Optical encryption for large-sized images using random phase-free method

TL;DR

This paper introduces an optical encryption method for large images that reduces speckle noise by using a random phase-free approach and scaled diffraction, enabling secure encryption and decryption of images larger than the encrypted image size.

Contribution

The paper presents a novel optical encryption framework combining random phase-free method and scaled diffraction to encrypt large images with reduced speckle noise.

Findings

Effective encryption and decryption of large images beyond encrypted image size.

Significant reduction in speckle noise in decrypted images.

Successful application of scaled diffraction for different plane sizes.

Abstract

We propose an optical encryption framework that can encrypt and decrypt large-sized images beyond the size of the encrypted image using our two methods: random phase-free method and scaled diffraction. In order to record the entire image information on the encrypted image, the large-sized images require the random phase to widely diffuse the object light over the encrypted image; however, the random phase gives rise to the speckle noise on the decrypted images, and it may be difficult to recognize the decrypted images. In order to reduce the speckle noise, we apply our random phase-free method to the framework. In addition, we employ scaled diffraction that calculates light propagation between planes with different sizes by changing the sampling rates.