JP2004110050A - Video display device and video display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve quality of a display video by properly controlling a quantity of light radiated to display elements according to the features of a video scene. <P>SOLUTION: A video display device is provided with a histogram creation part 15, a light source control data creation part 16 for creating a light source control data for controlling a light source 6, and a light source driving circuit 5 for controlling the light source based on the light source control data. When a histogram distribution detected by the histogram distribution creation part 15 is in a predetermined distribution state, the light source control data creation part 16 fixes the quantity of light radiated to the display elements 8 at a predetermined level in accordance with this predetermined distribution state, and creates such a light source control data as the light quantity radiated to the display elements 8 continuously increases as the brightness level of the video signal 1 increases when the histogram distribution is off the predetermined distribution state. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an image display device and an image display method, and more particularly, to an image display by irradiating light from a light source to a single or a plurality of display elements having a transmissive or reflective light modulation action. The present invention relates to a video display device and a video display method for displaying a video.

As a display device having a transmission type or a reflection type light modulating function and a light source for irradiating the display device with light, there are a direct-view type liquid crystal display device and a projection type display device, a so-called projector. .

(4) In general, a direct-view type liquid crystal display device has a problem in that, compared to a self-luminous display device such as a CRT, a lack of brightness in a bright scene and a decrease in image quality due to a floating black in a dark scene. As a method of improving the quality of a display image of the direct-view type liquid crystal display device, display quality is improved by dimming the luminance of a light source. In some direct-view type liquid crystal display devices, light source luminance can be adjusted in addition to general contrast adjustment (adjustment of signal amplification gain) to make it easier to see the brightness level. In this case, the brightness of the light source is adjusted by the user's manual operation, and the light source brightness is fixed after the adjustment.

On the other hand, in projectors, rather than improving display quality, the aim is to reduce power consumption, adjust brightness (the purpose is to set the brightness to be easy to see for the screen size and environmental lighting conditions), and extend the life of the light source A light source having a light control function has been put to practical use. For the adjustment, the user manually switches the dimming level, and in the state after the adjustment, the light source luminance is fixed as in the case of the above-described direct-view type liquid crystal display device.

Both direct-view type liquid crystal display devices and projectors have a strong demand for improving the quality of displayed images with respect to lack of brightness in bright scenes and floating of black in dark scenes, as compared with self-luminous display devices such as CRTs. As a method of further improving the quality of a display image, a method of dynamically changing the luminance of a light source according to a scene of an image is described in, for example, “Liquid Crystal Display Device” (hereinafter simply referred to as “first liquid crystal display device”). Some devices have been devised, such as a “liquid crystal projector” described in Patent Document 2 (hereinafter, simply referred to as a second conventional device).

In the first conventional apparatus, features of an input video signal are detected from a maximum value, a minimum value, and an average luminance level (hereinafter, referred to as APL), and when a level difference between the maximum value and the minimum value is large, contrast control is performed. When the level difference is small, the contrast control is increased. When the APL is higher than a predetermined value, the luminance of the light source is decreased. In the first conventional device, the luminance of the display device is made to approach a constant in this way.

In the second conventional apparatus, the maximum value of the input video signal is detected, and when the maximum value is high, the light source luminance is increased, and when the maximum value is low, the light source luminance is decreased. The second conventional apparatus attempts to increase the relative contrast ratio between the case where the maximum value is high and the case where the maximum value is low.
JP-A-5-127608 JP-A-6-160811

As described above, the control of the light source luminance, which is put into practical use as a product in a direct-view liquid crystal display device and a projector, is a static fixed control and does not correspond to a dynamic change of an input video signal. Therefore, the quality of the display video in each scene of the input video signal cannot be improved. The first conventional device and the second conventional device described above dynamically control light source luminance in response to a dynamic change of an input video signal. However, these conventional devices have the following problems.

In the first conventional apparatus, the luminance of the light source is dynamically controlled in accordance with the input scene, but the purpose is to make the display luminance constant, and the black floating is not improved for a dark scene such as movie software. .

In the second conventional apparatus, the light source luminance is dynamically controlled in accordance with the input video signal. However, since the light source luminance is controlled in accordance with the maximum value of the input video signal, the maximum is locally controlled even though the APL is low. If the value is high, black floating may occur in a dark part of the video. The second conventional device is a “liquid crystal projector”, but a discharge type light source (xenon lamp, high-pressure mercury lamp, etc.) generally used for a projector is stably lit when a sudden change in driving conditions is repeated. It is conceivable that deterioration of lamp characteristics (defective lighting start-up, occurrence of flicker at the time of steady lighting) and deterioration of life characteristics occur, thereby impairing the reliability of the lamp.

Therefore, an object of the present invention is to provide a display device having a transmissive or reflective light modulating function and a light source for irradiating the display device with light, and to provide a display image with a high quality (contrast effect). Deficiency, floating black). Another object of the present invention is to improve the reliability of a light source, a diaphragm, or a dimming element for adjusting the amount of light when dynamically controlling the amount of light applied to a display element.

A first invention includes a histogram creating unit that divides a brightness level of an input video signal into a plurality of brightness level segments and detects a histogram distribution for each of the brightness level segments. When the detected histogram distribution for each of the divided sections is in a predetermined distribution state, regardless of the average luminance level detected by the APL detection means, the amount of light applied to the display element is changed to a predetermined value according to the predetermined distribution state. It is characterized in that light quantity control data that is fixed at a level is created.

In a second aspect based on the first aspect, the light quantity control data creating means has a histogram distribution of at least one brightness level among the plurality of brightness level sections detected by the histogram creating means being smaller than a predetermined threshold value. When the brightness is large or small, light amount control data for fixing the light amount applied to the display element at a predetermined level regardless of the average luminance level detected by the APL detection means is created.

In a third aspect based on the first aspect, the light amount control data creating means determines that a video scene related to the input video signal is a dark scene based on the histogram distribution detected by the histogram creating means. It is characterized in that light amount control data is generated such that the light amount irradiated on the display element is fixed at a predetermined minimum level regardless of the average luminance level detected by the APL detecting means.

According to the first aspect, by controlling the amount of light emitted to the display element based on the histogram distribution, it is possible to more accurately extract features of a video scene that cannot be uniquely determined from only the APL detection result. In addition, it is possible to more appropriately control the amount of light applied to the display element according to the characteristics of the image scene, and to improve the quality of the displayed image.

According to the second aspect, the feature of the video scene can be easily extracted by comparing the histogram distribution of the video signal at a certain luminance level with a predetermined threshold value.

According to the third aspect, even in a case where only a part of the dark scene has a particularly bright part, and even when it is not possible to determine that the scene is a dark scene from the APL detection result, the dark scene is dark. By judging that the scene is a scene, it is possible to control the amount of light emitted to the display element so as to prevent floating of black.

