Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
2001-05-25
2002-08-20
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C315S368180, C348S807000, C445S003000
Reexamination Certificate
active
06437522
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for controlling dynamic convergence by using a digital controlling method to correct arbitrary convergence astigmatism of a screen in a reflection yoke of a CRT picture device, and in particular, to a method for controlling digital dynamic convergence and a system thereof to perform individual and independent correction of the convergence with respect to each crossing point of a cross hatch pattern on a screen by receiving correction data from outside and storing the same in memory, reading the correction data from the memory, and converting the correction data to a voltage or a current so as to have a structure of outputting to magnetic field adjusting coils.
The present invention also relates to a method for controlling digital dynamic convergence and a system thereof for correcting convergence that enables a worker to perform approximate correction by generating correction data according to linear interpolation with respect to areas between crossing points when correcting each of the crossing points on a screen of a cross hatch pattern.
2. Description of the Prior Art
In general, the deflection yoke (DY) performs a function of deflecting R, G, B electron beams to desired positions on a screen of a CRT picture device. As the screens tend to be highly defined, it is impossible to achieve the converging function of the screen with the deflection yoke alone. Therefore, diverse kinds of correcting devices are usually mounted on the deflection yoke.
Of the diverse kinds of correcting devices, a dynamic convergence controller is widely used for actively controlling the converged state of the screen by attaching magnetic field adjusting coils having a structure of two poles, four poles or six poles operated under a principle of a convergence purity magnet (CPM), and moving the relative positions of R, B beams with respect to the G beam.
In particular, it is critical to apply the dynamic convergence controller to a highly defined screen leveled to a HD TV for transferring character information and graphic processing, etc. to conform to an appearance of digital TV broadcasting.
A circuit in the conventional dynamic convergence controller for a deflection yoke comprises a plurality of resistors, inductors, condensers and diodes, etc. The circuit is operated in the manner of correcting astigmatism of the screen by manually handling the controlling means such as variable resistors, etc. so as to control intensity of the current flowing in the magnetic field adjusting coils.
A current waveform predetermined in the magnetic field adjusting coils can only be applied with the adjusting circuit of the above type. Thus, the conventional adjusting circuit has a technical limit of correcting convergence astigmatism of only a few limited patterns. Furthermore, correcting a misconvergence of one area of the screen results in subsequent variation of a misconvergence of another area. Therefore, it is quite difficult to correct all the misconvergence of the entire screen.
Moreover, a worker checks the degree of convergence astigmatism with naked eyes, and properly adjusts the controlling means based on his/her own experience to correct the convergence astigmatism. Hence, it is almost impossible to correct the misconvergence of a CRT picture device having a large and flat screen with a superluminal angle to a desired level by means of such a conventional method.
The devices suggested to overcome the limit of the conventional method of measuring the convergence astigmatism with naked eyes as described above are display characteristics measuring units for measuring display characteristics of a convergence in a display device such as a color TV, color liquid crystal display (LCD) or a color plasma display panel (PDP).
This kind of a display characteristics measuring unit includes a photographing unit for separating a particular measured pattern containing a display of colors into each color component of R, G, B on a display device to be measured and photographing the same, an image processing unit for processing images of each color component and performing a predetermined further processing, and a display unit for displaying the measured result.
For instance, as disclosed in Japanese Laid-Open Patent Gazette No. 1996-307898, the convergence measuring unit photographs a white measured pattern displayed on a color CRT to be measured by a camera having a color area sensor such as a CCD, calculates a luminous center for each color component of the photographed images R, G, B while the image is processed, and displays a relative displacement of the luminous center in the amount of misconvergence.
Accordingly, the misconvergence measuring unit calculates an emitting position of a measurement pattern of each color component on a display surface of the color CRT that is measured by an image-fixed position of the measurement pattern of each color component on a photographing surface of a color camera, as well as a relative variation of the emitting position of each color component.
However, this technology poses a problem that a degree of precision easily varies depending on the temperature and humidity. For this reason, this technology is corrected by using a particular correction chart before measurement as shown in the accompanying FIG.
1
.
According to the correcting method shown in
FIG. 1
, a correction chart
103
illuminated by a fluorescent lamp
104
(a chart including a cross hatching pattern
105
on a plate of an opaque white color) is photographed by a photographing device
101
of a convergence measuring unit
100
, and the correction data showing relative positional relations between each area sensor is calculated by using the photographed image. The calculated correction data is stored in a memory within a main body
102
of the device so as to be used as data for correcting variation of the luminous center position of the measurement pattern of each color component.
According to the conventional method for correcting the relative variation of an area sensor, a position (an absolute position) of each area sensor in a reference coordinate of a convergence measuring system is calculated by using image data of each color component obtained by photographing a particular correction chart, while a relative variation of the area sensor is calculated based on that calculation. Because of the numerous computing parameters (mediating variants), a long period of time is consumed for computation.
Moreover, since a particular correction chart is used rather than a measurement pattern displayed on the CRT to be measured, a problem has arisen that it is inconvenient and difficult to correct a convergence measurement system in a production line.
The recently developed technology to overcome the above problem is the technology disclosed in Korean Laid-Open Patent Gazette No. 1999-013780. The disclosed technology is related to an automatic convergence measurement device for a color CRT.
The accompanying
FIG. 1
is a schematic view illustrating construction of a convergence-measuring unit
1
for a color CRT. The convergence-measuring unit
1
comprises a photographing unit
2
and a measuring unit
3
.
The photographing unit
2
photographs a predetermined measurement pattern (for instance, a cross hatching pattern, a dot pattern, etc.) displayed on a display surface of the color display
4
to be measured. A pair of photographing cameras
21
,
22
is installed at the photographing device
2
for sensing images by using a stereovision method.
The measuring unit
3
computes an amount of misconvergence of a color display by using image data of the measurement pattern obtained by the photographing device
2
, and displays the computed result on a displaying unit
36
.
The photographing camera
21
is a color photographic device of a three-plate type, comprising a dichroic prism
212
installed at inside of the photographing unit
2
for separating the light into three colors at a rear side of the photographing lens
Cho Ho Jin
Moon Bong Mo
Shim Ick Chan
Darby & Darby
Samsung Electro-Mechanics Co. Ltd.
Tran Chuc
Wong Don
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