JP2010008688A - Image conversion device, image conversion method, liquid crystal display device, image conversion program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve an image conversion device which converts display content into an unidentifiable image when being viewed in an oblique direction. <P>SOLUTION: Since this liquid crystal display device (image conversion device) 1 comprises an interface circuit 2 which converts an image signal input from outside into an image signal indicating a bright image and an image signal indicating a dark image using a look-up table 5, and a liquid crystal drive circuit 3 for synthesizing the bright image and the dark image based on the image signal obtained by conversion and displaying an image on a liquid crystal panel 4, the display contents can be made unidentifiable when a user views the displayed image in the oblique direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image conversion device, an image conversion method, an image conversion method for converting an image so that display contents cannot be identified when viewed from an oblique direction, a liquid crystal display device for displaying an image obtained by the image conversion device, and an image conversion The present invention relates to a program and a recording medium.

  A liquid crystal panel has a feature that it can freely switch between a wide viewing angle characteristic and a narrow viewing angle characteristic mainly by electrical control. The wide viewing angle characteristic is suitable for, for example, viewing an image with a large number of people because an image displayed on the liquid crystal panel can be normally viewed from a wide viewing angle. The narrow viewing angle characteristic is suitable for a case where privacy is required because an image displayed on the liquid crystal panel can be normally viewed only from a narrow viewing angle. Actually, the switching of the viewing angle characteristic is used, for example, as a private filter function of a mobile phone, and is widely applied to others.

  Japanese Patent Application Laid-Open No. 2004-133867 discloses a white floating phenomenon that occurs when a low gradation side is viewed from an oblique viewing angle and a high gradation side that is viewed from an oblique viewing angle in a vertical alignment (VA) type liquid crystal display device. There has been disclosed a liquid crystal display device that can change the viewing angle characteristics on the display screen by changing the contrast and gradation expression ability of the liquid crystal panel by using the gradation collapse phenomenon.

  Specifically, in the liquid crystal display device disclosed in Patent Document 1, as shown in FIG. 16C, the pixels constituting the image are obliquely arranged with respect to the original image indicated by the transmission intensity curve in FIG. By increasing the transmission intensity when viewed from the viewing angle and reducing the amount of change, the above-described white floating phenomenon and gradation collapse phenomenon become prominent, and the viewing angle characteristic is deteriorated to narrow the viewing angle characteristic. Can be made.

Further, the liquid crystal display device, as shown in FIG. 16 (b), shows the transmission intensity when the pixels constituting the image are viewed from an oblique viewing angle with respect to the original image shown by the transmission intensity curve of FIG. 16 (a). By increasing the amount of change, it is possible to weaken the white floating phenomenon and the gradation collapse phenomenon, improve the viewing angle characteristics, and achieve wide viewing angle characteristics.
JP 2004-318112 A (published on November 11, 2004)

  However, in the above conventional configuration, even if narrow viewing angle characteristics are achieved, the user cannot clearly see the image displayed on the liquid crystal panel from outside the range of the viewing angle, but can identify the display contents. This causes a problem.

  In order to prevent the display contents from being identified when the user views from outside the viewing angle range, the liquid crystal display device increases the brightness of the image so that the front transmission intensity of all the pixels constituting the image is increased. Need to scale and display. Therefore, when the user views the image whose luminance is scaled as described above from the front, the entire image becomes bright and difficult to see. In addition, when performing the narrow viewing angle characterization, if the luminance scaling is performed as described above, the brightness of the image viewed by the user from the front and the narrow viewing angle characterization when the wide viewing angle characterization is performed. When this is done, the brightness of the image viewed by the user from the front is greatly different.

  This will be specifically described with reference to FIGS. 16 and 17. FIG. 17 shows an image (b) when the image displayed on the liquid crystal panel is viewed from the front when the image (a) is input to a liquid crystal display device having a conventional configuration, and a case where the image is viewed from 60 degrees obliquely. An image (c) is shown.

  As shown in FIG. 16C, when the narrow viewing angle characterization is performed, the amount of change in the transmission intensity when the image is viewed from 60 degrees obliquely in the range of the front transmission intensity of 0.5 to 1. Although it decreases, since the amount of change in the transmission intensity when viewing the image from 60 degrees obliquely in the range where the front transmission intensity is less than 0.5, as shown in FIG. The display content can be identified even when looking at the liquid crystal panel.

  Here, when the luminance of the image is scaled so that only the region having the front transmission intensity of 0.5 to 1 is used, the amount of change in the transmission intensity when the image is viewed from 60 degrees obliquely becomes smaller. Although it is difficult to identify the display contents when viewing the image, since the front transmission intensity is 0.5 to 1, the entire image becomes bright and difficult to see when viewed from the front. Further, in this case, as shown in FIG. 4A, in the wide viewing angle characterization, a region having a front transmission intensity of 0 to 0.5 is used, and in the narrow viewing angle characterization, the front transmission intensity is 0. .5 to 1 are used, the brightness of the image viewed from the front when the wide viewing angle characterization is performed, and the brightness of the image viewed from the front when the narrow viewing angle characterization is performed. Will be very different.

  The present invention has been made in view of the above problems, and its purpose is to achieve narrow viewing angle characterization without causing a problem that the entire image becomes bright when viewed from the front in a narrow viewing angle state. An image conversion device or image converter that cannot distinguish display contents even when viewed from an oblique viewing angle or an image that can be recognized from the front and an image viewed from an oblique viewing angle. It is to realize a method, a program, and a recording medium. Another object of the present invention is to realize a liquid crystal display device including such an image conversion device.

