## Electroholographic display unit for three-dimensional display by use of special-purpose computational chip for holography and reflective LCD panel

Optics Express, Vol. 13, Issue 11, pp. 4196-4201 (2005)

http://dx.doi.org/10.1364/OPEX.13.004196

Acrobat PDF (279 KB)

### Abstract

We developed an electroholography unit, which consists of a special-purpose computational chip for holography and a reflective liquid-crystal display (LCD) panel, for a three-dimensional (3D) display. The special-purpose chip can compute a computer-generated hologram of 800×600 grids in size from a 3D object consisting of approximately 400 points in approximately 0.15 seconds. The pixel pitch and resolution of the LCD panel are 12*µm* and 800×600 grids, respectively. We implemented the special purpose chip and LCD panel on a printed circuit board of approximately 28*cm*×13*cm* in size. After the calculation, the computer-generated hologram produced by the special-purpose chip is displayed on the LCD panel. When we illuminate a reference light to the LCD panel, we can observe a 3D animation of approximately 3*cm*×3*cm*×3*cm* in size. In the present paper, we report the electroholographic display unit together with a simple 3D display system.

© 2005 Optical Society of America

2. K. Maeno, N. Fukaya, O. Nishikawa, K. Sato, and T. Honda, “ELECTRO-HOLOGRAPHIC display using 15MEGA pixels LCD,” Proc.SPIE **2652**, 15–13 (1996). [CrossRef]

*α*and

*j*show a CGH and a 3D object, where

*A*is the intensity of the 3D object, λ is the wavelength of the reference light, and

_{j}*p*is the sampling interval on the CGH and the 3D object. The parameters

*xα*and

*yα*are the horizontal and vertical coordinates of the CGH, respectively, and

*x*and

_{j}, y_{j}*z*are the horizontal, vertical and depth coordinates of the 3D object. The parameters

_{j}*x*and

_{j},y_{j},x_{α}*y*are normalized by the sampling interval

_{α}*p*.

*MN*), where

*M*is the total sampling number of the CGH and

*N*is the total number of points of the 3D object. For example, for the case in which a low-resolution CGH (

*M*=800×600 grids) is computed from a 3D object with a simple structure (

*N*=1,000 points), the computation requires approximately 10 seconds using a personal computer with a 1.8-GHz Pentium-4 processor. Thus, even when using a computer with general computational ability, the CGH cannot be computed at video rate, i.e., 30 CGHs per second. Furthermore, a high-resolution CGH and a 3D object consisting of several points is required in order to develop a practical electroholographic display. Increasing the resolution of a CGH and the number of points of a 3D object requires increased computational ability.

*N*, whereas that for a CGH is proportional to

*MN*. In order to solve this problem, several software approaches have been proposed [3

3. M. Lucente, “Interactive Computation of Holograms Using a Look-Up Table,” J. Electronic Imaging **2**–**1**, pp. 28–34 (1993). [CrossRef]

4. H. Yoshikawa, S. Iwase, and T. Oneda, “Fast Computation of Fresnel Holograms employing Difference,” Proc. SPIE **3956**, pp. 48–55 (2000). [CrossRef]

5. K. Matsushima and M. Takai, “Recurrence formulas for fast creation of synthetic three-dimensional holograms,” Appl. Opt. **39**, pp. 6587–6594 (2000). [CrossRef]

7. T. Ito, T. Yabe, M. Okazaki, and M. Yanagi, “Special-purpose computer HORN-1 for reconstruction of virtual image in three dimensions,” Comput. Phys. Commun. **82**, 104–110 (1994). [CrossRef]

8. T. Ito, H. Eldeib, K. Yoshida, S. Takahashi, T. Yabe, and T. Kunugi, “Special-purpose computer for holography, HORN-2,” Comput. Phys. Commun. **93**, 13–20 (1996). [CrossRef]

9. T. Shimobaba, S. Hishinuma, and T. Ito, “Special-Purpose Computer for Holography HORN-4 with recurrence algorithm,” Comput. Phys. Commun. **148/2**, pp. 160–170 (2002). [CrossRef]

*et al*. used an acoustic optical modulator (AOM) as a spatial light modulator (SLM). An electroholographic display system with an AOM has only horizontal parallax in principle. A reconstructed 3D object from the system is large, because the diffraction angle of an AOM is wide. However, this optical system becomes a complex because it includes mechanism in the system [1]. On the other hand, an electroholographic display system with an LCD as an SLM has also been developed [2

2. K. Maeno, N. Fukaya, O. Nishikawa, K. Sato, and T. Honda, “ELECTRO-HOLOGRAPHIC display using 15MEGA pixels LCD,” Proc.SPIE **2652**, 15–13 (1996). [CrossRef]

10. T. Ito, T. Shimobaba, H. Godo, and M. Horiuchi, “Holographic reconstruction with 10um pixel pitch reflective LCD by reference light of LED,” Opt. Lett. **27**, 16, 1406–1408 (2002). [CrossRef]

