Aerial Image on Retroreflective Particles
Shinnosuke Ando

Kazuki Otao

Kazuki Takazawa

University of Tsukuba
Pixie Dust Technologies, Inc.
sinnoando@gmail.com

University of Tsukuba
Pixie Dust Technologies, Inc.

University of Tsukuba
Pixie Dust Technologies, Inc.

Yusuke Tanemura

Yoichi Ochiai

University of Tsukuba
Pixie Dust Technologies, Inc.

University of Tsukuba
Pixie Dust Technologies, Inc.
wizard@slis.tsukuba.ac.jp(a)(b) 03060

Figure 1: (a) Image of SIGGRAPH logo projected on our proposed screen. (b) Images of fire (We took the same image at 0◦ , 30◦and 60◦ .

CCS CONCEPTS• Hardware → Displays and imagers;

KEYWORDS
Passive display, Projection, Retroreflection, Aerial screen
ACM Reference format:
Shinnosuke Ando, Kazuki Otao, Kazuki Takazawa, Yusuke Tanemura, and Yoichi
Ochiai. 2017. Aerial Image on Retroreflective Particles. In Proceedings of SA’17 Posters, Bangkok, Thailand, November 27-30, 2017, 2 pages.
https://doi.org/10.1145/3145690.3145730

1INTRODUCTION

Many kinds of methods can be used to render aerial images. Amongthese, fog screens[Rakkolainen et al. 2005] have been used as primary diffusers of passive aerial display. In this type of display systems, diffusers are generated by the fog generator, and the projector projects images onto the fog. However, there are some issues
to be considered. The first problem is that the equipment is largeand heavy. The second is that the screen is not stable because of
low wind tolerance. Aerosol-based screens[Suzuki et al. 2017] canresist the wind and exhibit a high portability. However, there arelimits on the size and the time to project.

SA ’17 Posters, November 27-30, 2017, Bangkok, Thailand© 2017 Copyright held by the owner/author(s).
This is the author’s version of the work. It is posted here for your personal use. Notfor redistribution. The definitive Version of Record was published in Proceedings ofSA ’17 Posters, November 27-30, 2017, https://doi.org/10.1145/3145690.3145730.

We propose a new method of rendering aerial images using retroreflective particles. Owing to the properties of the retroreflective material, it is possible to place the projector in the same direction as
the observer with respect to the screen. This has an advantage thatthe image can be observed without facing the light source. In addition, each particle is heavy enough to fall vertically due to gravity
and there is no limit on the size in this method.

2 SYSTEM OVERVIEW
Figure 2 (a) shows the system overview of our proposed display.
This system consists of retroreflective particles, a device to control
the fall of retroreflective particles, and the laser projector. We drop
retroreflective particles from the control device, and project aerial
images from the observer’s side.
Retroreflective particles consists of glass beads and reflective films.
Glass beads are coated with reflective films. By coating reflectivefilms, the light from the laser projector is reflected straight backalong the same path from which it came when we drop retroreflective particles from the control device. When we drop retroreflective particles, retroreflective particles fall in various orientation.
Therefore the incident light collides directly with the reflective film
without passing through the glass beads according to a prescribedprobability. Then the incident light scatters.
Figure 2 (b) shows the system about the control device. By using
the stepper motor, it is possible to control the width of the slit. Thisdevice can be controlled in 1mm.

SA ’17 Posters, November 27-30, 2017, Bangkok, Thailand

Ando et. al.
(C)

(b)

(a)
Control device

motordriver

Arduinoglass beads
Incident light

projector

Place to drop particles

Stepper motor

Tensioner

reﬂected lightreﬂective ﬁlm

Observer

Digital camera
Laser Projector

ScreenSlit

Figure 2: (a) System overview. (b) Control device. (c) Structure of experiment to measure maximum luminance.

3 EVALUATION
3.1 Brightness

Table 1: View angle of our proposed display

We measure the light amount of the display and calculate the ratioof the light amount from the laser projector to the light amountfrom the display. Assuming that the light amount from the projector is Bb and the light amount from the display is Bd , the lightamount ratio R is given by the following formula.
B
R= dBbangle[deg]luminance[L]

0249
37.5
180.3

7.5
233.7
45
146.5

15
215.5
52.5
166

22.5
205.5
60
134.6

30
195.8

(1)

We use an optical sensor to measure the light amount. When wemeasure the light amount, we place the optical sensor at the position where the image is projected during the fall of retroreflective
particles. As a result, the ratio of the light amount is as follows.
R=697= 0.700502...
995

(2)

From the above calculations, the light amount observable by thedisplay is 70.050% of the light amount from the laser projector.

3.2

4 DISCUSSION

View Angle

We measure the maximum luminance of each angle and identify
the viewing angle of the proposed display. We project an imageof a white point from the laser projector and take a picture of theaerial image while changing the angle formed by the projector optical axis and the line of sight of the observer. (Figure 3) For the luminance measurement, we use a digital camera(α7s-2 SONY). We
fix to ISO 4000, F 3.2 and choose the pixel with the maximum luminance of each image. Luminance is measured by the following
formula. L(luminance) is the sum of each value about RGB (0 to255).
L = 0.298912 × r + 0.586611 × д + 0.114478 × b

Figure 3: View angle of our proposed display(3)

The result are shown in Table 1 and Figure 3. It is observed that themaximum luminance decreases as the angle decreases. However, it
is true that the viewing angle of our proposed display is wider thanthat of the fog display[Yagi et al. 2012]. Although the viewing angleof Pixie Dust[Ochiai et al. 2014] is wider than that of the proposed
method, the resolution of this method is higher than that of Pixie
Dust because the size of retroreflective particles is smaller.

It is dangerous if observers inhale/swallow retroreflective particles
via nose/mouse. We are considering establishing safety controls
the screen.

REFERENCES
Yoichi Ochiai, Takayuki Hoshi, and Jun Rekimoto. 2014. Pixie Dust: Graphics Generated by Levitated and Animated Objects in Computational Acoustic-potential
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1145/2601097.2601118
Ismo Rakkolainen, Stephen DiVerdi, Alex Olwal, Nicola Candussi, Tobias Hüllerer,
Markku Laitinen, Mika Piirto, and Karri Palovuori. 2005. The Interactive FogScreen.
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Ippei Suzuki, Shuntarou Yoshimitsu, Keisuke Kawahara, Nobutaka Ito, Atsushi Shinoda, Akira Ishii, Takatoshi Yoshida, and Yoichi Ochiai. 2017. Design Method for
Gushed Light Field: Aerosol-based Aerial and Instant Display. In Proceedings of
the 8th Augmented Human International Conference (AH ’17). ACM, New York, NY,USA, Article 1, 10 pages. https://doi.org/10.1145/3041164.3041170
Asuka Yagi, Masataka Imura, Yoshihiro Kuroda, and Osamu Oshiro. 2012. 360-Degree
Observable Fog Display. Transactions of the Virtual Reality Society of Japan 17, 4(2012), 409–417. https://doi.org/10.18974/tvrsj.17.4_409