JP2011203290A - Image display device and method of controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce collapse of gradation of a display image due to processing other than gamma curve correction.SOLUTION: An image display device has: a memory means 13 having a first access mode of writing/reading image data frame by frame and a second access mode of writing/reading the image data sub-frame area by sub-frame area; a compression means 11 for compressing the gradation of input image data; a restoring means 14 for restoring the compressed image data; and a gamma curve correction means 1. Switching between the first image display mode and the second image display mode with priority given to the gradation of the display image is performed. A control means 1 sets the first access mode in a first image display mode, sets the non-compression/non-restoration output state in a second image display mode, and sets the first access mode when the write capacity of the memory means is large to resolution of input image data determined by a resolution determination means and the second access mode when it is small.

Description

The present invention relates to an image display device such as a projector or a monitor.

  In some cases, a video signal (video data) having a large resolution is input to the image display device. In order to cope with the increased volume of video data, increasing the capacity of the frame buffer provided in the image display device or increasing the access speed to the frame buffer increases the cost. For this reason, a technique for reducing the volume of video data written to the frame buffer by compressing the video data is widely used.

  Although it is desirable in terms of cost to perform compression processing using a simple method such as bit shift, since such compression method is irreversible color (gradation) compression processing, it involves degradation in image quality. . Therefore, it is necessary to limit the case where irreversible color compression processing is applied.

  For example, Patent Document 1 discloses an image display device that switches application / non-application of irreversible color compression processing according to validity / invalidity of keystone adjustment in order to limit the case where irreversible color compression processing is applied. Has been.

JP 2007-72360 A

  By the way, an image display apparatus may be required to have a function capable of correcting the relationship between an input gradation and a displayed output gradation to an appropriate gamma curve in an installation environment. This is because the display image is affected by the installation environment, that is, the illumination spectrum and intensity at the place where the image display device is installed. For example, when the apparatus is installed in a strong illumination environment, the influence of illumination light on the display image differs depending on whether the display image has a low gradation or a high gradation.

  Therefore, a method is adopted in which the user selects an optimum correction curve for the actual installation environment from among the correction curves designed to obtain an appropriate gamma curve in a plurality of installation environments assumed in advance. Can be considered. In this case, the correction of the gamma curve causes the gradation to be crushed, so it is preferable that the gradation is not crushed by a process other than the correction of the gamma curve. In this respect, as disclosed in Patent Document 1, it is effective to limit the application case of the irreversible color compression processing.

  However, in the apparatus disclosed in Patent Document 1, irreversible color compression processing by bit shift is always applied when the size of the input video data (video data amount) is larger than the size of the frame buffer (buffer capacity). Furthermore, even if the video data amount is smaller than the buffer capacity, if the keystone adjustment amount is increased, irreversible color compression processing by bit shift is applied. In such a situation, the gradation that can be displayed is greatly reduced, so that correction close to an appropriate gamma curve cannot be performed.

  The present invention provides an image display apparatus capable of reducing the collapse of the gradation of a display image due to processing other than correction of a gamma curve.

  An image display apparatus according to an aspect of the present invention sequentially writes and reads video data in a first access mode in which video data is sequentially written and read in every frame and in each subframe area divided smaller than the one frame. A memory means having a second access mode; a compressed output state for outputting compressed video data generated by compressing the gradation of the input video data as video data to be written to the memory means; and the input video data is not compressed A compression means that can be switched to an uncompressed output state that is output as uncompressed video data, a decompressed output state that restores and outputs the compressed video data read from the memory means, and an uncompressed read from the memory means Restoration means that can be switched to a non-restored output state that outputs video data without restoring it, and adjusts the gradation of the displayed video A gamma curve correcting means for correcting a gamma curve for switching, a mode capable of switching between a first video display mode and a second video display mode in which the gradation of the display video is given priority over the first video display mode Selection means, resolution determination means for determining the resolution of the input video data, and control means for controlling access mode setting of the memory means and state switching of the compression means and restoration means. The control means sets the memory means to the first access mode when the first video display mode is set, and turns off the compression and decompression means when the second video display mode is set. When the compression and non-decompression output states are set, and the writing capacity of the memory means is large with respect to the resolution determined by the resolution determination means, the memory means is set to the first access mode, and the memory means is set to the resolution. When the write capacity is small, the memory means is set to the second access mode.

