 306 with an error amount setting signal input from the system control unit 31. As a result, when the difference output of the difference calculator 305 is equal to or smaller than the error amount setting signal, the selector 307 selects the input intermediate control signal, and outputs the intermediate control signal as it is as the light source control signal. On the other hand, when the difference output of the difference calculator 305 is larger than the error amount setting signal, the selector 307 selects the output from the selector 304 and outputs this output as a light source control signal. It is not always necessary to select and output the intermediate control signal and the output of the selector 304 according to the error amount. However, if the output is selected according to the error amount setting signal, the change This is preferable because it is possible to prevent the output of the selector 304 from oscillating without being stabilized even though the level of the intermediate control signal is constant, depending on the set value of the amount setting signal. Note that the error amount is desirably set to half the change amount in order to reliably prevent the oscillation state.

As described above, according to the first embodiment,
Since the light emission luminance of the light source 2 is controlled in accordance with the level of the APL, for example, in a dark scene with a low APL such as movie software, the light emission luminance of the light source 2 is controlled so as to reduce the light emission luminance of the screen. The problem of deterioration of the display image quality can be improved, and a higher-quality image can be provided. In particular, by making the change speed of the light emission luminance of the light source 2 small enough that the viewer does not perceive the change of the light source luminance by the signal change control unit 13, it is possible to display a video without a sense of incongruity, In addition, there is a great effect that a reduction in the life characteristics of the light source 2 can be prevented.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
1 shows a configuration of a video display device according to the embodiment. The difference between the video display device shown in FIG. 4 and the video display device shown in FIG. 1 is that the signal change control unit 15 and the system control unit 32
Therefore, description of other configurations will be omitted. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, the signal change control unit 15
Is similar to the first embodiment.
The light source control signal for controlling the light emission luminance of the light source 2 is generated by controlling the changing speed of the intermediate control signal generated in the step (1). However, the change speed is controlled such that the change speed when decreasing the light emission luminance of the light source 2 is faster than the change speed when decreasing the light emission luminance. Less than,
The operation of the signal change control unit 15 will be described in detail.

FIG. 5A shows an example of a time change of the APL signal output from the APL detector 11, and FIG.
FIG. 5B shows a temporal change of the light emission luminance of the light source 2 driven by the light source control signal created based on the APL signal shown in FIG.

The signal change control unit 15 controls the change speed of the intermediate control signal that changes every unit field period with a set time constant, and converts the intermediate control signal into a light source control signal having a slow change speed. At this time, it is detected whether the intermediate control signal changes in a direction to increase the light emission luminance of the light source 2 or conversely, changes in a direction to decrease the light emission luminance, and the control is performed in a direction to lower the light emission luminance of the light source 2. When the control is performed, the change speed of the light source control signal is increased so that the change in the light emission luminance of the light source 2 is performed faster than when the control is performed in a direction to increase the light emission luminance. That is, FIG.
As shown in FIG. 5A and FIG. 5B, assuming that the time when the light emission luminance of the light source 2 is changed from the minimum light emission luminance level L1 to the maximum light emission luminance level L2 is time T1, the light emission luminance of the light source 2 becomes Control is performed such that the time when changing from the maximum light emission luminance level L2 to the minimum light emission luminance level L1 is a time T2 shorter than the time T1. In this case, it is needless to say that the speed of change is important.

FIG. 6 shows the configuration of the signal change control unit 15. However, the difference between the signal change control unit 15 and the signal change control unit 13 in the first embodiment shown in FIG.
However, the only difference is that the change amount setting signals are separately input, and the description of the other identical components is omitted.

In the signal change controller 15, the adder 30
The luminance change amount setting signal is input to 2 and the luminance decrease change amount setting signal is input to the subtracter 303.
By configuring the signal change control unit 13 in this manner, the change speed when the light emission luminance of the light source 2 is increased and the change speed when the light emission luminance is decreased can be separately set. By always setting the change amount setting signal at the time of decrease in luminance to a value larger than the change amount setting signal at the time of increase in luminance, the change speed of the emission luminance when the luminance of the light source 2 changes in the direction of decreasing the luminance can be increased. Can be faster.

