JP4020047B2 - Video display method and video display device - Google Patents

Description

  The present invention relates to a video display method and a video display device, and in particular, in a projection-type display device, a video display method and a video that do not cause flickering or white crushing of an image (also referred to as “video” in the present specification). The present invention relates to a display device.

  In recent years, the development of information devices has been remarkable, and the demand for high-resolution, low power consumption and thin display devices has been increasing, and research and development have been promoted. Among them, the liquid crystal display device can change the optical characteristics by electrically controlling the alignment of liquid crystal molecules, and is expected as a display device that can meet the above needs. As one form of such a liquid crystal display device, a light valve (liquid crystal light valve, micromirror array device, etc.) and a dimming element that changes the amount of light incident on the light valve are used and emitted from the optical system. 2. Description of the Related Art Projection-type image display devices (such as liquid crystal projectors) that project an image on a screen through a projection lens are known.

  The projection-type image display method using a light valve and a light control element can improve the contrast feeling remarkably by making full use of the display gradation range (dynamic range) inherent to the light valve. It is a display method. However, in general images such as movies and televisions, the brightness of the screen changes in various ways, and it is difficult to make the dimming state completely follow the change in brightness. There were problems such as causing collapse and the image appearing to flicker.

  As a prior art related to the present invention, a method for extending the dynamic range of a projection display device is disclosed (for example, see Patent Document 1).

In this prior art, the light output intensity of a lamp (metal halide lamp) serving as a light source is changed in order to change the amount of light incident on the light modulator (light valve) in accordance with the video signal. However, even in the method disclosed in this prior art, it is difficult to completely follow the dimming state to the brightness of the screen.
Japanese Patent Laid-Open No. 3-179886

  The present invention has been made to solve such a problem, and an object of the present invention is to provide an image display that does not cause white crushing or flickering in a projection-type image display device using a light valve and a light control element. It is to provide a method and an image display device.

The video display method of the present invention is a video display method in a video display device in which an image on a light valve is changed according to an input image signal, and a light amount incident on the light valve is changed by a dimming element, A step of temporarily storing the input image signal for a predetermined storage time or a predetermined number of frames, a step of detecting a scene change of the input image signal to be stored, and a step of the dimming element according to the detected scene Determining a dimming parameter for controlling the amount of light; storing information on the dimming parameter together with a frame number at the start of the scene; and transmitting the accumulated image signal to the light valve as a delayed image signal. And generating a dimming control signal for controlling the dimming element based on the dimming parameter and reproducing In synchronization with the image signal, characterized by a step of controlling the light quantity of the light control element.
According to the video display method of the present invention configured as described above , the input image signal is temporarily stored in a mass storage device such as a RAM or a hard disk for a predetermined storage time (or the number of frames). Further, a scene change is detected from the input image signal, and a dimming parameter corresponding to the scene of the accumulated image signal is determined. Then, when reproducing the image signal stored in the mass storage device or the like, the dimming control signal generated based on the dimming parameter is output in synchronization with the image signal, and the light quantity of the dimming element is controlled.
As a result, the dimming parameter corresponding to the scene can be determined in advance, and flickering, white crushing, etc. can be eliminated, and the image can be reproduced without giving the viewer unnaturalness or a sense of discomfort.
Further, according to the video display method of the present invention having the above-described configuration, when the dimming parameter is determined according to the detected scene and stored in the memory, the scene start frame number (frame number of the image signal) is stored. To do. When the image signal is reproduced, the image signal and the dimming control signal (the light amount control signal of the dimming element generated based on the dimming parameter) are synchronized based on the frame number at the start of the scene.
Thus, the image signal and the dimming control signal (control signal generated based on the dimming parameter) can be reproduced in a simple and reliable manner.

