JPH02215294A - Digital convergence corrector - Google Patents

Abstract

PURPOSE:To visually reduce a raster unevenness and to improve a picture quality by alternately using the convergence corrected data of an upper adjoining scanning line and the convergence corrected data on a lower adjoining scanning line as the scanning in one scanning period. CONSTITUTION:A field discriminating part 11 fetches a signal from an H address counter 4 and a V blanking pulse input terminal 2 and executes the even/odd discrimination of a field. An AND output 53 of a field discrimination output 51 and an H address counter lowest order bit output 52 is added to a V address counter 5 by a V address adder 13. For such a reason, for the read address in the perpendicular direction of a memory 6, in the even field, the output of the V address counter 5 itself is designated, and in the odd field, the output of the V address counter 5 itself and the output, in which 1 is added to the output of the V address counter 5, are alternately outputted for each convergence correction output point in a horizontal direction.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a convergence correction device in a television receiver or display using a cathode ray tube.
In particular, the present invention relates to a digital convergence correction device that can reduce the memory capacity of a memory that stores convergence correction data and can reduce costs.

[Conventional technology]

As shown in Japanese Patent Publication No. 56-40355, a digital convergence correction device capable of performing convergence correction with high precision stores the convergence correction amount required at each point on the screen as convergence correction data in a digital format in memory. This convergence correction data is read out in synchronization with the raster scan in the cathode ray tube, and the convergence correction data is converted into an analog signal to obtain a convergence correction signal, which is used to perform convergence correction of the electron beam. The amount of convergence correction required for each point on the screen that requires convergence correction (convergence correction point) can be determined independently, and a convergence correction signal with the desired waveform can be easily obtained. be able to.

Hereinafter, a conventional digital convergence correction device will be explained in detail to the extent necessary with reference to FIG.

In FIG. 2, 1.2 are horizontal blanking pulses H, BLK and vertical blanking pulses V, BLK, respectively, synchronized with raster scanning in a cathode ray tube (not shown).
This is an input terminal for inputting .

Also, 3 is PLL (phase locked loop),
4.5 is the read address of the memory 6, which will be described later.
H address, ■H address signal that specifies the address, ■
an H address counter that generates each address signal;
■It is an address counter.

Further, 6 is a memory for storing convergence correction data, 7 is a digital/analog converter (DAC), 8 is a low-pass filter (L'PF) for interpolating the signal, and 9 is an amplifier for driving the convergence yoke 10, which will be described later. (AMP), and 10 is a convergence yoke (CY) that generates a compensating magnetic field.

It is now assumed that a clock is generated at the output of the PLL 3, which is synchronized in phase with the horizontal blanking pulse H9BLK having the horizontal deflection frequency [H from the input terminal l, and which has a frequency multiplied by f.

The H address counter 4 counts the output of the PLL 3 and generates an H address signal specifying a read address in the memory 6. In addition, the ■ address counter 5 counts the H-cycle clock from the H address counter 4 and uses the vertical blanking pulse from the input terminal 2 as a reset pulse, thereby specifying the ■ address as the read address in the memory 6. A V address signal is generated. As a result, the convergence correction data stored in the memory 6 is read out in synchronization with the raster scan of the cathode ray tube (not shown).

The read convergence correction data is converted from a digital signal to an analog signal by a digital-to-analog converter 7, and then drives a convergence yoke 10 via a low-pass filter 8 and an amplifier 9 to perform convergence correction.

When the digital convergence correction device described above is used in a television receiver or the like that performs interlace scanning, the display position of the scanning line on the cathode ray tube differs between even and odd fields, so strictly speaking, each field It is necessary to have separate convergence correction data for each.

However, having separate convergence correction data for each field doubles the memory capacity for storing the convergence correction data, and also requires field discrimination means, leading to an increase in cost. Therefore, in the conventional digital convergence correction apparatus, the same convergence correction data is used for correction for each field by utilizing the similarity between the convergence correction amounts of even and odd fields.

[Problem to be solved by the invention]

In the above conventional technology, when the raster correction amount by the digital convergence correction device becomes large, the convergence correction amount in the vertical direction on the screen becomes discontinuous because the convergence correction amount is the same for even and odd fields. There was a problem that raster unevenness occurred. Here, raster unevenness refers to a state in which the spacing between scanning lines is uneven.

