Lensless optical encryption with speckle-noise suppression and QR codes

Area of Science:

• Optics and Photonics
• Information Security
• Digital Image Processing

Background:

• Contemporary optical encryption methods often use coherent light, leading to speckle noise that degrades performance.
• Existing spatially incoherent encryption techniques face challenges with reduced encryption strength due to undiffracted light.
• Information encoded in formats like QR codes is susceptible to these limitations.

Purpose of the Study:

• To develop a novel lensless optical encryption scheme that mitigates speckle noise and enhances encryption strength.
• To address the limitations of existing coherent and incoherent optical encryption methods.
• To demonstrate a secure and robust method for encrypting and decrypting information, such as QR codes.

Main Methods:

• A new lensless encryption scheme was designed and experimentally implemented.
• Two liquid crystal spatial light modulators (SLMs) were utilized for encoding and encryption.
• A specially designed encoding diffraction optical element (DOE) was employed with spherically diverging illumination, eliminating the need for a converging lens.

Main Results:

• The proposed scheme successfully encrypted QR codes using spatially incoherent light.
• Experimental results demonstrated successful information retrieval from the decrypted images.
• Analysis confirmed high key sensitivity and a large key space, indicating resistance to brute-force attacks.

Conclusions:

• The developed lensless optical encryption scheme effectively overcomes the drawbacks of traditional methods.
• The technique offers a robust solution for secure optical encryption, particularly for data like QR codes.
• The demonstrated security parameters suggest suitability for practical applications requiring high-level data protection.