PURPOSE:To perform easily such a control that a prescribed displacement may be obtained to the prescribed input by forming at least one cut part at least to either one of two plate-shaped elastic members. CONSTITUTION:The working characteristics of an information reader depend on the characteristics of an elastic member. The tracking operation due to the rectangular displacement of an objective lens 16 to an optical axis is carried out by the functions of plate springs 19 and 20. In this case, the control is given to ensure an accurate operation to the tracking signal. As shown in the figure, three rhombic openings 24-26 are drilled almost equidistantly in the lengthwise direction of the spring 19. In this example, the elastic characteristics of the spring 19 are reduced evenly in its lengthwise direction. Then the displacement characteristics can be accurately obtained to the tracking signal with said characteristics of the spring 19 together with the characteristics of the spring 20. For this purpose, the overall elastic characteristics are controlled for the spring 19.
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