The video display method of the present invention is a video display method in a video display device in which an image on a light valve is changed in accordance with an input image signal, and a light amount incident on the light valve is changed by a dimming element. A step of temporarily storing the input image signal for a predetermined storage time or a predetermined number of frames, a step of detecting a scene change of the stored input image signal, and the dimming according to the detected scene. Determining a dimming parameter for controlling the amount of light of the element; transmitting the accumulated image signal to the light valve as a delayed image signal for reproduction; and the dimming element based on the dimming parameter Generating a dimming control signal for controlling the light amount, controlling the light amount of the dimming element in synchronization with the image signal to be reproduced, and the storage time If no scene change is detected in the image signal, a step of determining a dimming parameter based on the image signal within the accumulation time, a scene change is not detected in the image signal within the accumulation time, and When a frame that does not match the determined dimming parameter is detected, a new dimming parameter corresponding to the detected frame is determined, and the dimming parameter used for reproducing the image signal is determined. And stepwise changing from a current dimming parameter to a new dimming parameter.
According to the video display method of the present invention configured as described above, an input image signal is temporarily stored in a large-capacity storage device such as a RAM or a hard disk for a predetermined storage time (or the number of frames). Further, a scene change is detected from the input image signal, and a dimming parameter corresponding to the scene of the accumulated image signal is determined. Then, when reproducing the image signal stored in the mass storage device or the like, the dimming control signal generated based on the dimming parameter is output in synchronization with the image signal, and the light quantity of the dimming element is controlled.
As a result, the dimming parameter corresponding to the scene can be determined in advance, and flickering, white crushing, etc. can be eliminated, and the image can be reproduced without giving the viewer unnaturalness or a sense of discomfort.
Further, according to the video display method of the present invention having the above-described configuration, when a frame (scene) with a small degree of change is continuous and no scene change is detected in the image signal within the accumulation time, the image within the accumulation time is displayed. A new dimming parameter is determined based on the signal. In addition, when a scene change is not detected and a scene that does not match the determined dimming parameter appears, a new dimming parameter for the new scene is determined and used to reproduce the image signal. The dimming parameter to be changed is gradually changed from the current dimming parameter to the new dimming parameter.
As a result, frames (scenes) with a small degree of change are continuous, and in the actual image, although the brightness gradation and the like are greatly changed, the dimming parameter is not updated, and the image is not updated by the viewer. It is possible to prevent visuals from becoming unnatural or uncomfortable. In addition, it is possible to prevent the dimming parameter from changing suddenly and causing the viewer's vision to feel unnatural or uncomfortable.

The video display device of the present invention is a video display device that changes an image on a light valve according to an input image signal, and changes a light amount incident on the light valve by a dimming element. The image accumulation means for temporarily accumulating the signal for a predetermined accumulation time or a predetermined number of frames, the scene change detection means for detecting a scene change of the accumulated input image signal, and the adjustment according to the detected scene. A dimming parameter determining means for determining a dimming parameter for controlling the light amount of the optical element, a means for storing information on the dimming parameter together with a frame number at the start of the scene, and the accumulated image signal are delayed. Image reproduction means for transmitting the image signal to the light valve for reproduction, and a dimming control signal for controlling the dimming element based on the dimming parameter In synchronization with the image signal to the reproduction, and having a dimming control section for controlling the light quantity of the light control element.
  According to the video display device of the present invention configured as described above, the input image signal is temporarily stored in a mass storage device such as a RAM or a hard disk for a predetermined storage time (or the number of frames). Further, a scene change is detected from the input image signal, and a dimming parameter corresponding to the scene of the accumulated image signal is determined. Then, when reproducing the image signal stored in the mass storage device or the like, the dimming control signal generated based on the dimming parameter is output in synchronization with the image signal, and the light quantity of the dimming element is controlled.
  As a result, the dimming parameter corresponding to the scene can be determined in advance, flickering and white crushing can be eliminated, and the image can be reproduced without causing the viewer to feel unnatural or uncomfortable.
Further, according to the video display device of the present invention having the above configuration, in such a configuration, when the dimming parameter is determined according to the detected scene and stored in the memory, the frame number ( Together with the frame number of the image signal). When the image signal is reproduced, the image signal and the dimming control signal (the light amount control signal of the dimming element generated based on the dimming parameter) are synchronized based on the frame number at the start of the scene.
  Thus, the image signal and the dimming control signal (control signal generated based on the dimming parameter) can be reproduced in a simple and reliable manner.

