Optical encryption system that uses phase conjugation in a photorefractive crystal

Gopinathan, Unnikrishnan; Joseph, Joby; Singh, Kehar

doi:10.1364/ao.37.008181

Cited by 165 publications

(79 citation statements)

References 12 publications

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“…In the image encryption process, an image with a random phase mask is jointly Fourier transformed with another random pattern, which is a key for encryption and decryption, as shown in Fig. 2 and a hologram is formed at the Fourier plane (Yang & Kim, 1996, Javidi et al, 1996, and Unnikrishnan et al, 1998. The phase random mask put in front of the image to be embedded plays a role for scrambling the image, however it little affects the reconstruction of hologram, since the reconstruction is only the intensity of them.…”

Section: Theory Of Image Encryption and Decryption Of Hologrammentioning

confidence: 99%

Optimization of Hologram for Security Applications

Ohtsubo¹

2011

Holograms - Recording Materials and Applications

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Section: Theory Of Image Encryption and Decryption Of Hologrammentioning

confidence: 99%

Optimization of Hologram for Security Applications

Ohtsubo¹

2011

Holograms - Recording Materials and Applications

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“…Many techniques for the optical encryption of image data have been proposed and implemented in recent years [51][52][53][54][55][56][57][58][59][60][61][62]. Most perform encryption with a random phase mask positioned in the input, Fresnel, or Fraunhofer domain, or a combination of domains.…”

Section: Optical Image Encryptionmentioning

confidence: 99%

Phase in Optical Image Processing

Naughton¹,

Rastogi²,

Hack³

2010

AIP Conference Proceedings

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Abstract. The use of phase has a long standing history in optical image processing, with early milestones being in the field of pattern recognition, such as VanderLugt's practical construction technique for matched filters, and (implicitly) Goodman's joint Fourier transform correlator. In recent years, the flexibility afforded by phase-only spatial light modulators and digital holography, for example, has enabled many processing techniques based on the explicit encoding and decoding of phase. One application area concerns efficient numerical computations. Pushing phase measurement to its physical limits, designs employing the physical properties of phase have ranged from the sensible to the wonderful, in some cases making computationally easy problems easier to solve and in other cases addressing mathematics' most challenging computationally hard problems. Another application area is optical image encryption, in which, typically, a phase mask modulates the fractional Fourier transformed coefficients of a perturbed input image, and the phase of the inverse transform is then sensed as the encrypted image. The inherent linearity that makes the system so elegant mitigates against its use as an effective encryption technique, but we show how a combination of optical and digital techniques can restore confidence in that security. We conclude with the concept of digital hologram image processing, and applications of same that are uniquely suited to optical implementation, where the processing, recognition, or encryption step operates on full field information, such as that emanating from a coherently illuminated real-world three-dimensional object.

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“…One such application of digital holography is optical encryption [9][10][11][12][13][14][15][16][17][18][19][20] which often produces a complex-valued encrypted image resulting from a random phase mask positioned in the input, Fresnel, or Fraunhofer domain, or combination of domains. Digital holography has been applied to the encryption of 2D conventional (real-valued) images.…”

Section: Digital Holographymentioning

confidence: 99%

<title>Capture, encryption, compression, and display of digital holograms of three-dimensional objects</title>

et al. 2006

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Digital holography can be used to capture the whole Fresnel field from a reflective or transmissive object. Applications include imaging and display of three-dimensional (3D) objects, and encryption and pattern recognition of two-dimensional (2D) and 3D objects. Often, these optical systems employ discrete spatial light modulators (SLMs) such as liquid-crystal displays. In the 2D case, SLMs can encode the inputs and keys during encryption and decryption. For 3D processing, the SLM can be used as part of an optical reconstruction technique for 3D objects, and can also represent the key during encryption and decryption. However, discrete SLMs can represent only discrete levels of data necessitating a quantisation of continuous valued analog information. To date, many such optical systems have been proposed in the literature, yet there has been relatively little experimental evaluation of the practical performance of discrete SLMs in these systems. In this paper, we characterise conventional phase-modulating liquid-crystal devices and examine their limitations (in terms of phase quantisation, alignment tolerances, and nonlinear response) for the encryption of 2D and 3D data. Finally, we highlight the practical importance of a highly controlled discretisation (optimal quantisation) for compression of digital holograms.

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Optical encryption system that uses phase conjugation in a photorefractive crystal

Cited by 165 publications

References 12 publications

Optimization of Hologram for Security Applications

Optimization of Hologram for Security Applications

Phase in Optical Image Processing

<title>Capture, encryption, compression, and display of digital holograms of three-dimensional objects</title>

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