JP2005141204A - Image signal processing method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve image quality by making the color of afterglow the same as that of original image, in an image display device, using a color image display device having a plurality of luminous materials having different afterglow times. <P>SOLUTION: In an image signal processing method, used for the color image display device having the plurality of the luminous materials different in the afterglow time, a plurality of low-pass filters of different characteristics are applied in parallel with respect to a current field image signal to an image signal, corresponding to the luminous material of at least a short afterglow time. An elongation image signal, containing a pseudo-afterglow signal, is prepared by compositing these, and the pseudo-afterglow signal is added to only the necessary part, by compositing the current field image signal and the elongation image signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image signal processing method and an image signal processing apparatus for driving a color image display device having a plurality of light emitting materials having different afterglow times.

  A plasma display panel (PDP), which is attracting attention as a large-screen color image display device, uses phosphors of three colors, green, red, and blue, which emit light by ultraviolet excitation, as light emitting materials. However, phosphor materials that satisfy various conditions such as emission intensity and color purity are limited, and the present situation is that a group of green, red, and blue phosphor materials that satisfy all the conditions has not been obtained.

Among various conditions, the afterglow characteristics of the phosphor vary greatly depending on the emission color, and in particular, the difference between blue and green is large. When the afterglow time is defined as 1/10 afterglow time, for example, the blue afterglow time of BaMgAl ₁₀ O ₁₇ : Eu, which is a typical phosphor of blue, is several μs, whereas it is a green phosphor. The afterglow time of Zn ₂ SiO ₄ : Mn is long and has a value close to one field period (about 16.7 ms). Due to such a difference in afterglow time, a color that was not present in the original image may appear when displaying a moving image. For example, in an image in which a bright point moves, a green tail occurs behind the bright point, or a green image remains in a dark scene. In particular, when a green tail with high specific sensitivity occurs in a skin portion of a human image, it is very unsightly and the image quality is significantly deteriorated.

In order to improve the image quality deterioration due to the afterglow, the image signal of the previous field is superimposed on the image signal of the current field at a certain rate with respect to the image signal corresponding to the emission color of the phosphor having a short afterglow time. Accordingly, a method has been proposed in which the afterglow color is made to be the same as that of the original image in a pseudo manner to prevent unnatural color development and eliminate the uncomfortable feeling (see, for example, Patent Document 1).
JP 2002-14647 A

  However, as described above, in the method of superimposing the image signal of the previous field on the image signal of the current field at a certain rate, for example, when a bright white window pattern is moving in a dark background, the afterglow In some cases, a color difference occurs in the area where the image is generated, increasing the sense of incongruity. This is because the original afterglow seems to decrease exponentially as the distance from the window pattern increases, but when the previous field image signal is superimposed on the current field image signal, the pseudo afterglow is separated from the window pattern. This is thought to be because it no longer depends on

  The present invention relates to an image signal processing method and an image signal for improving the image quality by making the afterglow color the same as the original image even in an image display apparatus using a color image display device having a plurality of light emitting materials having different afterglow times. An object is to provide a processing apparatus.

  In order to achieve the above-mentioned object, the present invention parallelizes a plurality of low-pass filters having different characteristics to the current field image signal in order to add a pseudo afterglow signal to the image signal corresponding to the light emitting material having a short afterglow time. To create a decompressed image signal including a pseudo afterglow signal by combining them, and to combine the current field image signal and the decompressed image signal to add a pseudo afterglow signal only to the necessary part It is.

  According to the present invention, in an image display apparatus using a color image display device having a plurality of light emitting materials having different afterglow times, an image signal processing method for improving the image quality by making the afterglow color the same as the original image and An image signal processing apparatus can be provided.

  The invention according to claim 1 of the present invention is an image signal processing method used for a color image display device having a plurality of light emitting materials having different afterglow times, and an image corresponding to at least a light emitting material having a short afterglow time. An image signal processing method is characterized in that a pseudo afterglow signal whose luminance changes in a polygonal line shape is generated from a current field image signal, and the pseudo afterglow signal is added to the current field image signal.

