RESIDUAL INK MEASUREMENT

摘要

12 RESIDUAL INK MEASUREMENT A method and apparatus for detecting residual ink in a sample by illuminating by diffused infra-red light a series of spots on a sample and examining a small area on each spot by collecting light in a video camera to form a frame for each spot, digitizing each of the frame and detecting areas in the frames having a brightness below a selected level to determine the total dark area of each frame. The number of such frames processed in a set of frames used to categorize the sample is defined when a certain minimum number of frames have been processed and when a selected degree of convergence of the data collected for the set and the data from the frame currently being processed is obtained, or after a preset maximum number of frames have been processed. The sample is characterised on the basis of the ratio of the dark area to the total area processed.