CN100470626C - image display device - Google Patents

Abstract

Use the APL detection unit (2) to detect the APL of each unit field period of the input image signal (1), and the light source control data generation unit (3) according to the APL detection result, when the APL is 0% to the specified value A1, generate The light source control signal of the minimum level for stably driving the light source (6), when the APL is the specified value A2~100%, generates the light source control signal of the maximum level capable of stably driving the light source (6), and the APL is the specified value A1 ~A specified value of A2, generate a light source control signal that dynamically changes corresponding to the APL, and drive the light source (6) according to the light source control signal, thereby improving the phenomenon of insufficient contrast and emerging black shadows, and at the same time improving the performance of the light source (6) reliability.

Description

image display device

The application of the present invention is that the international application date is April 19, 2002, the international application number is PCT/JP02/03900, the national application number in China is 02801381.6, and the invention name is "image display device and image display method "A divisional application of the patent application.

technical field

The present invention relates to an image display device and an image display method, in particular to an image display device and an image display method for displaying an image by irradiating light from a light source to a transmissive or reflective display element having a light modulation function.

Background technique

In recent years, as image equipment such as video tape recorders and video disk players and image software have been enriched, the desire for image display devices capable of enjoying powerful images has been increasing.

Conventionally, there are so-called direct-view liquid crystal display devices and projection display devices as image display devices that spatially modulate light emitted from a light source to display images by using a transmissive or reflective display element having a light modulation function. A direct-view liquid crystal display device uses a liquid crystal panel as a display element, and directly uses eyes to see images displayed on the liquid crystal panel. And another kind of projection display device is to use a strong light source to project the image displayed on the liquid crystal panel or other display elements onto the screen to watch the image.

If an image display device adopting a display element having such a light modulation effect is compared with an image display device employing a self-luminous display element such as a CRT, the direct-view liquid crystal display device has, for example, insufficient brightness in a bright scene and Issue with shadows appearing in dark scenes. Therefore, attempts are being made to address these issues.

In a direct-view liquid crystal display device, in order to improve the quality of the displayed image, as a generally used method, the input image signal is adjusted by contrast (adjustment of signal amplification gain) or black level adjustment. Adjustment method. In addition, in addition to these electrical adjustments, there are also devices that divide the luminance level of the light source into several levels, which can be changed. However, the adjustment of the luminance level of the light source is performed manually, and the luminance of the light source remains fixed.

In addition, in the projection type display device, a display device with the same function of adjusting the luminance of the light source has also been put into practical use, but this is different from the direct view type display device, and its main purpose is not so much to improve the quality of the displayed image, but to Rather, it is to reduce the power consumption of the device, adjust the brightness of the image brightness for easy viewing according to the screen size and ambient lighting conditions, and extend the life of the light source. Moreover, the adjustment of the luminance level of the light source is performed manually by the user, as in the direct-view liquid crystal display device, and then the luminance of the light source is in a fixed state.

As mentioned above, compared with self-illuminating display devices such as CRTs, the existing direct-view liquid crystal display devices and projection display devices have insufficient brightness in bright scenes and black shadows in dark scenes. Image quality needs to be improved. However, the light source luminance control method adopted by the conventional direct-view liquid crystal display device and projection display device as described above is a static fixed control method, which cannot respond to dynamic changes of input image signals. Therefore, there is a problem that the display image quality cannot be improved in each scene of the input image signal.

Therefore, as a method of improving the quality of the displayed image, a method of dynamically changing the luminance of the light source according to the scene of the image has been proposed. Such a method is disclosed, for example, in Japanese Patent Application Laid-Open No. 5-127608 and Japanese Patent Laid-Open No. 6-160811.

The method proposed in the Japanese Patent Laid-Open No. 5-127608 is to detect the characteristics of the input image signal according to the maximum value, minimum value and average value of the input image signal, and the level difference between the maximum value and the minimum value is relatively large. When the contrast control is lowered, the signal amplification gain is reduced. When the level difference between the maximum value and the minimum value is small, the contrast control is increased to increase the signal amplification gain. At the same time, the average ratio between the maximum value and the minimum value is preset When the specified value is high, the luminance of the light source is reduced so that the luminance of the display device approaches a certain value.

In addition, the method proposed in JP-A-6-160811 is to detect the maximum value of the input image signal, increase the luminance of the light source when the maximum value is high, and decrease the luminance of the light source when the maximum value is low. , and make the luminance signal amplitude when the maximum value is low be smaller than the luminance signal amplitude when the maximum value is high, so as to increase the relative contrast ratio between the maximum value and the low value.

The technology proposed in Japanese Patent Laid-Open No. 5-127608, as mentioned above, is a technology to dynamically control the luminance of the light source according to the input scene, but there is a problem that, for the purpose of keeping the display luminance constant, the Dark scenes do not improve the appearance of shadows. In addition, since the brightness of the light source is controlled according to the average value of the maximum value and the minimum value of the input image signal, there are input scenes with a local high maximum value or low minimum value, and the characteristics of the input scene cannot be captured. Problem with improper adjustment of light source brightness. Also, since the adjustment of the luminance of the light source is performed discontinuously, there is a problem that the luminance of the screen changes greatly when the luminance of the light source changes, causing discomfort to the viewer.

In addition, the technique proposed in JP-A-6-160811 is also a technique for dynamically controlling the luminance of the light source according to the input image signal as described above, but since the luminance of the light source is controlled according to the maximum value of the input image signal, The problem is that even though the average luminance level (hereinafter referred to as APL) is low, in the case of an input scene where the local maximum value is high, the luminance of the light source is increased, and black shadows appear in the dark part of the image instead. . In addition, discharge light sources such as xenon lamps and high-pressure mercury lamps used in projection display devices have repeated and rapid changes in driving conditions, causing problems such as instability in lighting start-up performance and deterioration of normal lighting performance such as flicker during normal lighting. and lifetime characteristics deteriorate, and the reliability of the lamp decreases.

Contents of the invention

Therefore, the object of the present invention is to improve the problem of display image quality (contrast sensitivity) in an image display device composed of a transmissive or reflective display element having a light modulation function and a light source for irradiating light to the display element. deficiency and floating blackness). In addition, 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 irradiating a display element.

Another object of the present invention is to provide an image display device and method, which can change the luminance of the light source according to the input image signal, so as to realize the image display with a sense of contrast, and on the other hand, can prevent the The discomfort of the display caused by the sharp change of the temperature can be improved, and the life of the light source can be improved.

In order to achieve the above object, the present invention has the following features.

A first aspect of the present invention provides an image display device, which displays images by irradiating light from a light source on a transmissive or reflective display element with a light modulation effect, including:

a histogram generating means for dividing the luminance level of the input image signal into a plurality of luminance level areas, and detecting a histogram distribution of each luminance level area; and

a light quantity control device for controlling the light quantity of the light source,

When the histogram distribution of at least one luminance level region of the plurality of luminance level regions detected by the histogram generation device is greater than a predetermined threshold, the light quantity control device controls the light quantity of the light source, The amount of light impinging on the display element is fixed at a prescribed minimum level.

A second aspect of the present invention provides an image display device, which displays images by irradiating light from a light source on a transmissive or reflective display element with a light modulation effect, including:

a histogram generating means for dividing the luminance level of the input image signal into a plurality of luminance level areas, and detecting a histogram distribution of each luminance level area; and

an aperture disposed between the light source and the display element for controlling the amount of light irradiated on the display element,

When the histogram distribution of at least one of the plurality of luminance level regions detected by the histogram generation device is greater than a predetermined threshold, the aperture is controlled so that the light on the display element The amount of light on is fixed at a specified minimum level.

A third aspect of the present invention provides an image display device, which displays images by irradiating light from a light source on a transmissive or reflective display element with a light modulation effect, including:

a histogram generating means for dividing the luminance level of the input image signal into a plurality of luminance level areas, and detecting a histogram distribution of each luminance level area; and

a dimming element arranged between the light source and the display element for adjusting the amount of light irradiated on the display element,

When the histogram distribution of at least one luminance level region detected by the histogram generation device is greater than a specified threshold, the light adjustment element is controlled so that the light on the The amount of light on the display element is fixed at a specified minimum level.

A fourth aspect of the present invention is the image display device according to the above first aspect, further comprising an aperture provided between the light source and the display element for controlling the amount of light irradiated on the display element ,

When the histogram distribution of at least one luminance level region detected by the histogram generation device is greater than a prescribed threshold, the light source and aperture are controlled so that the light source in the The amount of light on the display element is fixed at a specified minimum level.

A fifth aspect of the present invention is the image display device according to the above first aspect, further comprising a regulator provided between the light source and the display element for controlling the amount of light irradiated on the display element. light element,

When the histogram distribution of at least one luminance level region detected by the histogram generation device is greater than a specified threshold, the light source and the dimming element are controlled so that the illumination in The amount of light on the display element is fixed at a specified minimum level.

A sixth aspect of the present invention is the image display device according to any one of the first to fifth aspects above, wherein the at least one luminance level region among the plurality of luminance level regions is The area closest to the black level.

Description of drawings

Fig. 1 is a block diagram showing the structure of an image display device according to a first embodiment of the present invention.

Figure 2 shows a method of light source brightness control.

Fig. 3 shows the method of controlling the luminance of the light source in the first embodiment.

Fig. 4 shows a specific example of signal processing in the first embodiment.

Fig. 5 shows the signal processing operation of the first embodiment.

Fig. 6 shows a modified example of the signal processing of the first embodiment.

Fig. 7 is a block diagram showing a configuration example of an image display device when the light source control method according to the first embodiment is used for aperture control.

Fig. 8 shows the aperture control method when the light source control method of the first embodiment is used for aperture control.

Fig. 9 shows a specific example of signal processing when the light source control method of the first embodiment is used for aperture control.

Fig. 10 is a block diagram showing the configuration of an image display device when the light source control method according to the first embodiment is used for dimming element control.

Fig. 11 is a block diagram showing another configuration of the image display device when the light source control method according to the first embodiment is used for dimming element control.

Fig. 12 is a diagram showing a method of controlling a light control element when the light source control method of the first embodiment is used for control of a light control element.

Fig. 13 shows a specific example of signal processing when the light source control method according to the first embodiment is used for dimming element control.

Fig. 14 is a block diagram showing the structure of an image display device according to a second embodiment of the present invention.

Fig. 15 shows a specific example of signal processing in the second embodiment.

Fig. 16 shows a specific example of signal processing when the light source control method of the second embodiment is used for aperture control.

Fig. 17 shows a specific example of signal processing when the light source control method according to the second embodiment is used for dimming element control.