By the way, if the change speed of the light source luminance is fast,
As described above, the change in the light source luminance is perceived and the quality of the displayed image deteriorates. From this viewpoint, it is preferable that the change speed of the light source luminance be slow. However, especially in movie software, there are many relatively dark scenes, and it is a problem to avoid deterioration of the quality of the displayed image due to the occurrence of floating black in particularly dark scenes. Therefore, when changing from a dark scene to a bright scene, the luminance of the light source is changed relatively slowly in order to minimize a perceived change in the light source luminance. By controlling the brightness of the light source to change relatively quickly in order to minimize the occurrence of floating, the quality of the displayed image can be improved as a whole.

Further, by rapidly lowering the light emission luminance of the light source 2 in accordance with the change of the image, the synergistic effect of the lowering of the image luminance and the lowering of the light emission luminance of the light source can be obtained.
It is possible to make the viewer feel that the image brightness has become darker, and to display a more effective image in movie software or the like that takes care of dark scenes.

As described above, according to the second embodiment,
The speed of change when controlling the direction in which the light emission luminance of the light source 2 decreases becomes faster than that when controlling in the direction in which the light emission luminance increases, so that the light source 2 when the image scene changes from a dark scene to a bright scene is changed. While the unnaturalness due to the change in luminance is suppressed, especially when the video scene changes to a dark scene, the light emission luminance of the light source 2 is reduced earlier to display black floating or the like due to the higher light emission luminance of the light source 2. It is possible to improve the deterioration of the quality and improve the quality of the displayed image as a whole.

(Third Embodiment) FIG. 7 shows a third embodiment of the present invention.
It is a block diagram showing the composition of the picture display device concerning an embodiment. Note that the image display device shown in FIG. 7 is different from the image display device shown in FIG. 1 only in the signal change control unit 16, the light source emission luminance state detection unit 17, and the system control unit 33. The configuration is denoted by the same reference numeral, and the description is omitted.

In this embodiment, the signal change control section 16
Is similar to the first embodiment.
By controlling the change speed of the intermediate control signal generated in the step (1), a light source control signal for controlling the light emission luminance of the light source 2 is generated. The light source light emission luminance state detection unit 17 constantly monitors the light source control signal output by the signal change control unit 16, and temporarily controls the light emission luminance of the light source 2 to follow the APL according to the progress of the light emission state of the light source 2. Control to suspend or resume. This control is performed, for example, by outputting a follow-up control signal from the light source emission luminance state detecting unit 17 to the signal change control unit 16. The signal change control unit 16 responds to the follow-up control signal to adjust the level of the light source control signal. Is fixed, the tracking of the light source luminance to the APL is temporarily stopped.

Hereinafter, referring to FIGS. 8A and 8B, the light source 2 based on the control of the light source emission luminance state detecting unit 17 will be described.
The change in the light emitting state of the device will be described in detail. FIG.
FIG. 8B shows an example of a time change of the APL signal output from the PL detection unit 11, and FIG. 8B is driven by a light source control signal created based on the APL signal shown in FIG. 5 shows a temporal change of the light emission luminance of the light source 2.
In the present embodiment, the light source emission luminance state detection unit 17 includes:
The elapsed time in a state where the light emission luminance continuously transitions in an intermediate region between the light emission luminance level L1 and the maximum light emission luminance level L2 without being counted is counted. Then, a predetermined time Ta set in advance by the system control unit 33.
Is counted, the light source emission luminance state detection unit 17
Sends a follow-up control signal to the signal change control unit 16 and
The change of the light emission luminance of following the APL is interrupted for a predetermined time Tb, and the light emission luminance at the time of the interruption is maintained. Then, when the interruption period Tb elapses, a standby state is entered, and the light emission luminance (the thin line portion in FIG. 8B) assuming that the control of the light source 2 by the light source control signal is continued without interruption is maintained. The emission luminance of the light source 2 (see FIG. 8)
(Bold line section) and within a predetermined level difference, and then the signal change control section 16
Then, the control for causing the light emission luminance of the light source 2 to follow the APL is restarted.

