JPH08317345A - Method and device for displaying video - Google Patents

Abstract

PURPOSE: To consist high resolution with high picture quality when displaying video signals in an interlace system on a successive scanning type display device. CONSTITUTION: A level difference detector 21 detects a contour from level difference between a video signal B, with which an inputted video signal A is read out at double speed, and a video signal G in the preceding line from a line memory 20. A level comparator 22 judges whether the contour is detected or not by performing comparison with a video contour compare level M. When the contour is detected or any motion is detected by a level difference detector 14 and a level comparator 15, while using a line memory 16, the line to continuously twice output the video signal B is interpolated. In the other case, field interpolation is performed by video signals C and B through the line memory 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video display method and device for displaying an interlaced video signal on a progressive scanning display device.

[0002]

2. Description of the Related Art The NTSC (National Television System Committee), which has been widely used for television broadcasting, has been used.
The interlace system is premised on the transmission of video signals such as e) system. In the interlaced method, a video signal for one frame is divided into two fields, an odd field and an even field, and is transmitted. Therefore, the frequency band required for transmission can be narrowed. In the odd-numbered field, the odd-numbered scanning lines among the plurality of horizontal scanning lines forming the image for one frame are sequentially transmitted while skipping the even-numbered scanning lines. In the even field, the even-numbered scanning lines for one frame are sequentially transmitted while skipping the odd-numbered scanning lines. A cathode ray tube widely used as a current television receiver (hereinafter referred to as "CRT" from Cathode Ray Tube).
The display device displays an image signal by an interlace system.

On the other hand, a liquid crystal display device (hereinafter abbreviated as “LCD”), which is expected to be widely used in the future because of easy space saving and power saving, is
It is premised on display by a progressive scanning method also called a non-interlaced method. In an LCD, a plurality of pixels formed in advance can provide a flicker-free screen as compared with a CRT. In the progressive scanning method, odd-numbered and even-numbered scanning lines of one frame are alternately displayed one by one. Therefore, it is necessary to convert the transmitted interlaced video signal into a progressive scan video signal.

FIG. 7 shows a video display state by interlaced scanning of an interlace type CRT display device. The scanning lines o1, o2, ... Shown by solid lines are displayed during the period in which the video signal of the odd field is transmitted. The scanning lines e1, e2, e3, ... Shown by alternate long and short dash lines are displayed during the period in which the video signal of the even field is transmitted. Therefore, during one field period, the video signal is input only to half of the scanning lines in the effective display screen of the display. In the progressive scanning display as shown in FIG. 8, the scanning lines for one frame are displayed in the same period for both odd and even numbers. Therefore, in order to effectively display the interlaced video signal on the progressive scanning type display, during transmission of the video signal of one field,
It is necessary to interpolate the video signal of the other field by performing some signal processing.

9 and 10 show an interpolation method for displaying an interlaced video signal on a progressive scanning display device. The interpolation shown in FIG. 9C is performed using the even field of the previous frame shown in FIG. 9A and the odd field of the current frame shown in FIG. 9B. Alternatively, the interpolation shown in FIG. 10C is performed using the odd field of the current frame shown in FIG. 10A and the even field of the current frame shown in FIG. 10B.

In this specification, each scanning line is represented as follows. The odd field is represented by "o" and the even field is represented by "e". A number indicating the input order of the field is added before this, and the input order in the field is shown after the number. For example, "2o3"
In the case of, the third scan line of the second odd field is represented.

2o3 and 1e4, 2o5-1 of FIG. 9 (c)
e7 period, and 2e3 and 2o3, 2 in FIG.
In the period of e5 to 2o6, field interpolation is performed using the scanning line transmitted one field before the field to be displayed. During the periods 2o4 in FIG. 9C and 2e4 in FIG. 10C, line interpolation is performed by using adjacent scan lines in the field to be displayed. Field interpolation has the advantage of increasing the resolution in the vertical direction, and has the disadvantage of distorting the displayed image when displaying a moving image because it simultaneously displays the image signals of the two fields with input time differences.

FIG. 11 shows a state in which the character "H" moving in the scanning line direction at a speed of 1 pixel / field is displayed by field interpolation. Since the video signals are alternately switched for each field transmitted by the odd-numbered scan lines and the even-numbered scan lines, the display image is distorted. On the other hand, the line interpolation has the advantage that it is suitable for moving image reproduction and the resolution is inferior to the field interpolation because the displayed video signals are all switched for each field.

