## Real-time digital holographic microscopy using the graphic processing unit

Optics Express, Vol. 16, Issue 16, pp. 11776-11781 (2008)

http://dx.doi.org/10.1364/OE.16.011776

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### Abstract

Digital holographic microscopy (DHM) is a well-known powerful method allowing both the amplitude and phase of a specimen to be simultaneously observed. In order to obtain a reconstructed image from a hologram, numerous calculations for the Fresnel diffraction are required. The Fresnel diffraction can be accelerated by the FFT (Fast Fourier Transform) algorithm. However, real-time reconstruction from a hologram is difficult even if we use a recent central processing unit (CPU) to calculate the Fresnel diffraction by the FFT algorithm. In this paper, we describe a real-time DHM system using a graphic processing unit (GPU) with many stream processors, which allows use as a highly parallel processor. The computational speed of the Fresnel diffraction using the GPU is faster than that of recent CPUs. The real-time DHM system can obtain reconstructed images from holograms whose size is 512×512 grids in 24 frames per second.

© 2008 Optical Society of America

## 1. Introduction

1. U. Schnars and W. Juptner, “Direct recording of holograms by a CCD target and numerical Reconstruction,” Appl.Opt. **33**, 2, 179–181 (1994). [CrossRef] [PubMed]

4. N. Masuda, T. Ito, K. Kayama, H. Kono, S. Satake, T. Kunugi, and K. Sato, “Special purpose computer for digital holographic particle tracking velocimetry,” Opt. Express **14**, 603–608 (2006). [CrossRef] [PubMed]

5. Y. Abe, N. Masuda, H. Wakabayashi, Y. Kazo, T. Ito, S. Satake, T. Kunugi, and K. Sato, “Special purpose computer system for flow visualization using holography technology,” Opt. Express, **16**, 7686–7692 (2008). [CrossRef]

6. N. Masuda, T. Ito, T. Tanaka, A. Shiraki, and T. Sugie, “Computer generated holography using a graphics processing unit,” Opt. Express, **14**, 587–592 (2008). [CrossRef]

7. L. Ahrenberg, P. Benzie, M. Magnor, and J. Watson, “Computer generated holography using parallel commodity graphics hardware,” Opt. Express, **14**, 7636–7641 (2006). [CrossRef]

## 2. Real-time digital holographic microscopy system

### 2.1. Outline of the real-time DHM system

*nm*. ”BS” and ”ND” indicate a beam splitter and a neutral density filter, ”M” and ”MO” indicate a mirror and an objective lens. We used a CCD camera, which has a resolution of 1360×1024 and a pixel pitch of 4.65

*μm*× 4.65

*μm*. We also used a test target, USAF 1951, as a sample. These holograms are then transferred to a personal computer (PC) via the USB2.0 interface. The PC controls the GPU and the CCD camera. The GPU, ”GeForce 8800 GTS,” made by NVIDIA, can calculate the Fresnel diffraction at high speed, thus allowing us to obtain reconstructed images from holograms at about 24 frames per second.

### 2.2. Rapid calculation of the Fresnel Diffraction using the GPU

*x*,

*y*) and (ξ,

*η*) are coordinates on reconstruction plane

*u*(

*x*,

*y*) and hologram

*a*(

*ξ*,

*η*) captured by the CCD, respectively,

*λ*is the wavelength of the reference light, and

*z*is the distance from the hologram to the reconstruction plane. Using the convolution theorem, the Fresnel diffraction is expressed as [2,3]:

*C*and

*h*(

*x*,

*y*) define

*F*[∙] and

*F*

^{-1}[∙] indicate the forward and inverse Fourier transform, respectively. If we calculate the Fresnel diffraction using a computer or a GPU, we must discretize Eqs.(1) and (2), and, subsequently use the FFT algorithm.

*operates*/

*SP*× 96S

*Ps*× 1.2

*GHz*= 2304

*Gflops*(floating-point number operations per second). Thus, we can use the GPU chip as a highly parallel processor. We also used the CUDA (Compute Unified Device Architecture) as a programming environment for the GPU chip[8]. In comparison with CG (C for Graphics) language and HLSL (High Level Shader Language), the advantage of the CUDA is to be able to write a source code by a C-like language

*F*[

*a*(

*x*,

*y*)] in Eq. (2) using CUFFT and the result is stored in the memory on the board. Similarly, the GPU chip calculates term

*F*[

*h*(

*x*,

*y*)] and the result is stored in the memory. Thirdly, the GPU chip calculates complex multiplication of

*F*[

*a*(

*x*,

*y*)] and

*F*[

*h*(

*x*,

*y*)], and the result is stored in the memory. Fourthly, the GPU chip calculates

*u*(

*x*,

*y*) =

*F*

^{-1}[

*F*[

*a*(

*x*,

*y*)]

*F*[

*h*(

*x*,

*y*)]] using the inverse FFT, and the result is stored in the memory. Finally, the GPU chip calculates |

*u*(

*x*,

*y*)|

^{2}, and the host computer receives |

*u*(

*x*,

*y*)|

^{2}. On the PC, we process the normalization of |

*u*(

*x*,

*y*)|

^{2}and translate |

*u*(

*x*,

*y*)|

^{2}to an 8-bpp (bits per pixel) image. Here, we can ignore the term

*C*in Eq.(2) because |

*C*|

^{2}is 1 after the calculation of |

*u*(

*x*,

*y*)|

^{2}. For the above process, we used our numerical calculation library for wave optics using the GPU, the GWO (GPU-based Wave Optics) library[10