The video display device of the present invention is a video display device that changes an image on a light valve according to an input image signal and changes a light amount incident on the light valve by a dimming element. An image storage means for temporarily storing the signal for a predetermined storage time or a predetermined number of frames, a scene change detection means for detecting a scene change of the stored input image signal, and the adjustment according to the detected scene. A dimming parameter determining means for determining a dimming parameter for controlling the amount of light of the optical element;
  Image reproduction means for transmitting the accumulated image signal as a delayed image signal to the light valve for reproduction, and a dimming control signal for controlling the dimming element based on the dimming parameter, and generating the reproduction A dimming control means for controlling the amount of light of the dimming element in synchronism with the image signal, and when no scene change is detected in the image signal within the accumulation time, the image signal within the accumulation time is used as a basis. Means for determining a dimming parameter, and when a scene change is not detected in the image signal within the accumulation time and a frame that does not match the determined dimming parameter is detected. A new dimming parameter corresponding to the frame is determined, and a dimming parameter used for reproducing the image signal is gradually changed from the current dimming parameter to the new dimming parameter. And wherein the Rukoto.
  According to the video display device of the present invention configured as described above, the input image signal is temporarily stored in a mass storage device such as a RAM or a hard disk for a predetermined storage time (or the number of frames). Further, a scene change is detected from the input image signal, and a dimming parameter corresponding to the scene of the accumulated image signal is determined. Then, when reproducing the image signal stored in the mass storage device or the like, the dimming control signal generated based on the dimming parameter is output in synchronization with the image signal, and the light quantity of the dimming element is controlled.
  As a result, the dimming parameter corresponding to the scene can be determined in advance, flickering and white crushing can be eliminated, and the image can be reproduced without causing the viewer to feel unnatural or uncomfortable.
Further, according to the video display device of the present invention having the above configuration, when a frame (scene) with a small degree of change is continuous and no scene change is detected in the image signal within the accumulation time, the image within the accumulation time is displayed. A new dimming parameter is determined based on the signal. In addition, when a scene change is not detected and a scene that does not match the determined dimming parameter appears, a new dimming parameter for the new scene is determined and used to reproduce the image signal. The dimming parameter to be changed is gradually changed from the current dimming parameter to the new dimming parameter.
As a result, frames (scenes) with a small degree of change are continuous, and in the actual image, although the brightness gradation and the like are greatly changed, the dimming parameter is not updated, and the image is not updated by the viewer. It is possible to prevent visuals from becoming unnatural or uncomfortable. In addition, it is possible to prevent the dimming parameter from changing suddenly and causing the viewer's vision to feel unnatural or uncomfortable.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  In a projection-type image display device that changes an image on a light valve (also referred to as “image” in this specification) and a light amount incident on the light valve in accordance with an input image signal, Since the amount of light cannot be followed completely, the image may become unnatural.

  Therefore, the present invention temporarily stores an image in a large-capacity storage device such as a RAM or a hard disk, and applies a dimming control parameter determined in advance when reproducing the image, thereby synchronizing the video and the dimming.

First, a projection type video display apparatus to which the present invention is applied will be described.
FIG. 1 is a schematic configuration diagram showing this projection-type image display device. A transmission type light valve (liquid crystal light valve or the like) is provided for each of R (red), G (green), and B (blue) different colors. It is an example of a three-plate projection type color image display device provided. In the figure, reference numerals 10R, 10G, and 10B denote light sources, 13R, 13G, and 13B light control elements, 20R, 20G, and 20B light valves, 30 a cross dichroic prism, 40 a projection lens, and 41 a screen.

  The light sources 10R, 10G, and 10B are color light sources that can emit red light, green light, and blue light, respectively. The light sources 10R, 10G, and 10B are light emitting diodes (LEDs), organic electroluminescence elements (organic EL elements), and inorganic light sources. A light emitter 11 such as an electroluminescence element (inorganic EL element) and a reflector 12 that reflects the output light of the light emitter 11 are configured. The light valves 20R, 20G, and 20B are provided corresponding to the light sources 10R, 10G, and 10B, respectively, and light modulation is possible for each light source.

  In addition, the light control elements 13R, 13G, and 13B each include a liquid crystal layer held between a pair of glass substrates (light transmissive substrates), and are roughly configured by polarizing plates stacked on both sides of the liquid crystal panel. As the liquid crystal sandwiched between the pair of glass substrates, a liquid crystal with a high response speed such as FLC is used.

  When the dimming elements 13R, 13G, and 13B receive a drive signal from the dimming element driver and apply a voltage to the light transmissive electrode, the transmittance is changed by changing the time distribution between non-voltage application and voltage application between frames. The time distribution of 100% and transmittance 0% can be freely changed, and the light control elements 13R, 13G, and 13B can be changed by changing the time distribution of transmittance 100% and transmittance 0% in this way. The amount of light emitted from one frame to the next can be changed. Therefore, if the screen is bright, the amount of light between one frame can be increased by increasing the time distribution of 100% transmittance and reducing the time distribution of 0% transmittance in one frame. To be more.

  In the case of a dark screen, the amount of light emitted from the light emitter 11 is reduced by reducing the time distribution of 100% transmittance in one frame and increasing the time distribution of 0% transmittance to reduce the amount of light. The amount of light emitted between frames (the amount of light emitted from the light emitter 11 during one frame) is adjusted by the light control elements 13R, 13G, and 13B.

