JP3919014B2 - Video display device and video display method - Google Patents

Description

  The present invention relates to an image display apparatus and an image display method, and more specifically, an image is obtained by irradiating light from a light source to a single or a plurality of display elements having a transmission or reflection type light modulation action. The present invention relates to a video display device and a video display method.

  As a video display device comprising a display element having a transmissive or reflective light modulation action and a light source for irradiating the display element with light, there are a direct-view liquid crystal display device and a projection display device so-called projector. .

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

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

  Compared to self-luminous display devices such as CRTs for both direct-view liquid crystal display devices and projectors, there is a strong demand for improving the quality of displayed images against lack of brightness in bright scenes and black floats in dark scenes. As a method for further improving the quality of the displayed video, a method of dynamically changing the luminance of the light source according to the scene of the video is described in, for example, “Liquid Crystal Display Device” described in Patent Document 1 (hereinafter simply referred to as the first conventional technique). Some have been devised, such as “Liquid Crystal Projector” (hereinafter simply referred to as “second conventional device”) described in Patent Document 2.

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

In the second conventional apparatus, the maximum value of the input video signal is detected. When the maximum value is high, the light source luminance is increased, and when the maximum value is low, the light source luminance is decreased. In the second conventional apparatus, the relative contrast ratio between the case where the maximum value is high and the case where the maximum value is low is thus increased.
JP-A-5-127608 Japanese Patent Laid-Open No. 6-160811

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

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

  In the second conventional apparatus, the light source luminance is dynamically controlled according to the input video signal. However, since the light source luminance is controlled according to the maximum value of the input video signal, it is locally maximized despite the low APL. When the value is high, it is conceivable that black floating occurs in the dark part of the video. The second conventional device is a “liquid crystal projector”, but discharge-type light sources (xenon lamps, high-pressure mercury lamps, etc.) commonly used for projectors are stable when repeated sudden changes in driving conditions. It is conceivable that the reliability of the lamp may be impaired due to deterioration of the lamp performance (deterioration of lighting startability, occurrence of flicker during steady lighting) and deterioration of life characteristics.

  Therefore, an object of the present invention is to provide a display image quality problem (contrast sensation) in a video display device including a transmissive or reflective light-modulating display element and a light source that irradiates the display element with light. Deficiency, black float). Another object of the present invention is to improve a decrease in reliability of a light source, a diaphragm, or a light control element for adjusting the amount of light when the amount of light applied to the display element is dynamically controlled.

A first aspect of the present invention is an image display device for displaying an image by irradiating light from a light source to a single or a plurality of transmission type or reflection type display elements having a light modulation action. The display element is divided based on the histogram generation means for dividing the luminance level of the signal into a plurality of luminance level sections and detecting the histogram distribution for each of the luminance level sections, and the histogram distribution for each of the divided sections detected by the histogram generation means. A light amount control data creating unit that creates light amount control data for controlling the amount of light to be irradiated, and a light amount control unit that controls the amount of light emitted to the display element based on the light amount control data. during which a histogram distribution of the split segment each detected in the histogram creating means is in a predetermined distribution state, the display element Light amount Isa becomes constant at a predetermined level corresponding to a predetermined distribution state, between the histogram distribution of each divided segment is not in the predetermined distribution state, the average luminance level of the amount of light radiated on the display device the input video signal It is characterized in that the light quantity control data that changes in accordance with is created.

In a second aspect based on the first aspect, the light quantity control data creating means is configured such that the histogram distribution of at least one brightness level among the plurality of brightness level sections detected by the histogram creating means is lower than a predetermined threshold value. big during is characterized in that the amount of light radiated on the display device to create a light amount control data such that the constant at a predetermined level.

In a third aspect based on the first aspect, the light quantity control data creation means is a distribution state in which the histogram distribution detected by the histogram creation means is determined to determine that the video scene related to the input video signal is a dark scene. while in is characterized in that amount of light radiated on the display device to create a light amount control data such that the constant predetermined minimum level.
In a fourth aspect based on the first aspect, the light quantity control data creating means is a distribution state in which the histogram distribution detected by the histogram creating means determines that the video scene related to the input video signal is a bright scene. During this period, the light amount control data is created so that the light amount irradiated to the display element is constant at a predetermined maximum level.

