A deterministic phase-encoded encryption system, which adopts a lenticular lens array (LLA) sheet as a phase modulator
(key), based on arbitrary two-step phase-shift interferometry (PSI), with an unknown phase step, is presented. The
principle of encryption and decryption which is using a LLA in arbitrary unknown two-step PSI is given. With the aid of
key holograms (right key), it can be theoretically shown that only the reconstructed object wavefront term will be left in
the image plane, and all the accompany undesired terms be eliminated. Thus the hidden information of object wavefront
in this encryption system can be numerically and successfully decrypted using arbitrary unknown two-step PSI with right
key. For comparisons, computer simulations are carried out to verify the principle of encryption and decryption without
key, with wrong key and with right key, respectively.
This work presents the working principle for digital holography with arbitrary phase-step reconstruction using multiple
holograms. The arbitrary phase-step of the reference wave can be easily estimated with two different approaches -blind
searching algorithm (Meng et al.) and the limited area algorithm (Hsieh et al.). Using these approximations, the
magnitude-contrast images are reconstructed without dc term and twin-image blurring, but the phase-contrast images are
filled with phase distortion. Computer simulations are carried out to verify the proposed approach and optical
experiments are performed to validate it. The optical results and spatial resolutions using different estimation of the
phase-step are presented and discussed herein.
We propose a novel optical encryption approach using a lenticular lens array (LLA) as a deterministic phase
modulator and the single-shot digital holographic scheme. In the proposed scheme, the input amplitude image is
encrypted and interferes with the reference wave phase, which is modulated by a LLA, then recorded holographically by
a digital CCD camera to form an encrypted hologram. A decryption key is obtained from the key hologram using
numerical reconstruction. The image is decrypted using a digital holographic approach after which the encrypted
hologram is multiplying the numerical reconstructed key for decryption. The experimental results show that only an
encrypted hologram is needed. Moreover with this approach, the decryption procedure can be rapidly accomplished
using a personal computer, presenting a decrypted image of satisfactory image quality. Finally the selective sensitivity of
the key rotation is also investigated.
In this work, a novel approach for numerical wave-front reconstruction in arbitrary phase step digital holography is
presented. We present a simple and effective approach for digital holography microscopy that can be used for the 3D
reconstruction of micro-structure images. The experimental results demonstrate that only two digital holograms and a
simple estimation are required for the twin-image suppression and numerical reconstruction. The advantages of this
approach are its simplicity, in that only one estimate equation need be applied, and its effectiveness, in that the exact
phase profile of a micro lens array is presented, without blurring due to numerical reconstruction or aberration caused by
the quadratic phase micro objective lens.
We develop a novel holographic reconstruction method that requires only an off-axis Fresnel digital hologram
without the need for additional phase-retrieval elements in the experimental setup. With this approach we can reconstruct
numerical phase profiles without twin-image blurring, using only an off-axis digital hologram. Furthermore numerical
reconstruction and twin-image suppression can be rapidly accomplished with a personal computer. Not only is twin-
image suppression easier but the constraints characteristic of the conventional phase-shifting digital holographic-based
scheme that employs multiple exposures can be overcome. The experimental results clearly show that complex spatial
frequency information about the object to be measured is not lost during numerical reconstruction and that the profile of
the phase object can be exactly measured and presented.
This work presents a novel method for optical decrypted key production by screen printing technology. The key is
mainly used to decrypt encoded information hidden inside documents containing Moire patterns and integral
photographic 3D auto-stereoscopic images as a second-line security file. The proposed method can also be applied as an
anti-counterfeiting measure in artistic screening. Decryption is performed by matching the correct angle between the
decoding key and the document with a text or a simple geometric pattern. This study presents the theoretical analysis and
experimental results of the decoded key production by the best parameter combination of Moire pattern size and screen
printing elements. Experimental results reveal that the proposed method can be applied in anti-counterfeit document
design for the fast and low-cost production of decryption key.