Integrating Spheres for Measurements Between 0.185 microm and 12 microm

Area of Science:

• Optical physics
• Spectroscopy
• Materials science

Background:

• Accurate diffuse transmission and reflection measurements are crucial for material characterization.
• Traditional methods often have limitations in spectral range and calibration accuracy.

Purpose of the Study:

• To develop and describe a new system for absolute total diffuse transmission and reflection measurements.
• To extend the measurable spectral range into the ultraviolet (UV) and infrared (IR).
• To incorporate a unique self-calibrating technique for enhanced accuracy.

Main Methods:

• Utilized two integrating spheres, one coated with BaSO(4) (0.185–2.0 µm) and the other with sulfur flowers (1.5–12 µm).
• Employed a self-calibrating technique based on goniophotometric measurements for diffuse transmission and reflection.
• Ensured sphere coatings (BaSO(4) and sulfur) meet diffuseness and high reflectance requirements.

Main Results:

• The system successfully extends diffuse measurement capabilities into the UV and IR spectral regions.
• Reflection intercalibrations achieved high accuracy, better than 0.3% in the visible range.
• Transmission intercalibrations for quasi-specular samples showed potential absolute differences of several percent, necessitating goniophotometric validation.

Conclusions:

• The described system offers a robust method for absolute total diffuse transmission and reflection measurements.
• The self-calibrating feature enhances measurement reliability, particularly for reflection.
• Goniophotometric transmission measurements are essential for accurate determination with quasi-specular samples.