Recent Advances in Telexistence
Susumu TACHI, Ph.D.
Professor, The University of Tokyo
Department of Information Physics & Computing
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 Japan
http://www.star.t.u-tokyo.ac.jp/
Abstract. Telexistence is fundamentally a concept named for the technology that enables a human being to have a real-time
sensation of being at a place other than where he or she actually exists, and to interact with the remote environment, which may
be real, virtual, or a combination of both. It also refers to an advanced type of teleoperation system which enables an operator at
the control to perform remote tasks dexterously with the feeling of existing in a surrogate robot. Although conventionaltelexistence systems the author proposed back in 1980 provide an operator the real-time sensation of being in a remoteenvironment, persons in the remote environment have only the sensation that a surrogate robot is present, not the operator.
Mutual telexistence aims to solve this problem so that the existence of the operator is apparent to persons in the remoteenvironment by providing mutual sensations of presence. This enables humans to be seemingly everywhere at the same time,i.e., to be virtually ubiquitous. In this paper, recent advances in telexistence technology is reviewed with special focus on mutual
telexistence using RPT (Retro-reflective Projection Technology) and telexistence communication using immersive booth dubbed
TWISTER (Telexistence Wide-angle Immersive STERoscope).
Keywords: telexistence, tele-existence, telepresence, mutual telexistence, Retro-reflective Projection Technology (RPT),
Head-Mounted Projector (HMP), TWISTER (Telexistence Wide-angle Immersive STERoscope), TELESAR (TELExistence
Surrogate Anthropomorphic Robot)

1. Introduction
Telexistence (tele-existence) is a technology thatenables us to control remote objects andcommunicate with others in a remote environment
with a real-time sensation of presence by using
surrogate robots, remote/local computers, andcybernetic human interfaces. This concept has
been expanded to include the projection of ourselves
into computer-generated virtual environments, andalso the use of a virtual environment for theaugmentation of the real environment.
Before the concept of telexistence was proposed,
there were several systems that aimed for a similar
goal. In the U.S., Sutherland [1] proposed the firsthead-mounted display system, which led to the birthof virtual reality in the late 1980s. In Italy, C.
Mancini et al. [2] developed a mobile teleoperated
robot system, Mascot, as early as the 1960s. In
France, J. Vertut et al. [3] developed a teleoperation
system that controlled a submarine for deep
submergence technology in 1977. Although theseremote robots were not a humanoid type and nosensation of presence was provided in a strict sense,

the systems were closely related to the concept oftelexistence, and can be regarded as its forerunner.
In order to intuitively control a remote humanoid
robot, it is important to locally provide the operator anatural sensation of presence as if the operator felt
directly in the remote site, by means of visual,auditory, tactile, and force sensations. The concept ofproviding an operator with a natural sensation ofpresence to facilitate dexterous remote robotic
manipulation tasks was called “telepresence” by
Minsky [4] in USA and “telexistence” by Tachi et al.
[5] in Japan.
The concept of telexistence was proposed andpatented in Japan in 1980 [6], and became thefundamental guiding principle of the eight year
Japanese National Large Scale Project of "Advanced
Robot Technology in Hazardous Environments,"
which was initiated in 1983 together with theconcept of Third Generation Robotics. Through thisproject, we made theoretical considerations,established systematic design procedures, developed
experimental hardware telexistence systems, anddemonstrated the feasibility of the concept.
Through the efforts of twenty years of research anddevelopment in the U.S., Europe and Japan [7-23], it
has nearly become possible for humans to use ahumanoid robot in a remote environment as if it wasan other self, i.e. they are able to have the sensationof being just inside the robot in the remoteenvironment.
Although existing telexistence systems succeeded inproviding an operator a real-time sensation of being
in a remote environment, human observers in the
remote environment did not have the sensation thatthe human operator is presented, but only a surrogate
robot. Mutual telexistence addresses this problem sothat the existence of the operator is apparent by
persons in the remote environment by providing
mutual sensations of presence [24-26].
This paper describes recent advances in telexistence,
which fuses robotics, virtual reality and network
technology. A telexistence system using RPT(Retro-reflective Projection Technology) and ahumanoid robot with retro-reflective covering has
been proposed and proved to be a promising
approach toward the realization of mutual
telexistence. Another approach is the development of
TWISTER (Telexsistence Wide-Angle Immersive
STEReoscope), a 360-degree immersive full-color
cylindrical display with stereoscopic vision without
requiring specialized eyewear, designed forface-to-face telecommunication as if users exist in
the same virtual 3D space.

