JP2015011322A - Image processing apparatus and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus configured to prevent reduction in definition in a still image, to prevent fading of black color in a video image, and to improve a view angle, and an image processing method.SOLUTION: An image processing apparatus includes: a conversion processing unit which allocates a pixel of an image formed of a plurality of pixels to any of a high-grayscale pixel or a low-grayscale pixel, converts a grayscale value of the pixel allocated to the high- grayscale pixel to a higher grayscale value, and converts a grayscale value of the pixel allocated to the low-grayscale pixel to a lower grayscale value; and a determination unit which determines whether the pixel of the image is a video image or a still image. The conversion processing unit performs conversion so that a difference between the high-grayscale value and the low-grayscale value of the pixel to be converted when the determination unit determines that the pixel is a video image, is larger than a difference between the high-grayscale value and the low-grayscale value of the pixel to be converted when the determination unit determines that the pixel is a still image.

Description

  The present invention relates to an image processing apparatus and an image processing method for processing an image displayed on a liquid crystal panel.

  A liquid crystal display device changes the light distribution state of liquid crystal molecules by applying a voltage to a liquid crystal layer between electrodes constituting a pixel of a liquid crystal panel, thereby utilizing the optical anisotropy of the liquid crystal. The transmittance is adjusted, and the amount of light transmitted through the liquid crystal panel is controlled for each pixel to display an image with gradation. The light distribution state of the liquid crystal molecules changes not only in the applied voltage but also in the field of view depending on the change in the field of view, so the liquid crystal display device has a viewing angle dependency. High and narrow viewing angle.

  Such a liquid crystal display device is disclosed in Patent Documents 1 and 2, for example. The liquid crystal panel has different luminance characteristics depending on the viewing angle. In other words, the brightness differs between when the liquid crystal panel is viewed from the front and when viewed from the oblique direction. When the luminance is measured from the oblique direction, the intermediate gradation shifts to high brightness, and the screen appears whitish (both white and white). Therefore, a smooth color tone cannot be obtained.

  Therefore, when displaying an intermediate gradation that is easily affected by the viewing angle, a high gradation and a low gradation that are not easily affected by the viewing angle are used. For example, a high gradation pixel and a low gradation pixel are arranged in a grid pattern ( By disposing them in a staggered pattern and displaying pseudo gray levels, it is possible to suppress whitening when viewed from an oblique direction and widen the viewing angle.

JP 2004-62146 A JP 2009-276653 A

  However, in the conventional method, since the high gradation pixels and the low gradation pixels are arranged in a grid pattern, for example, the difference in the gradation values of adjacent pixels is large, and the fineness is impaired, and the edge portion There is a problem that the image becomes jagged and becomes a so-called rough image (video).

  The present invention has been made in view of such circumstances, and an image processing apparatus and an image processing capable of improving a viewing angle without impairing fineness in a still image and suppressing whitening in a moving image. It aims to provide a method.

  An image processing apparatus according to the present invention assigns a pixel of an image composed of a plurality of pixels to either a high gradation pixel or a low gradation pixel, and assigns a gradation value of the pixel assigned to the high gradation pixel to a higher gradation In the image processing apparatus including a conversion processing unit that converts a gradation value of a pixel assigned to the low gradation pixel to a lower gradation value of a lower gradation, the pixel of the image is a moving image Or a determination unit that determines whether the image is a still image, and the conversion processing unit includes the high gradation value to which the gradation value of the pixel is converted when the determination unit determines that the pixel is a moving image. The difference from the low gradation value is set larger than the difference between the high gradation value and the low gradation value to which the gradation value of the pixel is converted when the determination unit determines that the pixel is a still image. It is characterized by being converted.

  The image processing apparatus according to the present invention includes a difference calculation unit that calculates a difference between gradation values of corresponding pixels of one time-series image and another image, and the determination unit includes the gradation of the pixel. It is characterized in that it is determined whether the pixel is a moving image or a still image depending on whether the difference between the values is larger or smaller than a predetermined difference threshold value.

  The image processing apparatus according to the present invention includes a difference calculation unit that calculates a difference in gradation value between a pixel of the image and a peripheral pixel of the pixel, and the determination unit includes a gradation value of the pixel and the peripheral pixel. It is characterized in that it is determined whether the pixel is a moving image or a still image depending on whether the difference is greater or smaller than a predetermined difference threshold.

  The image processing apparatus according to the present invention includes an assigning unit that assigns a high gradation pixel and a low gradation pixel so as to form a lattice pattern for each of one or a plurality of pixels of the image.

  In the image processing apparatus according to the present invention, the determination unit determines a time point when the still image changes to a moving image or a time point when the moving image changes to a still image, and the high gradation value and the low gradation value An adjustment unit that adjusts the difference to gradually increase or decrease gradually from the time point is provided.

  In the image processing apparatus according to the present invention, when the determination unit determines that both a moving image and a still image exist in the pixel of the image, the high gradation value and the low gradation used when the determination unit determines that the image is a moving image. A selection unit that selects either a difference between the value and a difference between a high gradation value and a low gradation value used when the determination unit determines that the image is a still image, and the conversion processing unit includes: The gradation value of all the pixels of the image is converted using the difference between the selected high gradation value and low gradation value.

  An image processing method according to the present invention assigns a pixel of an image composed of a plurality of pixels to either a high gradation pixel or a low gradation pixel, and assigns a gradation value of the pixel assigned to the high gradation pixel to a higher gradation. In the image processing method of converting the gradation value of the pixel assigned to the low gradation pixel to the lower gradation value of the lower gradation, the pixel of the image is a moving image or a still image And a difference between the high gradation value and the low gradation value to which the gradation value of the pixel is converted when it is determined that the pixel is a moving image, and the pixel is a still image And converting the gradation value of the pixel to be larger than the difference between the high gradation value and the low gradation value, which is converted.

  According to the present invention, it is possible to improve the viewing angle without impairing the sense of fineness in a still image and suppressing whitening in a moving image.