  According to the first aspect of the invention, by controlling the amount of light applied to the display element based on the histogram distribution, it is possible to more accurately extract the features of the video scene that cannot be uniquely determined from the APL detection result alone. The quality of the displayed video can be improved by more appropriately controlling the amount of light applied to the display element according to the characteristics of the video scene.

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

  According to the third aspect of the present invention, even if there is a particularly bright part in a dark scene and it is not possible to determine that the scene is dark from the APL detection result, it is dark. It can be determined that the scene is a scene, and the amount of light applied to the display element can be controlled so as to prevent black floating.

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

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

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

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

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

  By the way, especially when movie software is used, the movie has a relatively large number of dark scenes on the entire screen, so the influence of the black floating is large, and the occurrence of the black floating greatly impairs the display quality of the video. Therefore, it is preferable to prevent black floating to the maximum in a dark scene.

  In addition, when a person watches a movie software, it feels that the contrast is high when the brightness level in a bright scene is large as compared with the dark adaptation memory in a dark scene. On the contrary, when the black level in the dark scene is low as compared with the light adaptation memory in the bright scene, the contrast is high. Increasing the contrast is important for improving the display quality of video. Therefore, it is not preferable that black float occurs or that the brightness of the white peak is lost in a bright scene because this leads to a decrease in contrast.

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

  In FIG. 3, as the first mode of light source control (fixed region Low), when the APL of the input video signal 1 is smaller than the threshold value A1, the light source control level is fixed to L1 (min). As the second mode (variable corresponding region), when the APL of the input video signal 1 is the threshold value A1 to the threshold value A2, the range is from L1 (min) to L2 (max) according to the change of the APL. Variable light source control level. In the third mode (fixed area High), when the APL of the input video signal 1 is larger than the threshold value A2, the light source control level is set to be constant L2 (max).

  In FIG. 3, the relationship between the APL and the light source control level in the variable corresponding region is linear, but is not limited to this, for example, the relationship between the light source control level and the light source driving power, or the light source driving power and the light emission intensity of the light source. If the relationship between and is non-linear, a function that reversely corrects non-linear characteristics in the variable correspondence region may be used. Furthermore, the present invention is not limited to the inverse correction of the nonlinear characteristic, and an arbitrary nonlinear characteristic function may be used.

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

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

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

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

  In the present embodiment, when the APL becomes the fixed region Low and the fixed region High, the light source control level is controlled to be constant at L1 (min) and L2 (max), respectively. There is no need to make the level constant at the minimum or maximum level, and even if it is in the vicinity of those levels, the above problem of black floating in dark scenes and lack of brightness in bright scenes are further improved Needless to say, the effect is achieved. However, if the driving is fixed at the minimum level or the maximum level as in the present embodiment, these effects can be obtained to the maximum, and the driving level of the light source does not fluctuate in a dark scene and a bright scene. This is more preferable because it can also improve the problem of decrease in property.

  In the present embodiment, as shown in FIG. 4, the light source control level is controlled according to the APL for each unit field time Tn. Instead, the average of the APLs for a plurality of unit field times Tn is used. And the light source control level may be controlled based on the average value. For example, assuming that Tn (unit field time) in the upper diagram of FIG. 4 is T2k = (Tn−k + Tn−k + 1 +.. Replace with By doing so, the cycle and amount of dynamic change of the dotted arrows shown in FIG. 5 are reduced. In other words, the fluctuation period of the light source control level in the APL variable corresponding region increases and the amount of change decreases. Therefore, it is possible to further reduce the decrease in the reliability of the lamp. This effect will be described more specifically with reference to FIG. FIG. 6 shows the case of k = 1, and the thick dotted line in the upper diagram shows the average of the APL detection results for each of the three unit fields. Based on this average, the light source control level is controlled as shown in the lower diagram of FIG. Therefore, by controlling the light source based on the average of the APLs of a plurality of unit field times, fluctuations in the light source control level can be reduced compared with the case shown in FIG. it can.

  Although not shown, an LPF may be inserted on the output side of the APL detection unit 2 as a configuration capable of giving an effect similar to the control based on the average of the APL of the plurality of unit field times. . However, in the case of control based on the average of APL, the number of target fields can be accurately defined as an integer as a value of k, and the value of k can be appropriately changed according to the situation by program setting or the like. Therefore, for example, in the variable corresponding region shown in FIG. 5, a control method is also possible in which the rate of change is changed depending on whether the light source luminance is increased or decreased.

