JP2014525595A - Image data processing method in image display panel - Google Patents

Abstract

  In the first mode, the image data processing method in the image display panel is visible at the first observation position (5) and image data composed of images displayed on the image display panel. A plurality of signals to be applied to the plurality of pixels of the image display panel based on the second data values in the plurality of pixels that cause a luminance change that is substantially invisible at the second observation position (3). Including a step of determining a voltage. The plurality of signal voltages applied to a plurality of pixels in a group of the plurality of pixels are a plurality of pixels in the group in which the overall luminance of the plurality of pixels in the group is specified by the image data. It is determined based on (for example, proportional) the overall luminance of the pixel. The number of the plurality of pixels in a group is variable depending on the position, and is selected by the image data and / or the second data value of the plurality of pixels in the image area of the defined group. Is done. The present invention can identify luminance redistribution across a reduced pixel group size in a main image region with sharp edges and other high resolution characteristics, and does not have high spatial resolution image characteristics. It is also possible to identify luminance redistribution across the increased pixel group size in a local area that is relatively uniform.

Description

  The present invention relates to a display device such as an active matrix liquid crystal display device capable of switching between a public display mode and a private display mode.

  Several displays that can be switched between a public display mode and a private display mode, which cost more than a standard display, are known to be easy to use and have excellent privacy performance.

  Devices equipped with such displays include mobile phones, PDAs (Personal Digital Assistants), laptop computers (laptop computers), desktop monitors, ATMs (Automatic Teller Machines), and electronic point of sale equipment (Electronic Point). of Sale (EPOS) equipment). Such a device may be noticed by an observer (eg, a driver or operator of heavy machinery) who can view an image at a certain time, such as an in-car television screen while the car is moving. It can be beneficial in cases where it is scattered and dangerous.

  Also, naturally, such as microlouver films (USRE27617 (FO Olsen; 3M 1973), US47666023 (S.-L. Lu, 3M 1988), US47664410 (R.F. Grzywinski; 3M 1988)). There are several ways to add a light control mechanism for displaying a wide viewing area. However, this and other methods, including removable optical members, require manual placement and removal of the film or other member to switch the display from public display mode to private display mode. Therefore, it is not convenient for the above switching.

  GB2413394 (Sharp), WO06132384A1 (Sharp, 2005) and GB24399961 (Sharp) disclose a method for providing an electrically switchable privacy function. In these inventions, the switchable privacy device is configured by adding one or more additional liquid crystal layers and polarizing plates to the display panel. The essential viewing angle dependence of these additional members can be changed by electrically switching the liquid crystal in a conventional manner. Devices utilizing this technology include Sharp Corporation mobile phones Sh851i and Sh902i. These methods have both the disadvantages that added optical elements increase the thickness and cost of the display.

  US20070040780A1 and GB07212555.8 describe a method for controlling the viewing angle characteristics of an LCD by switching one liquid crystal layer in two different displays that can display a high quality image to an on-axis observer. Yes. While these devices can provide a switchable privacy feature without having to increase the thickness of the display, they require complex pixel electrode designs and other manufacturing improvements for common displays.

  One example of a display device with a privacy mode function without increasing the complexity of the display hardware is the Sharp Corporation mobile phone Sh702iS. This mobile phone uses the liquid crystal mode specific angle data-luminance characteristics used in the display to create a private display mode that does not allow the viewer viewing the display from a position off center to recognize the displayed information. In the combination, adjustment of image data displayed on the LCD of this telephone is used. An important advantage of this type of method is that in the public display mode, the display is composed of a standard display without image quality degradation due to the private display mode function and is driven as a standard display. However, in the private display mode, the quality of the image displayed on the display is significantly reduced for the on-axis observer.

  The improved configuration disclosed in GB2428152A1, WO200910128A1, WO2011134209 and WO2011134208 manipulates the image data to be dependent on the second image, masking image and displays the modified image in the private display mode. When it is done, the masking image is visually recognized by an off-axis observer. These methods provide an electrically switchable public / private display with satisfactory privacy features with no additional optical elements and with minimal additional cost. All of these methods generally redistribute the brightness generated by the group of adjacent pixels to the on-axis observer while the overall brightness generated by the group maintains the same value. By taking advantage of the limited resolution of the human visual system. The driving principle of WO 2009/110128 is illustrated in FIG. 5 of WO 2009/110128. The voltage applied to the sub-pixel in the private display mode is determined by a look-up table (LUT) that receives as input the main image data, the sub-image data, and a spatial flag parameter. The space-dependent flag parameter may be a value indicating two or more pixel groups determined to be based on a spatial position. For example, odd rows of pixels in the image array may form one group, and even rows of pixels in the image array may form another group. These groups can constitute two parts of an odd and even pixel column or a grid array of pixel arrays. The function of the main image data value, the sub-image data value, and the spatial flag parameter is a function of the specific main image data value, the specific sub-image data value, and the specific value of the spatial flag parameter. The display is fixed throughout the display so that the same sub-pixel voltage is always generated regardless of the position of the pixel.

  WO201134209 and WO201134208 describe how the size of a pixel group can be increased within the redistributed brightness that increases the maximum contrast of the masking image seen by off-axis observers. However, it is also described how such an increase in pixel groups reduces the effective spatial resolution of the main image viewed by the on-axis observer. In essence, there is a toled-off relationship between the enhancement of the privacy effect and the reduction in the resolution of the main image. In WO2011134208, by carefully selecting a spatial parameter that determines whether a plurality of pixels in a group are made brighter or darker, or by temporal inversion of the spatial parameter pattern, It describes how to soften this resolution toled-off by making the eye recognize the average luminance produced by the individual pixels in the group over the frame. However, although these methods can reduce the resolution loss that can be visually recognized, this increase in the resolution loss that can be seen when there is luminance averaging over the entire group composed of the increased number of pixels. Will remain.