The timing at which the control of the light source is resumed depends on the light emission luminance when the control of the light source 2 by the light source control signal is continued without interruption and the light emission luminance of the light source 2 currently maintained. Although it was after waiting until it became within the predetermined level difference, this is a preferable control method to eliminate the discomfort of the video display due to the sudden restart of the control of the interrupted light source, You don't always have to wait for this timing.

FIG. 9 shows the configuration of the light source light emission luminance state detecting section 17 in this embodiment. The light source control signal output from the signal change control unit 16 is input to the comparators 501 and 502. Comparator 501
Compares the light source control signal with the maximum luminance (L2) setting signal, and similarly, the comparator 502 compares the light source control signal with the minimum luminance (L1) setting signal. The maximum luminance (L2) setting signal and the minimum luminance (L1) setting signal are both supplied from the system control unit 33. As a result of the comparison,
When the current light emission luminance is in an intermediate state higher than the minimum luminance L1 and lower than the maximum luminance L2, a control signal is output from the AND circuit 503 to the timer circuit 505, and the first timer circuit 505 counts time. To start. The first timer circuit continues counting while the light emission luminance is in the intermediate state. And the system control unit 33
When the set time Ta set from has elapsed, the first timer circuit 505 outputs a follow-up control signal to the signal change control unit 16 to interrupt the brightness control of the light source 2 that has followed the APL, and the second timer The circuit 506 starts counting.

When the set time Tb set by the system control unit 33 elapses, the second timer circuit 506
A control signal is sent to the R circuit 504, and the first timer circuit 5
Reset 05. When the first timer circuit is reset, the tracking control signal output from the first timer circuit is reset, and the light source 2 in the signal change control unit 16 is reset.
Restart of the brightness control is permitted. Signal change control unit 16
Detects that the tracking control signal has been reset,
The currently maintained light emission luminance of the light source 2 is compared with the intermediate control signal output from the intermediate control signal generation unit 12, and when the difference between the two becomes within a certain range, the luminance control of the light source 2 is restarted. (This part is not shown). In addition,
When the emission luminance reaches the maximum luminance (L2) or the minimum luminance (L1) during the counting of the first timer circuit 505, the first timer circuit 505 is reset by the comparators 501, 502 and the OR circuit 504.

As described above, according to the third embodiment,
In the brightness control of the light source of the video display device, when the brightness of the light source continues to change for a certain period of time (Ta) in an intermediate state, the control of the tracking of the APL for a certain period of time (Tb) is interrupted. It is possible to prevent the life of the light source from being deteriorated due to the continuous change over a long period of time.

In general, there is a trade-off between the improvement of display quality by causing the luminance of the light source to follow the APL and the improvement of the life of the light source by interrupting the luminance control of the light source. Therefore, for example, simply suspending the control of the light source at a predetermined timing every time for a predetermined period of time simply gives priority to the improvement of the life of the light source over the improvement of the display quality. . However, in the present embodiment, since the control of the light source is temporarily suspended only when the light source continues to change luminance in the intermediate state for a predetermined time or more, an advantage beyond a mere trade-off relationship is obtained. . In this regard, FIG.
This will be described with reference to FIG.

