My Research

My research interests include ‘uninstrumented’ 3D display technologies such as volumetric displays and holography. Especially, I am interested in combining applied physics (e.g. wave-front control of sound and light) with end-user engineering (e.g. high-performance computing and hardware design) to create novel 3D interfaces. My concept of 3D displays include not only displaying 3D visual images but also audio and haptics content. My goal is to develop a display system that can provide realistic multimodal user experiences, without the need to wear headsets as well as other devices (e.g. headphones, controllers, data-gloves).

My PhD mainly focused on a design method of unique 3D structures containing multiple 2D images, inspired by the Pulitzer Prize-winning book ‘Gödel, Escher, Bach: an Eternal Golden Braid’. The designed structures can display different images when viewed from different directions and thus can be used as a directional display. I also worked on developments of new types of volumetric displays and high-performance computing for real-time holographic displays.

More recently, I have been working on using phased arrays of ultrasound transducers. The ultrasound waves that I am using are simply mechanical energy that move through the air while making the air particles vibrate. By controlling this mechanical energy in 3D space, we can create content what we see, hear and touch. I am aiming to create a novel 3D interface, which is like 3D holograms portrayed in popular science-fiction movies, by making use of such ultrasound’s unique ability of directly controlling matter in real world.

Research Projects
DataLev: Mid-air data physicalisation using acoustic levitation
Lei Gao, Pourang Irani, Sriram Subramanian, Gowdham Prabhakar, Diego Martinez Plasencia and Ryuji Hirayama, CHI 2023, 312, Hamburg, Germany (2023).
OpenMPD: A low-level presentation engine for multimodal particle-based displays
Roberto Montano-Murillo, Ryuji Hirayama and Diego Martinez Plasencia, ACM Transactions on Graphics 42, 24 (2023).
High-speed acoustic holography with arbitrary scattering objects
Ryuji Hirayama, Giorgos Christopoulos, Diego Martinez Plasencia and Sriram Subramanian, Science Advances 8, eabn7614 (2022).
GS-PAT: High-speed multi-point sound-fields for phased arrays of transducers
Diego Martinez Plasencia, Ryuji Hirayama, Roberto Montano-Murillo and Sriram Subramanian, ACM Transactions on Graphics 39, 138 (ACM SIGGRAPH 2020).
A volumetric display for visual, tactile and audio presentation using acoustic trapping
Ryuji Hirayama, Diego Martinez Plasencia, Nobuyuki Masuda and Sriram Subramanian, Nature 575, 320–323 (2019).
Projection of multiple directional images on a volume structure with refractive surfaces
Ryuji Hirayama, Hirotaka Nakayama, Atsushi Shiraki, Takashi Kakue, Tomoyoshi Shimobaba and Tomoyoshi Ito, Optics Express 27(20), 27637–27648 (2019).
High-performance parallel computing for next-generation holographic imaging
Takashige Sugie, Takanori Akamatsu, Takashi Nishitsuji, Ryuji Hirayama, Nobuyuki Masuda, Hirotaka Nakayama, Yasuyuki Ichihashi, Atsushi Shiraki, Minoru Oikawa, Naoki Takada, Yutaka Endo, Takashi Kakue, Tomoyoshi Shimobaba and Tomoyoshi Ito, Nature Electronics 1, 254–259 (2018).
Efficient method for fabricating a directional volumetric display using strings displaying multiple images
Atsushi Shiraki, Masataka Ikeda, Hirotaka Nakayama, Ryuji Hirayama, Takashi Kakue, Tomoyoshi Shimobaba and Tomoyoshi Ito, Applied Optics 57(1), A33–A38 (2018).
Operating scheme of a light-emitting diode array for a volumetric display exhibiting multiple full-color dynamic images
Ryuji Hirayama, Atsushi Shiraki, Hirotaka Nakayama, Takashi Kakue, Tomoyoshi Shimobaba and Tomoyoshi Ito, Optical Engineering 56(7), 073108 (2017).
Inkjet printing-based volumetric display projecting multiple full-colour 2D patterns
Ryuji Hirayama, Tomotaka Suzuki, Tomoyoshi Shimobaba, Atsushi Shiraki, Makoto Naruse, Hirotaka Nakayama, Takashi Kakue and Tomoyoshi Ito, Scientific Reports 7, 46511 (2017).
Optical addressing of multi-colour photochromic material mixture for volumetric display
Ryuji Hirayama, Atsushi Shiraki, Makoto Naruse, Shinichiro Nakamura, Hirotaka Nakayama, Takashi Kakue, Tomoyoshi Shimobaba and Tomoyoshi Ito, Scientific Reports 6, 31543 (2016).
Image quality improvement for a 3D structure exhibiting multiple 2D patterns and its implementation
Ryuji Hirayama, Hirotaka Nakayama, Atsushi Shiraki, Takashi Kakue, Tomoyoshi Shimobaba and Tomoyoshi Ito, Optics Express 24(7), 7319–7327 (2016).
Design, implementation and characterization of a quantum-dot-based volumetric display
Ryuji Hirayama, Makoto Naruse, Hirotaka Nakayama, Naoya Tate, Atsushi Shiraki, Takashi Kakue, Tomoyoshi Shimobaba, Motoichi Ohtsu and Tomoyoshi Ito, Scientific Reports 5, 8472 (2015).
Three-dimensional volume containing multiple two-dimensional information patterns
Hirotaka Nakayama, Atsushi Shiraki, Ryuji Hirayama, Nobuyuki Masuda, Tomoyoshi Shimobaba and Tomoyoshi Ito, Scientific Reports 3, 1931 (2013).