Television – Image signal processing circuitry specific to television – Sweep expansion or reduction
Reexamination Certificate
1999-02-10
2001-07-17
Eisenzopf, Reinhard J. (Department: 2614)
Television
Image signal processing circuitry specific to television
Sweep expansion or reduction
C348S556000, C348S445000, C348S913000, C348S557000, C348S634000, C348S704000, C315S364000
Reexamination Certificate
active
06262779
ABSTRACT:
The present invention relates to a display apparatus such as for a television set or a computer terminal of a PC (Personal Computer) using a CRT (Cathode Ray Tube).
BACKGROUND OF THE INVENTION
As a method of driving a display apparatus, such as a CRT in a television set, deflection using a saw tooth wave is normally performed. In the case of, for example, horizontal scanning, a horizontal effective area is scanned at the leading edge of a saw tooth wave to display from the left end to the right end on a screen. On the other hand, the trailing edge becomes a retrace line interval for the horizontal scanning to return from the right end to the left end on the screen. At this time, video blanking is applied so that the scanning line, which returns, is not displayed. This horizontal retrace line interval is set to about 15% of the horizontal scanning interval.
In recent years, the screen of a television set tends to become larger, wide aspect displays have become widespread, and enlargement of the screen size has been proceeding. Demand for television sets with a small depth dimension (thin) in addition to a large screen is increasing.
The horizontal frequency of NTSC signals of an interlace scanning system is set to be 15.75 kHz. In contrast to that, the horizontal frequency of NTSC signals converted into a progressive scanning system (a line sequential system) is set to be 31.47 kHz. The use of this progressive scanning system has the advantage of being capable of reducing flickers of displayed pictures and providing images of high quality. Also, video signals having a higher horizontal scanning frequency than the conventional television signal are also increasing as in the case of highvision signals, PC signals and the like, and the horizontal deflection frequency tends to increasingly become a higher frequency.
Japanese Patent Laid-open Application No. Hei 3-76493 discloses a time axis compression apparatus for a television set for realizing such a progressive scanning system. In accordance therewith, it is possible to realize a progressive scanning system. Furthermore, this prior art makes it possible to compress the time axis of video signals in the horizontal period, and to show NTSC signals on a high definition display with their linearity maintained and without having to switch the horizontal deflection current. However, where NTSC signals are converted into a progressive scanning system, the horizontal frequency should be raised to about twice that of the interlace scanning system. Consequently, the current which flows to the horizontal deflecting coil of the deflecting yoke should also be approximately doubled, resulting in the problem of a power increase in the output section of the horizontal deflection circuit.
For this reason, a cost increase of the deflecting circuit, particularly the horizontal deflection circuit such as an increase in the power consumption of the horizontal deflection circuit and an expensive transistor being required has become a significant problem.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the above-described problems and to provide a display apparatus at a low cost.
It is another object of the present invention is to reduce power consumption occurring in the output section of the horizontal deflection circuit.
In order to achieve the aforementioned objects, a display apparatus such as a television set according to the present invention comprises: a blanking interval extension arrangement for extending a horizontal video blanking interval of a video signal; a deflecting arrangement for extending the retrace line interval within the extended blanking interval; and a display unit driven by the deflecting means, for displaying a video signal from the blanking interval extending extension arrangement.
In accordance with a feature of the present invention, by constructing the television set in the afore-described manner, it is possible to reduce the power consumption of the deflecting circuit by reducing variations of the deflection current with time.
A display apparatus according to the present invention is provided with a horizontal deflection circuit for driving the horizontal deflecting coil of a cathode ray tube, a vertical deflection circuit for driving the vertical deflecting coil of the cathode ray tube, and a video circuit for driving the cathode electrode of the cathode ray tube, and further provided with a signal processing circuit for converting the horizontal display interval of an input video signal and arranged before the video circuit. In addition, the ratio of the horizontal retrace interval to the horizontal period of the horizontal deflection circuit is set on the basis of the converted video signal outputted from this signal processing circuit.
According to a feature of the invention, the signal processing circuit is provided with a time axis conversion circuit for converting the ratio of the horizontal display interval to the horizontal period of the input video signal. Further the signal processing circuit is provided with an I/P (Interlace/Progressive) conversion circuit for ago converting a video signal of an interlace scanning system into a video signal of a progressive scanning system, and the ratio of the horizontal display interval to the horizontal period of the I/P converted signal is converted by the time axis conversion circuit.
In accordance with another feature of the present invention, a synchronizing pulse separation circuit is provided after the signal processing circuit, and the synchronizing signal for the converted video signal outputted from the signal processing circuit is separated by this synchronizing pulse separation circuit and supplied to the horizontal deflection circuit.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings.
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Kaizaki Kazuhiro
Motoshima Junji
Nakajima Mitsuo
Nishinaka Yuzo
Onozawa Makoto
Antonelli Terry Stout & Kraus LLP
Eisenzopf Reinhard J.
Hitachi Ltd
Natnael Paulos
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