Long Term Stability and Reliability of Permanently Installed On - Line UV Sensors Kyle

UV sensors are typically very sensitive to aging and solarization effects of the harsh environment in which they are used. Minimizing the long term effects of UV on a sensor/optics is extremely challenging, especially with on-line installed sensors used for continuous monitoring on a 24/7 basis. This paper describes a patented method of reducing the effects of aging and solarization to a minimal amount so a user can monitor and control a curing process with a robust, stable and consistent sensor. This paper reviews the impact of radiation (UV, Visible, IR) on the optical components (photodiodes, optical filters) in a sensor and presents the test data showing sensor performance over thousands of hours of operation with little or no deterioration. Construction of Optical Sensors Sensors for the measurement of optical radiation levels typically consist of three elements: • A detector converts optical energy incident on the sensor to electrical energy, typically in the form of an electric current. • An optical filter selects wavelengths of interest from the incident light to be transferred to the detector. • Input Optics can serve both to protect the other elements of the sensor, and to achieve a desired spatial response for the sensor. For example, a diffuse optical element is employed to achieve cosine response in the sensor. Every sensor system, at a minimum, has a detector. Optical filters are omitted in applications where the detector response and the band of interest are the same, or when it is assumed that the level of radiation in the band of interest will be well-correlated with a broader band. Other input optics are omitted in applications where spatial response does not require additional control, the other elements do not require mechanical protection, or where their cost would be prohibitive.