JPH04246684A - Scanning line width correcting method - Google Patents

Abstract

PURPOSE:To remove a lateral stripe pattern on a screen in the gap area between scanning lines and to excellently correct the gap between scanning lines even when the number of scanning lines is decreased to 1/n times (n: interger) of a maximum value. CONSTITUTION:The number (n) of scanning lines is found from the horizontal and vertical synchronizing signals HS and VS of an input video signal and when the (n) is smaller than the maximum number N of scanning lines which can be displayed on a display device, namely, when there are gap areas generated between the scanning lines, an electron beam is polarized vertically with a high frequency signal together with a vertical saw-tooth wave signal and vibrated vertically on the screen to apparently increase the width of each scanning line on the screen. Therefore, the electron beam strikes on even the gap areas formed owing to a decrease in the number of scanning lines to solve the problem that an image becomes unclear owing to the lateral stripe pattern of the gap areas.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning line width correction method, and more particularly to a scanning line width correction method for removing horizontal striped patterns caused by gaps between scanning lines on a screen.

0002

2. Description of the Related Art In an NTSC television system, a screen display with 525 scanning lines per frame is performed by interlaced scanning at a horizontal synchronization frequency of 15.75 kHz. In the HDTV (high-definition television) system, interlaced scanning is similarly performed, but in order to increase the definition of the displayed image, scanning is performed per frame at an even higher horizontal synchronization frequency, for example, 33.75 kHz. A screen display with 1125 lines is performed. On the other hand, in computer displays, non-interlaced scanning is generally employed to display still image information such as characters and graphics. Even in this non-interlaced scanning, a horizontal frequency is used depending on the field of use, depending on the degree of definition required for displaying characters, graphics, etc. In this way, a so-called multi-scan display device is used to commonly display multiple video signals using an interlace method or a non-interlace method with different horizontal synchronization frequencies, that is, different numbers of scanning lines per frame. be. For example, the KX-14HD1 model manufactured by Sony Corporation is a multi-scan display device that can selectively display a television signal or a video signal from a computer. This display device detects the synchronization signal frequency of the input video signal and automatically follows that frequency, and outputs a television signal with a horizontal synchronization frequency of 15.75 kHz, a computer output video signal, and a horizontal synchronization frequency of 2.
4kHz high-density computer output video signal and 31.
Displays a 5kHz captain video signal.

0003

[Problem to be Solved by the Invention] In a multi-scan display device, the spot size of the electron beam is adjusted so that the electron beam uniformly impinges on the entire display screen when scanning the maximum number of displayable scan lines. Fixed selection. Therefore, when the frequency of the horizontal synchronizing signal becomes low and fewer scanning lines than the maximum number of scanning lines are scanned, a gap region is created between adjacent scanning lines where the electron beam does not collide. This gap area stands out as a horizontal stripe pattern on the screen.
Make the displayed image difficult to see. As a method for solving the above-mentioned problem due to the reduction in the number of scanning lines, there is a method using a scan converter. In this method, when the number of scanning lines is reduced to a fraction of an integer, the gaps between the scanning lines are filled by continuously scanning the same scanning line an integer number of times. However, with this method, control is complicated when the number of scanning lines is not an integer fraction of the maximum number of scanning lines, and especially when the reduction in the number of scanning lines is less than 1/2 of the maximum number of scanning lines, the difference between each scanning line is Since the gap is narrower than the spot size of the electron beam, if an attempt is made to add a scanning line to the gap, there is a problem in that adjacent scanning lines will overlap. In addition, it is possible to increase the electron beam spot size according to the degree of reduction in the number of scanning lines, but if this is done, the influence of the Gaussian distribution of electrons in the electron beam spot will increase, and the sharpness of the displayed image will deteriorate. There is a risk that it will decrease. Furthermore, there is a limit to the range in which the spot size of the electron beam can be varied while keeping the focus constant.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a scanning line width correction method for eliminating horizontal striped patterns on a screen caused by gap areas between scanning lines. Another object of the present invention is to provide a scanning line width correction method that satisfactorily corrects gaps between scanning lines even when the number of scanning lines is reduced to less than one integer fraction of the maximum value.

