System to test fabrics and the like, for color and/or sheen, uses a multi-spectral digital scanner to provide color data for comparison with the data from a positive image model

摘要

To test fabrics and similar materials, for color and/or sheen, data are prepared from a model as a digitized image for comparison with image measurements from the test materials. To test fabrics and the like, for color and/or sheen, a positive image model is placed on a table to be illuminated by a light of known spectral characteristics. The model is scanned by a digital camera, and preferably a multi-spectral camera system with a number of spectral filters at the lenses, and the photo images are digitized. A negative image is taken for each closed positive image channel. The model is replaced by the test fabric (1), and illuminated, to be scanned by a digital camera system (3) for the images to be digitized. The positive model values and the negative values in the digital fabric values are computed in a data processing system (9) to eliminate inconsistencies and the spectral characteristics of the light source, and generate a corrected image. All the digital values in the corrected image are averaged for each zone and channel. The mean values are used conventionally to reconstruct the reflection spectra of each zone in the digitized and corrected image, taking into account the spectral characteristics of the camera, the spectral filter, the positive model image and the illumination. The reflection spectra are separated for each zone with the spectral distribution of one or more types of light, and multiplied with the normal spectral curves corresponding to the spectral characteristics of the human eye, to be integrated into the visual range of the spectrum. The color values XYZ are converted into a visual color range e.g. CIELAB. The CIELAB values are compared with the CIELAB color values of a reference model, using a formula which brings the color intervals into a human recognition pattern. The mathematic formula uses DELTA-E, CIE94, CMC or CIE2000 systems, coupled to the color components giving color shades e.g. brightness, coloration, color tone. The color interval for one or more types of light and their part-components are compared with given tolerance thresholds, and a breach of a threshold generates a fault report. The colored patterns on fabrics are divided into color separations, to be measured separately for comparison with the reference model. The CIELAB color values and the reference model are stored in memory at the data processing unit. The positive model and the fabric are illuminated by a number of light sources. The spectral filters are inserted into the lens path in a set sequence. An Independent claim is included for an assembly to test a fabric, or similar material, for color and/or sheen, using a digitized image from a positive model for comparison with scanned images from the test fabric at a data processing unit.