JP2778016B2 - Digital convergence circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention converts correction data necessary for convergence correction into a weighting coefficient that is multiplied by a basic correction wave constituting a composite wave in which correction data is stippled. The present invention relates to a digital convergence circuit for storing. [Prior Art] A projection television receiver that combines images projected from three monochromatic projection tubes corresponding to three primary colors on a screen is compared with a direct-view television receiver that looks directly at a screen on the cathode ray tube. In addition, it is necessary to correct the convergence of the scanning lines by adjusting the convergence of the scanning line, which is easily affected by the terrestrial magnetism and occurs when the direction of the projection tube is changed or the posture is adjusted. The digital convergence circuit 1 shown in FIG.
The present invention is applied to a projection type television receiver 4 for projecting an image from the RGB single-color projection tubes 2r, 2g, 2b to a screen 3 in front, and is provided for each of the projection tubes 2r, 2g, 2b. The convergence coil (not shown) is built in the defocus correction circuit 5. The convergence shift correction circuit 5 is connected to a storage circuit 6 for storing correction data necessary for convergence correction already collected for each sample point divided in a matrix on the screen 3. The correction data read from the storage circuit 6 in synchronization with the scanning is supplied to the focus shift correction circuit 5. [Problems to be Solved by the Invention] The conventional digital convergence circuit 1 is used for adjusting a convergence adjustment for collecting correction data necessary for convergence correction on a screen 3 such as a cross hatch pattern or a dot pattern. An image is projected, and at that time, the optimum correction data must be obtained through trial and error while changing the correction data given to the defocus correction circuit 5 for each sample point. Therefore, if the number of sample points is increased, The longer the time, the longer the work time and the larger the capacity of the storage circuit 6 are unavoidable.
In a projector in which the deflection mode is automatically switched according to the horizontal deflection frequency of ~ 41 kHz, the filtering characteristics of the convergence coil and its driving circuit and the characteristics of the deflection circuit change according to the horizontal deflection frequency and are stored in the storage circuit 6. Since the correction data to be changed is different, there is a problem that the storage circuit 6 must be further increased in capacity. Japanese Patent Application Laid-Open No. Sho 60-130288, "Digital Convergence Device" has a correction data storage circuit (frame memory) for storing correction data for each sample point and performs convergence correction based on the correction data. Is disclosed. However, this configuration has a configuration in which all convergence correction data for each sample point that divides one screen in a matrix is stored in the correction data storage circuit. Therefore, the correction data storage circuit requires a considerable storage capacity. Further, when the number of scanning lines increases or decreases according to the deflection frequency, the number of scanning lines between sample points set in advance is determined, and a coefficient for each scanning line between the sample points is multiplied to obtain the number of scanning lines on the screen. It is said that convergence correction can be performed with high accuracy without increasing the distance, but the correction data collected in a specific deflection mode cannot respond to other deflection modes only by linear conversion. After all, from the viewpoint of maintenance, correction data must be stored for each deflection mode.In that case, the correction data storage circuit requires a very large storage capacity, and the deflection frequency that can be actually handled is naturally limited. It had problems such as being done. Further, Japanese Patent Application Laid-Open No. Sho 57-140091, "Convergence control device", discloses a device in which correction data is constituted by a plurality of basic correction waves and coefficients. When performing the dynamic convergence adjustment, the first and second convergence adjustments using a horizontal or vertical period parabola waveform (Y = X ² ) are applied to the center and both ends on one axis of the screen. A convergence adjustment is performed, and then a two-stage convergence adjustment is performed in another part on the same one axis by a secondary convergence adjustment in which the center part and the image edge part become zero. The purpose of the present invention is to eliminate mutual interference between the first and second convergence adjustments. However, the residual convergence deviation that cannot be completely adjusted by the first-order convergence adjustment needs to be corrected using a special function waveform, for example, Y = X ³ −X or Y = X ⁴ −X ^2. Thus, the complexity of the circuit configuration cannot be avoided, for example, a high-order arithmetic circuit for the distance X is required. In addition, it is necessary to use separate composite waves Cc (X) for the right half and the left half of the screen for defining the convergence correction data, and Cc (X) = K + K ₁ (X ³ −X) + K ₂ (X ⁴ −X ² ) + K ₃ X ² (X ≦ 0) Cc (X) = K + K ₁ (X ³ −X) + K ₂ (X ⁴ −X ² ) + K ₄ X ² (X> 0) is required It is. Also, as is clear from these two equations, weighting coefficients K, K ₁ , K ₄ , K ₁ , which define four kinds of basic correction waves X ⁰ , X ² , X ³ −X, X ⁴ −X ² . of K _2, for K _1, K ₂ required in the second-order convergence adjustment is not present priority, so that if the variable either must change the other weighting coefficients, independently of one another It is almost impossible to determine each independently, the coefficients K ₁ , K
_The convergence adjustment takes time because the interdependency between the _two is large, and the weighting factor determined first
Whether or not the weighting coefficients K ₁ and K ₂ other than K, K ₃ and K ₄ are the optimal values also has a problem such as poor confirmation. Also, if required further convergence adjustment of higher order has been that it is possible to use ^{X 5 -X 3, X 6 -X} 4 as the basic correction wave, these basic correction wave Second
When used for the next convergence adjustment, the mutual interference between the weighting coefficients described above is inevitably further complicated. However, in such a case, at least one or more basic correction waves used for the secondary convergence adjustment are not all treated equally, but, for example, a plurality of basic correction waves are assigned priorities and used. The problem can be overcome by performing several steps of correction, such as correcting the convergence deviation that the wave could not completely correct with the basic correction wave of lower priority, but it is possible to solve the problem. No disclosure was made of the determination of the completion of the correction, and the lack of convergence deviation elimination was lacking.