Hereinafter, various embodiments of the present invention will be described with reference to the drawings.
(1st Embodiment)
FIG. 1 shows a configuration of a video display device according to the first embodiment of the present invention. The image display device includes an APL detection unit 2, a light source control data creation unit 3, an LPF 4, a light source drive circuit 5, a light source 6, an optical system 7, a display element 8, a video signal processing circuit 9, The device includes an element driving unit 10, a microcomputer 11, and a timer 12. The optical system 7 is provided when the image display device is a projector, but is not provided when the image display device is a direct-view type. Hereinafter, the operation of the first embodiment will be described.

映像 The video signal is supplied to the video display device. The video signal 1 is input to the video signal processing circuit 9 and the APL detector 2. The video signal 1 input to the video signal processing circuit 9 is subjected to signal processing necessary for the display device such as contrast control and brightness control, and then adapted to the light modulation action of the display element 8 via the display element driving unit 10. The drive signal is input to the display element 8. Since the signal processing in the video signal processing circuit 9 and the display element driving unit 10 is well known, detailed description is omitted.

The APL detector 2 detects the APL from the luminance signal component of the input video signal 1 for each unit field period, and outputs the detection result to the light source control data generator 3. The light source control data creating unit 3 creates light source control data according to the APL detection result. The created light source control data is input to the light source driving circuit 5 via the LPF 4. The light source driving circuit 5 drives the light source 6 under driving conditions according to the light source control data. The light emitted from the light source 6 is converged by the optical system 7 and is applied to the display element 8 as illumination light corresponding to the display range of the display element 8. The microcomputer 11 and the timer 12 control the APL detector 2 and the light source control data generator 3 in order to control the time axis when the APL is detected and when the light source control data is generated.

Next, specific processing contents of the light source control data creation unit 3 and the operation of the LPF 4 will be described with reference to FIGS.
Taking the discharge lamp used in the projector as an example, as shown in FIG. 2, the range of the light source driving power level from L1 (min) to L2 (max) is an area where the light source is stably turned on. When the level of the light source driving power is smaller than L1 (min), the light source cannot be stably turned on. Therefore, when varying the driving power of the light source, it is necessary to drive the light source in the power range of the stable lighting region (L1 (min) to L2 (max)). Therefore, dynamic light source control according to the APL of the input video signal 1 in the present embodiment is also performed using the stable lighting region.

FIG. 2 shows, for reference, an input image when the power of the light source is linearly changed from L1 (min) to L2 (max) with respect to the change range (0% to 100%) of the APL of the input image signal 1. The relationship between the APL of the signal 1 and the light source control level is shown by a dotted line. In this case, the light source control level becomes the minimum value L1 (min) in the stable lighting region only when the APL of the input video signal 1 is 0%. Therefore, when the APL is, for example, B1 shown in the figure, the light source control level is not reduced so much in spite of a dark scene, and black floating is not prevented. Further, the light source control level becomes the maximum value L2 (max) = 100% in the stable lighting region only when the APL of the input video signal 1 is 100%. Therefore, when the APL is, for example, B2 shown in the figure, the light source control level does not reach the maximum in spite of a bright scene, and the brightness of the white peak is impaired.

However, especially when using movie software, a movie has a relatively large number of dark scenes over the entire screen, so that the influence of the floating black is great, and the occurrence of the floating black greatly degrades the display quality of an image. Therefore, it is preferable to prevent black floating as much as possible in dark scenes.

Also, when a person views movie software, the contrast is high when the brightness level in a bright scene is large as compared with the dark adaptation memory in a dark scene. Conversely, when the black level in a dark scene is low as compared with the photoadaptive memory in a bright scene, the contrast is felt to be high. Enhancing the sense of contrast is important for improving the display quality of an image. Therefore, it is not preferable that the occurrence of black floating or the loss of the brightness of the white peak in a bright scene leads to a decrease in contrast.

In the present embodiment, in view of the above, power control of a light source as shown in FIG. 3 is performed in order to further improve the display quality of an image. A1 and A2 shown in FIG. 3 are preset APL threshold values. The threshold levels A1 and A2 are thresholds for distinguishing between dark and bright scenes, respectively, and are obtained by evaluation of movie software. For example, when using software having many bright scenes other than movie software, the setting of these thresholds may be changed according to the video source.

In FIG. 3, in the first mode of light source control (fixed area Low), when the APL of the input video signal 1 is smaller than the threshold value A1, the light source control level is fixed at L1 (min). In the second mode (variable corresponding area), when the APL of the input video signal 1 is the threshold value A1 to the threshold value A2, the APL of the input video signal 1 ranges from L1 (min) to L2 (max) according to the change of the APL. Vary the light source control level. In the third mode (fixed area High), when the APL of the input video signal 1 is larger than the threshold value A2, the light source control level is fixed at L2 (max).

In FIG. 3, the relationship between the APL and the light source control level in the variable correspondence area is linear, but the relationship is not limited to this. For example, the relationship between the light source control level and the light source drive power, or the light source drive power and the light emission intensity of the light source If the relationship is nonlinear, a function may be used that performs inverse correction of the nonlinear characteristic in this variable corresponding region. Further, the function is not limited to the inverse correction of the nonlinear characteristic, and may be an arbitrary nonlinear characteristic function.

Next, the relationship between the dynamic change of the APL of the input video signal 1 and the dynamic control of the light source control level will be specifically described with reference to FIG. In FIG. 4, the upper diagram shows a specific example of the dynamic change of the input APL to the light source control data generator 3, and the lower diagram shows the dynamics of the light source control level corresponding to the dynamic change of the input APL shown in the upper diagram. This shows the objective control. In particular, in the lower diagram, the solid line indicates an output signal from the light source control data creation unit 3, and the dotted line indicates an output signal from the LPF 4. Tn is a unit field time for detecting APL. As shown in FIG. 4, according to the present embodiment, in accordance with the control method shown in FIG. 3, when the APL is in the variable corresponding area (A1 to A2), the light source control is also activated. When the APL becomes the fixed area Low and the fixed area High, the light source control level is controlled to be constant at L1 (min) and L2 (max), respectively.

Next, the operation of the LPF 4 will be described. As described above, the dynamic change indicated by the solid line in the lower part of FIG. 4 indicates an output signal from the light source control data creation unit 3, that is, an input signal to the LPF 4, and the LPF 4 has a predetermined time constant. The output signal changes as indicated by the dotted line in the lower part of FIG. 4 and drives the light source 6 via the light source driving circuit 5. In the case of a discharge lamp, a sudden change in the driving power affects the state of the discharge arc, causing deterioration of the lamp electrodes and impairing the reliability of the lamp. Therefore, in the present embodiment, the drive power is varied with a time constant using the LPF 4 so that the reliability of the lamp does not decrease in the transient state in which the drive power is varied. The specific circuit of the LPF 4 is omitted because it is well known, but may be an analog LPF or a digital LPF. When a digital LPF is used as the LPF 4, it may be converted into an analog signal in the processing of the light source driving circuit 5. Note that, instead of the LPF 4, other means for giving a delay effect to the output signal from the light source control data creation unit 3 may be used.

