Showing papers on "Apochromat published in 2006"

Chromatic aberration correction of the human eye for retinal imaging in the near infrared

Abstract: An achromatizing lens has been designed for the human eye in the near infrared range, from 700 to 900 nm, for retinal imaging purposes. Analysis of the performance of the lens, including tolerance to misalignments, has been mathematically accomplished by using an existing eye model. The calculations have shown a virtually perfect correction of the ocular longitudinal chromatic aberration, while still keeping a high optical quality. Ocular aberrations in five subjects have been measured with and without the achromatizing lens by using a Hartmann-Shack wavefront sensor and a broad bandwidth femtosecond Ti:sapphire laser in the spectral range of interest with a set of interference filters, studying the benefits and limits in the use of the achromatizing lens. Ocular longitudinal chromatic aberration has been experimentally demonstrated to be fully corrected by the proposed lens, with no induction of any other parasitic aberration. The practical implementation of the achromatizing lens for Ophthalmoscopy, specifically for optical coherence tomography where the use of polychromatic light sources in the near infrared portion of the spectrum is mandatory, has been considered. The potential benefits of using this lens in combination with adaptive optics to achieve a full aberration correction of the human eye for retinal imaging have also been discussed.

Dynamic compensation of chromatic aberration in a programmable diffractive lens

Abstract: A proposal to dynamically compensate chromatic aberration of a programmable phase Fresnel lens displayed on a liquid crystal device and working under broadband illumination is presented. It is based on time multiplexing a set of lenses, designed with a common focal length for different wavelengths, and a tunable spectral filter that makes each sublens work almost monochromatically. Both the tunable filter and the sublens displayed by the spatial light modulator are synchronized. The whole set of sublenses are displayed within the integration time of the sensor. As a result the central order focalization has a unique location at the focal plane and it is common for all selected wavelengths. Transversal chromatic aberration of the polychromatic point spread function is reduced by properly adjusting the pupil size of each sublens. Longitudinal chromatic aberration is compensated by making depth of focus curves coincident for the selected wavelengths. Experimental results are in very good agreement with theory.

Chromatic compensation of programmable Fresnel lenses

Abstract: Two proposals to compensate chromatic aberration of a programmable phase Fresnel lens displayed on a liquid crystal device and working under polychromatic illumination are presented. They are based on multiplexing a set of lenses, designed with a common focal length for different wavelengths, and a multicolor filter that makes each sublens work almost monochromatically. One proposal uses spatial multiplexing with mosaic aperture. The other uses a rotating scheme, a color filter against an array of lens sectors, and hybrid spatial-time integration. The central order focalization has a unique location at the focal plane. We have drastically reduced the transversal chromatic aberration of the polychromatic point spread function by properly adjusting the pupil size of each sublens. Depth of focus curves have been made coincident too for the selected wavelengths.

Diffractive-refractive hybrid corrector for achro- and apochromatic corrections of optical systems.

Abstract: The possibility is shown of achro- and apochromatic correction of an optical system with any residual chromatism by completing the system with a diffractive-refractive hybrid corrector comprising one diffractive lens and one or two refractive lenses.

Immersion objective lens system for microscope

Abstract: An apochromat immersion objective lens system for microscope which consists, in order from the object side, of a first lens unit composed of a cemented lens component consisting of a plano-convex lens element having a planar surface on the object side and a meniscus lens element having a concave surface on the object side, a second lens unit composed of a lens component or two lens components, a third lens unit comprising at least two cemented lens components, a fourth lens unit composed of a negative lens component having a strongly concave surface on the image side and a fifth lens unit comprising a meniscus lens component having a concave surface on the object side, and has a large numerical aperture exceeding 1.4 without using special oil or a special cover glass plate as well as favorably corrected spherical aberration and chromatic aberration.

Apochromatic telescope without anomalous dispersion glasses.

Abstract: In order to correct secondary longitudinal chromatic aberration in conventional refracting optical systems, it is necessary to use at least one optical material having anomalous partial dispersion. A novel lens system with correction of the secondary spectrum by using only normal glasses is presented. The lens system comprises three widely separated lens components; both second and third components are subaperture. The presented example of an apochromatic telescope demonstrates secondary spectrum correction with the use of only crown BK7 and flint F2, which are among the most inexpensive optical glasses available at the market. Two more similar designs are presented, both with the use of low-cost slightly anomalous dispersion glasses. These telescopes have a higher relative aperture and a smaller tertiary spectrum.

Contact lens with high-order compensation for non-axisymmetric structure

Abstract: Contact lenses, such as prism ballasted toric lenses, having anterior and posterior surfaces related by way of non-axisymmetric thickness variation can exhibit a third-order aberration, particularly vertical coma. A wavefront modifier, such as an aspheric surface modification, is incorporated into the lenses to at least partially compensate for the wavefront aberration associated with the non-axisymmetric thickness variation. A magnitude of the modifications can be adjusted to set a target value for any remaining wavefront aberration of the lenses based on a population-wide goal.

Apochromatically corrected microscope objective

Abstract: A microscope objective with high aperture, large object field and apochromatic correction in the wavelength range from ultraviolet to infrared. The microscope objective includes, starting from the object level: a first group of lenses with overall positive refraction power, including a cemented group with positive-negative refraction power effect, made out of one of two lenses, and of a further lens with positive refraction power, a second group of lenses with positive refraction power, including three cemented lenses, a third group of lenses with negative refraction power, including three cemented lenses, in which the side that faces the image plane is convex, a fourth group of lenses, consisting of a lens with positive refraction power and a cemented group of two lenses with positive-negative refraction power, and a fifth group of lenses, including two lenses in a cemented group with negative-positive refraction power.

