As one of popular immersive Virtual Reality (VR) systems, stereoscopic cave automatic virtual environment (CAVE) system is typically consisted of 4 to 6 3m-by-3m sides of a room made of rear-projected screens. While many endeavors have been made to reduce the size of the projection-based CAVE system, the issue of asthenopia caused by lengthy exposure to stereoscopic images in such CAVE with a close viewing distance was seldom tangled. In this paper, we propose a light-weighted approach which utilizes a convex eyepiece to reduce visual discomfort induced by stereoscopic vision. An empirical experiment was conducted to examine the feasibility of convex eyepiece in a large depth of field (DOF) at close viewing distance both objectively and subjectively. The result shows the positive effects of convex eyepiece on the relief of eyestrain.
A method has been proposed to realize a transparent volumetric display using multiple mini-projectors and a rotating screen. Correct two-dimensional cross-sectional images are projected on a bidirectional scattering projection screen, which rotates to form a three-dimensional (3-D) image due to human vision persistence. An illumination subsystem is designed to ensure the accurate synchronization between the projectors and the rotating screen. Therefore, low-speed and low-cost miniature display devices can be used in the mini-projectors to realize dynamic volumetric imaging, which can satisfy all criteria of real 3-D vision with full color and high resolution. Experimental results of volumetric imaging realized by this method are also presented.
A light field head-mounted display (LF-HMD) using a micro structure array (MSA, lens array or pinhole array) is proposed to realize true three dimensional (3D) display. Dense light field of 3D scene is generated inside the exit pupil of HMD and the viewer can obtain correct depth. This method not only solves the huge data problem in true 3D displays, but also alleviates the visual fatigue in traditional HMDs. Design considerations of LF-HMD system have been analyzed in detail and an optical see-through LF-HMD has been designed using a wedge-shaped freeform prism cemented with a freeform lens and a pinhole array. The experimental result shows that the proposed method is capable of generating a dense light field to obtain a corrected perception of depth.
Visible Light Communications (VLC) has become an emerging area of research since it can provide higher data
transmission speed and wider bandwidth. The white LEDs are very important components of the VLC system, because it
has the advantages of higher brightness, lower power consumption, and a longer lifetime. More importantly, their intensity
and color are modulatable. Besides the light source, the optical antenna system also plays a very important role in the VLC
system since it determines the optical gain, effective working area and transmission rate of the VLC system. In this paper,
we propose to design an ultra-thin and multiple channels optical antenna system by tiling multiple off-axis lenses, each of
which consists of two reflective and two refractive freeform surfaces. The tiling of multiple systems and detectors but with
different band filters makes it possible to design a wavelength division multiplexing VLC system to highly improve the
system capacity. The field of view of the designed antenna system is 30°, the entrance pupil diameter is 1.5mm, and the
thickness of the system is under 4mm. The design methods are presented and the results are discussed in the last section of
this paper. Besides the optical gain is analyzed and calculated. The antenna system can be tiled up to four channels but
without the increase of thickness.
Two types of fisheye lenses for automobile navigation are designed with slope-constrained Q-type aspheres. Special
requirements have been considered in the design process, and Q-type surfaces are introduced by converted from other
kinds of aspheric description with only coefficients of low-order terms retained. A possible problem of imaging the first surface onto the sensor has also been analyzed. As a result, as for the six-element fisheye lens, MTF is greater than 0.3 at
45lp/mm, f-θ distortion is less than 0.03 when the focal length is calibrated, field of view is 230° and full field relative
illumination is greater than 0.4. For the four-element fisheye lens, MTF is greater than 0.4 at 45lp/mm, f-θ distortion is
less than 0.16 , field of view is 190° and full field relative illumination is greater than 0.6. The design results show that the Q-type surfaces employed in fisheye lenses can make the system more compact, lightweighted and easier to