  According to a second aspect of the present invention, there is provided an image signal processing method used for a color image display device having a plurality of light emitting materials having different afterglow times, and an image corresponding to at least a light emitting material having a short afterglow time. The current field image signal is divided into a plurality of signals, each of which is low-pass filtered with different characteristics, and then combined to create an expanded image signal. The previous field image signal before the current field image signal is the current field image signal. An image signal processing method characterized by adding a pseudo afterglow signal to a current field image signal by synthesizing a current field image signal and an expanded image signal for a region larger than the signal.

  According to a third aspect of the present invention, in the second aspect, the tap number T (T is an integer) at the time of low-pass filtering is determined for each pixel, and the current field image signal is characterized based on the tap number T. A low-pass filter using a plurality of low-pass filters having different values, and generating an expanded image signal by selecting the largest one of the outputs from the plurality of low-pass filters. .

  According to a fourth aspect of the present invention, in the third aspect, the motion region is detected based on the difference signal between the previous field image signal and the current field image signal, and the motion speed of the image pattern is calculated based on the motion region. The image signal processing method is characterized in that the number of taps is converted to T based on the motion speed.

  The invention according to claim 5 of the present invention is the image signal processing method according to claim 3, wherein the number of taps T is a power of 0 or 2.

  According to a sixth aspect of the present invention, in the fourth aspect, the difference signal between the previous field image signal and the current field image signal is binarized based on a threshold value determined by an afterglow characteristic of the luminescent material. The image signal processing method is characterized in that a motion region is obtained by

  According to a seventh aspect of the present invention, in the third aspect, the low-pass filter sets a compression constant n (n is a constant), and the T × n pixels adjacent to the right side of the target pixel and the target An image signal processing method characterized by calculating an average of a current field image signal corresponding to T × n pixels adjacent to the left side of a pixel multiplied by a predetermined value.

  The invention according to claim 8 of the present invention is the image signal processing method according to claim 7, wherein the compression constant n is set to be a power of 2 or 1 / power of 2. is there.

  According to a ninth aspect of the present invention, in the second aspect, by outputting either the expanded image signal or the current field image signal based on the result of comparing the expanded image signal and the current field image signal. An image signal processing method characterized by combining a current field image signal and an expanded image signal.

  The invention according to claim 10 of the present invention is an image signal processing apparatus for driving a color image display device having a plurality of light emitting materials having different afterglow times, and corresponds to a light emitting material having at least a short afterglow time. Pseudo afterglow adding means for adding a pseudo afterglow signal to the image signal to be processed, the pseudo afterglow adding means low-pass filters the current field image signal by a plurality of low-pass filters having different characteristics, and outputs the output An expanded image generating means for generating an expanded image signal including a pseudo afterglow signal by combining, and the current field image signal and the expanded image signal are combined for a region where the previous field image signal is larger than the current field image signal An image signal processing apparatus comprising image combining means for adding an afterglow signal to a current field image signal.

  According to an eleventh aspect of the present invention, in the tenth aspect, the expanded image creating means includes a tap number determining unit that determines the number of taps T (T is an integer) for low-pass filtering for each pixel, and a tap. Based on the number of taps T determined by the number determining unit, a plurality of low-pass filtering units having different characteristics for low-pass filtering the current field image signal and the largest output from the plurality of low-pass filtering units are selected. An image signal processing apparatus having a filtering selection unit.

  According to a twelfth aspect of the present invention, in the eleventh aspect, the tap number determining unit detects a motion region that is a portion having motion based on a difference signal between the previous field image signal and the current field image signal. An area detection unit; a motion speed calculation unit that calculates a motion speed of an image pattern based on the motion region; and a tap number conversion unit that converts the motion speed calculated by the motion speed calculation unit into a tap number T according to a predetermined rule. It is an image signal processing apparatus characterized by having.

  According to a thirteenth aspect of the present invention, in the twelfth aspect, the tap number converting unit converts the tap number T so that the tap number T is a power of 0 or 2. It is.

