Samenvatting
In this thesis, we investigate the integration of tunable lenses in micro-optical smart camera systems. We designed a 2-channel smart imaging system that possesses refocusing capabilities, via the implementation of a voltage-tunable liquid lens.We first studied the operation of different types of tunable lenses. This allowed us to compare their characteristics and performance. From this discussion, we concluded that the voltage-tunable liquid lenses show the best performance and integration possiblities. In this thesis, we have terefore chosen to investigate the Varioptic voltage-tunable lenses.
Via the use of the Mach-Zehnder interferometer, we determined the optical characteristics of the Varioptic Arctic lenses both for on- and off-axis illumination. We measured the tunability of the focal length, by changing the applied voltage. We also determined the root mean square of the wavefront aberrations, to be able to study the performance of the lenses. This gave us an idea of their operation and design possibilities. For the integration in the refocusing systems, we preferred a lens with a large focal range and a diffraction-limited performance. These requirements were mainly fulfilled by the Arctic 320 lens.
Afterwards, we used the data of the measurements to make a model for this lens in ray-tracing software. The latter was combined with one or more passive lenses, to design a voltage-tunable refocusing system. We made simulations of different types of configurations, with two and three lens elements. The obtained systems show a good performance. We achieved a large depth of field and an angular resolution which is better than 0.01°, except for the simulations where we placed the tunable lens as the first element in the configuration. for these ones, the angular resolution was much larger.
For both the voltage-tunable and mechanical refocusing systems, we were able to obtain some configurations that show through simulation a diffraction-limited behavior over a large depth of field. The simulation of a voltage-tunable system was also checked by a proof-of-concept. This setup showed the same performance and depth of field as the simulations, which confirmed its correctness. The voltage-tunable refocusing systems can have a lot of advantages. They can be easier integrated and be made more compact than the mechanical ones.
At the end, the one channel imaging system is extended to a 2-channel one. This fits in the current ongoing research at BPHOT, that investigates multi-channel designs. Up to now, these channels are static and so posses no refocusing capabilities. This disadvantage can be eliminated by the use of a tunable lens. In this thesis, we investigate the integration of the tunable lens in a multi-channel system, in order to add refocusing capabilities to the design.
We present a 2-channel imaging system. The first channel contains a static configuration, with a wide fiels of view. The second one contains a voltage-tunable refocusing system with a high angular resolution. This imaging system allows to get a wilde view, inaccurate image via the first channel and a small-view, high-resolution image via the second one. Through the implementation of the tunable lens, we obtained a design with a much larger depth of field, than is possible with the use of a static configuration.
This concept can have a lot of application, like for example in medical imaging and security.
| Datum prijs | 2012 |
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| Originele taal | English |
| Begeleider | Heidi Ottevaere (Promotor), Youri Meuret (Co-promotor) & Gebirie Yizengaw Belay (Jury) |