KR100302142B1 - Fixed Quantity Evaluation Method of Dynamic False Contour Phenomena of Plasma Display - Google Patents

Abstract

The present invention relates to a method for quantitative evaluation of video pseudo-contour phenomena in a plasma display (PDP), which detects edges of an original image and a simulation result image to show only edge regions, calculates correlation between two edge images, The step of moving the simulation result image to the maximum point (S100), and to measure the output brightness of the input signal of the display to create a 1D-LUT, using this to convert the grayscale value of the original image to the output value of the monitor (S200) and applying a power function to the Weber's law indicating that human vision is more sensitive to errors as the luminance is lowered (S300), and small errors are generated by processing having a large error value and contour processing. Applying the threshold value of the suppressed simulation result image to the result of Weber's law (S400); Since the increase in the gray level difference between cells decreases the sensitivity to the error of time at the edge part, applying a weighting function to the gray level difference between two pixels in the original image (S500), and calculating the mean squared error (MSE) By performing the step of applying (S600) to quantify the pseudo contour matching the visual experiment results.

Description

Fixed Quantity Evaluation Method of Dynamic False Contour Phenomena of Plasma Display}

The present invention relates to a quantitative evaluation method of a pseudo pseudo contouring phenomenon in a plasma display (Plasma Display or Plasma Display Panel; PDP), and more particularly, position correction, display gamma transform, and Weber's law (Weber's). Law), the threshold of the error, and the weight function of the gray scale difference in the original image to quantify the degree of pseudo contour occurring in the plasma display, The present invention relates to a method of quantitative evaluation of moving picture pseudo contour phenomenon in a plasma display which can evaluate pseudo contour degree of a subfield pattern at a similar speed with a small amount of calculation.

In general, plasma is a gas that is sufficiently ionized and conductive and is affected by a magnetic field. There are almost equal numbers of negative and positive charged particles together with neutral particles, and the entire gas is neutral. It is fully ionized at high temperatures of 20,000 K and above. Among the solids, the plasma exists in the form of either a donor charged positively with electrons or an acceptor charged negatively with holes. There is also a plasma present in the form of holes and electrons in the intrinsic semiconductor.

The plasma display (display device) using plasma is a flat panel display device using a light emitting phenomenon caused by gas discharge. The plasma display panel has two glass plates facing each other with the electrode forming surface inward and the discharge gas is hermetically sealed. Structure. As the discharge gas, a mixed dilute gas mainly composed of neon is used, and the light emitting display color is vermilion. A high voltage of about 200V is required for driving the panel, but since the threshold characteristics of the discharge start are very steep and there is an accumulation effect, a large capacity display can be performed by raster scanning pixels arranged in two dimensions for line sequential driving. Can be. It is used in various information terminal display devices, including portable personal computers. In addition, full color is also possible by the method in which the phosphor coated on the inner surface is emitted by ultraviolet rays generated by the discharge phenomenon. It is expected to realize future wall-mounted television.

Such a conventional plasma display has recently encountered a problem of image quality. Currently, the quality of plasma displays is inferior to that of CRTs in general monitors, and the contrast is particularly low.

Since the CRT was selected as a display in the conventional NTSC system, an unexpected problem arising in a plasma display having a completely different light emission and display principle is a matter of course, and one of such problems is a moving picture pseudo contour. Pseudo contour is a phenomenon in which an image is observed to be distorted when the viewpoint moves on the display screen. Its occurrence depends on the product of the pixel emission time length and the movement speed of the view point and the temporal nonuniformity of the light emission. Different levels are required, such as gradation or halftone of intermediate brightness) or color disturbances.