1 is a block diagram illustrating an example of a configuration of a liquid crystal display device as an image processing device according to a first embodiment. It is explanatory drawing which shows an example of the determination method of the moving image and still image by a moving image detection part. It is explanatory drawing which shows the 1st example of the viewing angle improvement process by a viewing angle improvement process part. It is explanatory drawing which shows the 1st example of the calculation method of the high gradation image and low gradation image by a high gradation image and a low gradation image output part. It is a schematic diagram which shows an example of the pattern signal which a pattern signal generation part produces | generates. It is a schematic diagram which shows an example of an input image. It is a schematic diagram which shows an example of an output image in case an input image is a moving image. It is a schematic diagram which shows an example of an output image in case an input image is a still image. 6 is an explanatory diagram illustrating an example of luminance characteristics of the liquid crystal display device of Embodiment 1. FIG. It is explanatory drawing which shows the 2nd example of the viewing angle improvement process by a viewing angle improvement process part. It is explanatory drawing which shows the 2nd example of the calculation method of the high gradation image | video and the low gradation image | video by the high gradation image | video and the low gradation image | video output part. It is a schematic diagram which shows an example of the output image at the time of using the gradation difference parameter (alpha). It is explanatory drawing which shows an example of the luminance characteristic of a liquid crystal display device at the time of using the gradation difference parameter (alpha). FIG. 3 is a schematic diagram illustrating an example of an image state obtained by a viewing angle improvement process of the liquid crystal display device according to the first embodiment. It is a schematic diagram which shows the other example of the pattern signal which a pattern signal generation part produces | generates. 10 is a time chart illustrating a change state based on a time constant of a gradation difference parameter α by a viewing angle improvement processing unit according to the second embodiment. It is explanatory drawing which shows an example of the mode of the brightness | luminance change by the change between a still image and a moving image. FIG. 10 is a block diagram illustrating an example of a configuration of a liquid crystal display device as an image processing device according to a third embodiment. FIG. 10 is an explanatory diagram illustrating an example of an output mode of a gradation difference parameter α by a gradation difference parameter output unit according to a fourth embodiment.

(Embodiment 1)
Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof. FIG. 1 is a block diagram illustrating an example of a configuration of a liquid crystal display device 100 as an image processing apparatus according to the first embodiment. The liquid crystal display device 100 includes a video signal input unit 11, a frame memory 12, a viewing angle improvement processing unit 13, a liquid crystal driving unit 20, a liquid crystal panel 30, and the like.

  The liquid crystal driving unit 20 includes a gate driver, a source driver, and the like, and drives the liquid crystal panel 30 based on the video signal output from the viewing angle improvement processing unit 13. Thereby, the transmittance of the liquid crystal panel 30 can be adjusted by the gradation of the video signal to express the change in the density of the video.

  The video signal input unit 11 is an interface for acquiring a video signal. The video signal is a signal in which video signals for one frame are continuous in time series. The video signal is processed independently for each of R (red), G (green), and B (blue). The video signal input unit 11 stores the acquired video signal in the frame memory 12 for each video signal of one frame. A video signal for one frame is also referred to as an image for one frame.

  The viewing angle improvement processing unit 13 includes a moving image detection unit 131, a gradation difference parameter output unit 132, a high gradation video and low gradation video output unit 133, a high gradation video and low gradation video selection unit 134, and a pattern signal generation unit 135. Etc. The viewing angle improvement processing unit 13 has functions such as a determination unit, a conversion processing unit, a difference calculation unit, and an allocation unit.

  The moving image detection unit 131 determines whether any pixel of the current frame image is a moving image or a still image based on the input video of the current frame and the previous frame. The moving image detection unit 131 outputs a flag signal based on the determination result. In the present embodiment, the flag signal output by the moving image detection unit 131 is represented by flag (x, y). For example, when flag (x, y) = sg, a still image is shown, and when flag (x, y) = dg, a moving image is shown. Further, (x, y) is a pixel coordinate.

  FIG. 2 is an explanatory diagram showing an example of a moving image / still image determination method by the moving image detection unit 131. FIG. 2 shows an image for one frame, which is represented by 8 × 8 pixels for convenience. As shown in FIG. 2, an image (video) of a frame (t-1) that is the latest frame and an image (video) of a frame t that is the current frame, as one time-series image and another image. ) Each corresponding pixel (a pixel with a pattern in FIG. 2), that is, each pixel having the same coordinate (x, y) is represented by d (x, y, t−1), d (x, y, t).

  The moving image detection unit 131 calculates the difference between the tone values of the corresponding pixels of one time-series image and another image. The gradation value difference Δd can be calculated by the following equation: Δd = | d (x, y, t) −d (x, y, t−1) |

  FIG. 3 is an explanatory diagram showing a first example of the viewing angle improvement processing by the viewing angle improvement processing unit 13. As illustrated in FIG. 3, the moving image detection unit 131 determines whether the pixel is a moving image or a still image according to whether the difference between the gradation values of the pixels is larger or smaller than a predetermined difference threshold FTH. . For example, when the gradation value difference Δd> FTH, the pixel (x, y) is determined to be a moving image, and when the gradation value difference Δd ≦ FTH, the pixel (x, y) is a still image. It can be determined that there is. When the gradation of the image is, for example, 256 gradations, the difference threshold value FTH can be set to a value of about 0 to 16, for example. Note that the determination of a moving image or still image can determine whether the entire image is a moving image or a still image, and can also determine whether a part of the image is a moving image or a still image. it can. That is, the present embodiment can be applied not only when the entire image is a moving image or a still image, but also when a moving image and a still image are mixed in the image.

  The gradation difference parameter output unit 132 outputs a gradation difference parameter α (x, y) based on the flag signal output from the moving image detection unit 131. In the example of FIG. 3, the gradation difference parameter α (x, y) output from the gradation difference parameter output unit 132 is “1”.

  The high gradation image and low gradation image output unit 133 calculates the high gradation image and the low gradation image based on the input gradation d of the input image and the gradation difference parameter α (x, y). The input gradation d is also expressed as d (x, y).

  FIG. 4 is an explanatory diagram showing a first example of a method for calculating a high gradation image and a low gradation image by the high gradation image and low gradation image output unit 133. In FIG. 4, the horizontal axis represents the input gradation d, and the vertical axis represents the output gradation q. dm is the maximum value of the input gradation, and qm is the maximum value of the output gradation. A straight line connecting the point where the input gradation and the output gradation are 0 and the point where both the input gradation and the output gradation are maximum values (the straight line indicated by “dnom” in FIG. 4) is the viewing angle improvement process. This shows gradation conversion when not performed. That is, the gradation conversion dnom converts the input gradation to the output gradation without performing the viewing angle improvement process. In FIG. 4, for the sake of simplicity, tone conversion high (d (x, y)) is represented by high and tone conversion dlow (d (x, y)) is represented by dlow.