In order to solve the above problems, an image conversion apparatus according to the present invention provides:
An image conversion device for converting an input image into an output image,
Scaling means for scaling the luminance value of each pixel constituting the input image to any value within a predetermined luminance range;
A dark image generating means for converting a luminance value of each pixel after the scaling into a luminance value equal to or lower than the luminance value using a lookup table;
Bright image generation means for converting the luminance value of each pixel after the scaling into a luminance value equal to or higher than the luminance value using a lookup table, and generating a bright image;
Image generating means for generating the output image by mixing the bright image and the dark image is provided.

  According to the above configuration, the image conversion apparatus scales the luminance value of each pixel constituting the input image to any value within a predetermined luminance range. For example, the luminance value of each pixel constituting the input image is scaled to any value between 0.05 and 0.5.

  In addition, the image conversion apparatus uses a dark lookup table in which substantially the same dark luminance value is associated with each input luminance value within the luminance range, and converts the luminance value of each pixel after scaling to the luminance. A dark image is generated by converting to a dark luminance value corresponding to the value.

  Further, the image conversion apparatus uses each of the input luminance values within the luminance range and a bright lookup table in which the bright luminance values that change according to the change of the input luminance value are associated with each other after the scaling. A bright image is generated by converting the luminance value of the pixel into a bright luminance value corresponding to the luminance value.

  Further, the image conversion device generates an output image by mixing the bright image and the dark image.

  Here, mixing of a bright image and a dark image will be described with reference to specific examples with reference to FIGS.

  As an example, an image composed of an area 25b having a scaled luminance value of 0.1 and an area 25a having a scale of 0.4 as shown in FIG.

  In this original image, when viewed from the front, naturally, the region 25b with a luminance value of 0.1 appears dark and the region 25a with a luminance value of 0.4 appears bright, so that the observer can recognize the image. is there.

  FIG. 7B shows an image when the original image is viewed from an oblique direction. As can be seen from the case 1 in the graph of FIG. 5, the region 25 b with a luminance value of 0.1 appears to have a luminance value of about 0.7, and the region 25 a with a luminance value of 0.4 appears to have a luminance value of about 1. Thus, the image is composed of a region 25d having a luminance value of about 0.7 and a region 25c having a luminance value of about 1. In this case as well, although it is difficult to see because the ratio of luminance values is small compared to the front, it is possible to recognize the same image as the front image.

  Here, as shown in the graph of FIG. 6, the state where the brightness value after scaling using the bright lookup table is 0.1 is set to about 0.195, and the state where the brightness value is 0.4 is set to the brightness value. Convert each to about 0.8. By this step, the bright image becomes an image formed with an area having a luminance value of about 0.195 and a luminance value of about 0.8.

  Similarly, using a dark lookup table, a state where the luminance value after scaling is 0.1 is converted to a luminance value of about 0.005, and a state where the luminance value is 0.4 is converted to a luminance value of about 0. By this step, the dark image becomes an image formed with a luminance value of about 0.005 and a luminance value of about 0. The bright image created in this way and the dark image are mixed at a ratio of 1: 1. The method of mixing will be described later.

  FIG. 7C shows a mixed image when viewed from the front. The region 25b having a luminance value of 0.1 in the original image is a one-to-one mixed region 25f having a luminance value of 0.195 and a luminance value of 0.005 as a result of mixing the images. It looks as a state. Similarly, the region 25a having a luminance value of 0.4 in the original image becomes a one-to-one mixed region 25e of the luminance value 0.8 and the luminance value 0 as a result of mixing the images. It appears as a state of 4. For this reason, when viewed from the front, the observer can recognize the same image as the original image.

  FIG. 7D shows an image when this image is viewed from an oblique direction. As can be seen from the case 1 in the graph of FIG. 5, the area with the luminance value of 0.195 in the front is about 0.85, the area with the luminance value 0.05 is about 0.15, and the luminance value is 0.8. The region with a luminance value of about 1 and the region with a luminance value of 0 appear as about 0.

  Here, the region 25b having a luminance value of 0.1 in the original image is a one-to-one mixed region 25h having a luminance value of about 0.85 and a luminance value of about 0.15 when viewed from an oblique direction. Appears as 0.5. Similarly, the region 25b having a luminance value of 0.4 in the original image results in a one-to-one mixed region 25g having a luminance value of about 1 and a luminance value of about 0 as a result of mixing the images. It appears as a state of 5.

  In other words, the observer can recognize the image in front, but the observer cannot recognize the image when viewed from an oblique direction.

  As described above, the image conversion apparatus has a look-up table in which an image having a predetermined luminance range is converted and displayed, the front transmission intensity of the image is in a certain range, and the oblique transmission intensity is substantially constant. Therefore, the display content can be recognized because there is a difference in luminance when viewed from the front, but it can be converted into an image that cannot be identified because there is no difference in luminance when viewed from an oblique direction.

  Also, since the image can be converted without significantly reducing the contrast of the image obtained by the conversion, the narrow viewing angle characteristics can be obtained without causing a problem that the entire image becomes bright when viewed from the front in a narrow viewing angle state. Even if the image obtained by performing the above is viewed from an oblique viewing angle, the display content can be made indistinguishable.

In order to solve the above problems, an image conversion apparatus according to the present invention provides:
An image conversion device for converting an input image into an output image,
Scaling means for scaling the luminance value of each pixel constituting the input image to any value within a predetermined luminance range;
Each input luminance value less than a predetermined value in the luminance range is associated with substantially the same dark luminance value, and for each input luminance value greater than or equal to the predetermined value in the luminance range, the input luminance value A dark image is generated by converting the luminance value of each pixel after scaling to the dark luminance value corresponding to the luminance value using a dark lookup table in which dark luminance values substantially equal to Dark image generation means;
Each input luminance value that is less than the predetermined value in the luminance range is associated with a bright luminance value that changes according to the change in the input luminance value, and each input that is greater than or equal to the predetermined value in the luminance range Using a bright lookup table in which a brightness value substantially equal to the input brightness value is associated with the brightness value, the brightness value of each pixel after the scaling is changed to the brightness value corresponding to the brightness value. A bright image generating means for generating a bright image by converting;
Image generating means for generating the output image by mixing the bright image and the dark image is provided.

