Optical scanner using a MEMS actuator

Optical scanners have numerous applications from bar code readers and laser printers in industry to corneal resurfacing and optical coherence tomography in medicine. We have developed an optical scanner fabricated using photolithography on a polyimide substrate. This scanner uses an electrostatic microelectromechanical system (MEMS) actuator to tilt a gold-coated mirror resting on 3 mum thick polyimide torsion hinges to steer an optical beam. The linear actuator used is the integrated force array (IFA), a network of hundreds of thousands of deformable capacitors, which electrostatically contract with an applied differential voltage. IFAs are 2.2 mum thick patterned, metallized polyimide films 1 cm long and either I or 3 mm wide depending on the application. The mirror support structures were modeled using one-dimensional beam theory and ANSYS finite element analysis and then fabricated using a three-layer process with polyimide and gold on silicon wafers. Side scanning structures have been fabricated with tables 1.125 or 2.25 mm wide. The completed devices were coated with a 500 Angstrom thick conformal coating of parylene for protection from the environment. These devices have demonstrated optical scan angles up to 146degrees for applied voltages up to +/-50 V. These devices were also used to steer a laser beam in a prototype bar code reader to demonstrate functionality. (C) 2002 Published by Elsevier Science B.V.