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Technical Briefs

Method to Achieve High Frame Rates in a Scanning Fiber Endoscope

[+] Author and Article Information
Matthew J. Kundrat

Human Photonics Laboratory, Department of Mechanical Engineering,  University of Washington, Seattle, WA 98195kund2463@uw.edu

Per G. Reinhall

Department of Mechanical Engineering,  University of Washington, Seattle, WA 98195

Eric J. Seibel

Human Photonics Laboratory, Department of Mechanical Engineering,  University of Washington, Seattle, WA 98195

J. Med. Devices 5(3), 034501 (Aug 15, 2011) (5 pages) doi:10.1115/1.4004646 History: Received May 27, 2009; Revised June 19, 2011; Published August 15, 2011; Online August 15, 2011

A new and miniature imaging device is being developed to allow flexible endoscopy in regions of the body that are difficult to reach. The scanning fiber endoscope employs a single scanning optical fiber to illuminate a target area, while backscattered light is detected one pixel at a time to build a complete image. During each imaging cycle the fiber is driven outward in a spiral pattern from its resting state at the image center to the outer fringe of the image. At this point, the fiber is quickly driven back to its initial position before acquiring a subsequent frame. This work shortens the time between successive images to achieve higher overall frame rates by applying a carefully timed input, which counteracts the tip motion of the scanning fiber, quickly forcing the scanning fiber to the image center. This input is called motion braking and is a square wave function dependent upon the damped natural frequency of the scanning fiber and the instantaneous tip displacement and velocity. Imaging efficiency of the scanning fiber endoscope was increased from 75–89% with this implementation.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

The distal end of the scanning fiber endoscope laying next to a dime for size comparison

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Figure 2

Full color images from the scanning fiber endoscope during human subject testing: (a) human stomach lining and (b) human vocal cords

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Figure 3

A cutaway view of the distal end of the scanning fiber endoscope and the major components are: (a) the detection optical fibers, (b) the piezoelectric tube actuator and electrodes, (c) the epoxy joint, (d) the scanning optical fiber, (e) the stainless steel housing, and (f) the scan lens assembly

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Figure 4

An illustration of the scan method of the scanning fiber endoscope where the piezoelectric tube is driven with two amplitude modulated sinusoids, X1 and X2 . The result is a space-filling spiral scan. Back-scattered light measured by the detector at each pixel location is assembled to form an image displayed on a screen.

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Figure 5

A representation of the tip motion during the imaging and nonimaging times for a single cycle of the scanning fiber endoscope

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Figure 6

A numerical example of motion braking with five uniform cycles, where T is the period for both the braking input and the scanning fiber tip displacement

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Figure 7

Experimental data showing the time history of the scanning fiber system during outward scanning and braking for the X1 -axis

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Figure 8

Experimental data showing the time history of the scanning fiber system during outward scanning and free decay for the X1 -axis

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Figure 9

Experimental data showing the time history of the scanning fiber system during outward scanning and braking for the rescaled time axis

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Figure 10

Experimental data showing the time history of the scanning fiber system during outward scanning and braking with misidentified braking parameters for the X1 -axis

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Figure 11

Experimental data showing the time history of the scanning fiber system during outward scanning and braking with misidentified braking parameters for the rescaled time axis

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