  According to the above configuration, the image conversion apparatus scales the luminance value of each pixel constituting the input image to any value within a predetermined luminance range. For example, the luminance value of each pixel constituting the input image is scaled to any value between 0.05 and 1.

  Further, the image conversion apparatus associates substantially the same dark luminance value with each input luminance value that is less than a predetermined value in the luminance range, and for each input luminance value that is equal to or greater than the predetermined value in the luminance range. A dark image is obtained by converting the luminance value of each pixel after scaling into a dark luminance value corresponding to the luminance value using a dark lookup table in which a dark luminance value substantially equal to the input luminance value is associated. Is generated.

  Further, the image conversion apparatus associates each input luminance value less than the predetermined value in the luminance range with a bright luminance value that changes according to the change in the input luminance value, and the predetermined luminance in the luminance range. For each input luminance value greater than or equal to the input luminance value, a bright lookup table in which a bright luminance value substantially equal to the input luminance value is associated is used, and the luminance value of each pixel after scaling is associated with the luminance value. A bright image is generated by converting to a bright luminance value.

  Further, the image conversion device generates an output image by mixing the bright image and the dark image.

  As described above, the image displayed on the image conversion apparatus is a mixture of a bright image and a dark image, and the transmission intensity value when viewed from an oblique direction of each pixel takes only two values. When the image is viewed from an oblique direction, the display content cannot be identified.

In order to solve the above problems, an image conversion method according to the present invention provides:
An image conversion method for converting an input image into an output image,
A scaling step for scaling the luminance value of each pixel constituting the input image to any value within a predetermined luminance range;
A dark image generation step of converting the luminance value of each pixel after the scaling into a luminance value equal to or lower than the luminance value using a lookup table, and generating a dark image;
A bright image generation step of generating a bright image by converting the luminance value of each pixel after the scaling into a luminance value equal to or higher than the luminance value using a lookup table;
And an image generation step of generating the output image by mixing the bright image and the dark image.

  According to said structure, there exists an effect similar to the image converter which concerns on this invention.

In order to solve the above problems, an image conversion method according to the present invention provides:
An image conversion method for converting an input image into an output image,
A scaling step for scaling the luminance value of each pixel constituting the input image to any value within a predetermined luminance range;
Each input luminance value less than a predetermined value in the luminance range is associated with substantially the same dark luminance value, and for each input luminance value greater than or equal to the predetermined value in the luminance range, the input luminance value A dark image is generated by converting the luminance value of each pixel after scaling to the dark luminance value corresponding to the luminance value using a dark lookup table in which dark luminance values substantially equal to A dark image generation step;
Each input luminance value that is less than the predetermined value in the luminance range is associated with a bright luminance value that changes according to the change in the input luminance value, and each input that is greater than or equal to the predetermined value in the luminance range Using a bright lookup table in which a brightness value substantially equal to the input brightness value is associated with the brightness value, the brightness value of each pixel after the scaling is changed to the brightness value corresponding to the brightness value. A bright image generating step for generating a bright image by converting;
And an image generation step of generating the output image by mixing the bright image and the dark image.

  According to said structure, there exists an effect similar to the image converter which concerns on this invention.

An image conversion apparatus according to the present invention includes:
In the image generation means, the output image can be generated by temporally mixing the bright image and the dark image.

An image conversion apparatus according to the present invention includes:
In the image generation means, the output image can be generated by spatially mixing the bright image and the dark image.

An image conversion apparatus according to the present invention includes:
In the image generation means, the output image can be generated by mixing the bright image and the dark image temporally and spatially.

An image conversion apparatus according to the present invention includes:
It is desirable that the luminance range is approximately 0.05 or more and approximately 0.5 or less.

  According to said structure, there exists an effect that it becomes impossible to identify display content, when the said output image is seen from 60 degree | times diagonally.

  Here, the numerical values (0.05 and 0.5) of the luminance range mean the luminance when the luminance of the pixel having the maximum luminance in the input image is set to 1.

An image conversion apparatus according to the present invention includes:
It is desirable that the luminance range is from about 0.05 to about 1.

  According to said structure, when the said output image is seen from diagonally 60 degree | times, there exists an effect that the expression of gradation becomes invisible.

  Here, the numerical values (0.05 and 0.5) of the luminance range mean the luminance when the luminance of the pixel having the maximum luminance in the input image is set to 1.

  A liquid crystal display device according to the present invention displays an output image converted from an input image by the image conversion device.

  The liquid crystal display device preferably has a vertical alignment (VA) display method.

  The image conversion apparatus may be realized by a computer. In this case, an image conversion program for realizing the image conversion apparatus in the computer by operating the computer as each of the above means and a computer-readable recording medium on which the image conversion program is recorded also fall within the scope of the present invention.

  As described above, the image conversion apparatus according to the present invention scales the luminance value of each pixel constituting the input image to any value within a predetermined luminance range. Next, the luminance value of each pixel after the scaling is converted into a luminance value equal to or lower than the luminance value using a look-up table to generate a dark image. The brightness value of each pixel after the scaling is converted into a brightness value equal to or higher than the brightness value by using a lookup table to generate a bright image. Thereafter, the generated bright image and dark image are mixed.