  According to a fourteenth aspect of the present invention, in the twelfth aspect, the motion region detection unit includes a one-field delay unit that delays the image signal by one field to create a previous field image signal, a previous field image signal, and a current field image signal. A difference image part for obtaining a difference signal from the field image signal, and a binarization based on a threshold value determined by the afterglow characteristics of the luminescent material, thereby converting a motion region in which the difference signal is equal to or greater than the threshold value. An image signal processing apparatus having a binarization unit for detection.

  The invention according to claim 15 of the present invention is that, in claim 11, the low-pass filtering unit sets a compression constant n (n is a constant), and multiplies the tap number T by the compression constant n, An image multiplying unit that multiplies the current field image signal by a predetermined value, and an image multiplying unit corresponding to T × n pixels adjacent to the right side of the target pixel and T × n pixels adjacent to the left side of the target pixel. An image signal processing apparatus having a filtering unit for calculating an average of output signals.

  A sixteenth aspect of the present invention is the image signal processing device according to the fifteenth aspect, wherein the compression constant n is set to a power of 2 or 1 / power of 2.

  According to a seventeenth aspect of the present invention, in the tenth aspect, the image synthesizing means compares the expanded image signal with the current field image signal, and the expanded image signal based on the output of the signal comparing unit. An image signal processing apparatus having a signal selection unit for selecting one of current field image signals.

  Hereinafter, an image signal processing method and an image signal processing device according to an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, similarly to the phosphor used in the PDP, the afterglow time of the green phosphor as the light emitting material is the longest, and the afterglow time of the red phosphor is long, and the blue phosphor It is assumed that only the afterglow time of the phosphor is extremely short.

  FIG. 1 is a diagram for explaining a method of adding pseudo afterglow in an image signal processing apparatus according to the present invention. As shown in FIG. 1A, for example, when a white window pattern moves to the right, afterglow occurs so that the left side of the window pattern has a yellow tail. Therefore, in order to make the afterglow color the same white as the original image, a pseudo afterglow signal is added to the blue image signal in this embodiment.

  Hereinafter, the basic concept of adding a pseudo afterglow signal will be described. In normal television broadcasting, it is generally known that the movement in the scanning line direction, that is, the horizontal direction is overwhelmingly larger than the movement in the vertical direction. Therefore, in this embodiment, in order to simplify the circuit, attention is paid only to the movement in the horizontal direction.

First, the tailing length of the pseudo afterglow to be added is calculated. Since the length of the tail depends on the motion speed of the image, the motion region is first detected. A portion that is bright in the previous field before the current field and dark in the current field is a region where afterglow occurs. However, the difference between the previous field of the luminance _{L f-1} and the current field luminance _{L f ΔL (= (L f} -1) -L f) is equal to or smaller than the threshold Lth determined by afterglow luminescent materials Since image quality degradation due to afterglow is small, pseudo afterglow need only be added to only the pixel region that satisfies (L _f-1 ) −L _f > Lth.

  Therefore, as shown in (b), (c), and (d) in FIG. 1, a difference signal between the previous field image signal and the current field image signal is obtained, and an area where the difference signal is equal to or greater than the threshold value Lth. Is a motion region. Then, the horizontal width of the motion region is detected, and this width is set as the motion speed.

  For example, when the white window moves to the right by 4 pixels in one field as shown in FIG. 2A, the region shown in FIG. 2B becomes the motion region. In this case, the horizontal width is 4 pixels. Accordingly, the motion speed in the motion region (b) in FIG. 2 is “4” over all pixels. If the shape of the motion region is as shown in FIG. 2D, the motion speed of each pixel in the motion region is as shown in FIG.

  The motion speed obtained in this way may be used as the length of the tail of the pseudo afterglow. However, when the motion speed is high, the afterglow extends over two or more fields. The length is different from the actual tail length of afterglow. Therefore, the motion speed is converted into a number (hereinafter referred to as “tap number”) T corresponding to the actual trailing length of afterglow. FIG. 3 is a diagram illustrating an example of conversion from the motion speed to the tap number T. This tap number T corresponds to the tailing length of the final pseudo afterglow. Here, if the number of taps T is set to be a power of “0” or “2”, division can be performed only by bit shift, so that an arithmetic circuit described later can be simplified. In this way, the motion speed of the image pattern calculated based on the motion region is converted into the number of taps T so as to match the afterglow characteristics of the phosphor.