[0005]

[Means and effects for solving the problems] In the scanning line width correction method of the present invention, the number of scanning lines n is determined based on the horizontal and vertical synchronizing signals Hs and Vs of the input video signal, and n is the number that can be displayed on the display device. When the number of scanning lines is smaller than the maximum number N, that is, when there is a gap between scanning lines, the electron beam is deflected vertically using a high-frequency signal together with a vertical sawtooth signal, and the electron beam is vibrated vertically on the screen. so that the width of each scan line increases in appearance. As a result, the electron beam also collides with the gap area caused by the decrease in the number of scanning lines, and it is possible to eliminate the problem that the image becomes difficult to see due to the horizontal striped pattern in the gap area.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing a multi-scan display device for implementing the scanning line width correction method of the present invention. Here, to simplify the explanation, a case where an image is displayed by non-interlaced scanning using a monochrome display device will be mainly described. In FIG. 1, an input monochrome video signal is sent to a video amplifier 12 via an input terminal 10.
is supplied to After the input video signal is sufficiently amplified by a video amplifier 12, it is sent to a cathode ray tube (hereinafter referred to as "CRT") 1.
6 (not shown) to control the display brightness of the CRT. The input video signal is further supplied to a synchronization signal separation circuit 14 via an input terminal 10. The synchronization signal separation circuit 14 includes a horizontal synchronization separation circuit that is a high-pass filter and a vertical synchronization separation circuit that is a low-pass filter, and these circuits separate the horizontal synchronization signal H from the input video signal.
s and vertical synchronization signal Vs are separated and output. The horizontal and vertical synchronization signals are provided by horizontal and vertical oscillation circuits 18, respectively.
20. The horizontal oscillation circuit 18 is synchronized with the horizontal synchronization signal Hs from the synchronization signal separation circuit 14 and generates a stable horizontal pulse signal of the same frequency, and supplies it to the horizontal deflection circuit 22. The horizontal deflection circuit 22 generates a horizontal sawtooth signal in response to the supply of the horizontal pulse signal, and
16 horizontal deflection coils 16a. Further, the vertical oscillation circuit 20 is synchronized with the vertical synchronization signal Vs from the synchronization signal separation circuit 14 and generates a stable vertical pulse signal of the same frequency, and the vertical deflection circuit 24 generates a vertical saw in response to the vertical pulse signal. Generate wave signals. The amplitude of this vertical sawtooth signal is equal to the amplitude VA in order to display the input video signal with the maximum number of scan lines.

The horizontal and vertical synchronizing signals Hs and Vs from the synchronizing signal separation circuit 14 are further supplied to a control circuit 26. As will be described later, the control circuit 26 includes a scanning line number determining circuit, a vertical sawtooth amplitude determining circuit, and a high frequency amplitude determining circuit, and generates control signals A and B based on the synchronizing signals Hs and Vs. Control signals A and B are provided to one input of multipliers 28 and 30.

The vertical sawtooth signal from the vertical deflection circuit 24 is multiplied by a control signal A in a multiplier 28 to obtain an amplitude VA'.
After being adjusted to , it is supplied to one input terminal of the analog adder 34 . Further, the high frequency generator 32 generates a high frequency signal with a peak-to-peak value VD, and this high frequency signal is multiplied by the control signal B in the multiplier 30 and adjusted to the amplitude VD'. supplied to the other input end. It is desirable that the frequency of the output signal of the high frequency generator is at least twice the luminance band of the video signal including the maximum number of displayable scanning lines. The output signal of the adder 36 becomes a modified vertical sawtooth wave signal in which a high frequency signal is superimposed on a vertical sawtooth wave signal, and is supplied to the vertical deflection coil 16b of the CRT 16. The horizontal and vertical deflection coils 16a, 16b cooperate to deflect the electron beam to draw a plurality of scanning lines on the screen of the CRT 16. Since the modified vertical sawtooth signal contains a high frequency signal, the vertical deflection means may use an electrostatic deflection electrode instead of a deflection coil in order to achieve good deflection.