  Thereby, when the image obtained by mixing is viewed from an oblique direction, the display content cannot be identified.

[Embodiment 1]
An embodiment of a liquid crystal display device according to the present invention will be described with reference to FIGS.

(Configuration of the liquid crystal display device 1)
The configuration of the liquid crystal display device 1 according to the present invention will be described below with reference to FIG. FIG. 2 is a block diagram illustrating a configuration of a main part of the liquid crystal display device 1. The liquid crystal display device 1 calculates a luminance value for each unit constituting the image based on the video signal input from the system device 10, and refers to the lookup table 5 based on the calculated luminance value to obtain two luminance values. The values (high luminance value and low luminance value) are calculated, and for each unit, the pixels constituting the unit are converted into pixels having the calculated high luminance value and pixels having the low luminance value, and the liquid crystal panel 4 It is a device that displays.

  The liquid crystal display device 1 includes an interface circuit 2 (scaling means, dark image generating means, bright image generating means), a liquid crystal driving circuit 3 (image generating means), a liquid crystal panel 4, and a lookup table 5. Details of each member will be described later.

(Operation of the liquid crystal display device 1)
The operation of the liquid crystal display device 1 will be described with reference to FIG. FIG. 1 is a flowchart showing the operation of the liquid crystal display device 1 when a video signal is input from the system device 10 to the liquid crystal display device 1.

  When the interface circuit 2 receives the video signal input from the system apparatus 10, the interface circuit 2 performs scaling of the luminance of an image obtained based on the received video signal. After performing the luminance scaling, the luminance value of each color of RGB is calculated for each unit constituting the image (S1). Details of luminance scaling and units will be described later.

  Next, the interface circuit 2 selects one unit from a plurality of units constituting the image (S2), and calculates the brightness value in the bright state and the brightness value in the dark state in RGB. Based on the luminance value of the corresponding unit calculated in S1 for any one of the unexisting colors, the luminance value in the bright state and the luminance value in the dark state are calculated using the lookup table 5. (S3). Here, the bright state means a relatively bright state, and the dark state means a relatively dark state.

  When the brightness value in the bright state and the brightness value in the dark state are calculated for all three colors of RGB for the unit selected in S2 (YES in S4), the process proceeds to S5 and the brightness value in the bright state and the brightness value in the dark state Is not calculated (NO in S4), the process returns to S3.

  In S5, the interface circuit 2 determines whether or not there is a unit that has not yet calculated the brightness value in the bright state and the brightness value in the dark state. If such a unit exists (YES in S5), the process returns to S2. If no such unit exists (NO in S5), the process proceeds to S6.

  In S <b> 6, the interface circuit 2 outputs the brightness value in the bright state and the brightness value in the dark state of each unit calculated in S <b> 2 to S <b> 5 to the liquid crystal drive circuit 3. The liquid crystal drive circuit converts the brightness value of a part of the pixels constituting the unit to the brightness value of the light state for each unit based on the brightness value of the light state and the brightness value of the dark state of each unit. Thus, the drive voltage is supplied to each pixel of the liquid crystal panel 4 so that the luminance values of the remaining pixels constituting the unit become the luminance values in the dark state. As a result, the entire image is displayed on the liquid crystal panel 4.

(unit)
The units constituting the image will be described with reference to FIG.

  A unit means a pixel group in which a plurality of pixels are combined, or a pixel group composed of a plurality of frames, each frame including one or more pixels (groups).

  Some of the pixels that make up the unit are pixels with a certain luminance value, the remaining pixels are pixels with another luminance value, and pixels with two different luminance values are alternately arranged or displayed alternately. By doing so, the unit becomes halftone when viewed from the human eye.

  For example, as shown in FIG. 3A, when the unit 20 is composed of a pixel 20a having a certain luminance value and a pixel 20b having another luminance value, the region of the pixel 20a is the region of the pixel 20b, And it is divided into a plurality of regions by the boundary of the unit. Similarly, the region of the pixel 20b is divided into a plurality of regions by the region of the pixel 20a and the boundary of the unit. Here, as the number of the pixels 20a is equal to the number of the pixels 20b and the number of the regions of the pixel 20a and the number of the regions of the pixel 20b are larger, the gradation of the unit is larger as viewed from the human eyes. It looks like a halftone.

  Further, as shown in FIG. 3B, the unit 20 is composed of a pixel 20a having a certain luminance value and a pixel 20b having another luminance value, and when the frame is switched, the pixel in the area where the pixel 20a was displayed. Is the luminance value of the pixel in the area where the pixel 20b is displayed, and the luminance value of the pixel in the area where the pixel 20b is displayed is the luminance value of the pixel in the area where the pixel 20b is displayed. Shall. In this case, since the frames are switched at a high speed, the gradation of the unit appears to be halftone as seen from the human eye.

  3A and 3B are given as specific examples of the unit. However, the unit is not limited to these, and how many pixels are included in one frame. Also good. Further, when the unit is composed of a plurality of frames, the number of frames may be any number. Furthermore, the number of pixels having a certain luminance value and the number of pixels having different luminance values that constitute the unit may not be equal.

(Luminance scaling)
A luminance scaling method according to this embodiment will be described.

  Scaling in the present invention is to replace the luminance value of each pixel constituting the input image with a luminance value that can be converted by a lookup table described later.

  For example, when the input image is configured in the range where the lowest luminance is 0 and the highest luminance is 1 among the pixels constituting the input image, the lowest luminance is 0.05 and the highest luminance is 0.5. If the luminance is between those values, the luminance is appropriately replaced so that the original luminance level is not changed. As a result, the entire image can be replaced with an image that can be converted by the lookup table.

