06/28/2011

Fraunhofer-Institut für Photonische Mikrosysteme IPMS

MEMS based endo-microscope

The Fraunhofer IPMS presents a miniaturized MEMS based laser microscope for being used in narrow environments, e.g. for endoscopic investigations in medicine, biology and industry. It consists of an optical head of only 8 mm diameter, containing a small silicon MEMS mirror of 1.9 by 1.9 mm² chip size and optical components that direct the light onto the object surface as well as receive reflected light for detection and image reconstruction.

The MEMS mirror oscillates resonantly in two axes in order to scan the object surface. The laser beam is focused by an objective in front of the MEMS scanner for achieving a microscopic resolution of about 15 μm within an object field of approximately 3 mm feed size. This enables a variety of new opportunities for viewing small items and structures under difficult access conditions, as in-vivo medical diagnosis of cancer or other suspicious tissues through an endoscope, or microscopic material analysis inside cavities of technical devices. The technical principle of scanning beam imaging is confocal by its nature and potentially allows optimization for various viewing fields, increased resolution, and it is extendable to capture tomography-like multi-layer images.

The optical head is designed and micro-assembled from several necessary components and materials, i.e. the MEMS mirror, optical parts to guide the light and focus it on the object surface, the electrical connections for MEMS driving, and an outer tube to accurately fix that all. It is coupled by a compound cable joining optical fibers and wires to a distant control unit, which comprises the laser light source,optoelectronic detectors, and all embedded electronics that is needed for control and signal processing.

The distant control configuration offers enough space and full flexibility for choosing and combining light sources and wavelength(s), different detectors, optical filters, electronics, etc. The current demonstration setup uses a green laser with 532 nm wavelength, an appropriate detector and an embedded electronic subsystem which controls the all components of the endo-microscope and provides image reconstruction. The embedded electronics connects to a PC or notebook that controls the entire system, visualizes and stores the images.

These works have been funded by means of the Fraunhofer Society.