Abstract: An illumination device for a spectral optical measurement device includes arranged with respect to an optical axis of the illumination device which, during a measurement operation, extends along a normal to a center point of an area of a sample to be illuminated. One or more segments of a mirror in a shape of a ring are centered on the optical axis. The mirror has an internal reflective surface arranged such that, during the measurement operation, the internal reflective surface receives light emitted from the light source and reflects the light over the area of the sample to be illuminated. The internal reflective surface has a freeform shape in a cross-section through the internal reflective surface in a plane parallel to the optical axis (for example in which the optical axis lies), and, in a cross-section of the mirror in a plane perpendicular to the optical axis, the internal reflective surface is represented by a straight line.

Abstract: An illumination device for a spectral optical measurement device includes arranged with respect to an optical axis of the illumination device which, during a measurement operation, extends along a normal to a center point of an area of a sample to be illuminated. One or more segments of a mirror in a shape of a ring are centered on the optical axis. The mirror has an internal reflective surface arranged such that, during the measurement operation, the internal reflective surface receives light emitted from the light source and reflects the light over the area of the sample to be illuminated. The internal reflective surface has a freeform shape in a cross-section through the internal reflective surface in a plane parallel to the optical axis (for example in which the optical axis lies), and, in a cross-section of the mirror in a plane perpendicular to the optical axis, the internal reflective surface is represented by a straight line.

Abstract: A hand-held measurement device for appearance analyzes includes a measurement array which comprises a number of illumination means for applying illumination light to a measurement field in at least three illumination directions and a number of pick-up means for capturing the measurement light in at least one observation direction. The illumination directions and the observation directions lie in a common system plane. At least one pick-up means is embodied to spectrally gauge the measurement light in a locally integral way, and at least one imaging pick-up means is embodied to gauge the measurement light in terms of color in a locally resolved way. The spectral pick-up means and the locally resolving pick-up means are arranged such that they receive the measurement light reflected by the measurement field under the same observation conditions and in particular from the same observation direction.

Abstract: A hand-held measurement device for appearance analyses includes a measurement array which comprises a number of illumination means for applying illumination light to a measurement field in at least three illumination directions and a number of pick-up means for capturing the measurement light in at least one observation direction. The illumination directions and the observation directions lie in a common system plane. At least one pick-up means is embodied to spectrally gauge the measurement light in a locally integral way, and at least one imaging pick-up means is embodied to gauge the measurement light in terms of colour in a locally resolved way. The spectral pick-up means and the locally resolving pick-up means are arranged such that they receive the measurement light reflected by the measurement field under the same observation conditions and in particular from the same observation direction.

Abstract: For the color measurement of samples printed on a substrate including a brightener, a raw spectral reflection factor of the sample is measured in a first measurement by illumination of the sample with light without UV portion. In a second measurement, a fluorescence spectrum of the sample is measured by illumination of the sample with only UV light. The measured fluorescence spectrum is recalculated as a corrected fluorescence spectrum by weighting with spectrally dependent correction factors and, finally, the measured raw spectral reflection factor and the corrected fluorescence spectrum are added to form a corrected spectral reflection factor from which the values characterizing the color of the sample are then calculated. The spectral correction factors are determined during the device manufacture for a certain set of light types and stored in the device.