FIG. 12 shows a state in which a stationary triangle is displayed. The solid line shows the line interpolation, and the broken line shows the field interpolation. It can be seen that the resolution of diagonal lines is inferior to field interpolation in line interpolation. Therefore, field interpolation is suitable for displaying a still image, and line interpolation is suitable for displaying a moving image. A prior art in which the movement of the video signal is detected for each pixel at the time of displaying the video by utilizing such a characteristic and the above-mentioned two methods are switched according to the detection result is disclosed in, for example, JP-A-63-156487. ing.

FIG. 13 shows an example of the structure required to realize the display method according to the prior art. 14 and 15 show signals of the respective parts of FIG. The input video signal a has an even field period in FIG. 14 and an odd field period in FIG. Further, "1H" indicates a period of one line which is one horizontal synchronizing period of the video signal a, and "1h" indicates one horizontal synchronizing period of the output video signal q. The output video signal q is equal to the input video signal a 2
It has double the transmission speed. 9 and 10 described above respectively show the line arrangement of each scanning line when displaying the video signal a of FIGS. 14 and 15 on the display.

In FIG. 13, three field memories 1, 2, and 3 can store a video signal for one field, and can read the stored data at a speed twice the transmission speed of the video signal a. Is. The level difference detector 4 outputs the output signal b of the field memory 1 and the field memory 3
The level difference e from the output signal d from is detected. The level comparator 5 compares the level difference e with the motion detection level n and outputs the motion detection signal f. Line memory 6
Can store a video signal for one line. The switching signal generation circuit 7 generates the switching signal p from the horizontal synchronizing signal o of the display device to be displayed. Changeover switch 8,
9 is switched by the output signals f and p from the level comparator 5 and the switching signal generation circuit 7, respectively.

At the same time as the video signal a is written to the field memory 1, the video signal b stored one field before is read out at a speed twice as high as that at the time of writing. This reading is performed in the first 1h period of the 1H period of the video signal a. The writing and reading timings of the field memories 2 and 3 are also the same as the field memory 1
The writing and reading timings of are also adjusted to the field memory 1. The video signals c and d read from the field memories 2 and 3 are video signals one field before the video signals b and c, respectively. Therefore, the video signal d
Is a video signal of two fields of the video signal b, that is, one frame before. The level difference detector 4 uses the video signal b,
The level difference for one frame period between d is detected, and the detected level difference is given to the level comparator 5 as the movement amount e between frames. The level comparator 5 compares the motion amount e with the motion detection comparison level n, and if e> n, the Low level, e
If ≦ n, the High level output is used as the motion detection signal f
Is given to the changeover switch 8.

The change-over switch 8 selects the video signal b when the motion detection signal f is at the Low level indicating "motion detected", and the motion detection signal f indicates Hi indicating "no motion detected".
The video signal c is selected at the gh level. The video signal k selected by the changeover switch 8 is stored in the line memory 6
Stored in. The line memory 6 outputs the video signal 1 to the changeover switch 9 in the latter half 1h of the horizontal synchronizing period 1H of the video signal a. The change-over switch 9 selects the video signal b in the first 1h period of the horizontal synchronizing period 1H and the video signal 1 in the latter half 1h of the horizontal synchronizing period 1H based on the changeover signal p from the changeover signal generating circuit 7, It is output as q to the progressive scanning display device in the subsequent stage. At this time, if the source of the video signal 1 is the video signal b, it corresponds to the line interpolation, and if it is the video signal c, it corresponds to the field interpolation. Although the case of motion detection and the case of non-detection have been described above, motion detection is performed in pixel units. In the case of the normal video signal a, the video signal k selected by the changeover switch 8 is frequently switched even within the same field and scanning line, and the output video signal q in the subsequent stage also changes accordingly.

[0014]

According to the prior art described above, "presence / absence of motion" is detected for each pixel, and field interpolation or line interpolation is switched according to the detection result to obtain a high resolution still image. , It is possible to display each video without distortion. However, the interpolation by the motion detection method as in the prior art causes distortion of the displayed image when the image to be displayed moves in the scanning line direction. 16
The display state when interpolation is performed in pixel units when a window of 3 × 3 pixels horizontally moves to the right in the figure at a speed of 1 [pixel / field] on the screen of the display is shown. “□” indicates one of the display pixels, “T” indicates a pixel in which motion is detected, “t” indicates a pixel immediately above that which is line-interpolated by the motion detection pixel T, and “*”.
Indicates the distortion of the display window.