Furthermore, the weighting coefficient finally determined differs depending on the deflection frequency, but is not stored and stored in the memory. Therefore, when the deflection frequency is switched, the convergence adjustment is performed each time. It had to be done from the beginning and had the problem of being very inefficient. Means for Solving the Problems The present invention has solved the above-mentioned problems, and has a convergence shift correction circuit for performing convergence correction based on correction data, and a horizontal scanning cycle prepared with priorities assigned in advance. Or a finite number of sample points for dividing the screen into a matrix by creating the correction data by multiplying a basic correction wave used according to the priority by an appropriate weighting coefficient from among a plurality of basic correction waves in a vertical scanning cycle. A weighting coefficient for minimizing the convergence deviation with respect to the largest number is optimally determined through trial and error, and the convergence deviation that could not be corrected in the correction data is multiplied by an appropriate weighting coefficient to the next priority basic correction wave. Correct with the correction data obtained,
When the convergence adjustment is performed by using the required number of basic correction waves according to the priority order until the convergence deviation settles within the predetermined allowable range at all of the sample points, the basic number of the required number A coefficient storage circuit that stores the weighting coefficient optimally determined for each correction wave for each deflection mode in which the horizontal deflection frequency or the vertical deflection frequency is different,
A central processing unit that reads a weighting coefficient from the coefficient storage circuit according to the deflection mode during the convergence correction, multiplies the corresponding basic correction wave, and sums the multiplication results to calculate correction data; A correction data storage circuit for storing correction data calculated at the time of correction in units of a screen; and control means for reading out correction data from the correction data storage circuit in synchronization with deflection scanning and supplying the correction data to the focus shift correction circuit. It is characterized by the following. [Operation] According to the present invention, the correction data for correcting the convergence shift is obtained by adding a plurality of basic correction waves prepared in advance with a priority order of the horizontal scanning cycle or the vertical scanning cycle to a combined wave weighted and added. Taking the above as stippling data, the correction data is created by multiplying the basic correction wave used according to the priority by an appropriate weighting coefficient, and the defocusing of the maximum number of a finite number of sample points that divides the screen into a matrix. Is determined through trial and error, and the convergence deviation that could not be corrected with the correction data is corrected using correction data obtained by multiplying the basic correction wave of the next priority by an appropriate weighting coefficient. After performing the adjustment, only the weighting coefficient of each basic correction wave constituting the composite wave of the basic correction wave with the weighting coefficient finally obtained is By storing the coefficient in the coefficient storage circuit for each deflection mode in which the horizontal deflection frequency or the vertical deflection frequency is different as a value unique to the correction object, the time required for the convergence adjustment can be reduced, and the storage circuit for the data required for the convergence correction can be stored. The capacity can be saved. Example An example of the present invention will be described below with reference to FIGS. FIG. 1 is a circuit diagram showing an embodiment of a digital convergence circuit of the present invention, and FIGS.
(G) is a waveform diagram showing each waveform example of a basic correction wave constituting a composite wave in which correction data is stippled. In FIG. 1, a digital convergence circuit 11 varies a weighting coefficient by which a basic correction wave in a horizontal scanning period or a vertical scanning period is multiplied for each sample point which divides a screen into a matrix, and synthesizes the basic correction wave. At the time of convergence adjustment performed while adjusting the correction data stippled on the obtained composite wave, a coefficient storage circuit 12 for storing a weighting coefficient corresponding to the finally adjusted correction data for each deflection mode.
