Standardization of Broadband UV Measurements for 365 nm LED Sources

Area of Science:

• Optical Radiation Measurement
• Photometry and Radiometry
• Ultraviolet (UV) Metrology

Background:

• Broadband UV-A irradiance measurements are critical for various applications.
• Current UV-A measurement practices using 365 nm sources face challenges with spectral mismatch errors.
• The spectral power distribution of 365 nm UV sources is not standardized, leading to inconsistent readings.

Purpose of the Study:

• To evaluate broadband UV measurements from 365 nm UV sources.
• To identify the causes of spectral mismatch errors in UV-A irradiance meters.
• To recommend standardization for accurate UV measurements.

Main Methods:

• Evaluation of available UV detectors and meters for spectral responsivity.
• Calculation of the spectral product of source distribution and meter responsivity.
• Estimation of broadband signal-measurement errors for different meter-source combinations.

Main Results:

• The CIE standardized UV-A function results in large spectral mismatch errors with 365 nm sources.
• Significant variations in readings occur between different UV meters measuring the same UV source.
• Calculated errors highlight the impact of non-standardized spectral characteristics.

Conclusions:

• Standardization of both UV source spectral distribution and meter spectral responsivity is essential for uniform, low-uncertainty broadband measurements.
• Specific spectral responsivity functions are identified as necessary for accurate broadband 365 nm UV irradiance meters.
• Recommendations are provided for improving the accuracy of UV irradiance meters.