  Next, a pseudo afterglow signal is created. In the embodiment of the present invention, the current field image signal shown in FIG. 1C is multiplied by a predetermined magnification, and then low-pass filtering is performed by three low-pass filters LPF1, LPF2, and LPF3 having different characteristics. Then, by combining them, an expanded image signal which is an image signal including a pseudo afterglow signal is created. (E), (f), and (g) in FIG. 1 show outputs of the low-pass filters LPF1, LPF2, and LPF3, respectively. Then, by selecting the largest one of these outputs, an expanded image signal shown in (h) in FIG. 1 is created.

  The low-pass filter in the present embodiment performs low-pass filtering by obtaining an average value of image signals for a predetermined number of pixels adjacent to the right and left sides of the target pixel. At this time, in order to give a difference to the characteristics of each low-pass filter, the number of pixels to be averaged on the right side and the left side of the target pixel is set to a predetermined constant (hereinafter referred to as “compression constant”) for the tap number T obtained above. Called T) multiplied by n. FIG. 4 is a diagram for explaining the operation of the low-pass filter. When T × n = 4, for example, when the number of taps T of the target pixel is “4” and the compression constant n is “1”, the left and right four pixels of the target pixel indicated by diagonal lines in FIG. An average of the image signals corresponding to 8 pixels is output as an image signal corresponding to the target pixel. When T × n = 4, for example, the number of taps T corresponding to the target pixel is “2” and the compression constant n is “1”. In this case, the average of the image signals corresponding to the four pixels in total, that is, the left and right two pixels of the target pixel indicated by hatching in FIG. 4B is output as the image signal corresponding to the target pixel. Further, as shown in FIG. 4C, when the number of taps T corresponding to the target pixel is “0”, the image signal corresponding to the target pixel is output as it is.

  Thus, the low-pass filter sets the compression constant n (n is a constant), and T × n pixels adjacent to the right side of the target pixel and T × n pixels adjacent to the left side of the target pixel The average of the current field image corresponding to is multiplied by a predetermined value is calculated. According to such a low-pass filter, no special weighting is applied to each pixel, so that a multiplier or the like is unnecessary. Further, if the number of pixels to be averaged is set to a power of “2”, division is performed. Since it can be performed only by bit shift, the arithmetic circuit can be configured easily.

  FIG. 5 is a diagram for explaining an example of a low-pass filter having different characteristics. The low-pass filter LPF1 has a compression constant n of “1” and inputs an image signal obtained by multiplying the image signal of the current field by 0.5 as the image signal. Here, for example, assuming that the current field image signal is the signal shown in FIG. 5A and the number of taps T at that time is the value shown in FIG. 5B, first, the current field image signal. Is multiplied by 0.5, and the average value of the image signals corresponding to a total of 8 pixels is output as the image signal of the pixel of interest for each of the left and right 4 pixels of the pixel having the tap number “4”. (C) in FIG. 5 shows the image signal thus obtained.

  The low-pass filter LPF2 has a compression constant of “0.5”, and the image signal of the current field is input as it is as the image signal. Then, an average value of the image signals corresponding to a total of four pixels is output as an image signal of the pixel of interest for each of the two pixels on the left and right of the pixel having the tap number “4”. (D) in FIG. 5 shows the image signal thus obtained. The low-pass filter LPF3 has a compression constant of “0.25”, and inputs a signal obtained by multiplying the image signal of the current field by 2 as the image signal. Then, the average value of the image signals corresponding to a total of two pixels is output as the image signal of the pixel of interest for each of the left and right pixels of the pixel having the tap number “4”. (E) in FIG. 5 shows the image signal thus obtained.

  And the expansion | extension image shown to (f) in FIG. 5 can be obtained by selecting the largest thing among the outputs of each low-pass filter LPF1-LPF3.

  In this way, the expanded image signal determines the number of taps T (T is an integer) for low-pass filtering for each pixel, and based on the number of taps T, the current field image signal is processed by a plurality of low-pass filters having different characteristics. A low pass filter is created by selecting the largest of the outputs from the plurality of low pass filters.

