JP2900968B2 - Image display method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to video signal processing and image display technology in a display system such as a television, and more particularly, to a PDP (Plasma Display Pan).
The present invention relates to an image display method and an image display method for improving an image to be displayed in (e).

[0002]

2. Description of the Related Art In recent years, this PDP is excellent in a large screen among flat displays, and is capable of full-color display and high-speed gradation display. ).

In a pulse driving type PDP apparatus, for example, when a halftone display such as a television screen is performed, a video signal (video signal) for displaying an image is digitized, and a display field period is set to each bit of the video signal. The display is divided into corresponding subfields, and the number of display (discharge) pulses is assigned to each subfield to perform image display.

That is, since the PDP operates in binary, the display field period (time field) is divided by the bits of the video signal, and the display field period is divided into two for each short time subfield.
The image of the value is displayed sequentially, and the images are superimposed and combined to perform gradation display.

In this case, since the addressing time for driving the display pixels of the PDP occupies a larger ratio than the display pulse application time of the display pixels, the number of subfields (corresponding to the number of display pulses). ) And the number of display gradations increases, the displayed image becomes darker.

For this reason, it is difficult to obtain sufficient gradations (256 gradations (8-bit gradation = 8 subfields)) for displaying on a color television screen. Tone (6 subfields).

[0007]

By the way, a PDP with a small number of display gradations, for example, a television screen with a display bit rate of about 6 bits is used.
When the image is displayed on the DP, in a screen that changes sharply (a screen with a large change in brightness), since the false contour is close to the true image, the deterioration of the image quality is not so large.

However, on a screen that changes slowly (a screen with a small change in brightness), a false contour is generated at a certain distance from the true image, so that the false contour is conspicuous and the image quality is extremely impaired. There is a point, and the effective number of display gradations is reduced.

[0009] This invention has been made in view of the above problems, and an object can not conspicuous other false contour occurring in the display screen, and no decrease in resolution of the display image,
It is an object of the present invention to provide an image display method and an image display device capable of improving image quality.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method for converting an input video signal into a digital signal.
Display image by digital video signal on display panel (PD
When displaying the P), to detect the spatial frequency is less area of the display screen by the input video signal, a digital conversion level or data of a video signal corresponding to the detected area
The level of the digital video signal after digital conversion
It changed every field or every frame of the serial input video signal, which has features that it has to display an image based on a video signal containing a video signal for changing the level
You .

[0011]

According to the action-mentioned means, the video signal color demodulated by the input video signal is, by Rukoto passed through example <br/> low pass filter as a region detection unit, the region spatial frequency is low in the display screen is detected , video signals corresponding to this region is temporarily stored by including latch unit.
Preferably, the display pixels corresponding to the video signals of the latch section are divided into N × M groups, and the digital conversion levels of the video signals corresponding to the N × M pixels in each group are respectively set to the minimum display floor. N / (N ×
M) (n = 1,..., N × M), and is changed periodically for each field of the input video signal.

As described above, only the area where the brightness changes slowly on the display screen is detected, and the level of the video signal corresponding to this area is changed, while the brightness changes sharply on the display screen. The level of the video signal corresponding to the region remains unchanged.

Therefore, regarding the false contour generated on the display screen due to the digitization of the input video signal, the occurrence position of the false contour of the image of the portion where the brightness gradually changes on the display screen is within each group and for each field or Different for each frame, the false contour becomes inconspicuous.

On the other hand, the level of a video signal corresponding to a portion where the false contour of an image is not so noticeable, that is, a video signal corresponding to a region where the brightness changes sharply on the display screen cannot be changed. The resolution of the display image corresponding to the region that changes rapidly does not decrease.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, when an image based on an input video signal is displayed on a display panel (PDP; plasma display panel) in halftone, an area where the brightness gradually changes on the display screen of the image (the spatial frequency is changed). (Small area) is detected, and the level of the video signal corresponding to the same area is changed for only this area to shift the false contour generated on the display screen.

