|Ophthalmic Applications of Circular Polarizers|
A circular polarizer is constructed from a linear polarizer laminated to a retarder. A retarder is an optical element that divides a linearly polarized beam into two orthogonal components without altering the intensity and polarization of the beam. It retards the phase of one component relative to the other and reunites the components into a single emerging beam. If the axis of the retarder is at 45º to the axis of the linearly polarized light, the two orthogonal components will be equal in magnitude. If the retardance (i.e., the relative phase difference between the two components) is 90 º of phase angle, or a quarter wavelength, the resulting beam is circularly polarized. The circularly polarized light can be right-handed or left-handed polarized, depending on the angle between the axis of the retarder and the axis of the linear polarizer. Right circularly polarized light will be blocked by a left circular polarizing filter, and vice versa.
Circular polarizers are being used in an increasing number of applications. These include control of corneal reflex glare in direct ophthalmoscopy, improvement of corneal endothelial view on slit-lamp specular reflection biomicroscopy, and consumer applications such as control of reflections and glare from computer visual display terminals (VDTs), and 3-D TV and movie projection systems. We have also used them in retinal photography, and pointed to possible improvements with their use in ophthalmic applications that traditionally used linear polarizers.
NIH / R01-EYO5450 Computer Processing of Retinal Nerve Fiber Defects.
Fariza E, Jalkh AE, Thomas JV, O'Day T, Peli E, Acosta J. (1988) Use of circularly polarized light in fundus and optic disc photography. Archives of Ophthalmology 106: 1001-1004 [PDF 6.0 MB]
Peli E. (1986) Ophthalmic applications of circular polarizers. Journal of the American Optometric Association. 57(4): 298-302
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Peli E. (1985) Circular polarizers enhance visibility of endothelium in specular reflection biomicroscopy. Archives of Ophthalmology 103: 670-672 [PDF 531 KB]
Peli E. (1983) Control of vertically polarized glare. Journal of the American Optometric Association. 54(5): 447-450 [PDF 6.0MB]