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Endoscope with optical sectioning capability

In recent years, the use of endoscopic instruments for examining and operating on internal regions of human body has become commonplace. Apart from improving the resolution and reducing the diameter of the probe current research is aimed at providing a 3-D imaging capability for these devices. Diverse approaches have been demonstrated ranging from binocular-view endoscope I to holographic imaging2. Because of its optical sectioning property the confocal scanning microscope is a tool especially suited for imaging of volume objects3. This property means that only thin region adjacent to the focal plane of the microscope is imaged while volume scattering is rejected by confocal filtering (in conventional imaging systems scattering causes blurring of the focused image). The object's appearance is then reconstructed by combining the recorded optical slices. Fibre-optic modification of the confocal microscope4 is most promising candidate for endoscopy applications due to it's compactness and flexibility. The fibre scanner is however the main obstacle to the system integration under given geometrical constraints (typically less than 2 mm outer diameter). We suggest here replacing the bulk focusing lens by gradient-index (GRIN) rod that is long enough to move the scanner off the zone of strict dimensional constraints. We demonstrate in this work a practical compromise between the dimensions of the probe and the endoscope 3-D imaging capacity.