When the dynamic control described in FIG. 4 is shown in the same format as that of FIG. 3, as shown in FIG. 5, when the APL is in the variable corresponding area (A1 to A2), the light source control level is indicated by an arrow shown in the figure. As described above, the stable lighting area dynamically changes according to the APL change of the input video signal 1.

As described above, according to the first embodiment, by dynamically driving the light source, it is possible to dynamically adjust the luminance according to the scene of the image, and the lack of brightness in a bright scene is insufficient. In addition, the problem of floating black in a dark scene can be improved, and the sense of contrast can be enhanced. Further, in the case of a dark scene, that is, when the APL of the input video signal is smaller than a predetermined threshold value, the light source control level is set to the minimum value of the stable lighting region. In addition, in the case of a bright scene, that is, when the APL of the input video signal is larger than a predetermined threshold value, the light source control level is set to the maximum value of the stable lighting area. The contrast can be further improved, and as a result, the sense of contrast can be further enhanced.

In the present embodiment, when the APL becomes the fixed area Low and the fixed area High, the light source control level is controlled to be constant at L1 (min) and L2 (max), but the driving of the light source is not necessarily performed. The level does not need to be constant at the minimum level or the maximum level, and even at levels near those levels, the problem of black floating in dark scenes and lack of brightness in bright scenes as described above is further improved. Needless to say, the effect to be obtained is obtained. However, if the driving is fixedly performed at the minimum level or the maximum level as in the present embodiment, the effects can be obtained to the maximum, and the driving level of the light source does not fluctuate in dark and bright scenes. It is more preferable because the problem of deterioration of the properties can be improved.

In the present embodiment, as shown in FIG. 4, the light source control level is controlled in accordance with the APL for each unit field time Tn. May be calculated, and the light source control level may be controlled based on the average value. For example, assuming that Tn (unit field time) in the upper part of FIG. 4 is T2k = (Tn−k + Tn−k + 1 +. Replace with By doing so, the period and amount of dynamic change of the dotted arrow shown in FIG. 5 are reduced. That is, the fluctuation cycle of the light source control level in the variable corresponding region of the APL becomes large, and the amount of change becomes small. Therefore, a decrease in the reliability of the lamp can be further reduced. This effect will be described more specifically with reference to FIG. FIG. 6 shows the case where k = 1, and the bold dotted line in the upper figure shows the average of the APL detection results for each of the three unit fields. Based on this average, the light source control level is controlled as shown in the lower diagram of FIG. Therefore, by controlling the light source based on the average of the APLs for a plurality of unit field times, the fluctuation of the light source control level is reduced as compared with the case shown in FIG. 4, and the decrease in the reliability of the light source can be further reduced. it can.

Although not shown, an LPF may be inserted at the output side of the APL detection unit 2 as a configuration that can provide an effect similar to the control based on the average of the APLs of the plurality of unit field times. . However, in the case of the control based on the average of the APL, the number of target fields can be accurately defined as an integer as the value of k, and the value of k can be appropriately changed according to the situation by setting a program or the like. Since it is possible, for example, in the variable corresponding area shown in FIG. 5, a control method of changing the change speed between when the light source luminance is increased and when the light source luminance is decreased is also possible.

Although the case where the light source is dynamically controlled has been described as the first embodiment, the present invention is similarly applied to other cases where the amount of light finally irradiated on the display element can be controlled. Can be. Hereinafter, the configuration and operation of the video display device in the case where the light source control method according to the present embodiment is applied to the control of an aperture and the control of a light control element will be described.

FIG. 7 is a block diagram showing a configuration of a video display device when the light source control method according to the first embodiment is applied to aperture control. 7, the image display device includes an APL detection unit 2, an aperture control data creation unit 19, an aperture drive circuit 20, a light source drive circuit 5, a light source 6, an optical system 17, a display element 8, an image It includes a signal processing circuit 9, a display element driving unit 10, a microcomputer 11, and a timer 12. The optical system 17 includes a stop 18. In FIG. 7, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Hereinafter, the operation of the video display device will be described.

The aperture control data creation unit 19 creates aperture control data according to the APL detection result. The created aperture control data is input to the aperture drive circuit 20. The iris drive circuit 20 dynamically drives the iris 18 under driving conditions according to the iris control data, and varies the amount of light blocking of the iris 18. The light emitted from the light source 6 is converged by the optical system 17 and applied to the display element 8 as illumination light corresponding to the display range of the display element 8. At this time, the amount of light applied to the display element 8 is adjusted according to the amount of light blocking of the diaphragm 18.

Next, with reference to FIGS. 8 and 9, specific processing contents of the aperture control data creation unit 19 will be described.
A1a and A2a shown in FIG. 8 are preset APL threshold values. The threshold levels A1a and A2a are thresholds for distinguishing between dark scenes and bright scenes, respectively, and are obtained by evaluation of movie software. For example, when using software having many bright scenes other than movie software, the setting of these thresholds may be changed according to the video source.

In FIG. 8, in the first mode of light quantity control (fixed area Low), when the APL of the input video signal 1 is smaller than the threshold value A1a, the light quantity control level is fixed at L1a (min). In the second mode (variable corresponding area), when the APL of the input video signal 1 is in the range of the threshold A1a to the threshold A2a, the APL of the input video signal 1 ranges from L1a (min) to L2a (max) according to the change in APL. Vary the light control level. In the third mode (fixed area High), when the APL of the input video signal 1 is larger than the threshold value A2a, the light source control level is fixed at L2a (max).

In FIG. 8, the relationship between the APL (A1a to A2a) and the light source control level in the variable corresponding region is linear, but the relationship is not limited to this and may be an arbitrary nonlinear characteristic function.

Next, the relationship between the dynamic change of the APL of the input video signal 1 and the dynamic control of the light amount control level will be specifically described with reference to FIG. In FIG. 9, the upper diagram shows a specific example of the dynamic change of the input APL to the aperture control data generator 19, and the lower diagram shows the dynamics of the light amount control level corresponding to the dynamic change of the input APL shown in the upper diagram. This shows the objective control. Tn is a unit field time for detecting APL. According to the control method shown in FIG. 8 described above, when the APL is in the variable corresponding area (A1a to A2a), the light quantity control dynamically follows the dynamic change of the APL. When the fixed area becomes High, the light amount control level is controlled to be constant at L1a (min) and L2a (max), respectively.

The output signal from the aperture control data creation unit 19 shown in the lower diagram of FIG. 9 is not limited to the case shown by the solid line, but takes into account the responsiveness and reliability of the aperture driving structure as shown by the dotted line. Thus, a time delay characteristic may be provided for a change in APL.

As described above, when the APL is in the variable corresponding area (A1a to A2a), the light amount control level dynamically transitions in the variable corresponding area according to the APL change of the input video signal 1, as indicated by the arrow in FIG. I do.

