Simple and flexible method for measuring the liquid refractive index with an electrically tunable lens

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Traditional methods for measuring liquid refractive index (RI) often require mechanical adjustments.
• Axial displacement of light is a key factor in parallel-plate-based RI measurements.

Purpose of the Study:

• To propose a simple, flexible, and mechanically adjusted-free method for measuring liquid RI.
• To utilize an electrically tunable lens (ETL) to replace the conventional convex lens in RI measurement systems.

Main Methods:

• Replaced the convex lens with an ETL in a parallel-plate setup.
• Controlled the driving current of the ETL to maintain a constant camera focal position.
• Derived the theoretical equivalence between ETL focal length change and axial displacement.
• Performed Zemax simulations to analyze ETL imaging characteristics.

Main Results:

• The ETL method allows RI measurement by monitoring focal length changes induced by driving current variations.
• Zemax simulations validated the effectiveness and imaging properties of the ETL.
• Experimental results confirmed the validity of the proposed method for various liquids.

Conclusions:

• The proposed ETL-based method offers a mechanically stable and efficient approach for liquid RI determination.
• This technique avoids cumbersome mechanical camera movements, simplifying the measurement process.
• The method is experimentally validated and suitable for diverse liquid samples.