Vision-aided system for obtaining a required weight by efficient choice of irregular fragments

Abstract

There are some situations when it is necessary to weigh, with high accuracy and high precision, a required amount of material using heterogeneous
and irregular pieces. As an example, in the laboratory, when preparing a liquid phase epitaxial growth, each of the materials that constitute the liquid
phase must have an exact weight, within micrograms, given by the phase diagrams. The sources of the materials usually are small polycrystalline
pieces of irregular shapes and random weights. Normally the weighing is done by interchanging the small irregular pieces of different sizes
according to the criteria of the operator until the given weight is obtained. This is a long and tedious process and since each liquid solution requires
several components, and a different liquid phase is needed for each layer, very often weighing it takes several hours. This operative process is
prone to errors. To ease this kind of processes, a vision-assisted system has been developed. It consists of a webcam, an analytical balance and a
PC. To use this assembly the operator only needs to put sequentially the pieces of the material in the analytical balance. When the required weight
can be obtained by a combination of some of the pieces added to the analytic balance, the PC notifies the operator and signals the selected pieces
in the screen. With the help of this system, the weighing accuracy has been improved and the time required to accomplish the process has been
dramatically reduced.