  Further, the cross dichroic prism 30 has a structure in which four right-angle prisms are bonded together, and a light reflecting film (not shown) made of a dielectric multilayer film is formed in a cross shape on the bonded surfaces 30a and 30b. . Specifically, a light reflecting film that reflects red image light formed by the light valve 20R and transmits green and blue image light formed by the light valves 20G and 20B is provided on the bonding surface 30a. It has been. On the other hand, a light reflecting film that reflects blue image light formed by the light valve 20B and transmits red and green image light formed by the light valves 20R and 20G is provided on the bonding surface 30b. . The light reflecting films combine the image lights of the respective colors formed by the liquid crystal light valves 20R to 20B to form light representing a color image. The synthesized light is projected on the screen 41 by the projection lens 40 which is a projection optical system, and an enlarged image is displayed.

Next, the circuit configuration of the video display device of this embodiment will be described.
FIG. 2 is a diagram showing a circuit configuration example of a video display device according to the present invention. Reference numeral 101 denotes an image analysis unit, 102 denotes an image processing unit, 103 denotes a light valve driver, 104 denotes a dimming element driver, and 13 denotes dimming. An element (such as the dimming element 13R in FIG. 1) and 20 indicate a light valve (such as the light valve 20R in FIG. 1).

  The image analysis unit 101 temporarily stores the input image signal a1 in a large-capacity storage device such as a RAM or a hard disk, and outputs the delayed image signal a2 to the image processing unit 102. Further, a scene change is detected from the stored image signal a1, and a dimming parameter corresponding to the scene is determined. In addition, when the image signal is reproduced, the dimming control signal a3 generated based on the dimming control parameter is synchronized with the reproduced image signal in order to adapt the image signal to be reproduced and the dimming amount of the dimming element 13. Then, the light is output to the dimming element driver 104.

  The image processing unit 102 sets the light amount of the light valve 20 (see FIG. 1) and the expansion amount of the video signal of each color based on the image signal a2 and the dimming control signal a3 received from the image analysis unit 101. Output to the driver 103.

  The light valve driver 103 drives the light valve 20 by a drive signal from the image processing unit 102. The dimming element driver 104 drives the dimming element (see FIG. 1) 13 based on the dimming control signal a3 from the image processing unit 102. The light valve driver 103 and the dimming element driver 104 have a function of driving for different colors of R (red), G (green), and B (blue).

  FIG. 3 is a diagram illustrating a circuit configuration example of the image analysis unit 101. The image analysis unit 101 temporarily stores a display image and performs a process of adapting a dimming parameter when reproducing the image to the display image. . In FIG. 3, reference numeral 201 denotes a storage device (image storage means), 202 denotes a video storage / playback section (image playback means), 203 denotes a histogram creation section, 204 denotes a histogram analysis section, and 205 denotes a scene change detection section (scene change detection). Means), 206 is a dimming parameter determining unit (dimming parameter determining unit), 207 is a scene storage / reading unit (dimming control unit), and 208 is a memory.

  The storage device 201 is a large-capacity storage device such as a RAM or a hard disk, and an image for determining a dimming parameter is temporarily stored for a predetermined storage time (or a predetermined number of frames).

  The video storage / reproduction device (image reproduction means) 202 temporarily stores (accumulates) the received image signal in the storage device 201, delays the image signal stored in the storage device 201 by a predetermined time, and delays the delayed image signal. As a2, it outputs to the light valve 20 and reproduces an image.

  The histogram creation unit 203 creates an appearance frequency distribution (histogram) for each number of gradations of pixel data included in a signal per unit time (one frame period) from the input image signal a1. FIG. 5 shows an example of the created histogram.

  The histogram analysis unit 204 analyzes the histogram created by the histogram creation unit 203, and detects, for example, video brightness based on the histogram.

  The scene change detection unit (scene change detection means) 205 detects whether there is a scene change in the image based on the histogram analysis result data received from the histogram analysis unit 204. In the example shown in FIG. 3, the histogram shape correlation (shape similarity) is examined for each frame, and a frame (scene) whose period of change in the histogram shape is equal to or less than a certain amount of change is detected as one scene. To do.

  Accordingly, a single scene may include a plurality of frames. For example, as shown in FIG. 5, a case where the histogram changes greatly is detected as a scene change, and a scene E is obtained from the scene A. The length (time) differs for each scene.

