Television – Basic receiver with additional function – For display of additional information
Reexamination Certificate
1999-11-02
2004-09-14
Diep, Nhon (Department: 2613)
Television
Basic receiver with additional function
For display of additional information
C348S565000, C348S678000, C348S687000, C348S689000
Reexamination Certificate
active
06791623
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a display device for displaying computer images including characters and figures mainly and television images including natural images mainly and a system thereof and particularly to a display device having a frequency resolution conversion function for an interlace scanning signal such as an NTSC, PAL, SECAM, or high definition television signal or an image information signal in a personal computer and to a display device for displaying video signals under various standards such as various computers under different specifications, various televisions, and video output devices.
2. Description of the Prior Art
Recently, as multi-media have been developed, there are increasing needs for displaying natural images of the NTSC system which are picked up by a household VTR or video camera on a display device for displaying images of a personal computer or work station.
However, although most of horizontal scanning frequencies of video signals of a personal computer are almost 24 kHz or higher, the horizontal scanning frequency of the NTSC system is low such as 15.75 kHz. When the display device side attempts to correspond to the horizontal scanning frequency of 15.75 kHz, the burden of the horizontal deflection circuit increases and the image quality is degraded such as an increase in screen distortion. Therefore, a double conversion process for doubling the horizontal scanning frequency by converting an interlace scanning signal to a sequential scanning signal is being examined.
Conversion to a sequential scanning signal is broadly divided into two systems. One of them is an intra-field scanning line interpolation system for generating interpolation scanning lines using the scanning lines in the same field and the other is an inter-field scanning line interpolation system for generating interpolation scanning lines using the scanning lines between the preceding and subsequent fields.
When the inter-field scanning line interpolation system among these two sequential scanning conversion systems is applied to the motion portion of an image, two fields which are different in time are composed, so that a problem arises that a duplicate image is formed. Therefore, it is necessary to generate interpolation scanning lines for the motion portion of an image by the inter-field scanning line interpolation system.
In the inter-field scanning line interpolation system, there are a single scan line doubler system in which a line memory which can store a video signal of at least one scanning line is installed, and a video signal of the interlace scanning system is written into this line memory in units of one scanning line, and it is read twice every time at a speed two times of that of writing and an operation interpolation system for generating interpolation scanning lines by operations in consideration of weighting of upper and lower scanning lines.
However, in the single scan line doubler system, the resolution in the vertical direction reduces and the image quality may be degraded. Therefore, as disclosed in Japanese Patent Application Laid-Open 3-113977, a proposal that the degradation of the resolution in the vertical direction is suppressed by modifying the vertical deflection circuit on the television set side so as to display the same scanning line which is read two times every time at the same location on the cathode ray tube is made. The aforementioned operation interpolation system is disclosed in Japanese Patent Application Laid-Open 4-157886 and others.
As disclosed in Japanese Patent Application Laid-Open 63-63283, an example that the horizontal scanning frequency is doubled by doubling the field frequency and the vertical deflection circuit is devised so as to prevent the scanning positions of an odd field and the scanning positions of an even field from confusing with each other may be cited.
A method for modifying the vertical deflection circuit in such a conventional apparatus requires a means for switching an output signal of the vertical deflection circuit on the television set side, so that the vertical deflection circuit has an extremely special constitution and the cost goes up.
In the operation interpolation system, it cannot be avoided that the cost is greatly increased due to addition of an operation circuit. Furthermore, scanning lines generated by operations are scanning lines which do not exist in the original video signal, so that the sharpness of an image reduces and the image quality may be degraded on the contrary.
Next, the standard for a video output device such as a computer terminal or a television set will be considered. The specification for a video signal sent from a computer is not standardized at present and the horizontal and vertical scanning frequencies, video display period, video display position, and video flyback time are different, so that a dedicated display device corresponding to each video signal is generally necessary. For a request for displaying suitable images corresponding to various video signals on one display device, there is a multi-scan display available. In this kind of display device (multi-scan display), many active elements are used in the deflection circuit, and the circuit is increased in scale so as to keep the stability and reliability of operation, and as a result, how to produce and adjust the display device easily comes into a problem.
The aforementioned scanning frequency of a video signal is increasing further at present and accordingly, the signal specification to which a display device corresponds is enlarged. Recently, a display device which can display not only the aforementioned computer signals but also video signals such as television (NTSC) signals and Hi-Vision signals has been required. Concretely, as to the horizontal scanning frequency of a video signal, a display device which can correspond to from 15.75 kHz of an NTSC signal to about 90 kHz equal to a high definition image or a signal of the CAD/CAM class (2M pixels) is desired.
When an extremely wide range of frequencies is handled as mentioned above, it is considerably difficult for the conventional prior art to correspond to them. The reason is that to allow corresponding to the scanning frequency of a video signal, the complexity of switching control of the element constant of the deflection circuit and the number of parts increase and the circuit scale also increases so as to ensure the reliability of operation. Furthermore, it becomes difficult to ensure the performance by corresponding to the display image quality and screen distortion characteristic of various video signals. As a result, the number of parts to be adjusted increases and the cost goes up.
As a method to solve such a problem, there is a method available that a frequency resolution conversion circuit for processing a video signal digitally and converting it to a signal at the desired horizontal and vertical scanning frequencies (hereinafter called a scan converter) is used. As an example using such a scan converter, there is a display device described in Japanese Patent Application Laid-Open 6-138834.
A display device having the aforementioned conventional scan converter will be explained hereunder with reference to the accompanying drawing.
FIG. 30
shows a rough configuration example thereof. In
FIG. 30
, numeral
11
indicates a scan converter,
13
a deflection circuit,
14
a cathode ray tube (CRT),
120
a video processor circuit,
150
a
,
150
b
, and
150
c
a video circuit Rch, a video circuit Gch, and a video circuit Bch respectively,
151
a video output circuit,
1100
an input video signal,
1200
an input synchronizing signal, and
1300
an output synchronizing signal.
An input video signal
1100
under various standards of computers is inputted to the scan converter
11
and sampled by the A/D converter which is a component of the scan converter
11
by the dot clock of the input video signal
1100
which is regenerated from the input synchronizing signal
1200
by the PLL (phase lo
Arai Ikuya
Hirose Masatoshi
Imai Yasuhiro
Inoue Fumio
Kawasaki Jiro
Antonelli Terry Stout & Kraus LLP
Diep Nhon
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