Therefore, as shown in FIG. 1, the image display device of the present invention comprises, for example, a display panel (PDP) 1 for displaying an image based on an input video signal, and a display panel (PDP) for converting the input video signal to a color difference signal. demodulates the video signal, the color demodulation synchronization separating unit 2 to separate a synchronizing signal, an a / D converter 3 to digital conversion of the video signal same color demodulation, lateral spatial frequency of the display screen for the video signal same color demodulation A low-pass filter (one-dimensional) 4 and a latch unit 5 for detecting and temporarily storing a portion where the color demodulation is small;
And a PDP 1 corresponding to a portion (video signal) stored in the latch unit 5 for generating a clock of a predetermined frequency (timing clock corresponding to a display pixel) in synchronization with the synchronization signal separated by N × display pixels
It has a control unit 7 for outputting control signals and timing signals for dividing into M groups, an M counter and an N counter, counts clocks from the clock generation unit 6, and outputs timing signals from the control unit 7. The comparison between the counter unit 8 that outputs a signal (address information) corresponding to the display pixel (position) of each group and the A / D conversion unit 3 based on the control signal from the control unit 7 and the signal from the counter unit 8 A comparison voltage generator 9 that generates a variable voltage (comparison level voltage) and a video interface 10 that receives an analog / digital converted video signal using the comparison voltage and performs control necessary for image display. Have.

More specifically, in this example, an analog system is adopted, and the low-pass filter 4 and the latch unit 5 detect only a portion where the brightness in the horizontal direction (each display line) of the display screen changes gradually. . In addition, the clock generation unit 6, the control unit 7, and the counter unit 8
The display pixels corresponding to the portion where the brightness changes gradually among the display pixels of the PDP 1 are divided into N × M groups. Further, the comparison voltage generator 9 is configured to output N ×
Different comparison voltages of approximately n / (N × M) (n = 1,..., N × M; n, M, and N are integers) of the minimum display gradation level are generated corresponding to the M display pixels. .

For example, while the same comparison voltage is generated for the display pixels at the same position in each group, the pattern of the comparison voltages generated corresponding to the display pixels in each group is the same for each group. Even
It changes periodically for each field or every frame.

Next, the operation of the image display apparatus having the above configuration and the operation of the image display method will be described in detail. First, an image (or a color image) based on an input video signal is displayed in halftone.

The color demodulation sync separation unit 2 separates a sync signal of an input video signal and demodulates the input video signal into a composite video signal of an original color signal. The color-demodulated video signal is input to the A / D converter 3 and the low-pass filter 4, respectively.

The one-dimensional low-pass filter 4 passes the video signal of the portion where the brightness of the display screen gradually changes (the portion where the horizontal spatial frequency is small) out of the video signal due to the operation thereof, and the latch portion 5 The video signals that have passed through the low pulse filter 4 are temporarily stored (for example, time corresponding to a field or a frame) sequentially.

The clock generator 6 generates a clock corresponding to the display pixel of the PDP 1 in synchronization with the synchronization signal of the input video signal, and outputs the clock to the counter 8. The control unit 7 controls the timing signal and the control signal for dividing the display pixels corresponding to the portion where the brightness gradually changes on the display screen into N × M groups based on the synchronization signal and the signal of the latch unit 5. The signal is sent to the counter unit 8 and the comparison voltage generation unit 9
Output to

The N counter of the counter unit 8 counts up every N horizontal display pixels of the display screen of each group, and the M counter of the counter unit 8 is M vertical display pixels of the display screen of each group. Count up every time.
The comparison voltage generator 9 to which the count value is input generates a different comparison voltage for each display pixel of each group. In addition,
Part the comparison voltage generator 9 that have the brightness of the display screen is changed abruptly (display pixels of the spatial frequency is greater area of the display screen), that is a constant reference voltage for the display pixel other than the above-mentioned groups Occurs.

The A / D converter 3 uses the comparison voltage from the comparison voltage generator 9 when digitally converting the color-demodulated video signal. That is, within each group, the conversion level of the digital conversion is different for each display pixel,
In other words, the level of the video signal corresponding to each display pixel is changed and the video signal is A / D converted. Note that the conversion level of the digital conversion is constant for the video signals corresponding to the display pixels other than the groups.

The pattern of the comparison voltage generated corresponding to the display pixels of each group is the same for each group.
(Even number) or every frame. For example,
For the display pixels of each group, the comparison voltage generated corresponding to the display pixel corresponding to the same position in the same field is the same, but between the fields (for example, between the odd field and the even field), The corresponding generated comparison voltages are different.

Specifically, at the time of digital conversion of an input video signal, for example, a PDP in a portion where brightness gradually changes on the display screen (a portion where the spatial frequency of the display screen is small)
Assuming that one display pixel is divided into groups of N = M = 5, the video signal level corresponding to the display pixel of each group in a certain field is 1/25, 25/25, 2/25, 24/2
5, ..., and that periodically variable by 14 / 25,15 / 25. In addition, 1/25, 25/25, 2/2
The patterns of 5 , 24/2 5 ,..., 14/25, 15/25 are periodically changed for each field.