As described above, according to the video display device shown in FIG. 7, by dynamically driving the aperture, the light amount can be dynamically adjusted according to the video scene, and the brightness perception in a bright scene can be improved. And the problem of floating black in dark scenes can be improved, and the sense of contrast can be enhanced. Further, in the case of a dark scene, that is, when the APL of the input video signal is smaller than a predetermined threshold value, the light amount control level is set to the minimum value of the aperture control region, so that the problem of black floating in a dark scene can be further improved. In addition, in a bright scene, that is, when the APL of the input video signal is larger than a predetermined threshold value, the light amount control level is set to the maximum value of the aperture control area. The contrast can be further improved, and as a result, the sense of contrast can be further enhanced.

Further, when controlling the light source, the minimum value L1 of the light source control is relatively large from the viewpoint of stable lighting of the light source (about 1/3 to 1/2 of the maximum value L2), and the light amount is sufficiently low in a dark scene. However, when controlling the aperture, the minimum value L1a of the light amount control can be made sufficiently small (in principle, 0 is also possible). As a result, in a dark scene, the black level can be sufficiently reduced, the black floating feeling can be improved more favorably, and the relative contrast ratio with a bright scene can be increased.

In addition, when controlling the light source, there is a problem that the life time is impaired if the change speed of the light source power is increased or the number of times of the change is large, from the viewpoint of the life reliability of the discharge light source used in the projector. In the case of controlling the aperture, the speed of change and the number of changes in the drive condition of the aperture have less influence on the reliability of the aperture drive structure than in the case of controlling the light source, although it depends on the opening / closing structure of the aperture. Therefore, for example, it is possible to make the aperture driving condition follow the change of the APL on a field / frame basis, and it is possible to greatly improve the followability when the brightness of the video scene changes sharply. Thus, a better sense of contrast can be obtained according to a change in the brightness of the scene.

Discharge light sources used in projectors are roughly classified into xenon light sources and high-pressure mercury light sources. Compared with xenon light sources, high-pressure mercury light sources are more difficult to ensure reliability in the above points, and drive power (brightness) is lower. If it is changed, the emission spectrum tends to change. Therefore, when a high-pressure mercury light source is used, controlling the aperture is particularly effective.

It is also possible to control both the light source and the aperture at the same time. In this case, the effect of improving the contrast is obtained by multiplying the effect of improving the contrast by controlling the light source and the effect of improving the contrast by controlling the aperture. At this time, by setting the changing speed of the aperture to be faster than the changing speed of the light source, it is possible to eliminate the adverse effect on the life reliability of the light source and to improve the followability of the light amount to the change of the image scene. Can be

FIG. 10 is a block diagram illustrating a configuration of a video display device in a case where the light source control method according to the first embodiment is applied to dimming element control. In FIG. 10, the image display device includes an APL detection unit 2, a dimming element control data creating unit 22, a dimming element driving circuit 23, a light source driving circuit 5, a light source 6, a dimming element 21, an optical A system 7, a display element 8, a video signal processing circuit 9, a display element driving unit 10, a microcomputer 11, and a timer 12 are provided. In FIG. 10, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the configuration shown in FIG. 10, the dimming element 21 is provided at a stage preceding the optical system 7, but the dimming element 21 may be provided inside the optical system 24 as shown in FIG. Hereinafter, the operation of the video display device shown in FIG. 10 will be described.

(4) The dimming element control data creating unit 22 creates dimming element control data according to the APL detection result. The created dimming element control data is input to the dimming element drive circuit 23. The dimming element driving circuit 23 dynamically drives the dimming element 21 under driving conditions according to the dimming element control data, and changes the transmittance of the dimming element 18. The light emitted from the light source 6 passes through the light control element 21, is converged by the optical system 7, and is applied to the display element 8 as illumination light corresponding to the display range of the display element 8. At this time, the amount of light applied to the display element 8 is adjusted according to the transmittance of the light control element 21.

Next, with reference to FIG. 12 and FIG. 13, specific processing contents of the light control element control data creation unit 22 will be described.
A1b and A2b shown in FIG. 12 are APL threshold values set in advance. The threshold levels of A1b and A2b are thresholds for distinguishing between dark scenes and bright scenes, respectively, and are obtained by evaluation of movie software. For example, when using software having many bright scenes other than movie software, the setting of these thresholds may be changed according to the video source.

In FIG. 12, in the first mode of light quantity control (fixed area Low), when the APL of the input video signal 1 is smaller than the threshold value A1b, the light quantity control level is fixed at L1a (min). In the second mode (variable corresponding area), when the APL of the input video signal 1 is in the range of the threshold value A1b to the threshold value A2b, the APL of the input video signal 1 ranges from L1b (min) to L2b (max) according to the change in APL. Vary the light control level. In the third mode (fixed area High), when the APL of the input video signal 1 is larger than the threshold value A2b, the light source control level is fixed at L2b (max).

In FIG. 12, the relationship between the APL (A1b to A2b) and the light source control level in the variable correspondence region is linear, but the relationship is not limited to this and may be an arbitrary nonlinear characteristic function.

Next, the relationship between the dynamic change of the APL of the input video signal 1 and the dynamic control of the light amount control level will be specifically described with reference to FIG. In FIG. 13, the upper diagram shows a specific example of the dynamic change of the input APL to the dimming element control data creation unit 22, and the lower diagram shows the light amount control level corresponding to the dynamic change of the input APL shown in the upper diagram. FIG. Tn is a unit field time for detecting APL. According to the control method shown in FIG. 12, when the APL is in the variable corresponding region (A1b to A2b), the light amount control dynamically follows the dynamic change of the APL. When the fixed area becomes High, the light amount control level is controlled to be constant at L1b (min) and L2b (max), respectively.

Note that the output signal from the dimming element control data creation unit 22 shown in the lower diagram of FIG. 13 is not limited to the case shown by the solid line, but takes into account the responsiveness and reliability of the dimming element as shown by the dotted line. Then, a change in APL may be given a time delay characteristic.

As described above, when the APL is in the variable corresponding area (A1b to A2b), the light amount control level dynamically transitions in the variable corresponding area according to the APL change of the input video signal 1, as indicated by the arrow in FIG. I do.

As described above, according to the video display device shown in FIG. 10 or FIG. 11, by dynamically driving the dimming element, it becomes possible to dynamically adjust the light amount according to the video scene, and And the problem of black floating in dark scenes can be improved, and the sense of contrast can be enhanced. Further, in a dark scene, that is, when the APL of the input video signal is smaller than a predetermined threshold value, the light amount control level is set to the minimum value of the dimming control area. In addition, in a bright scene, that is, when the APL of the input video signal is larger than a predetermined threshold value, the light amount control level is set to the maximum value of the dimming control area. Can be further improved, and as a result, the contrast feeling can be further enhanced.