Our first report [5, 8] proposed the principle of thetelexistence sensory display, and explicitly definedits design procedure. The feasibility of a visualdisplay with a sensation of presence wasdemonstrated through psychophysical measurements
using experimental visual telexistence apparatus.
A method was also proposed to develop a mobile
telexistence system that can be driven remotely withboth an auditory and visual sensation of presence.
A prototype mobile televehicle system wasconstructed and the feasibility of the method wasevaluated [12].

Fig.1 Concept of Telexistence.

In 1989, a preliminary evaluation experiment oftelexistence was conducted with the first prototype
telexistence master slave system for remotemanipulation. An experimental telexistence system
for real and/or virtual environments was designed
and developed, and the efficacy and superiority ofthe telexistence master-slave system overconventional
master-slave
systemswasdemonstrated experimentally [13, 14, 15].

Technology based on the concept of networked
telexistence enables users to meet and talk as if theyshare the same space and time, even if they are farapart from each other, as a natural progression fromthe telephone to the telexistence-videophone.

2. History of Telexistence
Figure 1 shows the concept of telexistence in realenvironments, virtual environments, and the realenvironment through a virtual environment(augmented telexistence). The following describes
the research and development conducted in order torealize the concept.

Fig. 2 Telexistence Surrogate Anthropomorphic Robot(TELESAR) at Work (1988).

Augmented telexistence can be effectively used innumerous situations. For instance, to control a slave
robot in a poor visibility environment, an
experimental augmented telexistence system wasdeveloped that uses a virtual environment model
constructed from design data of the real environment.
To use augmented reality in the control of a slave
robot, a calibration system using image
measurements was proposed for matching the realenvironment and the environment model [16, 17].

Fig. 4 Telexistence Master (1989).

The slave robot has an impedance control
mechanism for contact tasks and to compensate forerrors that remain even after calibration. An
experimental operation in a poor visibility
environment was successfully conducted by using ahumanoid robot called TELESAR (TELExistence
Surrogate Anthropomorphic Robot) (Fig.2) and its
virtual dual. Figure 3 shows the virtual TELESAR
used in the experiment and Figure 4 shows themaster system for the control of both real TELESAR
and virtual TELESAR.

Telexistence technology was adapted in the national
five-year Humanoid Robotics Project (HRP)
sponsored by the Ministry of Economy, Trade andIndustry (METI) to develop a new type of cockpit
system to control a humanoid bipedal robot, asshown in Figure 5. The telexistence cockpit wascompleted for this project in March 2000 (Fig 6). It
consists of three main subsystems: an audio/visualdisplay subsystem, a teleoperation master subsystem,
and a communication subsystem between the cockpit
and the humanoid robot [20, 21, 22, 23].

Experimental studies of tracking tasks demonstrated
quantitatively that a human being can telexist in aremote and/or a computer-generated environment byusing the dedicated telexistence master slave system[15].
A networked telexistence paradigm called R-cubed(Real-time Remote Robotics) was proposed in 1985,
and several pertinent ongoing research efforts arebeing conducted, including a real-time remote robot
manipulation language dubbed RCML [18, 19].
Fig.5 HRP Humanoid Robot at Work (2000).

Various teleoperation experiments using thedeveloped telexistence master system confirmed thatkinesthetic presentation through the master systemwith visual imagery greatly improves both theoperator's sensation of walking, and dexterity atmanipulating objects.

Fig. 3 Virtual TELESAR at Work (1993).

