Abstract
A deterministic phase-encoded encryption system is proposed. A lenticular lens array (LLA) sheet with a particular LPI (lenticular per inch) number is chosen as a modulator (key) instead of the random phase molator. The suggested encryption scheme is based on arbitrary two-step phase-shift interferometry (PSI), using an unknown phase step. The encryption and decryption principle is based on an LLA in arbitrary unknown two-step PSI. Right key holograms can be used to theoretically show that the object wavefront is the only one left in the hologram plane and that all accompanying undesired terms are eliminated. The encrypted image can therefore be numerically and successfully decrypted with the right key in the image plane. The number of degrees of freedom of the encryption scheme increases with the distance from the object and the LLA to the CCD, and also with the unknown phase-step and the LLA LPI number. Computer simulations are performed to verify the encryption and decryption principles without a key, with the wrong key and with the right key. Optical experiments are also performed to validate them.
Highlights
In digital holography (DH), the hologram is digitized and the object wavefront is numerically reconstructed using a computer
The suggested encryption scheme is based on arbitrary two-step phase-shift interferometry (PSI), using an unknown phase step
Of the encryption approaches that have been developed in recent years, the most often used and highly successful ones are based on phase-shift interferometry (PSI), making good use of available charged-couple device (CCD) resources to capture on-axis encrypted digital holograms [6,7,8,12,14]
Summary
In digital holography (DH), the hologram is digitized and the object wavefront is numerically reconstructed using a computer This idea was proposed by Goodman and Lawrence [1]. This approach has attracted increasing attention because a charged-couple device (CCD) camera was first used to acquire holograms directly with off-axis and in-line configurations [2,3]. The encrypted hologram includes the dc term, virtual image and twin image, because the object wavefront interferes with the phase-encoded reference wave at the hologram plane. The virtual image is the product of the object wavefront and the conjugate term of the phase-encoded reference wave.
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