  The gradation conversion “dhigh” is gradation conversion applied to the calculation of a high gradation image. The gradation conversion dhigh applied to the pixel (x, y) is expressed by Expression (1) when the input gradation d is 0 ≦ d <dm / 2. When dm / 2 ≦ d ≦ dm, it is expressed by Expression (2). That is, the tone conversion high can be represented by two straight lines as shown in FIG.

  The gradation conversion dlow is gradation conversion applied to the calculation of a low gradation image. The gradation conversion dlow applied to the pixel (x, y) is expressed by Expression (3) when the input gradation d is 0 ≦ d <dm / 2. In the case of dm / 2 ≦ d ≦ dm, it is expressed by Expression (4). That is, the gradation conversion dlow can be represented by two straight lines as shown in FIG.

  The gradation conversion high and dlow can be calculated from the input gradation d by the viewing angle improvement processing unit 13 based on the equations (1) to (4). Further, the input gradation and the output gradation indicated by the gradation conversion high and dlow may be recorded in an LUT (Look Up Table), and the output gradation for the input gradation d may be read out.

  The high gradation video and low gradation video selection unit 134 assigns the pixels of the image to either the high gradation pixel or the low gradation pixel based on the pattern signal generated by the pattern signal generation unit 135 and assigns the pixel to the high gradation pixel. By converting pixel gradation values to higher gradation high gradation values and converting pixel gradation values assigned to low gradation pixels to lower gradation low gradation values, viewing angle improvement processing is performed. Do.

  FIG. 5 is a schematic diagram illustrating an example of a pattern signal generated by the pattern signal generation unit 135. The pattern signal generation unit 135 assigns the high gradation pixel and the low gradation pixel so as to form a lattice shape for each of one or a plurality of pixels of the image of each frame. That is, the pattern signal generation unit 135 generates a pattern signal that determines whether to assign a pixel of an image of each frame to a high gradation pixel or a low gradation pixel. If the coordinates of the pixels of one frame image are (x, y), the pattern signal can be expressed by p (x, y), and p (x, y) is, for example, “1” and “0”. It can be expressed by the binary value. When p (x, y) is “1”, the pixel is high (Hi), the pixel (x, y) is assigned to the high gradation pixel, “0” is low (Low), and the pixel (x, y) is Assigned to low gradation pixels.

  The pattern signal generation unit 135 acquires the synchronization signal of the input video, counts the data enable signal that is the synchronization signal in dot units and line units, sets the value counted in dot units as the x coordinate, and counts in line units Is the y coordinate. The pattern signal illustrated in FIG. 5 is a staggered pattern (lattice pattern) of one line and one dot. As the distance between “1” is high (Hi) and “0” is low (Low), the feeling of roughness is reduced and the fineness can be enhanced.

  The high gradation video and low gradation video selection unit 134 then outputs p (x, y) = “1”, that is, when the pattern signal is high, the output video q (x, y) = high (d (x, y ), Α) and p (x, y) = “0”, that is, when the pattern signal is low, output video q (x, y) = dlow (d (x, y), α) is output. .

  As described above, the viewing angle improvement processing unit 13 performs processing with a large degree of viewing angle improvement on the pixel (x, y) determined to be a moving image, and determines a pixel ( For x, y), a process with a small degree of viewing angle improvement is performed. The process with a small degree of viewing angle improvement includes the case where the viewing angle improvement process is not performed. That is, as shown in FIG. 3, the viewing angle improvement processing is performed on the pixel (x, y) determined to be a moving image, and the pixel (x, y) determined to be a still image is performed. The viewing angle improvement process can be prevented from being performed.

  As shown in FIG. 3, the viewing angle improvement processing unit 13 determines the gradation when the pattern signal high (Hi) is assigned to the pixel (x, y) determined to be a moving image. When conversion high is applied and pattern signal low is assigned, gradation conversion dlow is applied.

  6 is a schematic diagram illustrating an example of an input image, FIG. 7 is a schematic diagram illustrating an example of an output image when the input image is a moving image, and FIG. 8 is an output image when the input image is a still image. It is a schematic diagram which shows an example. In FIGS. 6 to 8, the level of gradation is represented by the density of the line / point of the pattern for convenience. FIG. 6 shows an input image for one frame, which is represented by 8 × 8 pixels for convenience. As shown in FIG. 6, pixels indicated by white are pixels whose input gradation is high, and pixels indicated by black are pixels whose input gradation is low. In addition, pixels indicated by diagonal lines are pixels whose input gradation is medium gradation.

  High gradation and low gradation pixels are relatively unaffected by the viewing angle, and a phenomenon such as whitening does not appear remarkably even when the liquid crystal panel (screen) is viewed obliquely. On the other hand, pixels of medium gradation are affected by the viewing angle, and when the liquid crystal panel is viewed from an oblique direction, a phenomenon such as whitening appears.

  Therefore, as shown in FIG. 7, when the input image is a moving image, a high-gradation pixel is applied so that a viewing angle improvement process is performed on a medium-gradation pixel and the luminance is not shifted even when viewed from an oblique direction. And low gradation pixels are arranged so as to form a grid, so that it is simulated to be close to a medium gradation (intermediate luminance). If the image is a moving image, even if the pixels with high gradation and pixels with low gradation are arranged in a grid, the degree of fineness of the image (video) is less likely to be lost, and whitening is suppressed. can do.

  On the other hand, as shown in FIG. 8, when the input image is a still image, the viewing angle improvement process is not performed on the mid-tone pixels. When the image is a still image, the degree of fineness of the image (video) is highly impaired when the high gradation pixels and the low gradation pixels are arranged in a lattice pattern. Therefore, when the input image is a still image, the fineness of the image (video) can be maintained without performing the viewing angle improvement processing.

  FIG. 9 is an explanatory diagram illustrating an example of luminance characteristics of the liquid crystal display device 100 according to the first embodiment. In FIG. 9, the horizontal axis indicates the standardized input gradation (0 to 1) to the liquid crystal panel, and the vertical axis indicates the standardized luminance (0 to 1). That is, the input gradation is standardized so that the maximum gradation is 1, and is normalized so that the maximum value of luminance measured in the front and oblique directions of the liquid crystal panel is 1. In FIG. 9, the straight line indicated by the symbol A indicates the luminance measured in front of the liquid crystal panel with respect to the input gradation. The luminance characteristic indicated by the symbol A represents the luminance measured in front of the liquid crystal panel, so that there is no phenomenon such as so-called whitening.

