UV Radiometer Optical Stack for Accurate Irradiance
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Solution Overview
Problem
Current UV radiometry instruments struggle to provide accurate and absolute measurements of UV energy and irradiance, especially with UV LED sources, due to non-linear optical responses and lack of consideration for angle of incidence, leading to inconsistent and misleading results.
Innovation Solution
The development of UV radiometers with optical stacks that include a protective window, diffuser, bandpass interference filter, and AOI control plates, which utilize an inverse response filter to achieve a linear optical response and control angle of incidence, enabling precise measurement of pre-selected UV wavelengths and rejection of other wavelengths, thereby providing accurate and reproducible absolute energy and irradiance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If commercially available radiometers use filter response only to describe optical response, then device complexity is reduced, but measurement precision deteriorates due to lack of total optical response characterization
Solution Approach 1:
The optical system is segmented into multiple components (protective window, diffuser, bandpass interference filter, photodetector) with each component's individual optical response being characterized and combined to produce the total optical response curve, resolving the contradiction between simplified device description and accurate measurement
Solution Approach 2:
An inverse response filter is introduced as an intermediary component that compensates for the non-linear optical responses of other components in the system, creating a linearized total optical response that enables accurate absolute measurements without requiring complex calibration procedures
2Measurement precision
If bandpass interference filters are used for wavelength selection, then measurement precision for specific UV wavelengths is improved, but device complexity increases due to angle of incidence control requirements
Solution Approach 1:
The angle of incidence control function is extracted and isolated into separate AOI control plates positioned at specific locations in the optical path, allowing the bandpass interference filter to be optimized for wavelength selection while the control plates handle the angular constraints independently
Solution Approach 2:
The mechanical alignment requirements for angle of incidence control are replaced with a simpler optical solution using AOI control plates that define acceptable angular ranges without requiring complex mechanical adjustment mechanisms
3Adaptability or versatility
If non-LED UV sources are measured with traditional radiometers, then historical measurement capability is maintained, but measurement precision deteriorates due to non-constant optical component performance across different wavelength distributions
Solution Approach 1:
The radiometer is designed with a universal optical response characterization that works across different UV source types (LED, mercury lamp, etc.) by measuring the total optical response of all components and using this comprehensive data to accurately measure various UV wavelength distributions, eliminating the need for source-specific calibration
4Device complexity
If relative measurement mode is used to avoid absolute measurement uncertainties, then device complexity is reduced, but loss of information increases due to inability to provide accurate absolute energy and irradiance values
Solution Approach 1:
The inverse response filter acts as an intermediary that linearizes the optical response, enabling absolute measurements to be made directly without requiring complex calibration procedures or sacrificing accuracy for simplicity, thus eliminating the trade-off between device complexity and information completeness
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These instruments offer accurate, rectangular measurement responses with excellent out-of-band rejection, allowing for reliable comparison of different UV sources and improved process control in industrial settings, enhancing the transition from traditional mercury lamp sources to LED sources.
Implementation Method 1
bandpass interference filter arranged to receive light transmitted through the diffuser and configured to pass pre-selected UV wavelengths and reject other wavelengths
Implementation Method 2
photodetector arranged to receive light transmitted through the bandpass filter
Data Source
AI summary
Instruments and methods are disclosed which measure absolute energy and irradiance of UV light sources. The response curves of exemplary optical stacks of the radiometry instruments are substantially rectangular with steep transitions at the cutoff frequencies. Angle of incidence (AOI) control in combination with one or more interference filters in the optical stack enable the full optical stack to produce repeatable and accurate measurements. Inverse response filters are disclosed for leveling optical stack response.