If the operator issued a command to move the robot,
the robot actually walked to the goal. As the robot
walked around, real images captured by a wide fieldof view multi-camera system were displayed on four
screens of the surrounded visual display. This madethe operator feel as if he or she was inside the robot,

walking around the robot site.

human user B is present. The user B in turn uses
another telexistence robot B', which exists in the sitewhere the user A works. 3-D images of the remotescenery are captured by cameras on board both
robots A' and B', and are sent to the HMP’s of humanusers A and B respectively, both with a sensation ofpresence. Both telexistence robots A' and B' are seen
as if they were their respective human users by
projecting the real image of the users onto theirrespective robots.
Motion Control / Tactile Control
Visual & Auditory Information

Fig.6 Telexistence Cockpit for Humanoid Control (2000).

A CG model of the robot in the virtual environment
was represented and updated according to the current
location and orientation received from sensors on thereal robot. The model was displayed on thebottom-right screen of the surround visual display,and by augmenting real images captured by thecamera system, it supported the operator's navigationof the robot. Since the series of real images
presented on the visual display are integrated withthe movement of the motion base, the operator feels
the real-time sensation of stepping up and down.

HMP

3D image observed by
Telexistence Robot B’is projected and observedby Human User B witha sensation of presence.

3D image observed by
Telexistence Robot A’
is projected and observed by
Human User A with asensation of presence.

Human
User A

Telexistence
Robot A’

Telexistence Robot B’
Telexistence Robot B’ isobserved as if it is Human
User B by the projectionof real image of B on
the robot B’.

Telexistence Robot A’ is HMP
observed as if it is Human
User A by the projectionof real image of A on
the robot A’.

Human
User B

Visual & Auditory Information
Motion Control / Tactile Control

Fig. 7 Concept of Robotic Mutual Telexistence (adopted from[24]).

Persons can control the robot by just moving theirbodies naturally, without using verbal commands.
The robot conforms to the person’s motion, andthrough sensors on board the robot the human cansee, hear and feel as if they sensed the remoteenvironment directly. Persons can virtually exist in
the remote environment without actually being there.
For observers in the remote environment, however,the situation is quite different: they see only the robot
moving and speaking. Although they can hear thevoice and witness the behaviour of the humanoperator through the robot, it does not actually look
like him or her. This means that the telexistence is
not yet mutual. In order to realize mutual
telexistence, we have been pursuing the use of
projection technology with retro-reflective material
as a surface, which we call RPT (Retro-reflective
Projection Technology) [24, 25, 26].
By using RPT, the problem can be solved as shownin Figure 7 [24]: suppose a human user A uses his
telexistence robot A' at the remote site where anotherFig. 8 (A) Miniature of the HONDA Humanoid Robot,(B) Painted with Retro-reflective Material,(C) Example of Projecting a Human onto it,(D) Another Example (adopted from [24]).

Figure 8 presents an example of how mutual
telexistence can be achieved through the use of RPT.
Figure 8(A) shows a miniature of the HONDA
Humanoid Robot, while Figure 8(B) shows the robotpainted with retro-reflective material. Figures 8 (C)and (D) show how they appear to a human wearing
an HMP. The telexisted robot looks just like thehuman operator of the robot, and telexistence can benaturally performed [24].
However, thispreliminary experiment was conducted off-line, andreal-time experiments are yet to be conducted byconstructing and using a mutual telexistence
hardware system [25,26].
In order to verify the feasibility of the proposed
method, an experimental hardware system wasconstructed [27]. Figure 9 shows its schematic
diagram. In the figure, human user A tries totelexist in a remote environment [B] from a local
cockpit (A) using a robot A'. Human A is in thelocal cockpit (A), where his head motion ismeasured by ADL1 (Shooting Star Technology, Inc.),a mechanical goniometer with six-DOF (Degrees ofFreedom). He observes the remote environment[B] through a back projection display in the cockpit,
while his figure is captured by a stereo-camera
mounted on a newly designed and constructed
six-DOF torso servomechanism.

