Abstract: A method and an arrangement for generating a composite video signal in accordance with the chroma-key method in which a virtual background spill signal is generated and added to the composite video signal to avoid darkening effects which are produced when eliminating spill light, and to eliminate brightening effects which are produced in "clean-up" operations. The background spill signal may consist of the product of a virtual spill signal source (SP) and a control signal (k.sub.3). The control signal (k.sub.3) is preferably the difference between a foreground control signal (k.sub.1) and a background control signal (k.sub.2), and both signals should be identical in the foreground and background ranges but different in spill ranges.

Abstract: A chromakey method and an associated circuit arrangement are intended for treating transition colors in color keying in which transition colors occur in video pictures, for example at the edges between foreground objects and the key color of the background of these objects. For the proposed treatment of the transition colors, inter alia the keying function (k) plays a decisive role. It indicates the key color component for each transition color. To define this keying function (k), parameters are applied to a computer (C), which parameters fix a key color (.vertline.KC.vertline.,.theta.,.PHI.), a transition color (Cb, Cr, Y) and a boundary region (.alpha.,.beta.). In the color space, the boundary region separates the color of the foreground of a video picture from all other colors which may occur in the video picture. The keying function (k) is determined by way of the equation for the boundary.

Abstract: In a method of inserting a background picture signal into key color-characterized parts of a foreground picture signal, the selectivity, i.e., the boundary between its foreground colors and the transition or mixed colors degenerated by the key color should be changeable within a frame period by means of masking. This provides the possibility of differently keying equal colors of different origin occurring in a picture--as a pure foreground color, on the one hand, and as a mixed color, on the other hand--namely, by dynamically switching the selectivity within a frame period by means of the chroma angle .alpha..sub.c.

Abstract: A method and a circuit for generating a composite video signal formed from a foreground signal and a background signal in accordance with the luminance self-key mode is described, in which the key signal is derived from the luminance foreground signal in dependence upon a clipping level. To avoid a quadratic dependence of the luminance signal during product formation of the key signal with the foreground signal (referred to as "double multiplication"), the linear key signal should be replaced by a control signal which is hyperbolically formed in such a way that the unwanted quadratic dependence is eliminated.

Abstract: In a chroma-key method for inserting a background picture signal into key color-characterized key regions of a foreground picture signal, in which method fading operations are performed between the picture signals in proportional zones in dependence upon a control signal, while intermediate colors occurring in the proportional zones in the foreground signal are transformed into new intermediate colors which constitute a transition from the color of the foreground picture signal to that of the background signal, an optimal adaptation of the proportional zone to the respective color location of a foreground picture signal region is ensured in that individual proportional zones for regions of different color locations in the foreground picture signal are fixed in such a way that the distance between the color location of each region and the color location of the key color is determined individually for each region, and in that the control signal is generated for each region in dependence upon the color location

Abstract: In a method of separating a foreground picture signal FG from a mixed picture signal MG which has a key color KC as well as transition colors to this key color in key regions, the foreground picture signal is removed from the key color and the transition colors in accordance with the equationFG=MG-k*KC.Herein, k is a control signal which has a value of about 1 in the region of the key color KC and a value of about 0 at the transition boundaries. The transition boundaries in the C.sub.b /C.sub.r color plane are constituted by two straight lines through the origin of the C.sub.b /C.sub.r, color plane which, relative to a vector D.sub.KC of the key color extending from the origin of the C.sub.b /C.sub.r color plane to the color location KC of the key color, are arranged at angles .omega..sub.o and .omega..sub.u, respectively. The straight lines through the origin of the C.sub.b /C.sub.

Abstract: In a method of separating a foreground picture signal FG from a mixed picture signal MG having a key color KC and transition colors to this key color in key regions, the components of the key color and the transition colors are vectorially subtracted from the mixed picture signal in dependence upon a control signal k which, with a continuous variation, assumes values of between 1 in the region of the key color KC and O at mixed boundaries. Color errors due to a gamma pre-correction are obviated in that the vectorial subtraction is performed in accordance with the equation FG=MG-k*KC(f), in which KC(f) is chosen in dependence upon the color intensity as far as its angle in the C.sub.b /C.sub.r color plane is concerned.

