Noiseless optical encryption based on a complex secret key and a joint Fresnel transform correlator with a Billet...

A noiseless optical cryptosystem based on a joint Fresnel transform correlator (JFTC) with a Billet split lens (BSL) was designed. Benefitting from the adjustable structure of the BSL, we can control the size and recording position of the joint Fresnel transform power distribution by changing the split width of the BSL. To avoid the text being affected by noise, we converted the text into quick response (QR) code in advance, then used the QR code as the plaintext and utilized the noise tolerance ability of the QR code to realize noiseless recovery of the text. In this cryptosystem, we designed a complex secret key (CSK) to replace the secret key made from a random phase mask, and the CSK consists of a QR code filter and a spiral phase mask. Because the QR code and spiral phase can be determined by a few simple data, the transmission and preservation of the CSK is convenient. Finally, the validity and feasibility of the cryptosystem were demonstrated, and the sensitivity of the CSK was researched by simulation and experiment.