  Note that the range of luminance replacement is not particularly specified, and it is sufficient that the original luminance level is not switched. When the input image is configured in the range where the lowest luminance is 0.5 and the highest luminance is 0.6 among the pixels constituting the input image, the lowest luminance is 0.1 and the highest luminance is 0. It is also possible to shift and expand the luminance range so as to be .5.

(Conversion using lookup table)
A conversion method using the luminance lookup table according to the present embodiment will be described with reference to FIGS.

  First, with reference to FIG. 3, a unit will be described in which the brightness is different when viewed from the front, but the brightness looks the same when viewed from an oblique direction.

  FIG. 3C shows an example of a plurality of units that look the same when viewed from the front, but look different when viewed from an oblique direction. In FIG. 3C, the average value of the luminance value of the pixel 20d and the luminance value of the pixel 20e, the average value of the luminance value of the pixel 20f and the luminance value of the pixel 20g, and the luminance value of the pixel 20h are the same. . Further, the luminance value of the pixel 20d is larger than the luminance value of the pixel 20f, and the luminance value of the pixel 20e is smaller than the luminance value of the pixel 20g. The larger the difference between the two luminance values of the pixels that make up the unit, the darker the portion of the unit when viewed from the diagonal. The smaller the difference between the two luminance values of the pixels that make up the unit, the smaller the unit when viewed from the diagonal. The part of looks bright.

  By applying this, it is possible to create a plurality of units that look different when viewed from the front and look the same when viewed from the diagonal. FIG. 3D is an example of such a unit. Here, the average value of the luminance value of the pixel 20i and the luminance value of the pixel 20j is larger than the average value of the luminance value of the pixel 20k and the luminance value of the pixel 20l. The average value of the luminance value of the pixel 20i and the luminance value of the pixel 20j is larger than the luminance value of the pixel 20m. However, the brightness of each unit looks the same when viewed from an angle.

  Next, when an appropriate look-up table is selected and an image is converted using FIG. 4 and FIG. 5, the front transmission intensity of the constituent pixels is a value within a certain range, and viewed from an oblique direction Image area in which the transmission intensity of the image is substantially constant (that is, an image area composed of units having different brightness when viewed from the front as shown in FIG. 3D and the same brightness when viewed from an oblique direction) It will be explained that an image having can be generated.

  FIG. 4 shows an example of three lookup tables.

  The look-up table in Case 1 is a look-up table in which the luminance does not change between the bright state and the dark state even if the unit is converted. The look-up table in Case 2 shows that when the front transmission intensity of the unit is changed from 0 to 1, the bright state first brightens and then reaches the white state, then the dark state becomes brighter, and finally both are in the white state. This is a look-up table.

  The look-up table in Case 3 shows that when the front transmission intensity of the unit is changed from 0 to 1, when the front transmission intensity is 0.23 or less, only the bright state is bright and the front transmission intensity exceeds 0.23. The look-up table is such that both the bright state and the dark state become bright.

  FIG. 5 shows the relationship between the front transmission intensity of the converted image and the transmission intensity when viewed obliquely from 60 degrees in each lookup table.

  For many of the units constituting the image, the transmission intensity when the unit obtained using the case 3 look-up table is viewed obliquely is the unit obtained using the case 1 look-up table. It can be seen that the transmission intensity is smaller than the transmission intensity when viewed obliquely and is larger than the transmission intensity when the unit obtained using the lookup table of Case 2 is viewed obliquely.

  The example of three look-up tables is shown, but by adjusting the look-up table and adjusting the difference between the bright state and the dark state, the same gradation as the image before conversion when viewed from the front While displaying, it is possible to arbitrarily select the transmission intensity when viewed from an oblique direction.

  Therefore, by converting the luminance so that all the units composing the image have front transmission intensity such that the transmission intensity when viewed obliquely is substantially constant, the image cannot be identified when viewed obliquely. Can be possible.

  The luminance conversion according to the present embodiment is to convert the luminance so that the transmission intensity when viewed obliquely is substantially constant for all the units constituting the image obtained by the conversion. .

(Application result)
When an appropriate lookup table is selected as described above and the luminance is converted so that the transmission intensity when viewed obliquely becomes substantially constant, the image can be made indistinguishable when viewed obliquely.

  The liquid crystal display device 1 according to the present embodiment performs, for example, luminance scaling so that the front transmission intensity of the converted image falls within the range of the elementary characteristics in FIG. Such a lookup table 5 is applied.

  FIGS. 9B and 9C show the image obtained as a result of viewing from the front and the image viewed from 60 degrees from the oblique direction, respectively. FIG. 9A shows an image before conversion.

  The image viewed from the front of FIG. 9B has a contrast of 10, and the image can be identified. However, the image viewed from an oblique angle of 60 ° in FIG. It can be seen that cannot be identified.

  Note that, as an example of the lookup table used in the present embodiment, the lookup table as shown in FIG. 6 has been described, but the lookup table 5 of the present embodiment is not limited to this, and is converted. Any lookup table may be used as long as the oblique transmission intensity with respect to a certain range of the front transmission intensity in the obtained image becomes a substantially constant value.

(Advantages of the liquid crystal display device 1)
The liquid crystal display device 1 according to the present embodiment is a sufficiently distinguishable image when viewed from the front by the user, although it has a lower contrast than the image before conversion, and has a contrast when viewed from an oblique direction. An image that is almost 1 and cannot be identified can be displayed on the liquid crystal panel 4.

[Embodiment 2]
Next, another embodiment of the liquid crystal display device 1 according to the present invention will be described with reference to FIG. 2, FIG. 6, FIG. 10, and FIG.

