Robert Boschgmbh

Bts Broadcast Television Systems Gmbh

Heinz Hess

Horst Peth

Michael Hausdorfer

Reinhard Kirschenstein

When two color television standards prescribe the same horizontal scanning frequency but different color carrier frequencies, one of them, for example, requiring a frequency providing a one-half line offset to the horizontal scanning frequency (NTSC Standard) and the other requiring a three-quarter line offset (PAL-M Standard), each color carrier frequency being locked to the common line frequency, a modified phase locked loop circuit makes it possible to synchronize the color carrier frequencies to each other. The oscillator at the color carrier frequency of one standard has its output compared, in a phase comparison stage, with the color synchronization signal of the other standard. The output of the phase comparison stage is supplied to a sample-and-hold circuit which is sampled during the presence of that color synchronizing signal in every fourth line. The content of the sample-and-hold circuit is passed through a low-pass filter and then supplied to the control input of the oscillator, thus locking the latter to the color carrier of the other standard.

Synchronization of color carriers of different color TV standards having

To simplify the apparatus and the method steps to reestablish predetermined phase relationship of a chrominance TV signal with a reference, two chrominance derived signals of carrier frequency, respectively phase shifted by plus and minus 45.degree. with respect to the carrier frequency are obtained; chrominance derived signals, likewise phase shifted with respect to the input chrominance signal, are amplitude modulated with set voltages, and the amplitude modulated chrominance derived signals are so added that the phase position of the resulting chrominance signal will match that of the reference carrier.

Method to reestablish a predetermined phase relationship of a

To control the amplitude of color difference signals (R-Y, B-Y), a circuit is formed by two transistors each receiving matrixed color difference signals at their emitters, the base electrodes of one of the transistors (14, 16) being connected to a source of reference voltage and the base electrodes of the other of the transistors (13, 15) being connected to a common controlled source of voltage (U.sub.G, 18) The color difference signals are then available at the collectors of the second transistors (13, 15) under controlled conditions.

Circuit arrangement for matrixing three chroma signals to obtain color

Circuit for changeable prolongation of the running time of an ultrasound

The invention concerns a method and apparatus for mixing a foreground signal and a background signal under the control of a switching signal which is derived as a function of the color of the foreground signal. In response to the switching signal selected parts of the foreground signal are desaturated while maintaining their luminance component substantially unchanged; non-corresponding parts of the background signal are suppressed. Both signals so treated are additively superimposed. This leads to a better representation of fine details in the contours of a foreground object of interest.

Method for mixing two color television signals

Method and apparatus for comb filtering NTSC type television signals is described. The television signal is delayed by one line period, the delayed and the undelayed television signal are averaged. The resulting signal is delayed again by one line period and the delayed and the undelayed resulting signals are averaged, too. The result of the second averaging on the one hand is the luminance signal and on the other hand is subtracted by the television signal delayed by one line period. The result of such subtraction is the chrominance signal.

Comb filtering for NTSC television signals

To obtain an aperture correction signal with improved signal-to-noise ratio and having steep flanks with low harmonic content, the video signal is twice differentiated to obtain the second differential (C), and is also once differentiated to obtain the first differential (B), which is squared, the squared first differential and the second differential being multiplied and the product, after phase-matching by inversion, is applied as a correction signal (F), additively, in an adder (11) to the video signal (A) to form an aperture corrected output signal (G). Prior to the addition step, the video signal is time delayed to compensate for delays in the signal processing stages (4, 6, 7, 8) of the system (2).

Method of generating a video aperture correction signal

A contrast correction signal is generated to compensate for the limited contrast range of known image converters. The one of the primary color signals having the highest luminosity is low-pass filtered, its amplitude indicative of darker picture portions boosted, by use of a nonlinear amplifier, the resultant signal is subtracted from a blanking signal which has been subjected to the same nonlinear amplification and the resultant difference signal is multiplied by the composite television signal. The multiplier output constitutes the correction signal which is added to the composite color television signal. The method and system are illustrated with respect to the PAL, NTSC and SECAM systems.

Method and system for contrast correction of color television signals

A process and two embodiments of an apparatus are disclosed for displaying, on the screen of a conventional home television receiver, curves illustrating analog signal potential functions of the form U(x,y). The process generally requires generating first and second saw-tooth signals synchronized with the vertical and horizontal sync. signals of the picture raster of the home television receiver. At least part of each of the signal potentials U.sub.y and U.sub.x are then compared with the first and second saw-tooth signals to generate first and second impulse signals respectively when equal potential conditions are observed. The first impulse signal is then differentiated with respect to time to form a gate impulse signal of adjustable width for controlling the processing of signal potential U.sub.x. The second impulse signal is differentiated with respect to time to form a brightness control signal for output to the home television receiver.

Functional curve displaying process and apparatus

Each one of plural SECAM color-T.V. signals to be mixed is processed as follows: the signal is split into a luminance component and a video-frequency color component; the color component is amplitude-modulated onto a carrier, and the thusly modulated carrier is superimposed onto the respective luminance component to yield a frequency-multiplex signal which is then applied to one respective input channel of a mixer. The output signal of the mixer is split into a mixed luminance component and an amplitude-modulated mixed color component. The latter must be amplitude-demodulated, and then is frequency-modulated and superimposed onto the mixed luminance component to yield the desired mixed SECAM color-T.V. signal. Suppressed carrier amplitude-modulation is used, and each original video-frequency color component has superimposed, during the horizontal blanking intervals, reference oscillations from the carrier used for amplitude-modulation. The carrier signal needed by the amplitude-demodulator is derived from or furnished in dependence upon the amplitude of the reference oscillations in the horizontal blanking intervals of the amplitude-demodulated mixed color component, the reference oscillations having a phase which differs by 90.degree. from the phase which the carrier signal used for amplitude-modulation has outside the horizontal blanking intervals.

Method of mixing SECAM color-T.V. signals

This invention concerns a circuit arrangement for visually representing a horizontal frequency coupled input signal on the picture screen of a video display device such as a domestic television receiver. This is achieved by comparing the input signal to be represented in visual form with a vertical frequency sawtooth signal, the comparison being effected in such manner that a further signal is produced which identifies the moments when the two compared signals are equal. The further signal is then used directly or indirectly to control the brightness of the picture screen of the video display device. The further signal may be a pulse form signal with the leading flanks of the pulses corresponding to moments when the input signal crosses the sawtooth signal upwardly and the trailing flanks corresponding to the moments when the input signal crosses the sawtooth signal downwardly. The further signal is preferably differentiated prior to application to the display device.

Video display

The red, green and blue color signals are, respectively, applied to the base of three transistors, each connected as a common emitter stage. A constant current source has an output terminal connected to that side of the emitter resistors not connected to the respective emitter. The conductivity of the emitter resistors is proportional to the coefficients in the equation Y=k1.sup.. R+k2.sup.. G+k3.sup.. B where Y is the luminance signal. For the system, the color difference signals are then derived from the collector of the emitter follower stage receiving the red and green signals and the luminance signal is derived at the constant current output terminal. For the NTSC system, the same signals are derived from the same terminals, but an additional coupling resistor is added between the emitter of the transistor receiving the blue signal and the other two emitters.

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Weiterstadt, Germany

Heinz Hess