FIG. 10A shows an example of a time change of the APL signal output from the APL detecting section.
(B) shows a temporal change in the light emission luminance of the light source driven by the light source control signal created based on the APL signal shown in FIG. 10 (a). By the way, there is a case where control is performed so that the light source luminance follows only a part of the change range of the APL signal output from the APL detection unit. For example, in the APL signal level shown on the vertical axis of FIG. 10A, it is conceivable that the luminance of the light source dynamically follows only the range from the level Y to the level X. At this time, when the level is equal to or lower than the level Y, the light source is driven at the minimum emission luminance L1, and when the level is equal to or higher than the level X, the light source is driven at the maximum emission luminance L2. In the case of controlling the luminance of the light source in this way, if the control of the light source is simply interrupted for a certain period of time, the luminance of the light source is controlled as indicated by the thick line in FIG. You. Here, FIG.
A thin line portion indicates a change in luminance of the light source when the control of the light source is not interrupted. Looking at the thin line portion, in the illustrated range, the brightness of the light source is fixed at a maximum level L2 and a minimum level L1, respectively, for a certain period. That is, even if the brightness control of the light source is not interrupted, the life of the light source should not deteriorate. However, in the illustrated example, since the control of the light source is periodically interrupted for a certain period, the control of the light source is interrupted in the interruption period and the standby period shown in FIG. Display quality has not been improved.

On the other hand, according to the control operation of the present embodiment, such useless interruption of the light source control is not performed, and only when the luminance of the light source is changed in the intermediate state for a predetermined period or more, the light source control is performed. Interrupt the brightness control. Therefore, it is possible to interrupt the control of the brightness of the light source with a minimum necessary while improving the display quality, and an effect more than a mere trade-off can be obtained.

(Fourth Embodiment) FIG. 11 shows a configuration of a video display device according to a fourth embodiment of the present invention. In addition,
The video display device shown in FIG. 11 differs from the video display device shown in FIG. 11 only in the intermediate control signal creation unit 18, the signal change control unit 19, and the system control unit 32. Omitted. In FIG. 11, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, the system control unit 34
Controls the above-mentioned control units, and in particular, sends a light emission luminance control mute signal to the intermediate control signal creation unit 18 and sends an initial value setting signal to the signal change control unit 19. The intermediate control signal creating unit 18 receives the input APL as in the above-described embodiment.
The signal is converted into an intermediate control signal that is a source of a light source control signal for controlling the light emission luminance level of the light source 2 according to a set conversion function or conversion table for each unit field period. The intermediate control signal is controlled so that when the APL is high, the light emission luminance of the light source 2 is high, and when the APL is low, the light emission luminance of the light source 2 is low.

Since the intermediate control signal generated by the intermediate control signal generator 18 is a signal directly generated from the APL of the video signal, it is a signal that changes every unit field period following the change in the APL of the video signal. is there. Here, the intermediate control signal creation unit 18 has a change threshold level APLmin
Is set in advance, and A in the unit field period
When the PL change is smaller than the change threshold level APLmin, the intermediate control signal is controlled so as not to change.
By this processing, when the APL change of the video signal is very small, control is performed so that the light emission luminance of the light source 2 is not changed. Therefore, frequent changes in the light source driving conditions are reduced, and the light source is deteriorated due to the change in the light source driving conditions. Can be reduced.

The intermediate control signal generator 18 controls the light source luminance control following the unstable video signal when the video signal becomes unstable such as when the input video signal is switched. A light emission luminance control mute signal for prevention is input from the system control unit 34. Even when the light emission luminance control mute signal is on, the intermediate control signal is controlled so as not to change.

The signal change control section 19 converts the intermediate control signal, which changes every unit field period, into a light source control signal having a slowly changing speed according to a set time constant. Hereinafter, with reference to FIGS. 12A to 12C,
The change of the light emission state of the light source 2 under the control of the signal change control unit 19 will be described in detail.

FIG. 12A shows an example of the time change of the APL signal output from the APL detecting section 11, and FIG. 12B shows the time of the light emission luminance control mute signal when the input video signal is switched. FIG. 12C shows an example of the change, and FIG. 12C is driven by a light source control signal created based on the APL signal and the emission luminance control mute signal shown in FIGS. 12A and 12B. 3 shows a temporal change of the light emission luminance of the light source 2.

