Vladimir Rubtsov

Long-period gratings in optical fibres for chemical sensor applications

Analysis of long-period fibre grating (LPG) parameters and their mutual dependences are presented. LPGs were studied and optimized specifically for chemical sensor applications. It was found that absorption by the fibre cladding of some environmental gases, such as oxygen or water vapour, may result in a false signal generation. The principal limitation of the sensor sensitivity is connected to the longitudinal homogeneity of the fibre refractive indices.

Microhand With Internal Visual System

A pneumatically operated four-fingered micromanipulator (a ldquomicrohandrdquo) with a fiber-based internal visual system is developed using microelectromechanical systems fabrication techniques. This ldquoseeingrdquo microhand transfers images generated by the optical system equipped at the palm of the microhand to an operator via an optical fiber bundle to provide the shape and distal information of objects of interest. The use of illuminating fibers along with the optical bundle enables the microhands operation even in light-deficient environments. Such visual information informs the accurate relative location of the device and the status of manipulation to the operator in real time, who will take subsequent actions accordingly with an increased accuracy and efficiency. Embedding the fiber-based optical system inside the manipulator, instead of using an external camera setup for overall system monitoring, greatly reduces the size of the manipulator and helps increase maneuverability, particularly when operating in a space-limited work area. Tests have been conducted to verify the performance of the visually aided microhand to manipulate millimeter-sized objects in real time. Building on the ability of the UCLA microhand to gently handle irregular-shaped objects, this vision-enabled microhand is expected to provide more accurate manipulations and widen the window of applications.

Miniature Flipping Disk Device for Size Measurement of Objects Through Endoscope

Finding the size and distance of objects viewed through a single optical path-a typical endoscopic condition-is a challenge. Stereo imaging, which would provide the size and distance information, typically requires multiple optical channels or other elaborate techniques, increasing the endoscope diameter and system complexity. This paper reports the development of a miniature flipping disk device that enables stereo measurement, and demonstrates the operation of the device installed in an endoscope. The fabricated Pyrex disk (1.2 mm in diameter and 485 μm in thickness), anodically bonded to a 50-μm-thick silicon vertical comb-drive actuator, is flipped to ±10.7° at a resonant frequency of 414 Hz by 10 VAC of electrostatic actuation. The image shift made by such glass flipping provides a reference dimension, against which the real size and distance of objects seen through a standard single-channel endoscope can be estimated.

A micro translating lens unit for stereo imaging through single-image endoscope

Most stereo imaging tools require the use of multiple optical channels to achieve slightly different viewing angles around an object of interest, which inevitably increases overall size and structural complexity compared to single imaging systems. In this study, a translating lens device is developed to generate stereo images especially for endoscopic applications through a single-objective lens setup. A silicon comb-drive translates a miniature lens across the optical axis in front of an optical circuit to create different viewing angles through a single optical channel. Up to ±50 μm of lens translation has been tested at 24 VDC providing stereo acquisition for 3D perception. Coupling 3D viewing capability and the size advantage of a single endoscopic optical system, this technology aims to enhance the operators visual perception without sacrificing the endoscopes size.

Pneumatically deployed net system for endoscopic removal of foreign object

Endoscopic tools are widely used for removal of a foreign object from hard-to-reach areas in various applications including medical ones. However, metallic grabbers typically used for such endoscopic removal always bear the risk of accidently damaging surrounding surfaces or losing the grabbed object. Use of flexible grabbing systems such as a net would greatly reduce such risks by gently handling the object and yielding upon contact with the surroundings. In this study, a new object removing plan using a flexible grabbing system with object-locking is presented along with its realization through a pneumatically operated net and designated hook.

Fiber photo-catheters with spatially modulated diffusers for laser treatment of atrial fibrillation

A new generation of the optical fiber catheter has been developed for surgical treatment of atrial fibrillation with laser radiation. Atrial fibrillation (AF) is a heart rhythm abnormality that involves irregular and rapid heartbeats. The surgical maze procedure was the first treatment that offered a permanent solution for maintaining a normal sinus rhythm in patients with AF. This procedure involves the creation of a maze-like series of incisions in the left atrium, resulting in isolation of the pulmonary vein and removal of the left atrial appendage. To produce long continuous transmural lesions laser diodes operating in near IR range along with end-emitting fiber catheters have been used experimentally. The absence of side-emitting flexible catheters with the ability to produce long continuous lesions limits the further development of this technology. In this research, a new type of an optical catheter consisting of a flexible, spatially modulated fiber diffuser has been used to make continuous photocoagulation lesions for effective maze procedure treatments.

Miniature Netting System for Endoscopic Object Retrieval From Hard-to-Reach Area

Retrieval of an object from hard-to-reach areas requires the use of instruments of various kinds sent through an endoscope. However, removing a flat object firmly lodged in a narrow space, such as a coin or a button battery in a digestive passageway, causes complications when using existing endoscopic instruments. To address such a difficult situation, this paper reports development of a miniature retrieval device using MEMS technology and implementation of the device in a custom-made endoscope. The MEMS device consists of a circular plastic net 15 mm in diameter and pneumatically operated microjoints integrated under the net to bend it. The endoscope is equipped with a hooking mechanism, which secures the net after it wraps the object, and double imaging systems through which the operator monitors overall endoscopic retrieval procedures. Object retrieval is tested in a lab environment using a coin in a tube.

Miniature Stereo Imaging Converter With Translating Aperture

Depth information from an image can greatly increase the work efficiency when observing or inspecting objects, because the size, distance, and relative locations can be estimated. Various stereo imaging methods are being used to find depth information in a wide range of application fields, typically by placing multiple optical systems side-by-side to create multiple shifted images. In this study, we develop a miniature stereo image generating device, which can augment an existing single optical system (i.e., a two-dimensional images capturer) with three-dimensional capability. Developed with MEMS technology, the device consists of a single translating aperture, which shifts laterally between two positions (up to 100 μm apart demonstrated) by means of electrostatic comb actuators. Attached at the objective end of conventional (i.e., nonstereo) optical systems, this stereo converter with an aperture 900 μm in diameter is shown to successfully generate slightly different viewing angles, providing stereo images. Being miniaturized, this device is suitable for microscopic or endoscopic applications, where the size of the system is limited or axial depth of focus is relatively large.Copyright

Fiber photo-catheters for invasive and less invasive treatment of atrial fibrillation

Atrial fibrillation (AF) is a heart rhythm abnormality that involves irregular, and often rapid, heartbeats. Recent studies demonstrate the feasibility of treating AF and other structural heart diseases with limited, left-atrial ablation lesion sets. These cardiac ablation procedures reduce the time required to perform the maze procedure surgery, and are less invasive. To produce long continuous transmural lesions, solid-state lasers and high power laser diodes, along with end emitting fiber optic catheters, have been used experimentally. These devices demonstrated promising results, but the absence of side emitting fiber flexible catheters to produce long continuous lesions limits the further development of this technology. In this research, a prototype energy delivery and control system located in a catheter, was demonstrated. The highlight of the proposed system is a flexible 10-cm fiber diffuser that can be used to make continuous photocoagulation lesions for effective maze procedure treatments. The system also includes: a flexible optical reflector; a distributed temperature sensor array for monitoring the temperature in the surrounding tissue; a series of openings for rapid self-attachment to the tissue (vacuum holder - gripper); and an optional closed-loop irrigating chamber with circulating coolant to cool the optical diffuser.