In controlling the dimming element, generally, the same effects as in the case of controlling the aperture can be obtained. Further, as compared with the case where the light source is controlled, the case where the dimming device is controlled can be realized more easily because the dimming device driving circuit can be realized with a relatively simple circuit at a low voltage. Furthermore, when controlling the dimming element, there is more freedom in the arrangement between the light source and the display element than when controlling the aperture. , And can be realized with a relatively simple structure, so that it can be realized more easily.

Note that it is possible to perform both the light source control and the dimming element control at the same time.In this case, however, it is possible to obtain the same effect as in the case where both the light source control and the aperture control are performed simultaneously. it can. Further, it is also possible to simultaneously control the light source, the aperture, and the dimming element. In this case, the contrast improvement effect is obtained by controlling the light source and the contrast by controlling the aperture. Is obtained by multiplying the effect of improving the contrast and the effect of improving the contrast by controlling the dimming element, so that the improvement of the contrast is more effective.

(Second embodiment)
FIG. 14 shows a configuration of a video display device according to the second embodiment of the present invention. The image display device includes an APL detection unit 2, a light source control data creation unit 13, an LPF 4, a light source drive circuit 5, a light source 6, an optical system 7, a display element 8, a video signal processing circuit 9, The device includes an element driving unit 10, a microcomputer 11, and a timer 12. Note that this embodiment is different from the first embodiment only in the operation of the light source control data creation unit 13. Therefore, the same reference numerals are given to the other same components, and the description is omitted.

The operation of the light source control data creation unit 13 will be described with reference to FIG. The light source control data creation unit 13 performs a process for relaxing the dynamic follow-up characteristic of the light source level control with respect to the change in the APL, in addition to the process of the light source control data creation unit 3 in the first embodiment. As a result, the frequency of the state transition of the driving power condition of the lamp is reduced, and the decrease in the reliability of the lamp is further improved. Hereinafter, a specific description will be given with reference to FIG.

FIG. 15 shows the relationship between the dynamic change of the APL of the input video signal 1 and the dynamic control of the light source control level. In FIG. 15, the upper diagram shows a specific example of the dynamic change of the input APL to the light source control data creation unit 13, and the lower diagram shows the dynamic of the light source control level corresponding to the dynamic change of the input APL shown in the upper diagram. This shows the objective control. In particular, in the figure below, a solid line indicates an output signal from the light source control data creation unit 13, and a dotted line indicates an output signal from the LPF 4. Tn is a unit field time for detecting APL. As shown in FIG. 15, in the present embodiment, similarly to the first embodiment, according to the control method shown in FIG. In the case of ()), the light source control dynamically follows, but when the APL becomes the fixed region Low and the fixed region High, the light source control level is controlled to be constant at L1 (min) and L2 (max), respectively. .

However, in the present embodiment, it is determined whether or not the change in the input APL is smaller than a preset threshold value APmin. If the change in the APL is smaller than APmin, priority is given to the above-described normal control. Thus, the light source control level is not changed. More specifically, in the upper diagram of FIG. 15, the change level of the APL at the time t1 to t2 is smaller than the determination threshold value APmin. Therefore, as shown in the lower diagram of FIG. 15, the dynamic change control of the light source control level is not performed at time t2, and the light source control level at time t1 is maintained.

In the present embodiment, as described above, the light source control level is not made to follow a minute change in APL. This is because causing the light source control level to follow each minute APL fluctuation has a disadvantage that the reliability of the light source is impaired is greater than an advantage of improving the contrast, which is not preferable.

As described above, according to the second embodiment, in addition to the effects of the first embodiment, when the change in the APL is small, the driving condition immediately before is maintained without changing the driving condition of the light source. In addition, the frequency of the dynamic transition of the driving condition of the light source can be reduced. As a result, it is possible to improve the problem of the deterioration of the stable lighting property of the light source and the deterioration of the life characteristic, and to enhance the reliability of the light source.

The control method according to the second embodiment can be applied to control of a diaphragm and a light control element. Hereinafter, the case where the control method of the second embodiment is applied to the control of the aperture and the control of the light control element will be described.

FIG. 16 shows the relationship between the dynamic change of the APL of the input video signal 1 and the dynamic control of the aperture control level when the control method of the second embodiment is applied to aperture control. In this case, if the change in APL is smaller than a preset determination threshold value APmin, the light amount control level is not changed. Thus, it is possible to prevent a reduction in the reliability of the aperture drive structure due to the aperture drive structure repeating an excessively small movable operation.

FIG. 17 shows the relationship between the dynamic change of the APL of the input video signal 1 and the dynamic control of the dimming element control level when the control method of the second embodiment is applied to the control of the dimming element. . Also in this case, if the change in APL is smaller than the predetermined threshold value APmin, the light amount control level is not changed. Thus, it is possible to prevent a decrease in the reliability of the light control element due to the light control element repeating an excessively small light control operation.

(Third embodiment)
FIG. 18 shows a configuration of a video display device according to the third embodiment of the present invention. The image display device includes an APL detection unit 2, a light source control data creation unit 14, an LPF 4, a light source drive circuit 5, a light source 6, an optical system 7, a display element 8, a video signal processing circuit 9, a display The device includes an element driving unit 10, a microcomputer 11, and a timer 12. Note that this embodiment is different from the first embodiment only in the operation of the light source control data creation unit 14. Therefore, the same reference numerals are given to the other same components, and the description is omitted.

The operation of the light source control data creation unit 14 will be described with reference to FIG. The light source control data creation unit 14 performs a process for relaxing dynamic follow-up characteristics of the light source level control with respect to a change in APL, in addition to the process of the light source control data creation unit 3 in the first embodiment. As a result, the frequency of the state transition of the driving power condition of the lamp is reduced, and the decrease in the reliability of the lamp is further improved. Hereinafter, a specific description will be given with reference to FIG.

FIG. 19 shows the relationship between the dynamic change of the APL of the input video signal 1 and the dynamic control of the light source control level. In FIG. 19, the upper diagram shows a specific example of the dynamic change of the input APL to the light source control data creation unit 14, and the lower diagram shows the dynamic of the light source control level corresponding to the dynamic change of the input APL shown in the upper diagram. Shows objective control. In particular, in the figure below, the solid line indicates an output signal from the light source control data creation unit 14, and the dotted line indicates an output signal from the LPF 4. Tn is a unit field time for detecting APL. As shown in FIG. 19, in the present embodiment, similarly to the first embodiment, according to the control method shown in FIG. In the case of ()), the light source control dynamically follows, but when the APL becomes the fixed region Low and the fixed region High, the light source control level is controlled to be constant at L1 (min) and L2 (max), respectively. .

However, in this embodiment, it is determined whether or not the light source drive level has transitioned to L1 (min) or L2 (max). Hold the drive level.