  Here, by setting the compression constant n to a power of 2 or 1 / power of 2, the division in the average calculation can be performed only by bit shift, so that the arithmetic circuit can be simplified. Further, since each of the low-pass filters LPF1 to LPF3 performs only a simple moving average calculation, the expanded portion of the output image changes linearly as in (c), (d), and (e) in FIG. Just do it. However, by combining the outputs of a plurality of low-pass filters with different characteristics, an exponential function can be obtained as shown in (f) in FIG. 5 without using a low-pass filter having a complex coefficient matrix or a cyclic low-pass filter. A pseudo afterglow that changes in brightness can be created. This makes it possible to create pseudo afterglow that is close to natural afterglow with a simple circuit. According to this method, the exponential function is approximated by a polygonal line, but it is hardly recognized that it is a polygonal line on the image display. In addition, when a low-pass filter having a complex coefficient matrix is used as a low-pass filter, if the coefficient matrix is made variable, the circuit scale is further increased. However, the low-pass filter in the present embodiment is relatively Since it can be simply configured, the number of taps can be changed for each pixel in accordance with the movement speed. Accordingly, it is possible to create an extended image including pseudo afterglow that is close to natural afterglow, in which the pseudo afterglow has a long tail in a fast moving part and a short tail in a part that moves slowly.

  In this embodiment, the low-pass filter LPF1 inputs an image signal obtained by multiplying the current field image signal by 0.5 with a compression constant of 1, and the low-pass filter LPF2 sets the compression constant to 0.5. The image signal obtained by multiplying the field image signal by 1 is input, and the low-pass filter LPF3 is described as inputting the image signal obtained by doubling the current field image signal by setting the compression constant to 0.25. It is not limited, and it is desirable to set according to the afterglow characteristic of the phosphor. For example, the low-pass filter LPF1 inputs an image signal obtained by multiplying the current field image signal by 0.25 with the compression constant set to 1, and the low-pass filter LPF2 inputs 0.5 times the current field image signal with the compression constant set to 0.5. In some cases, it is better to input the image signal obtained by inputting the image signal, and the low-pass filter LPF3 may input an image signal obtained by multiplying the current field image signal by 1 with a compression constant of 0.25. In this embodiment, the case where three low-pass filters are used has been described as an example. However, the present invention is not limited to this, and if there are two or more low-pass filters, a natural simulation is possible. An expanded image signal including an afterglow signal can be created.

  Next, the pseudo afterglow signal is added to the previous field image signal. In this embodiment, in a region where the current field image is darker than the previous field image, if the expanded image signal is larger than the current field image signal, the current field image signal is replaced with the expanded image signal so that a pseudo residual signal is obtained. An image signal to which light is added is obtained. FIG. 1 (i) shows an image signal to which a pseudo afterglow signal is added. Thus, based on the result of comparing the expanded image signal and the current field image signal, the current field image signal and the expanded image signal are synthesized by outputting either the expanded image signal or the current field image signal, An image signal to which pseudo afterglow is added is created.

  As described above, in the image signal processing method according to the embodiment of the present invention, a pseudo afterglow signal whose luminance changes in a polygonal line shape is obtained from the current field image signal for an image signal corresponding to a light emitting material having a short afterglow time. A pseudo afterglow signal is added to the current field image signal. Also, for an image signal corresponding to a light emitting material having a short afterglow time, an extended image signal including pseudo afterglow by branching the current field image signal into a plurality of signals, low-pass filtering each with different characteristics, and then combining them. And a pseudo afterglow signal is added to the current field image signal by synthesizing the current field image signal and the expanded image signal for a region where the previous field image signal is larger than the current field image signal.

  FIG. 6 is a functional block diagram of the image signal processing apparatus 1 in the present embodiment. The image signal processing apparatus 1 includes a pseudo afterglow adding unit 2 for adding a pseudo afterglow signal, and delay units 4G and 4R that are delayed by a time equal to the processing time in the pseudo afterglow adding unit 2. A blue image signal 3B corresponding to a blue phosphor which is a light emitting material having a short time is input to the pseudo afterglow adding means 2. On the other hand, the green image signal 3G and the red image signal 3R are input to the delay means 4G and 4R, respectively.