(Configuration of the liquid crystal display device 1)
The configuration of the liquid crystal display device 1 according to the present embodiment is shown in FIG. FIG. 2 is a block diagram illustrating a configuration of a main part of the liquid crystal display device 1. In addition, since the structure of the liquid crystal display device 1 which concerns on this embodiment is the same as that of the liquid crystal display device 1 which concerns on Embodiment 1, description about each member is abbreviate | omitted.

(Application result)
The liquid crystal display device 1 according to the present embodiment performs, for example, luminance scaling so that the front transmission intensity of the converted image falls within the range of the elementary characteristics shown in FIG. Such a lookup table 5 is applied.

  FIGS. 11 (b) and 11 (c) show an image when the image obtained as a result is viewed from the front and an image when the image is viewed from 60 degrees from an oblique direction, respectively. FIG. 11A shows an image before conversion.

  The image viewed from the front of FIG. 11B has a contrast of 20, which is higher than the image obtained using the liquid crystal display device 1 of the first embodiment. Therefore, when the user views the liquid crystal panel 4 from the front, a clearer image can be seen.

  In addition, the image viewed from an oblique angle of 60 degrees in FIG. 11C has a contrast of 1.7, which is higher than the image obtained using the liquid crystal display device 1 of the first embodiment. However, although the contrast is high, as shown in FIG. 10, the oblique transmission intensity of the image displayed on the liquid crystal display device 1 according to the present embodiment takes only two values of 0.6 and 1. As shown in FIG. 11C, it can be seen that the expression of gradation is completely invisible and the display content of the image cannot be identified.

  Note that the look-up table in FIG. 6 is given as an example of the look-up table used in the present embodiment, but the look-up table 5 in the present embodiment is not limited to this, and an image obtained by conversion. If the look-up table in which the oblique transmission intensity with respect to a certain range of the front transmission intensity is substantially constant, and the oblique transmission intensity with respect to another certain range of the front transmission intensity is a substantially constant value different from the substantially constant value, Any lookup table is acceptable.

(Advantages of the liquid crystal display device 1)
The liquid crystal display device 1 according to the present embodiment is an image having substantially the same contrast as the image before conversion when viewed from the front by the user, and has no gradation expression when viewed from an oblique direction. An image that cannot be seen and cannot be identified can be displayed on the liquid crystal panel 4.

[Embodiment 3]
Next, still another embodiment of the liquid crystal display device 1 of the present invention will be described with reference to FIG. 2 and FIGS.

(Configuration of the liquid crystal display device 1)
The configuration of the liquid crystal display device 1 according to the present embodiment is shown in FIG. FIG. 2 is a block diagram illustrating a configuration of a main part of the liquid crystal display device 1. In addition, since the structure of the liquid crystal display device 1 which concerns on this embodiment is the same as the structure of the liquid crystal display device 1 which concerns on Embodiment 1 and Embodiment 2, description about each member is abbreviate | omitted.

(Operation of the liquid crystal display device 1)
The operation of the liquid crystal display device 1 will be described with reference to FIG.

  FIG. 12 is a flowchart showing the operation of the liquid crystal display device 1 when a video signal is input from the system device 10 to the liquid crystal display device 1.

  When the interface circuit 2 receives the video signal input from the system apparatus 10, the interface circuit 2 performs scaling of the luminance of an image obtained based on the received video signal. After the luminance scaling, the luminance value of each color of RGB is calculated for each unit constituting the image (S11).

  Next, the interface circuit 2 selects one unit from a plurality of units constituting the image (S12), and calculates the brightness value in the bright state and the brightness value in the dark state in RGB. Based on the luminance value of the corresponding unit calculated in S1 for any one of the unexisting colors, the luminance value in the bright state and the luminance value in the dark state are calculated using the lookup table 5. (S13), go to S14.

  Here, in order to make the image in the unit visible from an oblique direction, a look-up table that increases the transmission intensity when viewed obliquely is used. On the other hand, when the image in the unit is made invisible from an oblique direction, a look-up table is used so that the transmission intensity when viewed from the oblique direction becomes small. That is, in this embodiment, two sets of lookup tables are required.

  However, in general, in the case of a vertical alignment (VA) type liquid crystal display device, when the transmission intensity when viewed obliquely is the highest, both the brightness value in the bright state and the brightness value in the dark state are converted. This is the case when it is equal to the previous input luminance value. For this reason, a look-up table that increases the transmission intensity when viewed obliquely eliminates the conversion work by using the input luminance value before conversion as the luminance value in the bright state and the luminance value in the dark state as they are. Is possible. In this case, only a look-up table that reduces the transmission intensity when the image in the unit is viewed obliquely is required.

  In S14, the interface circuit 2 calculates the dark state / bright state in S13, and the bright state based on the corresponding unit brightness of the image to be displayed obliquely with respect to the color that has not yet been converted in S14. / The dark state is converted, and the process proceeds to S15.

  In S15, the interface circuit 2 determines whether the brightness value in the bright state and the brightness value in the dark state have been converted for all three colors of RGB for the unit selected in S12. When the brightness value in the bright state and the brightness value in the dark state are converted for all three colors of RGB (YES in S15), the process proceeds to S16, and the brightness value in the bright state and the brightness value in the dark state are converted for all three colors of RGB. If not (NO in S15), the process returns to S13.

  In S16, the interface circuit 2 determines whether there is a unit that has not yet converted the brightness value in the bright state and the brightness value in the dark state. If such a unit exists (YES in S16), the process returns to S12. If no such unit exists (NO in S16), the process proceeds to S17.