tracked motion of human B.
The stereo torso camera mechanism has six degrees
of freedom and is designed to track seated humanmotion at frequencies up to 1.3Hz. Two parallel
cameras are placed 65 mm apart from each other,each with a horizontal field of view of 45 degrees.
Figure 10 shows a general view of the 6-DOF
goniometer with HRP. The HRP's weight (1.65kg) is
fully counterbalanced by a weight and spring, while
six degrees of head motion (up/down, left/right,
back/forth, pitch, roll and yaw) are fully unrestricted.
For the positioning, spherical coordinates are usedwith translational motion of 980~1580 mm, basepitch of –15~15 degrees, and base yaw of –180~180
degrees, while orientation is realized using athree-axis pivot with pitch of -60~60 degrees, roll of-90~90 degrees, and yaw of -30~30 degrees.

Fig. 9 Schematic Diagram of the Robotic Mutual Telexistencesystem Experimentally Constructed [27].

Fig. 10 General View of Head-Mounted Projector (HMP)
suspended by Counter-balanced Goniometer with 6-DOF. [27]In a remote environment [B], a robot built using
PA-10 (Mitsubishi Heavy Industry Co.) as a headmotion mechanism, is covered with a screen withretro-reflective material. Images captured by acamera inside the screen robot's head are sent to therear projection display in the local cockpit. A
human observer B sees the screen robot using HMP(Head-Mounted Projector). His head movement ismeasured by a recently designed and constructed
six-DOF counter-balanced position/orientation
measurement system. The human observer B'shead motion is sent to the local cockpit, where a
torso stereo camera is controlled according to the

Figure 11 indicates a general view of the constructed
HMP. It consists of two 0.7-inch full-colour LCD
projectors with a resolution of 832x624, two
pinholes, and an acrylic half mirror. The horizontal
field of view of the projector is 60 degrees.
Figure 12 shows the dimensions and mechanism of
the constructed telexistence screen robot. The torsoof the robot is fixed and does not move, while using
a robot manipulator PA10 its head can move up anddown, left and right, back and forth, and rotate pitch,roll and yaw. The robot is covered with

retro-reflective material, including the bellows
connecting its head and torso.

The black dot on the surface of the head of the robot
indicates the location of the camera. The head iscontrolled so that the point always coincides with thelocation of the left eye of the human user A.

Fig. 11 General View of Head-Mounted Projector (HMP) used inthis configuration.

Fig. 13 Experimental Results: (1a, 1b) Human User A at Local
Fig.12 Configuration of Retro-reflective Screen Robot.

Cockpit(A), (2a, 2b) Human User B and Telexistece Robot A' in
Environment[B], and (3a, 3b) the image of the human user A on

A video camera is mounted on top of the mechanism
32.5 mm shifted from the center, where a hole with adiameter of 7 mm is open on the surface of the head. The
captured image is sent to the human user A. The motionof the screen robot is controlled to follow the motion of thehuman user A.

An example of the experimental results is shown in
Figure 13. In Figure 13 (1a, 1b) Human User A is at
the Local Cockpit(A), and his motion is measured by
ADL1. He moves to the left in (1b). In Figure 13 (2a,2b) Human User B and Telexistence Robot A' arefacing each other in Environment [B]. The robot
moves to the left according to the motion of Human
User A.
Figure 13 (3a, 3b) shows the image of the humanuser A on the robot A'. The image is still on thesurface of the robot head when it is moved to the left.

the robot A'.

A black dot is where the camera is located.

3. RPT: Retro-reflective Projection
Technology
In our laboratory at the University of Tokyo, a new
type of visual display is being developed called
X'tal (pronounced crystal) vision [28,29,30,31],
which uses retro-reflective material as its
projection surface. We call this type of display
technology RPT (Retro-reflective Projection
Technology) as is explained in the previous section,
which is a new approach to augmented reality (AR).
The idea was patented in 2001 and 2002, while first
demonstration of RPT together with HMP was madeat SIGGRAPH98, followed by demonstrations at
SIGGRAPH99 and SIGGRAPH2000.