  Therefore, no change in the liquid crystal layer or pixel electrode shape is required from a standard display, and a public display mode and a private display mode can be realized, and a display that does not change substantially in the public display mode. Performance (brightness, contrast, resolution, etc.), while the private display mode has a strong privacy effect while minimizing the degradation of on-axis image quality, especially the resolution loss that occurs in the private display mode. There is a need for high quality LCD displays.

USRE27617 US47666023 US4764410 GB2413394 WO06132384A1 GB2439961 US20070040780A1 GB07212255.8 GB2428152A1 WO20011010128A1 WO201134209 WO2011134208

  A first aspect of the present invention provides a method for processing image data in an image display panel. In the first mode, in the first mode, the image data composed of images displayed on the image display panel and the first observation position are visible, and the second observation position is substantially visible. Determining a plurality of signal voltages to be applied to the plurality of pixels of the image display panel based on the second data values in the plurality of pixels that cause a luminance change that cannot be performed. The plurality of signal voltages applied to a plurality of pixels in a certain group among the plurality of pixels are a plurality of pixels in the certain group in which the overall luminance of the plurality of pixels in the certain group is specified by the image data. The number of a plurality of pixels in a certain group is variable depending on the position, and is defined in the region of the image of the defined group. Kicking is selected by the image data and / or said second data values of a plurality of pixels.

  As an example, the overall luminance of the pixels in the group may be proportional to the overall luminance specified by the pixels in the group by the image data, but the present invention is not limited to this.

  This mode of driving the display device provides a private (narrow field of view) display mode. The luminance change generated as a result of the second data value serves to make the generated image invisible when the received image data is input only. Based on the superimposed luminance change, an observer at a first observation position (eg, position 5 in FIG. 2) outside the intended field width in the private mode (narrow field width 6 in FIG. 2). However, the image cannot be visually recognized or only the degraded image quality can be seen. An observer at a second viewing position (eg, position 3 in FIG. 2) that is within the intended viewing width in the private mode sees little or no change in intensity. Thus, such an observer can see the original image with little or no image quality degradation (ie, the image that is generated if the only image data received is input).

  Furthermore, the present invention provides GB2428152A1, WO2009110128A1 by providing an additional processing step of appropriately and locally determining a pixel group size within the luminance redistributed by the input image content and / or the sub-image content. , Extended to the processing methods of WO201134209 and WO201134208. That is, before the signal voltage is determined, the present invention provides a step of defining a pixel group within the pixels of the image display panel. The signal voltage is then determined to provide luminance redistribution between the pixels in a group (as opposed to the pixel luminance generated by the signal voltage determined only from the received image data). . Thus, this additional step is, for example, for sub-image content that does not have high spatial resolution image characteristics or is required to achieve increased contrast through luminance averaging across the increased group size. In the region, the luminance redistribution across the increased pixel group size in the local region where the main image content is relatively uniform can be identified. Similarly, the additional process is increased without requiring the use of an increased or reduced pixel group size in the main image area with sharp edges and other high resolution characteristics. Luminance redistribution may be specified in sub-image areas where high contrast can be achieved.

  As described above, the present invention can provide improved image quality to an observer at an observation position within the intended field of view width 6, such as an observer at position 3 in FIG. 2 can be provided more efficiently to an observer at a position outside the intended visual field width, such as an observer at position 5 in FIG.

  To the accomplishment of the foregoing and related ends, the present invention includes features that will now be fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. However, except for some points in the principles of the invention employed, these embodiments are exemplary. Other beneficial and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings and the like.

In the accompanying drawings, the same member number indicates the same member or the same characteristic.
FIG. 1 is an example of a schematic configuration of a standard LCD display panel and a control device provided. FIG. 2 is a schematic configuration of a display capable of switching between public / private view modes according to the embodiment of the present invention. FIG. 3 is a plot of the available off-axis luminance space versus the on-axis luminance space generated by the display provided with the present invention when using two-pixel grouping. FIG. 4 is a plot of the available off-axis luminance space versus the on-axis luminance space generated by the display provided with the present invention when using a four pixel grouping. FIG. 5 schematically shows how a part of a conventional control device is driven in an electronic circuit in an RGB type display. FIG. 6 schematically shows how the part of the control device of the embodiment of the present invention is driven in an RGB type display. FIG. 7 shows a case where this method is applied to an example of a processing method and input image data according to the embodiment of the present invention. FIG. 8A shows the result of the processing method according to the embodiment of the present invention, and FIG. 8B shows the result of the privacy process applied to an example of input image data. FIG. 9 shows a case where this method is applied to an example of a processing method and input image data according to a further embodiment of the present invention. FIG. 10A shows the result of the processing method according to the further embodiment of the present invention, and FIG. 10B shows the result of the privacy processing applied to an example of the input image data. FIG. 11A is a diagram showing off-axis luminance output with respect to the on-axis luminance output generated by the display equipped with the present invention and having four different sub-image levels when the two-pixel grouping is applied. FIG. 11 (b) shows off-axis luminance output versus on-axis luminance output generated by a display provided with the present invention with four different sub-image levels when applying a 4-pixel grouping. FIG.

  In a first embodiment, the display is a standard LCD with a controller modified to drive the display in either a wide field (public) mode or a narrow field (private) mode. display). In general, liquid crystal displays are: 1. a backlight unit for supplying wide-angle illumination to the panel; 2. a control device which receives digital image data and outputs not only the timing pulse and the common voltage of the counter electrodes of all pixels, but also the analog signal voltage of each pixel; A pixel electrode array and an active matrix array for guiding an electric signal received from the control device to the pixel electrode are arranged on one of the two glass substrates. And a plurality of constituent parts including a liquid crystal (LC) panel.