More specifically, in the upper diagram of FIG. 19, the APL at time t10 becomes smaller than the threshold value A1, and the light source control level transitions to the level of L1 (min) as shown in the lower diagram of FIG. I do. Once the driving condition of the light source transitions to L1 (min), the light source control data creation unit 14 holds the output in the state of L1 (min) regardless of the change in APL during the predetermined period T1. When the period T1 ends at time t12, a normal process according to the APL change is performed as in the first embodiment.

Similarly, APL at time t20 becomes larger than threshold value A2, and the light source control level makes a state transition to the level of L2 (max). Once the drive condition of the light source transitions to L2 (max), the light source control data creation unit 14 holds the output in the state of L2 (max) regardless of the change in APL during the predetermined period T2. When the period T2 ends at the time t22, a normal process according to the APL change is performed as in the first embodiment.

In the present embodiment, as described above, once the light source drive level transitions to L1 (min) or L2 (max), the light source control level is prevented from following the change in APL for a predetermined period. This has the effect of reducing the frequency of the dynamic transition of the driving conditions of the light source, improves the problem of the deterioration of the stable lighting property of the light source and the deterioration of the life characteristic, and can enhance the reliability of the light source. Further, there is another advantage in holding the output, particularly when the light source control level transits to L1 (min). For example, when the APL frequently changes before and after A1, unless the light source control level is held as in the present embodiment, the scene is a relatively dark scene, so that the change in the light source luminance is easily perceived. This is because human vision is more sensitive to a change in brightness in a dark scene than to a change in brightness in a bright scene, and is more sensitive to a change in brightness. Therefore, preventing frequent brightness fluctuations before and after A1 of APL is also effective for improving the quality of displayed images.

As described above, according to the third embodiment, in addition to the effects of the first embodiment, once the light source drive level transitions to L1 (min) or L2 (max), the drive condition of the light source is changed. Since the immediately preceding driving condition is retained, the frequency of dynamic transition of the driving condition of the light source can be reduced. As a result, it is possible to improve the problem of the deterioration of the stable lighting property of the light source and the deterioration of the life characteristic, improve the reliability of the light source, and improve the quality of the displayed image.

In the present embodiment, the light source control level is maintained for a predetermined period from the time when the input APL transits to A1 or less or A2 or more. However, the present invention is not limited to this. The light source control level may be maintained for a predetermined period from the time when the light source control has been performed, or the light source control level may be maintained for a predetermined period from another timing. Hereinafter, this modified example will be described with reference to FIG.

In this modification, the light source control data creation unit performs a digital processing operation to control the variable characteristic of the light source control level with a time delay as shown in the lower diagram of FIG. Performed by Specifically, in the upper diagram of FIG. 20, the APL at time t10 becomes smaller than the threshold value A1, and the light source control level is reduced at time t11 by the time delay effect in the light source control data generation unit. As shown in the lower diagram, the state transits to the level of L1 (min). Once the driving condition of the light source transits to L1 (min), the output is held at L1 (min) regardless of the change in APL during a predetermined period T1 '. When the period T1 'ends at time t12, a normal process according to the APL change is performed as in the first embodiment.

Similarly, the APL at time t20 becomes larger than the threshold value A2, and the light source control level transits to the level of L2 (max) at time t21 due to the time delay effect of the light source control data creation unit. Once the driving condition of the light source transits to L2 (max), the output is held in the state of L2 (max) regardless of the change in APL during a predetermined period T2 '. When the period T2 'ends at time t22, a normal process according to the APL change is performed as in the first embodiment.

The control method according to the third embodiment can be applied to control of a diaphragm and a light control element. For example, when the control method of the present embodiment is applied to the diaphragm dynamic control shown in FIG. 8, the light amount control level is set to L1a for a predetermined period from when the input APL transits to A1a or less or A2a or more. (Min) or L2a (max). As a result, the frequency of the dynamic transition of the aperture driving condition can be reduced, and as a result, a reduction in the reliability of the aperture driving structure can be prevented. On the other hand, when the control method of the present embodiment is applied to the dynamic control of the dimming device shown in FIG. 12, for example, the light amount control is performed for a predetermined period from when the input APL transitions to A1b or less or A2b or more. The level is maintained at L1b (min) or L2b (max), respectively. Thereby, the frequency of dynamic transition of the driving condition of the light control device can be reduced, and as a result, the reliability of the light control device can be prevented from lowering.

(Fourth embodiment)
FIG. 21 shows a configuration of a video display device according to the fourth embodiment of the present invention. The image display device includes an APL detection unit 2, a histogram creation unit 15, a light source control data creation unit 16, an LPF 4, a light source drive circuit 5, a light source 6, an optical system 7, a display element 8, a video signal It includes a processing circuit 9, a display element driving unit 10, a microcomputer 11, and a timer 12. Note that the present embodiment is different from the first embodiment only in the point that a histogram creating unit 15 is newly provided and the operation of the light source control data creating unit 16. Therefore, the same reference numerals are given to the other same components, and the description is omitted.

In FIG. 21, the video signal 1 is input to the video signal processing circuit 9, the histogram creation unit 15, and the APL detection unit 2. The histogram creating unit 15 detects a histogram distribution for each division obtained by dividing the input video signal level into a plurality of arbitrary luminance level divisions from the luminance signal component of the input video signal 1 for each unit field period. This detection result is input to the light source control data creation unit 16. The light source control data creating unit 16 creates light source control data based on the APL detection result and the histogram creation result.

Hereinafter, a specific operation of the histogram creating unit 15 will be described with reference to FIG. In the histogram creating unit 15, the signal level from 0% to 100% is divided in advance into a plurality of luminance levels (four divisions H1 to H4 in the figure). Is detected for each unit field. This histogram creation result is input to the light source control data creation unit 16.

The light source control data creation unit 16 compares the value in the section H1 closest to the black level among the divided sections with a predetermined threshold value HTL. As a result of the comparison, when the value in the section H1 is smaller than the HTL, the light source control data creating unit 16 performs the dynamic change of the APL according to the control method shown in FIG. 3 similarly to the first embodiment. On the other hand, when the APL is in the variable corresponding area (A1 to A2), the light source control dynamically follows, but when the APL becomes the fixed area Low and the fixed area High, the light source control level is set to L1 ( min) and L2 (max) are controlled to be constant.

On the other hand, when the value in the section H1 is larger than the HTL, it is determined that the scene is a dark scene regardless of the APL, and the light source control data creation unit 16 gives priority to the normal control similar to that in the first embodiment. Then, the light source drive control level is set to L1 (min) to improve black floating of the displayed image. When only a part of a dark scene includes a particularly bright part, the APL becomes large under the influence of the particularly bright part, so that the APL cannot determine that the scene is a dark scene. On the other hand, by determining a dark scene based on the histogram distribution as in the present embodiment, it is possible to determine that a dark scene is a dark scene even when only a part of the dark scene has a particularly bright part. .