  According to another aspect of the present invention, there is provided a control method comprising: a first access mode in which video data is sequentially written and read out for each frame; and a sequential writing and reading for each subframe area divided smaller than the one frame. A memory means having a second access mode to be read, and a compressed output state for outputting compressed video data generated by compressing the gradation of the input video data and input video data as video data to be written to the memory means Compression means that can be switched to an uncompressed output state that is output as uncompressed video data without compression, a decompressed output state that restores and outputs the compressed video data read from the memory means, and is read from the memory means A restoration means capable of switching to a non-decompression output state in which uncompressed video data is output without being restored, and The gamma curve correcting means for correcting the gamma curve for adjusting the image, and the first video display mode and the second video display mode that prioritizes the gradation of the display video over the first video display mode can be switched. The present invention is applied to an image display device having a mode selection means. The control method includes a step of setting the memory means to the first access mode when the first video display mode is set, and a compression and decompression means when the second video display mode is set. The non-compressed and non-decompressed output states are set, and when the writing capacity of the memory means is larger than the resolution determined by the resolution determining means, the memory means is set to the first access mode, and the memory means is set for the resolution. And a step of setting the memory means to the second access mode when the write capacity is small.

According to the present invention, in the second video display mode that prioritizes gradation, it is possible to reduce the collapse of the gradation of the display image due to processing other than correction of the gamma curve.

1 is a block diagram showing a configuration of an image display apparatus that is an embodiment of the present invention. 6 is a flowchart illustrating the operation of the image display apparatus according to the embodiment.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a configuration of a part related to processing of a video signal (video data) in an image display apparatus which is an embodiment of the present invention. The image display device includes various image display devices such as an image projection device such as a liquid crystal projector and a DLP (Digital Light Processing) projector and a direct-view type liquid crystal monitor.

  The image display apparatus includes an operation mode control unit (gamma curve correction unit, determination unit and control unit) 1, resolution conversion unit 2, image quality adjustment unit 3, resolution determination unit 4, operation unit 5, and image memory processing unit (memory unit, Compression means and decompression means) 10.

  The image memory processing unit 10 includes a compression unit 11, a compression application switch 12, an image memory unit 13, a restoration unit 14, a restoration application switch 15, a route control unit 16, and an address control unit 17, as indicated by dotted lines in the figure. .

  The compression unit 11 generates compressed video data having a size smaller than that of the input video data by compressing the video data (input video data) input as the input video signal. The compression referred to here is irreversible compression processing such as resolution conversion, bit width reduction, and color reduction.

  The compression application switch 12 selects a compression route in which input video data is written to the image memory unit 13 via the compression unit 11, and selects a bypass route that bypasses the compression unit 11 and is written to the image memory unit 13. It is possible to switch to a state to perform. The state where the compression route is selected corresponds to the compressed output state, and the state where the bypass route is selected corresponds to the uncompressed output state. When the input video data passes through the compression unit 11, the output of the compression application switch 12 is compressed video data, and when the input video data bypasses the compression unit 11, the output of the compression application switch 12 is uncompressed video data.

  In the image memory unit 13, the video data (compressed video data or uncompressed video data) output from the compression application switch 12 is written at the address specified by the address control unit 17. The image memory unit 13 outputs video data at an address designated by the address control unit 17 to a restoration unit 14 and a restoration application switch 15 described later.

  The restoration unit 14 restores the video data (compressed video data) compressed by the compression unit 11 to the original size video data (restored video data).

  The restoration application switch 15 selects a restoration route in which the compressed video data read from the image memory unit 13 is output via the restoration unit 14, and a detour route output by bypassing the restoration unit 14. It is possible to switch to the state to be selected. The state where the restoration route is selected corresponds to the restoration output state, and the state where the detour route is selected corresponds to the non-restoration output state. The video data output from the restoration application switch 15 is input to the resolution conversion unit 2.

  The route control unit 16 sets the compression application switch 12 as a compression route and sets the restoration application switch 15 as a restoration route, and a bypass route that sets the compression application switch 12 and the restoration application switch 15 as bypass routes. Switch. Route switching in the route control unit 16 is controlled by the operation mode control unit 1.

  The address control unit 17 controls a writing mode and a reading mode for the image memory unit 13. The write mode includes a first access mode, a second access mode, and a third access mode.

  In the first access mode, video data is sequentially written at different write addresses for each frame. The video data of each frame is held for one vertical synchronization period. In the second access mode, one frame of video data is divided into sub-frame areas each including a plurality of lines (for example, an area that is half of one frame), and is sequentially written to different write addresses for each sub-frame area. The video data of each subframe area is held for one subframe period.