Pseudo-contour phenomena of plasma displays can be evaluated as directly viewed by a person through a display device, or averaged after calculating the simple mean squared error (MSE) of the original image in the image as a result of computer simulation. Calculated) Evaluate using the calculation process. Evaluation using a direct plasma display is time consuming and expensive. And, in the case of simple MSE calculation, the difference between the original image and the error of the invisible part is greater. For example, as a result of the simulation, since the image is different from the original image, if there is no position correction, the error of the portion is larger than the pseudo contour due to the inconsistency in the edge of the two images. In addition, since the display device characteristics and the visual characteristics are not taken into consideration, it is not a quantification method that reflects pseudo contours well.

In order to reduce the pseudo contour of the moving image in the plasma display, first, a method in which light emission nonuniformity is reduced may be set to a sufficiently narrow range of light emission within one field such as a CRT. That is, the maximum light emission period may be made as short as possible. However, since plasma displays have tried to lengthen the light emission period in order to increase the brightness, this method is not desirable, and another method of reducing the temporal nonuniformity of light emission, on the contrary, makes the light emission period as uniform as possible spatially on the time or in the retina To disperse.

Second, the disturbance of the generated gradation is made inconspicuous. There is a method of error diffusion. It is often used when displaying an image with two values, whether or not to paint ink, such as printing. If the display of a point is too bright, it will spread the disturbance by darkening the surroundings. In addition, the disturbance of the bit display is used to spread the disturbance in three dimensions in time and space.

Third, equalizing pulses are applied to make the brightness of the original image and the image actually displayed equal. Since grayscale disturbances can be predicted in advance, if dark disturbances are expected to occur, correction light emission may be applied to the original signal corresponding to this portion, and in the case where bright disturbances are expected, the light emission intensity of the original signal may be reduced. If the correction is made corresponding to the moving speed and the direction of the image, the image quality is further improved.

The present invention is to overcome the conventional problem by reducing the pseudo contour of the video generated in the plasma display as described above, the position correction process, display gamma correction, visual nonlinearity of matching the position of the image as the simulation image and the original image Webber's law that characterizes, the threshold of error to ignore small errors, the weighting function of the gradation difference in the original image and the MSE (Mean Squared Error) calculation to quantify the degree of pseudo contour generated in the plasma display It is an object of the present invention to provide a pseudo contour quantification method in which the calculation result and the visual evaluation result are similar and match the visual evaluation with a small amount of calculation.

1 is a flow chart showing a quantitative evaluation of a pseudo pseudo contour phenomenon in a plasma display according to the present invention;

2 is a diagram showing a simulation result by a conventional subfield,

3 is a diagram showing a simulation result by the improved subfield in the present invention.

In order to achieve the above object, the present invention detects the edges of the original image and the simulation result image to represent only the edge region, calculates the correlation between the two edge images, and moves the simulation result image to a point where the correlation is maximum. And 1D-LUT by measuring the output luminance of the input signal of the display, and converting the gray level value of the original image into the output value of the monitor using the same, and the lower the luminance, the more sensitive the human vision is to errors. Approximating the power function with Weber's law, and applying the threshold value of the simulation result image to the result of Weber's law, which suppresses small errors by machining with many contours and having a large error value. Increasing the difference in gray level values between adjacent pixels in the original image is sensitive to visual errors at the edges. Therefore, the method reduces the gray level difference between the two pixels in the original image by applying a weighting function and applying the MSE calculation.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing the overall flow of the present invention.

Step S100 is to correct the position. The step of correcting the position is to solve the problem of excessive error in the edge part of the image due to the mismatch of the position when calculating the difference from the original image because the size of the image is different depending on the speed of the simulation. Use the following method.

First, the edges of the original image and the simulation result image are detected to show only the edge region. Second, the correlation between the two edge images is calculated. Third, the simulation result image is displayed at the point where the correlation is maximum. Move to match.

The degree of pseudo contour is calculated at the position determined by the above process.

In the step S200, the display gamma correction is performed. Since the display luminance of the input signal is exponential, the display device measures the output luminance of the input signal to create a 1D-LUT, and uses the original image. Converts the gradation value of to the output value of the monitor.