Hereinafter, the causes of raster unevenness will be explained in detail using drawings.

Figure 3 is a characteristic diagram showing the amount of convergence correction for each scanning line on the screen, where the horizontal axis represents the scanning lines numbered sequentially from the top of the screen, and the vertical axis represents a certain vertical line assumed on the screen. This shows the vertical convergence correction amount at the point where the scanning lines shown on the horizontal axis intersect.

In the figure, for even fields, the convergence correction amount for even scanning line numbers (marked with a circle (A) in the figure) is used, and for odd fields, the convergence correction amount for odd scanning line numbers (marked by (A) in the figure) is shown. Δ (two) or mouth seal (1)
) is output.

In other words, even field (scanning line 0.2.4.6...)
In this case, since the corresponding convergence correction amount is stored, it is output as is as indicated by the O symbol, but in odd fields (scanning lines 1, 3, 5 degrees, etc.), the corresponding convergence correction amount is Since it is not memorized, for example, if it is scanning line 5, the convergence correction amount (○ mark) of scanning line 6 of the even field to the right of it is entered with a mark (○).
1), or the convergence correction amount (O mark) of the scanning line 4 of the even-numbered field to the left thereof is output as a Δ mark (T).

FIG. 4 is a partially enlarged explanatory diagram of the state of the raster on the screen after convergence correction.

The convergence correction amount corresponding to the scanning line of the odd field is also stored, and if the convergence correction is performed strictly, the convergence correction amount as shown in Figure 3 (A) for the even field and Figure 3 (B) for the odd field will be used. Output. In this case, the convergence correction amount changes smoothly from the top to the bottom of the screen, so the scanning lines displayed on the screen are the even field scanning line (A) and the odd field scanning line (A), as shown in Figure 4(a). (A) are arranged at equal intervals, and raster unevenness does not occur.

However, as mentioned above, to reduce memory capacity,
If only the convergence correction amount for the even field is stored in the memory and that for the odd field is not stored, the even number on one scanning line can be used instead of the convergence correction amount for the odd field as shown in Fig. 3 (a). Field convergence correction amount (Figure 3), or 1
The amount of correction for even fields below the scanning line ((1) in FIG. 3) is output.

In this case, the convergence correction amount is discontinuous from the top to the bottom of the screen, so the scanning line displayed on the screen is
), or as shown in (C), even field scanning line (a) and odd field scanning line (two), or (1)
) is unevenly spaced, causing raster unevenness.

This raster unevenness becomes a problem in terms of image quality deterioration if the amount of raster correction by the digital convergence correction device becomes large.

Furthermore, similar raster unevenness occurs when convergence correction data is stored for every other scanning line in order to reduce the memory capacity by half during sequential scanning, and convergence correction is performed using the same convergence correction data for two horizontal periods. There were problems that arose.

An object of the present invention is to use a memory that stores convergence correction data for one field during interlaced scanning, or use a memory that stores convergence correction data for every other scanning line during sequential scanning. An object of the present invention is to provide a digital convergence correction device that does not cause raster unevenness.

[Means to solve the problem]

In order to achieve the above object, the present application has taken the following means as individual inventions.

(1) Looking at the scanning lines on the cathode ray tube screen in terms of display position, divide them into two types: scanning lines at odd-numbered positions and scanning lines at even-numbered positions, one of which is the first scanning line group, and the other is the second scanning line group. scanning line group, only the convergence correction data related to the first scanning line group is stored in the digital memory, and when scanning the first scanning line group, the convergence correction data is read out from the digital memory as it is. When scanning a second scanning line group, in the one scanning period, the scanning line adjacent above the one scanning line belonging to the second scanning line group in the first scanning line group. The convergence correction data of the upper adjacent scanning line and the convergence correction data of the lower adjacent scanning line are alternately read out from the digital memory and used as the scanning period is scanned. .

(2) When scanning the second scanning line group, in the scanning period of every other frame, the second scanning line group in the first scanning line group is scanned.
The convergence correction data of the upper adjacent scanning line and the convergence correction data of the lower adjacent scanning line of the scanning line adjacent to the upper side and the scanning line adjacent to the lower side of the scanning line belonging to the scanning line group are stored in a digital memory. They are read out and used alternately.