  In the third access mode, new writing to the image memory unit 13 is prohibited, and the frame video data held immediately before switching to the third access mode is held as it is.

  The address control unit 17 appropriately controls the number of write pixels per access to the image memory unit 13 in accordance with the difference in the amount of video data corresponding to the route selected by the compression application switch 12, and sets the number of write pixels. Accordingly, the write address to the image memory unit 13 is designated.

  On the other hand, the read mode has a first access mode and a second access mode respectively corresponding to the first access mode and the second access mode as the write mode. In the first access mode in the read mode, the video data is sequentially read from the image memory unit 13 for each frame, and in the second access mode, the video data is sequentially read for each subframe region. When the write mode is the third access mode, the read mode is set to the first access mode and the same frame video data is continuously output.

  The video data read from the image memory unit 13 corresponds to the video data of the video area requested by the resolution conversion unit 2. The address control unit 17 appropriately controls the number of read pixels per access to the image memory unit 13 in accordance with the difference in the amount of video data corresponding to the route selected by the restoration application switch 15, and sets the number of read pixels. In response, a read address from the image memory unit 13 is designated.

  The resolution conversion unit 2 refers to the video data written in the image memory unit 13 via the address control unit 17 and converts the video data into video data having a magnification set by the operation mode control unit 1 (enlargement / reduction). Resolution conversion processing. The video data after the resolution conversion process is output to the image quality adjustment unit 3.

  When enlarging / reducing processing is performed in the resolution conversion processing, the longer the time that video data is written in the image memory unit 13 until it is read out, the greater the extent (enlargement / reduction ratio) that can be achieved. growing. In the first access mode, the video data can be held for a time corresponding to one vertical synchronization period, and compared to the second access mode in which the video data can be held only for a time corresponding to the number of lines in the subframe area. A large enlargement / reduction ratio can be realized. In the second access mode, only a magnification close to the same magnification can be realized. Therefore, in order to realize a larger enlargement / reduction ratio, it is necessary to write / read the image memory unit 13 in the first access mode.

  The image quality adjustment unit 3 performs gamma correction on the input video data using data of a preset gamma curve, and displays the video data after the gamma correction on a display unit (not shown) (for example, a liquid crystal projector or a liquid crystal display). If it is a monitor, it is output to a liquid crystal panel). Thereby, an image (display image) corresponding to the set magnification is displayed on the display unit.

  There are two types of gamma curves that can be set in the image quality adjustment unit 3: an environment adaptive type and a video correction type. Each type of gamma curve includes a plurality of selectable gamma curves.

  The environment adaptive type gamma curve is designed to be an appropriate gamma curve in a plurality of installation environments assumed in advance. The user selects the gamma curve closest to the actual installation environment from the environment adaptive type gamma curves.

  On the other hand, the video correction type gamma curve includes a plurality of gamma curves having different gamma values (for example, 2.2), and the dark portion or bright portion of the video data is enhanced by changing the selected gamma curve.

  As described above, selecting or changing the gamma curve used for adjusting the gradation of the display video from the environment adaptive type and the video correction type gamma tables is also referred to as correcting the gamma curve.

  The resolution determination unit 4 determines the resolution of the input video data in the horizontal direction and the vertical direction. The determined resolution is output to the operation mode control unit 1.

  Although not shown, the operation unit 5 includes a pause operation unit, an electronic zoom operation unit, a gamma operation unit, and a priority mode operation unit (mode selection means). Each operation unit includes a button, a dial, a keyboard, a pointing device, and the like. It has an operation member.

  When this is operated by the user, the pause operation unit accepts an operation for validating / releasing the pause process of continuously outputting an input video signal at a certain timing until the operation is canceled. The electronic zoom operation unit accepts a user operation for instructing an enlargement process (electronic zoom process) for enlarging a part of the input video data.

  The gamma operation unit accepts an operation for selecting or changing, that is, correcting, a gamma curve that the user wants to use among the gamma curves of the environment adaptive type and the video correction type.

  The priority mode operation unit accepts a user operation for switching between a function priority mode (first video display mode) and a gradation priority mode (second video display mode), which will be described later, as the video display mode. Information on user operation of each operation unit is notified to the operation mode control unit 1.