Having. The weighting coefficients stored in the coefficient storage circuit 12 are read by the central processing unit 14 at the time of convergence correction, multiplied by the corresponding basic correction waves, and converted into correction data by summing up the multiplication results. 16 is
A ROM that stores software that defines an operation program of the central processing unit. Apart from the coefficient storage circuit 12 and the ROM 16, the central processing unit 14 is connected to a correction data storage circuit 13 for storing correction data for one screen, and the correction data calculated by the central processing unit 14 at the time of convergence correction is stored. It is stored for each screen. The correction data read from the correction data storage circuit 13 is latched by a latch circuit 17, supplied to a DA converter 18 and converted into an analog signal, and then passed through a low-pass filtering circuit 19 for aliasing distortion removal. And is supplied to the focusing error correction circuit 5. At the time of the convergence correction, the timing generation circuit 20, the phase locked loop circuit 21, and the address generation circuit 15 serve as control means for reading out the correction data from the correction data storage circuit 13 in synchronization with the deflection scanning and supplying the correction data to the focus shift correction circuit 5. Is provided. The timing generation circuit 20 receives a vertical synchronizing signal accompanying the video signal and generates a timing pulse for determining a read timing, while the phase locked loop circuit 21 addresses the frequency-multiplied signal phase-locked to the horizontal synchronizing signal. Generated as an operation clock required for The address generation circuit 15 specifies an address required for reading out correction data from the correction data storage circuit 13 based on the timing pulse supplied from the timing generation circuit 20 and the operation clock supplied from the phase locked loop circuit 21. Generate an address signal. By the way, in this embodiment, the correction data for the convergence correction is defined by a composite wave in which seven types of basic correction waves are weighted and added. Therefore, a weighting coefficient by which each basic correction wave is multiplied is determined by a convergence coefficient. It must be absorbed as data unique to the correction target. The seven types of basic correction waves are, as shown in FIGS. 2A to 2G, a parabolic waveform wave f of a horizontal scanning period and a vertical scanning period.
₁ (x), f ₂ (x) and sawtooth waveforms f ₃ (x), f ₄ (x) and a parabolic waveform f ₅ (x) in a horizontal scanning cycle amplitude-modulated by a sawtooth waveform in a vertical scanning cycle. ) And the sawtooth waveform f ₆ (x),
Further, the waveform is a sawtooth waveform f ₇ (x) of a horizontal scanning cycle amplitude-modulated by a parabolic waveform of a vertical scanning cycle, and each subscript corresponds to a priority that defines a use order at the time of convergence adjustment. 1 convergence correction amount Y at the distance x from the scan start end of the scan line of the line, Y = ΣKjfj (x) = K 1 f 1 (x) + K 2 f 2 (x) ·· + K 7 f 7 (x) Is defined by In the above equation, the weighting factor K ₁ ~K ₇ is a value that is trial and error determined in a particular deflection mode upon convergence adjustment can be determined according to the following procedure. First, the deflection mode is fixed, and the first priority basic correction wave f ₁ (x), which has the most influence on the convergence correction,
To determine the weighting coefficients K _1, and visually observing the defocusing on the screen while varying the value of K _1. In this case, the central processing unit 14, with respect to the weighting factor K ₁ which is provisionally set, calculates the correction data at each point obtained by dividing the screen into matrix form, and stores it in the correction data storage circuit 13. Then, the correction data storage circuit 13 reads out the stored correction data in synchronization with the horizontal deflection scanning, and supplies the data to the focusing deviation correction circuit 5 sequentially. On the other hand, coordinator for adjusting the convergence, while varying the values of weighting coefficients K _1, the values of the weighting coefficients K ₁ to defocus the finite number of sample points that divides the screen into a matrix seems fewest, The coefficient is stored in the coefficient storage circuit 12. Next, for the second-priority basic correction wave f ₂ (x) which affects the convergence correction amount after the first-priority basic correction wave f ₁ (x), the weighting factor K ₂ Determine the value. Thus, while the thrust adjustment range gradually, while using the basic correction wave in accordance with the priority until it can be determined that could defocusing solved to determine the optimum value also weights K ₃ ~K ₇ remain as needed.