12. T. Ito and T. Shimobaba, “One-unit system for electroholography by use of a special-purpose computational chip with a high-resolution liquid-crystal display toward a three-dimensional television,” Opt. Express **12**, No. 9, 1788–1793 (2004), http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-9-1788. [CrossRef] [PubMed]

## 2. Electroholographic Display Unit

*cm*×13

*cm*in size. The USB controller is used for communication, which is the coordinate datum of 3D objects, between a host computer and the electroholographic display unit. The datum is stored in Static RAM chips (SRAM). SPC automatically starts the computation of a CGH after receiving the datum. SPC implemented by virtual multiple pipeline (VMP) architecture [11

11. J. Makino, M. Taiji, T. Ebisuzaki, and D. Sugimoto, “GRAPE-4: A Massively Parallel Special-Purpose Computer for Collisional N-Body Simulations,” ApJ **480**, 432 (1997). [CrossRef]

### 2.1. Special-Purpose Chip for Holography

9. T. Shimobaba, S. Hishinuma, and T. Ito, “Special-Purpose Computer for Holography HORN-4 with recurrence algorithm,” Comput. Phys. Commun. **148/2**, pp. 160–170 (2002). [CrossRef]

_{XY},Γ

_{1}and Δ, which are expressed as

_{n-1},δ

_{n-1}and Δ of the first CU, which computes the following two recurrence formulas and the intensity

*I*(

*x*) on a CGH:

_{α}+n, y_{α}*n*, which is normalized by

*p*, indicates a coordinate on a CGH. The cascade connection of CUs, as shown in Fig. 2, can compute the two recurrence formulas of Eq. (3) and the intensity

*I*(

*x*) of Eq. (4).

_{α}+n, y_{α}12. T. Ito and T. Shimobaba, “One-unit system for electroholography by use of a special-purpose computational chip with a high-resolution liquid-crystal display toward a three-dimensional television,” Opt. Express **12**, No. 9, 1788–1793 (2004), http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-9-1788. [CrossRef] [PubMed]

*I*(

*x*) of Eq. (4) at one clock cycle of 35 MHz.

_{α}+n, y_{α}*vp_sw*signal. In the new unit, the clock frequency for reading 3D object information from the SRAM chips is 40 MHz. In addition, we used a phase-locked loop (PLL) in the FPGA chip to generate a 80-MHz clock signal from the 40-MHz clock signal. The 80-MHz clock signal is supplied to circuits in the BPU and the CUs. During the computation of a CGH, the

*vp-sw*signal is periodically toggled between 1 and 0 at 40 MHz.

*x*and

_{j}, y_{j}*P*are supplied to the BPU from the SRAM chips at 40 MHz. In Fig. 2, coordinates (

_{j}*x*) and (

_{α}, y_{α}*x*) are automatically set on registers in the FPGA chips so that they can be switched quickly. Here,

_{α}+C_{N},y_{α}*C*is the total number of CUs in the FPGA chip. The two coordinates are alternately supplied to the BPU at 80 MHz. Therefore, we can calculate Eq. (2), Eq. (3) and the cosine function in Eq. (4) alternately for the two coordinates at 80 MHz. The IU of the new unit can calculate the intensities

_{N}*I*(

*x*) and

_{α},y_{α}*I*(

*x*) at 40 MHz because the output of the look-up table for the cosine function is selected and accumulated by “Selector” and “ACC” by the

_{α}+C_{N},y_{α}*vp_sw*signal

*C*=30) into SPC.

_{N}### 2.2. Optical system and experimental result

*µm*, an active area of 9.6

*mm*×7.2

*mm*, and a maximum refresh rate of 360 Hz.

## 3. Conclusion

*µm*pixel pitch was approximately 3° for the wavelength of 500~700

*nm*. A well-known method for expanding the viewing zone of an electroholographic display is to enlarge the display area of a CGH. We can easily add multiple units to the optical system because we have implemented the unit on a small printed circuit board. In future studies, we are planning to develop a large-scale real-time electroholographic display system with the 16 units in order to enlarge the viewing zone. The applications of this system will include the visualization of numerical simulations, entertainment, medical imagery, and computer aided design.

