COLOUR VALUE MEASUREMENT

摘要

Light from e.g. a halogen lamp (2) is guided through a fibre (3) to an annular distributor (4) directing a conical or convergent beam (20, 21) through a window (23) on to the sample (22). The reflected light is detected by e.g. a Si photovoltaic cell (5). The light beam is chopped periodically by a disc (6) which is rotated by a motor (28) and comprises an open quadrant, a black reference quadrant and two colour reference quadrants comparable with the sample (22). The ratio of the intensities of reflections from the black and colour references is subtracted (16) from that of reflections from the sample and colour reference.