Abstract: An apparatus and method for acquiring an image of a predetermined extract of a moving printed product employs at least one black-and-white camera with a two-dimensional electronic image sensor and one or more illumination devices suitable for pulse-like illumination. The illumination device has multiple light sources forming spectral groups that have different spectral compositions. The light sources are arranged in a pattern such that the light sources of each spectral group completely illuminate the area of observation of the camera. A control device switches the individual spectral groups of light sources on and off sequentially such that the area of observation of the camera is illuminated with a sequence of light pulses of different spectral compositions. During each light pulse, the predetermined extract on a printed product moves into the area of observation of the camera, and an image of extract is captured.

Abstract: A method for evaluating an image of a predetermined extract of a printed product makes corrections to a white reference to account for spatial variations and changes of illumination intensity over time. Intensity signals recorded from first predetermined areas within the extract are combined arithmetically with reference data values that represent a measure of the intensity of the light reflection from unprinted regions of the printed product. At the start, an image of a white reference is recorded and basic reference data for the entire extract are derived from the intensity signals of this image. During each evaluation of an image of the predetermined extract, correction data are derived from intensity signals recorded from second predetermined areas within the extract.

Abstract: An apparatus for acquiring and evaluating an image of a predetermined extract of a printed product removes the effects of scattered light to improve the accuracy of image evaluation. The apparatus uses a camera that has an electronic image sensor with a two-dimensional arrangement of sensor elements. An aperture stop is arranged in the beam path of the camera for shadowing a predetermined part of the image sensor. When an acquired image is read from a part of the image sensor that is not shadowed, corresponding readings from the shadowed portion of the sensor are subtracted from the acquired image to obtain intensity signals corrected for scattered light.

Abstract: An apparatus for acquiring and evaluating an image of a predetermined extract of a printed product removes the effects of scattered light to improve the accuracy of image evaluation. The apparatus uses a camera that has an electronic image sensor with a two-dimensional arrangement of sensor elements. An aperture stop is arranged in the beam path of the camera for shadowing a predetermined part of the image sensor. When an acquired image is read from a part of the image sensor that is not shadowed, corresponding readings from the shadowed portion of the sensor are subtracted from the acquired image to obtain intensity signals corrected for scattered light.

Abstract: An apparatus and method for acquiring an image of a predetermined extract of a moving printed product employs at least one black-and-white camera with a two-dimensional electronic image sensor and one or more illumination devices suitable for pulse-like illumination. The illumination device has multiple light sources forming spectral groups that have different spectral compositions. The light sources are arranged in a pattern such that the light sources of each spectral group completely illuminate the area of observation of the camera. A control device switches the individual spectral groups of light sources on and off sequentially such that the area of observation of the camera is illuminated with a sequence of light pulses of different spectral compositions. During each light pulse, the predetermined extract on a printed product moves into the area of observation of the camera, and an image of extract is captured.

Abstract: A method for evaluating an image of a predetermined extract of a printed product makes corrections to a white reference to account for spatial variations and changes of illumination intensity over time. Intensity signals recorded from first predetermined areas within the extract are combined arithmetically with reference data values that represent a measure of the intensity of the light reflection from unprinted regions of the printed product. At the start, an image of a white reference is recorded and basic reference data for the entire extract are derived from the intensity signals of this image. During each evaluation of an image of the predetermined extract, correction data are derived from intensity signals recorded from second predetermined areas within the extract.

Abstract: Information is received from an image on a moving substrate. Flash exposure is used, defining operating or exposure cycles. The reflection or a representation of the image is subdivided into a matrix having n columns and m rows or lines. The sensor is a charge coupled device (CCD), arranged to have a sensing area (11) with n columns and m rows or lines, and a storage region or section (12), likewise arranged to have storage cells of n and m columns and rows or lines. Information of any one image element, upon sensing, is shifted by a line transfer pulse by one image line. The line transfer pulses are synchronized with web movement of the substrate and operate as shift pulses. The m line, at the first transfer line shift pulse, is shifted into the first line or row of the matrix of the storage portion of the CCD. For each operating cycle, at least one line transfer pulse is used. The information of the image elements can be read out serially from the storage portion (12) at high speed.