Robert Boschgmbh

Bts Broadcast Television Systems Gmbh

Reinhard Kirschenstein

Heinz Hess

Wolfram Klemmer

A tri-level HDTV synchronizing pulse signal is compared with first and second reference voltages to provide pulse signals respectively containing the positive and negative pulse of the tri-level signal. A blanking signal is also derived that provides blanking after each H synchronizing pulse for more than half a line duration. It is used in correlation with the separated positive pulses of the tri-level signal to produce H frequency synchronizing pulses. The blanking signal and also another pulse signal are generated by a four bit counter which is clocked by a clock signal having four times the H frequency and has the logic 1 voltage applied to that input of the counter where it will signify the binary number 4. These signals make possible the derivation of both a picture field synchronizing pulse of vertical scanning frequency V and a frame synchronizing signal of half that frequency, a pair of D-flipflops being used to provide these outputs. The first reference voltage may be ground potential if a slightly delayed output of the separated negative pulses is used to blank out the intervals between the separated positive pulses.

Method and circuit for deriving H and V synchronizing pulses from a

A gamma stage of a television camera is automatically provided with regulation removing effect of variations in temperature, supply voltage and the like by means of two series of control pulses added to the video signal in blanking intervals of the signal before processing by the gamma stage. One series of pulses inserted in the horizontal blanking intervals, is compared after passing through the circuit with a reference value in a gated comparison amplifier providing a constant voltage output for the duration of a horizontal scanning interval, which is utilized to correct the d.c. offset of the video signal before it enters the gamma stage. Another set of control pulses inserted in the vertical blanking intervals is supplied to a gated comparison amplifier to produce an output signal that remains constant for a vertical scanning interval, which is used to provide a multiplicative correction to the output of the gamma stage for controlling the amplification of the circuit as a whole. The output of the multiplicative correction stage proceeds to the usual circuit for d.c. level clamping in the horizontal blanking intervals to produce the output available for further processing, which is also utilized by the comparison amplifiers for regulation purposes.

Method and circuit for nonlinear transmission-processing of a video

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.

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Rossdorf, Germany

Reinhard Kirschenstein