Fig. 18 is a block diagram showing the structure of an image display device according to a third embodiment of the present invention.

Fig. 19 shows a specific example of signal processing in the third embodiment.

Fig. 20 shows a modified example of signal processing of the third embodiment.

Fig. 21 is a block diagram showing the structure of an image display device according to a fourth embodiment of the present invention.

FIG. 22 is an explanatory diagram regarding the operation of the histogram generating unit 15. As shown in FIG.

Fig. 23 is a block diagram showing the configuration of an image display device when the light source control method of the fourth embodiment is used for aperture control.

Fig. 24 is a block diagram showing the configuration of an image display device when the light source control method according to the fourth embodiment is used to control the light control element.

Fig. 25 is a block diagram showing the configuration of an image display device when the light source control method according to the fourth embodiment is used for light source and aperture control.

Fig. 26 is a block diagram showing the structure of an image display device when the light source control method according to the fourth embodiment is used to control the light source and the light control element.

Fig. 27 is a block diagram showing the structure of an image display device when the light source control method according to the fourth embodiment is used to control the light source, diaphragm, and dimming element.

Fig. 28 is a block diagram showing the structure of an image display device according to a fifth embodiment of the present invention.

FIG. 29 shows an example of the APL signal output by the APL detection unit 2 and the luminance of the light source 6 changing with time.

FIG. 30 is a block diagram showing the structure of the signal change control unit 32. As shown in FIG.

Fig. 31 is a block diagram showing the configuration of an image display device according to a sixth embodiment of the present invention.

FIG. 32 shows an example of the APL signal output by the APL detection unit 2 and the luminance of the light source 6 changing with time.

FIG. 33 is a block diagram showing the structure of the signal change control unit 33. As shown in FIG.

Fig. 34 is a block diagram showing the structure of an image display device according to a seventh embodiment of the present invention.

FIG. 35 shows an example of the APL signal output by the APL detection unit 2 and the luminance of the light source 6 changing with time.

FIG. 36 is a block diagram showing the configuration of the light source emission luminance state detection unit 35 .

Fig. 37 is an explanatory diagram of a comparative example for explaining the effect of the seventh embodiment of the present invention.

Fig. 38 is a block diagram showing the structure of an image display device according to an eighth embodiment of the present invention.

FIG. 39 shows an example of the APL signal output from the APL detection unit 2, the squelch signal from the system control unit 44, and the luminance of the light source 6 changing with time.

FIG. 40 is a block diagram showing the structure of the signal change control unit 37. As shown in FIG.

Detailed ways

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

1st embodiment

Fig. 1 shows the configuration of an image display device according to a first embodiment of the present invention. The image display device has an APL detection unit 2, a light source control data generation unit 3, an LPF 4, a light source drive circuit 5, a light source 6, an optical system 7, a display element 8, an image signal processing circuit 9, a display element drive unit 10, and a microcomputer. 11 and timer 12. When the image display device is a projection device, the optical system 7 is provided, but it is not provided in the case of a direct view type. Next, the operation of the first embodiment will be described.

The image signal 1 is supplied to an image display device. The image signal 1 is input to the image signal processing circuit 9 and the APL detection unit 2 . The image signal 1 input to the image signal processing circuit 9 is subjected to signal processing necessary for the display device such as contrast control and brightness control, and then input as a drive signal suitable for the light modulation function of the display element 8 through the display element drive unit 10. to display element 8. Since the signal processing in the image signal processing circuit 9 and the display element driving unit 10 is well known, detailed description thereof will be omitted.

The APL detection unit 2 detects the APL for each unit field period based on the luminance signal component of the input image signal 1 , and outputs the detection result to the light source control data generation unit 3 . The light source control data generation unit 3 generates light source control data corresponding to the APL detection result. The generated light source control data is input to the light source driving circuit 5 via the LPF4. The light source driving circuit 5 drives the light source 6 according to the driving conditions corresponding to the light source control data. The light emitted from the light source 6 is focused by the optical system 7 to irradiate 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 detection unit 2 and the light source data generation unit 3 in order to perform time axis control at the time of APL detection and generation of light source control data.

Next, with reference to FIGS. 2 to 4 , the specific processing content of the light source control data generation unit 3 and the role of the LPF 4 will be described.

Taking a discharge lamp used in a projection device as an example, as shown in FIG. 2 , the light source driving power level ranges from L1 (min) to L2 (max), which is a region where the light source is stably turned on. When the level of the driving power of the light source is lower than L1 (min), the light source cannot be turned on stably. Therefore, when changing the driving power of the light source, it is necessary to drive the light source within the power range of the stable lighting region (L1 (min) to L2 (max)). Therefore, the dynamic light source control corresponding to the APL of the input image signal 1 in this embodiment is also performed using the stable lighting area.

In FIG. 2, the input image signal 1 when the power of the light source is linearly changed from L1 (min) to L2 (max) for the variation range (0% to 100%) of the APL of the input image signal 1 is shown by a dotted line as a reference. The relationship between APL and light source control level. In this case, only when the APL of the input video signal 1 is 0%, the light source control level is at the minimum value L1 (min) of the stable lighting area. Therefore, when the APL is, for example, B1 shown in the figure, although it is a dark scene, the light source control level does not drop much, and black shadows cannot be prevented from appearing. Also, only when the APL of the input image signal 1 is 100%, the light source control level is set to the maximum value L2(max)=100% of the stable lighting area. Therefore, when the APL is, for example, B2 shown in the figure, even though it is a bright scene, the control level of the light source is not the maximum, which impairs the sense of brightness of the white peak.

In addition, especially when movie software is used, since movies have relatively many dark scenes on the entire screen, the impact of the appearance of black shadows is also great, and the appearance of black shadows will greatly damage the display quality of the image. Therefore, it is best to minimize the appearance of shadows in dark scenes.

In addition, when people watch movie software, compared with the dark-adapted storage of dark scenes, the brightness level of bright scenes is high, and the contrast ratio is high. Conversely, if the dark level is low in a dark scene compared to the photopic storage of a bright scene, the perceived contrast is high. Improving the sense of contrast is important for improving the display quality of images. As a result, black shadows appear, or the brightness of the peak white in bright scenes is perceived as impaired, resulting in a drop in contrast, which is undesirable.

In this embodiment, light source power control as shown in FIG. 3 is performed in order to further improve the display quality of an image in view of the foregoing. A1 and A2 shown in FIG. 3 are preset APL thresholds. The threshold levels of A1 and A2 are thresholds for distinguishing dark scenes and bright scenes, respectively, and can be obtained from the evaluation of movie software. In the case of using software with many bright scenes other than movie software, the setting of these thresholds may be changed according to the image source.

In FIG. 3, as the first mode (fixed area Low) of light source control, when the APL of the input image signal 1 is smaller than the threshold value A1, the light source control level is kept constant at L1 (min). As the second mode (corresponding variable area), when the APL of the input image signal 1 is threshold value A1 to threshold value A2, the light source control voltage is changed within the range of L1 (min) to L2 (max) according to the change of APL. flat. In the third mode (fixed area High), when the APL of the input image signal 1 is greater than the threshold value A2, the light source control level is kept constant at L2 (max).

In addition, in Fig. 3, it is assumed that the relationship between the APL of the corresponding variable region and the control level of the light source is a linear relationship, but it is not limited thereto, for example, the relationship between the control level of the light source and the driving power of the light source or the relationship between the driving power of the light source and the luminous intensity of the light source When the relationship is nonlinear, a function that inversely corrects the nonlinear characteristics may be used in the corresponding variable region. In addition, it is not limited to the inverse correction of the nonlinear characteristic, but may be a function of any nonlinear characteristic.

The relationship between the dynamic change of the APL of the input image signal 1 and the dynamic control of the light source control level will be described in detail below with reference to FIG. 4 . In FIG. 4, the upper figure shows a specific example of the dynamic change of the input APL input to the light source control data generation unit 3, and the lower figure shows the dynamic control of the light source control level corresponding to the dynamic change of the input APL shown in the upper figure. . Particularly in the figure below, the solid line represents the output signal from the light source control data generation unit 3, and the dotted line represents the output signal from the LPF4. Tn is the unit field time for detecting APL. As shown in Figure 4, in this embodiment, control is performed according to the control method shown in Figure 3 above, so that for the dynamic change of APL, when the APL is in the corresponding variable range (A1-A2), the light source control also dynamically tracks , but when the APL is in the fixed region Low and the fixed region High, the control levels of the light source are respectively set to L1 (min) and L2 (max) to keep constant.

The role of LPF4 will be described below. As mentioned above, the dynamic change of the solid line in the lower figure of FIG. 4 represents the output signal from the light source control data generation unit 3, that is, the input signal to the LPF4. According to the preset time constant of the LPF4, the output signal of the LPF4 is as shown in the figure 4 changes as shown in the lower figure, and the light source 6 is driven by the light source driving circuit 5. In the case of a discharge lamp, a sudden change in driving power will affect the state of the discharge arc, causing deterioration of the lamp electrodes and impairing the reliability of the lamp. Therefore, in this embodiment, the LPF 4 is used to have a time constant, and the driving power is changed so that the reliability of the lamp does not decrease in a transient state when the driving power is changed. For LPF4, its specific circuit is omitted because it is well known, and it can be an analog LPF or a digital LPF. When a digital LPF is used as the LPF 4 , it only needs to be converted into an analog signal in the processing of the light source driving circuit 5 . In addition, instead of the LPF 4 , other means that provide a delay effect on the output signal from the light source control data generating unit 3 may be used.

If the dynamic control illustrated in Fig. 4 is expressed in the same form as Fig. 3, as shown in Fig. 5, when the APL is in the corresponding variable range (A1-A2), the control level of the light source is as shown by the arrow in the figure , corresponding to the change of the APL of the input image signal 1, it is dynamically shifted in the stable lighting area.

As mentioned above, according to the first embodiment, by dynamically driving the light source, the luminance can be dynamically adjusted according to the image scene, the problems of insufficient brightness in bright scenes and black shadows in dark scenes can be improved, and the contrast can be improved. In addition, in a dark scene, that is, when the APL of the input image signal is less than a predetermined threshold, since the light source control level is set to the minimum value of the stable lighting area, the problem of black shadows appearing in a dark scene can be further improved. In addition, in a bright scene That is, when the APL of the input image signal is greater than the predetermined threshold, since the light source control level is set to the maximum value of the stable lighting area, the problem of insufficient brightness perception in bright scenes can be further improved, and as a result, the contrast perception can be further improved.

