Flexure suspension for two axis actuator

Abstract

A device for reading information from or writing information to an optical disc memory system using light from a laser diode includes an upper and lower flexure suspension. Both flexure suspensions are mounted on both an objective lens holder and its base. Each of these flexures is U-shaped and the central part of each leg of the U is a stiff beam. At each end of the control beam is provided a tracking hinge. Outward from the tracking hinges are a pair of focusing hinges which are separated from the tracking hinges by means of spacing beam sections. The unique configuration of the system allows these parallel mounted flexures to move in only two rigid modes namely, displacement along the x-axis (tracking) and displacement along the z-axis (focusing). These two rigid modes allow the objective lens to be re-positioned so that light beams may strike the information medium correctly. The sturdiness of these beam section therefore constrains the four remaining degrees of freedom so that displacement in the y direction, namely tangential motion and rotation in the x, y and z directions, specifically roll, pitch and yaw are severely limited thus essentially eliminated. This feature is paramount in that the possibilities . for undesired skewing of the flexure and the attached objective lens are precluded.