Amplified bimorph scanning mirror for optical coherence tomography

We have modeled, fabricated, and tested an amplified bimorph scanning mirror for application in optical coherence tomography. The scanning mirror was fabricated using photolithography on a polyimide substrate. This scanning mirror uses a bimorph actuator to drive a polyimide micromechanical structure at resonance. The forced vibration of the micromechanical structure causes a polysilicon gold plated mirror attached to two torsion hinges to tilt. Operating the device at resonance allows us to achieve very large displacements of the mirror. The material properties of the polyimide allow for large torsion angles in the hinges to be realized. The mirror and support structures were modeled using one-dimensional beam theory and fundamental vibration mechanics. The structures were also modeled and simulated using Intellisuite, a microelectromechanical (MEMS) analysis package. This device has demonstrated optical scan angles of up to 80 degrees using applied voltages of 35 V at resonant frequencies of 35 Hz, appropriate for real time imaging.