In addition, in this embodiment, the control is performed in such a way that when the APL is in the fixed range Low and the fixed range High, the light source control levels are kept constant at L1 (min) and L2 (max), respectively, but it does not It is necessary to keep the driving level of the light source constant at the minimum level or maximum level. Even at their similar levels, of course, the above-mentioned problem of black shadows appearing in dark scenes and the lack of brightness in bright scenes can be further improved. question. However, by driving with a fixed minimum level or maximum level as in this embodiment, these effects can be obtained to the maximum, and at the same time, since the light source drive level does not change in dark scenes and bright scenes, it is also possible to improve the reliability of the light source. problem, so it is ideal.

In addition, in this embodiment, as shown in FIG. 4, the control level of the light source is controlled based on the APL of each unit field time Tn, but it is also possible to calculate the average value of the APLs of a plurality of unit field times Tn, and use This average value is used to control the light source control level instead of the above method. For example, take Tn (unit field time) in the upper figure of FIG. 4 as T2K=(Tn-K+Tn-K+1+...+Tn+...+Tn+K-1+Tn+K)/(2K+1) , replaced by the average value of the detection results of APL of multiple unit fields. In this way, the dynamic change period and change amount of the arrows shown in FIG. 5 are reduced. That is, the change cycle of the light source control level in the corresponding variable region of the APL becomes larger, and the change amount becomes smaller. Therefore, it is possible to further improve the reduction in lamp reliability. This effect will be described in more detail below with reference to FIG. 6 . FIG. 6 shows the case of K=1, and the thick dotted line in the upper figure represents the average value of the detection results of APL in every 3 unit fields. The light source control level is controlled according to this average value as shown in the lower graph of FIG. 6 . Therefore, by controlling the light source based on the average value of the APLs of a plurality of unit field times, compared with the case shown in FIG. 4 , it is possible to reduce fluctuations in the control level of the light source and further improve the reduction in the reliability of the light source.

Although not shown in the figure, an LPF may be inserted on the output side of the APL detection means 2 as a configuration capable of providing an effect similar to the above-described control based on the APL average value of a plurality of unit field times. However, in the case of controlling based on the APL average value, since the number of target fields can be accurately specified as an integer value K, and the value of K can also be appropriately changed according to the situation by using program settings, for example, in Fig. In the corresponding variable area shown in 5, in the case of increasing or decreasing the luminance of the light source, a control method such as changing its changing speed can also be adopted.

In addition, as the first embodiment, the case where the light source is dynamically controlled has been described, but the present invention can also be similarly applied to other cases where the amount of light irradiated to the display element can be finally controlled. Next, the structure and operation of an image display device when the light source control method of this embodiment is used for aperture control and light control element control will be described.

Fig. 7 is a block diagram showing the configuration of an image display device when the light source control method of the first embodiment is used for aperture control. In FIG. 7, the image display device has an APL detection unit 2, an aperture control data generation 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 signal processing circuit 9, A display element driving unit 10 , a microcomputer 11 and a timer 12 . The optical system 17 includes an aperture 18 . In addition, in FIG. 7, the same reference numerals are assigned to the same configuration as in FIG. 1, and description thereof will be omitted. Next, the operation of the image display device will be described.

The aperture control data generation unit 19 generates aperture control data corresponding to the APL detection result. The generated aperture control data is input to the aperture drive circuit 20 . The aperture driving circuit 20 dynamically drives the aperture 18 according to the driving condition corresponding to the aperture control data, and changes the amount of light shielded by the aperture 18 . The light emitted from the light source 6 is focused by the optical system 17 to irradiate the display element 8 as illumination light corresponding to the display range of the display element 8 . At this time, the amount of light irradiated on the irradiating display element 8 and the amount of light shielded by the diaphragm 18 are adjusted.

Next, specific processing contents of the aperture control data generation unit 19 will be described with reference to FIGS. 8 and 9 .

A1a and A2a shown in FIG. 8 are preset APL thresholds. The threshold levels of A1a and A2a are thresholds for distinguishing dark scenes and bright scenes, respectively, and can be obtained from the evaluation of movie software. In the case of using software with many bright scenes other than movie software, the setting of these thresholds may be changed according to the image source.

In FIG. 8, as the first mode (fixed area Low) of the light quantity control, when the APL of the input image signal 1 is smaller than the threshold value A1a, the light quantity control level is kept constant at L1a (min). As the second mode (corresponding variable area), when the APL of the input video signal 1 is threshold value A1a to threshold value A2a, the light quantity control level is changed within the range of L1a (min) to L2a (max) as the APL changes. . In the third mode (fixed region High), when the APL of the input video signal 1 is greater than the threshold value A2a, the light source control level is kept constant at L2a(max).

In addition, in FIG. 8, the relationship between the APL (A1a-A2a) corresponding to the variable region and the light source control level is assumed to be a linear relationship, but it is not limited thereto, and may be any nonlinear characteristic function.

Referring to FIG. 9, the relationship between the dynamic change of the APL of the input video signal 1 and the dynamic control of the light quantity control level will be described in detail. In FIG. 9, the upper diagram shows a specific example of the dynamic change of the input APL input to the aperture control data generating unit 19, and the lower diagram shows the dynamic control of the light quantity control level corresponding to the dynamic change of the input APL shown in the upper diagram. . Tn is the unit field time for detecting APL. According to the aforementioned control method shown in Figure 8, control is carried out so that for the dynamic change of APL, when the APL is in the corresponding variable region (A1a-A2a), the light quantity control is also dynamically tracked, but when the APL is in the fixed region Low and the fixed region High , the light quantity control levels are kept constant at L1a (min) and L2a (max), respectively.

In addition, the output signal from the aperture control data generation unit 19 shown in the lower diagram of FIG. 9 is not limited to the case shown by the solid line, and may be as shown by the dotted line in consideration of the responsiveness and reliability of the aperture drive structure. , so that it has the characteristic of time delay for the change of APL.

As described above, when the APL is in the corresponding variable region (A1a to A2a), the light quantity control level is dynamically shifted in the corresponding variable region according to the APL change of the input image signal 1 as indicated by the arrow shown in FIG. .

As mentioned above, adopting the image display device shown in FIG. 7, by dynamically driving the aperture, the amount of light can be dynamically adjusted according to the image scene, and the problems of insufficient brightness in bright scenes and black shadows in dark scenes can be improved. Improve the sense of contrast. In addition, in a dark scene, that is, when the APL of the input image signal is less than a predetermined threshold, since the light quantity control level is set to the minimum value of the aperture control area, the problem of black shadows appearing in a dark scene can be further improved. In addition, in a bright scene That is, when the APL of the input image signal is greater than the predetermined threshold, since the light quantity control level is set to the maximum value of the aperture control area, the problem of insufficient brightness perception in bright scenes can be further improved, and the contrast perception can be further improved as a result.

In addition, when controlling the light source, due to the stable lighting of the light source, the minimum value L1 of light source control is relatively large (about 1/3 to 1/2 of the maximum value L2), and the amount of light cannot be made small enough in dark scenes, while controlling the aperture When , the minimum value L1a of the light quantity control can be made sufficiently small (it can also be 0 in principle). As a result, the black level can be kept low enough in dark scenes, the appearance of black shadows can be better improved, and the contrast ratio relative to bright scenes can be increased at the same time.

In addition, when controlling the light source, due to the life reliability of the discharge light source used in the projection device, if the power of the light source changes quickly, or the number of times of change is large, there will be a problem that the life time will be damaged, but when controlling the aperture , although it also depends on the opening and closing structure of the aperture, the influence of the speed of change and the number of changes of the aperture driving condition on the reliability of the aperture driving structure is smaller than that of controlling the light source. Therefore, for example, for the change of APL, it can also be positioned by field/frame to track the driving condition of the aperture, which can greatly improve the tracking performance when the image scene brightness changes sharply, and can obtain a good sense of contrast according to the scene brightness change.

In addition, discharge light sources used in projection devices are roughly divided into xenon lamp light sources and high-pressure mercury lamp light sources. Compared with xenon lamp light sources, high-pressure mercury lamp light sources are difficult to ensure reliability in the above points. The spectrum also has a tendency to change. Therefore, when using a high-pressure mercury lamp light source, aperture control is particularly effective.

In addition, it is also possible to simultaneously perform two types of control, the light source control and the iris control. In this case, since the contrast improvement effect is the product of the contrast improvement effect by light source control and the contrast improvement effect by iris control, it is more effective for contrast improvement. In this case, by setting the changing speed of the aperture faster than the changing speed of the light source, it is possible to eliminate the bad influence on the lifetime reliability of the light source, and to improve the tracking performance of the light quantity to the change of the image scene.

Fig. 10 is a block diagram showing the configuration of an image display device when the light source control method according to the first embodiment is used for dimming element control. In FIG. 10, the image display device has an APL detection unit 2, a dimming element control data generating unit 22, a dimming element driving circuit 23, a light source driving circuit 5, a light source 6, a dimming element 21, an optical system 7, and a display element. 8. Image signal processing circuit 9 , display element drive unit 10 , microcomputer 11 and timer 12 . In addition, 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 addition, in the structure shown in FIG. 10, the light adjustment element 21 is provided in the front stage of the optical system 7, However, As shown in FIG. 11, the light adjustment element 21 may be provided in the inside of the optical system 24. Next, the operation of the image display device shown in Fig. 10 will be described.

The dimming element control data generating unit 22 generates dimming element control data corresponding to the APL detection result. The generated 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 according to the driving condition corresponding to the dimming element control data, and changes the transmittance of the dimming element 21 . The light emitted by the light source 6 passes through the dimming element 21 , is focused by the optical system 7 , and irradiates the display element 8 as irradiating light corresponding to the display range of the display element 8 . At this time, the amount of light irradiating the display element 8 is adjusted according to the transmittance of the modulator element 21 .

The specific processing content of the dimming element control data generation unit 22 will be described below with reference to FIG. 12 and FIG. 13 .

A1b and A2b shown in FIG. 12 are preset APL thresholds. The threshold levels of A1b and A2b are thresholds for distinguishing dark scenes and bright scenes, respectively, and can be obtained from the evaluation of movie software. In the case of using software with many bright scenes other than movie software, the setting of these thresholds may be changed according to the image source.

In FIG. 12, as the first mode (fixed area Low) of the light quantity control, when the APL of the input image signal 1 is smaller than the threshold value A1b, the light quantity control level is kept constant at L1a (min). As the second mode (responsive variable area), when the APL of the input image signal 1 is threshold value A1b to threshold value A2b, the light quantity control voltage is changed within the range of L1b (min) to L2b (max) according to the change of APL. flat. In the third mode (fixed region High), when the APL of the input video signal 1 is greater than the threshold value A2b, the light source control level is kept constant at L2b(max).