  A schematic general configuration of a liquid crystal display control device is illustrated in FIG. 1 (Ernst Lueder, Liquid Crystal Displays, Wiley and Sons Ltd, 2001). A uniform common electrode and a color filter array film are generally arranged on the other of the two glass substrates. Between the two glass substrates, there is usually a liquid crystal layer having a thickness of 2 to 6 μm and capable of being aligned due to the presence of an alignment film on the inner surface of the two glass substrates. In each of the pixel regions of the liquid crystal layer, the two images are generated by performing predetermined optical adjustment on the light from the backlight unit and the surrounding environment by the electrically induced orientation change to generate the image. The glass substrate is generally placed between polarizing films that cross each other and other optical compensation films.

  One embodiment of the present invention is schematically illustrated in FIG. In general, the liquid crystal display control device 1 (hereinafter referred to as the LCD control device) is for the main observer 3 viewing from the normal direction (on the axis) to the display surface, in other words, resolution, As one method for optimizing the visual quality of a displayed image such as contrast, brightness, and response time, a signal voltage depending on input image data is output, particularly for the electro-optical characteristics of the liquid crystal panel 2. Is provided. The relationship between the input image data value at a certain pixel and the luminance to be visually recognized is determined by combining the effect of the data value on the signal voltage function of the display driver and the effect of the signal voltage on the luminance response of the liquid crystal panel. Based on the above display (gamma curve).

  The liquid crystal panel 2 can maintain the display gamma curve as accurately as possible for all viewing angle on-axis responses, and can provide substantially the same high quality image for the wide viewing area 4. As described above, generally, each subpixel is provided with a multi-liquid crystal domain and / or a passive optical compensation film. However, the electro-optic response of liquid crystal displays is angularly dependent, and the fact that the gamma curve at the off-axis is different from the gamma curve on the axis is an essential characteristic of liquid crystal displays. . Unless this is a contrast reversal, a large color shift, or a contrast decrease, it is generally not a defect that is clearly visible in an image viewed by an off-axis observer 5.

  When the device of the present embodiment is driven in the public mode, a set of main image data 6 constituting one image is input to the control device 1 in each frame period. Then, the control device outputs a set of signal data voltages to the liquid crystal panel 2. Each of these signal voltages is guided to the corresponding pixel electrode by the active matrix array of the liquid crystal panel, and the collective electro-optic response of the pixels is such that the liquid crystal layer produces the image. To do.

  The controller has one function of input pixel data value relative to output pixel data voltage (eg, stored in a look-up table) that can be applied to processing all pixels. In some cases, different look-up tables can be used for the red, green and blue subpixels of the display, but the output voltage based on the spatial location of the image data in the image or the pixel electrodes in the display There is no change in the function of the input data value for. Since substantially the same image is visually recognized by the observer 3 on the axis and the observer 5 off the axis, it can be said that the display is driven in the wide-field mode.

  When the device is driven in the private mode, the control device 1 has two main image data 7 constituting the main image and sub image data 8 constituting the sub image in all frame periods. An image data set is input.

  Then, as described above, the control device outputs a set of signal data voltages, which is one data voltage of each pixel in the liquid crystal panel. However, here, the control device (display controller) uses an extended look-up table (LUT), and the output signal data voltage of each pixel in the liquid crystal panel constituting the combined image is the main image. 7 and the sub-image 8 depend on the data value of the corresponding pixel (related to the spatial position in the image). The output data voltage at each pixel depends on a third parameter determined by the spatial position of the pixel in the display and the main image content and / or sub-image content at that image position. Therefore, the extended look-up table (LUT) stores an output data value in which all of the input main image data value, the input sub-image data value, and the spatial flag parameter are combined.

  Thus, in each frame period, the controller receives two images rather than one, stores them in a buffer, uses the function to set the data values of the two input images to one output voltage per pixel, The function is changed from the standard liquid crystal control device so as to incorporate a third parameter having a spatial dependency in this function. In such a case, the function of the input image data with respect to the output pixel voltage no longer matches at all pixels in this display or at all sub-pixels of the same color component.

  The third parameter having spatial dependency may be a flag value indicating classification of a pixel determined to be based on a spatial position into two or more pixel types. For example, it can be said that odd-numbered rows of pixels in the image array form one class, and even-numbered rows of pixels in the image array form another one class. These classes can constitute two parts of an odd and even pixel column or a grid array such as the above pixel array. If more than two categories are used, the spatial flag parameter can have as many values here as there are categories. The number of output data values or signal voltages in each combination of main image data value and sub-image data value can be increased accordingly. Pixels or sub-pixels of the same color type in the display can be thought of as a group, each group containing one or more pixels or sub-pixels of each classification type. The size of each pixel group, and thereby the number of different values of the spatial flag parameter that can be in an image area, can be varied in different image areas and the main image content and / or sub-values in each area. Depending on the image content, it can be determined in each image region.

  The output voltage from the control device 1 minimizes the deterioration of the main image quality with respect to the liquid crystal panel 2 and, when viewed by the main observer 3, is a combined image that is the main image. Is displayed. However, the off-axis observer 5 has different gamma curve characteristics of the liquid crystal panel, so that the off-axis observers may see the sub-image that blurs and / or degrades the main image. The viewer who is most prominently visible and within a conical limited angle centered on the normal of the display is ensured to view the main image information.

  The modified controller accomplishes this by changing the brightness of individual subpixels within the same color type subpixel group determined by the spatial flag parameter assignment. The individual brightness is the same brightness as the brightness specified by the main image data seen by the on-axis observer 3 or the overall brightness from the brightness specified by the main image data. While maintaining the proportional luminance or the average luminance, the luminance distribution within the group is changed and changed to be larger or smaller.