In this manner, the digital conversion level of the video signal corresponding to the display pixels of each group corresponds to the display pixels of each group (the display pixels in the area where the spatial frequency of the display screen is low). Gradation level 1
/ 25, 25/25, 2/25, 24/2 5 , ..., 14
/ 25, 15/25 (pattern), and the digital conversion level of other video signals (video signals in a region where the spatial frequency of the display screen is large) is kept constant.

The pattern of the variable digital conversion level is periodically changed for each field of the video signal, and the video signal converted at the variable digital conversion level or the fixed digital conversion level is input to the video interface 10. You.

Then, when an image based on a video signal is displayed on the PDP 1 by the video interface 10, a false contour occurs on the display screen of the image based on the video signal due to digitization of the video signal. However, as described above, at the time of digital conversion of the video signal, the level of the video signal corresponding to each display pixel in the portion where the brightness changes gradually on the display screen is changed, and within the group of the display image of the PDP 1 In addition, since the level of the video signal is changed for each field, a false contour caused by the digital conversion of the video signal becomes inconspicuous. That is, the position of the false contour differs for each group and each field, that is, the distance between the false contour of the display image and the true image (display image) is not constant for each group and each field.

In a portion where the brightness of the display screen changes abruptly (a region where the spatial frequency is large), the resolution of the display image does not deteriorate because the digital conversion level of the video signal is constant. .

As described above, the spatial frequency of the display screen of the PDP 1 is detected, and the level of the video signal corresponding to the portion where the spatial frequency is low (the portion where the brightness of the display screen changes gradually) is changed to display the image to be displayed. The false contour occurrence position is changed in a portion where the brightness is gentle, while the digital conversion level of the video signal is not changed in a portion where the spatial frequency of the display screen is large (a portion where the brightness of the display screen changes sharply). I have to.

Therefore, a false image is not conspicuous, a true image (display image) is clear, and the improvement of the image quality is particularly remarkable in a screen that changes slowly (a screen with a small change in brightness). Since the resolution of a display image (that is, an image in which false contours are not conspicuous) corresponding to a portion where the brightness changes sharply does not deteriorate, image quality can be further improved.

FIG. 2 is a schematic block diagram of a display image apparatus showing another embodiment of the present invention. In FIG. 1, FIG.
The same parts as those described above are denoted by the same reference numerals, and redundant description will be omitted.

The image display device of this embodiment is the same as the PD of FIG.
P1, color demodulation sync separation section 2, A / D conversion section 3, and video interface 10, M line memory section 1
1, low-pass filter (two-dimensional) 12, latch unit 1
3, a level change pattern generator 14, a controller 15, and an adder 16.

The A / D conversion unit 3 is a color demodulation synchronization separation unit 2
The video signal color-demodulated is converted into a digital signal (the number of display bits + 2 raised to the power of x, x = N × M), and the M line memory unit 11 sequentially stores the digital video signal for M lines (for example, for a half screen). I do.

The low-pass filter 12 passes through a region where the spatial frequency in the vertical and horizontal directions of the display screen based on the digital video signal of the M-line memory unit 11 is small (a region where the brightness of the display screen changes gradually). A digital video signal corresponding to an area where the vertical and horizontal spatial frequencies passing through the filter 12 are small is temporarily stored.

The level change pattern generating section 14 generates a level change pattern for varying a reference level for turning on / off the display least significant bit of the digital video signal corresponding to the region where the vertical and horizontal spatial frequencies are small in a predetermined pattern. Occur.

The control section 15 outputs a clock of a predetermined frequency (a control signal such as a timing clock of a display pixel) in synchronization with a synchronization signal of an input video signal, and outputs a low pulse filter 12, a latch section 13, and a level change pattern. The generator 14 is controlled.

The adder 16 turns on / off the least significant bit of the display bit of the digital video signal converted by the A / D converter 3 according to the level of a certain pattern. The video interface 10 controls the display of an image by driving the pixels of the PDP 1 based on the digital video signal changed by the adder 16.

In addition, as a supplementary explanation, in this example, a digital system is adopted, and the M-line memory unit 11 is used.
Is to temporarily store a digital video signal for a predetermined display line when storing an analog / digital converted digital video signal, but a capacity sufficient to detect an area where the spatial frequency in the vertical and horizontal directions of the display screen is small is sufficient. Yes,
For example, the capacity may be about half of the display screen or less.