Abstract: A method of inserting a background signal (BG) into parts of a foreground signal (FG), which parts are fixed by a predetermined key color (KC), in which method a control signal (k) is derived from the foreground signal (FG), which control signal assumes a first value when the foreground signal (FG) represents a color in the region of the key color (KC) and a second value when the foreground signal (FG) represents a different color, in which the control signal (k) has a transition range between the two values, and in which a difference, influenced by the control signal (k), between the vector of the background signal (BG) and the vector of a signal (KC) representing the key color is vectorially added to the foreground signal (FG) in accordance with Patent (U.S. patent application Ser. No. P 41 43 180.4), as well as an arrangement for performing this method.

Abstract: In a method of and an arrangement for inserting a background signal into parts of a foreground signal fixed by a predetermined key color, in which a control signal is derived from the foreground signal, this control signal assuming a first value when the foreground signal represents a color in the region of the key color and a second value when the foreground signal represents a different color, and in which the control signal has a transition range between the two values, a difference, influenced by the control signal, between the vector of the background signal and the vector of a signal representing the key color is vectorially added to the foreground signal.

Abstract: In a method, in which a control signal assumes a first value when the foreground signal represents a color in the region of the key color and a second value when the foreground signal represents a different color, and in which the control signal has a transition range between the two values, the distances between the color locations of the pixels of the foreground signal and the color location of the key color are computed for distinguishing color locations associated with foreground objects or with the key color from color locations to be associated with the transition range. Those color locations whose distance is distinguished from color locations of one or a plurality of adjacent pixels by more than a predetermined distance (not complying with a homogeneity criterion) are considered to be associated with the transition range. Intermediate values of the control signal are computed for the color locations in the transition range.

Abstract: With the signal electrode of a camera tube uniformly illuminated by diffuse light, scanning of the signal electrode by the electron beam is caused to leave unaffected certain lines or parts of lines which are scanned in the next frame. This may be done by blanking the beam out for a field, a line or part of a line in every two frames, or by shifting the lines of one field to superimpose them on those of the other field for a corresponding interval in every two frames. The video signal occurring when a previously unscanned line or line portion is first scanned is measured and compared with the previous measured value, in response to which the setting of the focussing control is shifted towards a smaller beam spot for a renewed measurement. When the signal rises to a higher magnitude, which would approximate twice the video signal of a normal scan, in the ideal case, the setting procedure is complete.

Abstract: Dynamic beam current reserve margin in television camera tubes necessary for the neutralizing of bright spots, which is accumulated on the camera tube signal electrode during a multiplicity of successive picture field periods after which a signal electrode is scanned by the electron beam during several field periods in interlaced line pattern and the video signal level of the third field is measured. In this measurement, the signal level is below a first predetermined threshold value, the dynamic beam current reserve is sufficient and the procedure is terminated. The threshold is reached or exceeded, the dynamic rise of the beam current is gradually magnified and further cycles of charge and scanning are performed, this time with measurement of the video signal during the second field.

Abstract: The signal electrode of a television camera tube by first scanning in an odd-numbered picture field is focussed in horizontal scanning pattern and then superimposing thereon in an even-numbered picture field the scanning pattern offset out of interlace and rotated slightly while at the same time the focussing current for the focussing coil of the electron beam is slightly altered for the even-numbered picture field. Charge patterns with charge maxima are thereby produced in the unscanned zones. The actual alignment is determined by the focus pivot point F that lies in a strip of maximum charge values running obliquely across the scanning pattern. Increasing the focussing current produces, simultaneously, rotation to the left and enlargement of the scanning pattern, resulting in a maximum charge value strip running from upper left to lower right (patterns a, c and e).

Abstract: A process for avoiding non-linearities and brightening on the television picture tube includes the generating of an additional signal of a higher frequency than that of the deflections signals, the separating of the additional signal into signal parts of opposite polarity, and the addition of the two additional signal parts to the deflection signals during time intervals immediately before and after the return movement period.

Abstract: A first regulating amplifier (7) provides a linearly increasing current to the horizontal deflection coil during the forward trace sweep and the amplifier is disconnected from the deflection coil and its parallel capacitor (2) during the retrace period to provide flyback by free reaction of the oscillating circuit. In order to shorten the retrace period an auxiliary coil (17) is energized with a regulated current during the forward trace sweep with the help of a second regulating amplifier (8) gated on during a preliminary portion of the line interval and a controllable voltage source (14) set thereby. During a first portion of the retrace interval currents flowing respectively in the auxiliary coil and in the horizontal deflection coil are stored in the capacitor (2), which discharges during the remainder of the retrace period only through the deflection coil.