## References and links

1. | S.A. Benton, “Experiments in holographic video imaging,” Proc.SPIE |

2. | K. Maeno, N. Fukaya, O. Nishikawa, K. Sato, and T. Honda, “ELECTRO-HOLOGRAPHIC display using 15MEGA pixels LCD,” Proc.SPIE |

3. | M. Lucente, “Interactive Computation of Holograms Using a Look-Up Table,” J. Electronic Imaging |

4. | H. Yoshikawa, S. Iwase, and T. Oneda, “Fast Computation of Fresnel Holograms employing Difference,” Proc. SPIE |

5. | K. Matsushima and M. Takai, “Recurrence formulas for fast creation of synthetic three-dimensional holograms,” Appl. Opt. |

6. | M. Lucente, “Diffraction-Specific Fringe Computation for Electro-Holography,” Ph. D. Thesis Dept. of Electrical Engineering and Computer Science, Massachusetts Institute of Technology (1994). |

7. | T. Ito, T. Yabe, M. Okazaki, and M. Yanagi, “Special-purpose computer HORN-1 for reconstruction of virtual image in three dimensions,” Comput. Phys. Commun. |

8. | T. Ito, H. Eldeib, K. Yoshida, S. Takahashi, T. Yabe, and T. Kunugi, “Special-purpose computer for holography, HORN-2,” Comput. Phys. Commun. |

9. | T. Shimobaba, S. Hishinuma, and T. Ito, “Special-Purpose Computer for Holography HORN-4 with recurrence algorithm,” Comput. Phys. Commun. |

10. | T. Ito, T. Shimobaba, H. Godo, and M. Horiuchi, “Holographic reconstruction with 10um pixel pitch reflective LCD by reference light of LED,” Opt. Lett. |

11. | J. Makino, M. Taiji, T. Ebisuzaki, and D. Sugimoto, “GRAPE-4: A Massively Parallel Special-Purpose Computer for Collisional N-Body Simulations,” ApJ |

12. | T. Ito and T. Shimobaba, “One-unit system for electroholography by use of a special-purpose computational chip with a high-resolution liquid-crystal display toward a three-dimensional television,” Opt. Express |

**OCIS Codes**

(090.1760) Holography : Computer holography

(090.2870) Holography : Holographic display

**ToC Category:**

Research Papers

**History**

Original Manuscript: April 26, 2005

Revised Manuscript: May 19, 2005

Published: May 30, 2005

**Citation**

Tomoyoshi Shimobaba, Atsushi Shiraki, Nobuyuki Masuda, and Tomoyoshi Ito, "Electroholographic display unit for three-dimensional display by use of special-purpose computational chip for holography and reflective LCD panel," Opt. Express **13**, 4196-4201 (2005)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-13-11-4196

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### References

- S.A.Benton, �??Experiments in holographic video imaging,�?? Proc.SPIE Vol.IS# 08, 247-267 (1991).
- K.Maeno, N.Fukaya, O.Nishikawa, K.Sato and T.Honda, �??ELECTRO-HOLOGRAPHIC display using 15MEGA pixels LCD,�?? Proc.SPIE 2652, 15�??13 (1996). [CrossRef]
- M.Lucente, �??Interactive Computation of Holograms Using a Look-Up Table,�?? J. Electronic Imaging 2-1, pp. 28�??34 (1993). [CrossRef]
- H.Yoshikawa, S.Iwase and T.Oneda, �??Fast Computation of Fresnel Holograms employing Difference,�?? Proc. SPIE 3956, pp. 48�??55 (2000). [CrossRef]
- K.Matsushima and M.Takai, �??Recurrence formulas for fast creation of synthetic three-dimensional holograms,�?? Appl. Opt. 39, pp. 6587�??6594 (2000). [CrossRef]
- M.Lucente, �??Diffraction-Specific Fringe Computation for Electro-Holography,�?? Ph. D. Thesis Dept. of Electrical Engineering and Computer Science, Massachusetts Institute of Technology (1994).
- T.Ito, T.Yabe, M.Okazaki and M.Yanagi, �??Special-purpose computer HORN-1 for reconstruction of virtual image in three dimensions,�?? Comput. Phys. Commun. 82, 104�??110 (1994). [CrossRef]
- T.Ito, H.Eldeib, K.Yoshida, S.Takahashi, T.Yabe and T.Kunugi, �??Special-purpose computer for holography, HORN-2,�?? Comput. Phys. Commun. 93, 13�??20 (1996). [CrossRef]
- T.Shimobaba, S.Hishinuma and T.Ito, �??Special-Purpose Computer for Holography HORN-4 with recurrence algorithm,�?? Comput. Phys. Commun. 148/2, pp. 160�??170 (2002). [CrossRef]
- T.Ito, T.Shimobaba, H.Godo and M.Horiuchi, �??Holographic reconstruction with 10um pixel pitch reflective LCD by reference light of LED,�?? Opt. Lett. 27, 16, 1406�??1408 (2002). [CrossRef]
- J.Makino, M.Taiji, T.Ebisuzaki and D.Sugimoto, �??GRAPE-4: A Massively Parallel Special-Purpose Computer for Collisional N-Body Simulations,�?? ApJ 480, 432 (1997). [CrossRef]
- T.Ito and T.Shimobaba, �??One-unit system for electroholography by use of a special-purpose computational chip with a high-resolution liquid-crystal display toward a three-dimensional television,�?? Opt. Express 12, No. 9, 1788�??1793 (2004), <a href="http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-9-1788.">http://www.opticsexpress.org/abstract.cfm?URI=OPEX-12-9-1788.</a> [CrossRef] [PubMed]

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