Polarized catadioptric optics systems are an emerging solution for virtual reality (VR) head mounted displays (HMD). A good VR optical system should have a large pupil volume to tolerate multiple interpupillary distances and to accommodate eye rotation as the user scans across the field of view (FOV). In this paper we review the 3M™ High Acuity Reflective Polarizer (HARP) optical lens and module. We present empirical and modeling data for lens module performance including MTF as functions of pupil rotation, decenter, and diopter adjustment range. The large eye box and decentering tolerance yields a natural viewing experience. 3M™ HARP optics demonstrates the promise of pancake optic designs to deliver realistic immersive VR experience.
Polarized catadioptric systems (also called folded optics, pancake lenses) are a viable solution for virtual reality (VR) head-mount display applications. Reasons include its high image resolution, wide field-of-view, smaller physical size and lighter weight compared to the conventional refractive optics counterparts. One of the major challenges with folded optics systems is to reduce the light intensities of the ghost images and spurious halos due to multi-bounces, hence improve the overall image contrast. In this paper we discuss a high-quality polarized catadioptric system and present a ghost analysis method and the corresponding results. It can be shown that the many ghosts in the image plane can be coarsely categorized into “local ghosts” and “distant ghosts” according to their proximity to the image. The local ghosts or halos are close to the image itself and they directly decrease image contrast; whereas the distant ghosts are located diagonally away from the image and they can create some distracting faint images under certain display content. The origin of each individual ghost and halo can be traced back to its contributing optical components, which provides targeted information to directly mitigate them on a component level. Experimental results are shown to demonstrate the validity and efficacy of this approach. Furthermore, the ghost analysis information can also be used as additional constraints in the lens design software to perform new rounds of optimization on a system level.
II-VI semiconductors can exhibit strong photoluminescence throughout the visible spectrum and are excellent candidates
for filling the so-called "green gap". We report on the performance of green color-converted LEDs fabricated by bonding
CdMgZnSe multiple quantum well structures to high-efficiency blue-emitting GaInN LEDs. A device efficacy of 181
lm/W at 537 nm (dominant) is measured under room temperature, 350 mA/mm2 quasi-cw conditions, more than twice as
efficient as typical commercial green LEDs today. The thermal roll-off is shown to be comparable to that of typical
green GaInN LEDs. Finally, the implications of the availability of high-efficiency, narrow-band, green and yellow
emitters in display applications will be discussed.
A new method of beam shaping by spatially inhomogeneous polarization is proposed and studied. Unlike the
conventional techniques, the polarization state in the pupil plane of a far-field beam shaping system is modulated
in a spatially variant pattern. It is shown that with carefully designed polarization manipulation, the smallest
flat-top intensity focal pattern can be obtained. Theoretical analysis demonstrates the uniqueness of this new idea
in terms of the size of the flat-top spot; experiments are described that successfully demonstrate the feasibility
of this method to practical applications.
Different beam shaping techniques to obtain the flat-top focus in one-dimension have been compared. It's shown that the smallest flat-top focus can be achieved with no loss by changing the polarization of the incident beam in a spatially inhomogeneous pattern. This spatially variant polarization manipulation adds a new degree of freedom in beam shaping and predicts better and more efficient results than conventional methods.
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