MXPA98001005A - Method to correct convergence in a proyecc television receiver - Google Patents

Abstract

The present invention relates to a projection television receiver, it is known to use a diffraction grating pattern to define on the image screen a multiplicity of intersection points for which convergence correction values are determined, stored digitally and are used during reproduction for the purpose of correcting convergence. It is an object to reduce the expense of time for such correction at the place of production or at the place where the client is located and, in addition, to improve the correction of the convergence at the edges of the image. First a rough correction or correction is made in the laboratory or in the pilot series using a first matrix with a fine diffraction grid pattern with correction values for all the receivers of a specific receptor type in order to determine the starting initials. Subsequently, a final correction or fine correction is made in series production individually for each receiver using a second matrix with a coarse diffraction grating pattern. In particular, a method to correct the convergence in a projection television receiver with automatic convergence correction

Description

METHOD TO CORRECT CONVERGENCE IN A PROJECTION TELEVISION RECEIVER.

DESCRIPTION OF THE INVENTION The invention proceeds from a method for correcting the convergence in a projection television receiver according to the preamble of claim 1. In order to correct the convergence in a projection television receiver it is known how to display a pattern on the screen. of diffraction grating? e narrow horizontal and vertical white lines forming a multiplicity of intersection points. The correction values are determined before the convergence for each intersection point. As a rule, these are 6 values, specifically for the primary colors R, G, B and for the horizontal direction and the vertical direction. These correction values are stored in a digital memory. During image reproduction, the correction values are extracted for each individual intersection point from the memory, converted to analog correction values in digital / analogue converters, and used to adjust the convergence. The correction values - between two intersection points in each case are obtained in the horizontal direction by slow-pass filtering and in the vertical direction by interpolation. A number of 16 lines in the horizontal direction and 13 lines in the vertical direction, for example, corresponding to 208 intersection points and 1248 correction values, are used for an acceptable convergence correction. The correction of the convergence is made with the help of deflection currents that are fed to an auxiliary baffle coil for horizontal convergence and an auxiliary baffle coil for vertical convergence. These auxiliary baffles are required because due to their high frequency components the correction currents can not be fed to the main baffle coils, which has a high inductance. Due to the high number of intersection points and correction values, a considerable time of several minutes is required to adjust the convergence in the place of production or in the place where the client is located. An object of the invention is to simplify the correction of the convergence in the factory during production and / or in the receiver in the place where the customer is located and, in particular, to reduce the time expenditure required for the correction of the convergence . According to a development of the invention, the correction of the convergence is improved at the edges of the image. This object is achieved by means of the invention specified in claim 1. Advantageous developments of the invention are specified in the sub-claims. The invention therefore allows the correction of the convergence required for a receiver to be carried out in a shorter time and also with a higher quality. In particular, time and costs can be saved at the place of production and at a point of service. The solution according to the invention for achieving convergence correction therefore consists of two stages. In a first stage, a pre-correction or rough correction is first performed for the best convergence on the fine diffraction grating pattern with all the diffraction grating points, for example 16 x 13 = 208 points, doing so in the laboratory or in the pre-produces ion. The correction is also effected by non-visible feedback for the favorable signal performance of the convergence circuit power gain in order to avoid long settling times and large voltage jumps. An average correction signal is calculated from the values of a specific number of receivers found that are suitable, and all subsequent receivers are entered as the starting position. This correction corrects approximately 85% of the convergence errors. In a second stage after the previous one, only a final correction or correction using a reduced number of, for example, 25 points of diffraction grating is made at the place of production or at a high level service point. Starting from a reduced number of diffraction points, the 208 points of the fine diffraction grating pattern can be obtained by interpolation between the diffraction grating points in the final correction. According to a particularly advantageous method of the invention, a fourth degree polynomial is selected as the interpolation function. However, it is also possible to use polynomials of lower or higher grade for this purpose. The correction values obtained during the procorrection thus serve in this case as initial values for the subsequent final correction. The final correction then corrects only about 15% of the convergence errors. As a result, substantial time is saved during production or during service. The quality of the correction made in this way is, however, comparable to the quality of correction by means of the fine diffraction grating pattern. According to a development of the invention, the intersection points with associated correction values in the horizontal direction are also provided outside the visible image area. The reason for this is the following: the correction values are formed by correction currents which are fed in each case to the auxiliary deflector coils for the horizontal direction and the vertical direction. These correction currents can have large changes in amplitude, particularly in the case of a line change, that is, at the beginning of a new line. High voltage peaks and transient phenomena occur afterwards due to the inductance of the auxiliary correction coil. In many cases, the response of the correction currents is too slow due to the inductance of the auxiliary deflector coils. If the correction is initiated before the visible image area, due to the intersection points located outside the visible image area, the respective correction current can be improved in advance approximately to its ideal value or ideal characteristic at the beginning of the area of visible image, that is to the right left edge of the image, for example. It is therefore possible by means of this development of the invention to improve the convergence in the edge regions of the image without the need for circuits that serve to supply the correction currents that are going to be overloaded or oversized. Correction values for points of intersection outside the visible image area can be obtained by extrapolation or similar mathematical calculations from correction values within the visible image area. The invention is explained in more detail below with the aid of the drawings in which: Figure 1 shows a fine diffraction grating pattern for the projection of coarse ion or correction in the laboratory for the purpose of calculating the values of Initial correction, Figure 2 shows a rough diffraction grating pattern for final correction or fine correction, individually for each receiver during production, Figures 3-5 show an example of the convergence correction at the upper edge of the image , with correction values for procorrection and final correction, and Figure 6 shows the development with correction values outside of the visible image area. A first fine matrix for such projection is displayed over the image area 1 visible in Figure 1, having a fine diffraction grating pattern with 16 KV intersection points in the horizontal direction and 13 KV intersection points in the direction vertical, which is 208 points of total intersection, which is shown in the visible image area 1 in Figure 1. The pro-correct ion is effected in the horizontal and vertical directions with the aid of this fine diffraction grating pattern corresponding to 16 x 13 x 6 1248 correction variables, for the correction of convergence for red, green and blue, respectively. Approximately 85% of the convergence errors can be corrected by means of this ion, which are preferably determined for each receiver of a pilot series. 5 points of intersection KE in the horizontal direction and 5 points of intersection KE in the vertical direction are displayed in a second coarse matrix over the area 1 of the image visible in Figure 2, ie a total of only 25 points of intersection. The correction values are determined, specifically individually for each receiver, for these 25 points of intersection with the purpose of the final correction described. The remaining 15% of convergence errors can be removed later using this correction in series production or at the service point. Figure 3 again shows the image area 1 with the first fine matrix with the fine diffraction grating pattern. As an example, the first convergence correction in the vertical direction for the red color in the uppermost fine part of the image is described. Figure 4 shows the relatively large correction DV values for procorrection with the help of the fine diffraction grating pattern according to Figure 1. Figure 5 shows, correspondingly, the substantially lower correction values DE for the final correction with the aid of the second matrix with the coarse diffraction grating pattern according to Figure 2. The total correction is then the result of the procorrection by the DV values with the subsequent calculation or the interpolation of the DE values for the final correction . In Figure 6, in addition to the intersection points KV within the visible image area 1, the symbolically indicated additional intersection points of Kl, K2 are also provided outside of the visible image area 1, specifically to the left of the left edge of the image. the image and to the right of the right edge of the image. The purpose of this is the following: curve 2 indicates that a correction value can vary greatly in each case between two lines. This means that in specific cases the correction deflection current that makes the correction must, if appropriate, change to a large extent in a short time, in order to have, at the beginning of the new line, the value that is correct for Correction of convergence. The correction current, however, is fed to an auxiliary baffle coil, which constitutes an inductive load. As a result, there is some inertia II necessarily in response to the effect that at the beginning of a line the correction current can not reach the correct value quickly enough, and this is also due to the voltages of operation of the output amplifiers due to the voltage induced by the change in current. Now, if the intersection points Kl, K2 to form the correction current are provided in advance outside the visible image area 1, the correction current can be better approximated to the ideal value at the beginning of a line in each case, ie on the right edge of the image. This means that the correction is improved at the edges of the image.