(3) When scanning the second scanning line group, in the one scanning period, the scanning line adjacent above and below the one scanning line belonging to the second scanning line group in the first scanning line group Among the adjacent scanning lines, the convergence correction data of the upper adjacent scanning line and the convergence correction data of the lower adjacent scanning line are read out from the digital memory, their average value is calculated, and the average value is used.

(4) Looking at the scanning lines on the cathode ray tube screen in terms of display position, divide them into two types: scanning lines at odd-numbered positions and scanning lines at even-numbered positions, one of which is the first scanning line group, and the other is the second scanning line group. scanning line group, only the convergence correction data of the first scanning line group is stored in the digital memory, and the difference between the convergence correction data of the second scanning line group and that of the first scanning line group is stored in a raster format. A raster unevenness correction signal generation circuit that outputs an unevenness correction signal is prepared, and when scanning the second scanning line group, the correction signals output from the raster unevenness correction signal generation circuit are added by an addition means. .

(5) Looking at the scanning lines on the cathode ray tube screen in terms of display position, divide them into two types: scanning lines at odd-numbered positions and scanning lines at even-numbered positions, one of which is the first scanning line group, and the other is the second scanning line group. scanning line group, and only the convergence correction data of the first scanning line group is stored in the digital memory, and when reading the convergence correction data from the digital memory and making it a convergence correction output, its amplitude is An amplitude control means is provided which controls and outputs differently when scanning the scanning line group and when scanning the second scanning line group.

[Effect]

The operation will be explained in correspondence with the number of each of the above-mentioned means.

(1) Since the convergence correction data of the upper adjacent scanning line and the convergence correction data of the lower adjacent scanning line are used alternately as the scans are performed during the relevant one scanning period, the visual appearance appears as if the average correction data were used. This can be felt and the raster unevenness is visually reduced.

(2) Since the convergence correction data of the upper adjacent scanning line and that of the lower adjacent scanning line are used alternately at one frame intervals,
Although flicker may be a problem, it is effective in displays using long-lasting phosphors.

(3) Since the average value of the convergence correction data of the upper adjacent scanning line and that of the lower adjacent scanning line is calculated and used, raster unevenness can be actually reduced, not visually.

(4) Since the correction signals output from the raster unevenness correction signal generation circuit are added, raster unevenness can actually be reduced, rather than visually.

(5) When reading the convergence correction data from the digital memory and outputting the convergence correction data, when scanning the second scanning line group, the amplitude of the convergence correction data is set to the upper level in the first scanning line group when viewed from the scanning line concerned. Since the amplitude control means controls the convergence correction signal of the scanning line at the adjacent position and that of the scanning line at the adjacent position below to approximately the intermediate value, the raster unevenness is actually reduced, not visually. be able to.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention.

In FIG. 1, components (i.e., 1-10) that operate in the same way as in FIG. 2 are numbered the same as in FIG. In addition, 11 is H
This is a field discriminating section that takes in signals from the address counter 4 and (2) the blanking pulse input terminal 2 and discriminates whether the field is even or odd, and outputs a logic 0 for an even field and a logic 1 for an odd field. 12 is an AND circuit that performs an AND operation on the least significant bit of the H address counter 4 and the output of the field discriminator 11, and 13 is an address adder that digitally adds the output of the AND circuit 12 to the output of the address counter 5. .

These element parts S (field discriminator 1
1, AND circuit 5.12, and address adder 13) are the parts added according to the present invention.

FIG. 5 is a timing chart showing the operation of the configuration shown in FIG. are shown respectively.

6 and 7 are scanning line state diagrams when convergence correction is performed using the configuration shown in FIG. 1, and 61a and 61b in FIG.
are the scanning lines of the odd field, similarly, FIG. 7 71a, 71
b is a scanning line of an even field, and 72 is a scanning line of an odd field.

As can be seen from FIG. 5, the field discrimination output 51,
The AND output 53 of the lowest bit output 52 of the H address counter is added to the address counter 5 by the address adder 13. Therefore, for the vertical read address of the memory 6, in the even field, ■ the output of the address counter 5 is specified as is, and in the odd field, ■ the output of the address counter 5 as is, and ■ 1 is added to the output of the address counter 5. are output alternately at each horizontal convergence correction output point.