  Also, a dimming parameter determination unit (a dimming parameter determination unit) 206 determines a dimming parameter corresponding to the scene detected by the scene change detection unit 205. Also, the determined dimming parameter is transmitted together with the scene start frame number (image signal frame number) to the scene storage / readout unit 207.

The scene storage / reading unit (dimming control means) 207 receives the scene start frame number and the dimming parameter information of the scene from the dimming parameter determination unit 206 and stores them in the memory 208. The scene storage / reading unit 207 also reads out the scene start frame number and dimming parameters from the memory 208, and generates and outputs a dimming control signal a3 for controlling the light amount of the dimming element 13. The dimming control signal a3 is performed in synchronization based on the image signal (delayed image signal) a2 output from the video storage / playback unit 202 and the frame number at the start of the scene.
Further, as described above, the memory 208 stores the frame number of the scene start and the dimming parameter corresponding to the scene (or the dimming control signal generated based on the dimming parameter).

Note that various methods can be used as a scene change detection method in the scene change detection unit 205. For example, the following method can be used.
(1) When the maximum value of brightness (brightness gradation) in a frame is equal to or less than a predetermined constant change amount, a frame (scene) in that period is set as one scene. In this method, a scene change can be detected most easily (with the least computation load) and at high speed.
(2) When the average value of the brightness (brightness gradation) in the frame is equal to or less than a predetermined constant change amount, the frame (scene) during that period is set as one scene. In this method, a scene change can be detected in a natural manner according to the average content (brightness) of the image.
(3) The correlation of the histogram shape (similarity of the shape) is examined for each frame, and a frame (scene) having a period of a certain amount of change or less is defined as one scene. In this method, a scene change can be detected in a highly reliable manner reflecting the contents of the image.

Various methods can also be used as the method for determining the light control parameter in the light control parameter determination unit 206. For example, the following method can be used.
(1) A dimming parameter is determined based on the brightest gradation in the scene. In this method, the dimming parameter can be determined most easily (with the least calculation load).
(2) The dimming parameter is determined based on the average brightness gradation in the scene. In this method, the dimming parameter can be determined in a natural manner according to the average content (brightness) of the image.
(3) The dimming parameter is determined based on the histogram in the scene. In this method, the dimming parameter can be determined with high reliability reflecting the contents of the image.

  FIG. 4 is a diagram showing processing when a scene change is not found within the image accumulation time. As shown in FIG. 4A, when there is no scene change within the accumulation time, The dimming parameter is determined within the period. Also, as shown in FIG. 4B, when a scene inappropriate for the determined parameter (for example, a scene brighter than the scene for which the parameter is determined) appears, the dimming parameter gradually changes in the new scene. Like that.

  As described above, when frames (scenes) with a small degree of change continue and no scene change is detected in the image signal within the accumulation time, a new dimming parameter is determined based on the image signal within the accumulation time. To do. In addition, when a scene change is not detected and a scene that does not match the determined dimming parameter appears, a new dimming parameter for the new scene is determined and used to reproduce the image signal. The dimming parameter to be changed is gradually changed from the current dimming parameter to the new dimming parameter.

  As a result, frames (scenes) with a small degree of change are continuous, and in the actual image, although the brightness gradation and the like are greatly changed, the dimming parameter is not updated, and the image is not updated by the viewer. It is possible to prevent visuals from becoming unnatural or uncomfortable. In addition, it is possible to prevent the dimming parameter from changing suddenly and causing the viewer's vision to feel unnatural or uncomfortable.

  As described above, the embodiment of the present invention has been described, but the functions of the image analysis unit 101 and the image processing unit 102 in the video display apparatus shown in FIG. 2 may be achieved by dedicated hardware. Also, a program for realizing the functions of the image analysis unit 101 and the image processing unit 102 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed. The image analysis unit 101 and the image processing unit 102 in the video display apparatus shown in FIG. The “computer system” here includes an OS and hardware such as peripheral devices.

The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. It also includes a device (transmission medium or transmission wave) and a device that holds a program for a certain period of time, such as a volatile memory inside a computer system serving as a server or client in that case.
The program may be for realizing a part of the functions described above, and further, a program that can realize the functions described above in combination with a program already recorded in a computer system, a so-called difference file (difference). Program).

  Although the embodiments of the present invention have been described above, the video display device of the present invention is not limited to the above illustrated examples, and various modifications can be made without departing from the scope of the present invention. Of course.