  Although the case of dynamically controlling the light source has been described as the first embodiment, the present invention is similarly applied to other cases in which the amount of light finally irradiated to the display element can be controlled. Can do. Hereinafter, the configuration and operation of the video display apparatus when the light source control method of the present embodiment is applied to the control of the diaphragm and the control of the light control element will be described.

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

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

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

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

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

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

  Note that the output signal from the aperture control data creation unit 19 shown in the lower diagram of FIG. 9 is not limited to the case indicated by the solid line, but considers the response and reliability of the aperture drive structure as indicated by the dotted line. Thus, a time delay characteristic may be given to a change in APL.

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

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

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

  Also, when controlling the light source, there is a problem that the life time is impaired if the change speed of the light source power is increased or the number of repetitions of the change is large from the viewpoint of the life reliability of the discharge light source used in the projector. When controlling the diaphragm, although depending on the opening / closing structure of the diaphragm, the influence of the change speed and the number of changes of the driving condition of the diaphragm on the reliability of the diaphragm driving structure is less than when the light source is controlled. For this reason, for example, it is possible to follow the driving conditions of the aperture in field / frame units with respect to changes in APL, which can greatly improve the followability when the brightness of the video scene changes sharply. A better contrast feeling can be obtained according to the change in the brightness of the scene.

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

  It is also possible to perform both light source control and aperture control at the same time. In this case, since the contrast improvement effect is obtained by the product of the contrast improvement effect by the light source control and the contrast improvement effect by the aperture control, it becomes more effective by improving the contrast. At this time, by setting the change rate of the aperture to be faster than the change rate of the light source, the follow-up ability of the light amount to the change of the image scene is improved while eliminating the adverse effect on the life reliability of the light source. Can be

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

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

Next, with reference to FIG. 12 and FIG. 13, the specific processing content of the light control element control data creation part 22 is demonstrated.
A1b and A2b shown in FIG. 12 are preset APL threshold values. The threshold levels of A1b and A2b are threshold values for distinguishing dark scenes and bright scenes, respectively, and are obtained by evaluation of movie software. When using software with many bright scenes other than movie software, these threshold values may be changed according to the video source.

  In FIG. 12, as the first mode of light quantity control (fixed area Low), when the APL of the input video signal 1 is smaller than the threshold value A1b, the light quantity control level is constant at L1a (min). As the second mode (variable corresponding region), when the APL of the input video signal 1 is between the threshold value A1b and the threshold value A2b, the range of L1b (min) to L2b (max) according to the change of APL. Variable light control level. In the third mode (fixed area High), when the APL of the input video signal 1 is larger than the threshold value A2b, the light source control level is set to be constant L2b (max).

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

  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. In FIG. 13, the upper diagram shows a specific example of the dynamic change of the input APL to the dimming element control data creation unit 22, and the lower diagram shows the light amount control level corresponding to the dynamic change of the input APL shown in the upper diagram. Dynamic control of is shown. Tn is a unit field time for detecting APL. According to the control method shown in FIG. 12, when the APL is in the variable corresponding region (A1b to A2b) with respect to the dynamic change of the APL, the light amount control dynamically follows, but the APL is in the fixed region Low and When the fixed region becomes high, the light amount control level is controlled to be constant at L1b (min) and L2b (max), respectively.

  Note that the output signal from the light control element control data creation unit 22 shown in the lower part of FIG. 13 is not limited to the case indicated by the solid line, but considers the response and reliability of the light control element as indicated by the dotted line. Thus, a time delay characteristic may be given to a change in APL.

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

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

  In the case of controlling the light control element, generally, the same effect as in the case of controlling the above-described diaphragm can be obtained. Further, compared to the case of controlling the light source, the dimmer element driving circuit can be realized with a relatively simple circuit at a low voltage when the dimmer element is controlled, and thus can be more easily realized. Furthermore, compared with the case of controlling the diaphragm, when controlling the light control element, there is a degree of freedom in arrangement between the light source and the display element, and the driving circuit is not necessary for driving the light control element. Since it can be realized with a relatively simple structure because only the electric control by is, it can be realized more easily.

  Although it is possible to perform both the light source control and the light control element control at the same time, in this case, the same effect as the case where both the light source control and the aperture control are performed simultaneously can be obtained. it can. Furthermore, it is possible to simultaneously control the light source, the aperture, and the light control element, in which case the contrast improvement effect is the contrast improvement effect by the light source control and the contrast by the aperture control. Therefore, it is more effective to improve the contrast.

