X'talVisor : Full open type head-mounted projector
Tetsuri Sonoda
Tomohiro Endo
Naoki Kawakami
Sususmu Tachi
Graduate Scool of Infomation Science and Technology, The University of Tokyo{tetsuri,kawakami,tachi}@star.t.u-tokyo.ac.jp , yendo@nuee.nagoya-u.ac.jp
1.Introduction
Today, most conventional wearable stereoscopic
displays, such as liquid crystal shatter glass, HMD,
and so on suffer the practical problem of covering alarge part of the wearer's face, so that in daily use,
they hinder normal communication with surroundingpeople. Some naked eye stereoscopic displays such as
LCD with a lenticular lens array have been proposed,
but they have limited viewpoints and narrow fields ofview.
We propose a new type of head-mounted projector(HMP), named X’talVisor(fig.1) as an ideal tool for
future VR collaborative environments. The X’talVisor
is a head mounted type display with a large field ofview, yet covers little of the wearer's face, so true
“face to face” communication is not hindered by thedisplay.

with remote persons are possible as if they were closeat hand. Moreover, it is possible to perform training inmixed reality environments with the same unimpeded
feeling as in the real world, without needing largescale equipment such as flight simulators, CAVE, etc.

2.Full open type HMP
X'talVisor is a natural extension of retro-reflective
projection technology (RPT) which used in HMPSIGGRAPH '99[1]. RPT consisted of a projector,
half-mirror for reflecting projection images, and a
retro-reflective screen for image projection(fig.2).
RPT made it possible to project stereoscopic color
images to a free-form surface screen with highcontrast and brightness, but the large half-mirror
covered most of the wearer’s face.
In X'talVisor, the large half-mirror is replaced by an
all-reflective spherical micro mirror. First, the predistorted image from the projector is concentrated bya condenser lens. The mirror is placed near the focal
point of the lens so that the necessary mirror size
becomes negligible. As we used a micro sphericalmirror, the image is expanded and distorted. Since theprojected image is already pre-distorted, the image
projected to the retro-reflective screen is not distorted,
while the field of view is large(fig.3).
As the mirror size is quite small, X'talVisor candisplay images without covering the wearer's face, andtherefore enables natural open-face-to-face situations.

Fig.1 X'talVisor
To screen

diffuserlight

Beam spritter

Projection lensCondenser lensLCD panel

Eye point

Fig.2 conventional RPT optical system

To screen

LCD panel
Projection lensSpherical mirror

Condenser lens
Eye point

3.Future Work
X'talVisor is a device that allows "image experiences"Fig.3 Improved RPT optical system
to permeate deeply into our daily lives. Unlike
conventional wearable displays, 3-dimensional
References
scenography with heightened presence can be[1]M. Inami, N. Kawakami, D. Sekiguchi, Y. Yanagida, T.
experienced with the same ease and comfort as
Maeda, K. Mabuchi and S. Tachi, Head-Mounted Projector,
wearing headphones for music. For example, byACM SIGGRAPH '99 Conference Abstracts andequipping X’talVisor with a headset, conversations Applications, p.179(Emerging Technologies), 1999