  In the present invention, the dimming parameter corresponding to the scene can be determined in advance, and there is an effect of eliminating flickering and white crushing and reproducing the image without giving the viewer unnaturalness and uncomfortable feeling. The present invention can be applied to a video display device using a light valve and a light control element, and a video display method.

The schematic block diagram which shows a projection type display apparatus. The figure which shows the circuit structural example of the video display apparatus by this invention. The figure which shows the circuit structural example of an image analysis part. The figure which shows a process when a scene change is not found within the accumulation time of an image. The figure which shows the example of a histogram.

Explanation of symbols

  13, 13R, 13G, 13B ... Light control element, 20, 20R, 20G, 20B ... Light valve, 101 ... Image analysis part, 102 ... Image processing part, 103 ... Light valve driver, 104 ... Light control element driver, 201 ... Storage device 202 ... Video storage / reproduction unit 203 ... Histogram creation unit 204 ... Histogram analysis unit 205 ... Scene change detection unit 206 ... Dimming parameter determination unit 207 ... Scene storage / read unit 208 ... memory

Claims (4)

In accordance with an input image signal, the image on the light valve is changed, and the amount of light incident on the light valve is changed by a dimming element.
Temporarily storing the input image signal for a predetermined storage time or a predetermined number of frames;
Detecting a scene change in the accumulated input image signal;
Determining a dimming parameter for controlling the amount of light of the dimming element according to the detected scene;
Storing the information of the dimming parameter together with the frame number of the scene start;
Transmitting the accumulated image signal to the light valve as a delayed image signal for reproduction; and
Generating a dimming control signal for controlling the dimming element based on the dimming parameter, and controlling the light amount of the dimming element in synchronization with the image signal to be reproduced;
A video display method characterized by comprising: In accordance with an input image signal, the image on the light valve is changed, and the amount of light incident on the light valve is changed by a dimming element.
  Temporarily storing the input image signal for a predetermined storage time or a predetermined number of frames;
  Detecting a scene change in the accumulated input image signal;
  Determining a dimming parameter for controlling the amount of light of the dimming element according to the detected scene;
  Transmitting the accumulated image signal to the light valve as a delayed image signal for reproduction; and
  Generating a dimming control signal for controlling the dimming element based on the dimming parameter, and controlling the light amount of the dimming element in synchronization with the image signal to be reproduced;
When a scene change is not detected in the image signal within the accumulation time, determining a dimming parameter based on the image signal within the accumulation time;
When a scene change is not detected in the image signal within the accumulation time and a frame that is incompatible with the determined dimming parameter is detected, a new dimming parameter corresponding to the detected frame is detected. Changing the dimming parameter used for reproducing the image signal step by step from the current dimming parameter to a new dimming parameter;
A video display method characterized by comprising: An image display device that changes an image on a light valve according to an input image signal and changes a light amount incident on the light valve by a dimming element,
  Image storage means for temporarily storing the input image signal for a predetermined storage time or a predetermined number of frames;
  A scene change detecting means for detecting a scene change of the accumulated input image signal;
  A dimming parameter determining means for determining a dimming parameter for controlling the amount of light of the dimming element according to the detected scene;
  Means for storing the dimming parameter information together with the frame number of the scene start;
  Image reproduction means for transmitting the accumulated image signal to the light valve as a delayed image signal for reproduction;
  A dimming control means for generating a dimming control signal for controlling the dimming element based on the dimming parameter, and controlling the light amount of the dimming element in synchronization with the image signal to be reproduced;
  A video display device comprising: An image display device that changes an image on a light valve according to an input image signal and changes a light amount incident on the light valve by a dimming element,
  Image storage means for temporarily storing the input image signal for a predetermined storage time or a predetermined number of frames;
  A scene change detecting means for detecting a scene change of the accumulated input image signal;
  A dimming parameter determining means for determining a dimming parameter for controlling the amount of light of the dimming element according to the detected scene;
  Image reproduction means for transmitting the accumulated image signal to the light valve as a delayed image signal for reproduction;
A dimming control means for generating a dimming control signal for controlling the dimming element based on the dimming parameter, and controlling the light amount of the dimming element in synchronization with the image signal to be reproduced;
  When no scene change is detected in the image signal within the accumulation time, means for determining a dimming parameter based on the image signal within the accumulation time;
  When a scene change is not detected in the image signal within the accumulation time and a frame that is incompatible with the determined dimming parameter is detected, a new dimming parameter corresponding to the detected frame is detected. Means for gradually changing the dimming parameter used for reproducing the image signal from the current dimming parameter to a new dimming parameter;
A video display device comprising:

Images