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G. Li; A New Method for Characterization of Transverse Chromic Aberration of Ophthalmic Lens. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3944.
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Transverse chromatic aberration causes lateral smearing or blurring of the images on retina due to color dependent magnification, and it is an important performance parameter for ophthalmic lens. The transverse chromatic aberration is usually characterized by the prism diopters and the Abbe number of the lens material, which involves the refractive indices at wavelengths 589.3 nm, 486.1 nm and 656.3 nm, and the latter two wavelengths are away from the photopic peak. Here a new parameter, called effective Abbe number is introduced and used to characterize the transverse chromatic aberration.
The measurement is performed at 543 nm and 594 nm, which are close to the photopic peak and available with commercial tunable He-Ne laser. A computer-interfaced optical setup has been built for this test. It requires only the laser beam displacements due to the angular deviation imparted by the lens. Other parameters such as the lens power, the distance of the measurement location from the center of the lens, and the distance from the lens to the camera are not required.
Composite lenses with -2D, -4D, -6D powers made with two singlets and a photosensitive layer in between to increase the effective Abbe value at radii away from the optical center have been tested. The effective Abbe value measured in the periphery of the lens was increased from a nominal base plastic value of 42.0 to a value of 46.0. The increase in visual acuity due to increases in effective Abbe value can be accurately estimated based upon measured vision data in the published literature.
The effective Abbe number gives a much better indication of visual performance than the actual Abbe number. Using this method, experimental results for the electro-optic ophthalmic lens will be reported.
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