= Brian Diffey
{c}
{tag=Physicist}
{tag=Physiology and neuroscience author}
= B. L. Diffey
{c}
{synonym}
\b[Brian Diffey], credited as \b[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>.<The transmission of optical radiation through human nails by S. G. Parker and B. L. Diffey>[Abstract and byline, British Journal of Dermatology 108, 11–16, DOI 10.1111/j.1365-2133.1983.tb04573.x]{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>.<Brian Diffey profile at Newcastle University>[Background, Research Interests and Publications; Dryburn Hospital history and Diffey BL entries]{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,
$$
I_{\rm det}=\int s(\lambda)[P_{\lambda,\rm trans}+P_{\lambda,\rm fl}]\,d\lambda,
$$
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.
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