Effects of spatial coherence in diffraction phase microscopy.

Area of Science:

• Optics and Photonics
• Biomedical Imaging
• Surface Metrology

Background:

• Quantitative phase imaging (QPI) offers label-free imaging but can be limited by noise or artifacts.
• Laser-based systems may have lower noise but white light systems can suffer from object-dependent artifacts like halos, hindering accurate surface topography reconstruction.

Purpose of the Study:

• To demonstrate accurate height map generation using white light diffraction phase microscopy (WLDPM) even for challenging structures.
• To identify and mitigate object-dependent artifacts, specifically halos, in WLDPM.
• To explore methods for reducing exposure times in WLDPM for dynamic measurements.

Main Methods:

• Implementing proper spatial filtering at the condenser for spatial coherence and at the output Fourier plane for a uniform reference beam in WLDPM.
• Analyzing object-dependent artifacts as a high-pass filtering phenomenon.
• Utilizing a supercontinuum laser as a high-radiance source.

Main Results:

• Accurate height maps of challenging structures were achieved by applying spatial filtering guidelines.
• The halo artifact was successfully eliminated through the application of these design guidelines.
• Reduced exposure times were achieved using a supercontinuum laser, enabling fast dynamic measurements.

Conclusions:

• Spatial filtering is crucial for artifact reduction and accurate surface topography reconstruction in WLDPM.
• WLDPM, when properly configured, can overcome limitations of traditional white light and laser-based systems.
• Supercontinuum lasers offer a viable solution for high-speed quantitative phase imaging applications.