Fountain solution thickness measurement using an optical grating surface in a digital lithography printing system

An ink-based digital printing system useful for ink printing, comprising:

• a processor;
• and
• a storage device coupled to the processor, wherein the storage device comprises instructions which, when executed by the processor, cause the ink-based digital printing system to measure fountain solution in variable data lithography printing by:
• providing an optical gating-like surface varying in a periodic fashion, wherein diffraction intensity off the gating-like surface varies as a function of fountain solution thickness;
• providing fountain solution onto the optical gating-like surface;
• causing an optical system to emit light through the fountain solution to the gating-like surface, while the light reflected from the gating-like surface is received by the optical system through the fountain solution;
• and
• measuring a thickness of the fountain solution, based on intensity of the reflected light received by the optical system.