Abstract
We report a two-axis water-immersible microscanning mirror using torsional and bending biaxially oriented polyethylene terephthalate hinges. Two different designs based on a four- or single-coil electromagnetic actuator are investigated. A micromachining-based fabrication process is developed to enable high patterning resolution and alignment accuracy and to reduce the amount of manual assembly. With a torsional hinge, the fast axis has a resonance frequency of 300 to 500 Hz in air and 200 to 400 Hz in water. With a bending hinge, the slow axis has a resonance frequency of 60 to 70 Hz in air and 20 to 40 Hz in water. 2D B-scan and 3D volumetric ultrasound microscopy are demonstrated using the hybrid-hinge scanning mirror. The ability of scanning the slow axis at DC or very low frequencies allows a dense raster scanning pattern to be formed for improving both the imaging resolution and field of view.
Highlights
Microelectromechanical systems (MEMS) scanning mirrors have been developed to provide fast scanning of light beams in air for a number of optical applications, such as light detection and ranging,[1,2] variable optical attenuator,[3] fluorescence microscopy,[4] and optical endoscopy.[5]
Different from conventional MEMS scanning mirror designs, flexible polymer hinges are used in the water-immersible microscanning mirrors (WIMSMs) to resist the possible shock damage in a liquid environment
With a much lower Young’s modulus, the elastomer hinge reduced the resonance frequency of the slow axis down to
Summary
Microelectromechanical systems (MEMS) scanning mirrors have been developed to provide fast scanning of light beams in air for a number of optical applications, such as light detection and ranging,[1,2] variable optical attenuator,[3] fluorescence microscopy,[4] and optical endoscopy.[5]. In current WIMSMs, the two torsional hinges (one for fast axis and the other one for slow axis) are usually made of the same (polymer) material, such as biaxially oriented polyethylene terephthalate (BoPET) or polydimethylsiloxane.[9] Even with different geometric designs, a large resonance-frequency ratio still cannot be readily obtained. By combining the torsional and bending modes, highly different driving frequencies of the fast and slow axes can be achieved with single (BoPET) hinge material. Using the new scanning mirror, scanning ultrasound microscopy has been conducted
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