Biophotonics_Concepts_to_Applications

For this application, 80-μm cladding-diameter SMFs and reduced-cladding MMFs
are available from various suppliers.

10.2.3 Tethered Capsule Endomicroscopy

A recent development in endoscopy for the digestive tract involves using a swal-
lowable capsule that is connected with an opticalfiber link to a measurement
instrument outside the body. This setup enables the use of high-resolution confocal
microscopic techniques inside the body to diagnose and monitor diseases in the
digestive tract. The method is known astethered capsule endomicroscopy. The
clinical procedure involves swallowing a nominally 7-mm-diameter and 30-mm
long rotating viewing capsule that is tethered to an opticalfiber link and captures
cross-sectional microscopic images as it travels through the digestive tract [ 26 – 28 ].
Images that are obtained have a nominal 30-μm lateral resolution and a 7-μm axial
resolution. As illustrated in Fig.10.11, typically the tethered capsule endoscope
system consists of (a) an external control module that contains a light source, a
photodetector, capsule manipulation controls, and signal-processing elements, (b) a
tether consisting of aflexible drive shaft for rotating the capsule, (c) a high-NA
SMF contained within the drive shaft, and (d) the rotating capsule that contains the
viewing optics.

10.3 Laser Speckle Imaging

Whenever coherent laser light illuminates a diffuse or random scattering medium,
the light that is scattered from different places on the illuminated surface will travel
through a distribution of distances. This distance distribution will give rise to
granular constructive and destructive interference patterns in the scattered light
distribution [ 29 – 34 ]. If a camera or photodetector array is used to observe the
scattered light, a randomly varying intensity pattern known asspecklewill be seen.
As shown in Fig.10.12, the granular speckle patterns look like sheets of moving

Optics

Optical fiber encapsulated

in a rotating drive shaft

Control

module

Viewing

windows

7 mm

Rotating

endoscope capsule

30 mm

Fig. 10.11Example schematic of a tethered capsule endoscope system

10.2 Endoscopy 307