Stuttgart-led group combines illumination and microscopy in fiber bundle

How can illumination and microscopy work with a single optical fiber-based endoscope? Using micro-3D-printing, a team of researchers, centered on the University of Stuttgart’s Institute of Applied Optics (ITO) and SCoPE Research Center, has developed compact fiber-tip optics that co-integrate illumination and imaging in a single fiber bundle endoscope.

The achievement is described in a paper in Light Advanced Manufacturing.

Endoscopes usually require separate channels for illumination and bright-field microscopy. For highly miniaturized endoscopes with components in the sub-millimeter regime, the handling and assembly can be prohibitively difficult, causing a practical bottleneck for the further miniaturization of endoscopes for biomedical imaging.

The Stuttgart group’s development of a micro-3D-printed, monolithic optical system also integrates micro-scale imaging and ring-illumination at the tip of an imaging fiber endoscope. Avoiding the usually difficult manual co-packaging of separate illumination- and imaging channels, this new architecture achieves a compact of just half a millimeter.

Furthermore, the imaging optics are hermetically sealed, allowing compact imaging with micro-scale resolution both in air and biomedical liquids. Further advances towards practical applicability in biomedical conditions could produce future endoscopes that facilitate the access to small organs and enable less invasive imaging procedures.

Repeatable fabrication

The paper Light Advanced Manufacturing paper reports: “A manufacturing process, suitable for possible future high-throughput fabrication, must be precise and repeatable. For the approach presented in this work, possibly critical manufacturing steps include the multiphoton 3D-printing of the front- and back-end optical components, and adhesion step of the 3D-printed endo-microscope to the CFB front-end.

“Optical surfaces 3D-printed using multiphoton lithography have shown high inter-process reproducibility for the fabrication of refractive lenses and complex DOEs. Thus, the 3D-printing process promises the reliable manufacturing of crucial endoscopic components presented in this work: the back-end DOE and front-end integrated endo-microscope.

“The reproducibility and precision of passive assembly using 3D-printed alignment structures has been investigated in the context of integrated photonics plug-and-play interconnects. Reproducible performance was demonstrated, achieving precise fiber-to-chip coupling with efficiencies approaching active alignment procedures.

“Our proposed passive alignment connection between 3D-printed optics and the CFB endoscope  differs in layout to the referenced work. However, the same multiphoton 3D-printing process governs the tolerances; therefore, they are expected to be equally precise.”