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

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

  FIG. 15 shows the relationship between the dynamic change of the APL of the input video signal 1 and the dynamic control of the light source control level. 15, the upper diagram shows a specific example of the dynamic change of the input APL to the light source control data creation unit 13, and the lower diagram shows the movement of the light source control level corresponding to the dynamic change of the input APL shown in the upper diagram. Control. In particular, in the figure below, the solid line indicates the output signal from the light source control data creation unit 13, and the dotted line indicates the output signal from the LPF 4. Tn is a unit field time for detecting APL. As shown in FIG. 15, in the present embodiment, as in the first embodiment, the APL is variable corresponding regions (A1 to A2) with respect to the dynamic change of APL according to the control method shown in FIG. 3 described above. ), The light source control dynamically follows, but when the APL becomes the fixed region Low and the fixed region High, the light source control level is controlled to be constant at L1 (min) and L2 (max), respectively. .

  However, in this embodiment, it is determined whether or not the change in the input APL is smaller than the level of the predetermined determination threshold value APmin. If the change in the APL is smaller than APmin, the above normal control is prioritized. Thus, the light source control level is not changed. More specifically, in the upper diagram of FIG. 15, the change level of APL at time t1 to t2 is smaller than the determination threshold APmin. Therefore, as shown in the lower diagram of FIG. 15, the light source control level is not dynamically changed 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 allowed to follow a minute change in APL. This is because it is not preferable to follow the light source control level with respect to minute changes in APL because the disadvantage of reducing the reliability of the light source is greater than the advantage of improving the contrast.

  As described above, according to the second embodiment, in addition to the effects of the first embodiment, when the change in APL is very small, the previous drive condition is maintained without changing the drive condition of the light source. The frequency of dynamic transition of the light source driving conditions can be reduced. As a result, it is possible to improve the problem of deterioration of stable lighting performance and life characteristics of the light source, and increase the reliability of the light source.

  Note that the control method of the second embodiment can also be applied to control of a diaphragm and a light control element. Hereinafter, a case where the control method of the second embodiment is applied to the control of the diaphragm and the control of the light control element will be described.

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

  FIG. 17 shows the relationship between the dynamic change of the APL of the input video signal 1 and the dynamic control of the light control element control level when the control method of the second embodiment is applied to the control of the light control element. . Also in this case, when the change in APL is smaller than the preset determination threshold APmin, the light amount control level is not changed. Thereby, the fall of the reliability of a light control element by the light control element repeating excessive micro light control operation | movement can be prevented.

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

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

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

  However, in the present embodiment, it is determined whether or not the light source drive level has transitioned to L1 (min) or L2 (max). If the transition has been made, the light source has a predetermined period of time in preference to the normal control described above. Holds drive level.

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

  Similarly, APL at time t20 becomes greater than threshold value A2, and the light source control level changes to the level of L2 (max). Once the light source driving condition transits to L2 (max), the light source control data creation unit 14 holds the output in the state of L2 (max) regardless of the change in APL in the predetermined period T2. When the period T2 ends at time t22, normal processing according to the APL change is performed as in the first embodiment.

  In the present embodiment, as described above, once the light source drive level transitions to L1 (min) or L2 (max), the light source control level is not allowed to follow 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, can improve the problem of deterioration of stable lighting performance and life characteristics of the light source, and can enhance the reliability of the light source. Furthermore, there is another advantage in maintaining the output particularly when the light source control level transitions to L1 (min). For example, when the APL frequently changes before and after A1, if the light source control level is not maintained as in the present embodiment, it is a relatively dark scene, and thus a change in light source luminance is easily perceived. This is because human vision is more sensitive to changes in brightness in dark scenes than to changes in brightness in bright scenes, and is more sensitive to changes in brightness. Therefore, preventing frequent fluctuations in brightness before and after A1 of the APL is also effective for improving the quality of the displayed video.

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

  In the present embodiment, the light source control level is maintained for a predetermined period from when the input APL transitions to A1 or lower or A2 or higher. However, the present invention is not limited to this. For example, the actual light source power is minimum or maximum. The light source control level may be maintained for a predetermined period from the beginning of the time, or the light source control level may be maintained for a predetermined period from another timing. Hereinafter, this modification will be described with reference to FIG.

