In the device developed in the Hungarian Institute MIKI Instrumentation the scanning beam is focused

Laser scanning devices for optical gaugingGyorgy Akos, Rita Csomor, Istvan Hejjas, Pal MarthonMIKI Instrumentation1368 Budapest, P.O.B. 183., HungaryAbstractLaser scanning devices have been constructed for measuring the outer diameter ofcylindrical objects. The size measurement is based on comparing the object to a photo -lithographically fabricated grating. Both one- and two -dimensional measuring techniquesare discussed.IntroductionLaser systems using scanning mirrors have been used for the measurement of diametersof rods, wires, etc.1 This method has the advantage of beeing relatively fast, accurateand contactless. In the device developed in the Hungarian Institute MIKI Instrumentationthe scanning beam is focused onto the sample. A reference beam, moving synchronously withthe sample beam, is scanning over a grating, determining the position of the laser spot.Thus the accuracy of the system is limited by the photolithographically fabricated gratingand not by the linearity of the scanning mirror - focusing lens assembly. The resolutionof the system can be made appreciably larger then the spot diameter by using a relativelylarge grating constant and a suitable interpolation method.Optical setupThe optical arrangement of the device can be seen on Figure 1. The output of a 5-mWHe -Ne laser is intensity stabilized by an acousto- optical modulator and correspondingfeed -back circuit. This device, as well as the galvanometric scanning mirror have beendeveloped at the Technical University of Budapest.