Under the RPT configuration, a projector is arranged
at the axial symmetric position of a user's eye withreference to a half-mirror, with a pinhole placed in
front of the projector to ensure adequate depth offocus, as shown in Figure 14. Images are projected
onto a screen that is constructed, painted, or covered
with retro-reflective material [28].

Fig.14 The principle of RPT system.

A retro-reflective surface reflects back the projected
light only in the direction of projection, whileconventional screens normally used for IPT scatterprojected lights in all directions ideally as aLambertian surface. Figure 15 shows how aretro-reflective surface behaves. It is covered withmicroscopic beads of about 50 micrometers indiameter, which reflect the incident light back to theincident direction. It can also be realized with amicrostructure of prism-shaped retro-reflectors
densely placed on a surface.

the retro-reflector, and the pinhole in the conjugate
optical system.
By using the same characteristics of an RPT system,
binocular stereovision becomes possible using only
one screen with an arbitrary shape. An object iscovered or painted with retro-reflective material to
be used as the screen. The light projected by the rightprojector is retro-reflected on the surface of thedisplay unit and is observed by the right eye, while
the light projected by the left projector isretro-reflected also by the same display surface andcan be observed by the left eye.
RPT can provide a way to change any physicalobject into a virtual object simply by covering its
surface with retro-reflective material. Figure 16
shows, for example, how optical camouflage can beachieved using real-time video information. The coatis made of retro-reflective material so that the
coming light is reflected back to the same directionthat it comes from. Microscopic beads on the surfaceof the coat have the function of retro-reflection.
A half mirror as is shown in Fig.14 makes it possible
for a spectator to see virtually from the position of
the projector. An HMP projects an image of the
background scenery captured by the video camera
behind the camouflaged subject. A computer
calculates the appropriate perspective and transforms
the captured image to the image to be projected on
the subject using image-based rendering techniques.
Thus, an observer looking through a half mirror seesa very bright image of the scenery so that he isvirtually transparent.

Fig. 15 Retro-reflective surface densely covered with microscopic
beads with about 50 micrometer diameter. Ideally, the refractive
index should be 2.

The retro-reflector screen, together with the pinhole,ensures that the user always sees images withaccurate occlusion relations. In the construction ofan RPT system, screen shapes are arbitrary, i.e., any
shape is possible. This is due to the characteristics of

Fig.16 Optical camouflage using RTP..

4. TELESAR 2 (TElLExistence Surrogate
Anthropomorphic Robot Mark 2)
The principle of mutual telexistence using RTP has been
proposed [24] and its feasibility has been demonstrated[27] as is described in Section 2. However, in order torealize a practical mutual telexistence system using RTP,
it is necessary to construct a hardware robot system
which is capable of working as both a retro-reflective
screen and telexsitence surrogate robot.
At Tachi Laboratory of the University of Tokyo ananthropomorphic
robot
calledTELESAR
2(TELExistence Surrogate Anthropomorphic Robot Mark2) and a master cockpit for the control of the robot are
being constructed.
The robot consist of two 7-DOF arms, two 5-fingered
hands, a 3-DOF neck mechanism, torso, and a head withstereo cameras, microphones and a speaker. Fig.17
shows a conceptual system and real hardware so far
constructed.
The robot will be covered withretro-reflective material to be projected an image of auser of the robot.

Slave Hand

HMP
Master Arm

Conceptual Image
Master Hand
Fig.18 TELESAR2 Master System.

5. Mutual Telexistence using TWISTER:
TelexistenceWide-angle
Immersive
STEReoscope
Another approach to mutual telexistence without theuse of robotics can be taken if we restrict our
purposes only to communication. The basic idea [18]is shown in Fig. 19. Each human user stands insideof a booth with a rotating cylindrical mechanism thatplays the role of both a display device and an input
camera device to capture moving pictures of the user
inside the booth. Each user can see the three
dimensional figures of other users working inreal-time in the mutual virtual environment.
This concept was first proposed in 1996, and a
preliminary experiment successfully demonstrated
the feasibility of the idea [33].

