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US 5,039,923 AGranted
Focus adjusting device for projection display
AssigneeHitachi, Ltd.
InventorsMasanori Ogino, Takeo Yamada, Miyuki Ikeda, Ichiro Niitsu
Life of this patent
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Abstract
A focus adjusting device for projection display, comprising at least one set of 4-pole magnetic field generating means, and adjustment means for adjusting the magnetic field strength of the 4-pole magnetic field generating means so as to eliminate astigmatism caused by fabrication error and attachment error of an electron gun and a focus coil.
Claims12
A focus adjusting device for a CRT in a projection display, comprising:
- deflection coil means;
- 6-pole pole piece means disposed at a position preceding the deflection coil means with respect to a direction of electron propagation;
- main focus coil means disposed at a position preceding the 6-pole pole piece means with respect to the direction of electron propagation;
- auxiliary deflection winding means disposed on the 6-pole pole piece means;
- two astigmatic aberration cancellation winding means disposed on the 6-pole pole piece means for cancelling astigmatic aberration caused by the main focus coil means, wherein one of the two astigmatic aberration cancellation winding means produces a magnetic field having six magnetic poles, an angle between adjacent ones of the six magnetic poles being approximately 60.degree.;
- and
- current adjusting means for adjusting currents in the two astigmatic aberration cancellation winding means so as to effect cancellation of the astigmatic aberration caused by the main focus coil means.
4 more elements
A focus adjusting device for a CRT in a display, comprising:
- magnet means, having a plurality of magnetic poles, for generating a constant magnetic field;
- and
- deflection coil means disposed at a position preceding the magnet means with respect to a direction of electron propagation, wherein the deflection coil means comprises winding means having a winding distribution for increasing pincushion distortion and for enabling cancellation of astigmatic aberration caused by the magnet means.
Dependencies are inferred from the claim text.