  In this modification, the light source control data creation unit performs a digital processing operation corresponding to a change in the input APL, as shown in the lower diagram of FIG. To do. 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 is the same as that shown in FIG. As shown in the figure below, state transition is made to the level of L1 (min). Once the driving condition of the light source transitions to L1 (min), the output is held in the state of L1 (min) regardless of the change in APL during a predetermined period T1 '. When the period T1 'ends at the time t12, the normal processing corresponding to the APL change is performed as in the first embodiment.

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

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

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

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

  Hereinafter, a specific operation of the histogram creating unit 15 will be described with reference to FIG. In the histogram creating unit 15, the signal level from 0% to 100% is divided in advance into a plurality of luminance levels (four sections H 1 to H 4 in the figure), and each of the divided sections of the input video signal 1 is divided. Is detected for each unit field. The histogram creation result is input to the light source control data creation unit 16.

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

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

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

  In the present embodiment, the light source control data creating unit 16 creates the light source control data based on the value of the histogram distribution in the section H1. However, the present invention is not limited to this. A histogram distribution of the brightness levels of the sections may be used, or a plurality of histogram distributions may be used in combination.

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

  In the present embodiment, it is determined whether the value of the section H1 is smaller or larger than the threshold value HTL, and the light source control level is controlled in two different modes according to the determination result. For example, another threshold value may be added in addition to the threshold value HTL, the condition determination mode may be increased, and the light source control level condition setting may be set to a plurality of modes according to the determination result.

  Although the case of dynamically controlling the light source has been described as the fourth embodiment, the light source control method described in the fourth embodiment can also be applied to the control of the diaphragm and the control of the light control element. Hereinafter, the configuration of the video display apparatus when the light source control method of the present embodiment is applied to the control of the diaphragm and the control of the light control element will be briefly described.

  FIG. 23 is a block diagram illustrating a configuration of a video display device when the light source control method of the fourth embodiment is applied to aperture control. In FIG. 23, the video display apparatus includes an APL detection unit 2, a histogram creation unit 15, an aperture control data creation unit 25, an aperture drive circuit 20, a light source drive circuit 5, a light source 6, an optical system 17, A display element 8, a video signal processing circuit 9, a display element driver 10, a microcomputer 11, and a timer 12 are provided. The optical system 17 includes a stop 18. In FIG. 23, the same components as those in FIG. 7 or FIG. The aperture control data creation unit 25 creates aperture control data based on the APL detection result and the histogram creation result, similarly to the light source control data creation unit 16 shown in FIG. As a result, even if there is a particularly bright part in a dark scene and it is not possible to determine that the scene is dark from the APL detection result, it is determined that the scene is dark. Therefore, it is possible to prevent black float.

  FIG. 24 is a block diagram illustrating a configuration of an image display device when the light source control method according to the fourth embodiment is applied to control of a light control element. 24, the video display device includes an APL detection unit 2, a histogram creation unit 15, a dimming element control data creation unit 26, a dimming element driving circuit 23, a light source driving circuit 5, a light source 6, and a dimming element. An optical element 21, an optical system 7, a display element 8, a video signal processing circuit 9, a display element driving unit 10, a microcomputer 11, and a timer 12 are provided. In FIG. 24, the same components as those in FIG. 10 or FIG. The dimming element control data creation unit 26 creates dimming element control data based on the APL detection result and the histogram creation result, similarly to the light source control data creation unit 16 shown in FIG. As a result, even if there is a particularly bright part in a dark scene and it is not possible to determine that the scene is dark from the APL detection result, it is determined that the scene is dark. Therefore, it is possible to prevent black float.

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

  FIG. 25 is a block diagram illustrating a configuration of a video display device when the light source control method according to the fourth embodiment is applied to light source and aperture control. In FIG. 25, the video display device includes an APL detection unit 2, a histogram creation unit 15, an aperture control data creation unit 25, an aperture drive circuit 20, a light source control data creation unit 16, an LPF 4, and a light source drive circuit 5. A light source 6, an optical system 17, a display element 8, a video signal processing circuit 9, a display element driving unit 10, a microcomputer 11, and a timer 12. The optical system 17 includes a stop 18. Note that the same reference numerals in FIG. 25 denote the same components as those in FIG. 21 or FIG. As a result, even if there is a particularly bright part in a dark scene and it is not possible to determine that the scene is dark from the APL detection result, it is determined that the scene is dark. Therefore, it is possible to prevent black float.