Now, the input video signal is changed from time t1 to t2.
In the following, a case where the video signal A is switched to the video signal B will be considered. It is assumed that the APL signal based on each video signal before and after the video signal switching is a signal as shown in FIG. At this time, the emission luminance control mute signal supplied to the intermediate control signal creation unit 18 is switched to the video signal B from the time t1 at which the video signal A switches as shown in FIG. Is controlled by the system control unit 34 so as to be in the on state until time t3 at which is stabilized. Since the intermediate control signal is controlled so as not to be changed while the light emission luminance control mute signal is in the on state, the intermediate light control signal generating unit 18 does not change the light source control signal.
As shown in (c), the light source emission luminance does not change between time t1 and time t3.

Next, let us consider a state in which the emission luminance control mute signal is turned off at time t3, and the control of the signal change creating unit 19 is restarted. For example, if the video signal A is
As shown in FIG. 2A, it is assumed that the APL is a low state before time t1 and the switched video signal B is a high APL state after time t2. In this case, as shown in FIG.
Immediately before switching, the light emission luminance of the light source 2 is in a low state, and while the light emission luminance control mute signal is in the on state,
The state where the light emission luminance is low is maintained. Thereafter, at time t3, the emission luminance control mute signal 111 is turned off,
If the control is continued by the signal change control unit 19 when the control by the intermediate control signal creation unit 18 is restarted, the signal change control unit 19 keeps the APL of the video signal B high even though it is constant. At 19, the tracking starts from the state immediately before the time t3, that is, the state where the light source luminance control level is low (the state of the broken line in FIG. 12C).
Therefore, a discrepancy occurs between the APL state of the actual image and the light emission luminance state of the light source, and an unnatural image is displayed.

Therefore, in the present embodiment, in order to solve the above-mentioned problem, an initial value setting signal newly generated by the system control unit 34 is introduced, and when the light emission luminance control mute signal is turned off, the initial value is simultaneously set. A value setting signal is sent to the signal change control unit 19 to reset the control state. This allows new control to be started from the point of reset, regardless of the past control history, so that an image that does not cause a sense of incongruity due to a mismatch between the light source emission luminance control at the time of switching the video signal and the display video does not occur. Display becomes possible.

Hereinafter, the signal change control section 19 will be described in detail. FIG. 13 shows a configuration of the signal change control unit 19. The signal change control unit 19 shown in FIG. 13 differs from the signal change control unit 13 shown in FIG. 3 only in that it newly includes a selector 701. The reference numerals are used and the description is omitted.

The selector 701 is controlled by an initial value control signal from the system control unit 34. Selector 701
Switches a signal to be fed back to the adder 302, the subtractor 303, and the comparator 301 according to the initial value control signal. More specifically, normally, the output of the selector 307 is supplied to each of the above units,
When receiving the initial value control signal from the system control unit 34 at the timing of the time t3 shown in FIG. 3C, that is, at the timing when the switching of the video signal is completed and the signal is stabilized, the intermediate control signal from the intermediate control signal generation unit 18 is received. Is supplied to each of the above units. By feeding back the intermediate control signal as it is after the signal switching, the past control state of the light source control signal can be reset, and the light source control signal can be immediately adjusted to a level corresponding to the APL of the current video signal.