In addition, in FIG. 12 , it is assumed that the relationship between the correspondingly variable APL (A1b-A2b) and the light source control level is a linear relationship, but it is not limited thereto, and may be any nonlinear function.

Next, the relationship between the dynamic change of the APL of the input video signal 1 and the dynamic control of the light quantity control level will be specifically described with reference to FIG. 13 . In FIG. 13, the upper figure shows a specific example of the dynamic change of the input APL input to the dimming element control data generation unit 22, and the lower figure shows the dynamic control of the light quantity control level corresponding to the dynamic change of the input APL shown in the upper figure. . Tn is the unit field time for detecting APL. Control according to the control method shown in Figure 12 above, so that for the dynamic change of APL, when the APL is in the corresponding variable area (A1b-A2b), the light quantity control is also dynamically tracked, but when the APL is in the fixed area Low and the fixed area High , the light quantity control levels are kept constant at L1b (min) and L2b (max), respectively.

In addition, the output signal of the dimming element control data generation unit 22 shown in the lower diagram of FIG. 13 is not limited to the case shown by the solid line, and may be as shown by the dashed line, taking into account the responsiveness and reliability of the dimming element. So that it has a time delay characteristic for the change of APL.

As described above, when the APL is in the corresponding variable region (A1b-A2b), the light control level dynamically shifts in the corresponding variable region according to the APL change of the input image signal 1 as indicated by the arrow shown in FIG.

As mentioned above, if the image display device shown in FIG. 10 or FIG. 11 is used, the light intensity can be dynamically adjusted according to the image scene by dynamically driving the dimming element, which can improve the lack of brightness in bright scenes and the black shadow in dark scenes. Emerging issues can improve the sense of contrast. In addition, in a dark scene, that is, when the APL of the input image signal is smaller than a predetermined threshold, since the light quantity control level is set to the minimum value of the aperture control area, the problem of black shadows appearing in a dark scene can be further improved. In addition, In a bright scene, that is, when the APL of the input image signal is greater than or greater than a predetermined threshold, since the light quantity control level is set to the maximum value of the dimming control area, the problem of insufficient brightness in a bright scene can be further improved, and as a result, Further enhance the sense of contrast.

In addition, when controlling the light adjusting element, generally, the same effect as that in the case of controlling the aperture described above can be obtained. In addition, compared with the case of controlling the light source, the dimming element drive circuit can also be realized with a relatively simple circuit and low voltage when controlling the dimming element, so it is easier to implement. In addition, compared with the case of controlling the aperture, in the case of controlling the dimming element, there is a degree of freedom of arrangement from the light source to the display element, and for the driving of the dimming element, no movable structure is required, and only the driving circuit is used for electrical control. Control, therefore, can be realized with a relatively simple structure, so it is easier to realize.

In addition, it is also possible to perform both control of the light source control and the control of the dimmer at the same time, and in this case, the same effect as when the two controls of the light source control and the aperture control are performed simultaneously can be obtained. Furthermore, it is also possible to simultaneously perform light source control, aperture control, and dimming element control. In this case, since the contrast improvement effect is the product of the contrast improvement effect by light source control, the contrast improvement effect by iris control, and the contrast improvement effect by dimmer control, it is more effective for contrast improvement.

Second Embodiment

Fig. 14 shows the configuration of an image display device according to a second embodiment of the present invention. The image display device has an APL detection unit 2, a light source control data generation unit 13, an LPF 4, a light source drive circuit 5, a light source 6, an optical system 7, a display element 8, an image signal processing circuit 9, a display element drive unit 10, and a microcomputer. 11 and timer 12. In addition, the difference between the present embodiment and the first embodiment is only the operation of the light source control data generation unit 13 . Therefore, the same reference numerals are attached to the other same configurations, and explanations thereof are omitted.

Next, the operation of the light source control data generation unit 13 will be described with reference to FIG. 15 . In addition to the processing of the light source control data generation unit 3 in the first embodiment, the light source control data generation unit 13 adds processing for alleviating the dynamic tracking characteristic of the light source level control to the APL change. In this way, the state transition frequency of the driving power condition of the lamp is reduced, and the situation of lamp reliability degradation is further improved. A specific description will be given below with reference to FIG. 15 .

FIG. 15 shows the relationship between the dynamic change of the APL of the input image signal 1 and the dynamic control of the light source control level. In FIG. 15 , the upper figure shows a specific example of the dynamic change of the input APL input to the light source control data generation unit 13, and the lower figure shows the dynamic control of the light source control level corresponding to the dynamic change of the input APL shown in the upper figure. In particular, in the figure below, the solid line represents the output signal from the light source control data generation unit 13, and the dotted line represents the output signal from the LPF4. Tn is the unit field time for detecting APL. As shown in Figure 15, in this embodiment, the same as the first embodiment, the control is performed according to the control method shown in Figure 3 above, so that the dynamic change of the APL is in the corresponding variable range (A1-A2) , the light source control also performs dynamic tracking, but when the APL is in the fixed area Low and the fixed area High, the light source control levels are respectively set to L1 (min) and L2 (max) to keep constant.

However, in this embodiment, it is judged whether the change in the input APL is lower than the predetermined judgment threshold APmin level, and when the change in APL is smaller than APmin, the above-mentioned normal control is given priority, and the light source control level is not changed. More specifically, in the upper graph of FIG. 15 , the change level of APL from time t1 to t2 is smaller than the determination threshold APmin. Therefore, as shown in the lower part 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 tracked to a slight change in APL. This is because, if the light source control level is tracked for every slight change in APL, the disadvantage of impairing the reliability of the light source is greater than the advantage of improving the contrast, so it is not preferable.

As described above, according to the second embodiment, in addition to the effect of the first embodiment, the driving conditions of the light source are not changed when the change in APL is small, and the driving conditions of a moment ago are kept, so the difference in the driving conditions of the light source can be reduced. Dynamic transfer frequency. As a result, the problems of deterioration in stable lighting performance and lifetime characteristics of the light source can be improved, and the reliability of the light source can be improved.

In addition, the control method of the second embodiment can also be applied to the control of the diaphragm and the light control element. Next, the cases where the control method of the second embodiment is applied to the diaphragm control and the light control element control will be described respectively.

Fig. 16 shows the relationship between the dynamic change of APL of the input image signal 1 and the dynamic control of the iris control level when the control method of the second embodiment is used for the iris control. In this case, when the change in APL is smaller than the predetermined determination threshold APmin, the light quantity control level is not changed. In this way, it is possible to prevent the reliability of the diaphragm driving mechanism from being lowered due to repeated excessive minute operations of the diaphragm driving mechanism.

Fig. 17 shows the relationship between the dynamic change of APL of the input video signal 1 and the dynamic control of the control level of the light adjustment element when the control method of the second embodiment is used for the control of the light adjustment element. In this case, when the change in APL is smaller than the predetermined determination threshold APmin, the light quantity control level is not changed. In this way, it is possible to prevent the reliability of the dimming element from being lowered due to repeated excessive fine dimming operations of the dimming element.

3rd embodiment

Fig. 18 shows the structure of an image display device according to a third embodiment of the present invention. The image display device has an APL detection unit 2, a light source control data generation unit 14, an LPF 4, a light source drive circuit 5, a light source 6, an optical system 7, a display element 8, an image signal processing circuit 9, a display element drive unit 10, and a microcomputer. 11 and timer 12. In addition, the difference between the present embodiment and the first embodiment is only the operation of the light source control data generation unit 14 . Therefore, the same reference numerals are attached to the other same configurations, and explanations thereof are omitted.

Next, the operation of the light source control data generation unit 14 will be described with reference to FIG. 19 . In addition to the processing of the light source control data generation unit 3 in the first embodiment, the light source control data generation unit 14 adds processing for easing the dynamic tracking characteristic of the light source level control to the APL change. In this way, the state transition frequency of the driving power condition of the lamp is reduced, and the situation of lamp reliability degradation is further improved. A specific description will be given below with reference to FIG. 19 .

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 figure shows a specific example of the dynamic change of the input APL input to the light source control data generation unit 14, and the lower figure shows the dynamic control of the light source control level corresponding to the dynamic change of the input APL shown in the upper figure. In particular, in the figure below, the solid line represents the output signal from the light source control data generation unit 14, and the dotted line represents the output signal from the LPF4. Tn is the unit field time for detecting APL. As shown in Fig. 19, in this embodiment, the same as the first embodiment, the control is performed according to the control method shown in Fig. 3 above, so that the APL is in the corresponding variable range (A1-A2) for the dynamic change of the APL. , the light source control is also dynamically tracked, but when the APL is in the fixed area Low and the fixed area High, the light source control levels are respectively set to L1 (min) and L2 (max) to keep constant.

However, in this embodiment, it is judged whether the light source drive level has shifted to L1 (min) or L2 (max), and when it shifts to L1 (min) or L2 (max), priority is given to the above-mentioned normal control, and within a predetermined period maintain this light source drive level.

Specifically, in the upper diagram of FIG. 19, the APL at time t10 is smaller than the threshold A1, the light source control level is shown in the lower diagram of FIG. 19, and the state shifts to the level of L1 (min). Once the light source driving condition shifts to L1(min), the light source control data generation unit 14 maintains the output in the state of L1(min) for a predetermined period T1 irrespective of the change in APL. Once the period T1 ends at time t12, normal processing corresponding to the change in APL is performed as in the first embodiment.

At the same time, the APL at time t20 is greater than the threshold A2, and the state of the light source control level shifts to the level of L2(max). Once the light source driving condition shifts to L2(max), the light source control data generation unit 14 maintains the output in the state of L2(max) for a predetermined period T2 irrespective of the change in APL. When the period T2 ends at time t22, normal processing corresponding to the change in APL is performed as in the first embodiment.

In this embodiment, as described above, once the light source drive level shifts to L1 (min) or L2 (max), the light source control level is not tracked to the change in APL for a predetermined period. This has the effect of reducing the frequency of dynamic transition of the driving conditions of the light source, which can improve the problems of the stable lighting performance degradation of the light source and the reduction of life characteristics, and improve the reliability of the light source. Also, maintaining the output especially when the light source control level transitions to L1(min) has additional advantages. For example, if the APL frequently changes before and after A1, unless the light source control level is maintained as in the present embodiment, the change in the luminance of the light source is likely to be felt because of a relatively dark scene. This is because human vision is more sensitive to brightness changes in dark scenes than to brightness changes in bright scenes, and has high sensitivity to brightness changes. Therefore, preventing frequent luminance changes of the APL before and after A1 is also effective for improving the quality of displayed images.

