Through our study of Scent Projectors, several problems have been found. One of the problems is that the user feels as if sudden wind (turbulence) come when the vortex ring hits one's face. This "turbulence effect" is caused by the local air flow of the vortex ring, rather than the velocity of entire vortex ring. As the vortex ring sooner or later collapses by itself, one option is to wait for it. However, it is difficult to deliver the scent to the intended position, as the behavior of the vortex ring just before the collapse is significantly unstable.

To solve this problem, we propose a novel approach in which vortex rings are intentionally broken by making them collide with each other while in the air. In this configuration, the scented air is carried from a nearby place to stay briefly at a certain location. After the vortex ring breaks, the turbulence effect is much smaller than when a vortex ring directly hits a user's face, thus providing a more natural olfactory experience. We named this method "SpotScents."．

First, we build a system that consists of two air cannons. Vortex rings emitted from air cannons collide with each other and collapse, leaving scented air carried by these vortex rings around the point of collision.

The relationship between the elapsed time and the travelled distance was measured in advance. If we shoot two vortex rings with time difference that corresponds to the difference of distance from two air cannons to the target point, two vortices would reach the target point simultaneously and collide. The concept of "SpotScents" and system was first presented at ACM SIGGRAPH 2005 Emerging Technologies, and the technical detail was presented at IEEE Virtual Reality 2006.

(The studies above were conducted at ATR.)

To be written.

The following videos also includes some early results, described in the page of Scent Projector. Some recent results are appended in these videos.

• ScentProjector_en_QVGA.wmv (320x240, 27MB)
• ScentProjector_en_VGA.wmv (640x480, 85MB)

• Koji Murai, Takafumi Serizawa, and Yasuyuki Yanagida: "Localized Scent Presentation to a Walking Person by Using Scent Projectors," Proceedings of the First IEEE International Symposium on Virtual Reality Innovation (ISVRI) 2011, Singapore, pp. 67-70, March 19-20, 2011.
• Fumitaka Nakaizumi, Yasuyuki Yanagida, Haruo Noma, and Kenichi Hosaka: "SpotScents: A Novel Method of Natural Scent DeliveryUsing Multiple Scent Projectors," Proceedings of IEEE Virtual Reality 2006, Alexandria, Virginia, USA, pp. 207-212, March 2006.
• Yasuyuki Yanagida, Haruo Noma, Shunsuke Yoshida, Shinjiro Kawato, Akira Utsumi, and Kenichi Hosaka: SpotScents, ACM SIGGRAPH 2005 Emerging Technologies, DVD-ROM, Los Angeles, U. S. A., July 2005.