Smartphone image sensors and solar radiation

This is a brief outline of a paper a colleague and I completed recently.

Evaluation of a Smartphone Sensor to Broadband and Narrowband Ultraviolet A Radiation (Igoe and Parisi, 2015).

This paper brings together previous research published about using narrowband filters and the possibility of using broadband UV filters on a smartphone camera for measuring direct solar UVA irradiances.

Earlier research focused on the successful use of UV narrowband filters (+ strong neutral density filters) to determine the aerosol optical depth at 340 nm and 380 nm, in Evaluating UVA Aerosol Optical Depth using a Smartphone Camera. (Igoe et al. 2013), and later, an Android app was developed and successfully tested for it in Smartphone based Android app for determining UVA aerosol optical depth and direct solar irradiances.

As smartphone cameras are not explicitly Scientific instruments, and in the case for solar UVA broadband measurements, are not calibrated as traditional equipment are, it is not possible to directly determine the direct solar broadband UVA irradiance.  However, in research published in Broadband Direct UVA Irradiance Measurement for Clear Skies Evaluated using a Smartphone (Igoe and Parisi, 2014), it was found that the broadband UVA could be reconstructed from narrowband data.  This was achieved using an adapted version of algorithms and models used in An algorithm to evaluate solar irradiance and effective dose rates using spectral UV irradiance at four selected wavelengths (Anav et al. 2004).