Apochromat

About: Apochromat is a research topic. Over the lifetime, 642 publications have been published within this topic receiving 7934 citations.

Hybrid refractive/diffractive achromatic camera lens and camera using such

Abstract: A hybrid refractive and diffractive achromatic lens suited for single-use or inexpensive single-lens cameras operating in visible spectral range. The lens comprises a body of optically transmissive material having an index of refraction at a wavelength approximately at the center of said range of at least 1.45. The lens body having a first and second surface on opposite sides thereof, at least one of said surfaces being curved to provide a refractive portion having power and introduces chromatic aberration, the lens having a diffractive portion having power which substantially achromatizes the lens for the chromatic aberration of the refraction portion over about 440 nm to about 650 nm range.

Selection of optical glasses. 1: Two materials

Abstract: A new method of selecting glass combinations for the correction of paraxial chromatic aberration in optical systems has been developed. This new method corrects axial color for at least three wavelengths using two different types of glass, and certain combinations may be found which are corrected at four and five wavelengths. The Abbe number and relative partial dispersions are not utilized in this new approach; instead the Buchdahl chromatic coordinate is used in characterizing the dispersion of the glasses. While the method is of general validity, in this first paper the number of different materials is restricted to two. Thick air-spaced doublets and Mangin mirror designs are presented as examples which demonstrate color correction at three, four, and five wavelengths and which are corrected for spherical aberration and spherochromatism as well. Tables are included listing glass combinations that have favorable power distributions and color correction at three, four, and five wavelengths.

Influence of shape and gradient refractive index in the accommodative changes of spherical aberration in nonhuman primate crystalline lenses.

Abstract: PURPOSE. To estimate changes in surface shape and gradient refractive index (GRIN) profile in primate lenses as a function of accommodation. To quantify the contribution of surface shape and GRIN to spherical aberration changes with accommodation. METHODS. Crystalline lenses from 15 cynomolgus monkeys were studied in vitro under different levels of accommodation produced by a stretching system. Lens shape was obtained from optical coherence tomography (OCT) cross-sectional images. The GRIN was reconstructed with a search algorithm using the optical path measured from OCT images and the measured back focal length. The spherical aberration of the lens was estimated as a function of accommodation using the reconstructed GRIN and a homogeneous refractive index. RESULTS. The lens anterior and posterior radii of curvature decreased with increasing lens power. Both surfaces exhibited negative asphericities in the unaccommodated state. The anterior surface conic constant shifted toward less negative values with accommodation, while the value of the posterior remained constant. GRIN parameters remained constant with accommodation. The lens spherical aberration with GRIN distribution was negative and higher in magnitude than that with a homogeneous equivalent refractive index (by 29% and 53% in the unaccommodated and fully accommodated states, respectively). Spherical aberration with the equivalent refractive index shifted with accommodation toward negative values (� 0.070 lm/diopter [D]), but the reconstructed GRIN shifted it farther (� 0.124 lm/ D). CONCLUSIONS. When compared with the lens with the homogeneous equivalent refractive index, the reconstructed GRIN lens has more negative spherical aberration and a larger shift toward more negative values with accommodation.

Geometrical aberration of a generalized Wolter type I telescope.

Abstract: Using two hyperboloids, we can control spherical aberration and coma of an imaging x-ray telescope. The coma-free condition is satisfied only at a particular radius of the first mirror. The best performance is obtained when we allow the coma-free condition at the outer edge and cancel about half of the defocused image for the largest height of an object by introducing spherical aberration.