(1) Field of the Invention
This invention relates to a novel method for processing a picture to reproduce the picture with improved visibility on a color television receiver, and to a picture processor therefor.
(2) Description of the Related Art
Reference is first made to FIG. 3 which is a simplified block diagram of a transmission system for color television pictures. In a television camera 21, a multicolored light is received from an object through a lens 22 and the color of the object is separated into the three primary colors, i.e., red (R) light, green (G) light, and blue (B) light by use of a dichroic mirror unit 23. From these colors of light, primary color signals E.sub.R,E.sub.G,E.sub.B are then produced by image orthicon camera tubes 21R,21G,21B, respectively. A luminance signal E.sub.Y, representative of the brightness of the picture, and color signals having information as to hue and saturation values are reproduced from the primary color signals by a matrix circuit 24 are then transmitted. The color signals which provide the primary color signals E.sub.R,E.sub.G,E.sub.B when combined with the luminance signal E.sub.Y are color difference signals E.sub.R -E.sub.y,E.sub.G -E.sub.Y, E.sub.B -E.sub.Y. When such color difference signals are transmitted, the luminance signal E.sub.Y is added in the following manner at the reception side, thereby making it possible to reproduce the original primary colors. EQU (E.sub.R -E.sub.Y)+E.sub.Y =E.sub.R EQU (E.sub.G -E.sub.Y)+E.sub.Y =E.sub.G EQU (E.sub.B -E.sub.Y)+E.sub.Y =E.sub.B
As depicted in FIG. 4, the signals thus transmitted are received by an antenna 25. The desired channel is selected by a tuning circuit 26, so that the signals are amplified and converted into intermediate frequency signals. Video intermediate frequency (IF) signals which have been amplified at an intermediate frequency (IF) amplifier 27 are converted into video signals at a video signal detector 28. After amplification of the video signals at a video signal amplifier 29, the resulting signals are fed to a color picture tube 1. By electron beam scanning, a complete picture is formed from a series of video signals. Here, synchronizing signals transmitted along with the video signals are separated at a synchronous circuit 31 to control a horizontal and vertical deflection circuit 32, whereby the frequency and phase of the electron beam scanning are maintained consistent with those at the transmission side.
On the other hand, audio intermediate frequency (IF) signals are converted into audio FM signals at an audio signal detector and FM converter 33. The audio FM signals are converted further into audio signals by an FM detector 34 and a low frequency (LF) amplifier 35 and are then reproduced at a speaker 36.
The video signal amplifier 29 serves to amplify each luminance signal of the color television signals, which have been obtained at the video signal detector 28, to a level sufficient to activate the color picture tube 1. The video signal amplifier 29 is usually constructed of amplification circuits arranged in 3 to 5 stages and various auxiliary circuits.
To reproduce a color picture, the color picture tube 1 has to be fed with primary color signals. There are two types of manners for feeding these signals, i.e., the primary color drive system and the color difference drive system. FIG. 5 is a block diagram showing how primary color signals are produced and then fed to the color picture tube 1 in the primary color drive system. Primary color signals E.sub.R,E.sub.G,E.sub.B are applied at a negative polarity to respective cathodes 37-1,37-2,37-3 of the color picture tube 1, while respective first grids 38-1,38-2,38-3 are fed with a d.c. voltage.
The primary color signals are produced by adding the luminance signal and color difference signals at a matrix circuit 39. The matrix circuit 39 is inputted with the luminance signal E.sub.Y and color difference signals E.sub.R -E.sub.Y,E.sub.G -E.sub.Y,E.sub.B -E.sub.Y and produces as outputs negative primary color signals -E.sub.R,-E.sub.G,-E.sub.B. The negative primary color signals are then fed to the respective cathodes 37-1,37-2,37-3 of the color picture tube 1.
In the color picture tube 1, electron beams controlled by the primary color signals are caused to impinge exactly on color phosphors of red, green and blue colors, respectively, by way of a color sorting system, free of illustration, so that the phosphors are caused to glow to reproduce the color picture. The construction of the color picture tube 1 is illustrated in FIG. 6. The color picture tube 1 is basically constructed of three components, namely, an electron gun 61 for generating and directing electron beams, a shadow mask 62 for causing the electron beams to impinge only on phosphor dots of the designated colors, and a phosphor screen 63 coated precisely with red (R), green (G) and blue (B) phosphor dots in a predetermined pattern. Depending on differences in these components, color picture tubes can be classified into several types. Their details are however omitted herein.
Formation of a picture on a color picture tube is performed by left-to-right scanning (horizontal scanning) and up-to-down scanning (vertical scanning). The picture is successively and downwardly formed on the picture screen from the upper left corner. When the scanning has reached the lower right corner, the scanning returns again to the upper left corner. In this manner, 30 pictures, which are each divided into 525 lines, are formed per second. Accordingly, the horizontal scanning is repeated 15,750 times a second (525 lines.times.30 pictures) while the vertical scanning is repeated 30 times.
However, interlaced scanning is used in actual scanning. As a result, the vertical scanning is repeated 60 times. As illustrated in FIG. 7(a) and 7(b), interlaced scanning is performed by first coarsely scanning at some intervals as indicated by numbers 1, 2, 3 and 4 and then scanning once more between the first scanning lines as indicated by numbers 5, 6 and 7. The scanning of an entire picture is brought to completion by only these two vertical scanning operations. When interlaced scanning is performed, two coarse pictures of 262.5 scanning lines are sent successively to form a picture of 525 scanning lines. It therefore appears as if 60 pictures are sent out, although 30 pictures are actually sent out per second. It is hence possible to obtain pictures of little flicker.
As has been described above, the conventional television receivers have reached a technical level which is satisfactory from the practical viewpoint. It is, however, now strived to improve the dissolution further, for example, by increasing the number of scanning lines to 650 or 700 lines per screen or converting the signal processing circuits into their digital counterparts. In addition, high-definition television receivers have also been developed, as future television receivers, for commercial use.