As described above, according to the third embodiment,
Since the light emission luminance of the light source is controlled in conjunction with the level of the APL, in a dark scene with a low APL such as movie software, the light emission luminance of the light source is controlled in a lowering direction. In such a dark scene, the problem of the display image quality can be improved, and a higher quality image can be provided. In particular, by resetting the light source control signal by the initial value control signal, when the user does not want to continue the current control state, such as when switching the input video signal, the control of the light source luminance is started under a new condition. Can be. Therefore, it is possible to avoid the problem that the control state of the light source luminance does not match the display image state, and it is possible to display an image that does not cause any discomfort according to the state of the display image.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a video display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of an APL signal output from an APL detection unit 11 and a change over time of light emission luminance of a light source 2;

FIG. 3 is a block diagram illustrating a configuration of a signal change control unit 13;

FIG. 4 is a block diagram illustrating a configuration of a video display device according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a change over time of an APL signal output from an APL detection unit 11 and light emission luminance of a light source 2;

FIG. 6 is a block diagram illustrating a configuration of a signal change control unit 15;

FIG. 7 is a block diagram illustrating a configuration of a video display device according to a third embodiment of the present invention.

FIG. 8 is a diagram showing an example of an APL signal output from the APL detection unit 11 and a change over time of the light emission luminance of the light source 2;

FIG. 9 is a block diagram illustrating a configuration of a light source emission luminance state detection unit 17;

FIG. 10 is a diagram for explaining another control example that is compared for explaining the effect of the third embodiment.

FIG. 11 is a block diagram illustrating a configuration of a video display device according to a fourth embodiment of the present invention.

FIG. 12 shows an APL signal output from an APL detector 11, a mute signal from a system controller 34, and a light source 2;
FIG. 4 is a diagram showing an example of a temporal change of the light emission luminance of FIG.

FIG. 13 is a block diagram showing a configuration of a signal change control unit 19;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Display element 2 Light source 3 Reflecting mirror 4 Condensing lens 5 Projection lens 6 Screen 11 APL detection part 12 Intermediate control signal creation part 13 Signal change control part 14 Light source drive part 15 Signal change control part 16 Signal change control part 17 Light source light emission luminance State detection unit 18 Intermediate control signal creation unit 19 Signal change control unit 21 Video signal processing unit 22 Display element drive unit 31 System control unit 32 System control unit 33 System control unit 34 System control unit 301 Comparator 302 Adder 303 Subtractor 304 Selector 305 Difference calculator 306 Comparator 307 Selector 501 Comparator 502 Comparator 503 AND circuit 504 OR circuit 505 First timer circuit 506 Second timer circuit 701 Selector

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) G09G 3/36 G09G 3/36 H04N 5/74 H04N 5/74 Z (72) Inventor Takaaki Gyoten Osaka 1006 Kadoma, Kadoma Matsushita Electric Industrial Co., Ltd. JJ06 KK43

Claims (13)