  In S <b> 17, the interface circuit 2 outputs the brightness value in the bright state and the brightness value in the dark state of each unit calculated and converted in S <b> 12 to S <b> 16 to the liquid crystal drive circuit 3. The liquid crystal driving circuit 3 uses the brightness value in the bright state and the brightness value in the dark state of each unit as input, and for each unit, the brightness value of a part of the pixels constituting the unit is the brightness value in the bright state. The drive voltage is applied to each pixel of the liquid crystal panel 4 so that the luminance values of the remaining pixels constituting the unit become the luminance values in the dark state. As a result, the entire image is displayed on the liquid crystal panel 4.

(Application result)
In the present embodiment, an image is converted using a look-up table used when making an image in the unit visible from an oblique direction and a look-up table used when making an image in the unit visible from the front. To do. FIG. 13 shows the relationship between the front transmission intensity of the converted image and the transmission intensity when viewed from 60 degrees obliquely when these look-up tables are used.

  Here, the solid line (white at 60 degrees diagonally) is from the front transmission intensity of the unit converted using the look-up table used when making the image in the unit look brightest when viewed obliquely and from 60 degrees from the diagonal. The broken line (60-degree black diagonal) indicates the unit converted by using the lookup table used to make the image in the unit look the darkest when viewed obliquely. This is the relationship between the front transmission intensity and the transmission intensity when viewed from 60 degrees obliquely.

  The liquid crystal display device 1 according to the present embodiment performs luminance scaling so that the front transmission intensity of the image after luminance scaling falls within the range of the elementary characteristics shown in FIG. An image obtained by applying two look-up tables so that the transmission intensity when viewed from above is within the hatched area of FIG. 13 is displayed.

  FIG. 14B and FIG. 14B show an image when the image obtained by conversion using the two look-up tables as described above is viewed from the front, and an image when viewed from 60 degrees from the oblique direction, respectively. 14 (c). FIG. 14A shows an image before conversion.

  The image viewed from the front of FIG. 14B has a contrast of 3, and the image viewed from the diagonal of FIG. Further, the display content of the image when viewed from the front is different from the display content of the image when viewed from the diagonal.

(Advantages of the liquid crystal display device 1)
In the liquid crystal display device 1 according to the present embodiment, when the user views from the front, both the image when viewed from the front compared to the image before conversion, and the image when viewed from the diagonal, Although the contrast is low, different images can be displayed on the liquid crystal panel 4 when viewed from the front and when viewed from an oblique direction.

(Program, recording medium)
Finally, as shown in FIG. 15, the liquid crystal display device 1 does not convert the image signal, but executes a program for converting the image signal in the external system device 40, and the converted image signal is converted into the liquid crystal display device. 30 may receive and display.

  Further, each block included in the liquid crystal display device 1 may be configured by hardware logic. Alternatively, it may be realized by software using a CPU (Central Processing Unit) as follows.

  In other words, the liquid crystal display device 1 only needs to record the program code (execution format program, intermediate code program, source program) of a control program that realizes each function so that it can be read by a computer. The liquid crystal display device 1 (or CPU or MPU) may read and execute the program code recorded on the supplied recording medium.

  The recording medium for supplying the program code to the liquid crystal display device 1 is, for example, a tape system such as a magnetic tape or a cassette tape, a magnetic disk such as a floppy (registered trademark) disk / hard disk, or a CD-ROM / MO / MD / DVD / CD. A disk system including an optical disk such as -R, a card system such as an IC card (including a memory card) / optical card, or a semiconductor memory system such as a mask ROM / EPROM / EEPROM / flash ROM.

  Further, even if the liquid crystal display device 1 is configured to be connectable to a communication network, the object of the present invention can be achieved. In this case, the program code is supplied to the liquid crystal display device 1 via a communication network. The communication network may be any network that can supply program codes to the liquid crystal display device 1 and is not limited to a specific type or form. For example, the Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, mobile communication network, satellite communication network, etc. may be used.

  The transmission medium constituting the communication network may be any medium that can transmit the program code, and is not limited to a specific configuration or type. For example, wired communication such as IEEE 1394, USB (Universal Serial Bus), power line carrier, cable TV line, telephone line, ADSL (Asymmetric Digital Subscriber Line) line, infrared light such as IrDA or remote control, Bluetooth (registered trademark), 802. 11 wireless, HDR, mobile phone network, satellite line, terrestrial digital network, etc. can also be used. The present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

(Additional notes)
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The image conversion apparatus according to the present invention can be widely used, such as being applied to a device such as a mobile phone where a liquid crystal screen is not desired to be seen by others depending on the situation.

4 is a flowchart showing the operation of the liquid crystal display device according to the first and second embodiments of the present invention. 1, showing an embodiment of the present invention, is a block diagram illustrating a main configuration of a liquid crystal display device. FIG. It is a figure explaining the concept of the unit used in the embodiment of the present invention. It is a figure explaining a lookup table. It is a figure which shows the relationship between the front transmission intensity | strength of the image converted using each look-up table of FIG. 4, and the transmission intensity | strength at the time of seeing from diagonal 60 degree | times. It is a figure which shows the look-up table which concerns on Embodiment 1 and 2 of this invention. It is a figure explaining the mixture of the bright image and dark image in this invention, and is a figure which shows the mixed image of the original image at the time of seeing from each of front and diagonal, and the bright image and dark image which were produced | generated from this original image is there. It is a figure which shows the relationship between the front transmission intensity | strength of the image converted using the lookup table which concerns on Embodiment 1 of this invention, and the transmission intensity | strength at the time of seeing from diagonal 60 degree | times, and the range of an elementary characteristic. 4 is an image displayed on a liquid crystal panel of the liquid crystal display device according to Embodiment 1 and an image represented by an image signal input to the liquid crystal display device. It is a figure which shows the relationship between the front transmission intensity | strength of the image converted using the look-up table which concerns on Embodiment 2 of this invention, and the transmission intensity | strength at the time of seeing from 60 degree | times, and the range of an elementary characteristic. 5 is an image displayed on a liquid crystal panel of a liquid crystal display device according to Embodiment 2 and an image represented by an image signal input to the liquid crystal display device. It is a flowchart showing operation | movement of the liquid crystal display device which concerns on Embodiment 3 of this invention. It is a figure which shows the relationship between the front transmission intensity | strength of the image converted using the look-up table concerning Embodiment 3 of this invention, and the transmission intensity | strength at the time of seeing from diagonal 60 degree | times, and the range of an elementary characteristic. 5 is an image displayed on a liquid crystal panel of a liquid crystal display device according to Embodiment 3 and an image represented by an image signal input to the liquid crystal display device. FIG. 3 is a configuration diagram of a liquid crystal display device and a system device in which a program is stored when image conversion according to the present invention is realized using a program. It shows a conventional technique, and shows the relationship between the front transmission intensity at a narrow viewing angle and a wide viewing angle and the transmission intensity when viewed from an oblique angle of 60 degrees of an image converted using the conventional technique. FIG. It shows a prior art and is an image displayed on a liquid crystal panel of a liquid crystal display device using the prior art and an image represented by an image signal input to the liquid crystal display device.

