A Photosensor-Based Measuring System for Precision Mechanics

In this short paper we describe a general measurement method for quality control of curved surfaces, obtained by means of machine-tools. Such control can be performed by measuring the surfaces in correspondence to a discrete number of adjacent points. Our system is based on a matrix of analog position transducers using commercially available photocouplers, microprocessor controlled by appropriate programs. To avoid the time variability of the displacement voltage transfer function, the characteristics of the photocouplers are stored in a digital memory by measuring a convenient number of reference elements or surfaces (initial calibration). These stored characteristics are then utilized for the evaluation of the unknown surface (measurement). As a result, we obtain with economical components an instrument having a remarkable precision which depends on the photocoupler stability and on the time interval between calibration and measurement.