In the first field shown in FIG. 16A,
Since the window is stationary and there are no pixels for which motion is detected, the display on the display is all field interpolation. In the second field shown in FIG. 16B,
Since the window horizontally moves one pixel to the right from the first field, the motion is detected at the pixel indicated by T, and the pixel t therebelow is interpolated by the video signal of the pixel indicated by T. As a result, the pixel indicated by * is distorted. Similarly, in the third field shown in FIG. 16C, the pixels indicated by * in the upper left and upper right also have distortion. As described above, only the pixel interpolation based on the motion detection of the prior art causes distortion inevitably with respect to the motion of the display image in the scanning line direction.

An object of the present invention is to provide a video display method and device capable of displaying a video on a progressive scanning display device with high resolution and high image quality without distorting the displayed video.

[0017]

According to the present invention, an image for one frame to be displayed by a plurality of scanning lines is an odd field signal representing an image displayed by each pixel on an odd-numbered scanning line and an even field signal. From an interlaced video signal that is transmitted by being divided into even field signals that represent the video displayed by each pixel on the th scan line, odd scan lines and even scan lines are alternately displayed on the same screen. In an image display method of forming an image for one frame while displaying, a first level difference, which is a difference in display level between pixels displayed adjacently, is changed to a first level difference by an odd or even field signal being transmitted. The difference between the display level of a pixel displayed by the odd or even field signal being transmitted and the display level of the pixel one frame before, as compared with the threshold value of 1. A second level difference is compared to a second threshold and the first level difference is greater than the first threshold or the second level difference is greater than the second threshold. Is also large, the scan lines in the odd or even field signal are continuously displayed twice while each scan line of the video signal is transmitted, and the first level difference is equal to the first threshold value. Below, and when the second level difference is less than or equal to the second threshold value, while each scan line of the video signal is transmitted,
A video display method is characterized in that scanning lines in an odd field signal and scanning lines in an even field signal are alternately displayed. Further, in the invention, it is characterized in that at least one of the first and second threshold values can be freely set. Further, in the present invention, the first level difference is calculated by comparing display levels between pixels on scanning lines displayed above and below with an odd or even field signal being transmitted. Further, according to the present invention, an image of one frame to be displayed by a plurality of scanning lines is composed of an odd field signal representing an image displayed by each pixel on an odd scanning line and each pixel on an even scanning line. From an interlaced video signal that is transmitted by being divided into an even field signal that represents a video to be displayed, while displaying odd-numbered scanning lines and even-numbered scanning lines alternately on the same screen, In a video display device for forming a video, a first field memory that can store a video signal being transmitted for one field and can be read at twice the transmission speed, and a video signal read from the first field memory are provided. A second field memory that can store one field and can be read at twice the transmission speed, and one video signal read from the second field memory Field can be stored, and the video signal read from the first field memory and the third field memory, which can be read at twice the transmission speed, can be stored for one scanning line, and the video signal can be stored at twice the transmission speed. A readable first line memory, and a second line memory capable of storing a video signal read from the first field memory or the second field memory for one scanning line, and readable at a speed twice the transmission speed, In response to the output from the first level difference detection means for comparing the video signals read from the first field memory and the first line memory for each pixel, the display level of the display level between adjacent pixels A first level comparing means for comparing a first level difference, which is a difference, with a first threshold value, and a video signal read from the first field memory and the third field memory as pixels. In response to the output from the second level difference detecting means and the second level difference which is the difference in display level of each pixel and is compared with the second threshold value. Switching means for switching and deriving a video signal to be displayed in response to outputs from the two-level comparing means and the first and second level comparing means, wherein the first level difference is greater than the first threshold value. If it is larger or the second level difference is larger than the second threshold value, the image of one scanning line read from the first field memory while each scanning line of the video signal is transmitted. The signal is stored in the second line memory while being displayed, and then the video signal for one scanning line read from the second line memory is switched to be displayed, and the first level difference is equal to the first threshold value. Below, and the second level difference is the second
Is less than or equal to the threshold value, the video signal for one scan line read from the first field memory is displayed while each scan line of the video signal is transmitted, and the video signal is read from the second field memory. A switching means for storing the video signal for one scanning line in the second line memory and for switching to display the video signal for one scanning line read from the second line memory. It is a characteristic video display device. Further, the present invention is characterized by comprising liquid crystal display means for displaying an image of the video signal derived from the switching means.

