inspired design of the lens architecture, a bio-inspired working principle of the lens tunability and the tunability of the curvature of the photodetecting unit.

1

This thesis is the first step towards the development of an enhanced optical system inspired to the pre-retinal structure eyes. This device will have to

integrate two tunable polymer lenses obtained by combining an emerging class of polymer-based ‘artificial muscle’ materials and technology, with a bio-

inspired design of the lens architecture, a bio-inspired working principle of the lens tunability and the tunability of the curvature of the photodetecting unit.

The lenses working principle imitates the accommodation of the crystalline lens of human eye and the one of the cornea of bird of prey [1-3]. Combining the optical effect of each tunable lens in the bio-inspire system we will obtain an

‘artificial-eye’ equipped with a double tunability of the focal length and consequently, a double variability of its other optical properties (e.g.

aberrations). Moreover, the bio-inspired optical system should show a

comparable size of the human eye and enhanced optical performance in terms of visual acuity.

The development of this device is an articulated and complex process, and in this context the thesis aim is to provide a software tool to model the bio-

inspired optical system and to evaluate its optical properties during the variation

of the lenses shape. Thus, to test the software performance we designed the

system with features similar to the human eye in terms of visual resolution,

lenses dimension and optical power distribution between the lenses. Moreover,

to implement the model, it has been necessary to carry out an experiment to

measure the refractive index (with an accuracy of

) of the fluid (pre-

polymer SILGARD 184® )used as refractive medium into the lenses . The

refractive index has been measured as function of wavelength ( )

and of temperature ( )

2 The thesis is structured as follows:.

 Chapter 2 describes the structure and the optical features of two

“biological cameras” : the human eye and the eye of birds of prey. It focuses on the different process of accommodation between the two eyes which are source of inspiration for the polymeric lenses.

 Chapter 3 describes the state of the art of tunable lenses and the

structure, the working principle and the feature of the polymeric lenses with electroactive elastomers which we use in the bio-inspired optical system.

 Chapter 4 presents the set-up, the experimental protocols, the algorithms for the data analysis and the results of the experiment carried out to measure the refractive index of pre-polymer SYLGARD 184®.

 Chapter 5 presents the models of the polymer lenses and of the bio- inspired optical system which is designed to have performance similar to the human eye.

 Chapter 6 presents the optical characterization of the designed model, also during the accommodation of the polymer lenses , in terms of paraxial optics and primary aberrations.

 Chapter 7 summarizes the achieved work and suggests possible future works.

Finally are proposed the following appendices:

 Appendix A, divided into four( I,II,III,IV) sections, is a overview of the background for optical design in terms of geometrical optic, aberrations, basic elements for optic design and ray-tracing.

 Appendix B presents the algorithms (coded with MATLAB®) used to data analysis in the measurement of the refractive index of pre-polymer SYLGARD 184®.

 Appendix C presents the software tool (coded with MATLAB®)

developed for the bio-inspired optical system.

3 References

[1]: “Bioinspired tunable lens with muscle-like electroactive elastomers” Carpi F., Frediani G., Turco S., and De Rossi D. ADV. FUNCT. MATER. 2011, 21, 4152-4158.

[2]: “Sviluppo e caratterizzazione di una lente polimerica elettroattiva per cristallino artificiale”. Tesi di laurea di Turco Simona.

[3]: “Sviluppo e caratterizzazione di una lente corneale a fuoco variabile bio-ispirata” . Tesi di laurea di Panti Sara

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