Explanation of symbols

1 Liquid crystal display device (image conversion device)
2 Interface circuit (scaling means, dark image generating means, bright image generating means)
3 Liquid crystal drive circuit (image generation means)
4 Liquid crystal panel 5 Look-up table 10 System device 20 Unit 30 Liquid crystal display device 40 System device

Claims (13)

An image conversion device for converting an input image into an output image,
Scaling means for scaling the luminance value of each pixel constituting the input image to any value within a predetermined luminance range;
A dark image generating means for converting a luminance value of each pixel after the scaling into a luminance value equal to or lower than the luminance value using a lookup table;
Bright image generation means for converting the luminance value of each pixel after the scaling into a luminance value equal to or higher than the luminance value using a lookup table, and generating a bright image;
An image conversion apparatus comprising: an image generation unit configured to generate the output image by mixing the bright image and the dark image. An image conversion device for converting an input image into an output image,
Scaling means for scaling the luminance value of each pixel constituting the input image to any value within a predetermined luminance range;
Each input luminance value less than a predetermined value in the luminance range is associated with substantially the same dark luminance value, and for each input luminance value greater than or equal to the predetermined value in the luminance range, the input luminance value A dark image is generated by converting the luminance value of each pixel after scaling to the dark luminance value corresponding to the luminance value using a dark lookup table in which dark luminance values substantially equal to Dark image generation means;
Each input luminance value that is less than the predetermined value in the luminance range is associated with a bright luminance value that changes according to the change in the input luminance value, and each input that is greater than or equal to the predetermined value in the luminance range Using a bright lookup table in which a brightness value substantially equal to the input brightness value is associated with the brightness value, the brightness value of each pixel after the scaling is changed to the brightness value corresponding to the brightness value. A bright image generating means for generating a bright image by converting;
An image conversion apparatus comprising: an image generation unit configured to generate the output image by mixing the bright image and the dark image. The image generation means includes
The output image is generated by temporally mixing the bright image and the dark image,
The image conversion apparatus according to claim 1. The image generation means includes
The output image is generated by spatially mixing the bright image and the dark image,
The image conversion apparatus according to claim 1. The image generation means includes
The output image is generated by temporally and spatially mixing the bright image and the dark image,
The image conversion apparatus according to claim 1. The luminance range is about 0.05 or more and about 0.5 or less,
The image conversion apparatus according to claim 1. The luminance range is about 0.05 or more and about 1 or less,
The image conversion apparatus according to claim 2. An image conversion method for converting an input image into an output image,
A scaling step for scaling the luminance value of each pixel constituting the input image to any value within a predetermined luminance range;
A dark image generation step of converting the luminance value of each pixel after the scaling into a luminance value equal to or lower than the luminance value using a lookup table, and generating a dark image;
A bright image generation step of generating a bright image by converting the luminance value of each pixel after the scaling into a luminance value equal to or higher than the luminance value using a lookup table;
An image conversion method including an image generation step of generating the output image by mixing the bright image and the dark image. An image conversion method for converting an input image into an output image,
A scaling step for scaling the luminance value of each pixel constituting the input image to any value within a predetermined luminance range;
Each input luminance value less than a predetermined value in the luminance range is associated with substantially the same dark luminance value, and for each input luminance value greater than or equal to the predetermined value in the luminance range, the input luminance value A dark image is generated by converting the luminance value of each pixel after scaling to the dark luminance value corresponding to the luminance value using a dark lookup table in which dark luminance values substantially equal to A dark image generation step;
Each input luminance value that is less than the predetermined value in the luminance range is associated with a bright luminance value that changes according to the change in the input luminance value, and each input that is greater than or equal to the predetermined value in the luminance range Using a bright lookup table in which a brightness value substantially equal to the input brightness value is associated with the brightness value, the brightness value of each pixel after the scaling is changed to the brightness value corresponding to the brightness value. A bright image generating step for generating a bright image by converting;
An image conversion method including an image generation step of generating the output image by mixing the bright image and the dark image. An image conversion device according to any one of claims 1 to 7, comprising:
A liquid crystal display device that displays an output image converted from an input image by the image conversion device.   The liquid crystal display device according to claim 10, wherein the display method is a vertical alignment type.   8. A program for operating the image conversion apparatus according to claim 1, wherein the image conversion program causes a computer to function as each of the above-described means.   A computer-readable recording medium on which the image conversion program according to claim 12 is recorded.