Reference colour recognition device - has filters to select reference colour and compare intensity with preset level

摘要

The colour recognition device for detecting a reference colour in colour printing, or detecting coloured indicators uses a filtering method. The first optical filter (F1) receives the light emitted by the object and has a transmission band in the wavelength of interest. A second optical filter (F2) selects a band not including the wavelength of interest. Detectors (C1, C2) measure the two outputs from these filters, and the difference between them is found. The difference signal is then compared with a present value to determine the presence of the reference colour of light.