[0009] Here, each scanning line is not linear in the horizontal direction as in the conventional case, but becomes a scanning line that moves in the horizontal direction while vibrating at high speed in the vertical direction due to the high frequency signal superimposed on the vertical sawtooth wave. Please note that. That is, the width of the electron beam appears to have increased because the electron beam vibrates slightly in the vertical direction at a speed sufficiently faster than the speed at which the electron beam moves in the horizontal direction. When the number of scanning lines on the screen decreases due to switching of the input video signal, and a gap is created between adjacent scanning lines in which the electron beams do not collide, the control circuit 26 generates a control based on the pulse signals Hs and Vs. By appropriately adjusting the amplitude of the vertical sawtooth signal and the amplitude of the high frequency signal according to the signal and causing the electron beam to impinge on the gap areas on the screen, it is possible to remove the horizontal striped pattern caused by the gap areas.

FIGS. 2 and 3 are explanatory diagrams for understanding the gist of the present invention. FIG. 2 shows a screen when displaying an image consisting of the maximum number of scanning lines. In this example, in order to simplify the explanation, the maximum number of scanning lines is shown as seven, but in general, the maximum number of scanning lines is N (positive integer). The diameter d of the electron beam spot is selected to be equal to the distance between the centers of adjacent scan lines, so that the electron beam scans the entire screen when displaying an image consisting of the maximum number of scan lines. The vertical distance L of this image is L=N×
It is represented by d. When the input video signal is switched and the number of scanning lines is reduced from the maximum number of seven scanning lines to, for example, three, a gap region is created between the scanning lines because the size of the electron beam spot is constant. In the present invention, in order to cause the electron beam to collide with this gap region, as described above with reference to FIG. 1, a high frequency signal is superimposed on a vertical sawtooth wave, and the electron beam is vibrated in the vertical direction for each scanning line. This situation is shown for the central scanning line in FIG. Here, if the vertical distance traveled by the center of the electron beam spot is D, then the width of the scanning line is the sum of the distance D and the diameter d. In order to display an image with the maximum number of scanning lines and an image of the same size, first, the total width of n scanning lines (the number of scanning lines varies depending on the video signal) with a width of D + d must be Vertical width N of the image in Figure 2
- Must be equal to d. Therefore, the following formula is obtained.

[0011] n・(D+d)=N・d
(1) From equation (1), find D: D={(N/n)-1)}・d
(2) becomes. The amplitude of the signal supplied to the vertical deflection coil 16b is proportional to the vertical distance D above the display screen. When the conversion constant for converting the vertical distance into signal amplitude is K, the amplitude VD' of the high frequency signal supplied to the adder 34 is expressed by the following equation. VD'=K・{(N/n)−1}・d
(3) From equation (3), if the amplitude VD of the output signal of the high frequency generator 32 is set to VD=K, the control signal B supplied to the multiplier 30 is {(N/n)-1}・d The signal may be a signal corresponding to . Further, when the maximum number of scanning lines is displayed, that is, when N=n, VD'=0 from equation (3).

Second, it is necessary to reduce the amplitude of the vertical sawtooth wave so that the scanning lines are drawn on the display screen without any gaps between them. In FIG. 2, the amplitude VA of the vertical sawtooth wave representing the maximum number of scanning lines is proportional to the distance l1 between the centers of the top and bottom scanning lines, so VA is expressed by the following equation.

VA=K・(N−1)・d
(4) The amplitude VA' of the vertical sawtooth wave when the scanning lines are drawn without gaps in FIG. 3 is proportional to the distance l2 between the centers of the top and bottom scanning lines, so VA'
is expressed by the following formula. l2=(n-1)・(D+d) VA'=K・(n-1)・(D+d) =K・N・(1/n)・(n-1)・d (
5) Therefore, the vertical sawtooth amplitudes VA and VA'
The ratio of is expressed by the following formula. VA'/VA={K・N・(1/n)・(n-1)・d
)}/[{K・(N-1)}] ={N・(n-1)}/{(N-1)・n}={N/(
N-1)}・{1-(1/n)}
(6) From equation (6), the control signal A supplied to the multiplier 28 is {
A signal corresponding to N/(N-1)}·{1-(1/n)} may be used.

