Optical Head as a Gauge Device in Manufacturing

Abstract

Numerous companies produce shape contouring devices based on the projection of an optical signal to obtain shape information. The basic principle for all of these devices is parallax determination. Parallax can be measured through projecting a small spot, a line, or a light pattern such as a grid. One application of this methodology is a gauge device in manufacturing processes where layers of materials are being deposited or removed to control the final geometry of the surface. The degree of accuracy achieved depends on the final required accuracy of the finished product. An essential aspect is measurement in real-time; real time stands for the time required by the controlling software to detect errors on the finished surface. The speed of the particular fabrication process dictates how quickly the software must be able to process information. The optical head must not reduce the speed of fabrication, and it should provide a warning of a faulty process fast enough to permit real-time corrections. In view of the real time requirement, the luminous signal processing must be reduced to a minimum. An optical head that projects a line is an excellent candidate for this operation because a line is the simplest form of the system that provides all of the required measurements in the case of the material deposition manufacturing process. This paper shows that very high precision and accuracy are achievable in conjunction with extremely low processing times in a unique laser line projection setup. The unique aspect of this system is the ability to make these measurements regardless of surface conditions.