In other words, the convergence correction data for the odd field is the convergence correction data for the even field on the l scanning line (Fig. 3 (2)) and the convergence correction data for the even field one scanning line below (Fig. 3 (1)). It is output alternately for each convergence correction point between horizontal planes.

Therefore, as shown in FIG. 3, rasters 61(a) and 61(b) of the odd field are
) in a wavy shape centered on the center position.

According to this embodiment, since the scanning lines of odd fields are convergence-corrected in a wavy manner, raster unevenness is visually reduced and image quality is improved. Furthermore, by providing a trap filter that removes the frequency component of the wave of the scanning line of the odd field, or by designing the LPF 8 of FIG. 1 to suppress the frequency component, the scanning line of the odd field can be As shown in FIG. 3, it appears between scanning lines 71(a) and 71(b) of an even field, and vertical raster unevenness can be eliminated without becoming wavy.

Next, a second embodiment of the present invention will be described using the drawings.

FIG. 8 is a block diagram showing a second embodiment of the present invention. In FIG. 8, components that operate in the same way as those in FIG. 1 (ie, 1-11 and 13) are given the same numbers as in FIG. In addition, 14 indicates that every time the output of the field discriminator 11 falls,
A frame counter that repeats 0 output and 1 output, 15 is the output of the frame counter 14 and A of the field discriminator 11
This is an AND circuit that performs an ND operation.

9 is a timing chart showing the circuit operation of FIG. 8, and 91, 92, and 93 are the field discriminator 11, frame counter 14, and AN in FIG.
The output of the D circuit 15 is shown.

Moreover, FIG. 10 shows the scanning line state when convergence correction is performed using the configuration of FIG. 8, and 101a 1
01b indicates a scanning line of an even field, and 102.103 indicates a scanning line of an odd field.

As can be seen from FIG. 9, the field discrimination output 91,
The AND output 93 of the frame count output 92 is added to the address counter 5 by the address adder 13. Therefore, for the vertical read address of the memory 6, in an even field, ■ the output of the address counter 5 is specified as is, and in an odd field, the output of the V address counter 5 as is, and ■ 1 is added to the output of the address cursor 5. are output alternately every l frames.

In other words, the convergence correction data for the odd field is the convergence correction data for the even field on one scanning line (Fig. 3 (2)) and the convergence correction data for the even field one scanning line below (Fig. 3 (1)). Outputs alternately every frame.

Therefore, the scanning lines of odd fields are 102.
As shown in 103, even field raster 101 (
Centering on the center position of a) and 1ot(b), they appear alternately above and below every l frame.

According to this embodiment, convergence correction is performed alternately upward and downward on the scanning lines of odd-numbered fields for each frame, which has the effect of apparently reducing raster unevenness in the vertical direction and improving image quality.

Next, a third embodiment of the present invention will be described using the drawings.

FIG. 11 is a block diagram showing a third embodiment of the present invention. In FIG. 11, components that operate in the same way as those in FIG. 1 (ie, 1 to 11) are given the same numbers as in FIG. In addition, 16 others
is the convergence correction data output from the memory.
An IH delay circuit that stores horizontal period and outputs convergence correction data delayed by one horizontal period; 17 is an average calculation circuit that calculates the average value of the output of the memory 6 and the output of the IH delay circuit 16 by digital processing; 18 is a field discrimination circuit; Part 1
If the output of 1 is logic O, that is, in an even field, the memory 6, +7) output is selected, and if the output of the field discriminator 11 is logic 1, that is, in an odd field, the output of the average calculation circuit 17 is selected. This is a selection circuit that selects.

Assume now that in the case of an even field, the selection circuit 18 selects the output of the memory 6, thereby outputting the convergence correction amount shown in FIG. 3(A).

Next, in the odd field, the convergence correction data for the even field one scanning line up from the IH delay circuit 16 (see FIG. 3) is sent from the memory 6, and the convergence correction data for the even field one scanning line below (see FIG. 1)) are respectively input to the average calculation circuit 17, and as a result, the average calculation circuit 17 outputs the average value of each correction amount of (1) and (1) in FIG. Convergence correction is performed via 18. As a result, the scanning line state becomes the state shown in FIG. 4(a).

According to this embodiment, since the convergence correction is performed by calculating the average value of the convergence correction data of the even fields above and below one scanning line as the convergence correction data of the odd field, the convergence correction amount in the vertical direction becomes continuous. , raster unevenness does not occur.

