Mark B. Spitzer

Eyeglass-based systems for wearable computing

This paper reports on progress in the area of hardware for wearable computing. Our specific interest is in reducing conventional head-mounted display systems to eyeglass scale. We report here the successful demonstration of an ergonomic eyeglasses-based display. We present some of the general considerations in the design of such eyeglasses and briefly review our approach and initial findings.

Monolithic integration of a light‐emitting diode array and a silicon circuit using transfer processes

This letter reports the attainment of a monolithically integrated light‐emitting diode array on a silicon integrated circuit. The emitters are first formed epitaxially on a lattice‐matched substrate and are subsequently transferred to the silicon. Interconnections are made using thin‐film techniques between the 128 separately addressable light‐emitting diodes and the driver circuit. This work demonstrates attainment of a high level of optoelectronic/logic integration.

Monolithic series-connected gallium arsenide converter development

The development of monolithic GaAs photovoltaic devices intended to convert light generated by a laser or other bright source to electricity is reported. The converters described can provide higher operating voltage than is possible using a single-junction converter, owing to the use of a monolithic circuit that forms a planar series-connected string of single-junction sub-cells. This planar monolithic circuit is arranged to deliver the desired voltage and current during operation at the maximum power point. A description is presented of two, six, and twelve-junction converters intended for illumination by a laser diode with a wavelength of 0.8 mu m. Design and characterization data are presented for optical power in the range of 100 mW to 1 W. The best conversion efficiency exceeds 50%.<<ETX>>

Multijunction cells for space applications

Abstract Recent efforts to improve space solar cell efficiency have involved development of various types of multijunction tandem solar cells. This paper reviews the limits to the efficiency of present-day designs and the most recent results from many active investigations involving silicon, germanium, CuInSe2 and III–V materials.

Gallium arsenide concentrator solar cells with highly stable metallization

The development of GaAs/AlGaAs double-heterostructure concentrator solar cells for space operation that are capable of surviving 5 min thermal excursions to temperatures well beyond 500 degrees C without significant degradation is presented. The cells are formed epitaxially using the organometallic chemical vapor deposition growth process. The design utilizes a contact system that yields high stability at elevated temperature, and AM0 efficiency of up to 20% has been obtained with this approach. The efficiency is observed to change by less than 10% after a 5 min excursion to temperatures as high as 700 degrees C. Stability at higher temperatures and for longer times is discussed, and a comparison is made to the stability of conventional concentrator cells characterized by AM0 efficiencies of up to 23%.<<ETX>>

A review of indium phosphide space solar cell fabrication technology

A review of the status of InP cell efficiency and of approaches to the reduction of cell cost is presented. The use of heteroepitaxial techniques such as InP-on-GaAs and InP-on-Si is discussed along with the use of chemical and mechanical techniques for removal and recovery of the substrate. The efficiency ultimately obtainable with designs made possible by such an approach is calculated.<<ETX>>

Video I/O interface for wearable computers

This paper is a report of work in progress toward the development and testing of a computer interface mounted in eyewear, and capable of both input and output functions. The unique feature of this interface is the use of advanced embedded optical techniques to form eyeglass lenses capable of relaying images internally, without significant optical components in front of the users face. These optical techniques make possible the incorporation of both a camera and display within eyeglasses. The interface also includes audio input and output. The paper discusses methods of constructing such an interface, design considerations, and will describe work in progress to realize working models.

Toward eyeglasses-based electronic displays

The development of a head mounted display concealed within eyeglasses has been a long term objective of many head mounted display (HMD) development efforts. This paper will review design concepts from the literature, with a view toward assessing the practical merits of the various approaches. The factors of importance in miniaturizing a HMD will be summarized. Finally, we will briefly summarize some new approaches including the use of alternative display technology that may lead to a display system hidden within eyeglasses frames.

Applications of circuit transfer technology to displays and optoelectronic devices

This paper reviews the use of circuit transfer processes for optoelectronic applications. In this process, a circuit comprising either Si or GaAs devices is removed from its original substrate and is transferred to a second substrate. For active matrix displays, CMOS circuits are transferred in this way to glass substrates, and active matrix liquid crystal displays with pixel format of 1280 by 1024 (with 1000 lines per inch) have been successfully formed. Photovoltaic circuits have also been transferred to glass and to other photovoltaic devices to further the formation of multi-bandgap tandem structures. LED arrays have been formed successfully by this technique as well. This work shows the potential for combining CMOS and III-V circuits to form integrated optical input and output devices, as well as optical power delivery to silicon circuits. We review progress in these areas and suggest new applications of the technology.

Eyewear-based displays for personal electronics

This paper addresses the development of eyewear based displays for portable, personal electronics. The personal electronic system applications include the wearable personal computer, portable digital video disk player, and the cellular telephone. We describe progress on integrated eyewear systems, as well as on clip-on systems that can attach to ordinary eyewear. We conclude with a short description of a system that will include a camera, display, and audio system.