Television – Display or receiver with built-in test signal generator,...
Reexamination Certificate
2000-04-11
2003-09-30
Lee, Michael H. (Department: 2614)
Television
Display or receiver with built-in test signal generator,...
C348S189000, C348S181000
Reexamination Certificate
active
06628324
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a video signal producing apparatus and a video signal producing method in which a composite video signal used for a television set or a video tape recorder is produced.
2. Description of Related Art
A display principal of a Braun tube used in a television set is initially described in brief.
In a television set, an electron beam is moved in horizontal and vertical directions to display an image on an image plane of a Braun tube. The movement of the electron beam in the horizontal direction is called a horizontal scanning, and the movement of the electron beam from top to bottom is called a vertical scanning. Also, when the horizontal scanning and the vertical scanning are simultaneously performed in the Braun tube, a number of fine loci extending in the horizontal direction appear on the image plane. Each locus is called a horizontal scanning line.
A plurality of broadcast systems for the color television are known, and regulations of National Television System Committee (NTSC) are adopted in Japan. In the NTSC, 525 horizontal scanning lines are used to display a frame-image on the image plane for each frame, and 30 frame-images are sent to the Braun tube every second. In practical use, to suppress the flickering occurring in the frame-images, the 525 horizontal scanning lines of each frame-image is divided into two groups of 262.5 horizontal scanning lines alternately arranged in the 525 horizontal scanning lines to produce two rough images respectively composed of one group of 262.5 horizontal scanning lines from each frame-image (refer to FIG.
10
B), and 60 rough images are displayed every second. This scanning is called an interlacing scanning, and each rough image composed of the 262.5 horizontal scanning lines corresponds to one field. The rough image composed of 262.5 horizontal scanning lines numbered by lower serial numerals is called an odd field, and the rough image composed of 262.5 horizontal scanning lines numbered by higher serial numerals is called an even field. The odd and even fields are interlaced with each other for each frame. As shown in
FIG. 10B
, one odd field is displayed by 262.5 horizontal scanning lines indicated by solid lines, one even field is displayed by 262.5 horizontal scanning lines indicated by broken lines, and the odd fields and the even fields are alternately displayed.
In the horizontal scanning, a horizontal retrace blanking period is provided after the completion of each horizontal scanning. Also, in the vertical scanning, a vertical retrace blanking period is provided after the completion of each vertical scanning. In each retrace blanking period, the electron beam is cut. Therefore, as shown in
FIG. 10A
, neither horizontal retrace line nor vertical retrace line is displayed on the image plane.
In each horizontal retrace blanking period, a horizontal synchronizing signal H
sync
is arranged to determine a starting position of the horizontal scanning line. Also, a vertical synchronizing signal V
sync
is arranged in each vertical retrace blanking period to determine a starting position of the vertical scanning.
The beam operation performed for displaying an image on the image plane of the Braun tube is controlled according to a composite video signal produced in a video processing circuit. In the composite video signal, information of scanning lines, information of the horizontal retrace blanking periods, information of the vertical retrace blanking period, information of the horizontal synchronizing signals, information of the vertical synchronizing signal, field information, and image information (color information and luminance information) are included for each field. In a video tape recorder (called VTR), three cords (yellow, red and white) to be connected with the television set are provided, and the composite video signal is output from the VTR to the television set through the yellow cord.
FIG. 11A
is a waveform view showing various signals included in the composite video signal, and
FIG. 11B
is an enlarged waveform view showing signals arranged in one horizontal retrace blanking period.
As shown in
FIGS. 11A and 11B
, one horizontal synchronizing signal B and a color burst signal E are arranged in each horizontal retrace blanking period A, and an image signal is arranged in a period other than the vertical retrace blanking period and the horizontal retrace blanking periods.
An image watched by a viewer is formed according to the image signal. A level range C shown in
FIG. 11B
indicates a luminance range of the image. As a level (or an electric potential) of the image signal is heightened in the level range C, the luminance of the image becomes heightened, and the image approaches the white color. In contrast, as a level of the image signal is lowered in the level range C, the image approaches the black color. That is, the top level (5 V) in the level range C corresponds to the white color, and the bottom level in the level range C corresponds to the black color and is called a pedestal level. The pedestal level is fixed. Also, in cases where a level of the image signal is placed between the top and bottom levels, the image becomes gray, and the luminance of the image changes with the level of the image signal.
The color of the image is determined by a phase difference between the color burst signal E and the image signal. A detail description of the color determination is omitted.
In addition, to indicate the horizontal synchronizing signal H
sync
and the vertical synchronizing signal V
sync
, a ground level (GND level) set to 0 V is used.
The electron beam is returned from the right side to the left side of the viewer during each horizontal retrace blanking period (refer to FIG.
10
A and
FIG. 10B
) when the viewer watches the image plane, and a horizontal synchronization of the electron beam is performed during the beam returning period according to the horizontal synchronizing signal. Also, the electron beam is returned from the bottom to top (refer to FIG.
10
A and
FIG. 10B
) during the vertical retrace blanking period corresponding to a period of the horizontal scanning lines which are numbered from No. 1 to No. 21.5 for the odd field and are numbered from No. 262.5 to No. 284 for the even field, and a vertical synchronization of the electron beam is performed during the beam returning period according to the vertical synchronizing signal.
The odd and even fields can be distinguished by the phase relationship of the vertical and horizontal synchronizing signals. That is, the horizontal synchronizing signal and the vertical synchronizing signal have the same phase in case of the odd field, and the phase of the horizontal synchronizing signal is opposite to the phase of the vertical synchronizing signal in case of the even field.
FIG. 12
is a constitutional view showing a conventional video signal producing apparatus.
As shown in
FIG. 12
, a conventional video signal producing apparatus is composed of
a video input terminal
1
for receiving a composite video signal indicating a video image from a VTR,
an oscillating circuit
8
for generating a main clock signal,
a microcomputer-for-television
9
for producing a composite video signal indicating an on-screen display (hereinafter, called OSD) character such as a channel number or a composite video signal indicating a test pattern according to the main clock signal generated by the oscillating circuit
8
, outputting the composite video signal of the test pattern indicated by two port output levels (a pattern output level fixed to 5 V and the ground level 0 V), and outputting the composite video signal of the OSD character as a red (R) signal, a green (G) signal and a blue (B) signal indicated by two levels (0 V and 5 V),
a pair of patterned resistors
16
and
17
, serially connected with each other, for adding the pedestal level (Vp) to the composite video signal of the test pattern output from the microcomputer-for-television
9
,
a selector
2
for selecting the com
Hosotani Osamu
Onishi Yasushi
Burns Doane , Swecker, Mathis LLP
Lee Michael H.
Mitsubishi Denki & Kabushiki Kaisha
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