  FIG. 7 is a functional block diagram showing the configuration of the pseudo afterglow adding means 2. The pseudo afterglow adding unit 2 switches between the expanded image generating unit 5 that generates the expanded image signal 6 including the pseudo afterglow signal from the input image signal 3, and the synthesized image by switching the image signal 3 and the expanded image signal 6. An image composition means 7 for adding a pseudo afterglow signal to the signal 3 is provided. FIG. 8 is a functional block diagram showing details of the decompressed image creating means 5. The expanded image creating means 5 is based on the tap number determining unit 11 that determines the tap number T (T is an integer) for low-pass filtering for each pixel, and the tap number T determined by the tap number determining unit 11. The plurality of low-pass filtering units 12 and 13 (corresponding to the above-mentioned low-pass filters LPF1 to LPF3) having different characteristics for filtering the field image signal and the largest output from the plurality of low-pass filtering units The filter selection part 14 to select is provided.

  The tap number determination unit 11 includes a motion region detection unit 8 that detects a motion region based on a difference signal between the previous field image signal and the current field image signal, and a motion speed calculation unit that calculates a motion speed of the image pattern based on the motion region. 9 and a tap number conversion unit 10 that converts the movement speed calculated by the movement speed calculation unit 9 into the tap number T according to a predetermined rule. Then, the horizontal speed of the motion region is measured by the motion speed calculation unit 9 to determine the motion speed at each pixel as shown in (c) of FIG. The obtained movement speed is converted into the number of taps in the tap number conversion unit 10 as shown in FIG. Here, the tap number conversion unit 10 performs conversion so that the tap number T is a power of “0” or “2”.

  The motion region detection unit 8 delays the current field image signal 3 by one field to create a previous field image signal, and the previous field image signal and current field image signal delayed by the one field delay unit 81. The difference image unit 82 for obtaining a difference signal with respect to 3 and a motion region in which the difference signal becomes equal to or greater than the threshold Lth by binarizing the difference signal based on the threshold Lth determined by the afterglow characteristics of the luminescent material. And a binarization unit 83 for detecting. In the present embodiment, Lth = 100 is set for an image signal of 256 gradations, but this value is experimentally matched to conditions such as afterglow characteristics and drive timing of a phosphor used in the image display device. It is what I have sought.

  The low-pass filtering units 12 and 13 set a compression constant n (n is a constant), a tap number multiplication unit that multiplies the tap number T by the compression constant n, and an image multiplication unit that multiplies the current field image signal by a predetermined value. A filtering unit that calculates an average value of output signals from the image multiplying unit corresponding to T × n pixels adjacent to the right side of the target pixel and T × n pixels adjacent to the left side of the target pixel. Yes. The low-pass filtering units 12 and 13 apply a plurality of low-pass filters having different characteristics to the current field image signal in parallel. Here, the compression constant n is set to a power of 2 or 1 / power of 2.

  The filtering selection unit 14 compares the outputs from the plurality of low-pass filtering units 12 and 13 in units of pixels, selects the largest one, and outputs it as the expanded image signal 6.

  FIG. 9 is a functional block diagram showing details of the image composition means 7. The image synthesizing means 7 compares the expanded image signal 6 with the current field image signal 3 based on the output of the signal comparison unit 15 that compares the expanded image signal 6 with the current field image signal 3. And a signal selection unit 16 for selection. Then, the signal comparison unit 15 compares the expanded image signal 6 and the image signal 3, and the larger signal is selected by the signal selection unit 16. Further, the signal comparison unit 18 compares the image signal 3 with the image signal of the previous field obtained by delaying the image signal 3 by the one-field delay unit 17, and if the image signal of the previous field is large, the output of the signal selection unit 16 is In this case, the image signal 3 is selected by the signal selection unit 19 and output. By sharing the 1-field delay unit 17 and the 1-field delay unit 81, the circuit configuration can be simplified.

  As described above, an image with pseudo afterglow added by the pseudo afterglow adding means 2 can be obtained. In practice, a digital signal processing integrated circuit (LSI) may be used as a circuit configuration example for realizing these functional blocks.