  For example, two sub-pixels with 50% luminance can have luminance that is changed so that the luminance of each sub-pixel is the same and in the opposite direction. Therefore, the two subpixels maintain the same average brightness for the on-axis observer, but for the observer 5 off the axis, the average brightness of the two subpixels is It changes according to the degree to which the change in luminance is increased in the two sub-pixels. To illustrate this effect, in FIG. 3 all possible combinations of two data values are used to deviate from the normalized axis created by the two pixels of a typical VAN mode liquid crystal display. Average brightness is plotted against average brightness on the normalized axis. This figure shows the existence of a possible width of the average brightness at a given off-axis average brightness (excluding maximum brightness and minimum brightness) at locations off-axis. Due to the viewing angle characteristics of VAN mode displays, mid-level data values generally produce higher brightness associated with the maximum at off-axis angles than on-axis. The pixel pairs to which the two data values are applied have the same shape, and the upper edge of the available space when it is off axis with respect to the luminance point on the axis is the lower green of the available space. Line up along the section. Then, the combined luminance in the pixel pair concentrates the luminance as much as possible on one pixel in the pixel pair (in other words, the data value is the most different, and in an 8-bit display, One of the two pixels is 0 or 255).

  As shown in FIG. 3, where the on-axis luminance point is 50%, the available space surrounding the luminance value when off-axis is the widest, so it is available for the sub-image. The contrast is the highest. At this point, for the off-axis observer, the combined brightness is reduced by almost half, while for the on-axis observer, the overall appearance is maintained unchanged. Each of the two pixels that produce 50% luminance on the axis can be replaced with two pixels, one pixel being fully on and the other one being completely off. This makes it possible to generate a sub-image with a contrast ratio of approximately 2: 1 in the main image area with an on-axis brightness of 50%.

  The amount of luminance redistribution that can be imposed on each pixel group, ie, the degree of change that can be achieved in the viewing brightness of the group with respect to an off-axis observer (in other words, the contrast of the sub-image) Depends on the average brightness of the group and the number of pixels in the group. FIG. 4 illustrates the average luminance at a location off the equivalent axis with respect to the on-axis luminance in a pixel group of four pixels rather than two pixels. In particular, when the on-axis luminance points are 25% and 75%, the volume available in the off-axis location is expanded with respect to the on-axis luminance space, and the off-axis luminance control, that is, the sub-image. It can be seen that contrast can be realized.

  Therefore, the present invention provides that the number of pixels in the group to which the luminance is redistributed is individually determined in each local image area based on an analysis of the main image content and / or the sub-image content in that area. Suggest that you may decide. The main merit of such an applicable pixel group size selection process is that, for the on-axis observer, the image resolution to be viewed is maintained, and at the same time, for the off-axis observer, the image It is to maximize the contrast. When the luminance generated by the group is redistributed to the observer on the axis at the maximum (in other words, the luminance is concentrated on the smallest possible number of sub-pixels in the group), A large group size allows an increase in sub-image contrast and an improvement in privacy strength, but the main image resolution shows a decrease with a larger group size. Therefore, the pixel group size selection step sacrifices some of the sub-image contrast in these image regions for the region of the main image having high resolution characteristics or the region corresponding to the low-contrast required region of the sub-image. Thus, luminance redistribution within a smaller group of adjacent pixels allows the original resolution to be maintained higher. Similarly, the pixel group size selection step is performed in a larger group of adjacent pixels for a relatively uniform main image area or an area corresponding to the sub-image area where high contrast is desired. The luminance redistribution at can have increased privacy strength. For purposes of this specification, the term “high spatial resolution” may be an image characteristic that occurs on a scale similar to the image group size that can be selected. For example, in the embodiments described below, certain image characteristics that cause significant changes in the image data over the entire sampled 4 × 2 block area may be considered “high resolution”. Similarly, “significant changes” may be considered to mean data values that differ significantly from the proposed threshold in these embodiments.

  In this way, the present invention provides additional processing steps for main image content and / or sub-image content depending on the applicable pixel group size selection, thereby enabling the switching disclosed in GB2428152A1, WO200910128A1, WO201134209 and WO2011134208. Benefiting a method for producing a possible privacy mode, such an application of the present invention is combined with cited references. In addition, the present invention optimizes the visible resolution of the main image and the contrast of the sub-image, and at the same time performs an arrangement that is considered advantageous and the pixel group size selection step in order to minimize resource requirements. Concentrate on.

  In a preferred embodiment, the pixel group size selection step is based solely on the analysis of the main image content and comprises a continuous analysis of each 2 × 2 block of similar color type subpixels in the main image. The two similar color type sub-pixels are directly adjacent to one side of the 2 × 2 block in the horizontal direction (as shown by the block shown in the dotted line in FIG. 7). Here, the size of the group of similar color subpixels in the selected adjacent mixed color pixel is simply referred to as “pixel group”. This can also be reflected in the facts of the other embodiments, where the image elements in a pixel group whose group size has been determined and whose luminance has been redistributed are the same pixels or adjacent color pixels or all adjacent color pixels. Of which can be different color subpixels. FIG. 6 shows an improved image data processing method of this embodiment by outputting a pattern in which the space flag parameter for determining a block has a fixed pixel classification value. This improved image data processing method of this embodiment analyzes the main image content over a certain area (if the main image pixel data values are continuously supplied to the LCD controller). Can be the pixel group size selection step of outputting a customized spatial flag parameter pattern in the image area.

  In the pixel group size selection step, the main image data value that exceeds a predetermined threshold in 8 pixels in the 2 × 2 block including 4 adjacent pixels, for example, a maximum value of 255 in a display of 8 bits per color Check if there are more than 150 main image data values. In the pixel group size selection step, it is also determined whether the difference between the largest data value and the smallest data value used for the eight pixels is larger than a predetermined threshold, for example, 50. These steps serve as means for easily determining whether there are bright pixels or high resolution characteristics in the 8-pixel region. If the threshold value is exceeded in any of the threshold tests, a 2-pixel classification pattern of spatial parameters is used for the 2 × 2 block that forms the central 4 pixels of the 8 samples. In other words, One classification is given to two of the four pixels, and another classification is given to the remaining two pixels. If none of the threshold tests exceed the threshold, a 4 pixel group pattern is applied to the 2 × 2 block forming the central 4 pixels of the 8 samples, in other words, the 4 pixels Each is given an individual classification value. This pixel group size selection method is illustrated in FIG. Since the pixel group size in the 2 × 2 block in the pixel has been determined, this process is moved to the next 2 × 2 block in the pixel and repeated. This process continues until each 2 × 2 block in the image has a pixel classification assigned to it, and this process is performed for each frame of main image input data.

  In a preferred embodiment, if the threshold is exceeded in any of the threshold tests, the 2 × 2 block in the pixel is assigned [upper left, upper right, lower right and lower left]. A pattern of classification values [1, 2, 1, 2] corresponding to each pixel is assigned. If none of the threshold tests exceed the threshold, the 2 × 2 block has a classification value [3, 6, 4, 5] that depends on the position of the 2 × 2 block in the image. Alternatively, a classification pattern of classification values [4, 5, 3, 6] is assigned. The pixel classification value is used to select one of the six output data values. In the lookup table (LUT), the combination of the main image input data value and the sub image input data value is Selected for pixel output. Therefore, the output data value in the lookup table is that the output value of the combination of the pixel classification values 1 and 2 is the desired average on-axis luminance and Calculated to produce off-axis average brightness. The same applies to output values of combinations of pixel classification values 3, 4, 5 and 6. If the look-up table output value of pixel class 1 is larger than the look-up table output value of pixel class 2 and the block of the [1, 2, 1, 2] output pattern is repeated, the output image is brighter A grid pattern of pixels and darker pixels is formed. If the output data value in the classification value [3, 4, 5, 6] is set to decrease in the order from 3 to 6, [3, 6, 4, 5] or [4, 5 , 3, 6] pattern generates a thin grid pattern having the same pattern as the [1, 2, 1, 2] pattern. In other words, the position of the brightest pixel matches in each pattern. This is because a clear boundary between the two-pixel grouping and the four-pixel grouping can be visually recognized in the output image because it does not result in the brightest pixels in the output being positioned adjacent to each other. There are advantages.

  If the two possible output patterns [3, 6, 4, 5] and [4, 5, 3, 6] as the 4-pixel group output are even more advantageous, in the main image area of 25% luminance One pixel in the 4-pixel output set can be brighter than the other three pixels, and in this case the position of the bright pixel in the block is improved for the observer on the axis. It can be changed so that it can be provided. Further, the two output patterns have the property of maintaining the brightest output pixel position (types 3 and 4) in the same pattern as the brightest output pixel position in the [1,2,1,2] pattern output. Have. This once again ensures that the on-axis observer can seamlessly see the transition between the two-pixel group and the four-pixel group.

  7 and 8 illustrate these processing methods and the results. FIG. 7 shows an overview of the pixel group size selection method of the preferred embodiment and this method when applied to a main image composed of blurred bright diagonal lines on a darker background (channels of 8 bits per color). In order to show the effect applied to the display, main image data values from 0 to 255 are used). FIG. 8A shows the result of the pixel group size selection step of assigning a pixel type classification to each pixel. As shown in the figure, each 2 × 2 block in the vicinity of the bright line in the pixel is assigned the classification pattern [1, 2, 1, 2], and 2 × 2 in each other portion. The classification pattern [3, 6, 4, 5] or [4, 5, 3, 6] is assigned to the block. FIG. 8B shows the output privacy processing in the same input main image area as above and the corresponding sub-image content that causes the luminance generated by each group in which the luminance is concentrated on as few pixels as possible. The result of pixel class assignment in the rendered image is shown. As shown in the figure, this is a result of assigning to a group of four pixels, and only one pixel in the group (location to which class 3 is assigned) is On, which is provided by this. The overall luminance of the four pixel group forms the input image. In the vicinity of the brighter line, the pixel group size selection step detects higher resolution characteristics and applies a specified pixel group of size 2, so that a 2 × 2 light / dark grid pattern is generated. . For pixels assigned class 1, the output data value is higher than the input data value (61 and 191 inputs are increased to 120 and 255, respectively), whereas for pixels assigned class 2 These data values are reduced to zero.

  As can be seen from this example, the privacy process interrupts the continuity of the bright diagonal line at the pixel scale, but rather than applying luminance redistribution in the 4-pixel group over the entire image area. The appearance of this line is significantly better preserved. Similarly, in a darker background, the concentration of luminance on only one pixel in each of the four pixels is compared to the standard method in which the luminance is redistributed only between pixel pairs. Improve the privacy strength.

  In a further embodiment, the demand on the pixel buffer memory is reduced by analyzing each 4 × 1 pixel block of the input main image data rather than each 2 × 2 block. Since the main image data is typically read continuously from left to right, one row at a time, into the display controller, the requirement to analyze pixel data on different rows is the pixel This means that the memory buffer needs to have a capacity capable of storing at least all rows of pixel data. By using a 4 × 1 analysis canel, this requirement can be reduced to only 4 pixels.

The pixel group size selection process in FIG. 7 is as follows.
(1) In each 2 × 2 block in the main image in each color channel in the main image, (2) 1 having a data value greater than threshold 1 in the 4 × 2 block centered on the 2 × 2 block If there are pixels,
(3) Or, in the above 4 × 2 block, when the difference between the highest data value and the lowest data value is larger than the threshold value 2,
(4) If so, apply a 2 × 2 pixel group in the 2 × 2 block. (5) If not, apply a 1 × 4 pixel group in the 2 × 2 block. The main image data in one color channel of the main image at a time is analyzed every 4 × 1 blocks at a time. In the previous embodiment, in order to determine the classification, adjacent pixels are also analyzed in addition to the four pixels in the 2 × 2 block having the determined classification type. Only pixels having the classified type are analyzed.

  Also, as in the previous embodiment, is there a pixel having a data value that exceeds the first threshold value, and whether the difference between the largest data value and the smallest data value in the block exceeds the second threshold value? 4 pixels in the current block are analyzed. If any of these threshold conditions is exceeded, the 4 × 1 block of pixels depends on the position of the 4 × 1 block, [leftmost, left from center, right from center, rightmost] A pattern of classification values [1, 2, 1, 2] or [2, 1, 2, 1] corresponding to each of the pixels is assigned. If the test does not exceed any of these threshold conditions, the 4 × 1 block contains a classification value [3, 6, 4, 5] or a value that depends on the position of the 4 × 1 block of the image. A pattern of [5, 4, 6, 3] or [4, 5, 3, 6] or [6, 3, 5, 4] is assigned. This means that after processing 4 or more rows, the area where the threshold test did not exceed these threshold conditions would be the same pixel classification pattern as that generated in the previous preferred embodiment. Guarantee. 9 and 10 show the processing outline, pixel classification result, and obtained privacy processing result equivalent to those in FIGS. 7 and 8 in the steps of this embodiment. It can be seen that the method of this embodiment produces a bright diagonal characteristic very similar to the preferred embodiment. Also, the method of this embodiment generates an output image similar to the preferred embodiment for light and dark vertical lines and other sharp parts, but for the sharp horizontal line type feature, the single line kernel Therefore, it will be indistinguishable from a plain background area. The above steps of this embodiment can in this case produce an output that is significantly different from the preferred embodiment.

  In both of the previous examples, the threshold test indicates that a 2 × 2 or 4 × 2 block of pixels analyzed in each step is a size 2 output group at the edge where the brightness characteristic has fallen in the sampling kernel. Note that it was not specified, but was specified to identify the center pixel and the brightest pixel. This is because two or less horizontally adjacent 2 × 2 blocks or one 4 × 1 block are specified to have a pixel group of size 2 instead of size 4, and the above sharpness is sacrificed at the expense of privacy. The result is to minimize the area required to save the part. However, this is not the case and it may be advantageous to have the threshold test provided, and a wider reduced pixel group size area is produced around the sharp part. This is indeed the case when the process parameters are tuned to produce the preferred output image pattern in the typical main image content of the display.

In FIG. 9, the image group size selection process is as follows.
(1) In each 4 × 1 block in the main image in each color channel in the main image, (2) When there is one pixel having a data value greater than the threshold value 1 in the 4 × 1 block,
(3) or when the difference between the highest data value and the lowest data value in the 4 × 1 block is larger than the threshold value 2,
(4) If so, apply a 2 × 2 pixel group in the 4 × 2 block. (5) If not, apply a 1 × 4 pixel group in the 4 × 1 block. A form has been described using two threshold type tests to perform the pixel group size selection step, but an image content analysis method that creates the desired distinction between image regions that are optimal for a particular pixel group size May be used.

  In a further embodiment, both the main image content and the sub-image content are analyzed in each image region, rather than the main image content in each region being analyzed, which affects the pixel group size selection step. Sampled. In this way, a main image area that does not have a sharp portion that can be subject to a four-pixel grouping based only on main image analysis, if the sub-image content of that area is used with an increased pixel size grouping. However, if there is no special advantage, it may have a two-pixel grouping applied instead. This can be the case for a uniformly bright sub-image area. This method has a certain pixel pitch and a typical viewing distance, which is a means by which the coarse pixel pattern generated by the four pixel group allows the on-axis observer of the four pixel grouping region to see an unclear or rough texture. It can be advantageous for use in a display. This is because it is beneficial to use a region limited to the increased sub-image contrast area.

  In a further embodiment, the sub-image content is used rather than the main image content in each region as an analysis target that affects the pixel group size selection step. This can be advantageous in that the computational resource requirements for applying the group size selection process can be reduced.

  In further embodiments, as with any of the above embodiments, certain steps are applied, but from any number of different group sizes, rather than simply selecting between 2 or 4 pixel group sizes. Allow selection. For example, a group of 2, 3 and 4 or a group of 2, 4 and 8 can be selected. This can be advantageous in the future as it redistributes luminance within a pixel group size greater than 4 without allowing the viewer to see a coarse pattern of bright and dark pixel arrays when higher ppi displays are generalized. . This process may also have the ability to specify one group size (in other words, there is no luminance redistribution). This can be advantageous in low ppi displays where some luminance redistribution around the sharp part is too disturbing to make the clear part invisible.

In a further embodiment, in addition to the pixel group size selection step, the display control device includes a further step indicating the case of the pixel group size selection step of changing the output from one adjacent pixel group to another pixel group. include. The size of the pixel group determines a region of off-axis brightness that can be generated by the group at a given on-axis brightness, so the pixel group in an image region where the sub-image value is constant Changes in size can cause a change in viewing brightness for an off-axis observer. This effect shown in FIG. 11 shows off-axis brightness values relative to on-axis brightness values generated by the privacy display as a function of main image input brightness at four sub-image levels. The sub-image level is calculated so as to cover the entire usable width of the off-axis luminance in the same interval process. FIG. 11A shows the resulting output in the two-pixel grouping, and FIG. 11B shows the resulting output in the four-pixel grouping. In the 4-pixel group process, there is a mismatch of off-axis brightness level when the pixel group size changes due to the available extended off-axis brightness width, especially at the darker sub-image level. I understand. These visible boundaries can damage the sub-image pattern. Therefore, this step of this embodiment may include means for modifying the input sub-image data or using a further extended privacy processing look-up table set to mix or smooth this change. . (The main purpose of the sub-image is to make the main image invisible at an observation position outside the private visual field width (as in the observation position 5 in FIG. 2). (Images may show logos, personal images, etc., and in such embodiments it may be preferred that the sub-image be reproduced as accurately as possible.)
Although the present invention has been described with respect to particular embodiments or embodiments, it will be understood that changes and modifications equivalent to those skilled in the art can occur to others upon reading and understanding this specification and the accompanying drawings. In particular, with respect to the various functions performed by the elements described above (parts, assemblies, devices, compositions, etc.), the terms used to describe the elements (including part numbers for means) are the elements described above. Unless otherwise indicated for an element that performs a special function, in the example embodiments of the present invention, even though it is not structurally equivalent to the disclosed structure that performs that function (in other words, it is functional Is equivalent). Furthermore, while particular features of the invention have been described above with reference to only one embodiment or more than one embodiment, such may be desirable, advantageous, or for special applications, such as A feature can be combined with one or more other characteristics of other embodiments.

  A first aspect of the present invention provides a method for processing image data in an image display panel. In the first mode, in the first mode, the image data composed of images displayed on the image display panel and the first observation position are visible, and the second observation position is substantially visible. Determining a plurality of signal voltages to be applied to the plurality of pixels of the image display panel based on the second data values in the plurality of pixels that cause a luminance change that cannot be performed. The plurality of signal voltages applied to a plurality of pixels in a certain group among the plurality of pixels are a plurality of pixels in the certain group in which the overall luminance of the plurality of pixels in the certain group is specified by the image data. The number of a plurality of pixels in a certain group is variable depending on the position, and is defined in the region of the image of the defined group. Kicking is selected by the image data and / or said second data values of a plurality of pixels.

  As an example, the overall luminance of the pixels in the group may be proportional to the overall luminance specified by the pixels in the group by the image data, but the present invention is not limited to this.

  This mode of driving the display device provides a private (narrow field of view) display mode. The luminance change generated as a result of the second data value serves to make the generated image invisible when the received image data is input only. Based on the superimposed luminance change, an observer at a first observation position (eg, position 5 in FIG. 2) outside the intended field width in the private mode (narrow field width 6 in FIG. 2). However, the image cannot be visually recognized or only the degraded image quality can be seen. An observer at a second viewing position (eg, position 3 in FIG. 2) that is within the intended viewing width in the private mode sees little or no change in intensity. Thus, such an observer can see the original image with little or no image quality degradation (ie, the image that is generated if the only image data received is input).

  Furthermore, the present invention provides GB2428152A1, WO2009110128A1 by providing an additional processing step of appropriately and locally determining a pixel group size within the luminance redistributed by the input image content and / or the sub-image content. , Extended to the processing methods of WO201134209 and WO201134208. That is, before the signal voltage is determined, the present invention provides a step of defining a pixel group within the pixels of the image display panel. The signal voltage is then determined to provide luminance redistribution between the pixels in a group (as opposed to the pixel luminance generated by the signal voltage determined only from the received image data). . Thus, this additional step is, for example, for sub-image content that does not have high spatial resolution image characteristics or is required to achieve increased contrast through luminance averaging across the increased group size. In the region, the luminance redistribution across the increased pixel group size in the local region where the main image content is relatively uniform can be identified. Similarly, the additional process is increased without requiring the use of an increased or reduced pixel group size in the main image area with sharp edges and other high resolution characteristics. Luminance redistribution may be specified in sub-image areas where high contrast can be achieved.

  As described above, the present invention can provide improved image quality to an observer at an observation position within the intended field of view width 6, such as an observer at position 3 in FIG. 2 can be provided more efficiently to an observer at a position outside the intended visual field width, such as an observer at position 5 in FIG.

  When the number of pixels in a group is selected according to the image data, the method identifies one or more regions of the image that have high spatial resolution characteristics, and a small group in the identified region. The size is selected. The use of a small group size keeps the image at the original resolution to a higher degree. Therefore, it is preferred to use a small group size in the above image regions with high spatial resolution or other image characteristics, whose appearance may be degraded by luminance redistribution between groups of larger pixels.

  The method determines the pixel voltage in each individual N pixel group in the image such that luminance redistribution is obtained within all N pixels of the group or within the M group of N / M pixels. May be configured.

  By determining the pixel voltage so that luminance redistribution is obtained within all N pixels of a group, the pixel voltage at the pixels within the group is determined so that one pixel of the group has the maximum luminance. It is good also as a structure. Concentration of luminance on only one pixel of a group of pixels improves the intensity of the disturbing effect caused by the luminance change and thus provides a more improved privacy effect.

  N can be 4 and M can be 2. However, the present invention is not limited to luminance redistribution within M groups, each including the same number (in other words, N / M) of pixels. For example, if N = 8, the pixel is divided into one group of 4 pixels or 2 pixels instead of dividing the pixel into one group of 4 pixels or 4 groups of 2 pixels. Can be divided into two groups.

  In the method, the second pixel in which the arrangement of brighter pixels and darker pixels generated in the first region of the image having the first pixel group size is different from the first pixel group size in the displayed image. The pixel voltage may be determined so as to be in phase with the arrangement of brighter pixels and darker pixels generated in the second region of the image adjacent to the first region having the group size. This can prevent what is seen at the boundary between the regions of the image having different pixel group sizes.

  This method may be configured to define one or more groups of pixels in the block based on image data of the pixels in the block in the block of pixels.

  In the pixel block, one or more groups of pixels in the block are defined based on image data in pixels in the block and at least one pixel outside the block. May be.