Next, a fourth embodiment will be described in which the IH delay circuit of the third embodiment shown in FIG. 11 is removed and the same operation can be performed.

FIG. 12 is a block diagram showing a fourth embodiment of the present invention. In FIG. 12, components that operate in the same way as those in FIG. 11 (i.e., 1 to 11° 17.18) are given the same numbers as in FIG. 11. In addition, 19 is a V address adder that adds the least significant bit of the H address counter 4 to the output of the V address counter 5, 20 is a latch that holds data in the memory 6, and 21
is a latch that holds the output of the selection circuit for one day.

Now, the address adder 19 contains the H address counter 4.
Since the least significant bit of is added, from memory 6, ■
The convergence correction data of the address obtained by adding 1 to the output of the address counter 5 and the convergence correction data of the address specified by the address counter 5 are alternately output. First, ■Convergence correction data of the address obtained by adding 1 to the output of address counter 5, that is, IH
The same data as the delayed convergence correction data is held in the latch 20.

Next, ■When the memory 6 outputs the convergence correction data of the address specified by the address counter 5, the average calculation circuit 17 performs the average calculation, and the result is latched to the latch 21.
to hold.

According to this embodiment, the same effect as in the third embodiment can be achieved without using an IH delay circuit.

Next, a fifth embodiment of the present invention will be described with reference to FIG. 13, in which raster unevenness is corrected using a raster unevenness correction signal generating means.

FIG. 13 is a block diagram showing a fifth embodiment of the present invention. In FIG. 13, components that operate in the same way as those in FIG. 1 (ie, 1 to 11) are given the same numbers as in FIG. 1. In addition, 22 is a raster unevenness correction signal with an L field period synchronized with the raster scan necessary for correcting raster unevenness from the signals input from the H blanking pulse input terminal 1 and the blanking pulse input terminal 2. This is a raster unevenness correction signal generation circuit that generates a raster unevenness correction signal, and the means for generating the raster unevenness correction signal is the output of the digital-to-analog converter 7 of the conventional digital convergence correction device shown in FIG.
A circuit similar to an analog convergence circuit that generates signals in an analog manner can be considered.

Further, 23 is an analog switch that transmits the output of the raster unevenness correction waveform generation circuit 22 to an adder 24, which will be described later, only when the field discrimination output is logic 1, and 24 is a digital switch.
This is an adder that adds the convergence correction signal output from the analog converter 7 and the output of the analog switch 23.

Assume now that the digital-to-analog converter 7 outputs convergence correction signals as shown in FIG. 3(A) for even fields and (2) for odd fields. In addition, the raster unevenness correction waveform generation circuit 22 outputs convergence correction data (see FIG.
It is assumed that the difference between the convergence correction data of the odd field (FIG. 3(a)) that does not cause raster unevenness is output as a raster unevenness correction signal. This raster unevenness correction signal is sent to the analog switch 23 and the adder 2.
4, it is added only to odd fields, and as a result, in even fields it is added as shown in Figure 3 (A), and in odd fields it is added as (A).
b) The convergence correction amount is the convergence yoke 1
Output from 0. As a result, the screen state is as shown in Figure 4(a).
Therefore, raster unevenness can be eliminated.

According to this embodiment, in addition to being able to eliminate raster unevenness in the vertical direction, raster unevenness that occurs when interlaced scanning is not performed correctly in the deflection circuit can be eliminated at the same time as raster unevenness that occurs during digital convergence correction. be able to.

Furthermore, in this embodiment, the raster unevenness correction signal generation circuit 22 uses the H address counter instead of generating signals using the signals input from the H blanking pulse input terminal 1 and the blanking pulse input terminal 2. 4. (2) The output of the address counter 5 may be used to generate a signal.

In addition, in this embodiment, when the raster unevenness correction signal generation circuit 22 generates a raster unevenness correction signal with a period of one frame synchronized with the raster scan, the output of the raster unevenness correction waveform generation circuit 22 is directly added to the adder. In addition to 24, raster unevenness can be corrected. In this case, the field discrimination section 11 and analog switch 23 can be deleted.

Next, a sixth embodiment of the present invention in which raster unevenness is corrected by controlling the amplitude of a convergence correction signal will be described with reference to the drawings.