  Curves indicated by symbols B and C are luminances measured in an oblique direction of the liquid crystal panel with respect to the input gradation, symbol B is for a moving image, and symbol C is for a still image. The luminance measured in the oblique direction of the liquid crystal panel is higher than the luminance measured in the front. In addition, the brightness of the still image indicated by the symbol C is higher than that of the moving image indicated by the symbol B. That is, in the case of a still image, the fineness of the image (video) is maintained even when the shift to the high luminance side when viewed from an oblique direction is large. In particular, it is possible to prevent loss of fineness in still images such as text display such as telop and OSD (On Screen Display) and photographs. On the other hand, in the case of a moving image, the shift to the high luminance side when viewed from an oblique direction can be suppressed, the intermediate luminance characteristic can be brought close to the luminance characteristic indicated by the symbol A, and so-called whitening can be suppressed.

  In the example of FIG. 3, the case where a constant of α (x, y) = 1 is used as the gradation difference parameter α (x, y) has been described. The gradation difference parameter α (x, y) is not limited to a constant, and can be any value from 0 to 1. Hereinafter, a case where the tone difference parameter α (x, y) is 0 ≦ α (x, y) ≦ 1 will be described.

  FIG. 10 is an explanatory diagram showing a second example of the viewing angle improvement processing by the viewing angle improvement processing unit 13. As in the case of FIG. 3, the moving image detection unit 131 determines whether the pixel is a moving image or a still image according to whether the difference in the gradation value of the pixel is larger or smaller than a predetermined difference threshold FTH. To do. For example, when the gradation value difference Δd> FTH, the pixel (x, y) is determined to be a moving image, and when the gradation value difference Δd ≦ FTH, the pixel (x, y) is a still image. It can be determined that there is.

  The gradation difference parameter output unit 132 outputs a gradation difference parameter α (x, y) based on the flag signal output from the moving image detection unit 131. For example, the gradation difference parameter output unit 132 outputs α (x, y) = α0 in the case of the moving image region, that is, when flag (x, y) = dg. The gradation difference parameter output unit 132 outputs α (x, y) = α1 in the case of a still image region, that is, when flag (x, y) = sg. Here, there is a relationship of 0 ≦ α0 <α1 ≦ 1.

  The gradation difference parameters α0 and α1 may be unique values for each liquid crystal panel or may be set from the outside. When setting is possible from the outside, for example, the user can set by remote control or button operation.

  The high gradation image and low gradation image output unit 133 calculates the high gradation image and the low gradation image based on the input gradation d of the input image and the gradation difference parameter α (x, y). The input gradation d is also expressed as d (x, y).

  FIG. 11 is an explanatory diagram showing a second example of a method for calculating a high gradation image and a low gradation image by the high gradation image and low gradation image output unit 133. In FIG. 11, the horizontal axis represents the input gradation d, and the vertical axis represents the output gradation q. dm is the maximum value of the input gradation, and qm is the maximum value of the output gradation. A straight line connecting the point where the input gradation and the output gradation are 0 and the point where both the input gradation and the output gradation are maximum values indicates the gradation conversion when the viewing angle improvement processing is not performed. is there. In FIG. 11, for the sake of simplicity, tone conversion dhigh (d (x, y), α) is represented by high (α), and tone conversion dlow (d (x, y), α) is dlow (α ).

  The gradation conversion high (α) is gradation conversion applied to the calculation of high gradation video. The tone conversion dhigh (α) applied to the pixel (x, y) is expressed by Expression (5) when the input tone d is 0 ≦ d <dm / 2, and the input tone When d is dm / 2 ≦ d ≦ dm, it is expressed by Expression (6). In equations (5) and (6), α is a tone difference parameter. That is, the gradation conversion dhigh can be represented by two straight lines that are bent at a point where the input gradation is dm / 2 and the output gradation is (1 + α) × qm / 2, as shown in FIG. When the tone difference parameter α increases, the high (α) shifts upward. When the tone difference parameter α is 1, the high (α) matches the high in FIG.

  The gradation conversion dlow (α) is gradation conversion applied to the calculation of a low gradation image. The gradation conversion dlow (α) applied to the pixel (x, y) is expressed by Expression (7) when the input gradation d is 0 ≦ d <dm / 2. When d is dm / 2 ≦ d ≦ dm, it is expressed by Expression (8). In equations (7) and (8), α is a tone difference parameter. That is, the gradation conversion dlow (α) is represented by two straight lines that are bent at a point where the input gradation is dm / 2 and the output gradation is (1−α) × qm / 2 as shown in FIG. Can do. When the gradation difference parameter α increases, dlow (α) shifts downward. When the gradation difference parameter α is 1, dlow (α) coincides with dlow in FIG. When the gradation difference parameter α is 0, both high (α) and dlow (α) have the maximum input gradation and output gradation, and the maximum input gradation and output gradation. Matches a straight line connecting points that are values.

  That is, when the gradation difference parameter α is increased, the gradation conversion high (α) and dlow (α) are moved away, and when the gradation difference parameter α is decreased, the gradation conversion high (α) and dlow (α) are reduced. It will approach.

  The high gradation video and low gradation video selection unit 134 then outputs p (x, y) = “1”, that is, when the pattern signal is high, the output video q (x, y) = high (d (x, y ), Α) and p (x, y) = “0”, that is, when the pattern signal is low, output video q (x, y) = dlow (d (x, y), α) is output. .

  As described above, the viewing angle improvement processing unit 13 performs processing with a large degree of viewing angle improvement on the pixel (x, y) determined to be a moving image, and determines a pixel ( For x, y), a process with a small degree of viewing angle improvement is performed.

  That is, as shown in FIG. 10, the viewing angle improvement processing unit 13 converts the gradation value of the pixel assigned to the high gradation pixel into the high gradation value of the higher gradation, and the pixel level assigned to the low gradation pixel. When the tone value is converted to a lower tone value with a lower tone, the viewing angle improvement processing unit 13 converts the tone value of the pixel for the pixel (x, y) determined to be a moving image. The difference between the high gradation value and the low gradation value to be generated is increased. The gradation difference parameter α is used as a parameter indicating the degree of viewing angle improvement.

