DE1161949B - Color television receiver - Google Patents

Description

FEDERATION

GERMAN

EUTSCfÜAND kl. 21 a ¹ 34/31 INTERNAT. KL. H 04 Il

PATENT OFFICE

116194

REGISTRATION DATE: JULY 17, 1961

NOTICE THE REGISTRATION AND ISSUE OF THE EDITORIAL:

Γ 19W

In known color television transmission systems, for reasons of compatibility, a brightness signal (Y) containing the brightness information of the color image and a color signal containing two of the so-called color difference signals are transmitted in a known manner. In the NTSC system, for example, the so-called / and g signals, which contain the color information, are modulated onto a color carrier in quadrature modulation. The signals I and Q or RY, BY, GY are recovered at the receiver using synchronous demodulators. To synchronize the synchronous demodulation, the reference phase is also transmitted in the form of a color synchronous pulse. The phase position of the transmitted color carrier-frequency signal is a measure of the hue and the amplitude is a measure of the color saturation. Such a transmission system has the following disadvantage:

Since the path of the transmitted color carrier-frequency signal contains information, namely the hue, contains, the hue is caused by phase errors in the transmission path or by errors in the set Phase of the reference carrier falsified at the recipient. The so-called Differential phase error off; this is a dependence of the phase of the color carrier frequency signal on the level of the transmitted brightness signal. These errors cannot be eliminated by setting the Balance the phase of the reference carrier at the recipient.

To reduce the effects of such phase errors, it is known (U.S. Patent 2 943142), a modulation axis of the quadrature-modulated color subcarrier at the transmitter periodically changes 180 ° to switch and thereby the modulation direction or modulation phase of the color carrier frequencies Change vibration. A phase error occurring in the transmission path has an effect then in two consecutive time segments in opposite directions. When switching of the modulation axis takes place at a line frequency, two consecutive lines with written opposite wrong shade. The eye integrates over these two false hues and perceives the right color tone thanks to its integrating effect.

Such a method with phase switching is shown in FIGS. 1 to 3. In the counter-clockwise system according to FIG. 1, the carrier vector B is rotated to the left by the angle Φ _Β due to a phase error in the transmission path. This angle Φ _Β means a wrong color on the receiver. In the color television receiver

Applicant:

Telefunken

Patentverwertungsgesellschaft mb H.,
Ulm / Danube, Elisabethenstr. 3

Walter Bruch, Hanover,
has been named as the inventor

Right-hand system according to FIG. 2, the carrier vector C is rotated to the right by the angle Φ _α. The rotation in the two systems according to FIGS. 1 and 2 is the same, but points in the opposite direction.

In successive time segments, a color that is incorrect in the opposite direction is thus reproduced. According to FIG. 3, the eye integrates these two incorrect vectors B and C and takes the correct hue according to vector D. The color is only slightly changed in saturation by the amount AS , but this does not have a disruptive effect.

The invention is based on a receiver for a color television transmission system in which a Brightness signal and two color signals or color difference signals by modulating a color carrier two mutually perpendicular modulation directions are transmitted and in which the modulation directions or the modulation phases of the color subcarrier in the transmitter and receiver can be switched to the rhythm of the line frequency, and is marked by a beam sweep in the direction perpendicular to the line or by an electrical one Averaging over consecutive lines using a memory.

The invention improves the known system with phase switching in the sense that the integration effect is perfected over successive lines.

In a time division multiplex transmission system in which one broadband signal (green) is constant and two narrow-band color signals (red, blue) after

309 647/106

are transmitted to each other at frame or line frequency and also written one after the other on the screen it is known that the electron beams corresponding to the narrowband signals (Rotund BJau) to defocus or vertically to wobble to the Zeflerf. The electron beam for the broadband signal (green) remains sharply focused to maintain good resolution (Proceedings of the I. R. E., October 1951, p. 1326, para. 2, lines 13 to 20). But that is what it is a completely different transmission system in which different falbes are written one after the other. The disadvantages eliminated by the "wobble" are also of a completely different kind. This is known The solution should be the coarse line structure caused by writing different colors one after the other can be reduced and a softer image can be obtained. A color correction is not intended.

Claims (1)

PATENT CLAIM: Receiver for a color television transmission system in which a brightness signal and two color signals or color difference signals are transmitted by modulating a color carrier in two mutually perpendicular modulation directions and in which the modulation directions or the modulation phases of the color carrier in the transmitter and receiver are switched over to the rhythm of the line frequency by means of a beam wobble in the direction perpendicular to the line or by means of an electrical averaging over temporally successive lines using a memory. Considered publications:
U.S. Patent No. 2,943,142;
Electronics, February 1952, pp. 88 to 95;
Proceedings of the IRE, October 1951, p. 1326. 1 sheet of drawings