US Patent 8201913 Drop detector

In one embodiment, a drop ejector assembly includes a printhead, a drop zone immediately downstream from the printhead, an array of optical fibers exposed to the drop zone such that light scattered off drops in the drop zone illuminates at least some of the optical fibers in the array, and a photo detector operatively connected to the array of optical fibers for converting light from the optical fibers into an electrical signal. In another embodiment, a drop detector includes a light source for illuminating drops passing through a drop zone and a light sensor for sensing light scattered off drops in the drop zone. The length of drop zone is 3 mm or less and the light sensor has a cross sectional dimension less than the length of the drop zone.