Optical-resolution photoacoustic microscopy (OR-PAM) can image biological tissues at micrometer level resolution. However, the imaging speed of traditional OR-PAM is often too slow for capturing dynamic information. In this work, we demonstrate a high-speed OR-PAM system using a water-immersible two-axis torsion-bending scanner, in which the fast axis employs the torsion scanning while the slow axis works at the bending mode. The system has achieved a cross-sectional frame rate of 400 Hz, and a volumetric imaging speed of 1 Hz over a field of view of 1.5 × 2.5 mm2. We have demonstrated high-speed OR-PAM of fast hemodynamic changes in vivo.
This paper reports a new two-axis water-immersible micro scanning mirror (WIMSM) using torsional and bending BoPET (biaxially-oriented polyethylene terephthalate) hinges. 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 Hz in air and ~200 Hz in water. With a bending hinge, the slow axis has a resonance frequency of 60~70 Hz in air and 20~40 Hz in water. 2D B-scan and 3D volumetric ultrasound microscopy are demonstrated by 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.
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.
In this paper, we report a new two-axis micro scanning mirror (WIMSM) using torsional and bending BoPET (biaxially-oriented polyethylene terephthalate) hinges. With a torsional hinge, the fast axis has a resonance frequency of 265 Hz in air and 172 Hz in water. With a torsional hinge, the fast axis has a resonance frequency of 265 Hz in air and 172 Hz in water. With a bending hinge, the slow axis has a resonance frequency less than 1 Hz. When the two axes are driven at their resonance frequencies, a dense raster scanning pattern with a maximal scanning range is obtained. For demonstration, 3D volumetric ultrasound microscopy in water is conducted with the new WIMSM.
In this paper, we report a new electromagnetically-driven two-axis water-immersible scanning mirror with single inductor coil actuator. By making the resonance frequencies significantly different, the scanning motion of the two axes can be decoupled due to the dynamic structural filtering effect. For verification, a prototype micro scanning mirror was designed, fabricated and tested. The resonance frequencies of the fast and slow axes in air and water were determined to be 720/72 Hz and 690/55 Hz, respectively. The optical tilting angle of both fast and slow axes at the resonance frequencies was characterized, which shows good linearity with the amplitude of the driving current. With both axes driven simultaneously at frequencies close to their resonance, stable and repeatable 2D raster scanning was successfully achieved in both air and water, respectively. 2D B-mode ultrasound microscopy was also demonstrated by using this micro scanning mirror.
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