As described above, according to the third embodiment, in addition to the effect of the first embodiment, once the light source driving level shifts to L1 (min) or L2 (max), the light source driving condition is kept for a while without changing The previous driving conditions can therefore reduce the frequency of dynamic transition of the driving conditions of the light source. As a result, the problems of deterioration of stable lighting performance of the light source and reduction in lifetime characteristics can be improved, and the reliability of the light source can be improved. In addition, the display image quality of images can be improved.

In addition, in this embodiment, the control level of the light source is maintained for a specified period after the input APL shifts below A1 or above A2, but it is not limited to this, for example, it can be from when the actual light source power reaches the minimum or maximum The light source control level may be kept constant for a predetermined period, or the light source control may be maintained for a predetermined period from other times. Next, this modified example will be described with reference to FIG. 20 .

In this modified example, the light source control data generation unit responds to changes in the input APL, as shown in the lower diagram of FIG. 20 , and performs control using digital processing operations, so that the variable characteristics of the light source control level have a time delay. Specifically, in the upper diagram of FIG. 20, the APL at time t10 is smaller than the threshold value A1, and the light source control level utilizes the time delay effect of the light source control data generation unit. As shown in the lower diagram of FIG. 20 at time t11, The state transitions to L1(min) level. Once the light source driving condition shifts to L1(min), the output remains constant in the state of L1(min) for a predetermined period T1' regardless of the change in APL. When the period T1' ends at time t12, normal data corresponding to the change in APL is performed as in the first embodiment.

Similarly, the APL at time t20 is greater than threshold A2, and the light source control level is shifted to L2 (max) level at time t21 by utilizing the temporal delay effect of the light source control data generation unit. Once the light source driving condition shifts to L2(max), the output remains constant in the state of L2(max) for a predetermined period T2' irrespective of the change in APL. When the period T2' ends at time t22, normal processing corresponding to the change in APL is performed as in the first embodiment.

In addition, the control method of the third embodiment can also be applied to the control of the diaphragm and the light control element. For example, when the control method of this embodiment is adopted for the dynamic control of the aperture shown in FIG. 8, the light quantity control levels are maintained at L1a (min) for a predetermined period from when the input APL shifts below A1a or above A2a. or L2a(max). In this way, the frequency of dynamic transition of the diaphragm driving conditions can be reduced, and as a result, the reliability of the diaphragm driving structure can be prevented from being lowered. In addition, for example, when the control method of this embodiment is adopted for the dynamic control of the dimming element shown in FIG. 12, the light quantity control levels are maintained at L1b ( min) or L2b(max). In this way, the frequency of dynamic transition of the driving conditions of the dimming element can be reduced, and as a result, the reliability of the dimming element can be prevented from being lowered.

Fourth Embodiment

Fig. 21 shows the structure of an image display device according to a fourth embodiment of the present invention. The image display device has an APL detection unit 2, a histogram generation unit 15, a light source control data generation unit 16, an LPF4, a light source driving circuit 5, a light source 6, an optical system 7, a display element 8, an image signal processing circuit 9, and a display element A drive unit 10 , a microcomputer 11 and a timer 12 . In addition, the difference between the present embodiment and the first embodiment is only the operations of additionally having the histogram generating unit 15 and the light source control data generating unit 16 . Therefore, the same reference numerals are attached to the other same configurations, and explanations thereof are omitted.

In FIG. 21 , image signal 1 is input to image signal processing circuit 9 , histogram generation unit 15 and APL detection unit 2 . The histogram generation unit 15 detects a histogram for each segment that divides the input image signal level into an arbitrary number of luminance level areas based on the luminance signal component of the input image signal 1 in each unit field period. distributed. The detection result is input to the light source control data generation unit 16 . The light source control data generation unit 16 generates light source control data based on the APL detection result and the histogram generation result.

Next, referring to FIG. 22 , the specific operation of the histogram generating unit 15 will be described. In the histogram generating unit 15, the signal level from 0% to 100% is divided in advance into several luminance levels (in the figure, four areas H1 to H4), and the input is detected for each unit field. The histogram distribution of the image signal 1 in each of the above partitions. The histogram generation result is input to the light source control data generation unit 16 .

In the light source control data generating unit 16, the value of the H1 area closest to the black level among the divided areas is compared with a predetermined threshold value HTL. When the result of the comparison is that the value of the H1 area is smaller than the HTL, the light source control data generating unit 16 is the same as the first embodiment, and controls according to the control method shown in the aforementioned FIG. When changing the area (A1~A2), the light source control also dynamically tracks, but when the APL is in the fixed area Low and the fixed area High, the light source control levels are respectively set to L1 (min) and L2 (max) to keep constant.

In addition, when the value of the H1 area is greater than HTL, regardless of the APL, it is determined that it is a dark scene, and the light source control data generation unit 16 sets the light source drive control level to L1 prior to the normal control similar to the above-mentioned first embodiment. (min), to improve the appearance of dark shadows in the displayed image. In the case where only a part of a dark scene has a particularly bright part, the APL becomes large due to the influence of the particularly bright part, and therefore it cannot be determined as a dark scene based on the APL. However, as in the present embodiment, a dark scene is judged based on the histogram distribution, and thus even a dark scene can be judged as a dark scene even if there is only a part of a particularly bright part in the dark scene.

In addition, in this embodiment, the number of partitions of the histogram distribution is set to be four, but it is not limited thereto, and may be any number of partitions. In addition, the divided range (width) of each divided luminance level is set to be 25% wide, but it is not limited to this, and may be any divided range, and the range size may be different for each divided area.

In addition, in this embodiment, the light source control data generation unit 16 generates the light source control data based on the histogram distribution value of the H1 area, but it is not limited to this, and the luminance level of other divided areas can be used according to the target scene control. A flat histogram distribution, or a combination of several histogram distributions.

In addition, in this embodiment, the light source control level is also set to L1 (min) in FIG. min) to L2(max). For example, when judging from the histogram distribution as a bright scene or an obscure scene, the light source control level may be set to L2 (max) or L1 (min) to L2 (max) regardless of each APL value. In the range.

In addition, in this embodiment, it is determined whether the value of the H1 area is greater than or less than the threshold value HTL, and the control of the light source control level is performed in two different modes according to the determination result, but it is not limited to this, for example, the threshold value HTL can also be In addition, another threshold value is added, and a condition judgment mode is added, and according to the judgment result, the conditions for taking the light source control level are set in multiple modes.

In addition, the fourth embodiment dynamically describes the case of dynamically controlling the light source, but the light source control method described in the fourth embodiment can also be used for the control of the diaphragm and the control of the dimming element. The structure of the image display device when the light source control method of this embodiment is used for the control of the diaphragm and the control of the dimming element will be briefly described below.

Fig. 23 is a block diagram showing the configuration of an image display device in which the light source control method according to the fourth embodiment is used for controlling the aperture. In FIG. 23, the image display device has an APL detecting unit 2, a histogram generating unit 15, an aperture control data generating unit 25, an aperture driving circuit 20, a light source driving circuit 5, a light source 6, an optical system 17, a display element 8, and a graph. Like a signal processing circuit 9 , a display element driving unit 10 , a microcomputer 11 and a timer 12 . The optical system 17 includes an aperture 18 . In addition, in FIG. 23 , the same reference numerals are assigned to the same configurations as those in FIG. 7 or FIG. 21 . Like the light source control data generating unit 16 shown in FIG. 21 , the aperture control data generation unit 25 generates aperture control data based on the APL detection result and the histogram generation result. In this way, even in the case where only a part of the dark scene has a particularly bright part, it can be judged as a dark scene even if it cannot be judged as a dark scene based on the APL detection result, and black shadows can be prevented from appearing.

Fig. 24 is a block diagram showing the configuration of an image display device in which the light source control method according to the fourth embodiment is used to control the light control element. In FIG. 24, the image display device has an APL detection unit 2, a histogram generating unit 15, a dimming element control data generating unit 26, a dimming element driving circuit 23, a light source driving circuit 5, a light source 6, dimming and 21, Optical system 7 , display element 8 , image signal processing circuit 9 , display element drive unit 10 , microcomputer 11 and timer 12 . In addition, in FIG. 24 , the same reference numerals are assigned to the same configurations as those in FIG. 10 or 21 . Like the light source control data generating unit 16 shown in FIG. 21 , the dimming element control data generation unit 26 generates dimming element control data based on the APL detection result and the histogram generation result. In this way, even in the case where only a part of the dark scene has a particularly bright part, it can be judged as a dark scene even if it cannot be judged as a dark scene based on the APL detection result, thereby preventing black shadows from appearing.

In addition, in the above description, the structure of each image display device when the light source control method of the fourth embodiment is used for the control of the aperture and the control of the light adjustment element is briefly described, but the control of the light source and the aperture can also be performed simultaneously. The control of the light source and the control of the dimming element can also be performed at the same time, and the control of the light source, the control of the aperture and the control of the dimming element can also be performed at the same time. The configuration of the image display device in these cases will be briefly described below.

Fig. 25 is a block diagram showing the structure of an image display device when the light source control method according to the fourth embodiment is used for controlling the light source and the diaphragm. In FIG. 25, the image display device has an APL detecting unit 2, a histogram generating unit 15, an aperture control data generating unit 25, an aperture driving circuit 20, a light source control data generating unit 16, an LPF 4, a light source driving circuit 5, a light source 6, Optical system 17 , display element 8 , image signal processing circuit 9 , display element drive unit 10 , microcomputer 11 and timer 12 . The optical system 17 includes an aperture 18 . In addition, in FIG. 25 , the same reference numerals are assigned to the same configurations as those in FIG. 21 or 23 . In this way, even in the case where only a part of the dark scene has a particularly bright part, if it cannot be judged as a dark scene based on the APL detection result, it can be judged as a dark scene, and black shadows can be prevented from appearing.

Fig. 26 is a block diagram showing the configuration of an image display device when the light source control method according to the fourth embodiment is used to control the light source and the light control element. In FIG. 26 , the image display device has an APL detection unit 2, a histogram generating unit 15, an aperture control data generating unit 26, a dimming element driving circuit 23, a light source control data generating unit 16, an LPF 4, a light source driving circuit 5, a light source 6. Dimming element 21 , optical system 7 , display element 8 , image signal processing circuit 9 , display element drive unit 10 , microcomputer 11 and timer 12 . In addition, in FIG. 26 , the same reference numerals are assigned to the same configurations as those in FIG. 21 or 24 . In this way, even in the case where only a part of the dark scene has a particularly bright part, if it cannot be judged as a dark scene based on the APL detection result, it can be judged as a dark scene, and black shadows can be prevented from appearing.