  The operation mode control unit 1 performs route control that performs compression restoration / detour route switching (state switching) and access mode setting according to the priority mode selected by the priority mode operation unit and the resolution determined by the resolution determination unit 4. The unit 16 and the address control unit 17 are controlled. Further, the operation mode control unit 1 permits or restricts (inhibits) the electronic zoom process and the pause process depending on whether the priority mode selected by the priority mode operation unit is the function priority mode or the gradation priority mode. . Further, the operation mode control unit 1 controls the resolution conversion unit 2 and the image adjustment unit 3 in accordance with operations at the pause operation unit, the electronic zoom operation unit, and the gamma operation unit.

  The flowchart of FIG. 2 shows the operation (control method) of the operation mode control unit 1. The operation mode control unit 1 executes the following processing (steps) according to the computer program stored in the built-in memory.

  In step S101, the operation mode control unit 1 determines whether the set priority mode is the gradation priority mode or the function priority mode. Here, the case where the set priority mode is the function priority mode will be described first. The function priority mode is a mode in which execution of the electronic zoom process and the pause process is prioritized out of whether or not the electronic zoom process and the pause process can be executed and the number of gradations that can be expressed by the display image.

  In step S120, the operation mode control unit 1 reads the resolution of the input video data determined by the resolution determination unit 4. Then, it is determined whether the size (writing capacity) of the image memory unit 13 is larger than the resolution of the input video data, in other words, the size (video data amount) of the input video data corresponding to the resolution. The term “large” includes the case where they are equal.

  When the size of the image memory unit 13 is larger than the resolution, the operation mode control unit 1 sets a bypass route through the route control unit 16 in step S121, and the first access through the address control unit 17 in step S123. Set the mode.

  On the other hand, when the size of the image memory unit 13 is small with respect to the resolution, the operation mode control unit 1 sets a compression / decompression route through the route control unit 16 in step S122 and the first through the address control unit 17 in step S123. 1 access mode is set.

  In this way, setting the compression / restoration route when the size of the image memory unit 13 is small with respect to the resolution reduces the number of gradations that can be expressed in the display image, but compression is performed with the first access mode set. Video data can be written into the image memory unit 13. When the access mode for the image memory unit 13 is set to the first access mode, the resolution conversion unit 2 can perform magnification conversion (resolution conversion) at a large enlargement / reduction ratio, thereby performing electronic zoom processing. It can be permitted (step S126). In addition, by temporarily setting only the write mode of the image memory unit 13 to the third access mode, the pause process can be permitted (step S125).

  In the function priority mode, in step S124, a gamma curve that can be set by the image adjustment unit 3 is set as a video correction type, and correction that emphasizes a dark portion or a bright portion of video data is performed.

  In step S127 to step S134, the operation mode control unit 1 changes the gamma curve according to the gamma curve selection operation, executes the pause process according to the pause operation, or according to the electronic zoom operation. To perform electronic zoom processing.

  In step S135, if the user newly inputs input video data having a different resolution, the process returns to step S120. If the user performs an operation to change the priority mode to the gradation priority mode in step S136, the process returns to step S101.

  Next, the case where the priority mode determined in step S101 is the gradation priority mode will be described. The gradation priority mode is a mode in which priority is given to not reducing the number of gradations out of the number of gradations that can be expressed in the display image and whether or not the electronic zoom process and the pause process can be performed.

  In step S102, the operation mode control unit 1 reads the resolution of the input video data determined by the resolution determination unit 4. Then, it is determined whether or not the size of the image memory unit 13 is larger than the resolution of the input video data (the size of the input video data corresponding to the resolution). This includes the case where it is equal to the larger one.

  When the size of the image memory unit 13 is larger than the resolution, the operation mode control unit 1 sets the first access mode through the address control unit 17 in step S103, as in the function priority mode, and in step S105. A detour route is set through the route control unit 16.

  When the size of the image memory unit 13 is smaller than the resolution, unlike the function priority mode, the operation mode control unit 1 sets the second access mode through the address control unit 17 in step S104, and the route in step S105. A detour route is set through the control unit 16. Thereby, the uncompressed video data can be written in the image memory unit 13 while the bypass route is set.

  In the second access mode, the resolution conversion unit 2 may not be able to execute magnification conversion at a large enlargement / reduction ratio. Therefore, the operation mode control unit 1 performs electronic zoom in the gradation priority mode in step S108. The operation (electronic zoom processing) is restricted (prohibited here). Note that “restricting” the electronic zoom process includes a case where the electronic zoom process is permitted in a state where the enlargement / reduction rate is limited to be smaller than that when the electronic zoom process is not limited.