Double gauss lens design : A review of some classics

Abstract: Walter Mandler (1922-2005) designed many double Gauss lenses for Leica cameras. We review; form and aberration balance for his most renowned lenses. Designs are re-evaluated using modern optimisation routines with special attention to glass replacement.

Low-order aberration corrections of multilayer flat lenses using negative-index materials

Abstract: A study of the corrections for some low-order aberrations of multilayer flat lenses based on the introduction of negative-index materials is presented. With the aberration coefficients of a multilayer flat lens that we provided, numerical solutions for the parameters of the double-layer three-layer, and four-layer flat lenses are investigated, respectively, to correct the aberrations, under some conditions, up to orders as high as possible. We find that with the increment of the layer number, the spherical and oblique aberrations can be corrected up to higher orders though the corresponding ranges of the refractive indices and working distances become narrower.

The primary structure design of a birefringent lens with the concept of pseudo-chromatic aberration

Abstract: Much attention has been paid to the optical design of a birefringent lens and analysis of its polarization aberration due to its essential application in bifocal interferometric microscopes. To investigate a practical way of designing a birefringent lens with large separation between the two foci, a novel concept named 'pseudo-chromatic aberration' is proposed, which results from the difference of refractive indices between the ordinary and extraordinary rays when they pass through the birefringent lens. As the concept is similar to normal chromatic aberration, the existing primary aberration theory to design a thin cemented lens can also be adopted on the design of a birefringent lens. A table of primary structure of cemented doublet birefringent lenses is consequently obtained. Different combinations of three kinds of birefringent crystals and optical glasses can satisfy various requirements. A concrete example of a birefringent lens with the compactness factor ? of 0.25 is given using the glass of SF2 and calcite.

Iris imaging lens

Abstract: An iris imaging lens (1A) includes a biconvex lens (2A), a biconcave lens (3A), and a visible light cut-off filter (4A). At least one of the surfaces of the visible light cut-off filter (4A) is a curved surface. With this configuration, the visible light cut-off filter (4A) serves as a lens. Not only the biconvex lens (2A) and the biconcave lens (3A) but also the visible light cut-off filter (4A) correct the aberration. Accordingly, it is possible to reduce the aberration and improve the lens performance without increasing the number of imaging lenses. This reduces the production cost.

Aberration functions for microlithographic lens

Abstract: We proposed a series of orthogonal aberration functions, which is suitable for a microlithographic projection lens. In this paper, general explanation and numbering of the orthogonal aberration functions are reviewed.

Zoom lens for imaging element

Abstract: PROBLEM TO BE SOLVED: To provide a compact zoom lens capable of forming an image of high image quality while having a satisfactorily long back focus wherein a color dispersion prism can be installed. SOLUTION: Chromatic aberration of magnification arising in a 1st lens group G1 and a 2nd lens group G2 is corrected by making the transverse chromatic aberration in a direction where the image height of g-line becomes higher than that of d-line in a 4th lens group G4 without enlarging a distance between a 3rd lens group G3 and the 4th lens group G4. Next, axial chromatic aberration in a direction opposite to that of the 4th lens group G4 is generated by using a high-dispersion glass satisfying a conditional expression (2) in the 3rd lens group G3, then, the axial chromatic aberration of the 4th lens group is corrected. Further, the 1st lens group is constituted by using a lens using a special low-dispersion glass material or an abnormal-dispersion glass material satisfying a conditional expression (1), then, the axial chromatic aberration arising in the 1st lens group at a telephoto end is reduced to a certain extent. the expression (1) is 75.0≤ν1 and the expression (2) is 40.0≥ν31. COPYRIGHT: (C)2007,JPO&INPIT

Chromatic aberration compensating image optics

Abstract: An imaging optics capable of compensating for chromatic aberration is provided with a light shielding means in a surface peripheral area of a certain lens element in a lens system so as to block a light flux of a specified wavelength range, thereby eliminating chromatic aberration in halo of the light flux of the specified wavelength range when it passes the periphery of the lens system. Thus, the invention provides the imaging optics that, without an increase in the number of pieces of lens elements and without a use of an expensive specified low-dispersion glass material, in contrast with the prior art imaging optics of the same optical performances, well compensates for chromatic aberration, especially, in halo.

A Camera Lens of Low Light Near Infrared with Large Field of View

Abstract: The partial dispersion of glass working on the near infrared band was caculated,and the apochromatic of a long focal length system was analyzed.A low light near infrared video camera lens was designed,whose focal length is 180mm,F-number is 1.2.Two kinds of glasses,ZF and ZK,was used in this optical system.As a video camera lens,It can be used outdoor environment.

Optical head with spherical aberration correction and method of using same

Abstract: An optical head with excellent optical characteristics even when using a light source that substantially has a wavelength broadening is provided. The optical head includes a light source, an objective lens for focusing a light beam emitted from the light source on an information recording medium and a photodetector for detecting the light beam reflected from the information recording medium, wherein defocusing correction means and spherical aberration correction means are provided in an optical path between the light source and the information recording medium. Since both the defocusing correction means and the spherical aberration correction means are provided, while defocusing of a focused spot on the information recording medium caused by a wavelength broadening of the light source and chromatic aberration of the optical system can be corrected, the spherical aberration of the optical system caused by wavelength difference between a design wavelength and an incident wavelength also can be corrected. As a result, excellent optical characteristics can be obtained.