Embossed Touch Display -illusory elongation and shrinking of tactile objectsHideyuki Ando∗NTT Communication
Science Laboratories

Junji Watanabe†
PRESTO Japan Scienceand Technology Agency / NTTMasashi Nakatani‡
The Universityof Tokyo

Tomohiro Amemiya* Taro Maeda*
NTT Communication
Science Laboratories

Abstract

2

The Embossed Touch Display is a novel tactile display that canpresent any given width of objects. When we touch objects in space,
we actively move our hands and fingers. Due to this active touchmovement, we can perceive the shape of an object, even though
the object may be larger than the fingertip. With the Embossed
Touch Display, when the object is moved in the same or opposite
direction of the hand movement, the width of the object is perceived
to elongate or shrink. By controlling the velocity and position of theobject during hand movement, any given width can be displayed.

In addition to the tactile function of the display, visual images canbe presented with a slider-mounted liquid crystal display. An example is the elastic moon shown in Fig. 2. The moon changes
its shape according to hand movement. When the finger is static,a static full moon is shown. When the finger moves, the moon iselongated into an ellipse. The visual and tactile edges of the moon
can totally overlap. Another demonstration of this display would
be to capture an image of a person’s face and then have that person move their finger across the facial image to make it fatter orthinner. (Both demonstrations can be experienced at our booth.) In
such ways, our display can provide new visual-tactile experiences.

CR Categories: H.5.2 [Information interfaces and presentation(e.g., HCI)]: User Interface—Haptic I/O;
Keywords: Tactile display, tactual illusion, Shape presentation

1Introduction

Demonstration

In the future, we plan to present sensations of surface texture andviscosity by changing the control strategy of the liner slider. Thisdisplay can be applied as a new tool for artistic expression. In addition, the novel tactile illusion from which we took the display principle is expected to have a great influence not only on the interface
research but also on the scientific field.
SAME direction

One way in which we explore the external world is through oursense of touch. The fingertips contain sensitive tactile sensors, andwhen the fingers touch an object and are moved across its surface,
the information sequentially presented to the fingertips is integrated
into the total shape of the object. This perceptual integration isbased on the important assumption that an object is static duringexploratory hand movements. However, if the object moves during
the hand movement, the assumption leads to an illusory perceptionof the object’s shape. As shown in Fig 1(a), when the object moves
in the same direction as the hand movement, the object is perceived
to elongate, since the width is basically judged from the initial andfinal positions of the moving edges. On the other hand, when theobject moves in the opposite direction as in Fig. 1(b), its width isperceived to shrink. Our discovery of this phenomenon led us todevelop a novel tactile display called the Embossed Touch Displaythat can provide any given width of an object by moving the object
according to the hand movement.
The Embossed Touch Display features advanced object control performed in accordance with measured hand movements. We implemented the display with a laser distance sensor and a liner slider.
The sensor measures the distance between it and the finger, andliner slider is controlled in accordance to the distance. Using
this display, we can present realistically rigid edges. We can alsopresent continuous surfaces, which is difficult for prior tactile devices.

(a) Perceptually elongated width
OPPOSITE direction

㧔b㧕Perceptually shrunk width

Figure 1: Conceptual figure of display principle.

∗ e-mail: (hide,t-amemiya,maeda)@avg.brl.ntt.co.jp† e-mail:watanabe@avg.brl.ntt.co.jp‡ e-mail:nakatani@star.t.u-tokyo.ac.jp(a) Before hand movement
veridical width(b) After hand movement
perceptually elongated width

Figure 2: An elastic moon shape.