  FIG. 26 is a block diagram illustrating a configuration of an image display device when the light source control method according to the fourth embodiment is applied to control of a light source and a dimming element. In FIG. 26, the video display device includes an APL detection unit 2, a histogram creation unit 15, a dimming element control data creation unit 26, a dimming element drive circuit 23, a light source control data creation unit 16, an LPF 4, The light source drive circuit 5, the light source 6, the light control element 21, the optical system 7, the display element 8, the video signal processing circuit 9, the display element drive part 10, the microcomputer 11, and the timer 12 are provided. In FIG. 26, the same components as those in FIG. 21 or FIG. As a result, even if there is a particularly bright part in a dark scene and it is not possible to determine that the scene is dark from the APL detection result, it is determined that the scene is dark. Therefore, it is possible to prevent black float.

  FIG. 27 is a block diagram illustrating a configuration of a video display device when the light source control method according to the fourth embodiment is applied to control of a light source, a diaphragm, and a light control element. 27, the video display device includes an APL detection unit 2, a histogram creation unit 15, an aperture control data creation unit 25, an aperture drive circuit 20, a dimming element control data creation unit 26, and a dimming element drive circuit. 23, the light source control data creation unit 16, the LPF 4, the light source drive circuit 5, the light source 6, the light control element 21, the optical system 17, the display element 8, the video signal processing circuit 9, and the display element drive. A unit 10, a microcomputer 11, and a timer 12 are provided. The optical system 17 includes a stop 18. In FIG. 27, the same components as those in FIG. 21, FIG. 23, or FIG. As a result, even if there is a particularly bright part in a dark scene and it is not possible to determine that the scene is dark from the APL detection result, it is determined that the scene is dark. Therefore, it is possible to prevent black float.

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

1 is a block diagram illustrating a configuration of a video display device according to a first embodiment of the present invention. It is a figure showing one method of light source luminance control. It is a figure which shows the method of the light source luminance control in 1st Embodiment. It is a figure which shows the specific example of the signal processing in 1st Embodiment. It is a figure which shows the mode of the signal processing operation | movement in 1st Embodiment. It is a figure which shows the modification of the signal processing in 1st Embodiment. It is a block diagram which shows the structural example of the video display apparatus at the time of applying the control method of the light source in 1st Embodiment to aperture control. It is a figure which shows the control method of an aperture when the control method of the light source in 1st Embodiment is applied to control of an aperture. It is a figure which shows the specific example of the signal processing at the time of applying the control method of the light source in 1st Embodiment to control of an aperture stop. It is a block diagram which shows the structure of the video display apparatus at the time of applying the control method of the light source in 1st Embodiment to control of a light control element. It is a block diagram which shows the other structure of the video display apparatus at the time of applying the control method of the light source in 1st Embodiment to control of a light control element. It is a figure which shows the control method of the light control element at the time of applying the control method of the light source in 1st Embodiment to control of the light control element. It is a figure which shows the specific example of the signal processing at the time of applying the control method of the light source in 1st Embodiment to control of a light control element. It is a block diagram which shows the structure of the video display apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the specific example of the signal processing in 2nd Embodiment. It is a figure which shows the specific example of the signal processing at the time of applying the control method of the light source in 2nd Embodiment to control of an aperture stop. It is a figure which shows the specific example of the signal processing at the time of applying the control method of the light source in 2nd Embodiment to control of a light control element. It is a block diagram which shows the structure of the video display apparatus which concerns on the 3rd Embodiment of this invention. It is a figure which shows the specific example of the signal processing in 3rd Embodiment. It is a figure which shows the modification of the signal processing in 3rd Embodiment. It is a block diagram which shows the structure of the video display apparatus which concerns on the 4th Embodiment of this invention. FIG. 6 is a diagram for explaining the operation of a histogram creation unit 15. It is a block diagram which shows the structure of the video display apparatus at the time of applying the control method of the light source in 4th Embodiment to control of an aperture stop. It is a block diagram which shows the structure of the video display apparatus at the time of applying the control method of the light source in 4th Embodiment to control of a light control element. It is a block diagram which shows the structure of the video display apparatus at the time of applying the control method of the light source in 4th Embodiment to control of a light source and an aperture_diaphragm | restriction. It is a block diagram which shows the structure of the video display apparatus at the time of applying the control method of the light source in 4th Embodiment to control of a light source and a light control element. It is a block diagram which shows the structure of the video display apparatus at the time of applying the control method of the light source in 4th Embodiment to control of a light source, an aperture stop, and a light control element.

