Transmission out-of-plane interferometer to study thermal distributions in liquids.

Area of Science:

• Optics and Photonics
• Fluid Dynamics
• Thermal Science

Background:

• Traditional optical phase observation methods often require complex in-line alignment or external mirrors.
• Observing dynamic thermal processes in liquids presents challenges in maintaining optical stability and resolution.
• Digital holographic interferometry offers high-resolution phase imaging but can be sensitive to alignment.

Purpose of the Study:

• To introduce a simplified optical setup for observing optical phase in heating liquids.
• To develop an out-of-plane transmission digital holographic interferometer that minimizes alignment complexity.
• To demonstrate the system's capability in visualizing time-dependent thermal distributions.

Main Methods:

• An out-of-plane transmission digital holographic interferometer was designed and implemented.
• A neutral phase screen was used to uniformly add speckle to image holograms.
• Variable magnification was achieved through the illumination geometry of the liquid sample.
• A proof-of-principle experiment involving a heating liquid was conducted.

Main Results:

• The developed optical setup successfully observed the optical phase in a heating liquid without in-line alignment or post-sample mirrors.
• The use of a neutral phase screen effectively introduced speckle for holographic recording.
• Variable magnification allowed for detailed observation of the sample area.
• The experiment clearly depicted the temperature-time-varying distribution within the liquid through optical phase changes.

Conclusions:

• The proposed out-of-plane digital holographic interferometer provides a simplified and effective method for optical phase observation in dynamic thermal processes.
• The system's ability to achieve variable magnification and visualize thermal distributions makes it a valuable tool for fluid dynamics and thermal science research.
• This technique offers a promising alternative for non-invasive, high-resolution phase imaging in challenging liquid environments.