Abstract

We report a low complexity, non-iterative method for enhancing the sharpness, brightness, and contrast of the pictorial content that is recorded in a digital hologram, without the need of re-generating the latter from the original object scene. In our proposed method, the hologram is first back-projected to a 2-D virtual diffraction plane (VDP) which is located at close proximity to the original object points. Next the field distribution on the VDP, which shares similar optical properties as the object scene, is enhanced. Subsequently, the processed VDP is expanded into a full hologram. We demonstrate two types of enhancement: a modified histogram equalization to improve the brightness and contrast, and localized high-boost-filtering (LHBF) to increase the sharpness. Experiment results have demonstrated that our proposed method is capable of enhancing a 2048x2048 hologram at a rate of around 100 frames per second. To the best of our knowledge, this is the first time real-time image enhancement is considered in the context of digital holography.

© 2012 OSA

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References

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  1. T.-C. Poon, ed., Digital Holography and Three-dimensional Display: Principles and Applications (Springer, 2006).
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
  6. T. Yamaguchi, G. Okabe, and H. Yoshikawa, “Real-time image plane full-color and full-parallax holographic video display system,” Opt. Eng. 46(12), 125801 (2007).
    [CrossRef]
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2011

2009

2007

T. Yamaguchi, G. Okabe, and H. Yoshikawa, “Real-time image plane full-color and full-parallax holographic video display system,” Opt. Eng. 46(12), 125801 (2007).
[CrossRef]

Cheung, K. W. K.

Kim, E. S.

Kim, J. H.

Kim, S. C.

Kim, T.

Kim, Y. S.

Lam, E. Y.

Okabe, G.

T. Yamaguchi, G. Okabe, and H. Yoshikawa, “Real-time image plane full-color and full-parallax holographic video display system,” Opt. Eng. 46(12), 125801 (2007).
[CrossRef]

Poon, T. C.

Poon, T.-C.

Sakamoto, Y.

Sakata, H.

Tsang, P. W. M.

Yamaguchi, T.

T. Yamaguchi, G. Okabe, and H. Yoshikawa, “Real-time image plane full-color and full-parallax holographic video display system,” Opt. Eng. 46(12), 125801 (2007).
[CrossRef]

Yoshikawa, H.

T. Yamaguchi, G. Okabe, and H. Yoshikawa, “Real-time image plane full-color and full-parallax holographic video display system,” Opt. Eng. 46(12), 125801 (2007).
[CrossRef]

Zhang, X.

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Figures (5)

Fig. 1
Fig. 1

Spatial relation between the 3-D object space, the 2-D VDP, and the hologram

Fig. 2
Fig. 2

(a) A scene image evenly divided into a left and a right sections, positioned at 0.56m and 0.6m from the hologram plane, respectively. (b) Numerical reconstruction of the hologram representing the double depth image in Fig. 2(a) at 0.56m. (c) Numerical reconstruction of the hologram representing the double depth image in Fig. 2(a) at 0.56m. The whole hologram has been directly processed with histogram equalization

Fig. 3
Fig. 3

(a),(b) Numerical reconstruction of the hologram representing the double depth image in Fig. 2(a) at 0.56m and 0.6m, respectively. The hologram has been enhanced with our proposed method.

Fig. 4
Fig. 4

(a) A hemisphere with the texture of an earth image positioned at 0.3m from the hologram plane. The radius of the hemisphere is 0.5mm. (b),(c) Numerical reconstructed image of the hologram representing the image in Fig. 4(a) after direct application of high-boost-filtering to the left side of the hologram, and after application of high-boost-filtering to sharpen the left side of the globe with our proposed method, respectively.

Fig. 5
Fig. 5

(a),(b) Plot of the normalized cross-correlation values between a hologram which is generated directly from an enhanced 3D scene, and a hologram which is enhanced by our proposed method at different positions of the VDP, representing the “Lenna” and the “hemisphere”, respectively.

Equations (10)

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H( x,y )= m=1 X1 n=1 Y1 I( m,n ) r( m,n,x,y ) exp[ j 2π λ r( m,n,x,y ) ] .
u w ( x,y )=H( x,y )g( x,y ),
u w H ( x,y )| ( x,y )R =A[ u w ( x,y )B u w L ( x,y ) ].
u w L ( x,y )= 1 9 m=1 1 n=1 1 u w ( x+m,y+n ) .
p( m )=N( m )/M.
cdf( i )= k=0 i p( k ) .
n=D×cdf( m )
T( 0 )=1 and T( m )| m>0 =n/m.
v( x,y )= u w ( x,y )T( | u w ( x,y ) | )
H ENC ( x,y )= u ENC ( x,y ) g ( x,y ),

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