[0018]

According to the present invention, an image for one frame to be displayed by a plurality of scanning lines is an odd field signal representing an image displayed by each pixel on an odd-numbered scanning line,
From an interlaced video signal that is transmitted by being divided into an even field signal that represents an image displayed by each pixel on an even scan line, an odd scan line and an even scan line alternate on the same screen. An image for one frame is formed while being displayed. A contour whose display level is changed by comparing a first level difference, which is a difference in display level between pixels displayed adjacently, with a first threshold value by an odd or even field signal being transmitted. Can be detected. Comparing a second level difference, which is the difference between the display level of the pixel displayed by the odd or even field signal being transmitted and the display level of the pixel one frame before, with a second threshold value. The motion can be detected by.

When the first level difference is greater than the first threshold value or the second level difference is greater than the second threshold value, a contour or motion is detected and the video signal is detected. While each scanning line is transmitted, the scanning line in the odd or even field signal is displayed twice in succession to perform high-quality line interpolation. When the first level difference is less than or equal to the first threshold value and the second level difference is less than or equal to the second threshold value, contours and motion are not detected, so that each scan line of the video signal is transmitted. In the meantime, the field interpolation in which the scanning lines in the odd field signal and the scanning lines in the even field signal are alternately displayed can be performed to achieve high resolution display.

Further, according to the present invention, since at least one of the first and second threshold values can be freely set, the frequency at which the interpolation method is switched can be adjusted according to the displayed image.

According to the invention, the first level difference is
Since the display levels between the pixels on the scanning lines displayed above and below are compared and calculated by the odd-numbered or even-numbered field signal being transmitted, the change in the contour in the scanning line direction can be reliably detected.

Further in accordance with the present invention, the video display device comprises:
An image for one frame that should be displayed with multiple scanning lines
Interlaced video transmitted by being divided into an odd field signal representing an image displayed by each pixel on an odd scan line and an even field signal representing an image displayed by each pixel on an even scan line An image for one frame is formed while alternately displaying odd-numbered scan lines and even-numbered scan lines on the same screen from the signal. The first field memory can store the video signal being transmitted for one field, and can be read at a speed twice the transmission speed. The second and third field memories are the first
Also, the video signal read from the second field memory can be stored for one field, and can be read at a speed twice the transmission speed. The first and second line memories can store one scanning line of video signals read from the first field memory or the first field memory or the second field memory, respectively, and have a transmission rate of 2
It can be read at twice the speed.

The first level difference detecting means compares the video signals read from the first field memory and the first line memory for each pixel. The first level comparing means is responsive to the output from the first level difference detecting means, and compares the first level difference, which is the difference in display level between adjacent pixels, with a first threshold value, Detect changes in contours. Second
The level difference detecting means includes a first field memory and a third field memory.
Motion is detected by comparing pixel-by-pixel video signals read from the field memory. The second level comparison and output means compares the second level difference, which is the difference between the display levels of the pixels, with the second threshold value to reliably detect the motion.

The switching means responds to the outputs from the first and second level comparing means to switch and derive the video signal to be displayed. When the first level difference is larger than the first threshold value or the second level difference is larger than the second threshold value, it means that a change or movement of the contour is detected. While each scanning line of the video signal is being transmitted, the video signal for one scanning line read from the first field memory is displayed and stored in the second line memory, and then the second line memory is stored.
It is possible to realize a high-quality display of a moving image by switching to display a video signal for one scanning line read from the line memory and performing line interpolation. When the second level difference is less than or equal to the second threshold value, a video signal for one scanning line read from the first field memory while each scanning line of the video signal is transmitted as a still image display. While displaying, the video signal for one scanning line read from the second field memory is stored in the second line memory, and the video signal for one scanning line read next from the second line memory is displayed. It is possible to realize a high resolution by switching to and performing field interpolation.

Further, according to the present invention, since the liquid crystal display means for displaying the image signal of the image signal derived from the switching means is provided, a good image display without flicker can be realized with a space saving.
This can be achieved while achieving power saving.