  In addition, as shown in FIG. 10, the viewing angle improvement processing unit 13 converts the gradation value of the pixel assigned to the high gradation pixel into the high gradation value of the higher gradation, and the pixel level assigned to the low gradation pixel. When the tone value is converted to a lower tone value having a lower tone, the viewing angle improvement processing unit 13 determines that the tone value of the pixel is the pixel (x, y) determined to be a still image. The difference between the converted high gradation value and low gradation value is reduced. The gradation difference parameter α is 0 ≦ α ≦ 1. The gradation difference parameter α can be adjusted to the viewing angle and the fineness of the edge portion by the user confirming the image (video) and setting it to a desired value.

  That is, as shown in FIG. 10, when the viewing angle improvement processing unit 13 determines that the pixel is a moving image, the difference between the high gradation value and the low gradation value to which the gradation value of the pixel is converted is calculated as follows: When it is determined that the pixel is a still image, the input gradation is converted by setting the gradation value of the pixel larger than the difference between the high gradation value and the low gradation value to be converted.

  Then, as shown in FIG. 10, the viewing angle improvement processing unit 13 uses a large value (for example, α1) of the gradation difference parameter α for the pixel (x, y) determined to be a moving image, When the pattern signal high (Hi) is assigned, gradation conversion high is applied, and when the pattern signal low (Low) is assigned, gradation conversion dlow is applied.

  In addition, the viewing angle improvement processing unit 13 uses a small value of the gradation difference parameter α (for example, α0, α0 <α1) for the pixel (x, y) determined to be a still image, and the pattern signal. When high (Hi) is assigned, gradation conversion high is applied, and when pattern signal low (Low) is assigned, gradation conversion dlow is applied.

  FIG. 12 is a schematic diagram showing an example of an output image when the gradation difference parameter α is used. FIG. 12 shows an input image for one frame, which is represented by 8 × 8 pixels for convenience. In FIG. 12, pixels indicated by white are pixels whose input gradation is high, and pixels indicated by black are pixels whose input gradation is low. In addition, the lattice pattern pixels are pixels to which the gradation conversion high (α) is applied, and the dot pattern pixels are pixels to which the gradation conversion dlow (α) is applied. Tone pixel.

  By adjusting the tone difference parameter α in the range of 0 <α <1, the jaggedness and shakiness of the edge portion of the image become less noticeable compared to the case of the moving image of FIG. 7 corresponding to α = 1. A sense of fineness can be maintained.

  FIG. 13 is an explanatory diagram showing an example of luminance characteristics of the liquid crystal display device 100 when the gradation difference parameter α is used. In FIG. 13, the horizontal axis indicates the standardized input gradation (0 to 1) to the liquid crystal panel, and the vertical axis indicates the standardized luminance (0 to 1). In FIG. 11, the straight line indicated by the symbol A indicates the luminance measured on the front surface of the liquid crystal panel with respect to the input gradation. The luminance characteristic indicated by the symbol A represents the luminance measured in front of the liquid crystal panel, so that there is no phenomenon such as so-called whitening.

  Curves indicated by symbols D and E are luminances measured in an oblique direction of the liquid crystal panel with respect to the input tone, and symbol D is a case where the tone difference parameter α is large (for example, α1). E is a case where the gradation difference parameter α is small (for example, α0, α0 <α1).

  As can be seen from FIG. 13, when the gradation difference parameter α is increased, the brightness characteristic approaches the linear brightness characteristic indicated by the symbol A (the brightness measured in front of the liquid crystal panel), and thus whitening can be suppressed. That is, as the gradation difference parameter α approaches 0 to 1, whitening can be suppressed.

  On the other hand, if the gradation difference parameter α is reduced, the edge of the image becomes less noticeable and it is possible to prevent the fineness from being impaired. That is, the closer the gradation difference parameter α is to 1 to 0, the more fineness can be maintained. By providing the liquid crystal display device 100 with an appropriate configuration or function for setting the gradation difference parameter α to a desired value, the user can check the image and adjust the gradation difference parameter α to improve the viewing angle. It becomes possible to maintain and adjust the fineness of the edge portion as desired.

  FIG. 14 is a schematic diagram illustrating an example of a state of an image obtained by the viewing angle improvement process of the liquid crystal display device 100 according to the first embodiment. As shown in FIG. 14, it is assumed that the input video has a moving image area determined as a moving image and a still image area determined as a still image. In the moving image area, whitening can be suppressed by increasing the difference between the high gradation and the low gradation accompanying the viewing angle improvement processing (the gradation difference parameter α is large, for example, α = α1). However, at the edge of the intermediate gradation, the high gradation pixels and the low gradation pixels are arranged in a lattice shape, and the edges are jagged.

  In the still image area, the difference between the high gradation and the low gradation associated with the viewing angle improvement processing is reduced (the gradation difference parameter α is reduced, for example, α = α0, α0 <α1), thereby improving the sense of detail. Can be maintained. In the example of FIG. 14, the edge with the intermediate gradation is substantially linear.

  According to the present embodiment, when the input video is a moving image and a telop portion exists in a part of the moving image, the telop portion is determined as a still image region, and a fine feeling can be maintained in the still image region, The edge with the intermediate gradation is linear. Then, the part other than the telop portion is determined as a moving image, and whitening can be suppressed in the moving image area.

  In the above-described embodiment, each pixel in the image of each frame is assigned to either the high gradation pixel or the low gradation pixel. However, the high gradation pixel and the low gradation pixel are assigned by the pattern signal. The method is not limited to this.

  FIG. 15 is a schematic diagram illustrating another example of the pattern signal generated by the pattern signal generation unit 135. In the example of FIG. 15, unlike the example of FIG. 5, a staggered pattern of one line and two dots is formed. Thereby, it is possible to prevent the polarity of the liquid crystal panel 30 from matching the high gradation pixel and the low gradation pixel. In order to maintain the fineness of the video, the example of FIG. 5 is preferable to the example of FIG. 15. However, depending on the characteristics of the video, the method of FIG. It is only necessary to select whether to adopt the method.