In step S300, Weber's law is executed. As the luminance decreases due to the non-linear nature of vision (darker than brighter places), the human vision is more sensitive to errors. Approximately apply the Weber's law of representation. Weber's law is applied as a function of power, the main method. The error meter up to step S300 is expressed by Equation 1.

Here, i ₁ (x, y) is the original image, i ₂ (x, y) is the simulation image, and G is display gamma correction.

In step S400, a process of applying a threshold is performed. That is, since the simulation result image mainly has a lot of contour processing and small errors are suppressed by processing having a large error value, the threshold value of the error is applied to the result of Equation 1 above.

Step S500 is a process of applying a weight to the difference between the gray scale values. As a result of the error threshold being applied, the difference between the gray scale values between adjacent pixels in the original image is increased to give a weight for the large error. Increasing, that is, the sensitivity to the human visual error in the edge portion is reduced, so as to apply the difference between the gray value of the two pixels in the original image as a weight function as in Equation 2, a constant a = 15 was used.

,

Where a is the decay index.

Step S600 shows a mean squared error (MSE) calculation, and the MSE calculates an average after calculating a sum of squares of the errors.

Here, M is the horizontal size (number of rows) of the image, and N is the vertical size (number of columns) of the image. In other words, it averages the total number of pixels.

The threshold of the error is set based on the visual experiment, and the simulation pattern is selected by selecting a good pattern and a bad pattern, and the visual experiment is performed using the visual pattern. The threshold is adjusted to match the ranking of the pattern given by the visual experiment.

The error calculation method was applied to 128 gradation 8-subfield pattern optimization. Table 1 compares the visual test results and the error calculation results.

Pattern number Image 1 Image 2 Visual rank MSE Proposed method Visual rank MSE Proposed method One One 63.22 0.39 One 87.04 0.14 2 2 65.62 1.05 2 89.46 0.27 3 3 71.46 1.83 3 86.26 0.46 4 4 60.81 1.83 4 65.67 1.32 5 5 107.95 2.50 5 131.84 2.11 6 6 98.76 3.93 6 151.11 4.01

Pattern number Image 3 Image 4 Visual rank MSE Proposed method Visual rank MSE Proposed method One One 46.87 0.29 One 139.73 0.17 2 2 47.16 0.40 2 144.193 0.22 3 3 49.37 0.75 3 119.09 0.36 4 4 45.72 1.45 4 161.36 1.15 5 5 68.85 2.19 5 260.53 1.07 6 6 75.47 4.16 6 293.62 1.94

Pattern number Image 5 Image 6 Visual rank MSE Proposed method Visual rank MSE Proposed method One One 139.22 0.25 One 165.69 0.27 2 2 142.82 0.50 2 171.72 0.43 3 3 127.87 0.86 3 138.41 0.74 4 4 104.75 1.39 4 169.25 1.45 5 5 215.69 3.50 5 304.28 2.02 6 6 225.31 3.25 6 339.98 3.03

Pattern number Image 7 Image 8 Visual rank MSE Proposed method Visual rank MSE Proposed method One One 38.67 0.81 2 104.20 0.11 2 2 39.58 1.18 3 108.60 0.26 3 3 39.27 2.05 One 96.06 0.46 4 4 40.98 2.31 4 98.35 0.68 5 5 61.74 3.92 5 176.34 1.61 6 6 71.10 2.98 6 230.87 2.67

Pattern number Image 9 Image 10 Visual rank MSE Proposed method Visual rank MSE Proposed method One One 66.44 0.22 2 64.38 0.25 2 2 67.44 0.41 3 65.86 0.35 3 3 55.17 0.66 One 56.55 0.58 4 4 70.52 1.15 4 88.29 1.63 5 5 111.86 1.95 5 112.77 2.38 6 6 140.87 3.68 6 119.31 4.82

Table 1 is an embodiment proposed by the present invention, and more specifically, to confirm whether or not the calculated quantitative value coincides with the human visual evaluation.

