Facsimile and static presentation processing – Facsimile – Recording apparatus
Patent
1993-09-03
1996-11-19
Rogers, Scott A.
Facsimile and static presentation processing
Facsimile
Recording apparatus
3582613, 358427, 358429, 358539, H04N 141, H04N 1415, H04N 1419
Patent
active
055768350
DESCRIPTION:
BRIEF SUMMARY
This is a continuation of International Application PCT/EP92/029977 with an international filing date of Dec. 12, 1992 published as WO93/04572 Mar. 18, 1993.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is concerned with the coding and transmission of images and patterns, and, more particularly, to the coding and transmission of information for telefax and for television, especially color television.
2. Description of the State of the Art
Facsimile equipment is split into standard groups in accordance with the transmission time. Groups 1 and 2 with point by point scanning have already been superseded by Group 3 equipment. The latter represents a digital transmission system in which the picture scanning points of equal brightness are brought together in an unbroken sequence and combined into a code word. Such methods are known as one-dimensional. The MHC method is an example of such a one-dimensional method. The two-dimensional process is built up on the same principle. In this case a reference line is first scanned and in the subsequent lines only departures from the reference line are coded. The MRC method operates in accordance with this principle. Then there is the MMR code, in which after a coded reference line a large number of subsequent lines are coded two-dimensionally. In run-length coding, for each number of picture points per line, a special binary code is determined for white and black, eg., 1 white=000111, 1 black=010, 2 white=0111, 2 black=11, . . . 20 white=0001000, 20 black=00001101000. Such coding goes up to picture point number 63. Then one starts again from the beginning with an additional section code word for white and black. For transmitting these coded numbers a phase-difference or amplitude-phase-difference modulation technique may be employed.
In gray-scale scanning, the gray values are divided into gray steps and converted in more or less close patterns of black and white dots. In this way, as is known from the Dither printing process, a corresponding gray step is taken in by the eye. In the coding of color images and patterns expensive processes have hitherto been necessary. To some extent similar to the coding in the NTSC, PAL and SECAM systems.
SUMMARY OF THE INVENTION
A drawback of these known methods is in facsimile the relatively long time taken up for transmission and the large outlay for coding and the necessary large bandwidth, in particular in the coding and transmission of color images. As hitherto several carriers were required in color transmissions, distortion by mutual interference, such as for example cross color, cross luminance, have arisen.
The aim of the invention is to provide such a coding that the information can be transmitted in a shorter time period than hitherto, but with at least the same transmission security. This is attained in that the run length coding in numbers or digits for black and white takes place by means of the same code words for different numbers or digits. This is possible because the pick-up sequence black/white is used as a criterion. A further shortening of the time during the coding of white lines is therefore possible in that the respective coded number of the white lines is disposed ahead of or behind the marker for "white line". During color transmission a savings in time and effort is achieved by means of multiplex-code coding.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an overall representation of a facsimile equipment.
FIG. 2 shows an alternating current code in which the characteristic states are marked by the amplitudes of the half-waves. Multi-value coding is achieved by two alternating currents, displaced in phase by 90 degrees, and added together for transmission.
FIG. 3 shows a multi-value alternating current code in which several added alternating currents are provided, of which the frequency always lies half the frequency higher than the primary alternating current.
FIG. 4 shows an alternating current code in which the coding is determined by the duration of the cycles and the a
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