FIG. 14 is a block diagram showing a sixth embodiment of the present invention. In FIG. 14, components (i.e., 1 to 11) that operate in the same way as those in FIG. 1 are given the same numbers as in FIG. In addition, 25 is an EXOR circuit that performs an exclusive OR operation of the most significant bit of the address counter 5 and the output of the field discriminator 11, and 26 is OFF when the output of the EXOR circuit 25 is logic O.
, analog switch that turns on when logic is 1, 27°28
．． 29 are resistors R1, R2, and R3, respectively, and 26 to
The amplitude control section 30 is composed of 29 components.

Further, FIG. 15 is a diagram showing the vertical convergence correction output. In Figure 15, the horizontal axis is the vertical position of the screen,
The vertical axis indicates the convergence correction amount. Also, 15
1,153 are convergence correction amounts for even fields at the top of the screen and at the bottom of the screen, respectively, and 152.154 are convergence correction amounts for odd fields at the top and bottom of the screen, respectively.

FIG. 15A is a general explanatory diagram of vertical convergence distortion on a screen, and corresponds to FIG. 15.

In FIG. 15A, the vertical axis of the screen corresponds to the 1V period, and the horizontal axis corresponds to the IH period. In the raster at the top of the screen, generally positive distortion (correction amount AU) occurs near both ends of the IH period, and negative distortion (correction amount JL) occurs near the center. The same goes for the raster at the bottom of the screen. No distortion occurs in the raster at the center of the screen (center of the IV period) and is zero.

The meaning of FIG. 15 will be better understood if FIG. 15 is referred to again while keeping in mind the general tendency of vertical convergence distortion.

FIG. 16 is a timing chart showing the operation of the configuration shown in FIG.
The field discriminator 11, the most significant bit of the address counter 5, and the outputs of the EXOR circuit 25 are shown in the figure.

First, the principle of a method for eliminating raster unevenness using an amplitude control method will be explained.

The term "amplitude control" here has the following meaning. That is, in FIG. 15, the required correction amount 151 for the raster in the even field at the top of the screen has a pulse-like waveform, and the required correction amount 152 for the raster in the odd-numbered field at the top of the screen similarly has a pulse-like waveform. Although they are similar, 151 is larger than 152 overall.

Also, at the bottom of the screen, the correction amount 153 for the even field raster has an inverted pulse-like waveform.
The required correction amount 154 for the odd field raster similarly has an inverted pulse-like waveform and is similar, but this time, 153 is smaller than 154 overall.

Therefore, once the waveform of the required correction amount 151 for the even field raster at the top of the screen is created, the waveform of the required correction amount 152 can be created by controlling the amplitude of this waveform. Similarly, once the waveform of the required correction amount 153 for the even field raster at the bottom of the screen is created, the waveform of the required correction amount 154 can be created by controlling the amplitude of this waveform. This is what amplitude control means.

Now, since the output of the conventional digital convergence correction device having the configuration shown in FIG. 2 has only convergence correction data for even fields, instead of outputting convergence correction data 152 and 154 for odd fields, Even field convergence correction correction data 151 and 153 are output. For this reason,
The amount of correction in the vertical direction becomes discontinuous, causing raster unevenness.

However, from FIG. 15, the convergence correction data 152 of the odd field above the center of the screen is the same as the convergence correction data 152 of the even field, as already mentioned.
It can be seen that it can be approximated as a smaller amplitude of 1.

Furthermore, the convergence correction data 154 for odd fields below the center of the screen can be approximated by increasing the amplitude of the convergence correction data 153 for even fields.

In order to perform the above amplitude control, it is necessary to switch between three types of gains in the amplitude control section. Therefore, if you lower the gain of the even field convergence correction signal below the center of the screen and leave the gain of the odd field convergence correction signal unchanged, the gain can be reduced to 2.
A similar raster unevenness reduction effect can be obtained by switching the type.

Next, a configuration for performing the above operation will be explained. The field discriminator 11 outputs a signal 161 which is a logic 0 for even fields and a logic 1 for odd fields. Also, from the most significant bit of the address counter 5, a signal 162 is output which becomes logic 0 above the center of the screen and becomes logic 1 below the center of the screen. For this reason, the EXOR circuit 25
is a logical 0 above the center of the screen for even fields,
A signal 163 is output that becomes logic 1 at the bottom, logic 1 above the center of the screen, and logic 0 below the center of the screen in odd fields.