Fig. 27 is a block diagram showing the structure of an image display device when the light source control method according to the fourth embodiment is used to control the light source, diaphragm, and dimming element. In FIG. 27, the image display device has an APL detecting unit 2, a histogram generating unit 15, an aperture control data generating unit 25, an aperture driving circuit 20, a dimming element control data generating unit 25, a dimming element driving circuit 23, and a light source. Control data generation unit 16, LPF 4, light source drive circuit 5, light source 6, light adjustment element 21, optical system 17, display element 8, image signal processing circuit 9, display element drive unit 10, microcomputer 11 and timer 12. The optical system 17 includes an aperture 18 . In addition, in FIG. 27 , the same reference numerals are assigned to the same configurations as those in FIG. 21 , FIG. 23 or FIG. 24 . In this way, even in the case where only a part of the dark scene has a particularly bright part, if it cannot be judged as a dark scene based on the APL detection result, it can be judged as a dark scene, and black shadows can be prevented from appearing.

As mentioned above, by combining the control of the light source with the control of the iris or the dimming element, the luminance can be adjusted dynamically according to the scene of the image more effectively, and the insufficient brightness of the bright scene and the black shadow of the dark scene can be further improved. Emerging issues can improve the sense of contrast.

Fifth Embodiment

Fig. 28 is a block diagram showing the structure of an image display device according to a fifth embodiment of the present invention. In Fig. 28, the image display device has a display element 8, a light source 6, a mirror 27, a condenser lens 28, a projection lens 29, a screen 30, an APL detection unit 2, an intermediate control signal generation unit 31, and a signal change control unit 32. , a light source driving unit 5 , an image signal processing unit 9 , a display element driving unit 10 and a system control unit 41 . In addition, in FIG. 28 , the same reference numerals are assigned to the same configurations as those in FIG. 1 .

The display element 8 has a light modulation effect, and the light source 6 illuminates the display element 8 . Reflector 27, condenser lens 28 and projection lens 29 are illumination optical systems, reflector 27 reflects the light irradiated by light source 6, and condenser lens 28 condenses the light illuminated by light source 6 and the light reflected by reflector 27 , the projection lens 29 enlarges and projects the image displayed on the display element 8 onto the screen 30 . In addition, the reflection mirror 27 and the condensing lens 28 are structures corresponding to the optical system 7 shown in FIG. 1 . An image signal is input to the APL detection unit 2, the APL of the input image signal is detected, and the detection result is output as an APL signal. The intermediate control signal generation unit 31 generates an intermediate control signal as a basis of a light source control signal for controlling the light emission luminance of the light source 6 based on the APL signal output from the APL detection unit 2 . The signal change control unit 32 controls the level change of the intermediate control signal output by the intermediate control signal generating unit 31 to generate and output a light source control signal for controlling the luminance of the light source 6 . The light source driving unit 5 drives the light source 6 under conditions corresponding to the light source control signal from the signal change control unit 32 . The image signal processing unit 9 processes the input image signal into a form suitable for display by the display element 8 . The display element driving unit 10 drives the display element 8 based on the image signal processed by the image signal processing unit 9 . The system control unit 41 controls the control units described above.

Fig. 29(a) shows an example of the APL signal outputted by the APL detection unit 2 changing with time, and Fig. 29(b) shows the light source control signal driven by the APL signal shown in Fig. 29(a). Time-dependent changes in the luminance of the light source 6 .

Next, referring to Fig. 28 and Fig. 29, the operation of the image display device of the present embodiment, especially the control of the luminance of the light source 6 will be described in detail. In addition, since the operations of the image signal processing unit 9 and the display element driving unit 10 are well known, description thereof will be omitted.

The APL detection unit 2 detects the APL for each unit field period with respect to the luminance signal component of the input image signal, and outputs the detection result as an APL signal. The intermediate control signal generation unit 31 converts the level of the APL signal output by the APL detection unit 2 every unit field period according to the set conversion function or conversion table, and generates an intermediate control signal. This intermediate control signal is a signal serving as a basis for a light source control signal for finally controlling the light emission luminance level of the light source. The intermediate control signal is generated such that the luminous luminance of the light source 6 increases when the APL is high, and the luminous luminance of the light source 6 decreases when the APL is low. Here, the conversion function or the conversion table may be loaded in the intermediate control signal generation unit 31 in advance, or may be appropriately set by the system control unit 41 . Since the intermediate control signal is directly generated from the APL of the video signal, it is a signal that changes every unit field period following changes in the APL of the video signal. The signal change control unit 32 controls the change speed of the intermediate control signal that changes during each unit field period according to the set time constant. In this way, the intermediate control signal becomes a signal with a slow change speed, and is output as a light source control signal . The detailed operation of the signal change control unit 32 will be described later. The light source driving unit 5 drives the light source 6 under a driving condition corresponding to the light source control signal, thereby changing the light emission luminance of the light source 6 .

As a reference here, consider the case where the light source 6 is controlled by directly inputting an intermediate control signal to the light source driving unit 5 without using the signal change control unit 32 . In this case, as described above, since the intermediate control signal directly reflects the change in APL of the image signal as it is, the luminance of light emitted by the light source also changes every unit field period. In this way, if the luminance of the light source 6 is controlled in such a manner that the change in APL is directly reflected, the change of luminance will be too fast, and the image will flicker, degrading the display quality. In addition, since the light source driving unit 5 and the light source 6 have time constants for changes in control states, changes in luminance lag behind changes in APL. In this way, for example, when a bright scene suddenly changes to a dark scene, the luminance of the picture lags behind the change of the scene and changes abruptly, resulting in a very uncomfortable image. Also, since the light source 6 controls the luminance of the light source 6 by directly reflecting changes in APL, frequently changing the light emitting state accelerates the deterioration of the electrodes or reduces the reliability of the light source 6 .

Therefore, in order to solve the above problems, it is considered to pass the intermediate control signal through a low-pass filter, so as to reduce the change of the light emitting state of the light source. However, the time constant of the low-pass filter made of electrical parts reaches about 0.1 second at most, and the brightness change of the picture due to the brightness change of the light source 6 is still felt, and the problem of poor display quality has not been completely solved.

Therefore, in this embodiment, the signal change control unit 32 is provided in order to solve the above-mentioned problem of deterioration of display quality due to perceived change in screen luminance. The signal change control unit 32 is used to control the change speed of the intermediate control signal, and the change speed of the luminous luminance of the light source 6 is reduced to an imperceptible level. Therefore, it is possible to perform display with a high sense of 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 times the light emission state of the light source 6 changes can be reduced, and the reliability of the light source 6 can be prevented from being lowered. In addition, in order to prevent the deterioration of the display quality due to the change of the luminous luminance of the light source 6, it is obtained through experiments, as shown in FIG. When the highest luminance L2 changes linearly and from the highest luminance to the lowest luminance, the required time T0 is at least 0.3 seconds. The luminance of the light source 6 may be changed. In addition, here is only the time required to assume that the luminance of the light source changes linearly from the highest luminous luminance to the lowest luminous luminance, and the time required to assume a linear change from the lowest luminous luminance to the highest luminous luminance. The degree to which the desired rate of change is expressed. Needless to say, what is important in actually controlling the luminance of a light source is of course the speed of change.

Next, the signal change control unit 32 responsible for controlling the speed of change in luminance of the light source as described above will be described in detail. FIG. 30 is a block diagram showing the structure of the signal change control unit 32. As shown in FIG. The signal change control unit 32 includes a comparator 301 , an adder 302 , a subtractor 303 , a selector 304 , a difference calculator 305 , a comparator 306 and a selector 307 . Its working condition is described below.

The intermediate control signal generated by the intermediate control signal generation unit 31 is input to the signal change control unit 32 . In the signal change control unit 32 , a light source control signal is generated according to the intermediate control signal, and is output by the selector 307 . The light source control signal output by the selector 307 is fed back to the comparator 301 , the adder 302 and the subtractor 303 . The signal change control unit 32 adds or subtracts the light source control signal one unit field period ago to the change amount setting signal from the system control unit 41 in the adder 302 or the subtractor 303, and by doing this, each unit field During this period, the light source control signal is updated sequentially and then output. This change amount setting signal sets the change amount using FIG. 29 as described above, and is set to such a degree that the change speed of the light emission luminance of the light source 6 is not felt. The input intermediate control signal is compared with the light source control signal before one unit field period in the comparator 301, and the output of the adder 302 or the output of the subtractor 303 is selected by the selector 304 according to the comparison result. output it. For example, when the intermediate control signal level of the current unit field period is greater than the light source control signal level before one unit field period, the output of the adder 302, that is, the light source control signal before one unit field period plus a specified amount of change is sent from the selector 304 output. Here, by arbitrarily setting the change amount setting signal from the system control unit 41, the change speed of the light source control signal can be freely controlled. In addition, the update interval of the light source control signal may not be every unit field period, but every several unit field periods. In this way, the change speed of the light source control signal can be further slowed down. This is because the change speed of the light source control signal is proportional to the quotient of dividing the change amount set by the change amount setting signal by the update interval of the light source control signal.

The difference calculator 305 obtains the difference between the output of the selector 304 and the intermediate control signal. The differential output from this differential calculator 305 is compared with an error amount setting signal input from the system control unit 41 in a comparator 306 . As a result, when the differential output of the differential calculator 305 is smaller than the error amount setting signal, the input intermediate control signal is selected by the selector 307, and the intermediate control signal is directly output as the light source control signal as it is. In addition, when the differential output of the differential calculator 305 is larger than the error amount setting signal, the output from the selector 304 is selected in the selector 307, thereby outputting the output as a light source control signal. In addition, it is not necessarily necessary to select and output the intermediate control signal and the output of the selector 304 according to the error amount, but if the output is selected based on the error amount setting signal in this way, the set value of the change amount setting signal is used. , although the level of the intermediate control signal is constant, the problem that the output of the selector 304 is unstable and in an oscillating state can be prevented, so it is ideal. In addition, in order to prevent the oscillating state reliably, it is preferable to set the error amount to half of the change amount.

As described above, according to the fifth embodiment, the luminance of the light source 6 is controlled in conjunction with the level of APL, and the luminance of the light source 6 is controlled to be lowered in a dark scene with a low APL such as movie software, so that the difference can be improved. It can provide higher-quality images to solve problems such as the appearance of black shadows on the screen and the deterioration of image quality. Moreover, especially by using the signal change control unit 32, the speed of change of the luminous brightness of the light source 6 is reduced to the extent that the viewer does not feel the change of the luminance of the light source. There is a great effect such as a decrease in the lifetime characteristic of the light source 6 .