Claims (9)

1. A method for correcting the convergence in a projection television receiver, in which the correction values are determined for the points of intersection, defined by a matrix, of a diffraction grating pattern displayed on the screen, are stored in a digital memory and are used for correction purposes during image reproduction, characterized in that a first ion or coarse correction is performed in the laboratory or in the pilot series using a first matrix with a diffraction grating pattern (KV). fine with the same correction values for all receivers of a specific receiver type in order to determine the initial values, and a final correction or fine correction is subsequently made in series production individually for each receiver of the receiver type using a second matrix with a rough diffraction grating pattern (KE).

2. A method according to claim 1, characterized in that the fine diffraction grating pattern for the pro-correction contains approximately 200 points (KV) of intersection.

3. The method according to claim 1, characterized in that the rough diffraction grating pattern for the final correction contains approximately 25 points (KE) of int ersection.

4. The method according to claim 1, characterized in that the pro-correction effects approximately 85% of the total correction required.

5. The method according to claim 1, characterized in that all points of the fine diffraction grating pattern in the horizontal and vertical directions are used for the purpose of pro-correction.

6. The method according to claim 1, characterized by setting the correction values for the final correction is obtained by mathematical interpolation from a few correction values.

7. The method according to claim 6, characterized in that the interpolation function is a 4th degree polynomial.

8. The method according to claim 1, characterized in that the points (Kl, K2) of intersection with the associated correction values in the horizontal direction are also provided outside the visible image area (1).

9. The method according to claim 8, characterized in that the correction values for the points of intersection outside the visible image area (1) are obtained by extrapolation from correction values within the visible image area (1). SUMMARY OF THE INVENTION In a projection television receiver, the use of a diffraction grating pattern is known to define on the image screen a multiplicity of intersection points for which convergence correction values are determined, stored digitally and used during reproduction for the purpose of correcting convergence. It is an object to reduce the expense of time for such correction at the place of production or at the place where the client is located and, in addition, to improve the correction of the convergence at the edges of the image. First a co-correction or gross correction is made in the laboratory or in the pilot series using a first matrix with a fine diffraction grating pattern with correction values for all the receivers of a specific receptor type in order to determine the initial values. Subsequently a final correction or fine correction is made in series production individually for each receiver using a second matrix with a coarse diffraction grating pattern. In particular, a method for correcting convergence in a projection television receiver with automatic convergence correction. Figures 1.2.