  FIG. 10 is an example of a circuit block diagram of a PDP driving device using the image signal processing device of the present embodiment. The AD converter 20 performs analog-digital conversion (AD conversion) on each of the green, red, and blue image signals 21. The digital data processing unit 221 inside the LSI 22 uses the internal memory 222 and the external memory 23 to perform a delay process for the green and red image signals and a process for adding pseudo afterglow to the blue image signal. After that, necessary data processing is performed and output to the PDP driver 24. The PDP driver 24 drives the PDP 25 to display an image.

  As described above, the image signal processing apparatus according to the embodiment of the present invention adds a pseudo afterglow signal for adding a pseudo afterglow signal to a blue image signal corresponding to a blue phosphor having a short afterglow time. And a pseudo afterglow adding means for generating a decompressed image signal including a pseudo afterglow signal by low-pass filtering the current field image signal with a plurality of low-pass filters having different characteristics and combining the outputs. Image generating means, and image synthesizing means for synthesizing the current field image signal and the expanded image signal for an area where the previous field image signal is larger than the current field image signal and adding a pseudo afterglow signal to the current field image signal. Image signal processing apparatus. Then, by adding pseudo afterglow that decreases in a polygonal line to the blue image signal, the afterglow of each of the green, red, and blue images is visually equal, and as a result, the color of the afterglow is Since it becomes the same as the original image, it is possible to eliminate a sense of incongruity.

  In addition, when one field is divided into a plurality of sub-fields with different weights and displayed, such as PDP, a phenomenon in which a gradation different from the original is observed in the moving image portion due to the integral action of the eyes, so-called moving image A false contour may occur. In order to prevent this, a driving method that does not generate a moving image pseudo contour or ignores it even if it occurs, such as using only a gradation that does not generate a moving image pseudo contour for a region where pseudo afterglow is added. It is desirable to use together.

  In the present invention, even in an image display apparatus using a color image display device having a plurality of light emitting materials having different afterglow times, the afterglow color can be made the same as that of the original image. This is useful for improving the display quality of a driving apparatus using a color image display device having a light emitting material.

The figure for demonstrating the method of pseudo afterglow addition in embodiment of this invention The figure for demonstrating the relationship between the motion area | region and motion speed in embodiment of this invention. The figure for demonstrating the conversion from the moving speed to the number of taps in embodiment of this invention The figure for demonstrating operation | movement of the low-pass filter in embodiment of this invention The figure for demonstrating the example of the low-pass filter from which the characteristic in embodiment of this invention differs Functional block diagram of an image signal processing apparatus in an embodiment of the present invention Functional block diagram of pseudo afterglow adding means of the image signal processing apparatus Functional block diagram of decompressed image creating means of the image signal processing apparatus Functional block diagram of image composition means of the image signal processing apparatus The block diagram which shows an example of the circuit of the image signal processing apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image signal processing apparatus 2 Pseudo afterglow addition means 3, 3G, 3R, 3B Image signal 4G, 4R Delay means 5 Expanded image creation means 6 Expanded image signal 7 Image composition means 8 Motion area detection part 9 Motion speed calculation part 10 Tap Number conversion unit 11 Tap number determination unit 12, 13 Low-pass filtering unit 14 Filter selection unit 81 1 field delay unit 82 Difference image unit 83 Binarization unit

Claims (17)

