Showing papers on "Apochromat published in 2013"
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TL;DR: The reconstructed GRIN lens has more negative spherical aberration and a larger shift toward more negative values with accommodation, compared with the lens with the homogeneous equivalent refractive index.
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.
41 citations
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TL;DR: This study is the first systematic experimental study of the relative contribution of geometry and GRIN to the aberrations in a mammal lens.
36 citations
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TL;DR: Two novel schemes for correction of spherical aberration are proposed and studied and the accuracy of the proposed aberration correction schemes is validated.
Abstract: As with a conventional lens, a Fresnel zone lens (FZL) can be used to image objects at infinity or nearby In the latter case, the FZL converts a diverging spherical wavefront into a converging spherical wavefront The glass substrate on which the FZL is fabricated introduces spherical aberration resulting in a shift of the image plane and blurring of the image Two novel schemes for correction of this spherical aberration are proposed and studied in this paper To demonstrate them, FZLs are designed with and without aberration correction They are fabricated using electron beam direct writing The devices are evaluated and the accuracy of the proposed aberration correction schemes is validated
18 citations
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TL;DR: Equations for the calculation of optical power and curvature radii are described for aplanatic and nonaplanatic optical systems, which are composed of two or three thin lenses in contact.
Abstract: This work deals with a method for primary optical design of superachromats, where chromatic aberration is corrected for several wavelengths. Equations for the calculation of optical power and curvature radii are described for aplanatic and nonaplanatic optical systems, which are composed of two or three thin lenses in contact. Results of the calculations are presented for chosen optical systems of superachromats with basic design parameters.
15 citations
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11 Sep 2013
TL;DR: In this article, a compact apochromatic lens with long focal length, which operates over very-broad spectrum from 400nm to 900nm for high resolution image application, was designed.
Abstract: This paper designs a compact apochromatic lens with long focal length, which operates over very-broad spectrum from 400nm to 900nm for high resolution image application. The focal length is 290mm, and F-number is 4.5.In order to match CCD sensor, lens resolution must be higher than 100lp/mm. It is a significant challenge to correct secondary spectrum over very-broad spectrum for this application. The paper firstly pays much attention on dispersion characteristic of optical materials over this very-broad spectrum, and dispersion characteristic of glasses is analyzed. After properly glasses combinations and optimal lens structure selected, this compact apochromatic lens is designed. The lens described in this paper comprises fewer lenses, most of them are ordinary optical materials, and only one special flint type TF3 with anomalous dispersion properties is used for secondary spectrum correction. Finally, the paper shows MTF and aberration curve for performance evaluation. It can be seen that MTF of the designed lens nearly reach diffraction limit at Nyquist frequency 100lp/mm, and residual secondary spectrum is greatly reduced to less than 0.03mm (in the lines 550nm and 787.5nm). The overall length of this compact apochromatic lens is just 0.76 times its focal length, and because of fewer lenses and ordinary optical materials widely used, production cost is also greatly reduced.
4 citations
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23 Mar 2013
TL;DR: In this paper, an objective lens for probe-forming particle-optical columns such as focused ion beam equipment, scanning electron microscopes, and helium microscopes is described, which comprises two interleaved (quadrupole/octopole) lenses and two or three ancillary octopole lenses, and is capable of simultaneous compensation of spherical (Cs) and chromatic (Cc) aberrations of the objective lens alone or of the complete particleoptical column.
Abstract: An objective lens for use in probe-forming particle-optical columns such as focused ion beam equipment, scanning electron microscopes, and helium microscopes is described. It comprises two interleaved (quadrupole/octopole) lenses and two or three ancillary octopole lenses, and is capable of simultaneous compensation of spherical (Cs) and chromatic (Cc) aberrations of the objective lens alone or of the complete particle-optical column. Additional apparatus comprising a gridded aperture and position-sensitive detector is specified, together with a method to measure and minimize all of the five independent third-order aberration coefficients of the objective lens.
4 citations
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TL;DR: In this article, the authors proposed a depth measurement system based on the chromatic aberration effect under a dark field illumination scheme. But, the proposed system is limited to a range of ±15 μm and it cannot discriminate the depth change of 2 μm micro-beads.
Abstract: Detecting the z-position of moving objects in an embedded microchannel is an important but highly challenging problem in the MEMS field. The present study proposes a new depth measurement system based on the chromatic aberration effect under a dark-field illumination scheme. The microchannel is illuminated by dispersed white light and the light scattered from the moving objects is captured by a low numerical aperture (N.A.) objective lens. Due to chromatic aberration effect, sample in various positions will scatter different wavelengths. The depth of each moving object is then determined by inspecting the intensity ratio of the scattered spectral components with wavelengths of 450 nm (blue light) and 670 nm (red light), respectively. Experimental results show that the proposed system enables the object depth to be measured over a range of ±15 μm while using acrylic lens for light aberration. Alternatively, the developed system is capable to discriminate the depth change of 2 μm micro-beads when a higher Abbe number material of BK7 lens is used for light aberration. The depth measurements are obtained without the need for a delicate optical system or scanning process with the developed system. The use of UV-Vis-NIR spectrometer enables this system to analyze the depths of the samples in flow velocity 500 μm/sec. The proposed system provides a straightforward yet highly effective means of determining the depth of moving objects in microfluidic channels in a continuous manner.