  In the above-described embodiment, when determining whether an image (video) is a moving image or a still image, the coordinates of each of two time-series images of the current frame and the latest frame are the same pixel. Although the determination is based on the difference between the gradation values, the determination method for a moving image or a still image is not limited to this.

  For example, the viewing angle improvement processing unit 13 calculates a difference in gradation value between a pixel of an image of an arbitrary frame and a peripheral pixel of the pixel. The peripheral pixels may be, for example, 8 pixels around an arbitrary pixel, 4 pixels above and below, left and right, 2 pixels left and right, or 2 pixels above and below. The gradation value of the peripheral pixels may be an average value obtained by summing the gradation values of the peripheral pixels and dividing by the number of peripheral pixels, or may be a median value.

  The viewing angle improvement processing unit 13 determines that the pixel is a moving image when the difference between the gradation values of the pixel and the surrounding pixels is larger than a predetermined difference threshold, and determines the gradation values of the pixels and the surrounding pixels. When the difference is smaller than a predetermined difference threshold, it can be determined that the pixel is a still image.

(Embodiment 2)
As shown in FIG. 14, when the input video is a moving image and there is a still image area such as a telop part in the moving image, when the video scene changes, the still image area changes to a moving image area, or the moving image The area may change to a still image area. In this case, when the liquid crystal panel is viewed from an oblique direction, the color may suddenly change and appear unnatural. For example, when a stationary telop suddenly scrolls, the color changes, which makes it look unnatural. Hereinafter, a method for improving such a phenomenon will be described.

  FIG. 16 is a time chart showing a change state based on the time constant of the gradation difference parameter α by the viewing angle improvement processing unit 13 according to the second embodiment, and FIG. 17 shows luminance due to a change between a still image and a moving image. It is explanatory drawing which shows an example of the mode of a change. The configurations of the liquid crystal display device 100, the viewing angle improvement processing unit 13, and the like are the same as those in the first embodiment, and thus description thereof is omitted.

  The upper chart in FIG. 16 shows how the gradation difference Δd (t) changes when the still image region of the input video changes to the moving image region at time t0, for example. In this case, as described above, when the liquid crystal panel is viewed from an oblique direction, the hue suddenly changes and looks unnatural.

  As illustrated in FIG. 17, this is because the luminance characteristic in the case of the still image indicated by the symbol E in the case where the luminance is q1 changes from the still image to the moving image. It can also be seen from the fact that the brightness characteristic changes rapidly to the brightness q2. In addition, when it changes from a moving image to a still image, it looks unnatural as well.

  The moving image detecting unit 131 determines a time point when the still image changes to a moving image or a time point when the moving image changes to a still image. When the moving image detecting unit 131 determines that the moving image detecting unit 131 changes from a still image to a moving image, the gradation difference parameter output unit 132 as the adjusting unit sets a gradation value parameter that is a difference between the high gradation value and the low gradation value, From this point in time, adjust to increase gradually with the required time constant. In addition, when the moving image detection unit 131 determines that the moving image detection unit 131 changes from a moving image to a still image, the gradation difference parameter output unit 132 requires a gradation value parameter that is a difference between the high gradation value and the low gradation value from the time point. The time constant is adjusted to gradually decrease.

  For example, as shown in the lower chart of FIG. 16, the tone difference parameter when the video before time t0 is a still image is α0, and the tone difference parameter when the video is a moving image is α1 (α1> α0). ), The gradation difference parameter α is gradually increased from α0 to α1 from time t0. The time (time constant) until the gradation difference parameter α becomes from α0 to α1 can be set as appropriate, but can be set to, for example, a time corresponding to 3 to 5 frames. In this way, when changing from a still image to a moving image, or from a moving image to a still image, the gradation difference parameter is changed to gradually increase or decrease gradually from the time of the change. By giving a constant, you can gradually increase (strengthen) the improvement of the viewing angle, or gradually decrease (decrease) the improvement of the viewing angle, and suppress the unnatural state, You can make the video look natural.

(Embodiment 3)
FIG. 18 is a block diagram illustrating an example of a configuration of a liquid crystal display device 110 as an image processing apparatus according to the third embodiment. The difference from the first embodiment is that an image processing unit 40 is provided and a frame memory 41 used together with the image processing unit 40 is provided instead of the frame memory 12. In addition, the same code | symbol is attached | subjected to the location similar to Embodiment 1, and description is abbreviate | omitted.

  The image processing unit 40 has a function of performing predetermined image processing on the video signal. The predetermined image processing is, for example, enlargement processing or reduction processing, frame rate conversion processing, and the like, but is not limited thereto.

  The frame memory 41 is a frame memory used for processing performed by the image processing unit 40. In the third embodiment, the frame memory used by the viewing angle improvement processing unit 13 and the frame memory used by the image processing unit 40 are shared. , Combined use.

  More specifically, the image processing unit 40 stores the acquired video signals d (t), d (t-1),... In the frame memory 41 for each video signal of one frame in order to perform predetermined processing. . The image processing unit 40 outputs the processed video signal f (d (t), d (t-1)) and the difference value Δd (t) of the gradation values between frames to the viewing angle improvement processing unit 13.

  The viewing angle improvement processing unit 13 performs the same processing as in the first embodiment based on the video signal f (d (t), d (t-1)) and the difference value Δd (t). Thereby, it is not necessary to provide a dedicated frame memory for the viewing angle improvement processing unit 13, and the circuit scale can be reduced.

(Embodiment 4)
In the above-described embodiment, the gradation difference parameter output unit 132 outputs the gradation difference parameter α (x, y) = α0 in the case of the moving image area, and the gradation difference parameter α (x in the case of the still image area. Y) = α1 is output, but the present invention is not limited to this.

  FIG. 19 is an explanatory diagram illustrating an example of an output mode of the gradation difference parameter α by the gradation difference parameter output unit 132 according to the fourth embodiment. As shown in FIG. 19A, it is assumed that a part of the input video (a region indicated by a rectangular frame in the drawing) is a still image region and the rest is a moving image region. As shown in FIGS. 19B to 19D, the gradation difference parameter α is output by the gradation difference parameter output unit 132 in three modes: mode 1, mode 2, and mode 3.

  As shown in FIG. 19B, mode 1 is a mode in which different gradation difference parameters are output by dividing a still image region and a moving image region. The gradation difference parameter output unit 132 outputs a gradation difference parameter α0 for the still image area, and outputs a gradation difference parameter α1 (α1> α0) for the moving image area. By using mode 1, it is possible to separate a portion for enhancing the effect of the viewing angle improvement processing and a portion for weakening.

