Trihedral corner cube arrays are efficient retro-reflectors. They are integral parts in numerous imaging and sensing applications. However, the fabrication of these trihedral arrays can prove to be both difficult and cost prohibitive. Using a phase-only mask, we have fabricated an array of analog reflectors which can then be tiled using a photolithographic stepper. The elements are designed using a fixed period and varying fill factor to create the analog slope of each side wall. The overall depth of the array can be controlled by both the exposure and etching processes to ultimately create the desired effect. After etching, a single coating of metal finishes the process, and the elements can then be diced out and integrated into each specific application. The etched arrays may alternatively be used as a mold to create high volumes of the desired element. The design and fabrication parameters for trihedral corner cube arrays will be discussed in detail. The advantages and limitations will then be discussed.
The projection based head-mounted display (HMD) constitutes a new paradigm in the field of wearable computers. Expanding on our previous projection based HMD, we developed a wearable computer consisting of a pair of miniature projection lenses combined with a beam splitter and miniature displays. Such wearable computer utilizes a novel conceptual design encompassing the integration of phase conjugate material (PCM) packaged inside the HMD. Some of the applications benefiting from this innovative wearable HMD are for government agencies and consumers requiring mobility with a large field-of-view (FOV), and an ultra-light weight headset. The key contribution of this paper is the compact design and mechanical assembly of the mobile HMD.
Current technology trends are focused on miniaturizing displays, although for specific applications such as the use of head-mounted displays (HMD) this limits the advancements for a wider field-of-view (FOV) and a negligible overall weight of the optics. Due to the advancements of electronics that benefit from smaller miniature displays, universities and companies are focused on developing this technology to meet the growing demand of this global market. Higher resolution displays with added brightness are being developed, but these displays are decreasing in their viewable area. HMDs can benefit from these higher resolution and brighter displays but they will undergo an increased optical weight to compensate for the smaller display size. To overcome this hindrance in HMDs, we demonstrate in this paper how to incorporate microlenslet arrays as an optical relay system to magnify miniature displays. Microlenslet arrays provide respectively shorter focal length which yields a smaller overall object to image distance and an incremental overall weight compared to an otherwise increased optical lens assembly. The contribution of this paper is a patented concept of magnifying/demagnifying miniature displays with microlenslet arrays that can be integrated in a spaced limited area.
Recent investigation demonstrated the feasibility of using stacks of microlenslet arrays for optical imaging applications. Many applications driving our research require ultra-compact magnifying imaging systems. In this investigation we demonstrate that a magnifying system based on a stack of two dissimilar microlenslet
arrays is feasible.
Conventional head-mounted displays (HMDs) consisting of a pair of miniature projection lenses, beam splitters, and miniature displays mounted on the helmet, as well as phase conjugate material placed strategically in the environment have been redesigned to integrate the phase-conjugate material into a complete see-through embodiment. Some initial efforts of demonstrating the concept was followed by an investigation of the diffraction effects versus image degradation caused by integrating the phase-conjugate material internally in the HMD. The key contribution of this paper lies in the conception, and assessment of a novel see-through HMD. Finally, the diffraction efficiency of the phase-conjugate material is evaluated, and the overall performance of the optics is assessed in both object space for the optical designer and visual space for possible users for this technology.
In this paper, we investigate the design and fabrication of ultra-light weight projection lenses for color wearable displays. Driven by field of view requirements from 40 degree to 90 degrees, we employed the combination of plastic, glass, and diffractive optics to yield less than 10g optics per eye. The approach centers on the use of projection optics instead of eyepiece optics to yield most compact and high image quality designs. The implementation of the fabricated 52 degrees lens in a teleportal head-mounted display and remote collaborative environment is demonstrated. We also present the design results for a 70 degrees design.