In the present embodiment, the number of divided sections in the histogram distribution is four, but the number is not limited to this and may be an arbitrary number of divided sections. Further, although the division range (width) of each division luminance level is 25% width, it is not limited to this, and may be an arbitrary division range, and the size of the range differs for each division division. It does not matter.

Further, in the present embodiment, the light source control data creating unit 16 creates the light source control data based on the value of the histogram distribution in the section H1, but is not limited thereto. A histogram distribution of the luminance levels of the sections may be used, or a plurality of histogram distributions may be used in combination.

Further, in the present embodiment, the light source control level is also set to L1 (min) in FIG. 3, but is not limited to this, and the light source control level is set to L2 (max) or L1 (min) to L2 ( max). For example, when it is determined based on the histogram distribution that the scene is a bright scene or a scene that is neither bright nor dark, the light source control level is set to L2 (max) or L1 (min) to L2 (max) regardless of the value of APL. May be set in the range.

Further, in the present embodiment, it is determined whether the value of the section H1 is smaller or larger than the threshold value HTL, and the light source control level is controlled in two different modes according to the determination result. The present invention is not limited to this. For example, another threshold value other than the threshold value HTL may be added to increase the number of condition determination modes, and the light source control level condition setting may be set to a plurality of modes according to the determination result.

Although the case where the light source is dynamically controlled has been described as the fourth embodiment, the control method of the light source described in the fourth embodiment can be applied to the control of the aperture and the control of the light control element. Hereinafter, the configuration of the video display device when the light source control method according to the present embodiment is applied to the control of the aperture and the control of the light control element will be briefly described.

FIG. 23 is a block diagram showing a configuration of a video display device when the light source control method according to the fourth embodiment is applied to aperture control. In FIG. 23, the video display device includes an APL detection unit 2, a histogram creation unit 15, an aperture control data creation unit 25, an aperture drive circuit 20, a light source drive circuit 5, a light source 6, an optical system 17, The display device includes a display element 8, a video signal processing circuit 9, a display element driving unit 10, a microcomputer 11, and a timer 12. The optical system 17 includes a stop 18. 23, the same components as those in FIG. 7 or FIG. 21 are denoted by the same reference numerals. The aperture control data creation unit 25 creates aperture control data based on the APL detection result and the histogram creation result, similarly to the light source control data creation unit 16 shown in FIG. As a result, even when only a part of the dark scene has a particularly bright part and the APL detection result cannot determine that the scene is a dark scene, the scene is determined to be a dark scene. Thus, the floating of black can be prevented.

FIG. 24 is a block diagram illustrating a configuration of a video display device in a case where the light source control method according to the fourth embodiment is applied to control of a light control element. 24, the video display device includes an APL detecting unit 2, a histogram creating unit 15, a dimming element control data creating unit 26, a dimming element driving circuit 23, a light source driving circuit 5, a light source 6, The optical device includes an optical element 21, an optical system 7, a display element 8, a video signal processing circuit 9, a display element driving unit 10, a microcomputer 11, and a timer 12. 24, the same components as those in FIG. 10 or FIG. 21 are denoted by the same reference numerals. The light control element control data creation unit 26 creates light control element control data based on the APL detection result and the histogram creation result, similarly to the light source control data creation unit 16 illustrated in FIG. As a result, even when only a part of the dark scene has a particularly bright part and the APL detection result cannot determine that the scene is a dark scene, the scene is determined to be a dark scene. Thus, the floating of black can be prevented.

In the above, the configuration of each video display device when the control method of the light source according to the fourth embodiment is applied to the control of the aperture and the control of the light control element has been briefly described. May be performed simultaneously, the control of the light source and the control of the light control element may be performed simultaneously, or the control of the light source, the control of the aperture, and the control of the light control element may be performed simultaneously. Hereinafter, the configuration of the video display device in each of these cases will be briefly described.

FIG. 25 is a block diagram illustrating a configuration of a video display device in a case where the light source control method according to the fourth embodiment is applied to light source and aperture control. In FIG. 25, the video display device includes an APL detection unit 2, a histogram creation unit 15, an aperture control data creation unit 25, an aperture drive circuit 20, a light source control data creation unit 16, an LPF 4, and a light source drive circuit 5. , A light source 6, an optical system 17, a display element 8, a video signal processing circuit 9, a display element driving unit 10, a microcomputer 11, and a timer 12. The optical system 17 includes a stop 18. 25, the same components as those in FIG. 21 or FIG. 23 are denoted by the same reference numerals. As a result, even when only a part of the dark scene has a particularly bright part and the APL detection result cannot determine that the scene is a dark scene, the scene is determined to be a dark scene. Thus, the floating of black can be prevented.

FIG. 26 is a block diagram illustrating a configuration of a video display device in a case where the light source control method according to the fourth embodiment is applied to control of a light source and a light control element. In FIG. 26, the video display device includes an APL detection unit 2, a histogram creation unit 15, a dimming element control data creation unit 26, a dimming element drive circuit 23, a light source control data creation unit 16, an LPF 4, It includes a light source driving circuit 5, a light source 6, a dimming element 21, an optical system 7, a display element 8, a video signal processing circuit 9, a display element driving section 10, a microcomputer 11, and a timer 12. In FIG. 26, the same components as those in FIG. 21 or FIG. 24 are denoted by the same reference numerals. As a result, even when only a part of the dark scene has a particularly bright part and the APL detection result cannot determine that the scene is a dark scene, the scene is determined to be a dark scene. Thus, the floating of black can be prevented.

FIG. 27 is a block diagram showing a configuration of a video display device when the light source control method according to the fourth embodiment is applied to control of a light source, an aperture, and a light control element. In FIG. 27, the video display device includes an APL detection unit 2, a histogram creation unit 15, an aperture control data creation unit 25, an aperture drive circuit 20, a dimming element control data creation unit 26, a dimming element driving circuit 23, a light source control data creating unit 16, an LPF 4, a light source driving circuit 5, a light source 6, a dimming element 21, an optical system 17, a display element 8, a video signal processing circuit 9, and a display element driving circuit. A unit 10, a microcomputer 11, and a timer 12 are provided. The optical system 17 includes a stop 18. In FIG. 27, the same components as those in FIG. 21 or FIG. 23 or FIG. As a result, even when only a part of the dark scene has a particularly bright part and the APL detection result cannot determine that the scene is a dark scene, the scene is determined to be a dark scene. Thus, the floating of black can be prevented.

As described above, by combining the control of the light source with the control of the aperture or the light control element, it is possible to more effectively dynamically adjust the luminance according to the scene of the image, and to increase the brightness in a bright scene. The problem of lack of feeling and the problem of black floating in a dark scene can be further improved, and the feeling of contrast can be enhanced.

