The fundamental goal of this potentially transformative research project is to investigate the feasibility of ultracompact optical imaging systems for ultraminiature cameras designed for chronic surgical implantation in the human body, as well as for minimally invasive endoscopic examinations. Biomedical imaging applications of such ultraminiature cameras include chronically implantable cameras, ultraminiature endoscopes, an intraocular camera for retinal prostheses, a wide field-of-view eye-tracked extraocular camera for retinal prostheses, and a miniaturized eyetracking camera.
The principal research activities enabled by this grant will include theoretical analysis, fabrication, and test of ultraminiature optical systems that are both compact and low-mass to allow for surgical implantation; the incorporation of optimized imaging capability in such highly miniaturized optical systems by means of ultra-small form factor refractive and hybrid refractive/diffractive optical elements; the investigation of design principles for the development of low power, low form factor CMOS image sensor arrays that are optimized for biomedical imaging applications, and the assessment by means of visual psychophysics techniques of the importance of pre- and post-image filtering of pixellated images for biomedical applications, in order to establish appropriate design constraints for these novel optical imaging systems.
The fundamental goal of this potentially transformative research project is to investigate the feasibility of ultracompact optical imaging systems for ultraminiature cameras that are designed for chronic surgical implantation in the human body, as well as for minimally invasive endoscopic examinations. Such ultraminiature cameras must be at once extremely small, very low mass, and very low power, as well as being both biocompatible and hermetically sealed for chronic implantation. Recent advances in biocompatible optical materials, optical systems design, and CMOS image sensor array technology potentially enable this extreme miniaturization. Biomedical imaging applications of such ultraminiature cameras include chronically implantable cameras, ultraminiature endoscopes, an intraocular camera for retinal prostheses, a wide-field-of-view eye-tracked extraocular camera for retinal prostheses, and a miniaturized eye-tracking camera. In the intraocular camera application, for example, the ultraminiature camera is designed for implantation within the human eye, with capability for partially restoring vision in those blinded by photoreceptor degenerating diseases such as retinitis pigmentosa (RP) and age-related macular degeneration (AMD). The intraocular camera is designed to provide either still images or a video stream to a pixellated microstimulator array that is proximity-coupled to the retinal surface. The development of such an ultraminiature intraocular camera (IOC) would eliminate the need for an external head-mounted or eyeglass-mounted camera in retinal prostheses, thereby providing for a completely implantable prosthetic device capable of restoring sight with foveation to the blind, at the same time relieving surgical complications. These diseases are widespread; the American Foundation for the Blind estimates that approximately 1.3 million Americans are legally blind, of whom many are victims of either retinitis pigmentosa or age-related macular degeneration. The intellectual merit of this research program resides in part in the use of application-dependent constraints to make possible the development of a new generation of ultraminiature imaging systems that in turn enable novel biomedical applications. This research program is highly interdisciplinary, and involves visual psychophysics, optical system design, optical component fabrication, constraint optimization, CMOS circuit design, and optical imaging system integration and packaging. The potential impact of such novel chronically implantable cameras is evident in the potential for post-surgical examination of, for example, key regions of arthroscopically modified joints in full motion, or regions of tissue thought susceptible to cancerous regrowth. The potential impact of the successful development of an ultraminiature intraocular camera for retinal prostheses also cannot easily be underestimated, as the alleviation of blindness is a truly worthy goal. The development of a highly miniaturized intraocular camera will allow for the production of a completely surgically-implantable retinal prosthesis with procedures similar to those employed in cataract surgery, minimizing post-surgical complications and enhancing chronic toleration. Even broader impacts of this research program include applications of ultraminiature optical imaging systems to automotive and aerospace applications, in which low power, low form factor imaging systems can be incorporated during manufacturing, thereby allowing for long term monitoring of inaccessible but critical components. The principal research activities enabled by this grant included the theoretical analysis, fabrication, and evaluation of ultraminiature optical systems that are compact, low-mass, and hermetically sealed to allow for surgical implantation; the incorporation of optimized imaging capability in such highly miniaturized optical systems by means of ultra-small form factor optical elements; the development of ultraminiature wide-field-of-view lenses for an eye-tracked extraocular camera; the investigation of design principles for the development of low power, low form factor CMOS image sensor arrays that are optimized for biomedical imaging applications; the design, fabrication, and evaluation of ultraminiature CMOS sensor elements capable of detecting the presence of positive mobile ions and moisture, thereby providing a means of detecting early signs of a breach in package integrity that could eventually lead to device failure; and the assessment by means of visual psychophysics techniques of the importance of pre- and post-image filtering of pixellated images for biomedical applications, in order to establish appropriate design constraints for these novel optical imaging systems. In addition, we have demonstrated that monocular depth cues (such as lines converging at infinity) persist even in the low resolution limit characteristic of current and projected intraocular retinal prostheses. As a consequence, those implanted with intraocular retinal prostheses may be able to perceive significant depth in the environment, even though the implants will initially be limited to a single eye. During the research program, we have presented multiple seminars within the Center for Excellence in Teaching at the University of Southern California, at the USC Keck School of Medicine, and within the Caltech Project for Effective Teaching (CPET) at the California Institute of Technology on "The Art of Scientific Presentation", in which specific examples were chosen from this research program. In addition, invited seminars on "An Intraocular Camera for Retinal Prostheses: Restoring Sight to the Blind" were presented to classes in Electrical Engineering, Engineering, and Biomedical Engineering at the University of Southern California.