To summarize the above, in order to prevent a gap from occurring due to a decrease in the number of scanning lines when switching from a video signal with a maximum number of scanning lines N to a video signal with a smaller number of scanning lines n, The amplitude of the high frequency signal superimposed on the vertical sawtooth wave is a value proportional to {(N/n)-1}・d,
The amplitude of the vertical sawtooth wave is the amplitude when the maximum number of scanning lines is displayed.
It may be multiplied by N/(N-1)}/{1-(1/n)}.

FIG. 4 shows a circuit for determining the number of scanning lines 38, a vertical sawtooth amplitude determining circuit 40, a high frequency signal amplitude determining circuit 42, and storing the maximum number of scanning lines N commonly used by these circuits. 2 is a block diagram showing a control circuit 26 including a memory device 44. FIG. Memory 44 and other memory devices described below may be, for example, digital setting switches. As will be described later, the scanning line number determination circuit 38 receives horizontal and vertical synchronizing signals Hs.
, Vs, the scanning line value n of the input video signal is determined and supplied to a vertical sawtooth amplitude determining circuit 40 and a high frequency amplitude determining circuit 42. Additionally, circuits 40 and 42 are supplied with a maximum scan line value N from a memory 44. From the values n and N, the vertical sawtooth amplitude determining circuit 40 calculates {N·(N−
1)}・{1-(1/n)} The high-frequency amplitude determining circuit 42 generates a control signal A corresponding to {(N/n)-1}
- Generate control signal B corresponding to d.

FIG. 5 is a block diagram showing the scanning line number determination circuit 38 in detail. The horizontal synchronization signal Hs and vertical synchronization signal Vs from the synchronization signal separation circuit 14 are supplied to a horizontal period detection circuit 48 and a vertical period detection circuit 50, respectively. The horizontal and vertical period detection circuits 48 and 50 include a counter circuit and a reciprocal circuit, and calculate the frequency by counting the input pulses, and calculate the reciprocal of the frequency to obtain digital values TH representing the horizontal period and vertical period, respectively. and TV
Output. The integrator 52 performs a charging operation to generate a ramp signal during a vertical blanking period of the vertical synchronization signal. The peak value of the gradient wave signal is determined by the analog-to-digital converter 5.
4, a digital value TB representing the vertical blanking period
After being converted into , it is supplied to one input terminal of the subtraction circuit 56 . The other input terminal of the subtraction circuit 56 is supplied with the digital value TV from the vertical synchronization detection circuit 56, and the output terminal thereof is supplied with a digital value (TV-TB) representing only the period during which a plurality of horizontal scanning lines are drawn. appear. The value (TV-TB) is supplied to one input terminal of the division circuit 58, and the value TH is supplied to the other input terminal. The division circuit 58 is (TV-TB)
/TH is calculated and a digital value n indicating the number of scanning lines in one frame is output. If the video signal is of an interlaced scanning type, it is necessary to double the digital value n. When interlaced and non-interlaced video signals are switched and input, the digital values n and 2
A switch may be provided to select n and supply it to the output terminal, and the switch may be switched according to the input video signal.

FIG. 6 is a block diagram showing the memory 44 and vertical sawtooth amplitude determination circuit 40 in detail. Memory 44 supplies the maximum scan line value N to one input of subtraction circuit 60 and to one input of division circuit 62 . The memory 64 stores the value 1 and supplies this value to the other input terminal of the subtraction circuit 60. The subtraction circuit 60 subtracts 1 from the value N and supplies the output value N-1 to the other input terminal of the division circuit 62. The division circuit 62 divides the value N by N-1 and supplies the output value N/(N-1) to one input terminal of the multiplication circuit 66 . The stored value 1 of the memory 64 is also supplied to one input terminal of a division circuit 68 and a subtraction circuit 70. The division circuit 68 receives the value n from the scanning line discrimination circuit 38 at the other input terminal, divides 1 by n, and supplies the output value 1/n to the other input terminal of the subtraction circuit 70 . The subtraction circuit 70 subtracts 1/n from 1 and supplies the output value 1-(1/n) to the other input terminal of the multiplication circuit 66. The multiplication circuit 66 is
Output value N/(N-1) of division circuit 62 and subtraction circuit 70
Multiply the output value of 1-(1/n) and get the value {N/(N-1)
}・{1-(1/n)} is output. This output value is obtained by a digital-to-analog converter (hereinafter referred to as "DAC") 72.
It is converted into an analog signal and becomes the control signal A.