  As illustrated in FIG. 19C, mode 2 is a mode in which the entire screen is a still image when the input video includes a still image area. In this case, the gradation difference parameter output unit 132 outputs the gradation difference parameter α0 for the entire screen.

  As shown in FIG. 19D, mode 3 is a mode in which the entire screen is a moving image when the moving image area is included in the input video. In this case, the gradation difference parameter output unit 132 outputs the gradation difference parameter α1 for the entire screen. By using mode 2 or 3, when the liquid crystal panel 30 is viewed from an oblique direction, it is possible to prevent a difference in hue from being displayed in the display portion.

  That is, the gradation difference parameter output unit 132 as the selection unit, when the moving image detection unit 131 determines that both a moving image and a still image exist in the pixel of the image, Either a gradation difference parameter α1 that is a difference from the gradation value or a gradation difference parameter α1 that is a difference between a high gradation value and a low gradation value that are used when the image is determined to be a still image is selected. The viewing angle improvement processing unit 13 converts the gradation values of all pixels of the image, that is, pixels of the entire screen, using the selected gradation difference parameter.

  The above-described modes 1 to 3 can be configured to be changed by the user with a remote control or button operation. Further, the mode of the gradation difference parameter output unit 132 may be changed in conjunction with the mode of the television (TV). For example, when the television mode is the standard mode or the cinema mode, the mode of the gradation difference parameter output unit 132 is changed to mode 1. Thereby, a moving image part can strengthen the viewing angle improvement processing effect, and can suppress whitening. In addition, a still image portion (for example, a telop or a subtitle portion) can weaken the viewing angle improvement processing effect and maintain a fine feeling. When the television mode is the PC mode, the mode of the gradation difference parameter output unit 132 is changed to mode 2. When a moving image is displayed on a small screen, it is possible to weaken the viewing angle improvement processing effect and maintain the fineness. When a moving image is displayed on a full screen, the viewing angle improvement processing effect can be strengthened and whitening can be suppressed.

  As described above, the image processing apparatus according to the embodiment of the present invention assigns an image pixel composed of a plurality of pixels to either a high gradation pixel or a low gradation pixel, and assigns the pixel to the high gradation pixel. A conversion processing unit (132, 133) that converts a gradation value of a pixel into a higher gradation value of a higher gradation and converts a gradation value of a pixel assigned to the low gradation pixel into a lower gradation value of a lower gradation. 134) includes a determination unit (131) that determines whether the pixel of the image is a moving image or a still image, and the conversion processing unit includes the determination unit and the pixel is a moving image. If the determination unit determines that the pixel is a still image, the difference between the high gradation value and the low gradation value, to which the gradation value of the pixel is converted when determined, is determined. Is converted larger than the difference between the high gradation value and the low gradation value to be converted. Characterized in that you have to so that.

  The image processing method according to the embodiment of the present invention assigns a pixel of an image composed of a plurality of pixels to either a high gradation pixel or a low gradation pixel, and the gradation of the pixel assigned to the high gradation pixel. In the image processing method of converting a value to a higher gradation value of a higher gradation and converting a gradation value of a pixel assigned to the low gradation pixel to a lower gradation value of a lower gradation, the pixel of the image is a moving image Or a step of determining whether the pixel is a still image and a difference between the high gradation value and the low gradation value to which the gradation value of the pixel is converted when it is determined that the pixel is a moving image, And converting the gradation value of the pixel to be larger than the difference between the high gradation value and the low gradation value to be converted when it is determined that the pixel is a still image.

  In the present embodiment, the determination unit (131) determines whether any pixel of the image is a moving image or a still image. The conversion processing unit (132, 133, 134) converts the gradation value of the pixel assigned to the high gradation pixel to the high gradation value of the higher gradation, and lowers the gradation value of the pixel assigned to the low gradation pixel. When converting to a low gradation value of gradation, the difference between the high gradation value and the low gradation value to which the gradation value of the pixel is converted for the pixel (x, y) determined to be a moving image Increase Then, with respect to the pixel (x, y) determined to be a still image, the conversion processing unit (132, 133, 134) generates a high gradation value and a low gradation value to which the gradation value of the pixel is converted. Reduce the difference between. As a result, it is possible to improve the viewing angle without impairing the fineness of a still image and suppressing whitening in a moving image.

  An image processing apparatus according to an embodiment of the present invention includes a difference calculation unit (131) that calculates a difference between gradation values of corresponding pixels of one time-series image and another image, and the determination unit (131) is characterized in that it is determined whether the pixel is a moving image or a still image according to whether a difference in gradation value of the pixel is larger or smaller than a predetermined difference threshold value. .

  In the present embodiment, the difference calculation unit (131) calculates the difference between the tone values of the corresponding pixels of one time-series image and another image. The determination unit (131) determines whether the pixel is a moving image or a still image according to whether the difference between the gradation values of the pixels is larger or smaller than a predetermined difference threshold FTH. For example, when the gradation value difference Δd> FTH, the pixel (x, y) is determined to be a moving image, and when the gradation value difference Δd ≦ FTH, the pixel (x, y) is a still image. It can be determined that there is. Thus, the present embodiment can be applied even when a moving image and a still image are mixed in the image.

  The image processing apparatus according to the present invention includes a difference calculation unit (131) that calculates a difference in gradation value between a pixel of the image and a peripheral pixel of the pixel, and the determination unit (131) includes the pixel and the peripheral It is characterized in that it is determined whether the pixel is a moving image or a still image depending on whether the difference in gradation value from the pixel is larger or smaller than a predetermined difference threshold value.

  In the present embodiment, the difference calculation unit (131) calculates a difference in gradation value between a pixel of an image of an arbitrary frame and a peripheral pixel of the pixel. The peripheral pixels may be, for example, 8 pixels around an arbitrary pixel, 4 pixels above and below, left and right, 2 pixels left and right, or 2 pixels above and below. The gradation value of the peripheral pixels may be an average value obtained by summing the gradation values of the peripheral pixels and dividing by the number of peripheral pixels, or may be a median value. The determination unit (131) determines that the pixel is a moving image when the difference in gradation value between the pixel and the surrounding pixel is larger than a predetermined difference threshold, and the difference in gradation value between the pixel and the surrounding pixel is predetermined. If it is smaller than the difference threshold, it can be determined whether the pixel is a still image.

