Key Design Considerations for Measurement of Drops-In-Flight using Machine Vision

Abstract

Inkjet technology is in the process of revolutionizing traditional printing and dispensing industries. An ever-increasing number of startups and established companies have been working hard to create their own proprietary inkjet knowledge and advanced materials. Machine vision tools have become integral to this R&D process, especially for imaging and measuring drops in flight.Drop in flight imaging is usually accomplished using a strobe light synchronized with the firing frequency, together with a camera and workstation (Figure 1). Analysis is accomplished using machine vision techniques, including automatic thresholding, edge finding, and connectivity. <fig position="float" id="s46_f.1"> <label>Figure 1</label> <caption>Basic Drop Analysis System Layout</caption> <graphic mime-subtype="tif" xlink:href="Images\s46_f01.tif" xmlns:xlink="http://www.w3.org/1999/xlink"/> </fig>The implementation of this type of system, however, is far from trivial. In order for measurements to be accurate and repeatable, it's very important that proper system design and analysis methods are used.In this paper, we will discuss imaging techniques and other important considerations for drop-in-flight volume and velocity measurements. Broadly speaking, categories include print controller requirements, optical design, image analysis algorithms, and calibration, as well as other factors and pitfalls. The impact of these design choices will be explained using theory, experimental data and practical examples.