The weighting coefficients K _{1 to} K ₇ thus determined are all stored in the coefficient storage circuit 12 upon completion of the adjustment. Therefore,
For example, if the convergence deviation is eliminated by the convergence adjustment up to the third priority basic correction wave f ₃ (x), the values of the weighting coefficients K _{4 to} K ₇ are all set to “0”, but the coefficient storage is performed. completed at the time the memory is completed weighting coefficient K ₁ ~K ₇ to the circuit 12, all of the correction data required for convergence correction in a particular deflection mode is stored in the correction data storage circuit 13, also convergence adjusting simultaneously . Also,
Once the convergence adjustment is completed, unless the convergence correction is performed under the same conditions,
The storage contents of the correction data storage circuit 13 can be deleted. This is because the data required for convergence correction are stored in the coefficient correction circuit 12 by changing the shape to weight coefficient K ₁ ~K _7, the weighting coefficient K ₁ ~ from the next to be read from the coefficient storage circuit 12 correction data obtained by multiplying the K ₇ each fundamental correction wave is written in a predetermined address of the correction data storage circuit 13, because the convergence correction is performed based on the correction data written here. Further, since the coefficient storage circuit 12 stores only the weighting coefficient by which the basic correction wave is multiplied in a specific deflection mode, its storage capacity has a sufficient margin. Therefore, the deflection mode (for example, horizontal deflection frequency) for the same model Can also be stored separately for each deflection mode. In this case, the correction data read from the coefficient storage circuit 12 corresponding to the deflection mode is written to the correction data storage circuit 13 each time, and the correction data storage circuit 13 has a sufficient function as a buffer memory. Can be demonstrated. As described above, according to the digital convergence circuit 11, the correction data for correcting the convergence shift is provided with a plurality of basic correction waves f ₁ (p. x) to f ₇ (x) are regarded as the stippling data on the synthesized wave to which the weighted addition is performed, and an appropriate weighting coefficient is assigned to the basic correction wave used according to the priority order.
K _{1 to} K ₇ are multiplied to generate correction data Kjfj (x), and a weighting coefficient for minimizing a focus shift is determined through trial and error for a maximum number of a finite number of sample points that divide the screen into a matrix. Further, the convergence adjustment for correcting the convergence shift that could not be completely corrected by the correction data with the correction data obtained by multiplying the basic correction wave of the next priority by an appropriate weighting coefficient is performed, and with the weighting coefficient finally obtained. Only the weighting coefficients K _{1 to} K ₇ of the respective basic correction waves constituting the composite wave of the basic correction waves are stored in the coefficient storage circuit 12 as values unique to the correction object for each deflection mode having different horizontal deflection frequency or vertical deflection frequency. be able to.
For this reason, unlike the conventional convergence circuit in which the correction data required for the convergence correction is stored in the storage circuit for every sample point one by one, the storage capacity of the coefficient storage circuit 12 can be significantly reduced, and the basic correction wave can also be reduced. In the case where the coefficient is determined sequentially from the basic correction wave having a high influence on the correction data, the convergence correction can be performed using the minimum basic correction wave without using up all the basic correction waves prepared in advance. There is also. Also, unlike the high-order identification method in which the correction data is forcibly applied to a complex synthesized wave composed of high-order arithmetic expressions prepared in advance, optimal convergence correction suitable for the characteristics of the correction target is possible, and the Convergence adjustment can be performed very easily as compared with the method of determining correction data for every point. Furthermore, it is only necessary to determine one weighting coefficient for one screen for each basic correction wave through trial and error without using a complicated method of changing the weighting coefficient for each scanning line for the basic correction wave. Specifically, it is only necessary to store only several types of weighting coefficients in the coefficient storage circuit 12. On the other hand, at the time of convergence correction, the corresponding basic correction waves f ₁ (x) to f ₇ (x) are multiplied by the weighting coefficients K _{1 to} K ₇ read from the coefficient storage circuit 12 in accordance with the deflection mode, and the multiplication results are added. To calculate the correction data ΣKjfj (x), and store the calculated correction data in the correction data storage circuit 13 for each screen.
