Abstract: In a digital full color copying machine, image signals of red, green and blue are converted to a value signal, and histograms of the value signal for chromatic dots and achromatic dots respectively are generated. Then, a document type, such as a color standard document, a color photograph document, a color standard document having a colored background, a black-and-white standard document, or a black-and-white photograph document, is determined automatically based on the histograms. Background level of a copy is controlled automatically at an appropriate level both for a color document and for a black-and-white document having a white background according to the document type by gradation correction of the value signal. Thus, background processing is performed irrespective of a color document or a black-and-white document.

Abstract: When a monochromatic image is reproduced, a user can select desired mixing coefficients of red, green and blue in order to control gradation data for the reproduction of a monochromatic image as well as a monochromatic reproduction color. When a document is automatically determined not to be a color document, the mixing coefficients of red, green and blue are changed according to the type of the document. If a monochromatic copy mode is selected, the mixing coefficients can be set manually. Preferably, in order to help a user to select mixing coefficients, a plurality of images of monochromatic colors of various mixing coefficients of red, green and blue can be printed on a single sheet of paper.

Abstract: An image reading apparatus comprises a photoelectric converter including three linear image sensors of red, green and blue aligned in parallel to each other along a main scan direction. When a document is scanned, a document is read by the photoelectric converter by moving it relative to the document. The moving direction is set to be a first direction, for a prescan and a second direction reverse to the first direction, for a normal scan. Analog output signals of the first to third linear image sensor are converted to digital signals. In a prescan, a selector exchanges the digital signals of the first and third linear image sensors, while in a normal scan, the selector does not exchange them.

Abstract: The present invention is intended to improve the mass-productivity of equipment having magnetic bearings at the time of its manufacture, and to facilitate after-sale service of equipment having magnetic bearings after the time when either of a magnetic bearing control apparatus and a structure having a rotor has gotten out of order and is exchanged or repairs. In the magnetic bearing arrangement according to the present invention, due to the fact that a portion (a central position (off-set) regulator 8, a positional feedback gain adjuster 9 and a filter 10) of control elements of a magnetic bearing control apparatus 1 is placed outside the magnetic bearing control apparatus 1 as such, for instance, inside the structure having the magnetic bearing, some factors restricting the interchangeability between the magnetic bearing control apparatus 1 and a structure (such as a casing) 2 having a rotor are eliminated.