Fountain solution thickness measurement system and method using ellipsometry

A method of controlling fountain solution thickness on a non-reflective imaging member surface of a rotating imaging member, comprising:

• (a) applying a fountain solution fluid layer at a dispense rate onto the imaging member surface, the imaging member surface being non-reflective with a reflective substrate attached to the non-reflective imaging member surface at non-image forming regions along a gutter of the imaging member surface outside a imageable area of the imaging member surface to form a reflective surface on the otherwise non-reflective surface, the fountain solution fluid layer being dispensed on both the reflective surface and the non-reflective surface at the fountain solution dispense rate with a fountain solution applicator;
• (b) measuring a light reflectance from the reflective surface having the fountain solution fluid layer thereon with a light reflectance detector spatially separate from the imaging member surface and forming a gap therebetween;
• and
• (c) modifying the fountain solution dispense rate via controller in communication with the light reflectance detector and the fountain solution applicator based on the measured light reflectance.

An image forming device for controlling a fountain solution dispense rate, comprising

• a rotatable imaging member having an imaging member surface that is non-reflective over an imageable area thereon, the imaging member surface including a reflective substrate attached at non-image forming regions thereon along a first side gutter of the imaging member surface outside the imageable area, the imaging member surface having a layer of fountain solution fluid dispensed on portions of both the imageable area and the non-image forming regions at a fountain solution dispense rate;
• a light reflectance detector spatially separate from the imaging member surface forming a gap therebetween, the light reflectance detector configured to measure a light reflectance from the reflective substrate with the fountain solution fluid layer thereon;
• and
• a controller in communication with the light reflectance detector and the fountain solution applicator, the controller configured to determine an interference between light reflectance from the reflective substrate and the measured light reflectance from the reflective substrate with the fountain solution fluid layer thereon, the controller further configured to modify the fountain solution dispense rate based on the interference.