[Claims] 1. An image display device for displaying an image by irradiating light from a light source to a display element having a transmissive or reflective light modulation function driven based on an input image signal, APL detecting means for detecting an average luminance level of the input video signal; and dynamically controlling light emission luminance of the light source based on the average luminance level detected by the APL detecting means in accordance with the average luminance level. A light source control signal generating means for generating a light source control signal for driving the light source in accordance with the light source control signal generated by the light source control signal generating means. Is related to a change in the average luminance level in which the amount of change in level per unit time in the light source control signal is detected by the APL detection means. Not so that a predetermined amount or less, and generates the light source control signal, the image display device. 2. The method according to claim 1, wherein the predetermined amount is a change amount such that a change in luminance of the light source is hardly perceived.
The video display device according to claim 1. 3. The image display device according to claim 2, wherein the predetermined amount is a change amount that requires at least 0.3 seconds to change the light emission luminance of the light source with a maximum control width. . 4. The light source control signal creating means according to claim 1, wherein:
The light source control is performed by sequentially adding or subtracting the predetermined amount to or from the level of the light source control signal output immediately before in the light source control signal generation unit in accordance with the average luminance level detected by the L detection unit. The video display device according to claim 1, wherein the video display device generates a signal. 5. An intermediate control signal generating unit that generates an intermediate control signal that changes in response to a change in the average luminance level detected by the APL detecting unit; 2. The video display device according to claim 1, further comprising: a signal change control unit configured to control a change in a level of the intermediate control signal created by the creation unit and generate the light source control signal. 6. The signal change control means according to claim 1, wherein a level difference between the light source control signal output immediately before in the signal change control means and the intermediate control signal generated by the intermediate control signal generating means is a predetermined error. If it is larger than the amount, the predetermined amount is added to or subtracted from the level of the light source control signal output immediately before and output as the light source control signal, while the level difference is larger than the predetermined error amount. 6. The image display device according to claim 5, wherein when the value is smaller, the intermediate control signal is output as the light source control signal as it is. 7. The light source control signal generating means detects when the input video signal is switched, regardless of the state of the light source control signal generated immediately before the switching occurs, by the APL detecting means. The image display device according to claim 1, wherein the light source control signal corresponding to the current average luminance level is generated. 8. An image display device for displaying an image by irradiating light from a light source to a display element having a transmissive or reflective light modulation function driven based on an input image signal, APL detection means for detecting an average luminance level of the input video signal; and a light source control signal for dynamically controlling light emission luminance of the light source in accordance with the average luminance level detected by the APL detection means Light source control signal creating means, and light source driving means for driving the light source in accordance with the light source control signal created by the light source control signal creating means, wherein the light source control signal creating means has an emission luminance of the light source. The amount of change in level per unit time of the light source control signal when lowering is larger than the amount of change when increasing the light emission luminance of the light source, Characterized by creating a source control signal, the image display device. 9. An image display device for displaying an image by irradiating light from a light source to a display element having a transmissive or reflective light modulation function driven based on an input image signal, APL detecting means for detecting an average luminance level of the input video signal; and dynamically controlling light emission luminance of the light source based on the average luminance level detected by the APL detecting means in accordance with the average luminance level. A light source control signal generating means for generating a light source control signal for generating the light source control signal, and a light source driving means for driving the light source based on the light source control signal generated by the light source control signal generating means. A state in which the light emission luminance of the light source is controlled at an intermediate level smaller than a maximum level and larger than a minimum level continues for a first predetermined period. , As to interrupt at least a second predetermined period of time dynamic control of the light source, characterized by generating said light source control signal, the image display device. 10. The light source control signal creating means, wherein after the second predetermined time has elapsed since the interruption of the dynamic control of the light source, the average luminance level detected by the APL detection means and 10. The video display device according to claim 9, wherein the dynamic control of the light source is restarted when the level difference from the average luminance level becomes within a predetermined difference. 11. An image display method for displaying an image by irradiating light from a light source to a display element having a transmission type or reflection type light modulation function driven based on an input image signal, An APL detecting step of detecting an average luminance level of the input video signal; and a light source driving step of dynamically driving the light source according to the average luminance level detected by the APL detecting step. Driving the light source such that the amount of change in the level of light emission luminance per unit time of the light source per unit time is equal to or less than a predetermined amount regardless of the change in the average luminance level detected by the APL detection step. Video display method. 12. An image display method for displaying an image by irradiating a light from a light source to a display element having a transmissive or reflective light modulation function driven based on an input video signal, An APL detecting step of detecting an average luminance level of the input video signal; and a light source driving step of dynamically driving the light source according to the average luminance level detected by the APL detecting step. The step is such that the amount of change in level per unit time of the light emission luminance of the light source when reducing the light emission luminance of the light source is larger than the change amount when increasing the light emission luminance of the light source. A video display method, comprising: 13. An image display method for displaying an image by irradiating light from a light source to a display element having a transmissive or reflective light modulation function driven based on an input image signal, An APL detecting step of detecting an average luminance level of the input video signal; and a light source driving step of dynamically driving the light source based on the average luminance level detected by the APL detecting step. The step of interrupting the dynamic control of the light source for at least a second predetermined period each time a state in which the light emission luminance of the light source is controlled at an intermediate level other than the maximum level and other than the minimum level continues for a first predetermined period; Driving the light source so that the image is displayed.