  For the same reason, even if the write mode is set to the third access mode, there is a case where there is no video data of one frame, the operation mode control unit 1 in the gradation priority mode in step S107. Limit (inhibit here) the pause operation (pause process).

  In the gradation priority mode, the gamma curve that can be set by the image adjustment unit 3 is set as the environment correction type in step S106, and the gamma curve suitable for the installation environment is selected by the user in steps S109 and S110.

  Then, in step S111, the operation mode control unit 1 returns to step S102 when the user newly inputs input video data having a different resolution. If the user performs an operation to change the priority mode to the function priority mode in step S112, the process returns to step S101.

  As described above, in this embodiment, electronic zoom processing and pause processing with gradation reduction other than gamma curve correction are limited in the gradation priority mode that emphasizes gradation expression corresponding to the installation environment of the apparatus. . Thereby, it is possible to reduce the collapse of gradation other than the gamma curve correction. Also, the user can perform gamma curve correction suitable for the installation environment without being conscious of which process is accompanied by gradation reduction.

  In this embodiment, the case where the user directly operates the priority mode operation unit using the operation unit 5 has been described. However, the operation of the priority mode operation unit may be linked to other operations. Further, the name of the gradation priority mode is merely an example, and another name may be used.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

  It is possible to provide an image display apparatus with less gradation collapse other than gamma curve correction.

DESCRIPTION OF SYMBOLS 1 Operation mode control part 4 Resolution determination part 11 Compression part 14 Restoration part 16 Route control part

Claims (3)

Memory means having a first access mode in which video data is sequentially written and read for each frame and a second access mode for sequentially writing and reading in each sub-frame area divided smaller than the one frame;
A compressed output state in which compressed video data generated by compressing gradation of input video data is output as the video data to be written in the memory means, and non-compressed video data in which the input video data is output without being compressed. A compression means capable of switching to a compressed output state;
Switchable between a restored output state in which the compressed video data read from the memory means is restored and output and a non-restored output state in which the uncompressed video data read from the memory means is outputted without being restored. Recovery means,
Gamma curve correction means for correcting the gamma curve for adjusting the gradation of the display image;
Mode selection means capable of switching between a first video display mode and a second video display mode that prioritizes the gradation of the display video over the first video display mode;
Resolution determination means for determining the resolution of the input video data;
Control means for controlling access mode setting of the memory means and state switching of the compression means and the restoration means;
The control means includes
If the first video display mode is set, the memory means is set to the first access mode;
When the second video display mode is set, the compression and decompression unit is set to the non-compression and non-decompression output states, and the memory unit performs the resolution determined by the resolution determination unit. When the write capacity is large, the memory means is set in the first access mode, and when the write capacity of the memory means is small with respect to the resolution, the memory means is set in the second access mode. A characteristic image display device. Resolution conversion means for performing enlargement / reduction processing of the input video data;
The memory means has a third access mode for temporarily prohibiting writing of the video data;
The control means includes
When the first video display mode is set, the setting of the enlargement / reduction processing and the memory means to the third access mode is permitted,
2. The image display apparatus according to claim 1, wherein when the second video display mode is set, the setting of the enlargement / reduction processing and the memory means to the third access mode is restricted. Memory means having a first access mode in which video data is sequentially written and read for each frame and a second access mode for sequentially writing and reading in each sub-frame area divided smaller than the one frame;
A compressed output state in which compressed video data generated by compressing gradation of input video data is output as the video data to be written in the memory means, and non-compressed video data in which the input video data is output without being compressed. A compression means capable of switching to a compressed output state;
Switchable between a restored output state in which the compressed video data read from the memory means is restored and output and a non-restored output state in which the uncompressed video data read from the memory means is outputted without being restored. Recovery means,
Gamma curve correction means for correcting the gamma curve for adjusting the gradation of the display image;
A control method for an image display device, comprising: a first video display mode; and mode selection means capable of switching between a second video display mode that prioritizes the gradation of the display video over the first video display mode. And
Setting the memory means in the first access mode when the first video display mode is set;
When the second video display mode is set, the compression and decompression unit is set to the non-compression and non-decompression output states, and the memory unit is configured to the resolution determined by the resolution determination unit. Setting the memory means to the first access mode when the writing capacity is large, and setting the memory means to the second access mode when the writing capacity of the memory means is small with respect to the resolution; A control method for an image display device, comprising: