JP4044347B2 - Driving method of liquid crystal display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drive circuit for a TN liquid crystal (twisted nematic liquid crystal) liquid crystal display device and signal processing of a video signal input to the liquid crystal display device. The present invention relates to a signal processing method of a liquid crystal display device capable of enlarging control of angular characteristics.
[0002]
[Prior art]
The TN liquid crystal system, which is often used in liquid crystal TVs, has a complex field of view due to various birefringence effects depending on the direction and angle of light passing through the liquid crystal layer due to the different refractive index method and twisted orientation of the liquid crystal For example, in general, the entire screen becomes whitish at an upward viewing angle, the entire screen becomes dark at a downward viewing angle, and light and darkness are reversed in a low-luminance portion of an image.
[0003]
For such viewing angle characteristics, many techniques have been developed for widening the viewing angle with respect to brightness, hue, contrast characteristics, gradation characteristics, and the like by various methods.
[0004]
As such technology, improvements to the liquid crystal panel itself and those using optical members are very common, but the TFT process and the liquid crystal panel process are not complicated, resulting in a decrease in yield and an increase in cost. As a method that does not, a technique for widening the viewing angle only by signal processing of an external circuit is also shown. This utilizes the viewing angle dependence of transmittance characteristics (hereinafter referred to as VT characteristics) with respect to the applied voltage of the liquid crystal cell, and a plurality of gradation voltage conversion characteristics (hereinafter referred to as γ characteristics) for input signals are prepared. In this technique, a plurality of characteristics are visually combined to improve the viewing angle characteristics by driving the liquid crystal while performing this switching control at a predetermined interval. For example, Japanese Patent Laid-Open No. 7-121144 “Liquid Crystal Display” Device ", Japanese Patent Application Laid-Open No. 9-90910" Liquid crystal display device driving method and liquid crystal display device "and the like.
[0005]
An example of such a conventional wide viewing angle liquid crystal display device by external signal processing is shown in FIG. In FIG. 14, γ conversion circuits γ1 and γ2 having a plurality of different γ characteristics with an RGB image signal as an input, and the γ characteristics are switched and controlled every n frames (n is a natural number, n ≧ 2) of the image signal. And the liquid crystal is driven according to the output of the γ conversion means. As a γ characteristic switching pattern, as shown in FIG. The corresponding pixels are configured to apply display signal voltages corresponding to the same γ characteristics and having different polarities. Here, as shown in FIG. 16, the two gamma characteristics are optimized so that different viewing angles become the optimum field of view. For example, γ1 is optimized for the upper visual field 10 °, γ2 is optimized for the lower visual field 10 °, and the γ characteristics are fixed. Then, by modulating with the switching pattern, the operation is performed so as to widen the optimum gradation characteristic by about 10 degrees up and down.
[0006]
  As described above, in the conventional technique, as a technique for expanding the viewing angle characteristic (improving the viewing angle characteristic) only by the signal processing of the external circuit, a plurality of fixedly set plural techniques are used.γ specialA method for modulating the characteristics is disclosed as a technique.
[0007]
[Problems to be solved by the invention]
However, in the conventional example, the γ characteristics having a plurality of different characteristics set to widen the viewing angle are spatiotemporally modulated. However, this is performed by modulating the γ with the RGB trio as one unit (one set). Therefore, in the case where the degree of modulation of γ is increased in order to obtain a certain viewing angle improvement effect (for example, when the γ1 and γ2 shown in FIG. 16 are switched and modulated, the γ characteristics of γ1 and γ2 are large), Due to the modulation control, the modulation pattern is recognized as a dot-like pattern. Therefore, in reality, it is assumed that the present invention can be applied to a liquid crystal panel having a minimum number of pixels of, for example, about VGA (640 × 480 pixels) or more, or a resolution of about 80 PPI or more.
[0008]
Even when applied to a liquid crystal panel having a certain level of resolution, depending on the method of modulation and the image to be displayed, the edge portion of the image (especially the edge portion of the diagonal line) has a rough edge. (If it is diagonal, the edges will be stepped) and the image will appear smooth. Further, there are cases where fine characters, lines, etc., become faint characters, or a one-pixel line looks like a dotted line.
[0009]
Furthermore, in order to solve such problems, it is conceivable to perform modulation in units of RGB pixels, but in this case, depending on the modulation pattern, there may be adverse effects, and for fine characters etc. In some cases, a false color is generated, resulting in an image different from the original image.
[0010]
In this way, in the technology for improving the viewing angle characteristics by signal processing, it is important to suppress the adverse effects on the image caused by the trade-off with the improvement items and effects of the viewing angle improvement. It can be said that this greatly depends on the state of the input image signal. However, in the conventional example, there is no disclosure of a technique for adaptively controlling such adverse effects according to an input video signal.
[0011]
The second problem to be solved by the present invention is that, in the conventional example, the modulation degree of γ is configured to always use a fixed value after setting. Therefore, depending on the image, the effect is small and the harmful effect is greater. It may be a result. In reality, depending on the state and characteristics of the image of the video signal to be displayed, it is easily affected by viewing angle characteristics, in other words, images that require improvement, and conversely, they are relatively less affected by viewing angle characteristics. For example, there are images that are less effective and more harmful, but they are not adaptable to this (image).
[0012]
The third problem to be solved by the present invention is that, in such a technique for improving the viewing angle characteristic by γ modulation, the equivalently synthesized γ characteristic may change from the original γ characteristic, As a result, as compared with the case where the viewing angle enlargement process is not performed, the image quality in the front direction where the image quality should not be changed is changed.
[0013]
The present invention has been made in view of improving the above-mentioned problems in the technology for improving the viewing angle characteristics by such signal processing and drive control. As a result, the resolution is lower. An object of the present invention is to make it possible to apply such a technique to a liquid crystal panel. In addition, adaptive control is performed according to the input signal source and the state of the video, making the dot pattern due to the modulation pattern less noticeable, and smoothing the edges to reduce blurring of characters and lines and false colors This is intended to improve the resolution and improve the appearance. Another object of the present invention is to provide a good display that effectively obtains the effect of improving the viewing angle by suppressing adverse effects related to image quality in accordance with the state of the image to be displayed.
[0014]
[Means for Solving the Problems]
  In order to solve such a problem, the present invention is a drive device for a liquid crystal display device, and is an RGB independent γ conversion circuit having independent RGB and each having a plurality of γ characteristics, and the RGB independent γ conversion circuit A γ switching circuit for switching the output of γ, a γ data setting of the RGB independent γ conversion circuit, and a viewing angle adaptive control circuit for controlling the switching pattern of the γ switching circuit (2),, LCD panel (4)And the viewing angle adaptive control circuit (3) sets a γ characteristic to be the same as R and B, and G is set to a γ characteristic different from RB in a trio comprising one pixel of RGB, and the trio By controlling so that the γ switching pattern is set as a unit and all adjacent pixels have different γ characteristics, the viewing angle characteristics are improved without deterioration in image quality. is there.
[0015]
In addition, depending on the characteristics of the video signal, the modulation pattern for each RGB pixel unit or the modulation pattern for each RGB trio unit is properly used to optimize the input signal.
[0016]
In addition, the second problem can be suppressed by using image feature information obtained from the image feature detection circuit, image feature information such as high-frequency components and flatness, and gradation and color signals of the input signal. The degree of modulation of γ is controlled so as to be effectively controlled.
[0017]
Furthermore, for the third problem, the video signal is compensated and controlled by adaptively controlling each parameter such as the color signal and the γ characteristic of the input video signal in accordance with the γ modulation characteristic to be controlled. It is a thing.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
    (Embodiment 1)
  FIG. 1 shows the present invention.The fruit1 is a block diagram showing a configuration of a liquid crystal display device that performs a driving method according to Embodiment 1. In the present liquid crystal display device shown in FIG. 1, reference numeral 1 denotes a predetermined application necessary for input video signal data based on VT characteristics of a liquid crystal panel. RGB independent γ conversion circuit that can set RGB individually for multiple γ characteristics that convert to voltage, 2 is a RGB independent switching control with a predetermined pixel pattern to achieve the desired viewing angle characteristics The γ switching circuit 3 performs an optimum pattern in consideration of the pixel arrangement of the liquid crystal panel to be used according to the inputted liquid crystal panel pixel arrangement information, and γ data setting and γ switching for the RGB independent γ conversion circuit 1 A viewing angle adaptive control circuit configured to perform switching control with respect to the circuit 2 and perform modulation control of γ, 4 is a TN liquid crystal, and the viewing angle dependency is increased with respect to a desired direction. A liquid crystal panel that has been cormorant orientation control.
[0020]
The operation of the liquid crystal display device configured as described above will be described with reference to FIGS. 1, 6, 7, and 15.
[0021]
First, the RGB independent γ conversion circuit 1 includes three RGB circuits that perform γ conversion processing by a calculation method using a plurality of parameters, and each parameter can be set to γ1 and γ2 for each RGB. For γ conversion processing, the ROM table method may be used, or by partially combining with the ROM table method, the γ characteristics can be partially curved, and the accuracy is further improved compared to the case of only linear approximation by calculation using parameters. A γ conversion circuit may be used. Here, the ideal γ characteristics are the characteristics of the color filter, backlight, etc. of the liquid crystal display device. In order to control the viewing angle while suppressing the occurrence of the above, etc., the γ characteristics of RGB need to be set to the optimum values individually and further according to the gradation. Therefore, it is set as the structure which can be controlled separately in this way.
[0022]
The signal output from the RGB independent γ conversion circuit 1 is input to the source driver of the liquid crystal panel 4 as a video signal that is individually controlled by the γ switching circuit 2 and is subjected to γ modulation control, and the liquid crystal pixels are driven. The viewing angle adaptive control circuit 3 operates to control each parameter of the γ switching circuit 2 and γ1 and γ2 so as to perform space-time modulation on the γ1 characteristic and the γ2 characteristic, as shown in the conventional example. However, the modulation (switching) pattern in the two-dimensional direction (screen within one frame) of the γ modulation is subjected to an optimum process as described below according to the pixel arrangement information of the liquid crystal panel 4.
[0023]
In the conventional example, as shown in FIG. 15, the RGB trio is one unit, and one set of RGB is a modulation pattern that sets the same characteristics of γ1 or γ2. In the first embodiment, b in FIG. As shown, a modulation pattern is set with each pixel of RGB as one unit. In particular, the combination of the modulation patterns is determined in consideration of the pixel arrangement of the liquid crystal panel. For example, assuming that the pixel arrangement of the liquid crystal panel is a stripe type as shown in a in FIG. 7 and is arranged in the order of RGB, RGB, and RGB from the left, assuming that the gamma modulation is a checkered pattern, as shown in b in FIG. In addition, when R and B are γ1, only G is always controlled in reverse phase so that G has a γ2 characteristic. In this way, by making the center of the pixel array constituting one stripe-type pixel out of phase, γ1 and γ2 can be a checkered pattern in the minimum pixel unit.
[0024]
Further, since the luminance signal = 0.59G + 0.3R + 0.11B, by setting only G as the reverse phase, the luminance having a high influence on the luminance signal is set as the reverse phase with respect to R and B. It is advantageous because the influence on the signal can be distributed almost evenly (with the smallest luminance difference).
[0025]
  Therefore, the pixel array is in the order of RGB, RGB, RGB, as described above.High influence on luminance signal G In the center of the pixel arrayIt is considered that the arrangement is most effective. Therefore, what is necessary is just to use what was arranged in this way about the color filter of the liquid crystal panel 4. FIG. In the case of a liquid crystal panel in which the color filter is not in this arrangement, as shown in FIG. 6, a delay control circuit 9 for each of the RGB signals is provided at the output portion of the γ switching circuit 2, and the input liquid crystal panel pixel arrangement information By performing RGB delay control so that the viewing angle adaptive control circuit 3 is in the same order as the pixel arrangement order, it is possible to perform independent γ modulation control for each RGB pixel by this optimal combination.(That is, the viewing angle adaptive control circuit 3 controls the signal input timing to the liquid crystal panel 4 with respect to each of R, G, and B by the delay control circuit 9 based on the input liquid crystal panel pixel arrangement information. , G Can be output (displayed) in a manner similar to that arranged in the center of the pixel array, and in this case as well, each RGB pixel can perform independent γ modulation control. )
[0026]
In this way, by using a modulation pattern in units of RGB pixels, which is the minimum unit that can be performed by signal processing, the modulation pattern can be reduced, and the pattern pattern (dot pattern in the case of a checkered pattern) can be made finer. Therefore, it is possible to apply the viewing angle expansion technique by γ modulation even in a low-resolution liquid crystal panel as compared with the case where the RGB trio is modulated as one unit.
[0027]
In the first embodiment and the following embodiments, only two types of switching, γ1 and γ2, are described as γ characteristics, but it is possible to switch three or more γ characteristics as well, for example, When modulation is performed by assigning three γ characteristics to each RGB pixel, it is possible to achieve a neutral state against the trade-off between the effect of widening the viewing angle and the adverse effect that the pattern becomes conspicuous. It is.
[0028]
As described above, the modulation (switching) pattern of the γ characteristic in the viewing angle expansion control is adaptively selected according to the pixel arrangement of the liquid crystal panel, and is controlled with the minimum pattern for each RGB pixel. Thus, the pattern pattern by the control is not conspicuous, and the viewing angle enlargement control can be realized with a good image quality of the edge portion such as a sense of resolution and diagonal lines. In addition, it is possible to apply a viewing angle expansion technique by γ modulation even in a liquid crystal panel having a lower resolution than the conventional example.
[0029]
    (Embodiment 2)
  FIG. 2 shows the present invention.The fruitFIG. 2 is a block diagram illustrating a configuration of a liquid crystal display device that performs a driving method according to a second embodiment. In the present liquid crystal display device illustrated in FIG. 2, reference numeral 1 denotes an RGB independent γ-conversion circuit similar to that in the first embodiment, and 1 is a γ switching circuit similar to 1, and 31 is a liquid crystal panel pixel array information, an input source type, and information indicating its display area, taking into account the pixel array of the liquid crystal panel according to the input video signal type A viewing angle adaptive control circuit configured to perform γ modulation control by performing γ data setting for the RGB independent γ conversion circuit 1 and switching control for the γ switching circuit 2 with an optimal pattern. This is the same liquid crystal panel as the first embodiment.
[0030]
The operation of the liquid crystal display device configured as described above will be described with reference to FIG.
[0031]
In general, the video characteristics of the video signal displayed on the liquid crystal panel 4 largely depend on the type of the signal source. For example, in the case of an input signal such as a personal computer screen or a car navigation screen, many characters and lines are displayed, the dynamic range of the input signal is large, and the signal component is biased to a relatively high or low luminance. There are many signals with high contrast. It can also be said that there is relatively little fast movement of the image. On the other hand, a natural image video signal such as a TV or video signal, on the other hand, is concentrated in halftones, depending on the video scene, concentrated in high luminance, or concentrated in low luminance. It can be said that the speed at which the image moves varies.
[0032]
Therefore, considering the above points, whether the modulation pattern is set for each RGB pixel unit as shown in the first embodiment in accordance with the type of the input video signal source as described above, Thus, by selecting whether to set the modulation pattern with the RGB trio as one unit, it is possible to use the effective modulation pattern in a simple manner.
[0033]
Specifically, in the case of a personal computer or car navigation signal input, there are many fine characters and lines. Therefore, if the modulation pattern of the first embodiment is applied, the influence of the false color described in detail in the third embodiment is exerted. Easy to receive. In addition, since there are many signals having a large dynamic range and high contrast, the influence on the image quality such as gradation inversion due to the viewing angle is relatively small. For this reason, it is considered that a conventional pattern in which modulation is performed with the RGB trio as one unit is suitable.
[0034]
On the other hand, in the case of TV signals and video signals, false colors are relatively inconspicuous due to their fast movement and many natural images, or a sense of resolution and smoothness are given priority over the occurrence of false colors. In this case, it can be said that the method of setting the modulation pattern for each RGB pixel unit described in the first embodiment is suitable.
[0035]
In the second embodiment, the above-described determination is performed based on the input source type signal input to the viewing angle adaptive control circuit 31. In the case of a personal computer or car navigation signal input, the RGB trio is set to 1 as usual. In the case of a TV or video signal, modulation is performed as a unit, and a γ modulation pattern is appropriately selected so that the processing described in the first embodiment is performed based on liquid crystal panel pixel arrangement information, and an RGB independent γ conversion circuit The γ modulation pattern is controlled for the 1 and γ switching circuit 2.
[0036]
In addition, in a system that displays a plurality of screens, if an input source type signal and information indicating its display range are given to the viewing angle adaptive control circuit 31, and each display screen can be controlled independently, In an example in which a TV display and a car navigation display are simultaneously displayed in an in-vehicle TV or the like with a two-screen display function, it is possible to display with a modulation pattern suitable for each image characteristic.
[0037]
Further, in the case where the video feature detection circuit 6 is provided as in the fourth embodiment and the video signal to be displayed is an image in which a sense of resolution and smoothness should be more important than generation of false colors, each of the RGB in the first embodiment is used. The modulation pattern is implemented in units of pixels, and conversely, in the case of an image in which the occurrence of false colors is a problem, the use of the modulation pattern with the RGB trio as one unit as shown in the conventional example is performed properly. It is conceivable to do as well.
[0038]
As described above, by effectively selecting the modulation pattern according to the type of the input signal source, effective viewing angle expansion control adapted to the video characteristics can be realized very easily.
[0039]
    (Embodiment 3)
  FIG. 3 shows the present invention.The fruitFIG. 3 shows a groove block diagram of a liquid crystal display device that performs the driving method in the third embodiment. In the present liquid crystal display device in FIG. 3, reference numeral 1 denotes an RGB independent γ-conversion circuit similar to that in the first embodiment; The gamma switching circuit is the same as in the first embodiment, 5 is a false color detection circuit for detecting an image portion where false colors are likely to be generated from the input video signal and the degree thereof, and 32 is the false color detection information and the liquid crystal panel. The γ data setting for the RGB independent γ conversion circuit 1 and the γ switching circuit 2 so as to reduce the false color in the false color generation unit with an optimum pattern considering the pixel arrangement of the liquid crystal panel 4 based on the pixel arrangement information. Is a viewing angle adaptive control circuit configured to perform switching control for γ and perform modulation control of γ, and 4 is a liquid crystal panel similar to that of the first embodiment.
[0040]
The operation of the liquid crystal display device configured as described above will be described with reference to FIGS.
[0041]
First, as described in the first embodiment, in the case of the γ modulation method in which the modulation pattern is set in units of RGB pixels, the white balance is broken for each pixel in which a set of RGB trio is set. There is a problem that it occurs.
[0042]
However, the false color includes a portion that is particularly conspicuous and a portion that is relatively inconspicuous depending on the state of the image, or a portion in which the resolution feeling is prioritized depending on the image. In general, the most prominent part of false color is considered to be halftone fine characters, etc. Problems such as gradation reversal and black floating whites that are problematic as viewing angle characteristics for such parts are considered. It is considered that there is relatively little influence.
[0043]
In the third embodiment, in consideration of the above, in the case of the γ modulation method in which the modulation pattern is set in units of RGB pixels as in the first embodiment, a false color is particularly generated depending on the state of the video signal. As shown in FIG. 8b, for the portion where the generation is desired to be suppressed, the effect of improving the viewing angle is reduced by suppressing the modulation degree to be small, but the effect of generating the false color is suppressed. It is.
[0044]
Therefore, the false color detection circuit 5 has only to detect the signal portion determined as the above portion from the input video signal. Specifically, the edge portion of the image (the portion where the change amount of the input signal is large) or the impulse is detected. A portion where the signal changes like a signal is detected, and the degree (change amount) is also output to the viewing angle adaptive control circuit 32. The viewing angle adaptive control circuit 32 performs γ modulation control for setting a modulation pattern for each RGB pixel unit described in the first embodiment. In addition, the viewing angle adaptive control circuit 32 indicates that the image portion is likely to generate false colors. Control is performed so as to perform modulation degree control as shown in FIG. 8 based on the signal and the signal indicating the degree thereof, and γ data setting for the RGB independent γ conversion circuit 1 is controlled independently for RGB.
[0045]
When the RGB independent γ conversion circuit 1 is a ROM table system, an operation for switching to a predetermined data table may be performed.
[0046]
Further, in the above description, the control of the switching pattern of the γ switching circuit 2 is the same as the pattern control that modulates in units of RGB pixels in the first embodiment, and only the false color generation unit is γ in the viewing angle adaptive control circuit 32. Although the case where the control is performed so as to reduce the generation of false color by suppressing the modulation degree of RGB, as described in Embodiment 2 in the false color generation portion, the RGB trio is set as one unit as in the conventional example. It is also possible to eliminate the generation of false colors by controlling the switching pattern of the γ switching circuit 2 so as to modulate with the modulation pattern. Regarding the proper use of these two control methods, for example, the portion where the false color generation level detected by the false color detection circuit 5 is large, such as the character portion described above, is completely deleted by the latter method, and the natural image is not much. For a portion where the false color generation degree is not so large, such as an edge portion that is not strong, it is possible to use the portion by suppressing the modulation degree by the former method.
[0047]
Note that, as in the fifth embodiment, the signal processing circuit 8 is provided, and for an image in which the occurrence of false color becomes a problem, the degree of edge enhancement is suppressed or the noise reduction processing is set to be strong. Such adaptive control also provides the effect of signal processing, and it is effective to include such a signal processing circuit 8.
[0048]
  As described above, the third embodiment applies the modulation pattern in units of RGB pixels described in the first embodiment, and is such as a fine character or building image in which false colors are conspicuous. In this part, the modulation degree is adaptively reduced to reduce the difference between the conversion data of γ1 and γ2, or the RGB trio is partially made into one unit modulation pattern, and the false color is suppressed to be small. It is possible to realize the viewing angle enlargement control with high image quality.
(Embodiment 4)
  FIG. 4 shows the present invention.The fruitFIG. 4 shows a block diagram of a configuration of a liquid crystal display device that performs a driving method according to a fourth embodiment. In the liquid crystal display device shown in FIG. 1 is a γ switching circuit similar to 1, 6 is a video feature detection circuit for detecting image flatness, harmonic component parts, edge parts, etc. from the input video signal, and 7 is a signal gradation and video of the input video signal. A γ modulation degree control determination circuit that determines the priority of the viewing angle expansion effect from the feature information. Reference numeral 33 denotes the RGB independent γ conversion circuit 1 according to the modulation degree control signal input from the γ modulation degree control determination circuit 7. A viewing angle adaptive control circuit configured to perform modulation control of γ by controlling the modulation degree control of γ data and the switching pattern of the γ switching circuit 2, and 4 is a liquid crystal similar to that of the first embodiment. It is a panel.
[0049]
The operation of the liquid crystal display device configured as described above will be described with reference to FIGS. 4, 8, 9, 10, and 11.
[0050]
As described above, gradation inversion is achieved by equivalently synthesizing and improving the VT characteristic in each viewing angle direction in the liquid crystal pixel by modulating the γ characteristic in the spatio-temporal direction as in the present invention. In the technique for improving the viewing angle characteristics such as the white floating blackout gradation characteristics, the degree of modulation of the γ characteristics (in the present invention, the degree of difference in each gradation of the γ characteristics γ1 and γ2 to be switched) is to some extent. The larger the angle, the higher the viewing angle improvement effect. However, on the other hand, the dot pattern (modulation pattern pattern) by γ modulation is conspicuous, and at the same time, depending on the modulation pattern, a false color as described in the first to third embodiments is generated, or the RGB trio is one unit. Even if it is a pattern that does not generate false colors as in the conventional case, the edge part becomes uneven and loses smoothness, the fine characters are faded, the fine line becomes dotted, the flat part is also a color like human skin, for example This part has various image quality problems such as unevenness and roughness.
[0051]
On the other hand, as shown in the conventional example, the spatial modulation by reversing the modulation pattern in the field direction can alleviate various adverse effects due to the conspicuousness of these dot patterns. The viewing angle improvement effect itself is also suppressed. Furthermore, with regard to spatial modulation, there is a risk that a new problem called flicker is likely to occur. As described above, the degree of modulation of γ has a relationship that it is a trade-off between the effect of improving the viewing angle and the adverse effect on image quality due to this processing.
[0052]
The viewing angle improvement includes an image that is not so necessary (an image that is not easily affected by the viewing angle characteristic) and a very effective image depending on the image to be displayed.
[0053]
In this way, there are images that are likely to have a viewing angle improvement effect and images that are likely to cause dot effects depending on the state of the image. An example in which this is determined by the gradation of the input signal is shown in FIG.
[0054]
As described above, the video signal has a viewing angle characteristic depending on its signal state (image) and an image that is problematic (to be improved) as a viewing angle characteristic, that is, an image (image portion) with a high priority of the viewing angle expansion effect. On the other hand, it can be said that there is an image (image portion) that is not greatly affected (the necessity for improvement is not so high), that is, an image with a low priority of the viewing angle expansion effect.
[0055]
In view of these points, the fourth embodiment modulates the “image portion with a high priority of the viewing angle expansion effect” or the “image portion where the adverse effect is relatively difficult to occur” as shown in FIG. Adaptive control is performed to improve the viewing angle improvement effect by increasing the degree of control, and conversely for “image part with low priority of viewing angle expansion effect” or “image part where adverse effects are relatively likely to occur” In FIG. 8B, adaptive control is performed so as to suppress the image quality adverse effect by controlling the modulation degree to be lowered.
[0056]
Referring to FIG. 4, the γ modulation degree control determination circuit 7 makes the above determination based on the image features obtained by the video feature detection circuit 6 and the gradation of the input signal, and the viewing angle expansion effect priority parameter is set as the viewing angle. In response to this, the viewing angle adaptive control circuit 33 controls γ data setting for the RGB independent γ conversion circuit 1 as shown in FIGS. A conceptual diagram of this modulation degree emphasis suppression processing is shown in FIG. FIG. 11 shows an example of a specific γ characteristic when the modulation degree is controlled as described above. The γ characteristics shown in FIG. 11 indicate the input / output characteristics of the digital γ circuit showing the output data with respect to the input data, and the characteristic example of FIG. 11 is as described in the fifth embodiment. 4 shows an example of characteristics of a modulation γ circuit (RGB independent γ conversion circuit) in a system in which an image quality adjustment RGB independent γ circuit is separately provided for image quality adjustment.
[0057]
A specific example of processing will be described below by dividing it into modulation degree emphasis processing and modulation degree suppression processing.
[0058]
First, in the case of performing modulation degree emphasis processing, an example of “an image portion with a high priority of the viewing angle expansion effect” will be described here. First, tone reversal, which is the biggest problem as image degradation due to viewing angle, can be mentioned. In general, inversion in a low luminance range from the lower viewing angle direction and inversion in a high luminance portion from the upper viewing angle direction are problems. An example showing this is a in FIG. In addition, these are regarded as problems because they are more conspicuous in a flat portion as an image.
[0059]
This example will be described with reference to FIG. 4. When the gradation of each of the RGB input signals corresponds to the predetermined low gradation area or high gradation area as described above, or in FIG. In the case where it corresponds to a key portion and, in addition to this, when the flatness is detected in a predetermined period by the video feature detection circuit 6, the “viewing angle expansion” is performed in the γ modulation degree control determination circuit 7. It is determined that it corresponds to an “image portion having a high effect priority”, and the viewing angle expansion effect priority parameter (horizontal axis) in FIG. 10 is set higher than the standard. Here, what is important is that the viewing angle expansion effect priority parameter corresponding to the horizontal axis of FIG. 10 is continuously set through a low-pass filter, and the modulation degree is naturally changed while suppressing a sudden change. It is to let you. As a result, even if there is a malfunction in the adaptive control determination in the γ modulation degree control determination circuit 7, adverse effects such as a drastic change in the modulation degree associated with the adaptive control can be reduced, and control without a sense of incompatibility can be achieved.
[0060]
In this example of enhancement processing, an example has been described for “an image portion with a high priority of viewing angle expansion effect”, but other determinations based on similar parameters of the input video signal and video feature information are also possible. It is also conceivable to set a viewing angle expansion effect priority parameter based on a reference. In addition, the gamma modulation degree control determination circuit 7 can set the viewing angle expansion effect priority parameter by paying attention to the aspect of “an image portion in which an adverse effect is relatively unlikely”. However, paying attention only to the aspect of “image part that is less likely to cause adverse effects”, for example, an effect such as a halftone flat part with a light shade may be required, but adverse effects may occur easily. Therefore, it is necessary to set the viewing angle widening effect priority parameter by appropriately comprehensively judging. In the above enhancement processing example, an example is shown in which adaptive control is performed with emphasis on gradation inversion as the viewing angle characteristic to be improved. It is necessary to set the viewing angle expansion effect priority parameter according to the determined criteria.
[0061]
Next, in the case of performing the modulation degree suppression process, an example of “an image portion where an adverse effect is relatively likely to occur” will be described here. The main adverse effect is that the dot pattern by γ modulation becomes uneven at the edge portion of the image, as described above, and appears to be a rough edge (a jagged edge). This has a great influence especially on the oblique edge portion. For the same reason, fine characters are blurred and a fine line of 1 pixel appears as a dotted line. As described above, it is considered that an edge portion of an image, a halftone impulse signal, and the like are likely to cause harmful effects. In addition, the high-frequency component portion of the image, that is, the image portion of the fine pattern, has a large influence on the image if the dot pattern overlaps the image. FIG. 9B shows an example of such an “image portion where an adverse effect is relatively likely to occur”. Therefore, in the case of suppression processing, determination is made with emphasis on video information detected by the video feature detection circuit 6.
[0062]
In general, in a flat portion having a dark color that is not halftone, it can be said that “an image portion having a relatively small viewing angle expansion effect”. In such an image portion, it is considered that the modulation degree should be controlled to be low in order to suppress harmful effects.
[0063]
This example will be described with reference to FIG. 4. When the gradation of each of the RGB input signals corresponds to a gradation area that is not the gradation used for the determination in the enhancement process, or in FIG. In the case where it corresponds to a key part, and in addition to this, when the image feature detection circuit 6 detects an edge portion of an image or a high frequency component portion of a signal in a predetermined period, etc., a γ modulation degree control determination circuit 7, it is determined that it corresponds to the “image portion where the adverse effect is relatively likely to occur”, and the viewing angle expansion effect priority parameter (horizontal axis) in FIG. 10 is set lower than the standard. Also in this case, the viewing angle expansion effect priority parameter is continuously set through the low-pass filter, and the modulation degree is naturally changed while suppressing a rapid change.
[0064]
In this example of suppression processing, an example has been described for “an image portion where adverse effects are relatively likely to occur”. However, in addition to this, a field of view based on other determination criteria based on similar parameters of the input signal and video feature information is also used. It is also conceivable to set a corner expansion effect priority parameter. Further, the gamma modulation degree control determination circuit 7 can set the viewing angle expansion effect priority parameter by paying attention to the aspect of “an image portion with a low viewing angle expansion effect (low viewing angle expansion effect)”. . However, as in the case of the enhancement process, the aspect of “an image part where adverse effects are relatively likely to occur” and the aspect of “an image part having a low priority of viewing angle expansion effect (small viewing angle expansion effect)” are not necessarily included. Since there is a case where they do not match, it is necessary to make a comprehensive judgment as appropriate to set the viewing angle expansion effect priority parameter. Also, in this suppression processing example, we showed adverse suppression that presupposes that adaptive control is performed with emphasis on tone reversal as the viewing angle characteristics that we would like to improve, but we focused on other viewing angle characteristics improvement items If this is the case, it is necessary to set the viewing angle expansion effect priority parameter according to the determination criteria corresponding to the determination criterion.
[0065]
Note that the fourth embodiment is not limited to the case of the modulation pattern in which each RGB pixel is one unit as described in the first and third embodiments. Needless to say, the RGB trio as in the conventional example is 1 Even in the case of a modulation pattern as a unit, it can be similarly implemented.
[0066]
As described above, according to the fourth embodiment, according to the purpose of the viewing angle improvement, the degree of modulation is increased only in a portion where the image is particularly desired to be improved or an effective portion to increase the viewing angle improvement effect. For image parts that are relatively irrelevant to the target viewing angle improvement and have a greater negative effect, it is effective to reduce the modulation level and suppress the negative effect with natural adaptive control without any sense of incongruity. This makes it possible to control the viewing angle more accurately.
[0067]
    (Embodiment 5)
  FIG. 5 shows the present invention.The fruitFIG. 6 shows a block diagram of a configuration of a liquid crystal display device that performs a driving method according to a fifth embodiment. In the present liquid crystal display device, FIG. 1 is a γ switching circuit similar to 1, 8 is an RGB independent signal processing circuit that performs γ conversion processing for color gain and hue control or image quality adjustment on an input video signal, and 34 is a γ for the RGB independent γ conversion circuit 1. A viewing angle adaptive control circuit configured to perform γ modulation control by performing data setting and simultaneously outputting γ setting information to the RGB independent signal processing circuit 8 and performing switching pattern control on the γ switching circuit 2. Reference numeral 4 denotes a liquid crystal panel similar to that of the first embodiment.
[0068]
The operation of the liquid crystal display device configured as described above will be described with reference to FIGS.
[0069]
As described so far, the method of improving the viewing angle characteristic by space-time modulating the γ characteristic by signal processing in this way has various adverse effects and has a trade-off with the viewing angle improvement effect. Many.
[0070]
Originally, to improve the viewing angle characteristics (enlarge the viewing angle) is to improve the visual characteristics from angles other than the front viewing angle direction. Therefore, it is desired that the visual characteristics from the front viewing angle direction that is originally good do not change with or without the viewing angle improvement processing. However, the present technology modulates the γ characteristic in the spatio-temporal direction, so that the VT characteristic in each viewing angle direction is equivalently synthesized in the liquid crystal pixel, and is combined with the integration effect of the human eye to be improved in total. As can be understood from the principle, the equivalent γ characteristic (equivalent γ characteristic corresponding to a combination of γ1 and γ2) shown in a in FIG. 12 depends on the modulation characteristic of γ (characteristics of a plurality of γ to be switched). ) May change the visual characteristics from the front direction from the original characteristics. In such a case, the color appears to be light, or the hue appears to be slightly changed, especially in a slightly light flat portion having a halftone luminance. That is, if γ1 and γ2 as shown in FIG. 12a are set, the equivalent equivalent γ of the synthesis is as shown by the dotted line, but this is essentially the same as shown by the solid line b in FIG. If the viewing angle enlargement process is turned off, the above-described adverse effects may occur from the front viewing angle direction.
[0071]
In the fifth embodiment, in such a case, the RGB independent signal processing circuit 8 corrects the gain of the color signal, corrects the hue, or compensates with the γ circuit for image quality adjustment so as to compensate for this. It is intended to operate.
[0072]
As is apparent from the embodiments so far, this adverse effect is also greater as the modulation degree is larger. Therefore, when performing modulation degree control as described in the fourth embodiment, the modulation degree is considered. Direction for correcting the gain of the color signal based on the correction amount for each gradation, that is, the amount of change from the original characteristic for each gradation (in this case, the correction direction is determined depending on which direction the original γ characteristic has changed) Video signal processing is performed so as to compensate. That is, the control is performed so that the gain of the color signal of the gradation portion corresponding to A in FIG. 12B is slightly increased and the gain of the color signal of the gradation portion corresponding to B is slightly increased. The difference from the original γ indicated by b in FIG. 12 can be calculated when setting the modulation characteristics γ1 and γ2, so that the RGB independent signal processing circuit 8 applies correction in consideration of the degree of modulation for each gradation. It is possible.
[0073]
For hue, this technology corresponds to the RGB color shift characteristic of viewing angle characteristics, and it is based on the fact that independent γ modulation control is performed on each RGB signal. When the degrees are different for RGB, a hue change may occur for the same reason. In this case as well, each RGB can be compensated for from a difference from the original γ characteristic, and a change in hue can be suppressed.
[0074]
The important point here is that the compensation shown in the fifth embodiment is excessively excessive, and the purpose and effect of improving the viewing angle by the original γ modulation will be lost. It is necessary.
[0075]
Although FIG. 5 shows a case where an RGB signal is input as an input video signal, it is also conceivable that a Y color difference signal is input and such processing is performed in the color signal processing unit.
[0076]
  Next, as another solution to the same problem, the RGB independent signal processing circuit 8 is provided with an image quality adjustment RGB independent γ conversion circuit separately from the RGB independent γ conversion circuit 1 (for γ modulation). For adjustmentγ specialA process for obtaining the same effect by adjusting the property is also conceivable. In this case, since b in FIG. 12 is the γ characteristic itself, the image quality adjusting γ circuit may be controlled as shown in FIG. 13 to correct this. The image quality adjustment γ also needs to be configured so that the γ characteristic can be set differently for RGB,γ specialWhen the characteristics are different in RGB, it is possible to compensate by performing optimum processing for each RGB. In this case as well, if the compensation is performed excessively, the purpose and effect of improving the viewing angle by the original γ modulation are lost, so it is necessary to consider performing the compensation within an appropriate range.
[0077]
Further, having the γ circuit for image quality adjustment separately from the γ circuit for γ modulation as in this example is not only for the problem described in the fifth embodiment, but also by such signal processing. It is also effective as a configuration that easily realizes a system that improves the viewing angle characteristic by space-time modulating the γ characteristic. That is, the control for adjusting the image quality of the total system (creating an image) with the image quality adjusting γ circuit while the γ circuit for γ modulation is turned off (modulation is not performed when γ = 1 is set). In the configuration, when viewing angle improvement control is performed, the modulation γ circuit (RGB independent γ conversion circuit) makes the composite γ during modulation as γ = 1.0 as much as possible so as not to change the original γ characteristics. The basic control method is to control in this way. With such a configuration, it is not necessary to consider the image quality when setting the modulation data of γ when the viewing angle is improved, and it is easy to set, and the compensation of the present embodiment is also compensated as shown in FIG. Easy to calculate quantity.
[0078]
As described above, in the fifth embodiment, it is possible to perform a good display without greatly changing the image quality from the front viewing angle direction from the original image quality, and to improve the viewing angle without feeling uncomfortable. It becomes possible.
[0079]
【The invention's effect】
As is apparent from the above description, according to the present invention, in the technology for improving the viewing angle characteristics by such signal processing and drive control, the dot pattern by the modulation pattern can be made inconspicuous by minimizing the dot pattern. It is possible to improve the resolution by smoothing the edges and reducing the blurring of characters and lines, and to effectively suppress the adverse effects such as false colors that accompany this, resulting in a good-looking image quality Is possible. As a result, such a technique can be applied even to a liquid crystal panel having a lower resolution. In addition, by optimizing the modulation pattern by optimizing the characteristics of the video signal to be displayed, it can be used effectively regardless of whether the input is a video or TV signal, or a computer image or car navigation image signal. .
[0080]
Also, with regard to the viewing angle improvement effect and its adverse effects, by changing the modulation factor adaptively and naturally according to the characteristics and state of the display image, there are few adverse effects due to the adaptive processing, such as image quality degradation due to the viewing angle expansion processing. It is possible to realize effective viewing angle expansion control with reduced image quality.
[0081]
Furthermore, control of viewing angle expansion is performed with good image quality with little discomfort due to the presence or absence of processing, while suppressing changes in image quality such as color depth, hue, and tone characteristics from the front viewing angle direction, which occur due to the modulation state of the γ characteristic. be able to.
[Brief description of the drawings]
1 is a configuration block diagram of a liquid crystal display device that performs a driving method according to Embodiment 1 of the present invention;
FIG. 2 is a configuration block diagram of a liquid crystal display device that performs a driving method according to Embodiment 2 of the present invention.
FIG. 3 is a configuration block diagram of a liquid crystal display device that performs a driving method according to Embodiment 3 of the present invention.
4 is a block diagram showing the configuration of a liquid crystal display device that performs a driving method according to Embodiment 4 of the present invention. FIG.
FIG. 5 is a configuration block diagram of a liquid crystal display device that performs a driving method according to a fifth embodiment of the present invention.
6 is a configuration block diagram of a liquid crystal display device that performs the driving method according to Embodiment 1 of the present invention. FIG.
7 is a schematic diagram showing an example of a γ switching pattern in one screen in the γ conversion circuit of the driving method according to the first to third embodiments of the present invention. FIG.
FIG. 8 is a characteristic diagram showing an example of γ modulation degree control in the γ conversion circuit of the driving method according to the third and fourth embodiments of the present invention.
FIG. 9 is a characteristic diagram showing an example of the effect and negative gradation characteristics of the driving method according to the fourth embodiment of the present invention.
FIG. 10 is a conceptual diagram of modulation degree emphasis suppression processing of a driving method according to Embodiment 4 of the present invention.
FIG. 11 is a characteristic diagram illustrating an example of γ characteristic control by modulation degree control of a driving method according to Embodiment 4 of the present invention.
FIG. 12 is a characteristic diagram showing an example of a change in γ characteristics due to modulation of γ in the driving method according to the fifth embodiment of the present invention.
FIG. 13 is a characteristic diagram illustrating an example of compensation in image quality adjustment γ in the driving method according to the fifth embodiment of the present invention.
