Centre for Sensors, Instruments and Systems Development

Universitat Politècnica de Catalunya

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Optical sectioning techniques using self...

Preliminary design of the research prototype
On skin SMI modelization
SMI Sensor


Optical sectioning techniques using self-powered interferometry: applications in biophotonics.

Principal investigator

Santiago Royo Royo [+info]


Optical Feedback Interferometry (OFI) is an optical sensing scheme that has become the core working topic of our research. In OFI, the light emitted by a laser diode is partially backrreflected from a target surface, and enters back into the laser cavity, causing beats in the emitted power, which may be interpreted as interference fringes. Such beats are typìcally sensed by the monitor photodiode present in most laser diodes. Thus, it is a very compact, self-aligned, cost-effective and high resolution (nanometers) sensor suitable for many applications. When applied to tissues in health-related applications, however, it lacks depth sectioning capabilities. The signal recovered includes feedback signal returned from all possible depths, limiting severely its potential applications, as the information obtained is integrated. Blood flow sensing, microfluidics or even pulseoximetry are techniques feasible to OFI which would benefit from depth-resolved information, but at present lack it. Optical sectioning, however, has a number of well-established strategies in optical engineering and biophotonics, which have been used to discriminate depth information in tissues. Up to now these techniques have not been applied to OFI sensing, possibly due to the origin of OFI in the electronics engineering world.

The goal of this project is to develop experimental setups which enable optical sectioning capabilities in OFI-based setups, to enable novel, compact, cost effective and non invasive medical devices. With this purpose, two well-established techniques for optical sectioning, confocal microscopy (CM) and photoacoustic tomography (PAT) will be adapted to the coherent sensing scheme of OFI and experimentally tested using lab prototypes. The development process of two different complex operative prototypes, and the limited time of the project, prevents the inclusion in any clinical trial. The prototypes will be tested and validated on tissue phantoms, which have more controlled conditions for validation of prototypes at this stage of development. Such tissue phantoms will be built and characterized at CD6, in order to accurately control its preparation process and optical specifications. The project has thus four partial objectives to attain its main goal. Firstly, detailed optical and photometric modelling of light propagation in tissue, and the effects induced in the laser feedback, will be implemented. Such simulations will be then validated on tissue phantoms built and characterized in our laboratory, to confirm the feasibility of both the models and the phantom construction and characterization procedures. The complexity of the phantoms will increase to adapt to the stage of development of the project. At the end of the project two different operative prototypes with optical sectioning based on OFI (OFI-CM and OFI-PAT) will be built and tested on different types of tissue phantoms. 

In our last two projects within the Plan Nacional we have developed micro and nanometric OFI setups applied to biophotonics (sensing the arterial pulse wave - a licensed patent-) and to laser ultrasonics (optical detection of the ultrasonic wave), an application close to PAT. This has given our team the experience to tackle a relevant sensing problem like the one presented, reinforced also by our long-term collaboration with Thierry Bosch from the LAASCNRS Centre at Toulouse, a world class specialist in OFI research which actively participates in the project.

CD6 Centre for Sensors, Instruments and Systems Development
Rambla de Sant Nebridi, 10  ·  08222  ·  Terrassa (Barcelona)