[0026]

FIG. 1 shows the electrical construction of a display device according to an embodiment of the present invention. The field memories 11, 12, and 13, which are the first, second, and third field memories, can store a video signal for one field. Reading from the field memory 11 and writing to and reading from the field memories 12 and 13 are performed at a speed twice as fast as the speed at which the input video signal A is written into the field memory 11. The video signal A is transmitted from a television receiver, a VTR or the like. Level difference detector 14
Detects the level difference E between the output signal B of the field memory 11 and the output signal D of the field memory 13. With respect to the level difference E, the level comparator 15 compares the level difference E with the motion detection level N and outputs the motion detection signal F. The line memory 16 can store a video signal for one line. In the switching signal generation circuit 17,
The switching signal P is generated from the horizontal synchronizing signal O of the display device to be displayed. The changeover switch 18 is used for the video signals B and C.
Is switched to the line memory 16. The changeover switch 19 switches between the video signal B and the output signal L of the line memory 16 by the output signal P from the switching signal generation circuit 17, and outputs the video signal Q.

At the same time as the video signal A is written in the field memory 11, the video signal B stored one field before is read out at a speed twice as fast as that at the time of writing. This reading is performed during the 1h period which is the first half of the 1H period of the video signal A. Field memory 12, 1
The write and read timings of 3 are also adjusted to the field memory 11. Field memory 12, 13
The video signals C and D read from are the video signals one field before the video signals B and C, respectively. Therefore, the video signal D becomes a video signal one frame before the video signal B. The level difference detector 14 detects the level difference between the video signals B and D for one frame period, and supplies the detected level difference to the level comparator 15 as a motion amount E between frames.
The level comparator 15 compares the motion amount E with the motion detection comparison level N and derives a low level output as E> N and a high level output as E ≦ N as a motion detection signal F.

The line memory 2 which is the first line memory
0 indicates the video signal B read from the frame memory 11.
Is written, and the stored data is read as a video signal G at the same time. The level difference detector 21, which is the first level difference detecting means, detects the level difference between the video signal B and the video signal G. This level difference is given from the level difference detector 21 to the level comparator 22 as an image contour level difference H between the upper and lower scanning lines. The level comparator 22, which is the first level comparing means, compares the image contour level difference H with the image contour comparison level M which is the first threshold value. When H> M, the output signal I becomes Low level, and when H ≦ M, the output signal I becomes High level.

The output signal I of the level comparator 22 is applied to one input of the 2-input AND circuit 23. AND circuit 2
The motion detection signal F is given to the other input of 3. The AND circuit 23 derives a low-level output J when either the video contour detection or the video motion detection is performed, and derives a high level as the output J otherwise. The output J is given to the changeover switch 18 to switch the video signals B and C.

The change-over switch 18 selects the video signal B when the output J of the AND circuit 23 is at the low level indicating "detection", and when the output J is at the high level indicating "no detection". Select. Changeover switch 18
The video signal K selected by is stored in the line memory 16 which is the second line memory. Line memory 1
From 6 onwards, the first half 1h of the horizontal synchronization period 1H of the video signal A
The contents stored between the eaves are output to the changeover switch 19 as the video signal L in the latter half 1h period. Changeover switch 1
9 is a video signal B during the first 1h period of the horizontal synchronization period 1H based on the switching signal P from the switching signal generation circuit 17.
, The video signal L is selected in the latter half of 1h period,
The image signal Q is output to the progressive scanning display device in the subsequent stage. At this time, if the source of the video signal L is the video signal B, it corresponds to the line interpolation, and if it is the video signal C, it corresponds to the field interpolation.

The level difference detector 14 related to the motion detection is the second level difference detecting means, and the level comparator 15 is the second level difference detecting means.
The level comparison means and the motion detection comparison level correspond to the second threshold value. The switching signal generation circuit 17, the switching switches 18 and 19 and the AND circuit 23 correspond to switching means. Although the video contour comparison level M and the motion detection comparison level N are described as preset constants, at least one of them may be adjustable. It is possible to obtain a higher image quality and a higher resolution by adjusting the level as the threshold value while watching the displayed image and reducing the frequency of switching the interpolation method according to the type and the property.

2 and 3 show signals of the respective parts in the configuration of FIG. 2 shows the case where the input video signal A is in the even field period, and FIG. 3 shows the case where the video signal A is in the odd field period. 4 and 5 are similar to FIGS.
In the case of, the arrangement of the scanning lines displayed on the progressive scanning display is shown.