Embodiment 6

Fig. 31 shows the configuration of an image display device according to a sixth embodiment of the present invention. In addition, since the image display device shown in FIG. 31 differs from the image display device shown in FIG. 28 only in the signal change control unit 33 and the system control unit 42, descriptions of other configurations are omitted. In addition, in FIG. 31 , the same reference numerals are assigned to the same configurations as those in FIG. 28 , and description thereof will be omitted.

In the present embodiment, signal change control unit 33 controls the change speed of the intermediate control signal generated in intermediate control signal generating unit 31 to generate a light source control signal for controlling the luminance of light source 6 as in the fifth embodiment. However, the speed of change is controlled so that the speed of change when the luminous luminance of the light source 6 is decreased is faster than that when the luminous luminance of the light source 6 is increased. The operation of the signal change control unit 33 will be described in detail below.

Fig. 32(a) shows an example of the APL signal output by the APL detection unit 2 changing with time, and Fig. 32(b) shows the light source control signal driven by the APL signal shown in Fig. 32(a). Time-dependent changes in the luminance of the light source 6 .

The signal change control unit 33 controls the change speed of the intermediate control signal that changes every unit field period with a set time constant, and converts it into a light source control signal with a slow change speed. At this time, it is controlled to detect whether the intermediate control signal changes to the direction of increasing the luminous luminance of the light source 6, or vice versa, and changes to the direction of reducing the luminous luminance of the light source 6. When the direction is changed, the speed of change of the light source control signal is increased compared with the time of control in the direction of increasing the luminous luminance, so that the luminous luminance of the light source 6 is changed at a faster speed. That is, as shown in Fig. 32 (a) and Fig. 32 (b), if the time when the luminous luminance of the light source 6 is changed from the lowest luminous luminance level L1 to the highest luminous luminance level L2 is time T1, then Control is performed so that the time when the emission luminance of the light source 6 changes from the maximum emission luminance level L2 to the minimum emission luminance level L1 is time T2 which is shorter than time T1. In addition, in this case, of course, the speed of change is also important.

FIG. 33 shows the structure of the signal change control unit 33. As shown in FIG. Here, the difference between the signal change control unit 33 and the signal change control unit 32 of the fifth embodiment shown in FIG. , and descriptions of other identical structures are omitted.

In the signal change control means 33, the change amount setting signal is input to the adder 302 when the luminance increases, and the change amount setting signal is input to the subtractor 303 when the luminance decreases. By configuring the signal change control unit 32 in this way, it is possible to separately set the change speeds when increasing and decreasing the light emission luminance of the light source 6 . In addition, by always setting the change amount setting signal when the luminance decreases to be greater than the threshold value of the change amount setting signal when the luminance increases, the light emission luminance when the luminance of the light source 6 changes more quickly in the direction of decreasing luminance can be achieved. speed of change.

However, as described above, if the change speed of the luminance of the light source is accelerated, the change of the luminance of the light source will be perceived and the quality of the displayed image will deteriorate. From this point of view, it is preferable that the speed of change of the luminance of the light source is slower. However, especially in movie software, etc., there are many darker scenes, especially the problem that the display image quality degradation caused by the emergence of black shadows in dark scenes should be avoided. Therefore, when changing from a dark scene to a bright scene, in order to suppress the perception of changes in the luminance of the light source as much as possible, the luminance of the light source should be changed relatively slowly. On the other hand, when changing from a bright scene to a dark scene, in order to To suppress the appearance of black shadows, the luminance of the light source should be changed relatively quickly. By controlling in this way, the quality of the displayed image can be improved as a whole.

In addition, since the luminance of the light source 6 is rapidly reduced according to the change of the image, the viewer can feel that the luminance of the image is brighter by using the synergistic effect of the reduction of the luminance of the image and the reduction of the luminance of the light source. Further darkening enables more effective images to be displayed in movie software where dark scenes are important.

As described above, according to the sixth embodiment, by controlling the speed of change when the luminous luminance of the light source 6 changes in the direction of decrease is faster than the speed of change when the luminous luminance of the light source 6 is changed in the direction of increase, it is possible to suppress image distortion. The unnatural feeling caused by the luminance change of the light source 6 when the scene changes from a dark scene to a bright scene, especially when the image scene changes to a dark scene, can be improved by reducing the luminance of the light source 6 more quickly. 6. The decrease in display quality caused by the appearance of dark shadows due to the high luminous brightness improves the quality of displayed images as a whole.

Seventh Embodiment

Fig. 34 is a block diagram showing the structure of an image display device according to a seventh embodiment of the present invention. In addition, because the difference between the image display device shown in FIG. 34 and the image display device shown in FIG. 28 is only the signal change control unit 34, the light source luminance state detection unit 35 and the system control unit 43, so for other For the same configuration, the same reference symbols are attached, and descriptions thereof are omitted.

In this embodiment, the signal change control unit 34 controls the change speed of the intermediate control signal generated by the intermediate control signal generating unit 31 to generate a light source control signal for controlling the luminance of the light source 6 as in the fifth embodiment. The light source luminance state detection unit 35 monitors the light source control signal output by the signal change control unit 34 all the time, and controls according to the progress of the luminous state of the light source 6, so that the control of the luminance of the light source 6 to track the APL is temporarily interrupted, Or start over. This control is performed, for example, by outputting a tracking control signal from the light source emission luminance state detection unit 35 to the signal change control unit 34, and the signal change control unit 34 fixes the level of the light source control signal according to the tracking control signal, thereby making the light source Lui's tracking of APL was temporarily interrupted.

Next, referring to FIG. 35( a ) and FIG. 35( b ), the change of the light emission state of the light source 6 caused by the control of the light source light emission luminance state detection unit 35 will be described in detail. Fig. 35(a) shows an example of the APL signal output by the APL detection unit 2 changing with time, and Fig. 35(b) shows the light source control signal driven by the APL signal shown in Fig. 35(a). Time-dependent changes in the luminance of the light source 6 . In this embodiment, the light source luminance state detection unit 35 is neither at the lowest luminance level L1 nor at the highest luminance level L2, but keeps transitioning in the intermediate region between them. The elapsed time in is counted. Moreover, when the predetermined time Ta preset by the system control unit 43 has been counted, the light source luminous luminance state detection unit 35 sends a tracking control signal to the signal change control unit 34, so that the luminous luminance of the light source 6 can only be interrupted by tracking the APL change. A certain time Tb, and maintain the luminance of the interruption moment. Then, after the interruption period Tb, it enters a waiting state, and waits for the emission luminance (thin line portion in FIG. After the luminance (the thick line part in FIG. 35( b )) is within the predetermined level difference, the signal change control unit 34 restarts the control of making the luminous luminance of the light source 6 track the APL by using the tracking control signal,

In the above, the timing of resuming the control of the light source is regarded as waiting for the luminous luminance when the control of the light source 6 is continued without interruption by the light source control signal and the luminous luminance of the light source 6 maintained at present to be within a predetermined level difference. , but not necessarily limited thereto, for example, light source control may be restarted immediately after the tracking interruption period Tb elapses. However, the method of restarting the tracking after waiting for the luminous luminance when the control of the light source 6 is continued without interruption by the light source control signal and the luminous luminance of the light source 6 maintained at present is within a predetermined level difference, there is no reason. Discomfort in image display caused by immediately resuming interrupted light source control is therefore desirable.

FIG. 36 shows the configuration of the light source emission luminance state detection unit 35 of this embodiment. The light source control signal output by the signal change control unit 34 is input to the comparator 501 and the comparator 502 . The comparator 501 compares the light source control signal with the highest luminance (L2) setting, and the comparator 502 also compares the light source control signal with the lowest luminance (L1) setting signal. In addition, both the highest luminance (L2) setting signal and the lowest luminance (L1) setting signal are supplied from the system control unit 43 . As a result of the comparison, when the current emission luminance is in an intermediate state greater than the minimum luminance L1 and less than the maximum luminance L2, the AND circuit 503 outputs a control signal to the timer circuit 505 . The first timer circuit 505 starts time counting. While the luminance is in the intermediate state, the first timer circuit keeps counting. Then, if the setting time Ta set by the system control unit 43 passes through, the first timer circuit 505 outputs a tracking control signal to the signal change control unit 34, interrupts the luminance control of the light source 6 tracking APL, and simultaneously makes the second The timer circuit 506 starts counting.

When the set time Tb set by the system control unit 43 elapses, the second timer circuit 506 sends a control circuit to the OR circuit 504 to reset the first timer circuit 505 to zero. If the first timer circuit is cleared, the tracking control signal output by the first timer circuit is cleared, allowing the luminance control of the light source 6 in the signal change control unit 34 to be restarted. If the signal change control unit 34 detects that the tracking control signal is cleared, it will compare the luminance of the currently maintained light source 6 with the intermediate control signal output by the intermediate control signal generating unit 31, and work when the difference between the two is within a certain range. , so that the luminance control of the light source 6 is resumed. In addition, in the counting process of the first timer circuit 505, when the luminous brightness reaches the highest brightness (L2) or the lowest brightness (L1), the comparators 501, 502 and the OR circuit 504 are used to set the first timer circuit 505 cleared.

As described above, according to the seventh experimental form, in the luminance control of the light source of the image display device, when the luminance of the light source is in the intermediate state for a certain period of time (Ta), the control is performed so that the interruption of the period of time (Tb) affects the APL. In this way, it is possible to prevent the reduction of the life of the light source caused by continuously changing the luminance of the light source for a long time.

In addition, there is generally a trade-off relationship between improving the display quality by tracking the luminance of the light source based on the APL, and improving the life of the light source by discontinuing the luminance control of the light source. Therefore, for example, simply interrupting the light source control every time at a predetermined time and only for a predetermined period only gives priority to improving the life of the light source rather than improving the display quality. However, in the present embodiment, since the control of the light source is temporarily suspended whenever the light source continues to change in luminance in an intermediate state for a predetermined time or longer, advantages beyond a simple trade-off relationship can be obtained. This situation is explained below.