FIG. 14 is a block diagram illustrating a configuration of a conventional liquid crystal display device.
FIG. 15 is a schematic diagram showing a switching pattern shown in the configuration of a liquid crystal display device of a conventional example.
FIG. 16 is a characteristic diagram showing a γ modulation characteristic of a liquid crystal display device of a conventional example.
[Explanation of symbols]
1 RGB independent γ conversion circuit
2 γ switching circuit
3, 31, 32, 33, 34 Viewing angle adaptive control circuit
4 LCD panel
5 False color detection circuit
6 Video feature detection circuit
7 Gamma modulation degree control judgment circuit
8 RGB independent signal processing circuit
9 Delay control circuit

Claims (14)

An RGB independent γ conversion circuit (1) having independent RGB and each having a plurality of γ characteristics, and a γ switching circuit for switching the output of the RGB independent γ conversion circuit (1). (2), a viewing angle adaptive control circuit (3) for controlling γ data setting of the RGB independent γ conversion circuit (1) and a switching pattern of the γ switching circuit (2), and a liquid crystal panel (4) , The viewing angle adaptive control circuit (3)
In a trio consisting of one pixel each of RGB, the γ characteristics are set to the same R and B, G is set to a γ characteristic different from RB, and
Controlling to set the γ switching pattern with the trio as one unit, and
Control all adjacent pixels to have different γ characteristics,
A driving device for a liquid crystal display device characterized in that viewing angle characteristics are improved without deterioration of image quality.   When the pixel arrangement of the color filter of the liquid crystal panel (4) does not form one pixel in the order of RGB, an RGB individual delay adjustment circuit (9) is provided at the output of the γ switching circuit (2), and RGB 2. A driving device for a liquid crystal display device according to claim 1, wherein the delay is controlled so as to form one pixel in the order of.   The viewing angle adaptive control circuit (3) sets the γ switching pattern in common with the trio as one unit or sets each RGB pixel as one unit in consideration of the pixel arrangement of the liquid crystal panel. 2. The driving device for a liquid crystal display device according to claim 1, wherein whether to perform the selection is adaptively selected for each pixel in accordance with a type of an input video signal.   The viewing angle adaptive control circuit (31) sets the trio as one unit in the case of a signal including a lot of characters and figures according to the source type of the input video signal, 4. The driving device for a liquid crystal display device according to claim 3, wherein each of the RGB pixels is set independently as one unit in consideration of the pixel arrangement of the liquid crystal panel.   Furthermore, a false color detection circuit (5) for detecting a video portion in which false color is likely to be generated from the signal change amount of the input video signal is provided, and the viewing angle adaptive control circuit (3) detects the signal change amount of the input video signal. 2. The liquid crystal display device according to claim 1, wherein in a large portion, the γ data setting of the RGB independent γ conversion circuit (1) is set for each pixel and adaptive control is performed so as to suppress generation of false colors. Drive device.   The viewing angle adaptive control circuit (32) sets the necessary γ data and its switching pattern for each pixel based on the detection information of the false color detection circuit (5), and the RGB independent γ conversion circuit (1). 6. The driving device for a liquid crystal display device according to claim 5, wherein the driving device is set for the [gamma] switching circuit (2).   The viewing angle adaptive control circuit (32) makes a judgment for each pixel based on the detection information of the false color detection circuit (5), and in the portion where the signal change amount of the input video signal is large, the γ switching pattern is 6. The driving device for a liquid crystal display device according to claim 5, wherein the trio is commonly set as one unit, and adaptive control is performed so as to suppress generation of false colors.   Further, a video feature detection circuit (6) for extracting features of the input video signal, and a determination for enhancing or suppressing the modulation degree of γ from the input video signal and the video feature information extracted by the video feature detection circuit (6). A gamma modulation degree control determination circuit (7) that performs the viewing angle adaptive control circuit (3) for the RGB independent gamma conversion circuit ( The RGB independent γ conversion circuit (1) is applied to an image portion in which it is determined that a dot pattern is likely to occur in the input video signal by performing adaptive control to enhance the effect by increasing the modulation degree of the γ data setting in 1). 2. The drive device for a liquid crystal display device according to claim 1, wherein adaptive control is performed so as to suppress the occurrence of dot patterns by lowering the modulation degree of the γ data setting.   9. The driving device of a liquid crystal display device according to claim 8, wherein the video feature detection circuit (6) detects a flat portion of an image of an input video signal. The γ modulation degree control determination circuit (7) is a gradation that is susceptible to gradation inversion, which is a disturbance in the gradation characteristic of the transmittance that occurs at a viewing angle other than the front direction of the liquid crystal panel from the input video signal. Alternatively, it is calculated based on being a color and a flat portion of an image input from the video feature detection circuit (6), and it is determined that the image portion has a large viewing angle improvement effect. Item 9. A driving device for a liquid crystal display device according to Item 8.   9. The driving device for a liquid crystal display device according to claim 8, wherein the video feature detection circuit (6) detects a contour portion and a high frequency component portion of an image of an input video signal.   The γ modulation degree control determination circuit (7) has a gradation or color that is likely to generate a dot pattern from the input video signal, and the contour portion of the image input from the video feature detection circuit (6) or 9. The driving device for a liquid crystal display device according to claim 8, wherein the driving is performed based on the high-frequency component portion, and it is determined that the image portion is to suppress the occurrence of a dot pattern. Further, an RGB independent signal processing circuit (8) for performing RGB signal processing on the input video signal is provided, and according to the γ modulation degree of the γ data setting set by the viewing angle adaptive control circuit (34), RGB independent signal processing apparatus for driving a liquid crystal display device according to claim 1, wherein the controlling the gain and color phase of a color signal of the circuit (8).   The RGB independent signal processing circuit (8) is configured according to a difference in each gradation between a γ characteristic obtained by calculation from a plurality of γ data set by the viewing angle adaptive control circuit (34) and a desired γ characteristic. 14. The driving device for a liquid crystal display device according to claim 13, wherein the hue and gain of the color signal are controlled.

Images