We are presenting the results of a freeform HMD optical system design. The tolerancing analysis is carried out to
analyze the optical performance of this system. Results are discussed in detail.
The design of a compact optical system with good image quality for head mounted display (HMD) is particularly
demanding since the aberrations, weights, and center of gravity of the display are always critical. One more critical
requirement is its wide field of view. We are presenting two designs of an HMD optical system, which have good optical
performance while maintaining the compactness. The comparison of their optical performance and other parameters is
also presented. Freeform optical surfaces are employed in one of these designs while one aspheric and some spherical
surfaces are used in the other design. Freeform surfaces provide more degrees of freedom to design an optical system
with less number of elements and hence to reduce the weight of the overall system. Generally, HMD optical systems are
tilted and decentered in their nature; it is difficult to get rid of all the aberrations without adding extra optics in such
systems. However, freeform optics also provides enough degrees of freedom in this aspect and facilitates the designer to
overcome such limitations without additional optics. It is also mentioned that the fabrication technologies of freeform
optics are developing now and hence allow the designers to employ such optics elements in their designs. The designing
characteristics and results of the two proposed models are also discussed in this paper.
There exist great interests in using segmented mirrors instead of monoliphic primary mirror to build large aperture
telescopes. The use of segmented mirrors reduces the difficulties in fabrication, transportation and replication as well as
decreases the impact of gravity. In the meanwhile, one of the grand challenges in this approach lies in matching the
individual mirrors to yield the form of a continuous surface. The erroneous differences between the global radii of
curvature (GROC) of the segmented mirrors have significant influence on image quality. In this paper, we present a
model of segmented systems and an analysis technique which reveals the effect of these errors on the image quality. Our
analytical results show that the GROC differences have great influence on image quality and the impact remains high
despite of using active optics to compensate these errors. The local radii of curvature of individual mirror segment
should be used to correct these errors. We propose a new approach to generate compensators that controls the local
radius of curvature of each segment efficiently. Finally, through simulation results, we demonstrate that the new
compensators can dramatically reduce the effect of radius mismatch.
Mathematical and computer modeling of an optical system with a segmented mirror are designed and applied to a telescopic system. The unique feature of this presentation is to establish a center of the segments (sub-aperture arrangement) mathematically that provides six degrees of freedom (i.e. dx, dy, dz, α, β, γ) to each sub-aperture in order to input the mounting errors. To do so, a Visual Basic routine based on CODE V's COM interface is written that makes it possible to model all types of segmentation modes in a fast and convenient way. Segment results are discussed and the image quality of the design based on these results is evaluated in this paper.
The results of design effort for infrared zoom systems using all reflective aspheric surfaces are described. Issues such as
the paraxial design theory and aberration balancing are discussed in detail. Two all reflective zoom optical systems are
disclosed clearly. Both of them are to be used with uncooled infrared detectors. The first design is an unobscured three
mirror zoom system without any intermediate image, and the second is a three mirror system with central obscuration
which forms an intermediate image. With the design theory further developed, this kind of systems can be designed for
cooled infrared detectors, for which cold stop matching is an important issue.
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