International Workshop on Holography and related technologies 2011 (IWH2011), Utsunomiya, A1,
pp.1-2 (2011.11.16, Invited).

Computer holography: 3D imaging of virtual and real objects
Kyoji Matsushima1), Hirohito Nishi1), Yasuaki Arima1), and Sumio Nakahara 2)
1)
Department of Electrical and Electronic Engineering, Kansai University
2)
Department of Mechanical Engineering, Kansai University
3-3-35 Yamate-cho, Suita, Osaka 564-8680, Japan

1. Introduction
The technology of computer-generated holograms (CGH) for display purposes is sometimes called the final
3D technology, because reconstructed 3D images give viewers almost all depth cues. However, the techniqueof CGH could not create fine 3D images equal with that by classical holography for a long time. This is dueto the gigantic display resolution required for reconstructing fine 3D images accompanied with a large
viewing-angle. Recently, we presented some brilliant CGHs that are calculated by techniques called thepolygon-based method1) and silhouette method2) and fabricated by laser lithography technology. These
digitally synthetic holograms, referred to as Computer Holograms in this paper, have extremelyhigh-definition and reconstruct spatial 3D images compared favorably with classical holograms3,4). The
reconstructed images thus give viewers a strong sensation of depth that never has been achieved byconventional 3D systems providing only binocular disparity.
Some new techniques introduced into our computer holograms are presented and demonstrated.
2. New techniques
2.1 Embedding the field of real-existing objects5,6)
The wave-fields of real-existing objects are captured by using the technique of phase-shifting digitalholography and embedded in a virtual 3D scene build of 3D mesh objects and 2D images. Since sensor
pitches and sizes of currently available image sensors do not meet the requirements for high-definition
computer holography, synthetic aperture techniques are used to capture the wide area wave-fields with highsampling density. Examples of optical reconstruction of a computer hologram using this technique are shownin Fig.1. Here, photographs are taken from different view-points.
2.2 Rendering specular smooth surfaces7)
Some early computer holograms created by the polygon-based method reconstructed only diffuse surfaces.
Specular surfaces also can be reconstructed by controlling the spatial spectrum of individual polygons5).
However, the shading technique is limited to flat-shading. This new technique makes it possible to create
specular and smooth surfaces without any tessellation technique of polygons, which obviously increases thecomputation time. Figure 2 shows optical reconstruction of a computer hologram by the technique.
2.3 Hidden-surface removal of severe self-occluded objects
Hidden-surface removal is a very difficult and important problem in computer holography, because viewerscan take various view-points of holograms unlike computer graphics (CG) whose view-points are fixed instill images. In our computer holograms, the silhouette method enables us to properly reconstructmutual-occlusion. This means that light of objects hidden behind other objects are shielded properly in any
view-point. However, in some cases where the object itself has occlusion, for example concave objects, thistechnique fails to hide the surfaces should not be seen. To achieve exact hidden-surface removal, the lightshould be shielded polygon by polygon. However, this is very time-consuming because the conventionalsilhouette method requires the same number of numerical operation of field propagation as that of polygons.
The new technique is for avoiding unnecessary field propagation and reducing the computation time. Opticalreconstruction of a computer hologram created by the proposed technique is shown in Fig. 3.
3. Conclusion
Three techniques are newly introduced into high-definition computer holography. These techniques mostInternational Workshop on Holography and related technologies 2011 (IWH2011), Utsunomiya, A1,pp.1-2 (2011.11.16, Invited).

likely enhance power of expression of computer holograms.
This work was supported in part by research grants from the JSPS (KAKENHI, 21500114) and Kansai
University (Grant-in-aid for Joint Research 2011-2012).
Reference
1) K. Matsushima: Appl. Opt. 44, 4607-4614(2005).
2) K. Matsushima, A. Kondoh: SPIE Proc. 5290, 90-97(2004).
3) K. Matsushima, S. Nakahara: Appl. Opt. 48, H54-H63 (2009).
4) K. Matsusima, M. Nakamura, S. Nakahara, I. Kanaya: SIGGRAPH 2010 Poseters, (2010).
5) H. Nishi, K. Higashi, Y. Arima, K. Matsushima, S. Nakahara: SPIE Proc. 7957, 79571A(2011).
6) Y. Arima, K. Matsushima, S. Nakahara: OSA Topical Meeting on Digital Holography andThree-Dimensional Imaging 2011, Tokyo, DWC28(2011).
7) H. Nishi, K. Matsushima, S. Nakahara: OSA Topical Meeting on Digital Holography andThree-Dimensional Imaging 2011, Tokyo, DWC29(2011).

(a) Left(a) Left(b) Center(c) Right(b) Center(c) Right(b) Center(c) Right

Fig.1 Optical reconstruction of “Bear II”.

Fig.1 Optical reconstruction of “The Metal Venus II”.

(a) Left

Fig.1 Optical reconstruction of “The Hands”.