As a hypothetical example for comparison with the present embodiment, a case where the control of the light source is simply interrupted for a predetermined period every time at a predetermined time will be described below. Fig. 37(a) shows an example of the temporal change of the APL signal output from the APL detection unit in this hypothetical example. FIG. 37( b ) shows the change with time of the luminance of the light source driven by the light source control signal generated from the APL signal shown in FIG. 37( a ). In this hypothetical example, as shown in FIG. 37( a ), when the APL signal level is Y or lower, the light source is driven at the lowest luminance L1, and when it is X or higher, the light source is driven at the highest luminance L2. In this hypothetical example, since the light source control is simply interrupted for a predetermined period at a predetermined time every time, the bold line in FIG. Looking at the thick line, the luminance of the light source reaches a certain level L2 for a short period of time before the "interruption period" shown in the figure. Therefore, in this case, even if the luminance control of the light source is not interrupted during the interruption, it should not have any profound influence on the life of the light source at all. However, according to this hypothetical example, if the control of the light source is interrupted indiscriminately, the appearance of black shadows and the like cannot be prevented during this period, that is, the display quality cannot be improved.

On the other hand, according to the present embodiment, such unnecessary interruption of the light source control is not performed, and the brightness control of the light source is interrupted only when the brightness of the light source changes in an intermediate state for a predetermined period or more. Therefore, it is possible to achieve an effect beyond a mere trade-off relationship in which the control of the light source luminance is interrupted at a minimum necessary level while trying to improve the display quality.

Eighth embodiment

Fig. 38 shows the configuration of an image display device according to an eighth embodiment of the present invention. In addition, since the image display device shown in FIG. 38 differs from the image display device shown in FIG. 28 only in the intermediate control signal generation unit 36, the signal change control unit 37 and the system control unit 44, for other configurations Description is omitted. In addition, in FIG. 38 , the same reference numerals are assigned to the same configurations as those in FIG. 28 , and description thereof will be omitted.

In this embodiment, the system control unit 44 controls the above-mentioned control units, especially sends a luminance control squelch signal to the intermediate control signal generation unit 36 , and sends an initial value setting signal to the signal change control unit 37 .

The intermediate control signal generating unit 36 is the same as the above-mentioned embodiment, and converts the input APL signal into a light source control signal for controlling the luminance level of the light source 6 in each unit field period according to the set conversion function or conversion table. The basic intermediate control signal. The intermediate control signal is controlled in such a way that when the APL is high, the luminous luminance of the light source 6 is increased, and when the APL is low, the luminous luminance of the light source 6 is decreased.

The intermediate control signal generated by the intermediate control signal generating unit 36 is a signal that changes every unit field period due to changes in the APL of the image signal. Here, the change threshold level APLmin is preset in the intermediate control signal generator 36, and when the change in APL in a unit field period is smaller than the change threshold level APLmin, the intermediate control signal is controlled so as not to change. With this processing, when the APL of the image signal changes very little, it is controlled so that the luminance of the light source 6 does not change, so frequent changes in the driving conditions of the light source can be reduced, and light source damage caused by changes in the driving conditions of the light source can be reduced. deteriorating.

In addition, in the intermediate control signal generation unit 36, when the image signal is in an unstable state such as when the input image signal is switched, in order to prevent the light source luminance control from following the unstable image signal, the system control unit 44 Input the luminance control squelch signal. When the luminance control squelch signal is on, the intermediate control signal is also controlled so as not to change.

The signal change control unit 37 converts the intermediate control signal that changes every unit field period into a light source control signal with a slow change speed by using a set time constant. Next, referring to FIGS. 39( a ) to 39 ( c ), the change of the light emitting state of the light source 6 by the control of the signal change control unit will be described in detail.

Fig. 39 (a) shows an example of the APL signal output by the APL detection unit 2 changing with time, and Fig. 39 (b) shows an example of the luminance control squelch signal changing with time when the input image signal is switched. Example, Fig. 39 (c) is the luminous luminance of the light source 6 driven by the light source control signal generated according to the APL signal shown in Fig. 39 (a) and Fig. 39 (b) and the luminous luminance control squelch signal. Variety.

Consider now the case where the input image signal is switched from the image signal A to the image signal B at times t1 to t2. Furthermore, the APL signal obtained from each image signal before and after the image signal switching is set as shown in FIG. 39(a). At this time, the luminance control squelch signal supplied to the intermediate control signal generation unit 36 is controlled by the system control unit 44 so that the image signal A is switched from the time t1 to the switching time as shown in FIG. 39(b). After the image signal B is obtained, the operation of each control unit is in the on state until time t3 when the operation of each control unit becomes stable. In the intermediate control signal generation unit 36, since the intermediate control signal is controlled so as not to change while the emission luminance control squelch signal is on, the light source control signal does not change as a result, as shown in FIG. 39(c). Between the time t1 and the time t3, the luminance of the light source does not change.

Next, consider a state in which the emission luminance control squelch signal is turned off at time t3 and the control of the intermediate control signal generation unit 36 is resumed. For example, assuming that the image signal A is the image signal shown in FIG. 39(a), the state before the time t1 is a state where the APL is low, and the image signal B after switching is the state after the time t2, that is, APL is in a sustained high state. In this case, as shown in FIG. 39(c), immediately before the switching of the image signal A, the luminous intensity of the light source 6 is in a low state, and the luminous luminance is maintained while the luminous luminance control squelch signal is in the on state. degree is low. Then, when the luminance control squelch signal is off at time t3 and the control by the intermediate control signal generation unit 36 is restarted, if the control is continued in the signal change control unit 37 as it is, the APL of the image signal B The high state remains constant, and the signal change control unit 37 starts tracking from the state immediately before time t3, that is, the state in which the light source luminance control power rate is low (the state indicated by the dotted line in FIG. 39( c )). Therefore, the APL state of the actual image does not match the luminance state of the light source, and the displayed image has an uncomfortable feeling.

Therefore, in this embodiment, in order to solve the above-mentioned problems, an initial value setting signal generated by the system control unit 44 is additionally introduced. The signal change control unit 37 resets the control state. In this way, since the control can be restarted from the reset time regardless of the past control experience, it is possible to display the feeling of discomfort caused by the inconsistency between the light source luminance control and the displayed image when the image signal is switched. image.

The signal change control unit 37 will be described in detail below. FIG. 40 shows the configuration of the signal change control unit 37. As shown in FIG. In addition, since the signal change control unit 37 shown in FIG. 40 differs from the signal change control unit 32 shown in FIG. and omit the description.

The selector 701 is controlled by an initial value control signal from the system control unit 44 . The selector 701 switches the signal to be fed back to the adder 302 , the subtractor 303 and the comparator 301 according to the initial value control signal. If it is described more specifically, the output of the selector 307 is usually supplied to the above-mentioned parts, and at the time t3 shown in FIG. The initial value control signal of the unit 44 is to supply the intermediate control signal from the intermediate control signal generating unit 36 to the above-mentioned parts. After the signal switching, by feeding back the intermediate control signal as it is, the past control state of the light source control signal can be reset, the light source control state can be reset, and the light source control signal can be immediately adjusted to the level corresponding to the APL of the current image signal. flat.

As described above, according to the eighth embodiment, by employing the same configuration as the advanced linkage control of the APL to control the luminous luminance of the light source, the luminous luminance of the light source is lowered in a dark scene such as movie software where the APL is low. Therefore, it can improve the problem of displaying image quality in dark scenes such as black shadows appearing on the screen, and can provide higher-quality images. In particular, by using the initial value control signal to reset the light source control signal, it is possible to start the control of the light source luminance under new conditions when the previous control state is not intended to be continued when the input image signal is switched or the like. Therefore, it is possible to avoid the problem that the control state of the luminance of the light source does not match the state of the displayed image, and it is possible to display an image corresponding to the state of the displayed image without discomfort.

As described above, the image display device and the image display method related to the present invention are in the image display device composed of a display element having a transmissive line reflection light modulation function and a light source for irradiating light to the display element, Improve the quality of display images caused by lack of contrast and black shadows, and improve the reliability of the device.

Claims (6)

1. image display apparatus, by irradiation on the display element with optical modulation effect of transmission-type or reflection-type from the light of light source with displayed image, comprising:

The briliancy level of input image signal is divided into a plurality of briliancy level districts and detects the histogram generating apparatus of the histogram distribution in each briliancy level district; And

The light amount control device that the light quantity of described light source is controlled,

When the histogram distribution at least one the briliancy level district in described a plurality of briliancy level district that described histogram generating apparatus is detected during greater than the threshold value of regulation, described light amount control device is controlled the light quantity of described light source, and the feasible light quantity that is radiated on the described display element is fixed on the minimum levels of regulation.

2. image display apparatus as claimed in claim 1 is characterized in that, also comprises being arranged between described light source and the described display element being used to control the aperture that is radiated at the light quantity on the described display element,

When the histogram distribution at least one the briliancy level district in described a plurality of briliancy level district that described histogram generating apparatus is detected during greater than the threshold value of regulation, control described light source and aperture, the feasible light quantity that is radiated on the described display element is fixed on the minimum levels of regulation.

3. image display apparatus as claimed in claim 1 is characterized in that, also comprises being arranged between described light source and the described display element being used to control the Light modulating device that is radiated at the light quantity on the described display element,

When the histogram distribution at least one the briliancy level district in described a plurality of briliancy level district that described histogram generating apparatus is detected during greater than the threshold value of regulation, control described light source and Light modulating device, the feasible light quantity that is radiated on the described display element is fixed on the minimum levels of regulation.

4. image display apparatus, by irradiation on the display element with optical modulation effect of transmission-type or reflection-type from the light of light source with displayed image, comprising:

The briliancy level of input image signal is divided into a plurality of briliancy level districts and detects the histogram generating apparatus of the histogram distribution in each briliancy level district; And

Be arranged between described light source and the described display element and be used to control the aperture that is radiated at the light quantity on the described display element,

When the histogram distribution at least one the briliancy level district in described a plurality of briliancy level district that described histogram generating apparatus is detected during greater than the threshold value of regulation, control described aperture, the feasible light quantity that is radiated on the described display element is fixed on the minimum levels of regulation.

5. image display apparatus, by irradiation on the display element with optical modulation effect of transmission-type or reflection-type from the light of light source with displayed image, comprising:

The briliancy level of input image signal is divided into a plurality of briliancy level districts and detects the histogram generating apparatus of the histogram distribution in each briliancy level district; And

Be arranged between described light source and the described display element and be used to regulate the Light modulating device that is radiated at the light quantity on the described display element,

When the histogram distribution at least one the briliancy level district in described a plurality of briliancy level district that described histogram generating apparatus is detected during greater than the threshold value of regulation, control described Light modulating device, the feasible light quantity that is radiated on the described display element is fixed on the minimum levels of regulation.

6. as each described image display apparatus in the claim 1 to 5, it is characterized in that described at least one the briliancy level district in described a plurality of briliancy level district is near the district of black-level.

Images