Slave Arm

Conceptual Image
Fig. 17 TELESAR2 Slave system.
Figure 18 shows the master system for TELESAR2. It
consists of two master arms with 6 DOF force feedback
mechanism and 7 DOF measurement system, two 4
fingered master hand, and an HMP mounted on a 6 DOF
goniometer.
The master slave system is controlled by using
impedance based bilateral control [32].

In general, in order to display three-dimensional
objects for an arbitrary viewpoint outside a closed
surface, ray information is required from a sufficientvariation of directions inward, and at points ofsufficient density over a closed surface separating
the observer and the object. However, it is difficult
to capture images from continuous viewpoints
simultaneously because each camera occupies
physical space. To increase the number ofviewpoints, we considered two approaches: toreduce the camera size, and to exploit the camera's
motion.

user can see the three dimensional figures of otherusers working in real-time in the mutual virtualenvironment [18,34].
We implemented the display partially as a series ofapparatus dubbed TWISTER (Telexistence Wideangle Immersive STERoscope) from model I
through Model IV, and confirmed its performance asa stereoscopic display of full-color images [35-37].
TWISTER has a rotating display and camera units
surrounding the observer. One unit consists of two
LED (Light-Emitting Diode) arrays, a parallax
barrier, and a camera. Each LED array consists ofpairs of red, green, and blue LEDs, and displays
time-varying patterns so that the observer canperceive an image. Due to the use of LEDs,
TWISTER can be used as a display of high intensity
full-color images, even in a bright room.

Fig. 19 Basic Idea of Mutual Telexistence Booth(Adpoted from [18]).

For capturing a human figure in real-time anddisplaying it in a virtual environment with a virtual
viewpoint given by a user, the rendering PC
calculates the regions of each camera image used for
multi-texture-mapping. The information of theregion is sent to the control PC and used as anindication of the video switch. The switch timing is
synchronized with the camera scanning, and thecamera scanning direction is vertical. In this way,
the rendering PC can selectively capture thenecessary column image from the cameras.
Then, the captured images are texture-mapped onto aplane at a corresponding focal distance in the virtual
three-dimensional space. This process is equivalent
to the simple memory copy. Finally, the rendering
PC renders the scene with 3D graphics. One cycleof all these processes completes within video rate
(1/30[sec]), so the system realizes real-timerendering.
The basic idea of this form of mutual telexistence isthe projection of human beings into a mutual virtualenvironment in real-time. With multiple booths, each

The rotation of the display unit makes it awide-angle display. In fact, the angle of view as anormal display is 360 degrees. In addition, since thehorizontal and temporal resolutions of this display
are determined by the period of LED emission, thespatio-temporal resolution can be adaptive andoptimized to the subject (Fig.20).

Fig.20 Principle of autosteropsis using moving parallax
barrier.

The key device for autostereopsis is the parallax
barrier. One of the LED arrays is for the left eye, andthe other is for the right eye. Because the parallax
barrier obscures LED emission from the opposite
side, different images are shown to the left and righteyes. The angle of view as a stereoscopic display
depends on the direction and the position of theobserver. If the head of the observer is fixed, it
exceeds 120 degrees in an ideal condition. On theother hand, if the observer always faces the center ofthe image region of interest, it can be 360 degrees.
With the moving parallax barriers, the crosstalk
between the left eye image and the right eye image isreduced to almost zero, which gives it a powerfuladvantage over other stereoscopic vision systems.
Since the rotating unit has cameras on it, you cancapture the image of the observer simultaneously.
With this system, the face of the observer is clearly
captured, and natural non-verbal communication
between multiple booths is achieved when the image
data is transferred in real-time.
The rotator of TWISTER rotates counterclockwise(viewed from the top) at a constant speed of about
one revolution per second. The sync signal isgenerated when a photo detector attached to therotator senses the light from a photo diode attachedto the framework.

Fig.22 Preliminary Experimental TelexistenceCommunication using TWISTER II (2001).

Communication experiments exemplified in Fig. 19
are being conducted connecting TWISTER III andIV.

Fig.23 General view of TWISTER II (2001).
Fig.21General view of TWISTER II (2001).

