An apparatus adapted to sense a colorant and method for sensing color and detecting a donor mispick condition

摘要

An apparatus and method for sensing color of or colorant associated with an article. The apparatus and method is particularly suited for donor colorant detection and donor pick sensing in a thermal printer and for example employs N light sources of distinct wavelengths paired with N photosensors. Measured light values for a donor are combined to form an N-dimensioned coordinate value which is then compared against N-dimensioned reference values to determine a color or donor picking condition. The decision algorithm uses a decision rule based on Maximum Likelihood Decoding methods, whereby an Euclidean distance is computed between the measured N-dimensioned coordinate value and each of a set of reference N-dimensioned coordinate values. The apparatus and method detect which donor color has been picked and also detects and identifies multi-pick and pick failure conditions. <IMAGE>