Proceedings of 2nd International Symposium for Color Science and Art 2020-2021

Development of multicolor-holographic flip-books systems
using lithium-niobate crystals (2)Jun Chen, Mitsunori Toyoda, Yukihiro Ishii*,**Tokyo Polytechnic Univ., 1583 Iiyama, Atsugi, Kanagawa 243-0297, Japan* Tokyo Univ. of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, JAPAN** RIKEN Center for Advanced Photonics, Wako 351-0198, JapanABSTRACT
A multicolor holographic flip-books system using a white
LED light source is presented. In this system,
angle-multiplexed image plane holograms are recordedusing an Fe-doped LiNbO3 (LN) crystal as recording
media with a 532-nm green laser. A white LED light source
was then used to illuminate the recorded holograms. The
flip-books animation can be played when the LN crystal
was slowly rotated. The reconstructed flip-books can beobserved directly with human eyes, and the image noise
was drastically reduced due to an incoherent white-lightsource.

Fig. 3 Optical setup hologram recording
A diode-pumped solid-state (DPSS) laser (CoherentCompass 315M-100SL, 532nm, 100mW) is used forrecording the holograms. The light beam from the DPSS
laser is split using a Beam-split into two beams. One isused to illuminate a liquid-crystal device (LCD) on which
the input images were displayed, and the light wave
passing through the LCD was imaged with a 4-f opticalsystem onto the LN crystal as the object wave. The otherbeam is expanded and then used as a reference wave.
The object and reference waves with a cross angle of 30°
overlapped on the LN crystal and form an interference
fringe patterns. In the bright region of the fringe patterns,the electrons of Fe level were excited, moved to dark
region and finally formed a space-charge field that
produces a space refractive index distribution via Pockels
effect. In this way the input image was recorded on the LN
crystal as a transparent image hologram. Because of thesharp Bragg condition, the next image can be recorded byslightly rotating the crystal.

1. INTRODUCTION
We describe a multicolor-holographic flip-books systemusing Fe-doped LiNbO3 (LN) crystals. By using the system,
color animation can be observed by rotating the crystal.
Being different from the conventional hologram recorded
on a thin recording material, volume hologram using athick material allows the angle-multiplexed hologram
recording [1~3]. Thus, volume hologram has proved to bevery useful for optical memory due to the large storage
capacity and fast transfer rate. Thanks to theangle-multiplexing property, it’s interesting to use the LN
crystal as a holographic recording material for recording
multicolor flip-books.
Fourier-transform scheme has been usually used torecord the hologram in LN crystals. However,
Bragg-mismatch occurs when we use a light source with adifferent wavelength for hologram reconstruction, as aresult, only a portion of the recorded image can bereconstructed. On the hand, an image hologram [3] canproduces a whole image. We demonstrate thewhole-image reconstructions from an image-plane volume
hologram with a Fe-doped LN crystal. A LN volume
hologram can record a number of multiplexed images withthe rotation of a crystal [4].
2. THEORY AND OPTICAL SYSTEM
The concept of the proposed multicolor-holographic
flip-books system [5,6] is schematically shown in Fig.1.
The images forming the flip-books are multiply recordedon an LN crystal as holograms while the LN crystal isrotated by an angle of 1°. After that, we can observe acolor animation by rotating the LN crystal under theillumination of a LED broad-spectral source [7].

Fig. 2 Optical setup hologram reconstruction
In multi-color observation of the flip-books, a day lightwhite LED Solis-3C (Thorabs Inc.) was use as a lightsource. Solis-3C covers a large spectrum range from
430nm to 750nm. The DPSS green laser was also usedas light source for comparison. For reconstruction of19

Proceedings of 2nd International Symposium for Color Science and Art 2020-2021
image with different wavelength i.e. different color, theincident angle of the illumination beam should be set as=,and θB sin −1 λB / λG ⋅ sin θGθR sin −1 λR / λG ⋅ sin θG=(()

4.4 Demonstration of flip-books using the LED
As a demonstration, flip-books was made using theLED light source. During the experiments, the original
images was send to LCD one by one, and recorded withthe reference beam, while the LN crystal was rotated by 1°
between two adjacent images.

)

to match the Bragg condition due to the wavelength
difference between the recording and readout lights.
3. EXPERIMENTAL RESULTS
3.1 Hologram reconstruction using the LED light
In our experiments, a Fe-doped LN crystal of 10-mm
square and 4-mm thickness was used. In our previousstudy, we found that the p-polarization is better thans-polarization, therefore the p-polarization was used inhologram recording. An image hologram was recorded byuse of the image shown in Fig.3(a). The angle between
object and reference beams is 30°. The reconstructed
image using the LED light source is shown in Fig.3 (b), andthe reconstructed image using the green laser is also
shown in Fig.3(c).

Fig. 6 Demonstration of a flip-books using the white
LED as an illumination light source.
(a)

4. CONCLUSION
A multicolor holographic flip-boos system is presented.
The original images were recorded on a rewritable
photorefractive media, Fe-doped LN crystal, we canobserve a color animation by slowly rotating the crystal
with a white LED light source. By optimize the incident lightpolarization condition, the exposure-time reduction fromhundreds to seconds enabled us to easily record a large
amount of images into the crystal.

(c)

(b)

Fig. 3 Hologram reconstruction using LED and laser:(a) original image, (b) with LED, (c) using green laser.
3.2 The effect of the polarization
In order to check the effect of the polarization ofillumination beam, reconstructed the hologram by use
different LED light beam of different polarization states,and the experimental results are shown in Fig.4, (a)random, (b) p-polarization, and (c) s-polarization. From
the results, we found s-polarized light does not makecontribution and can be cut out using a polarizer.

6. Acknowledgment
This work was supported by “FY2021 Tokyo
Polytechnic University International Research Center for
Color Science and Art Grant”
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[4] T. Sato, J. Chen, and Y. Ishii, Proc. of The Eleventh
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[5] T. Hosono, S. Hikota, J. Chen, M. Toyoda, Y. Ishii, The
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[6] F. Shishido, Y. Okeya, J. Chen, M. Toyoda, Y. Ishii,Optics & Photonics Japan 2019, 3pP12 (2019).
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(a)

(b)
(c)
Fig. 4 Reconstruction image intensity at different
polarization condition

3.3 Red image reconstructed using the LED light
Since we used a white LED light source for reconstruction,
the images of different color can be reconstructed from therecorded hologram as shown in Fig.5. As an example, bysetting the incident angle as17.94°, a red image
corresponding to a central wavelength of 632.8nm wasobtained.

(a)

(b)

Fig. 5 Reconstruction of a red image with the LED: (a)original image, (b) reconstructed image.

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