We have already achieved full-color presentation of
3D images. With LEDs, it can easily be seen in awell-lit room. The capabilities for autostereopsis
without eyewear, and panoramic (360degree)presentation of normal three-dimensional images
have been also confirmed. The result wasdemonstrated at SIGGRAPH 2001 (Fig.21, Fig.22).
Figure 23 indicates a general view of a newly
developed TWISTER IV with both 360-degree
display and camera capabilities.

It is also possible to use TWISTER as a cockpit ofmutual telexistence using robots, as is show in
Fig.24. In the figure pictures of a user A is captured
by TWISTER and sent to a robot, which sends theimage to humans wearing HMP. The HMP projects
the image on the robot to show the figure of the userA.
Human positions and orientation measured by the
robot are sent to TWISTER to determine the images
that should be transmitted.
Human A can control the robot as if he is presented

by utilizing visual, auditory and tactile information
with a sensation of presence.

Fig.24 Schematic diagram of TWISTER used as a
cockpit for robotic mutual t elexistence.

6. Conclusions
In this keynote paper, a history of telexistence wasreviewed, the principle of RPT was explained, andan experimental mutual telexistence system using
RPT, which was designed and constructed todemonstrate its feasibility and efficacy, wasintroduced. It was also demonstrated that an
immersive auto stereoscopic booth called TWISTER
can be used as a promising device not only for thepresentation of three-dimensional images but also forthe device of the future telecommunication as
telexistence videophone by capturing three
dimensional images of the user in real-time.

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[15] S.Tachi and K.Yasuda: Evaluation Experiments of aTele-existence Manipulation Sysytem, Presence, vol.3,
no.1, pp.35-44, 1994.
[16] Y.Yanagida and S.Tachi: Virtual Reality System with
Coherent Kinesthetic and Visual Sensation of Presence,
Proceedings of the 1993 JSME International Conference
on Advanced Mechatronics (ICAM), pp.98-103, Tokyo,
Japan, August 1993.
[17] K.Oyama, N.Tsunemoto, S.Tachi and T.Inoue:
Experimental study on remote manipulation using virtual
reality, Presence, vol.2, no.2, pp.112-124, 1993.

[18] S.Tachi: Real-time Remote Robotics- Toward
Networked Telexistence : IEEE Computer Graphics andApplications, vo.18, Nov-Dec98, pp.6-9, 1998.
[19] Y.Yanagida, N.Kawakami and S.Tachi: Developmentof R-Cubed Manipulation Language - Accessing realworlds over the network, Proceedings of the 7thInternational Conference on Artificial Reality andTele-Existence (ICAT'97), pp.159-164, Tokyo, Japan,
December 1997.
[20] T.Nishiyama, H.Hoshino, K.Suzuki, R.Nakajima,
K.Sawada and S.Tachi, "Development of Surrounded
Audio-Visual Display System for Humanoid Robot
Control", Proc.of 9th International Conference ofArtificial Reality and Tele-existence (ICAT'99), pp.
60-67, Tokyo, Japan, December 1999.
[21] T.Nishiyama, H.Hoshino, K.Suzuki, K.Sawada and
S.Tachi, "Development of Visual User Interface
Embedded in Tele-existence Cockpit for Humanoid Robot
Control", Proc. of IMEKO 2000 World Congress, Vol.XI(TC-17 & ISMCR2000), pp.171-176, Vienna, Austria,
September 2000.
[22] S.Tachi, K.Komoriya, K.Sawada, T.Nishiyama,
T.Itoko, M.Kobayashi and K.Inoue: Development ofTelexistence Cockpit for Humanoid Robot Control,
Proceedings of 32nd International Symposium on
Robotics (ISR2001), pp.1483-1488, Seoul, Korea, April
2001.
[23] S.Tachi, K.Komoriya, K.Sawada, T.Nishiyama,
T.Itoko, M.Kobayashi and K.Inoue: Telexistence Cockpit
for Humanoid Robot Control, Advanced Robotics, Vol 17,
No. 3, pp. 199-217 (2003)[24] S.Tachi: Augmented Telexistence, Mixed Reality,
pp.251-260, Published by Springer-Verlag, 1999.
[25] S.Tachi: Toward Next Generation Telexistence,
Proceedings of IMEKO-XV World Congress, vol.X(TC-17 & ISMCR'99), pp.173-178 , Tokyo/Osaka, Japan,
June 1999.
[26] S.Tachi: Toward the Telexistence Next Generation,
Proceedings of the 11th International Conference on
Artificial Reality and Tele-Existence, (ICAT2001), pp.1-8,
Tokyo, Japan, December 2001.
[27] S.Tachi, N.Kawakami, M.Inami and Y.Zaitsu:
Mutual Telexistence System Using Retro-Reflective
Projection Technology, International Journal of
Humanoid Robotics, Vol. 1, No. 1, pp. 45-64, 2004.
[28]] N.Kawakami, M.Inami, T.Maeda and S.Tachi:
Media X'tal -Projecting virtual environments on
ubiquitous object-oriented retro-reflective screens in thereal environment-, SIGGRAPH'98, Orlando, FL, July