FIG. 1 is a block diagram illustrating a configuration of a video display device according to a first embodiment of the present invention. FIG. 4 is a diagram illustrating one method of light source luminance control. FIG. 4 is a diagram illustrating a method of controlling light source luminance in the first embodiment. FIG. 3 is a diagram illustrating a specific example of signal processing according to the first embodiment. FIG. 3 is a diagram illustrating a state of a signal processing operation according to the first embodiment. FIG. 9 is a diagram illustrating a modification of the signal processing according to the first embodiment. FIG. 2 is a block diagram illustrating a configuration example of a video display device when the light source control method according to the first embodiment is applied to aperture control. FIG. 5 is a diagram illustrating a method of controlling the aperture when the method of controlling the light source according to the first embodiment is applied to the control of the aperture. FIG. 4 is a diagram illustrating a specific example of signal processing when the light source control method according to the first embodiment is applied to aperture control. FIG. 2 is a block diagram illustrating a configuration of a video display device when the light source control method according to the first embodiment is applied to control of a light control element. FIG. 4 is a block diagram illustrating another configuration of the video display device when the light source control method according to the first embodiment is applied to control of a light control element. FIG. 4 is a diagram illustrating a method of controlling a light control element when the light source control method according to the first embodiment is applied to control of a light control element. FIG. 4 is a diagram illustrating a specific example of signal processing when the light source control method according to the first embodiment is applied to control of a light control element. It is a block diagram showing the composition of the picture display concerning a 2nd embodiment of the present invention. FIG. 11 is a diagram illustrating a specific example of signal processing according to the second embodiment. FIG. 9 is a diagram illustrating a specific example of signal processing when the light source control method according to the second embodiment is applied to aperture control. FIG. 9 is a diagram illustrating a specific example of signal processing when the light source control method according to the second embodiment is applied to control of a light control element. FIG. 11 is a block diagram illustrating a configuration of a video display device according to a third embodiment of the present invention. FIG. 14 is a diagram illustrating a specific example of signal processing according to the third embodiment. FIG. 14 is a diagram illustrating a modification of the signal processing according to the third embodiment. It is a block diagram showing the composition of the picture display concerning a 4th embodiment of the present invention. FIG. 4 is a diagram for explaining an operation of a histogram creation unit 15; FIG. 14 is a block diagram illustrating a configuration of an image display device when a light source control method according to a fourth embodiment is applied to aperture control. FIG. 14 is a block diagram illustrating a configuration of an image display device when a light source control method according to a fourth embodiment is applied to control of a light control element. FIG. 13 is a block diagram illustrating a configuration of a video display device when a light source control method according to a fourth embodiment is applied to control of a light source and an aperture. FIG. 15 is a block diagram illustrating a configuration of a video display device when a light source control method according to a fourth embodiment is applied to control of a light source and a light control element. FIG. 14 is a block diagram illustrating a configuration of a video display device in a case where a light source control method according to a fourth embodiment is applied to control of a light source, an aperture, and a light control element.

Explanation of reference numerals

1 video signal 2 APL detector 3 light source control data generator 4 LPF
Reference Signs List 5 light source drive circuit 6 light source 7 optical system 8 display element 9 video signal processing circuit 10 display element drive section 11 microcomputer 12 timer 13 light source control data creation section 14 light source control data creation section 15 histogram creation section 16 light source control data creation section 17 optics System 18 Aperture 19 Aperture control data creating unit 20 Aperture drive circuit 21 Dimming element 22 Dimming element control data creating unit 23 Dimming element drive circuit 24 Optical system 25 Aperture control data creating unit 26 Dimming element control data creating unit

Claims (8)

An image display device that displays an image by irradiating light from a light source to a single or a plurality of display elements having a transmissive or reflective light modulation action,
Histogram creating means for dividing the luminance level of the input video signal into a plurality of luminance level sections and detecting a histogram distribution for each of the luminance level sections;
Light quantity control data creating means for creating light quantity control data for controlling the light quantity applied to the display element, based on the histogram distribution for each of the divided sections detected by the histogram creating means,
Light amount control means for controlling the amount of light emitted to the display element based on the light amount control data,
The light amount control data creating unit is configured to, when the histogram distribution for each of the divided sections detected by the histogram creating unit is in a predetermined distribution state, adjust a light amount applied to the display element according to the predetermined distribution state. Fixed at a certain level,
When the histogram distribution for each of the divided sections deviates from the predetermined distribution state, creating light amount control data such that the amount of light applied to the display element continuously increases with an increase in luminance level. A video display device characterized by the following. The light quantity control data creating unit is configured to, when a histogram distribution of at least one brightness level among the plurality of brightness level sections detected by the histogram creating unit is larger or smaller than a predetermined threshold value, display the display element. 2. The image display device according to claim 1, wherein light amount control data is generated such that the light amount applied to the light is fixed at the predetermined level. The light amount control data creating unit, when it is determined that the video scene related to the input video signal is a dark scene based on the histogram distribution detected by the histogram creating unit, the light amount applied to the display element 2. The image display device according to claim 1, wherein the light amount control data is generated so as to be fixed at a predetermined minimum level. The light amount control data creating unit, when it is determined that the video scene related to the input video signal is a bright scene based on the histogram distribution detected by the histogram creating unit, the light amount applied to the display element 2. The image display device according to claim 1, wherein the light amount control data is generated so as to be fixed at a predetermined maximum level. An image display method for displaying an image by irradiating light from a light source to a single or a plurality of display elements having a transmissive or reflective light modulation action,
Dividing the luminance level of the input video signal into a plurality of luminance level sections and detecting a histogram distribution for each of the luminance level sections;
A light quantity control data creating step for creating light quantity control data for controlling the light quantity applied to the display element based on the histogram distribution for each of the divided sections detected by the histogram creating step;
Light amount control step of controlling the amount of light emitted to the display element based on the light amount control data,
The light quantity control data creating step includes, when the histogram distribution for each of the divided sections detected in the histogram creating step is in a predetermined distribution state, the light quantity applied to the display element according to the predetermined distribution state. Fixed at a certain level,
When the histogram distribution for each of the divided sections deviates from the predetermined distribution state, creating light amount control data such that the amount of light applied to the display element continuously increases with an increase in luminance level. Characteristic video display method. The light quantity control data creating step is performed when the histogram distribution of at least one brightness level among the plurality of brightness level sections detected in the histogram creation step is larger or smaller than a predetermined threshold. 6. The image display method according to claim 5, wherein light amount control data is generated such that the light amount applied to the light is fixed at the predetermined level. The light amount control data creating step includes, when it is determined that the video scene related to the input video signal is a dark scene based on the histogram distribution detected in the histogram creating step, the light amount applied to the display element. 6. The image display method according to claim 5, wherein the light amount control data is fixed so as to be fixed at a predetermined minimum level. The light amount control data creating step includes, when it is determined that the video scene related to the input video signal is a bright scene based on the histogram distribution detected in the histogram creating step, the light amount applied to the display element. 6. The image display method according to claim 5, wherein the light amount control data is fixed so as to be fixed at a predetermined maximum level.

Images