The low-pass filter 12 and the latch unit 13 receive the digital video signal from the M-line memory unit 11 and detect an area where the spatial frequency in the vertical and horizontal directions is small.
This detection area is temporarily stored.

The level change pattern generation section 14 generates a pattern for comparing the level of the video signal corresponding to the area stored in the latch section 13. In this case, the display pixel corresponding to the area stored in the latch
× M groups, and corresponding to the same N × M pixels, the minimum display gradation level is substantially n / (N × M).
(N = 1,..., N × M). Moreover, the value (level change value) of each pattern may be different, or may be periodically different for each field or each frame.

The adder 16 is a digital video signal that has been A / D-converted based on the pattern generated by the level change pattern generator 14 and is the most significant of the signals corresponding to the area where the brightness change is small on the display screen. Vary the lower bit level. In this case, the A / D converted digital video signal (the number of display bits + 2 x bits, x = N ×
In M), on / off of the least significant bit of the display bit is determined by 2 x bits.

The video interface 10 processes the digital video signal obtained by the adder 16 in the same manner as in the previous embodiment, and performs control necessary for image display based on the digital video signal.

The operation of the image display device having the above configuration and the operation of the image display method will be described in detail. First, assuming that an image (or a color image) based on an input video signal is to be displayed in halftone, the input video signal is demodulated into a video signal of an original color signal by a color demodulation / synchronization / separation unit 2, and the color-demodulated video signal is reproduced. Is digitally converted by the A / D converter 3, and a digital video signal level change corresponding to a change in the luminance level of the display screen is detected based on the digitally converted video signal.

In this case, digital video signals of a predetermined number of display lines (M lines; M is an integer) of the display screen are temporarily stored in the M line memory unit 11 and the digital video signals of the M line memory unit 11 are stored in the memory. It passes through a two-dimensional low-pass filter 12. At this time, the control unit 15 generates a clock of a predetermined frequency in synchronization with the synchronization signal of the input video signal, and the low-pass filter 12 operates by timing of this clock.

Therefore, when there is an area where the brightness changes gradually on the display screen corresponding to the digital video signal of the M line memory section 11, the digital video signal corresponding to this area is temporarily stored in the latch section 13. .
However, if there is no area on the display screen where the brightness gradually changes, no digital video signal is stored in the latch section 13.

In this manner, a region having a small spatial frequency is detected on the display screen for M lines. The detection is performed by using a two-dimensional low-pass filter 12 in a digital system in contrast to the analog system in the previous embodiment. Therefore, not only a region where the horizontal spatial frequency is low, but also a region where the vertical spatial frequency is low, that is, a region where the vertical and horizontal spatial frequencies are low can be detected.

When a digital video signal is stored in the latch unit 13, a level change pattern generation unit 14 generates a pattern of a predetermined level change value based on the digital video signal, and a timing of a clock of a predetermined frequency from the control unit 15 is output. Outputs each level change value of the pattern. Note that each level change value of the pattern is not only positive but also negative.

The adder 16 adds the level change value from the level change pattern generator 14 to the digital video signal obtained by the A / D converter 3, that is, the brightness of the display screen changes gradually. The level of the digital video signal corresponding to the area is varied. Then, the digital video signal corrected by the level change value is input to the video interface 10.

Then, the video interface 10 drives the display pixels of the PDP 1 on the basis of the digital video signal to display an image. On the display screen of the PDP 1, a false contour due to digitization of the input video signal is displayed. Occurs.

However, as described above, in the area where the brightness of the display screen changes gradually, the level of the digital video signal corresponding to each display pixel in the area is corrected with a different level change value. Since the value pattern is changed for each field or for each frame, the position of the false contour of the display image can be shifted as in the previous embodiment, and the false contour becomes inconspicuous.

That is, the position of the false contour is determined for each group,
This is because the distance differs between the fields, that is, the distance between the false contour of the display image and the true image (display image) is not constant for each group and each field.

Moreover, in a region where the brightness of the display screen changes sharply (a region where the spatial frequency is large), that is, in a region where the false contour of the image is not conspicuous, the level of the digital video signal is kept unchanged. Therefore, the image quality can be improved because the resolution of the display image on the screen where the brightness changes sharply does not deteriorate.