It calculates 60 simulation result images (10 images × 6 patterns = 60) by applying six subfield patterns (pattern numbers 1-6) to 10 images. That is, six simulation results were obtained for one image.

In addition, pseudo contour quantification values are calculated from the six simulation images by the method applied in the present invention. For example, the calculated value for pattern 1 of image 1 is 0.39 and the calculated value for pattern 2 is 1.05.

From the same simulation image, the pseudo contour degree can also be obtained by simple MSE calculation. This is to show that simple MSE calculations do not fit well. Here, the simple MSE calculation is obtained by averaging the error between the original image and the simulated image without using the method applied in the present invention, such as position correction or gamma correction. The MSE calculation used is shown in Equation 4.

Here, M is the horizontal size (number of rows) of the image, and N is the vertical size (number of columns) of the image. In other words, it averages the total number of pixels.

In addition, six simulation images were shown to each of the fifteen people, and the best ones were ranked. Thus, the final ranking is determined by combining the rankings suggested by the 15 people.

In addition, in Table 1, people rated pattern 1 as 1st and pattern 2 as 2nd ... pattern 6 as 6th (first column). If the calculation is done using only simple MSE (column 2), it does not match the ranking of people. That is, the MSE of pattern 4 (= 60.81) is smaller than the MSE of pattern 1 (= 63.22). On the other hand, using the quantitative evaluation method (third column) of the present invention, it can be seen that the rank of the human visual evaluation rank and the rank of the calculated values match.

In the present invention, the top 4 patterns and the middle 2 patterns were selected from the optimization results including the existing optimal patterns, and visual evaluation was performed using 10 general images. In Table 1, pattern numbers are numbers assigned to six patterns. The calculated error criterion is similar to visual evaluation except for images 8 and 10.

Visual evaluation was conducted by visualizing the ranking of six patterns per 10 images under the conditions of Table 2.

Highest brightness 45cd / m ² Guanqian Street 4h Ambient brightness Low Video size 256 × 256 (pixels) resolution 800 × 600 display Syncmaster 7x

Therefore, the pseudo contour simulation result by the improved subfield in the present invention is shown in Figure 2, it can be seen that there is a significant difference than the conventional simulation result, Figure 1. That is, FIG. 1 shows a conventional eight-field pattern (1 2 4 8 16 32 64 128), and shows the field pattern (8 1 2 64 128 32 16 4) used in FIG.

As described above, the quantitative evaluation method of the pseudo contour image in the plasma display according to the present invention includes the Weber's law indicating the nonlinear characteristics of the position correction process, display gamma correction, and vision, which match the position of the image as the simulation image. The error calculation result and the visual evaluation result are similar by quantifying the pseudo contour of the plasma display using the threshold of the error to ignore small errors, the weighting function of the gradation difference in the original image, and the MSE calculation. Has little advantage.

Claims (1)

Detecting edges of the original image and the simulation result image to represent only an edge region, calculating a correlation between the two edge images, and moving the simulation result image to a point where the correlation is maximum (S100); Generating a 1D-LUT by measuring an output luminance of an input signal of a display, and converting a gray value of an original image into an output value of a monitor by using the same; Approximating and applying the following power function to Weber's law indicating that human vision is more sensitive to error as the luminance is lowered (S300); (i ₁ (x, y); original image, i ₂ (x, y); simulated image, G; display gamma correction) Applying the threshold value of the simulation result image to the result of Weber's law to suppress the small errors by the machining having a large amount of contour processing and having a large error value (S400); In step S500, since the increase in the difference in gray values between adjacent pixels in the original image reduces the sensitivity to the error of time at the edge portion, the following weighting function is applied to the difference in gray values between two pixels in the original image; (a; attenuation index) Applying the next MSE (Mean Squared Error; calculating the average after calculating the sum of squares of errors) (S600) A quantitative evaluation method of a pseudo pseudo contour phenomenon in a plasma display (PDP), characterized in that for performing.