  The method includes the first observation position at a pixel at a boundary between a first image region having a first size group and a second image region having a second size group different from the first size. The pixel voltage may be changed so as to coincide with the luminance level visually recognized in step (b). Otherwise, in the image viewed at the first observation position, there is a discrepancy between the luminance levels of the pixels in the first image region and the pixels in the second image region that cause the visible boundary to appear. To prevent.

  The signal voltage applied to the pixels in a certain pixel group may be determined so that the overall luminance of the group and the overall luminance specified in the pixels in the group by the image data are the same.

  The second observation position may be a substantially on-axis observation position.

  In the second mode, the method applies from the received image data to the pixels of the image display panel so as to generate an image that can be viewed at both the first observation position and the second observation position. The signal voltage to be determined may be determined. This mode provides a wide field of view (public) mode. Switching between the first mode (private) and the second mode (public) can be made possible by using, for example, a privacy mode On / OFF signal shown in FIG.

  According to a second aspect of the present invention, there is provided a display panel control circuit applicable to the method of the first aspect.

  According to a third aspect of the present invention, there is provided a display comprising the control circuit according to the second aspect of the present invention, which is applied and used for outputting the determined signal voltage to the display panel, and the display panel. provide.

  The display panel may be a liquid crystal display panel.

  According to a fourth aspect of the present invention, there is provided a display panel applied to execute the method of the first aspect.

  A fifth aspect of the present invention provides a computer readable medium comprising instructions that, when executed on a processor, cause the processor to perform the method of the first aspect.

  The embodiment of the present invention can be applied to various display devices, and the user is advantageous from the privacy function provided in a general wide-field display for use in a scene where privacy is required. obtain. Examples of such devices include mobile phones, PDAs (Personal Digital Assistants), laptop computers (laptop computers), desktop monitors, ATMs (Automatic Teller Machines) and electronic point of sale equipment (Electronic Point of Interest). Sale (EPOS) equipment). Such a device may be noticed by an observer (eg, a driver or operator of heavy machinery) who can view an image at a certain time, such as an in-car television screen while the car is moving. It can be beneficial in cases where it is scattered and dangerous.

DESCRIPTION OF SYMBOLS 1 LCD controller 2 Liquid crystal panel 3 Main observer 4 View angle width of main image in public mode 5 Off-axis observer 6 View angle width of main image in private mode 7 Input main image data 8 Input sub-image data

Claims (17)

A method of processing image data in an image display panel,
The image data processing method is as follows:
In the first mode, image data composed of an image displayed on the image display panel and luminance that is visible at the first observation position and cannot be visually recognized at the second observation position. Determining a plurality of signal voltages to be applied to the plurality of pixels of the image display panel based on the second data values in the plurality of pixels causing the change,
In the above process,
The plurality of signal voltages applied to a plurality of pixels in a group of the plurality of pixels are a plurality of pixels in the group in which the overall luminance of the plurality of pixels in the group is specified by the image data. The number of pixels in a group is determined based on the overall luminance of the pixels, and is variable depending on the position, and the image data of the pixels in the region of the image of the group defined and / or Alternatively, the image data processing method is selected according to the second data value. The number of pixels in a group is selected by the image data,
The method includes identifying a region of an image that has high spatial resolution characteristics and that is defined by one or more of the image data, and selects a small group size in the identified region of the image. The image data processing method according to claim 1, further comprising: a step.   The method determines the pixel voltage in each individual N pixel group in the image such that luminance redistribution is obtained within all N pixels of the group or within the M group of N / M pixels. The image data processing method according to claim 1, wherein the image data is processed as described above.   The method of determining the pixel voltage so as to obtain luminance redistribution among all N pixels of a group is to determine the pixel voltage at the pixels in the group so that one pixel of the group has the maximum luminance. The method of processing image data according to claim 3, further comprising:   5. The image data processing method according to claim 3, wherein N is 4 and M is 2.   In order to prevent the method from being viewed at the boundaries of regions having different pixel group sizes, the brighter pixels generated in the first region of the image having the first pixel group size in the displayed image and The arrangement of lighter and darker pixels generated in a second region of the image adjacent to the first region having a second pixel group size that is different from the first pixel group size. The image data processing method according to claim 1, wherein the pixel voltages are determined so as to have the same phase.   7. The method according to claim 1, wherein in the block of pixels, one or more groups of pixels in the block are defined based on image data of the pixels in the block. The image data processing method according to claim 1.   The method includes defining, in a block of pixels, one or more groups of pixels in the block based on image data in pixels in the block and at least one pixel outside the block. The image data processing method according to any one of claims 1 to 6.   The method includes the first observation position at a pixel at a boundary between a first image region having a first size group and a second image region having a second size group different from the first size. The image data processing method according to claim 1, wherein the pixel voltage is changed so as to coincide with a luminance level visually recognized in step 1.   In the method, the signal voltage applied to the pixels in a certain pixel group is the same as the overall luminance of the pixels in the group and the overall luminance specified in the pixels in the group by the image data. The image data processing method according to claim 1, wherein the image data processing method is determined.   11. The image data processing method according to claim 1, wherein the second observation position is substantially an observation position on an axis. 11.   In the second mode, the method applies the received image data to the pixels of the image display panel so as to generate an image that can be viewed at both the first observation position and the second observation position. The image data processing method according to claim 1, wherein a signal voltage to be determined is determined.   A display panel control circuit for performing the method according to claim 1. A display comprising the control circuit according to claim 13 and a display panel,
The control circuit is a display for outputting the determined signal voltage to the display panel.   The display according to claim 14, wherein the display panel is a liquid crystal display panel.   A display panel for performing the method according to claim 1.   A computer readable medium containing instructions, which when executed by a processor, causes the processor to perform the method of any one of claims 1-12.

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