FIG. 6 shows a display state when a window of 3 × 3 pixels moves horizontally to the right at a speed of 1 [pixel / field] on the display. The meanings of “□”, “T”, and “t” are the same as in FIG. 16 described above. "R" is
The pixel in which the image contour is detected is shown. “R” indicates a pixel directly below the R pixel and subjected to line interpolation by the pixel. The first field shown in FIG. 6A is a state in which the window is stationary. At this time, although there are no motion detection pixels, the upper portion of the window is interpolated with the background pixels because of the video contour detection pixel, and the window itself. Has changed to 2 × 4. In the second and third fields shown in FIGS. 6B and 6C, respectively, the window size is changed to 4 × 4 and 2 × 4 by both the motion detection pixel and the video contour detection pixel. There is. However, the shape of each field does not change although the size of the window changes. Therefore, the display of the display device is not distorted, and a display that is visually unnatural is realized.

In the above-mentioned embodiment, although the image is displayed on the LCD, the CR of high resolution is used.
You can also use T to display in a non-interlaced format.

[0035]

As described above, according to the present invention, the progressive scanning display is performed while alternately displaying the odd-numbered scanning lines and the even-numbered scanning lines from the interlaced video signal on the same screen. Image for one frame is formed. A change in contour is detected by comparing a first level difference, which is a difference in display level between pixels displayed adjacently, with a first threshold value according to an odd or even field signal being transmitted. be able to. Comparing a second level difference, which is the difference between the display level of the pixel displayed by the odd or even field signal being transmitted and the display level of the pixel one frame before, with a second threshold value. The motion can be detected by.

When a contour or motion is detected, the scan line in the odd or even field signal is displayed twice in succession during the transmission of each scan line of the video signal, and the line interpolation is performed. To do. When the first level difference is less than or equal to the first threshold value and the second level difference is less than or equal to the second threshold value, no contour or motion is detected and each scanning line of the video signal is transmitted. In the meantime, the field interpolation for alternately displaying the scanning lines in the odd field signal and the scanning lines in the even field signal is performed. It is possible to reliably detect the change and movement of the contour and achieve high quality display.

Further, according to the present invention, since at least one of the first and second thresholds can be freely set, it is possible to adjust the frequency of switching the interpolation method according to the displayed image.

Further, according to the present invention, the first level difference is
Since the display level between the pixels on the scanning lines displayed above and below is compared and calculated by the odd or even field signal being transmitted, it is possible to reliably detect the change in the contour along the scanning line direction.

Further in accordance with the present invention, the video display device comprises:
An image for one frame is formed by alternately displaying odd-numbered scanning lines and even-numbered scanning lines on the same screen from an interlaced video signal. The first field memory can store the video signal being transmitted for one field, and can be read at a speed twice the transmission speed. The second and third field memories can store the video signals read from the first and second field memories for one field, respectively, and can be read at a speed twice the transmission speed. The first and second line memories are the first field memory or the first field memory or the second field memory.
1 for each video signal read from the field memory
It can store scanning line segments and read at twice the transmission rate.

A change in the contour can be detected by the first level difference detecting means and the first level comparing means.
The second level difference comparing means detects the motion by comparing the video signals read from the first field memory and the third field memory for each pixel. The second level comparison and output means compares the second level difference, which is the difference between the display levels of the pixels, with the second threshold value to reliably detect the motion. The switching means performs line interpolation to display a moving image with high image quality when a contour change or motion is detected, and field interpolation to display a still image at high resolution when not detected. You can

Further, according to the present invention, since the liquid crystal display means for displaying the image signal of the image signal derived from the switching means is provided, a good image display without flicker can be realized, and space saving can be achieved.
This can be achieved while achieving power saving.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a video display device according to an embodiment of the present invention.

FIG. 2 is a time chart showing signals of respective parts of FIG.

FIG. 3 is a time chart showing signals of respective parts in FIG.

FIG. 4 is a schematic diagram showing scanning lines of a display screen corresponding to FIG.

5 is a schematic diagram showing scanning lines of a display screen corresponding to FIG.

FIG. 6 is a schematic diagram showing a horizontal moving window according to the embodiment of FIG.

FIG. 7 is a schematic diagram showing scanning lines of an interlace type image display device.

FIG. 8 is a schematic diagram showing scanning lines of a progressive scanning type video display device.

FIG. 9 is a schematic diagram showing an interpolation method of scanning lines on a display screen according to a conventional technique.