Furthermore, when the output of the EXORu path is logic 0, the analog switch 26 is turned off, so that it is LPF'd. EXO
When the output of the R circuit is logic 1, the analog switch 26 is turned on, so the output of LPFB becomes R1+(R2//R3) and is input to AMP9, so the gain is smaller than when the output of the EXOR circuit is logic 0. can do.

Therefore, above the center of the screen, the convergence correction amount for odd fields is smaller than that for even fields, and below the center of the screen, the amount of convergence correction for even fields is smaller than that for odd fields. As a result, the amount of correction in the vertical direction becomes continuous, and raster unevenness can be reduced.

According to this embodiment, raster unevenness can be reduced with a simple circuit. Further, in this embodiment, if the amplitude is continuously modulated, raster unevenness can be corrected more accurately.

It goes without saying that in all of the embodiments described above, a configuration in which even and odd fields are considered reversely can be realized.

Note that all of the above embodiments are examples in which interlaced scanning is performed, but even when convergence correction data is stored for every other scanning line during sequential scanning and convergence correction is performed, the field discrimination section A similar effect can be obtained by using the output of the least significant bit of the vertical address counter 5 instead of the output.

〔Effect of the invention〕

According to the present invention, during interlaced scanning, a memory that stores convergence correction data for one field is used, or during sequential scanning, a memory that stores convergence correction data for every other scan is used. Furthermore, since raster unevenness on the screen can be eliminated or reduced, the capacity of expensive memory can be halved and costs can be reduced, and image quality can be improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a block diagram showing a conventional example of a digital convergence correction device, and Fig. 3 is an explanation of the relationship between the vertical scanning line position and the convergence correction amount thereto. Fig. 4 is an explanatory diagram showing the raster state after convergence correction, Fig. 5 is a timing chart showing the signal timing of the main part in Fig. 1, and Fig. 6 is raster unevenness improvement by the embodiment of Fig. 1. FIG. 7 is an explanatory diagram showing the effect of improving raster unevenness when a low-pass filter is added to the embodiment of FIG. 1. FIG. 8 is a block diagram showing another embodiment of the present invention. 9 is a timing chart showing the signal timing of the main part in FIG. 8, FIG. 10 is an explanatory diagram showing the effect of improving raster unevenness by the embodiment of FIG. 8, and FIGS. FIG. 15 is a block diagram showing the embodiment of FIG. 14, and FIG.
Figure 5A is an explanatory diagram showing convergence distortion on the screen corresponding to the convergence correction waveform shown in Figure 15;
This figure is a timing chart showing the signal timing of the main part in FIG. 14. Explanation of symbols 4...H address counter, 5...■Address counter, 6...Digital memory, 7...Digital/analog converter, 11...Field discriminator, 12
゜15...AND circuit, 13...■Address adder, 14...Frame counter, 16...IH delay circuit, 17...Average calculation circuit, 22...Raster unevenness correction signal generator , 30... Amplitude Control Department Agent Patent Attorney Akio Namiki Figures (a) (b) (C) O- Figure Figure Figure Figure 10 Figure 1b Figure 15A Figure 15 Figure 16 Field ramie J? l'l soil 161~EXORIEW
I 163～-ri1--2 [-11111111]----"-□〇 Temple M

Claims (1)