An image signal processing method for use in a color image display device having a plurality of light emitting materials having different afterglow times, wherein the pseudo brightness changes linearly with respect to an image signal corresponding to a light emitting material having a short afterglow time. An afterglow signal is created from a current field image signal, and the pseudo afterglow signal is added to the current field image signal. An image signal processing method used for a color image display device having a plurality of light emitting materials having different afterglow times, and at least branches the current field image signal to an image signal corresponding to a light emitting material having a short afterglow time. Then, after low-pass filtering each with different characteristics, a decompressed image signal is created by synthesis, and for the region where the previous field image signal before the current field image signal is larger than the current field image signal, the current field An image signal processing method comprising: adding a pseudo afterglow signal to the current field image signal by combining an image signal and the expanded image signal. For the decompressed image signal, the number of taps T (T is an integer) for low-pass filtering is determined for each pixel, and the current field image signal is reduced by a plurality of low-pass filters having different characteristics based on the number of taps T. 3. The image signal processing method according to claim 2, wherein the image signal processing method is performed by filtering and selecting the largest output from the plurality of low-pass filters. The number of taps T is a motion region detected based on a difference signal between the previous field image signal and the current field image signal, a motion speed of an image pattern is calculated based on the motion region, and the tap number T is calculated based on the motion speed. 4. The image signal processing method according to claim 3, wherein the determination is performed by conversion. 4. The image signal processing method according to claim 3, wherein the tap number T is a power of 0 or 2. 5. The image according to claim 4, wherein the motion region is obtained by binarizing a difference signal between the previous field image signal and the current field image signal based on a threshold value determined by an afterglow characteristic of the luminescent material. Signal processing method. The low-pass filter sets a compression constant n (n is a constant), and corresponds to T × n pixels adjacent to the right side of the target pixel and T × n pixels adjacent to the left side of the target pixel. 4. The image signal processing method according to claim 3, wherein an average of the field image signal multiplied by a predetermined value is calculated. 8. The image signal processing method according to claim 7, wherein the compression constant n is set to be a power of 2 or 1 / power of 2. The current field image signal and the expanded image signal are synthesized by outputting either the expanded image signal or the current field image signal based on the result of comparing the expanded image signal and the current field image signal. The image signal processing method according to claim 2. An image signal processing apparatus for driving a color image display device having a plurality of light emitting materials having different afterglow times, for adding a pseudo afterglow signal to an image signal corresponding to a light emitting material having a short afterglow time The pseudo afterglow adding means includes the pseudo afterglow signal by low-pass filtering the current field image signal by a plurality of low-pass filters having different characteristics and combining the outputs. A decompressed image creating means for creating a decompressed image signal; and combining the current field image signal and the decompressed image signal with respect to a region where the previous field image signal is larger than the current field image signal, An image signal processing apparatus comprising: an image composition unit for adding to a field image signal. The expanded image creating means includes a tap number determining unit that determines a tap number T (T is an integer) for low-pass filtering for each pixel, and a current field based on the tap number T determined by the tap number determining unit. 11. A plurality of low-pass filtering units having different characteristics for low-pass filtering image signals, and a filtering selecting unit for selecting the largest output from the plurality of low-pass filtering units. The image signal processing apparatus described. The number-of-tap determination unit calculates a motion area of a motion region that is a portion having motion based on a difference signal between the previous field image signal and the current field image signal, and calculates a motion speed of the image pattern based on the motion region. The image signal processing according to claim 11, further comprising: a motion speed calculating unit that converts the motion speed calculated by the motion speed calculating unit into a tap number T according to a predetermined rule. apparatus. 13. The image signal processing apparatus according to claim 12, wherein the tap number conversion unit performs conversion so that the tap number T is a power of 0 or 2. The motion region detection unit includes a one-field delay unit that delays the image signal by one field to create a previous field image signal, a difference image unit that obtains a difference signal between the previous field image signal and the current field image signal, and the difference And a binarization unit that detects a motion region in which the difference signal is equal to or greater than the threshold value by binarizing the signal based on a threshold value determined by the afterglow characteristics of the light emitting material. The image signal processing apparatus according to claim 12. The low-pass filtering unit sets a compression constant n (n is a constant), a tap number multiplication unit that multiplies the tap number T by the compression constant n, an image multiplication unit that multiplies a current field image signal by a predetermined value, And a filtering unit that calculates an average of output signals from the image multiplication unit corresponding to T × n pixels adjacent to the right side of the pixel and T × n pixels adjacent to the left side of the target pixel. The image signal processing apparatus according to claim 11. 16. The image signal processing apparatus according to claim 15, wherein the compression constant n is set to a power of 2 or 1 / power of 2. The image synthesis means includes a signal comparison unit that compares the expanded image signal with the current field image signal, and a signal selection unit that selects either the expanded image signal or the current field image signal based on the output of the signal comparison unit. The image signal processing apparatus according to claim 10, further comprising:

Images