The present invention relates to a display apparatus, a marker signal making process, a marker signal detector circuit, and a control signal generator circuit that are suitable for use when making a display in which, e.g. a display screen is divided into a plurality of areas and images whose picture qualities are different in every area are displayed. Particularly, the present invention relates to the display apparatus, the marker signal making process, the marker signal detector circuit, and the control signal generator circuit in which, when an image signal is displayed on a screen provided with an area for displaying information on characters, numerics, etc. and an area for displaying an acquired image of photograph, moving video, etc., the picture quality of displayed photograph, moving video, etc. is improved especially without degrading the displayed characters, numerics, etc.
In a display apparatus of a television receiver, etc. which displays, e.g. image signals by a television broadcast or image signals reproduced from a video tape, etc., in order to improve the displayed picture quality for a still image represented-by a photograph picture, etc. and a moving image represented by a motion picture, etc., picture quality improving techniques such as enlargement of brightness difference (hereinafter referred to as contrast ratio) between white level and black level of displayed image, e. g. by increasing the amplification factor for image signals or by emphasizing outlines of images (hereinafter referred to as sharpness) etc. have heretofore been practiced.
Moreover, various kinds of semiconductor integrated circuits hereinafter referred to as IC), etc. have been implemented that have at least one of these picture quality improving functions and is arranged to control these picture quality improving functions, e.g. by exterior direct current voltage (hereinafter referred to as DC voltage) or by control means using an information communicating means such as what is called a bus communication or the like. As a typical one of them, e.g. a preamplifier IC used for an image amplifier circuit, a RGB decoding IC for resolving from luminance/color difference signals into R/G/B signals, and the like are known.
FIG. 17 shows an example of a structure of display apparatus having such a picture quality improving function. Further, in FIG. 17, for making easy to understand advantageous effects of the present invention described below, a structure of display apparatus of a monitor display apparatus which receives signals, e.g. from a computer equipment is shown. Prior art will be described with reference to this structure.
In FIG. 17, image signals of red, green, blue (R/G/B) input, e.g. to input terminals 701R, 701G, 701B are supplied through respective capacitors 702R, 702G, 702B to a preamplifier IC 703. In the preamplifier IC 703, the supplied image signals (R/G/B) are supplied through respective clamping circuits 801R, 801G, 801B to sharpness improving circuit 802R, 802G, 802B and taken out through amplifiers 803R, 803G, 803B.
From a microcomputer (hereinafter referred to as micon) 700 that is present within the apparatus and controls various kinds of functions is output, e. g. sharpness control DC voltages and contrast ratio control DC voltages, which are supplied to the preamplifier IC 703. Thus, in the preamplifier IC 703, e. g. the sharpness improving circuits 802R, 802G, 802B and the amplifiers 803R, 803G, 803B are controlled so that the sharpness and the contrast ratio may be improved, respectively.
Image signals (R/G/B) derived from the preamplifier IC 703 are further amplified by an output amplifier 704 and then taken out through capacitors 705R, 705G, 705B. These resulting image signals (R/G/B) are subjected to DC voltage conversion by a cut off adjusting amplifier 706 and then supplied to, e.g. a cathode ray tube (hereinafter referred to as CRT) 707 that is a display means, thus causing the image by image signals (R/G/B) with improved picture quality to be displayed on a screen of CRT 707.
By the way, in the monitor display apparatus for displaying, e.g. outputs from the computer, its primary object in the past has been to display information on characters, numerics, etc. of documents, table calculations, etc. output from the computer. For this reason, the monitor display apparatus has generally been used for displaying image signals supplied from the computer, e.g. in the form of a binary signal xe2x80x9c1/0xe2x80x9d on a proper brightness level.
In contrast, recent computers called multimedia display not only the above-mentioned information on characters, numerics, etc. but also an image of photograph, moving video or the like taken from a disk unit or a video card in an arbitrary area called a window. In that case, an image of the thus acquired photograph, moving video, etc. is lower in the contrast and sharpness as compared with the information on characters, numerics, etc., and so if these are displayed together, the picture quality of displayed photograph, moving video, etc. looks remarkably deteriorated.
Accordingly, in such a monitor display apparatus, for the purpose of improving the picture quality of images of photograph, moving video, etc., the improvement of the contrast ratio and the sharpness has been considered.
However, in the conventional monitor display apparatus, the improvement of picture quality by the enlargement of brightness difference and the outline emphasis, etc is carried out uniformly over the entire display screen. For this reason, when there is an area displaying the characters, numerics, etc. in the screen, these displays may on the contrary turn hard to see. This makes eyes readily tired, particularly if the brightness displaying the characters, numerics, etc. is too high, which results in causing a picture quality deteriorating effect of disabling a long time watching (use) and the like.
In recent years, due to the development of so-called internet and the spread of teletext, even common television receivers have increasingly such opportunities as displaying the image of photograph, moving video, etc. together with the display of characters, numerics, etc. on one screen. Thus, in such television receivers, if the improvement of picture quality by the enlargement of brightness difference and the outline emphasis, etc. is carried out uniformly over the entire screen, a fear will be caused that the display of characters, numerics, etc. in the screen may turn hard to see.
The present invention has been made in consideration of these points. The problem intended to solve is that, with the conventional apparatus, when displaying the image of photograph, moving video, etc. together with the information on characters, numerics, etc., the picture quality of image of photograph, moving video, etc. looks remarkably deteriorated, but if the picture quality of these photograph, moving video, etc. is improved, the picture quality of the display of characters, numerics, etc. will turn worse.
The present invention is arranged to specify arbitrary areas on a display screen and apply respective arbitrary image processings to every specified area. This will enable the picture quality of image of photograph, moving video, etc. to be improved without making the information on characters, numerics, etc. hard to see, when the image of photograph, moving video, etc. is displayed together with the information on characters, numerics, etc. In this connection, the display apparatus, the marker signal making process, the marker signal detector circuit, and the control signal generator circuit according to the present invention will be disclosed.