High Resolution Tactile Display
Masashi Nakatani* Hideyuki Ando†
Junji Watanabe†
Naoki Kawakami*Susumu Tachi*(*)The University of Tokyo, Japan(*†) NTT Communication Science Laboratories, Japan
E-mail: nakatani@star.t.u-tokyo.ac.jp
1. Introduction
We proposed a tactile display which can present thesense of presence and movement of an object. To
develop the display, we chose to use a pin-matrix typetactile display whose tactors move only in the verticaldirection. The vertical indentation was decided to besuitable for this application, because it can achieve
high spatial resolution of the contactors. However, inorder to display the sense of presence and movementof an object effectively, we need to find out and utilize
the suitable resolution. Therefore we conducted anexperiment to evaluate the suitable resolution for shaperecognition with a pin matrix[1].The result suggested
that the interspacing of pin-rods should be less than 1.5mm for shape recognition: , and 1.0 mm can provide
rich enough information for recognizing the shape
underneath a pin matrix in active touch. Moreover, in
our follow-up test, suggested that the performance is
not so improved even if the resolution of the pin matrix
was made finer than 1.0 mm in our additional test.
Based on this result described above, we
determined that the vertical indentation would be theeffective stimulating method to convey tactile signal
with high resolution. In addition, we set the horizontal
resolution to be 1.0 mm, according to the shaperecognition performance of the humans.

2. Developed System
We decided to use a passive high-density pin matrix
as a tactor for representing the presence of an object
through the tactile sensory channel. This passive
device is composed of 441 (21 x 21) steel pins 0.8 mm
in diameter with arbitrary center-to-center spacing
larger than 1.0 mm. The pins' movement is constrainedby the close-tolerance holes in fiberglass boards inorder to allow free movement in the vertical directionand essentially to prohibit free motion in the verticaldirection. Each pin of the passive Pin Matrix wasdriven by using the velocity controllable motor stage
that can move only in 2D direction.

Figure 1 Proposed method to actuate apassive High-Density Pin Matrix
Tactile reconstruction with high resolution wasadopted because of the following reasons: the shapeinformation, especially the contour of an object, can bepresented more clearly and the sense of the presented
objects movement (i.e., velocity) is evoked morestrikingly with our proposed method. Also a passive
pin matrix is suitable to create moving stimulus
because of its mechanical characteristics. In otherwords, the pin matrix exhibits the "filtering effect"
originates its mechanical property, which is alreadyanalyzed in a part of related studies[2].
When developing high-density tactile display, there
are four advantages of adapting a passive pin matrix asfollows: 1. Ease to change the resolution, 2. Simple
actuation mechanism, 3. Durability and 4. Scalability.
The method we propose is really easy to increase or
decrease the number of pin-rods according to theapplication. Therefore, it is also possible to develop apalm size tactile display by just adding the pin-rods
with our proposed method.

References[1] M. Nakatani, H. Kajimoto, N. Kawakami and S. Tachi,“Tactile sensation with high-density pin-matrix”, In
Proc. of APGV ‘05, p. 169, 2005.
[2] R. Kikuuwe, A. Sano, H. Mochiyama, N. Takasue andHideo Fujimoto, "Enhancing Haptic Detection ofSurface Undulation", Trans. on Applied Perception, Vol.
2, No. 2, pp. 46-67, 2005.