Reducing field depth: annular Hadamard masks

Area of Science:

• Optics and Photonics
• Image Processing

Background:

• Optical systems often face challenges with limited depth of field, affecting image clarity.
• Modulation Transfer Function (MTF) is a key metric for evaluating optical system performance.

Purpose of the Study:

• To investigate the use of Hadamard-coded annular masks for optically narrowing the field depth.
• To enhance the influence of focus error on MTF without compromising light throughput.

Main Methods:

• Utilizing annular masks coded with Hadamard matrix elements.
• Performing numerical evaluations of irradiance point spread functions (PSFs) and MTFs.
• Assessing Fisher information of Walsh-Hadamard masks.

Main Results:

• Demonstrated that Hadamard-coded annular masks can narrow field depth.
• Showed enhanced influence of focus error on MTF with no loss in light throughput.
• Presented numerical evaluations and digitally generated images validating the approach.

Conclusions:

• Hadamard-coded annular masks offer an effective method for optical depth-of-field control.
• The technique allows for translating out-of-focus information into background noise, enabling 3-D scene slicing.
• This approach provides a novel way to improve optical imaging and depth perception.