Semi-resonant operation of a fiber-cantilever piezotube scanner for stable optical coherence tomography endoscope imaging

A forward-view optical coherence tomography (OCT) scanning catheter has been developed based on a fiber-cantilever piezotube scanner by using a semi-resonant scan strategy for a better scan performance. A compact endoscope catheter was fabricated by using a tubular piezoelectric actuator with quartered electrodes in combination with a resonant fiber cantilever. A cantilever weight was attached to the fiber cantilever to reduce the resonance frequency down to 63 Hz, well in the desirable range for Fourier-domain OCT. The resonant-cantilever scanner was driven at semi-resonance frequencies that were well out of the resonance peak but within a range of partial resonance. This driving strategy has been found to minimize the phase difference between the two scan axes for a better scan stability against environmental perturbations as well as for a driving simplicity. By driving the two axes at slightly different frequencies, a low-order Lissajous pattern has been obtained for a 2D area scan. 3D OCT images have been successfully acquired in an acquisition time of 1.56 seconds for a tomogram volume of 2.2 × 2.2 × 2.1 mm(3). They were reconstructed without any scan calibration by extracting the scan timing from the image data. In addition, it has been found that the Lissajous scan strategy provides a means to compensate the relative axial motion of a sample for a correct imaged morphology.