Study on Optical Servosystem

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1.Mechanism of Photovoltaic Effect.The electric model for the photovoltaic effect in PLZT element is proposed to make clear the mechanism of the photovoltaic effect in it. The model is constructed in parallel by an electric current source dependent on the light intensity, electric resistance on the light intensity and the temperature of the element, and the electric capacitance on the temperature. The validity of this model is shown by the experiment.2.Inprovement of Characteristics of PLZT Element.It can be estimated from the electric model that the PLZT element has the very slow response speed of second ordor. The rise time of the response speed can be considerably improved by the superposition of the pyro-electric effect caused by irradiating the light for heating on the surface of the PLZT element, and the settling time of the response is also improved by controlling the time to irradiate the light for heating. It is clarified by the experiment that the doping of W of 0.5 mol% impr … More oves the response speed, and the optimization of the doping should be investigated for the improvement.3.Development of Control Method in Optical Servosystem.Some control methods of the displacement of the bimorph type optical actuator are developed. In a simple On-Off control some large stationary oscillation is caused in the step response because the optical shutter in the system necessary for control of the irradiating time has severe time lag characteristic. The other two methods are studied to compensate the weak point. The one is the method where the irradiating time is controled by considering the current displacement of the actuator, the current velocity and a threshold relating to them. The other is a predicition control where the irradiating time is predicted by cunsidering the current displacement and the time lag of the optical shutter. It is clarified by the experiment that the prediction control is most applicable among these three methods.It can be said from these results that the optical actuator using PLZT element is applicable to the optical servosystem if they will be investigated further in detail. Less