Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
1998-11-05
2001-02-27
Ham, Seungsook (Department: 2178)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C315S008000
Reexamination Certificate
active
06194848
ABSTRACT:
CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C § 119 from an application entitled
Automatic Magnetic Field Compensator For A CRT
earlier filed in the Korean Industrial Property Office on Nov. 5, 1997, and there duly assigned Ser. No. 97-58213 by that Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automatic magnetic field compensator for a cathode ray tube, and more particularly to an apparatus for automatically compensating for the changes generated in a display with a cathode ray tube in effect of the earth's magnetic field by using magnetic sensors detecting the earth's magnetic field.
2. Description of Background Art
Usually, a display with a cathode ray tube (CRT) has a problem that both sides of a screen tilt upward or downward in response to the effect of the earth's magnetic field (hereinafter: ‘earth's magnetic field’ is abbreviated as ‘EMF’.) according to the installation direction, i.e. north, south, east or west. Accordingly, the effects of the EMF must be eliminated to realize a stabilized picture on a screen. More particularly, a tilt of screen is compensated for by flowing direct current (DC) with variable flowing direction and variable current intensity through a compensation coil for EMF wound around the neck of a CRT, around which a deflection yoke is also wound.
An apparatus for compensating for the deflection of electron beam in a CRT display is described in the Korean patent application No. 94-1310 (its Korean examined publication No. 96-13551).
The above-mentioned automatic magnetic field compensator, which is set forth in FIG. 1, comprises a compensation value determining unit 10 for generating compensation values respectively corresponding to each directional magnetic field, and a direction detect and select unit 20 for receiving the compensation values from the compensation value determining unit 10 and sensing the direction of a CRT to selectively output one of the received compensation values. This automatic magnetic field compensator further comprises a deflection compensating unit 30, coupled to the direction detect and select unit 20, for receiving the selected compensation values from the direction detect and select unit 20 and compensating for deflection of electron beam emanating from an electron gun in a CRT.
In FIG. 1, the direction detect and select unit 20 comprises a directional sensor (not shown) and an output select switch (not shown), thereby detecting the direction of a CRT to control the output of output select switch in response to the detection result. A compensation value of the east is set to be a reference voltage and VA indicates a compensation value of the west. VB indicates a compensation value of the south and VC indicates a compensation value of the north.
To explain the automatic magnetic field compensator referring to FIG. 1, the directional sensor in the direction detect and select unit 20 detects the present direction of a CRT. The direction detect and select unit 20 controls the output select switch to input the compensation values from the compensation value determining unit 10, which corresponds to the direction of a CRT, to the deflection compensate unit 30. The deflection compensate unit 30 compensates for the deflection of electron beam in a CRT in response to the input compensation values, thereby compensating for picture distortion, screen tilt, and color convergence to display a normal picture on a CRT screen.
The conventional automatic magnetic field apparatus described above, however, has a disadvantage that a display with a cathode ray tube must apply a predetermined voltage to the magnetic field compensator continuously in order to compensate for picture distortion and color convergence and therefore the display consumes power excessively.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an apparatus for automatically compensating for the deflection of electron beam in a CRT display by the EMF using magnetic sensors automatically detecting EMF.
To achieve the above-mentioned objects, an apparatus for automatically compensating for the deflection of electron beam in a CRT display by the EMF comprises detection means for detecting the EMF in response to the EMF output control signals, a pulse generator for generating pulse signals with a predetermined frequency corresponding to the EMF detected by the detection means, a counter for counting the pulse signals from the pulse generator at predetermined times to generate a gate signal, control means for receiving the gate signal generated by the counter and comparing the gate signal with a reference signal to generate a compensation value for the EMF, the control means further generating output state control signals for controlling the output state of the detection means, and process means for compensating for the deflection of electron beam emanating from an electron gun in a cathode ray tube in response to the compensation value generated by the control means.
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Bushnell , Esq. Robert E.
Gregory Zakia N.
Ham Seungsook
Samsung Electronics Co,. Ltd.
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