In order to supply the correction data read out in synchronism with the deflection scanning to the defocus correction circuit 5, the correction data storage circuit 13 is only required to store the correction data for one screen in a specific deflection mode. Function only. Therefore, the correction data storage circuit 13 can be released from the duty of semi-permanently storing the correction data unique to each display to be subjected to the convergence correction, and the display of the same model differs depending on the deflection mode. By changing the correction data to a weighting coefficient for multiplying the basic correction wave, the correction data can be stored in the coefficient storage circuit 12 with less burden, and therefore, a single coefficient storage circuit 12 can have a weight corresponding to a plurality of deflection modes. Coefficients can be stored. In the above embodiment, the projection type television receiver is described as an example, but the convergence correction target may be a direct-view type television receiver which directly looks at an image projected on a picture tube. Good. The number of types of basic correction waves is not limited to seven, and may be any type as long as there are at least two or more types of basic correction waves constituting a composite wave serving as a core of correction data. [Effects of the Invention] As described above, according to the present invention, a plurality of basic corrections prepared by assigning correction data for correcting a convergence shift to a horizontal scanning period or a vertical scanning period in advance are prepared. The waves are regarded as stippling data on the synthesized wave to which the weights are added, and the correction data is created by multiplying the basic correction wave used according to the priority by an appropriate weighting coefficient, and a finite number of screens are divided into a matrix. A weighting coefficient for minimizing the convergence deviation for the maximum number of sample points is determined through trial and error.Furthermore, the convergence deviation that could not be completely corrected in the correction data is multiplied by the appropriate weighting coefficient to the next priority basic correction wave. Each basic correction wave which is subjected to convergence adjustment to be corrected with the obtained correction data and constitutes a composite wave of the finally obtained basic correction waves with weighting coefficients Is stored in the coefficient storage circuit for each deflection mode having a different horizontal deflection frequency or vertical deflection frequency as a value unique to the correction target, so that the correction data necessary for convergence correction is stored for every sample point. Unlike a conventional convergence circuit that stores data in a storage circuit, the storage capacity of the storage circuit can be significantly reduced.Also, for a basic correction wave, coefficients are sequentially determined from a basic correction wave having a high effect on correction data.
In some cases, convergence correction can be performed using the minimum basic correction wave without using up all the basic correction waves prepared in advance. Unlike the high-order identification method that applies correction data to the target, it is possible to perform optimal convergence correction that matches the characteristics of the correction target.In addition, compared to the method that determines correction data for every point on the screen,
The convergence adjustment can be done very easily,
Also, one weighting coefficient may be determined for one screen for each basic correction wave through execution and error without using a complicated method of changing the weighting coefficient for each scanning line for the basic correction wave. Only needs to store several types of weighting coefficients in the coefficient storage circuit.In the case of one or convergence correction, the weighting coefficient read from the coefficient storage circuit is multiplied by the corresponding basic correction wave according to the deflection mode, and the multiplication results are added up. Then, the correction data is calculated, the calculated correction data is stored in the correction data storage circuit for each screen, and the correction data read out from the correction data storage circuit, which is a buffer memory, in synchronization with the deflection scan is stored in the focus shift correction circuit. In order to supply the correction data, only the correction data for one screen in the specific deflection mode is required for the correction data storage circuit. Therefore, the correction data storage circuit can be released from the duty of semi-permanently storing the correction data unique to each display to be subjected to convergence correction, and the correction data storage circuit can be released from the same model. As for the display, by changing different correction data according to the deflection mode to a weighting coefficient for multiplying the basic correction wave, the coefficient can be stored in the coefficient storage circuit with less burden. Weighting coefficients corresponding to the deflection modes of the present invention can be stored, and an excellent effect such as a digital convergence circuit suitable for a multi-scan television receiver or the like can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram showing an embodiment of a digital convergence circuit of the present invention, and FIGS. 2 (A) to (G) show a composite wave on which correction data is stippled. FIG. 3 is a circuit diagram showing an example of a conventional digital convergence circuit. 5 Focus shift correction circuit 11 Digital convergence circuit 12 Coefficient storage circuit 13 Correction data storage circuit 14 Central processing unit 15 Address generation circuit 20 Timing generation circuit 21 Phase locked loop circuit

Claims (1)

(57) [Claims] A focus shift correction circuit for performing convergence correction based on correction data, and a plurality of basic correction waves of a horizontal scanning cycle or a vertical scanning cycle prepared in advance with a priority order, and a basic correction wave used according to the priority order is appropriately selected. The correction data is created by multiplying by a weighting coefficient of, and the weighting coefficient for minimizing the focusing deviation for the maximum number of the finite number of sample points for dividing the screen into a matrix is optimally determined through trial and error, and the correction data Then, the convergence deviation that could not be completely corrected is corrected with correction data obtained by multiplying the next priority basic correction wave by an appropriate weighting coefficient, and the convergence deviation settles within a predetermined allowable range at all of the sample points. When the convergence adjustment is performed by using the required number of basic correction waves according to the above priority order, A weight storage coefficient optimally determined for each of the required number of basic correction waves, a coefficient storage circuit that stores a horizontal deflection frequency or a vertical deflection frequency for each deflection mode, and a coefficient storage circuit according to the deflection mode during convergence correction. A central processing unit that reads out the weighting coefficients, multiplies the corresponding basic correction waves, and calculates the correction data by summing up the multiplication results; and a correction that stores the correction data calculated by the central processing unit at the time of convergence correction on a screen basis. Data storage circuit, read out the correction data from the correction data storage circuit in synchronization with the deflection scanning,
A digital convergence circuit comprising: a control unit that supplies the convergence deviation correction circuit.