[0055]

As described above, according to the present invention, an image based on an input video signal is displayed on a display panel (PDP;
When displaying halftones on a plasma display panel), a region where the brightness changes slowly (a region with a small spatial frequency) on the display screen of the same image is detected, and only this region corresponds to the video signal corresponding to the same region. Digital
Conversion level or digital video after digital conversion
The level of the signal is different for each field of the input video signal.
In other words, the false contour generated on the display screen is shifted for each frame , so that the false contour of the display image can be made inconspicuous. As a result , the true image becomes clear,
Also, since the level of the video signal is not changed in an area where brightness is sharply changed on the display screen (an area where false contours are not conspicuous), the resolution of the displayed image in the same area may not be reduced. Can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an image display device showing one embodiment of the present invention.

FIG. 2 is a schematic block diagram of an image display device showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 PDP (Plasma display panel) 2 Color demodulation synchronization separation part 3 A / D conversion part 4 Low pal filter (one-dimensional) 5, 13 Latch part 6 Clock generation part 7, 15 Control part 8 Counter part 9 Comparison voltage generation part Reference Signs List 10 Video interface 11 M line memory unit 12 Low-pass filter (two-dimensional) 14 Level change pattern unit 16 Addition unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 5/66 101 H04N 5/66 101B

Claims (5)

(57) [Claims] A digitally converted input video signal;
Display panel with digital video signal (PDP)
To display on the detected regions spatial frequency is low in the display screen by the input video signal, a digital conversion level or daisy video signal corresponding to the detected area
The level of the digital video signal after barrel conversion, the change in input <br/> force per field of the video signal or each frame, and to display an image based on a video signal containing a video signal for changing the level An image display method comprising: 2. A display panel (PDP) for displaying an image based on a digital video signal obtained by digitally converting an input video signal.
In the image display method for halftone display, while detecting a portion where the horizontal spatial frequency of the display screen is small by a video signal obtained by color demodulation of the input video signal, temporarily stores the detected portion, and stores the detected portion in the stored portion. The display pixels of the corresponding display panel are divided into N × M groups, and the digital conversion level of the video signal corresponding to the N × M pixels in each group is set to n / (N × M) of the minimum display gradation. (N = 1,..., N × M)
And an image display method for changing an input video signal for each field or frame, and displaying an image based on the video signal digitally converted using the digital conversion level. 3. A display panel (PDP) for displaying an image based on a digital video signal obtained by digitally converting an input video signal.
In the image display method for displaying a halftone image, the digital video signal is stored for a predetermined number of display lines, and an area having a small vertical and horizontal spatial frequency of a display screen is detected by the stored digital video signals of the plurality of display lines. The detected area is temporarily stored, the least significant bit of the digital video signal is turned on / off corresponding to the stored level, and the level is varied by changing the input video signal for each field or frame. An image display method, wherein an image is displayed based on a digital video signal. 4. A display panel (PDP) for displaying an image based on a digital video signal obtained by digitally converting an input video signal.
A low-pass filter for detecting a portion having a small horizontal spatial frequency of a display screen by using a video signal obtained by color demodulating the input video signal; and a low horizontal spatial frequency of the detected display screen. Latch means for temporarily storing only a portion, control means for dividing display pixels of the display panel corresponding to the temporarily stored portion into a plurality of N × M groups, and display of each group divided by the control means For each pixel, the level of the digital conversion is set to n / (N ×
M) (n = 1,..., N × M), and a comparison voltage generating means for generating a comparison voltage which varies for each field or every frame of the input video signal. The input video signal is digitally converted using the generated comparison voltage, an image is displayed based on the digitally converted video signal, and the false contour position of the display screen of the image is determined within each group and for each field or frame. An image display device characterized in that it is changed every time. 5. A display panel (PDP) for displaying an image based on a digital video signal obtained by digitally converting an input video signal.
Storage means for sequentially storing the digital video signals for a predetermined number of display lines on a display screen, and a vertical and horizontal space of the display screen based on the stored digital video signals of a plurality of display lines. A low-pass filter for detecting an area having a small frequency; a latch means for temporarily storing only an area having a small vertical and horizontal spatial frequency of the detected display screen; and a digital video signal for each display pixel corresponding to the temporarily stored area. Level change pattern generating means for generating a level change pattern for changing the least significant bit on / off with different values, and changing the level change pattern for each field or frame of the input video signal; The level change value is set in the vertical and horizontal directions of the digital video signal. Control means for controlling the least significant bit of a digital video signal corresponding to an area having a small spatial frequency, wherein an image is displayed based on the digital video signal including the digital video signal whose level has been changed, and a display screen of the same image Wherein the false contour position is changed within each group and for each field or each frame.