By Marcello Cherchi, MD PhD
From: https://en.wikipedia.org/wiki/Augustin-Jean_Fresnel (accessed 5/31/22)
Augustin-Jean Fresnel was born in Broglie (France) on May 10 of 1788, and died in Ville-D’Avray (France) on July 14 of 1827. He trained as a civil engineer and physicist, and contributed to the study of optics.
Parallel (collimated) beams of light can be focused by refraction via a traditional convex lens (Figure A), but such a lens is relatively heavy. Augustin-Jean Fresnel was able to achieve the same end in a much more compact form by developing a lens consisting of concentric rings (an idea originally proposed by Georges-Louis Leclerc de Buffon) that are the “effective” component of the convex lens (Figure B) that refract the parallel beams of light in the same fashion (Figure C). Figure D shows an actual Fresnel lens, bisected to display its pattern.
The application in oculomotor studies is that a patient wearing Fresnel lenses cannot focus (and thus cannot visually fixate), while an outside examiner can still see the patient’s eyes. Such lenses can be made very compact (Strupp, Fischer et al. 2014).
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All figures from https://jarphys.wordpress.com/2015/04/19/fresnel-lenses-how-they-work/ (accessed 5/30/22).
References
Strupp, M., C. Fischer, L. Hanss and O. Bayer (2014). “The takeaway Frenzel goggles: a Fresnel-based device.” Neurology 83(14): 1241-1245.
