Dr. Ing. Rudolf Hell Gmbh

Rudolf Hell Gmbh

Ingo Hoffrichter

Hans-Georg Knop

Eggert Jung

Hans Keller

A method and circuit arrangement for selective correction of hues and colors in the production of color separations for polychromatic mixed printing. A hue signal identifying the hues of the scanned colors as well as a color saturation signal and a luminance signal are derived from the measured color value signals acquired when scanning the original. Hue signals, color saturation signals and luminance signals are limited such that they are respectively not equal to zero only for selectable regions. The region of the hue signal defines a hue to be selectively corrected, and all three regions of the signals define a color to be selectively corrected. At least one of the limited signals is combined with at least one of the unlimited signals to form the selective correction signals which are superimposed on the color signals to be corrected.

Method and circuit arrangement for selective correction of hues and

In electronic reproduction technology, a method and an apparatus for the production of hue and color separations for single color printing. A color original is optoelectronically scanned to obtain measured color value signals. A recognition region for a selected separation hue is defined in a recognition circuit. A hue recognition signal, which is a measure for the hue deviations of the hues scanned in the color original from the selected separation hue, is generated from the measured color value signals. Corrected color signals are derived from the measured color value signals and at least one corrected color signal is selected for further processing. A recording signal is acquired in a mixer stage by mixing the selected color signal and the hue recognition signal. The recording signal controls a recording element for recording of the hue separation. When color separations are to be produced, a recognition region for a selected separation color is defined and a color recognition signal is generated and mixed with the selected color signal to obtain the recording signal which controls the recording of the color separation.

Method and apparatus for the production of color separations for single

In electronic reproduction technology, a recognition circuit for hues and colors in colored surfaces is provided. Before the actual hue recognition, the hue to be recognized is selected and its prescribed or measured color values of the RGB color space are transformed by a first color transformation into chrominance values of the chrominance/luminance color space, whereby the transformation coefficients are defined such that the transformed color locus of the hue to be recognized lies on a rotated X'Y' color coordinate system in the chrominance plane. During the actual hue recognition, the colored surface is opto-electronically scanned and the measured color values acquired are transformed into chrominance values by a second color transformation with the transformation coefficients defined in the first color transformation. By selection of chrominance values and by quotient formation of the selected chrominance values, a hue signal which is a measure for hue deviation of the scanned hues from the hue to be recognized is generated. After combination of the hue signal with an auxiliary control signal, a hue recognition signal is formed, this being unequal to zero when the scanned hues lie within a sector-shaped hue recognition region. For color recognition, a color saturation signal and a luminance signal are additionally generated. The color saturation signal and luminance signal are adjustably limited in terms of amplitude and are combined with the hue recognition signal to form a color recognition signal.

Method and apparatus for the recognition of hues and colors

In an apparatus and a process for obtaining image signals, and electronically mixing the image signals to generate mixed signals, the steps include modulating one of the image signals with the control signal, amplitude-inverting the control signal, modulating the other image signal with the amplitude-inverted control signal, and adding a modulated image signal so as to obtain the mixed signal. The control signal has prearranged characteristics determining the commencement and at least partly the characteristic of the modulating step.

Apparatus for mixing image signals to obtain a printing master

Apparatus including a circuit arrangement for adjusting the color signal levels of a white dot in dot and line-wise reproduction of color picture patterns with a scanning instrument and in which for each color includes a photo converter for obtaining a color signal voltage and further including amplifiers receiving the output of each of the converters and wherein the gain of the converters and/or the amplifier are adjustable by means of a control signal through a regulating device. The circuit arrangement can be used not only in color scanners but also in black-white scanners.

Apparatus including a circuit arrangement for adjusting the color signal

In the scanning and reproduction apparatus, the signal level of the 'black point' or darkest portion of an image, is automatically adjusted without disturbing the previously adjusted white level, by placing a level adjusting circuit in the signal path between the scanner and the reproduction device and including in the adjusting circuit elements affecting a decrease of the operational signal from black to white thereby avoiding disturbing the white level, and wherein the derived image signal of the darkest image portion or 'black point' is checked against a reference signal as the scanning proceeds, and also checked for coincidence with the reference signal.

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Kiel, Germany

Ingo Hoffrichter