| One of the autonomous control functions of the eye is to regulate light input to suit the conditions for best visual acuity. This is done by changing the size of the pupil. Losing an eye is devastating at any age. It has great impact on one's self image, self confidence and self esteem causing physical as well as psychological distress. A person who has lost an eye will replace the latter with an ocular implant. Standard ocular implants will attempt to faithfully reproduce the physical features of a natural eye, however the prosthetic pupil is fixed all the time giving a poor cosmetic appearance.;An analog-to-digital converter (ADC) has been integrated to the system, making it more compact. By developing a voltage-to-current converter we were able to use a current input ADC developed by a team of the Polystim neurotechnologies laboratory.;In this master's thesis we propose an artificial human pupil, which is composed of a dedicated controller and a miniaturized display. The purpose of this system is to overcome the problem of post-prosthesis anisocoria for people with ocular implants, by creating iris diaphragm in the prosthetic eye with photosensitive receptors responding to light so as to work in symmetry with the normal eye. The proposed artificial pupil would acquire ambient light through a photosensor, convert the acquired signal to digital data, transform this data to light intensity and finally control the display accordingly. This system would replace the static iris of a prosthetic eye. Experimental results from developed prototype, and post-layout simulation results from the integrated controller faithfully reproduce the expected performance, which is in the form of a dilating and contracting pupil. The main part of the system is implemented in 0.18 mum CMOS process and has a total area of 1.3 mm2. |