FIG. 10 is a schematic diagram showing a method of interpolating a scan line on a display screen according to a conventional technique.

FIG. 11 is a schematic diagram showing distortion when a moving image is displayed by a conventional field interpolation method.

FIG. 12 is a schematic diagram showing an example in which the resolution is reduced by the conventional line interpolation method.

FIG. 13 is a block diagram showing an electrical configuration of a video display device according to the prior art.

FIG. 14 is a time chart showing signals of respective parts of FIG.

FIG. 15 is a time chart showing signals of respective parts in FIG.

16 is a schematic diagram showing an example in which the image quality is degraded in the prior art of FIG.

[Explanation of symbols]

 11, 12, 13 Field memory 14, 21 Level difference detector 15, 22 Level comparator 16, 20 Line memory 17 Switching signal generating circuit 18, 19 Switching switch 23 AND circuit

Claims (5)

[Claims] 1. An image for one frame to be displayed by a plurality of scanning lines is composed of an odd field signal representing an image displayed by each pixel on an odd scan line and each pixel on an even scan line. From an interlaced video signal that is transmitted by being divided into an even field signal that represents a video to be displayed, while displaying odd-numbered scanning lines and even-numbered scanning lines alternately on the same screen, In an image display method for forming an image, a first level difference, which is a difference in display level between pixels displayed adjacently, is compared with a first threshold value by an odd or even field signal being transmitted. , A second level difference, which is the difference between the display level of the pixel displayed by the odd-numbered or even-field signal being transmitted and the display level of the pixel one frame before, 2
Each of the scanning lines of the video signal when the first level difference is larger than the first threshold value or the second level difference is larger than the second threshold value, The scan lines in the odd or even field signal are displayed twice in succession while the first level difference is less than or equal to the first threshold value and the second level difference is Is less than or equal to the second threshold, the scanning lines in the odd field signal and the scanning lines in the even field signal are alternately displayed while each scanning line of the video signal is transmitted. Video display method. 2. The image display method according to claim 1, wherein at least one of the first threshold value and the second threshold value can be freely set. 3. The first level difference is calculated by comparing display levels between pixels on scanning lines displayed above and below with an odd or even field signal being transmitted. The video display method described in 2. 4. An odd field signal representing an image displayed by each pixel on an odd scan line, and an image for one frame to be displayed on a plurality of scan lines, and each pixel on an even scan line. From an interlaced video signal that is transmitted by being divided into an even field signal that represents a video to be displayed, while displaying odd-numbered scanning lines and even-numbered scanning lines alternately on the same screen, In a video display device for forming a video, a first field memory capable of storing a video signal being transmitted for one field and being readable at a speed twice the transmission speed, and a video signal read from the first field memory A second field memory that can store one field and can be read at twice the transmission speed, and one video signal read from the second field memory Field can be stored and the video signal read from the first field memory can be stored for one scanning line, and the third field memory can be read at twice the transmission speed. A readable first line memory, and a second line memory capable of storing one scanning line of a video signal read from the first field memory or the second field memory and readable at a speed twice the transmission speed, A first level difference detecting means for comparing the video signals read from the first field memory and the first line memory for each pixel, and a display level of a display level between adjacent pixels in response to an output from the first level difference detecting means. First level comparison means for comparing the first level difference, which is the difference, with a first threshold value, and a video signal read from the first field memory and the third field memory are displayed. The second level difference detection means for each comparison and the second level difference, which is the difference between the display levels of the respective pixels, are compared with the second threshold value in response to the output from the second level difference detection means. Switching means for switching and deriving a video signal to be displayed in response to the outputs from the second level comparing means and the first and second level comparing means, wherein the first level difference is greater than the first threshold value. Is larger or the second level difference is larger than the second threshold value, one scanning line portion read from the first field memory is transmitted during each scanning line of the video signal. The video signal is stored in the second line memory while being displayed, and then the video signal for one scanning line read from the second line memory is switched to be displayed, and the first level difference is the first threshold. Less than or equal to the value and the second level difference is the second threshold When it is lower, while the respective scan lines of the video signal is transmitted, while displaying a video signal of one scanning line to be read from the first field memory, the second
The video signal for one scanning line read from the field memory is stored in the second line memory, and then the video signal for one scanning line read from the second line memory is switched to be displayed. And a video display device. 5. The video display device according to claim 4, further comprising liquid crystal display means for displaying an image of the video signal derived from said switching means.