1998.
[28] M.Inami, N.Kawakami, D.Sekiguchi, Y.Yanagida,
T.Maeda and S.Tachi: Visuo-Haptic Display using
Head-Mounted Projector, Proceedings of IEEE Virtual
Reality 2000, pp.233-240, New Brunswick, NJ, March
2000.
[29] M. Inami, N. Kawakami, Y. Yanagida, T. Maeda and
S. Tachi, Method of and Apparatus for Displaying an
Image, US PAT. 6,283,598, September 4, 2001.
[30] M. Inami, N. Kawakami, Y. Yanagida, T. Maeda and
S. Tachi, Method and Device for Providing Information,
US PAT. 6,341,869, January 29, 2002.
[31] S.Tachi: Two Ways of Mutual Communication:
TELESAR
and
TWISTER,in
S.Tachied.
Telecommunication, Teleimmersion and Telexistence,
IOS Press, ISBN 1-58603-338-7, pp. 3-24, 2003.
[32] R.Tadakuma, K.Sogen, H.Kajimoto, N.Kawakamiand S.Tachi: Development of Multi-D.O.F. Master-Slave
Arm with Bilateral Impedance Control for Telexistence,
Proceedings of the 14th International Symposium on
Measurement and Control in Robotics (ISMCR2004),
pp.D21.1-D21.5, Houston, Texas, September 2004.
[33] S.Tachi, T.Maeda, Y.Yanagida, M.Koyanagi and H.
Yokoyama: A Method of Mutual Tele-Existence in a
Virtual Environment, Proceedings of the 6th International
Conference on Artificial Reality and Tele-Existence,(ICAT'96), pp.9-18, Makuhari, Chiba, Japan November
1996.
[34] Y.Kunita, M.Inami, T.Maeda and S.Tachi: Real-TimeRendering System of Moving Objects, Proceedings of1999 IEEE Workshop on Multi-View Modeling andAnalysis of Visual Scenes, pp. 81-88, Colorado, USA,
June 1999.
[35] Y.Kunita, N.Ogawa, A.Sakuma, M.Inami, T.Maeda
and S. Tachi: Immersive Autostereoscopic Display for
Mutual Telexistence: TWISTER I (Telexistence
Widw-Angle Immersive STEReoscope Model I),
Proceedings of IEEE Virtual Reality 2001, pp. 31-36,
Yokohama, Japan, March 2001.
[36] K.Tanaka, J.Hayashi, Y.Kunita, M.Inami, T.Maeda
and S.Tachi: The Design and Development of TWISTER
II: Immersive Full-color Autosteroscopic Display,
Proceedings of the 11th International Conference on
Artificial Reality and Tele-Existence, (ICAT2001),
pp.56-63, Tokyo, Japan, December 2001.
[37] K.Tanaka, J.Hayashi, M.Inami, and S. Tachi:
TWISTER: An Immersive Autostereoscopic Display,
Proceedings of IEEE Virtual Reality 2004, pp.59-66,
Chicago, Illinois, March 2004.