Precise knowledge and control over the amount of light generated, delivered and measured is required for process repeatability. This requires an in-depth understanding of the source of radiometry. Radiometry is the lynch pin that links the simple measurement of a photocurrent from a detector to established metrics of measure - power and irradiance. This knowledge is built into each Lumen Dynamics system through the use of internal or external radiometers. Every system delivers repeatability and radiometric accuracy.
Quantifying and characterizing radiant energy or light can be a challenging task. The measurement technique must address factors such as the spectral content of the incident light and its spatial and angular distribution. UV light can damage many materials, leading to photo-bleaching or solarization - effects that can modify the response of the radiometer. In addition, the process used to calibrate the radiometer generally has multiple steps, with each step influencing the overall uncertainty of the resulting calibration.
The Lumen Dynamics Advantage
Lumen Dynamics manufactures a family of radiometers that offer unmatched versatility and accuracy for UV spot curing and fluorescence microscopy.
- High Accuracy Measurements: Lumen Dynamics radiometers utilize a patented non-imaging optical technology to efficiently gather light over large collection areas and divergence angles. This optical system provides for a uniformity of response across the collection aperture of better than 3% and uniformity in angular response of better than 1% within the divergence angles typically found in UV spot curing delivery optics. In contrast, competitive products tend to have small collection apertures. Therefore, they are prone to irradiance measurement errors larger than 30% simply due to spatial variations in the light distribution out of flexible light guide delivery optics as they are bent.
- Flat Spectral Response: Many of Lumen Dynamics radiometers are designed to measure broadband light sources. The detection system within these systems is based upon thermopile technology to provide a flat spectral response compared to photodiode technologies. This enables the user to more accurately measure sources with varying spectral bandwidths and different spectral power densities. In contrast, competitive radiometers tend to have narrow band filters, making them accurate only when the light being measured is exclusively of that narrow spectral band and can be grossly inaccurate for broadband light sources.
- Increased Versatility: Lumen Dynamics has identified the need in some applications to measure light directly at the cure site or microscope objective plane. A compact measurement device that is coupled with the Lumen Dynamics radiometer has been developed to improve the consistency and repeatability of UV curing and illumination where measurement at the light guide is insufficient to maintain process control.
- Narrow Band Calibration: Lumen Dynamics has recently expanded its calibration capability to include a narrow band calibration process for accurately measure sources such as LEDs and lasers popular in microscopy applications and more recently adopted for UV curing applications. Lumen Dynamics' objective plane radiometer is calibrated in the spectral band from 320 to 700nm in 1 nm increments.
- NIST Traceability: Lumen Dynamics radiometers are calibrated using ISO-9001 certified processes to achieve absolute traceably to radiometric standards maintained by the National Institute of Standards and Technology in the United States. Our uncertainty specification of +/-5% typical, +/-10% maximum is among the best in the industry, and we believe one of the most strictly maintained. Redundancy has been built into the calibration process to ensure reliable, consistent calibrations.