10. T. Shimobaba, T. Ito, N. Masuda, Y. Abe, Y. Ichihashi, H. Nakayama, N. Takada, A. Shiraki, and T. Sugie, “Numerical calculation library for diffraction integrals using the graphic processing unit: the GPU-based wave optics library,” J. Opt. A: Pure Appl. Opt. **10**, 075308 (2008), http://www.iop.org/EJ/abstract/1464-4258/10/7/075308/. [CrossRef]

11. The GWO library, http://sourceforge.net/projects/thegwolibrary/.

### 2.3. Multiple threading for the real-time DHM system

12. Wikipedia, http://en.wikipedia.org/wiki/Thread_(computer_science).

## 3. Performance and optical results

13. FFTW Home Page, http://www.fftw.org/.

## 4. Conclusion and future work

## Acknowledgment

## References and links

1. | U. Schnars and W. Juptner, “Direct recording of holograms by a CCD target and numerical Reconstruction,” Appl.Opt. |

2. | U. Schnars and W. Jueptner, |

3. | O. K. Ersoy, Diffraction, |

4. | N. Masuda, T. Ito, K. Kayama, H. Kono, S. Satake, T. Kunugi, and K. Sato, “Special purpose computer for digital holographic particle tracking velocimetry,” Opt. Express |

5. | Y. Abe, N. Masuda, H. Wakabayashi, Y. Kazo, T. Ito, S. Satake, T. Kunugi, and K. Sato, “Special purpose computer system for flow visualization using holography technology,” Opt. Express, |

6. | N. Masuda, T. Ito, T. Tanaka, A. Shiraki, and T. Sugie, “Computer generated holography using a graphics processing unit,” Opt. Express, |

7. | L. Ahrenberg, P. Benzie, M. Magnor, and J. Watson, “Computer generated holography using parallel commodity graphics hardware,” Opt. Express, |

8. | NVIDIA, “NVIDIA CUDA Compute Unified Device Architecture Programming Guide Version 1.1,” NVIDIA (2007). |

9. | NVIDIA, “CUDA FFT Library Version 1.1 Reference Documenta-tion,” NVIDIA (2007). |

10. | T. Shimobaba, T. Ito, N. Masuda, Y. Abe, Y. Ichihashi, H. Nakayama, N. Takada, A. Shiraki, and T. Sugie, “Numerical calculation library for diffraction integrals using the graphic processing unit: the GPU-based wave optics library,” J. Opt. A: Pure Appl. Opt. |

11. | The GWO library, http://sourceforge.net/projects/thegwolibrary/. |

12. | Wikipedia, http://en.wikipedia.org/wiki/Thread_(computer_science). |

13. | FFTW Home Page, http://www.fftw.org/. |

**OCIS Codes**

(090.1995) Holography : Digital holography

(090.5694) Holography : Real-time holography

**ToC Category:**

Holography

**History**

Original Manuscript: June 6, 2008

Revised Manuscript: July 15, 2008

Manuscript Accepted: July 21, 2008

Published: July 23, 2008

**Virtual Issues**

Vol. 3, Iss. 9 *Virtual Journal for Biomedical Optics*

**Citation**

Tomoyoshi Shimobaba, Yoshikuni Sato, Junya Miura, Mai Takenouchi, and Tomoyoshi Ito, "Real-time digital holographic microscopy using the graphic processing unit," Opt. Express **16**, 11776-11781 (2008)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-16-11776

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### References

- U. Schnars and W. Juptner, "Direct recording of holograms by a CCD target and numerical Reconstruction," Appl. Opt. 33, 179-181 (1994). [CrossRef] [PubMed]
- U. Schnars and W. Jueptner, Digital Holography - Digital Hologram Recording, Numerical Reconstruction, and Related Techniques (Springer 2005).
- O. K. Ersoy, Diffraction, Fourier Optics And Imaging (Wiley-Interscience 2006).
- N. Masuda, T. Ito, K. Kayama, H. Kono, S. Satake, T. Kunugi, and K. Sato, "Special purpose computer for digital holographic particle tracking velocimetry," Opt. Express 14, 603-608 (2006). [CrossRef] [PubMed]
- Y. Abe, N. Masuda, H. Wakabayashi, Y. Kazo, T. Ito, S. Satake, T. Kunugi, and K. Sato, "Special purpose computer system for flow visualization using holography technology," Opt. Express, 16, 7686-7692 (2008). [CrossRef]
- N. Masuda, T. Ito, T. Tanaka, A. Shiraki, and T. Sugie, "Computer generated holography using a graphics processing unit," Opt. Express 14, 587-592 (2008). [CrossRef]
- L. Ahrenberg, P. Benzie, M. Magnor, and J. Watson, "Computer generated holography using parallel commodity graphics hardware," Opt. Express 14, 7636-7641 (2006). [CrossRef]
- NVIDIA, "NVIDIA CUDA Compute Unified Device Architecture Programming Guide Version 1.1," NVIDIA (2007).
- NVIDIA, "CUDA FFT Library Version 1.1 Reference Documenta-tion," NVIDIA (2007).
- T. Shimobaba, T. Ito, N. Masuda, Y. Abe, Y. Ichihashi, H. Nakayama, N. Takada, A. Shiraki, and T. Sugie, "Numerical calculation library for diffraction integrals using the graphic processing unit: the GPU-based wave optics library," J. Opt. A: Pure Appl. Opt. 10, 075308 (2008), http://www.iop.org/EJ/abstract/1464-4258/10/7/075308/. [CrossRef]
- The GWO library, http://sourceforge.net/projects/thegwolibrary/.
- Wikipedia, http://en.wikipedia.org/wiki/Thread (computer science).
- FFTW Home Page, http://www.fftw.org/.

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