Vignetting-free computer-generated Fresnel holograms by mask shifting

Area of Science:

• Computational optics
• Digital holography
• Image processing

Background:

• Direct sampling (DS) and simple shading (SS) are common methods for generating sampled Fresnel zone plates (FZPs) in computer-generated holography.
• These methods often lead to aliasing or vignetting in reconstructed images, limiting hologram generation parameters.

Purpose of the Study:

• To propose and evaluate a novel mask-shifting (MS) method for generating sampled FZPs.
• To overcome the limitations of aliasing and vignetting in computer-generated Fresnel holography.

Main Methods:

• The mask-shifting (MS) method involves shifting the center of the FZP relative to the mask center when the FZP is near the hologram margin.
• This shifting introduces a phase shift without altering intensity distribution, thereby alleviating aliasing and vignetting.

Main Results:

• The MS method successfully alleviates both aliasing and vignetting simultaneously.
• This allows for unrestricted object size and object distance during hologram generation.

Conclusions:

• The mask-shifting method offers a significant improvement over traditional DS and SS techniques.
• It provides greater freedom in designing computer-generated holograms without compromising image quality.