FIG. 7 is a block diagram showing the memory 44 and high frequency amplitude determining circuit 42 in detail. The memory device 44 is
The value N is supplied to one input of the divider circuit 74. The division circuit 74 receives the value n from the scanning line number determination circuit 38 at the other input terminal, divides the value N by n, and supplies the output value N/n to one input terminal of the subtraction circuit 76 . Memory 78 stores the value 1 and supplies this value to the other input of subtraction circuit 76 . The subtraction circuit 76 subtracts 1 from N/n and supplies the output value (N/n)−1 to one input terminal of the multiplication circuit 80 . A memory 82 stores the diameter d of the electron beam spot determined by the conditions for displaying the maximum number of scanning lines, and supplies the value d to the other input terminal of the multiplication circuit 80. The multiplication circuit 80 multiplies the value (N/n)-1 and d, and the output value {(
N/n)-1}・d is output. This output value is DAC8
4, it is converted into an analog signal and becomes the control signal B.

Although the preferred embodiments of the present invention have been described above, various modifications can be made to the present invention. For example, the vertical sawtooth amplitude determining circuit 40 and the high frequency amplitude determining circuit 42, excluding the DAC, can be implemented by one microprocessor. Furthermore, in the embodiment, the adder superimposes the high frequency signal on the vertical sawtooth signal and supplies it to the vertical deflection means, but it is also possible to provide a vertical deflection means exclusively for the high frequency signal and supply the high frequency signal separately. . Furthermore,
In the above description, a monochrome CRT has been described, but the present invention can also be applied to color CRTs such as trinitron tubes and inline tubes. It can also be used in color projectors that use three monochrome CRTs.

[0020]

[Effect] In the scanning line width correction method of the present invention, when a gap region occurs between adjacent scanning lines due to a decrease in the number of scanning lines,
The electron beam is deflected vertically using a high-frequency signal together with a vertical sawtooth signal, causing the electron beam to oscillate vertically on the screen, thereby increasing the apparent width of each scanning line on the screen. As a result, the electron beam also collides with the gap region caused by the reduction in the number of scanning lines, and it is possible to eliminate the problem that the image becomes difficult to see due to the horizontal striped pattern in the gap region. Also,
Gap correction is easy to control even if the scan line reduction is not an integer fraction of the maximum number of scan lines, especially when adjacent scan lines overlap even if the gap between scan lines is smaller than the electron beam spot size. It is possible to satisfactorily correct the gap between scanning lines without causing any problems.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a display device that implements the scanning line width correction method of the present invention.

2 and 3 are simplified diagrams for explaining the principle of the present invention.

FIG. 4 is a block diagram showing the configuration of the control circuit in FIG. 1;

FIG. 5 is a block diagram showing details of the scanning line number determination circuit in FIG. 4;

FIG. 6 is a block diagram showing details of the vertical sawtooth amplitude determination circuit of FIG. 4;

FIG. 7 is a block diagram showing details of the high frequency amplitude determination circuit of FIG. 4;

[Explanation of symbols]

16 CRT 22 Horizontal deflection circuit 24 Vertical deflection circuit 26 Control circuit 28, 30 Multiplication circuit 32 High frequency generator 34 Adder

Claims (1)

[Claims] Claim 1: When a gap region where the electron beam does not collide occurs between a plurality of scanning lines drawn on the screen, the electron beam is vibrated in the vertical direction with respect to each scanning line in accordance with a vertical deflection signal. A scanning line width correction method in which the electron beam collides also in the gap region.