4 citations
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07 Feb 2013TL;DR: The apochromatic immersion lens is made of multiple lenses having sub-systems as discussed by the authors, which are cropped out from an object plane (OE) by using a meniscus deflected towards the object plane.
Abstract: The apochromatic immersion lens is made of multiple lenses having sub-systems. Five sub-systems (T1,T2,T3,T4,T5) are provided, which are cropped out from an object plane (OE). The former sub-system consists of a three layered lens component, which has the form of a meniscus deflected towards the object plane. The latter sub-system has two converging lenses (L4,L5), which are made of fluorine crown glass. The third sub-system consists of a three layered lens component and a two layered lens component, where the two layered lens component has a converging lens (L9) and a diverging lens (L10).
3 citations
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TL;DR: The features of objectives intended for amateur and professional astronomical observations, and experimental compositions of the glass have been developed that make it possible to obtain apochromatic systems composed of two lenses.
Abstract: This paper discusses the features of objectives intended for amateur and professional astronomical observations. Type-OK4 crown glass with special dispersion behavior is used to achieve apochromatic correction in refracting objectives, since the technology for obtaining high-quality blanks made from this glass makes it possible to create apochromatic objectives with an entrance-pupil diameter of up to 304 mm. Experimental compositions of the glass have been developed that make it possible to obtain apochromatic systems composed of two lenses.
1 citations
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11 Sep 2013
TL;DR: In this article, a high-speed and small-volume mid-wave IR zoom lens capable of 16× magnification using a 320×256 IR FPA detector has been described, which can be continuously adjusted by simply moving two lens groups, which uses the root exchange theory.
Abstract: The high-speed and small-volume mid-wave IR zoom lens capable of 16× magnification using a 320×256 IR FPA detector has been described. The system magnification can be continuously adjusted by simply moving two lens groups, which uses the root-exchange theory. The object-image exchange theory and root-exchange theory are presented. The structure using root-exchange theory can get large zoom ratio with simple volume and the smooth zoom curve. Mechanically compensated IR zoom lens design has these questions: firstly, big volume caused by complex optical structure; secondly, limited IR material and obvious focus shift with temperature change. The zoom lens using mechanically compensated method has solved all the questions that existed in traditional system. The system also contains much less optical material and has a very simple structure by using DOE elements. The element of first moving group and the second element of the second moving group are both DOE. As the DOE has minus Abb number, which is opposite of refractive materials, it can minimize the higher order chromatic aberration. Based on the characteristics, the chromatic aberration was balanced. Research on the thermal analysis and compensation is considered. The passive athermalization is made by DOE elements. DOE elements make the zoom lens maintain its performance when it is operating between -20°C and 60°C.The results show the high magnification zoom lens design performance, with small volume and light weight. The aberration of the system were well corrected and diffraction limited performance was achieved in required temperature range.
1 citations
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TL;DR: In this paper, a broadband and large aperture apochromatic collimator was designed, which worked in band of 400~1, 000 nm, half field of view was 2.2°, relative aperture F 2.8, and focal length was 135 mm.
Abstract: High accuracy spectral tunable calibration light source is a novel calibration light source,which especially accounts for the stringent calibration requirements of hyper-spectral remote sensors.A broadband and large aperture apochromatic collimator was designed.The lens worked in band of 400~1 000 nm,half field of view was 2.2°,relative aperture F was 2.8,and focal length was 135 mm.According to the corrected formula of parial dispersion(P) and Abbe number(ν),the original optical structure was acquired,based on the principles of apochromatic lens design.The secondary spectrum was corrected well with the help of Zemax software.At last,the lens was apochromatic in the whole working band with secondary spectrum residual of about 0.04 mm,and other aberrations are balanced well.The Lens's MTFs are better than 0.8 at spatial frequency of 37 lp/mm,which meet the requirements of the light source system.
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TL;DR: In this paper, it was shown that a bend-free drift-quadrupole system can transport certain incoming beam ellipses without introducing first-order chromatic distortions, which is not a rare special case, but a general property.
Abstract: Though a straight drift-quadrupole system can not be made an achromat, there exists an example of a bend-free drift-quadrupole system which can transport certain incoming beam ellipses without introducing first-order chromatic distortions. In this paper we show that such a possibility is not a rare special case, but a general property. For every drift-quadrupole system there exists an unique set of Twiss parameters, which will be transported through that system without first order chromatic distortions. Moreover, we prove that at the same time these Twiss parameters minimize the absolute values of the system chromaticities and also bring the second order effect of the betatron oscillations on the longitudinal dynamics to the minimal possible value.
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TL;DR: A digital camera with two prism arrays is applied to capture a stereo image of the corrected chromatic aberration and distortion, and the camera distortion can be increased, and reduced by the lens optimization.
Abstract: We apply a digital camera with two prism arrays to capture a stereo image of the corrected chromatic aberration and
distortion. The doublet prisms are used to correct chromatic aberration. The camera distortion with two prism arrays can
be increased, and reduced by the lens optimization.