  An image processing apparatus according to an embodiment of the present invention includes an assigning unit (14) that assigns a high gradation pixel and a low gradation pixel so as to form a lattice pattern for each of one or a plurality of pixels of the image. And

  In the present embodiment, the assigning unit (14) assigns the high gradation pixels and the low gradation pixels so as to form a lattice pattern for each of one or a plurality of pixels of the image. Thereby, there is little feeling of roughness and a feeling of fineness can be made high.

  In the image processing apparatus according to the embodiment of the present invention, the determination unit (131) determines a time point when the still image changes to a moving image or a time point when the moving image changes to a still image, and the high gradation value And an adjustment unit (132) for adjusting the difference between the low gradation value and the low gradation value so as to gradually increase or decrease gradually from the time point.

  In the present embodiment, the determination unit (131) determines the time point when the still image changes to the moving image or the time point when the moving image changes to the still image. When changing from a still image to a moving image, the adjustment unit (132) adjusts the gradation value parameter, which is the difference between the high gradation value and the low gradation value, so that the gradation value parameter gradually increases from the time point with a required time constant. . In addition, when changing from a moving image to a still image, the adjustment unit (132) should gradually reduce the gradation value parameter, which is the difference between the high gradation value and the low gradation value, with a required time constant from that time point. adjust. Thereby, the state which looks unnatural can be suppressed and an image | video can be made to look natural.

  The image processing apparatus according to the embodiment of the present invention is used when the determination unit (131) determines that both a moving image and a still image exist in the pixel of the image, and the determination unit determines that the image is a moving image. A selection unit (132) is provided for selecting one of a difference between the high gradation value and the low gradation value and a difference between the high gradation value and the low gradation value used when the determination unit determines that the image is a still image. The conversion processing units (132, 133, 134) convert the gradation values of all the pixels of the image using the difference between the high gradation value and the low gradation value selected by the selection unit. It is characterized by being.

  In the present embodiment, the selection unit (132) is used when the determination unit (131) determines that both a moving image and a still image exist in the pixel of the image and the determination unit determines that the image is a moving image. Either the difference between the high gradation value and the low gradation value or the difference between the high gradation value and the low gradation value used when the determination unit determines that the image is a still image is selected. The conversion processing units (132, 133, 134) convert the gradation values of all the pixels of the image using the difference between the high gradation value and the low gradation value selected by the selection unit. For example, when the input video includes a still image region and a moving image region, the gradation difference parameter α0 used for the still image is selected for the entire screen. When the input video includes a still image region and a moving image region, the gradation difference parameter α1 used for the moving image is selected for the entire screen. Thereby, when the liquid crystal panel is viewed from an oblique direction, it is possible to prevent a difference in color from appearing in the display portion.

DESCRIPTION OF SYMBOLS 11 Video signal input part 12 Frame memory 13 View angle improvement process part 131 Movie detection part 132 Gradation difference parameter output part 133 High gradation image and low gradation image output part 134 High gradation image and low gradation image selection part 135 Pattern signal Generation unit 20 Liquid crystal drive unit 30 Liquid crystal panel 40 Image processing unit 41 Frame memory

Claims (7)

An image pixel composed of a plurality of pixels is assigned to either a high gradation pixel or a low gradation pixel, and the gradation value of the pixel assigned to the high gradation pixel is converted into a higher gradation value, In an image processing apparatus including a conversion processing unit that converts a gradation value of a pixel assigned to a low gradation pixel into a lower gradation value of a lower gradation,
A determination unit that determines whether a pixel of the image is a moving image or a still image;
The conversion processing unit
When the determination unit determines that the pixel is a moving image, the difference between the high gradation value and the low gradation value to which the gradation value of the pixel is converted is determined, and the pixel is a still image in the determination unit. The image processing apparatus is characterized in that the gradation value of the pixel is converted to be larger than the difference between the high gradation value and the low gradation value to be converted. A difference calculation unit that calculates a difference between gradation values of corresponding pixels of one time-series image and another image,
The determination unit
2. The method according to claim 1, wherein whether the pixel is a moving image or a still image is determined according to whether a difference in gradation value of the pixel is larger or smaller than a predetermined difference threshold value. Image processing apparatus. A difference calculation unit that calculates a difference in gradation value between a pixel of the image and a peripheral pixel of the pixel;
The determination unit
2. The method according to claim 1, wherein the pixel is determined to be a moving image or a still image depending on whether a difference in gradation value between the pixel and a peripheral pixel is larger or smaller than a predetermined difference threshold value. Item 8. The image processing apparatus according to Item 1.   The allocation part which allocates a high gradation pixel and a low gradation pixel so that it may form a grid | lattice form for every 1 or several pixel of the said image is provided, The any one of Claim 1 to 3 characterized by the above-mentioned. The image processing apparatus described. The determination unit
It is designed to determine when to change from a still image to a movie or when to change from a movie to a still image.
5. The apparatus according to claim 1, further comprising an adjustment unit that adjusts a difference between the high gradation value and the low gradation value so as to gradually increase or decrease gradually from the time point. The image processing apparatus according to item 1. When the determination unit determines that both the moving image and the still image exist in the pixel of the image, the difference between the high gradation value and the low gradation value used when the determination unit determines that the image is a moving image and the determination unit A selection unit that selects either the difference between the high gradation value and the low gradation value used when the image is determined to be a still image;
The conversion processing unit
6. The gradation values of all pixels of the image are converted using a difference between a high gradation value and a low gradation value selected by the selection unit. The image processing apparatus according to any one of the above. An image pixel composed of a plurality of pixels is assigned to either a high gradation pixel or a low gradation pixel, and the gradation value of the pixel assigned to the high gradation pixel is converted into a higher gradation value, In an image processing method for converting a gradation value of a pixel assigned to a low gradation pixel into a lower gradation value of a lower gradation,
Determining whether the pixels of the image are moving images or still images;
The difference between the high gradation value and the low gradation value to which the gradation value of the pixel is converted when it is determined that the pixel is a moving image, and when the pixel is determined to be a still image, An image processing method comprising: converting a gradation value of a pixel to be larger than a difference between the high gradation value and the low gradation value to be converted.

Images