[Claims] 1. Convergence correction data at each lattice point of a lattice pattern arbitrarily set on a cathode ray tube screen using a raster scan method, with scanning lines as horizontal stripes and virtual lines perpendicular to the scanning lines as vertical stripes. a digital memory for determining and storing the address in advance, an address signal generating means for generating an address signal specifying a horizontal address and a vertical address of the memory in synchronization with raster scanning on the cathode ray tube screen, and the address signal generating means. a digital/analog converter that reads convergence correction data from the digital memory in accordance with an address signal generated by the means, converts it into digital/analog, and outputs it;
In the digital convergence correction device, the scanning lines on the cathode ray tube screen are divided into two types, scanning lines at odd-numbered positions and scanning lines at even-numbered positions, in terms of display position, and one of them is designated as a first scanning line. group, and the other one is a second scanning line group, and only convergence correction data related to the first scanning line group is stored in the digital memory, and when scanning the first scanning line group, the address signal is When reading the convergence correction data from the digital memory according to the address signal generated by the generating means and inputting it to the digital/analog converter to scan the second scanning line group, the first Among the scanning line groups, select the upper and lower scanning lines of the first scanning line that belong to the second scanning line group, and select the convergence correction data related to the upper scanning line and the lower scanning line. The present invention is characterized by comprising convergence correction data manipulating means for alternately reading out convergence correction data related to adjacent scanning lines from the digital memory and inputting them to the digital/analog converter as scanning occurs during the one scanning period. Digital convergence correction device. 2. In the digital convergence correction device according to claim 1, when the convergence correction data manipulation means scans the second scanning line group, the first scanning line group The convergence correction data related to the upper adjacent scanning line and the lower adjacent scanning line among the scanning line adjacent to the upper side and the scanning line adjacent to the lower side of the first scanning line belonging to the second scanning line group. A digital convergence correction device characterized in that it comprises means for alternately reading out related convergence correction data from said digital memory and inputting it to said digital/analog converter. 3. In the digital convergence correction device according to claim 1, when the convergence correction data manipulation means scans the second scanning line group, the first scanning line group in the first scanning line group is Convergence correction data related to the upper adjacent scanning line and convergence correction data related to the lower adjacent scanning line among the scanning line adjacent to the upper side and the scanning line adjacent to the lower side of the 1 scanning line belonging to the scanning line group 2. A digital convergence correction device characterized by comprising means for reading out from the digital memory, calculating an average value thereof, and inputting the average value to the digital/analog converter. 4. Obtain and store in advance convergence correction data at each lattice point of a lattice pattern arbitrarily set on a cathode ray tube screen using the raster scan method, with scanning lines as horizontal stripes and virtual lines perpendicular to the scanning lines as vertical stripes. a digital memory; an address signal generating means for generating an address signal specifying a horizontal address and a vertical address of the memory in synchronization with raster scanning on the cathode ray tube screen; and an address signal generated by the address signal generating means. a digital/analog converter that reads the convergence correction data from the digital memory according to the method, converts it into digital/analog, and outputs it;
In the digital convergence correction device, the scanning lines on the cathode ray tube screen are divided into two types, scanning lines at odd-numbered positions and scanning lines at even-numbered positions, in terms of display position, and one of them is designated as a first scanning line. one scanning line group, and the other one is a second scanning line group, and only the convergence correction data related to the first scanning line group is stored in the digital memory, and the convergence correction data related to the second scanning line group and the second scanning line group are stored in the digital memory. A raster unevenness correction signal generating circuit is prepared which outputs the difference related to the first scanning line group as a raster unevenness correction signal, and when scanning the first scanning line group, the address signal generating means generates a raster unevenness correction signal. The convergence correction data is read from the digital memory according to the address signal and inputted to the digital/analog converter, and the output is used as the convergence correction output. When scanning the second scanning line group, the first scanning line group an addition of adding a correction signal output from the raster unevenness correction signal generation circuit to the output from the digital/analog converter which reads and inputs convergence correction data from the digital memory when scanning, and outputs the result as a convergence correction output. A digital convergence correction device characterized by comprising means. 5. Obtain and store in advance convergence correction data at each lattice point of a lattice pattern arbitrarily set on a cathode ray tube screen using the raster scan method, with scanning lines as horizontal stripes and virtual lines perpendicular to the scanning lines as vertical stripes. a digital memory; an address signal generating means for generating an address signal specifying a horizontal address and a vertical address of the memory in synchronization with raster scanning on the cathode ray tube screen; and an address signal generated by the address signal generating means. a digital/analog converter that reads the convergence correction data from the digital memory according to the method, converts it into digital/analog, and outputs it;
In the digital convergence correction device, the scanning lines on the cathode ray tube screen are divided into two types, scanning lines at odd-numbered positions and scanning lines at even-numbered positions, in terms of display position, and one of them is designated as a first scanning line. one scanning line group, and the other one is a second scanning line group, and only convergence correction data related to the first scanning line group is stored in the digital memory; When reading the convergence correction data from the digital/analog converter and using the output as the convergence correction output,
An amplitude control means receives the output of the digital/analog converter, controls the amplitude according to whether the first scanning line group or the second scanning line group is scanned, and outputs the amplitude. A digital convergence correction device characterized in that the controlled output is used as a convergence correction output.