Patent ID: 6956645

Claim:
An apparatus for measuring an optical property of a quantity of polymer applied by a printing device onto a support and correcting the quantity of polymer applied, comprising: a source of radiation to irradiate a droplet of polymer solution or polymer dispersion during a printing process, the source including at least a primary beam; a detector of radiation, which is arranged in relation to both the source of radiation and the droplet in such a way that the detector receives either radiation re-emitted by the droplet or radiation transmitted through the droplet at a time at which the droplet is capable of being imprinted with a subsequent droplet and before a boundary surface forms between the droplet and the subsequent droplet; and a control unit configured to cause a printing device to print the subsequent droplet when the detector detects the droplet as having less than a desired quantity of polymer, wherein the subsequent droplet is printed on the droplet before the boundary surface forms.