International Workshop on Holography and Related Technologies 2013 (IWH2013), Kitami, 17a-2(2013.10.17).

A wavefront printer using complex-amplitude modulationby using phase-only SLM
Wataru Nishii and Kyoji Matsushima
Department of Electrical and Electronic Engineering, Kansai University,
3-3-35, Yamate-cho, Suita, Osaka 564-8680, Japan

1. Introduction
Computer holography is being developed in recent several years and producing impressive high-definition
computer-generated holograms (CGH). These high-definition CGHs are printed by high resolution printers[1-3] and the reconstructed 3D images are comparable to conventional optical holograms. However, These
CGHs cannot be reconstructed by white light illumination because of its two-dimensional fringe pattern,
while conventional optical holography produces volume holograms reconstructed by white light. This isbecause the fringes are recorded in a three-dimensional manner.
To produce synthetic volume holograms, holographic printers have been proposed [4]. This type ofprinters record multi-viewpoint images by optical interference of light generated by a spatial light modulator(SLM) with a reference wave. Therefore, the produced hologram is volumetric and thus reconstructed bywhite light illumination. However, produced images are holographic stereograms in these printers, because
2D images are recorded on the material. If wavefront, numerically synthesized by computer and generated by
SLM, is recorded on the material instead of 2D images, the produced hologram dose not reconstruct
stereogram but numerically calculated object fields, and thus the hologram is regarded as CGHs. In thisscheme, CGH can be produced as volume hologram that reconstructs 3D images under white lightillumination. We call this type of printer “wavefront printer”.
Wavefront printers reported in early studies commonly use SLMs that modulate amplitude of light [5].
However, wavefront printer by amplitude SLM needs some technique to removes the conjugate image. This
generally results in the narrow space-band product. Therefore, we propose a wavefront printer using
phase-only SLM. However, this type of SLM has the problem of wavefront degradation because of coding
noise caused by phase-only modulation. In this paper, we propose a method for reducing the degradation byusing polarization modulation that is generated even in phase-only SLM.
2. Principle of wavefront printer and complex amplitude modulation
Figure 1 shows the structure of the wavefront printer. Wavefront printer record synthetic wavefronts on
photo-sensitive materials by optical interfere of the wavefronts with a reference wave. Since the reference
wave illuminates the material from the other side
M1of the synthetic wavefronts, volume CGH isLaser Shutter HWP1PBS
SF2 HWP2
488[nm]recorded on the material. Here, the phase-only
M2
M3
SLM modulates not only phase but also
SF1
ND filter
polarization angle of the incident light according
L4L1StageAperture

L3L5
L6

Hologram plate HP Filter

L2Fig.1 The structure of the wavefront printer.

BSSLM

Table 1 Parameter of the phase-only SLM.
Manufacturer
HOLOEYE
Model number
PLUTO
Number of pixels
1,920×1,080
Pixel pitches
8×8µm
Modulation level256(8bit)

International Workshop on Holography and Related Technologies 2013 (IWH2013), Kitami, 17a-2(2013.10.17).

to the pixel level displayed on the SLM. As a result, amplitude of the recorded wavefront effectively changes
dependently on the polarization angle as shown in Fig. 2(a). This allows us to modulate complex amplitudeof light even in the phase-only SLM. Figure 2(b) shows the value of complex amplitude modulation forgiven pixel levels. This was measured in the SLM used for the printer. The parameters of the SLM is shownin Table 1.
3. Print of high-definition volume CGH and its optical reconstruction
Figure 3 and table 2 shows the 3D scene of the printed test CGH and its parameters, respectively. Figure 4
shows optical reconstruction of the test CGHs by white light illumination. Noise caused in the phase-onlymodulation as in (a) is slightly eased by complex amplitude modulation as in (b).
4. Conclusion
The wavefront printer using phase-only SLM is proposed for printing volume CGHs. It is verified thatcomplex amplitude modulation is valid for reduction of coding noise caused by phase-only encoding.
This work was supported by research grants from the JSPS (KAKENHI, 24500113) and the MEXT
strategic research foundation at private universities (2013-2017).
References[1] S. Yamanaka and K. Matsushima: “A new high-resolution printer for digital synthetic holograms” inJapanese, The Institute of Image Information and Television Enginners 58, 1665-1668 (2004).
[2] H. Yoshikawa and M. Tachinami: “Development of direct fringe printer for computer-generatedholograms”, SPIE Proc. 5742, 5742-33 (2005).
[3] K. Matsushima and S. Nakahara: “Extremely High-Definition Full-Parallax Computer-Generated
Hologram Created by the Polygon-Based Method”, Appl. Opt. 48, H54-H63 (2009).
[4] M. Yamaguchi, N. Ohyama, and T. Honda: “Holographic three-dimensional printer: new method”, Appl.
Opt. 31, 217-222 (1992).
[5] T. Yamaguchi, O. Miyamoto and H. Yoshikawa: “Volume hologram printer to record the wavefront ofthree-dimensional objects”, Opt. Eng, 51, 075802 (2012).
yPolarization ofreference wave

Im1.0

Polarization ofgenerated wave

-1.0

x0

1.0

Effective amplitude ofinterference fringe-1.0(a) Principle

Hologram
x

g=255

g=0
θ(g)

yObject(b) Effective complex
amplitude modulation.

Fig. 2 Complex amplitude modulation by the phase-only SLM.

Rez2230Fig. 3

30.24

Unit : mm30.72

The 3D scene of the test CGH.

Table 2 Parameters used for printing volume CGH.
Number of total pixels
Effective pitches
Size of hologram
Number of pixels of a tile
Number of tiles
Wavelength
Center position of the object

30,720×30,240pixel
1.0×1.0µm
30.72×30.24mm2
1,920×1,080pixel
16×28
488nm
(0, 0, －30)mm(b) Complex amplitude
modulation
Fig. 3 Optical reconstruction of the CGHs by white light illumination.
(a)Phase-only modulation