Brian Diffey

Brian Diffey, credited as B. L. Diffey in the primary byline, coauthored the 1983 study of optical transmission through human toenails with S. G. Parker. The paper measured thirteen autopsy toenails at fifteen wavelengths between 300 and 600 nm using a monochromator, integrating sphere and photodiode; its analysis included a correction for nail fluorescence.^[ref]

Newcastle University's named profile identifies Brian Diffey as a photobiology researcher, lists work under the initials B. L. Diffey and records his medical-physics work at Dryburn Hospital, the affiliation given for the nail paper. His research interests include measuring human exposure to ultraviolet radiation.^[ref] The research attribution here is collective; a joint byline does not establish which author performed a particular apparatus task.

The nail experiment illustrates fluorescence contamination in nail-transmission measurements. A light detector can register both incident-wavelength light transmitted through a sample and light emitted at other wavelengths. In an original linear detector model,where $s$ is spectral responsivity and $P_{\lambda }$ is spectral radiant power. Converting the total detector current into transmittance requires separating those contributions or specifying a valid correction. The detector's response at the emitted wavelengths need not equal its response at the illumination wavelength.

For an illustrative already power-calibrated signal, suppose incident power is 1.00 mW and the collected signal contains 0.08 mW of transmitted illumination plus 0.02 mW of fluorescence. Treating all detected power as transmitted illumination gives 10% instead of 8%, a 25% relative overestimate. These are invented values explaining the measurement issue, not data reported by the authors. Their explicit fluorescence correction shows why a detector reading alone does not define the desired optical quantity.