Apparatus including a circuit arrangement for adjusting the color signal levels of a white dot

• US 4,136,360 A
• Filed: 10/14/1976
• Issued: 01/23/1979
• Est. Priority Date: 10/14/1975
• Status: Expired due to Term

• Current Assignee: Linotype-Hell AG (Heidelberger Druckmaschinen Ag)
• Original Assignee: Dr ING Rudolf HELL GmbH
• Inventors: Knop, Hans-Georg, Hoffrichter, Ingo
• Primary Examiner(s): Martin, John C.
• Application Number:
  US05/732,404
• Time in Patent Office: 831 Days
• Field of Search: 358/75, 358/76, 358/78, 358/80, 358/282, 358/280, 358/284
• US Class Current: 358/523
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence

Abstract

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.

Claims

1. Apparatus for adjusting the color signal levels of a white dot in reproduction of color original pictures with a scanning means, in which for each color separation a photo-electric converter and amplifier are provided, the amplification factor of the converter and/or the amplifier is adjustable by a control signal, wherein for each color signal component of a color separation a comparator is provided, having an actual value input and a desired value input, said actual value inputs of the comparators comprise the color signal components, said desired value inputs of the comparators are connectable through a transfer switch to the setting means of a constant voltage source for the adjustment of the color signal components to a common level corresponding to the level of said constant voltage source, and said desired value inputs are connectable, for adjusting the color signal components to values necessary for producing a true color reproduction, to a storage device containing said necessary values, wherein a desired value computer supplying inputs to the storage device and calculating the desired values from the actual values of the color signal components of the white dot and the white level, said computer is connected to the outputs of the amplifiers and to a constant voltage source, and wherein for each color signal component a voltage generator is provided, receiving the output of an associated comparator, each voltage generator during the adjustment of the color levels produces at its output a changing voltage as a control signal when unequal input values of the comparator exist, and, when the input values are equal locks onto and holds the instantaneous voltage value existing during reproduction.

3. Apparatus for adjusting the color signal component levels of a white dot in the reproduction of color original pictures with a scanning means having multichannel color reproductions means with each channel receiving and amplifying different color information and having independent gain control means, including a comparator receiving the different multichannel color information, an adjustable constant value source also supplying an input to said comparator, a voltage generator receiving a number of outputs from said comparator corresponding to the number of color channels and supplying a number of outputs corresponding to the number of color channels respectively to said gain control means of each channel, including a desired value computer receiving the different multichannel color information and said output of the constant value source, and switching means for disconnecting the output of said constant value source from said comparator and connecting the output of said desired value computer to said comparator.

2. Apparatus according to claim 3 wherein the desired value computer includes a maximum selection circuit for the color signal voltages, a divider connected to the maximum selection circuit and to said constant voltage source for the white level, said divider calculating a quotient from the white level and the maximum color signal voltage, and a plurality of multipliers corresponding to each color component signal voltage receiving the output of said divider and the color component signals, for the formation of the product from the quotient and the corresponding color component signal and wherein the outputs of said multipliers constitute the outputs of the desired value computer.

4. Apparatus according to claim 3 including a storage means connected between said desired value computer and said switching means.

5. Apparatus according to claim 3 wherein said voltage generator includes an upward-downward counter.