Explanation of symbols

1 Video signal 2 APL detection unit 3 Light source control data creation unit 4 LPF
DESCRIPTION OF SYMBOLS 5 Light source drive circuit 6 Light source 7 Optical system 8 Display element 9 Image | video signal processing circuit 10 Display element drive part 11 Microcomputer 12 Timer 13 Light source control data creation part 14 Light source control data creation part 15 Histogram creation part 16 Light source control data creation part 17 Optical System 18 Diaphragm 19 Diaphragm control data creation unit 20 Diaphragm drive circuit 21 Dimming element 22 Dimming element control data creation part 23 Dimming element drive circuit 24 Optical system 25 Diaphragm control data creation part 26 Dimming element control data creation part

Claims (8)

An image display device that displays an image by irradiating light from a light source to a single or a plurality of transmissive or reflective display elements having light modulation action,
A histogram creating means for dividing the brightness level of the input video signal into a plurality of brightness level sections and detecting a histogram distribution for each brightness level section;
Light quantity control data creating means for creating light quantity control data for controlling the light quantity irradiated to the display element based on the histogram distribution for each of the divided sections detected by the histogram creating means;
A light amount control means for controlling the amount of light applied to the display element based on the light amount control data,
The light amount control data generating means during the detected histogram distribution of the split segment each in the histogram creating means is in a predetermined distribution state, the amount of light irradiated to the display element in accordance with the predetermined distribution state Constant at a given level,
While the histogram distribution for each of the divided sections is not in the predetermined distribution state , light amount control data is created such that the amount of light applied to the display element changes according to the average luminance level of the input video signal. A video display device. The light quantity control data creation means irradiates the display element while a histogram distribution of at least one brightness level of the plurality of brightness level categories detected by the histogram creation means is larger than a predetermined threshold value. wherein the amount of light to create a light amount control data such that the constant at the predetermined level, the image display device according to claim 1. The light amount control data generating means, while the detected histogram distribution in the histogram creation unit, video scene according to the input video signal is in a distribution state as determined to be dark scene, the display device wherein the amount of light radiated to create a light amount control data such that the constant predetermined minimum level, the image display device according to claim 1. The light amount control data generating means, while the detected histogram distribution in the histogram creating means is in distribution, such as a video scene according to the input video signal is judged to be bright scene, the display device wherein the amount of light radiated to create a light amount control data such that the constant predetermined maximum level, the image display device according to claim 1. An image display method for displaying an image by irradiating light from a light source to a single or a plurality of transmissive or reflective light-modulating display elements,
A histogram creating step for dividing the luminance level of the input video signal into a plurality of luminance level segments and detecting a histogram distribution for each luminance level segment;
Based on the detected histogram distribution of the split segment each Oite the histogram creation step, the light amount control data generating step of generating a light amount control data for controlling the amount of light applied to the display element,
A light amount control step for controlling the amount of light applied to the display element based on the light amount control data,
In the light amount control data production step, while the histogram distribution for each detected the divided segments in said histogram generating step is in the predetermined distribution state, the amount of light irradiated to the display element according to the predetermined distribution state Constant at a given level,
While the histogram distribution for each of the divided sections is not in the predetermined distribution state , light amount control data is created such that the amount of light applied to the display element changes according to the average luminance level of the input video signal. A video display method. In the light amount control data production step, during histogram distribution of at least one of luminance levels of the detected plurality of luminance levels division in the histogram creation step is greater than a predetermined threshold, the display device characterized by creating a light amount control data such as the amount of light to be irradiated is constant at the predetermined level, the image display method according to claim 5. In the light amount control data production step, while the histogram created detected histogram distribution in step, the video scene according to the input video signal is in a distribution state as determined to be dark scene, the display element amount of light is irradiated, characterized in that to create the light amount control data such that the constant predetermined minimum level, the display method of claim 5. In the light amount control data production step, while the histogram created detected histogram distribution in step is in distribution, such as a video scene according to the input video signal is judged to be bright scene, the display element amount of light is irradiated, characterized in that to create the light amount control data such that the constant predetermined maximum level, the image display method according to claim 5.

Images