Search results for "achromatic"
showing 10 items of 49 documents
Intraepidermal morphologic manifestations in lysosomal diseases.
1989
This paper reports the ultrastructural findings for the epidermis of biopsied skin specimens in numerous lysosomal diseases, which can be grouped as follows: a) presence of vacuolar lysosomal residual bodies in mucopolysaccharidoses I, II and III, Salla disease, GM 2 -gangliosidoses and infantile type II glycogenosis; b) avacuolar lysosomal residual bodies in Niemann-Pick disease type C, mucolipidosis IV, Farber disease, Fabry disease, and late infantile and juvenile neuronal ceroid-lipofuscinoses; c) absence of lysosomal residual bodies in GM 2 -gangliosidoses, metachromatic leukodystrophy, Gaucher disease and sialidosis type III Whenever possible, a biopsy of the skin for morphological di…
ALTERED RATIO BETWEEN AXON CALIBER AND MYELIN THICKNESS IN SURAL NERVES OF CHILDREN
1978
ABSTRACT Maturation of myelin sheaths in normal sural nerves of children proceeds more slowly than axon growth. This asynchronous development of axons and myelin sheaths results in a statistically significant change of the ratio between axon caliber and myelin thickness during normal development. Therefore, myelin thickness of individual nerve fibers must be related to the size of the axons as well as to the age of the individuals studied. Abnormalities of the relationship between myelin thickness and axon diameter (primary hypomyelination of large, or small, or all fibers) were clearly identified in cases with metachromatic leukodystrophy, KRABBE's, DEJERINE-SOTTAS’, COCKAYNE'S and SANFILI…
Achromatic Fresnel diffraction patterns
1993
Abstract A novel method for obtaining a single, but arbitrary, achromatic Fresnel diffraction pattern of any pupil with broadband parallel illumination is presented. The optical device simply consists of an achromatic objective and an on-axis zone plate. A criterion for selecting the system parameters in order to minimize the residual chromatic aberrations is given. The recording of the selected diffraction field is obtained with low chromatic aberrations even for white-light illumination. An experimental verification is shown to illustrate this approach.
White-light Fourier transformer with low chromatic aberration.
1992
A simple Fourier transformation system working with broadband parallel illumination is presented. The proposed setup, consisting of two on-axis zone plates and an achromatic objective, allows us to obtain the achromatic Fourier transform representation of the input at a finite distance with a low chromatic aberration. The discussion of the system, using the Fresnel diffraction theory, leads to an analytical expression to evaluate the transversal and longitudinal chromatic aberrations. It is shown that the resulting chromatic aberrations for typical values of the involved parameters are less than 1% over the entire visible spectrum.
Scale-tunable optical correlation with natural light
2008
We describe two different scale-tunable optical correlators working under totally incoherent light. They behave as spatially incoherent wavelength-independent imaging systems with an achromatic point-spread function (PSF). In both cases it is possible to adapt the scale of the achromatic PSF, i.e., to modify the scaling factor of the PSF and preserve the chromatic compensation, by one's shifting the input along the optical axis. The remarkable properties of these systems allow us to carry out a scale-tunable color pattern-recognition experiment with natural light.
Hybrid (refractive-diffractive) Fourier processor: A novel optical architecture for achromatic processing with broadband point-source illumination
1998
We report on an achromatic Fourier processor constituted basically by a quasi-wavelength-independent imaging forming system whose first half performs an achromatic Fourier transform of the colour input. The novel optical architecture, only formed by a small number of diffractive and refractive lenses, works under white-light point-source illumination and provides an intermediate achromatic real Fraunhofer plane and a final colour image without chromatic distortion. In this way, our optical processor performs simultaneously, with a single filter, the same spatial filtering operation for all the spectral components of the broadband illumination. The practical capabilities of our proposal are …
Quasi-wavelength-independent broadband optical Fourier transformer
1999
The chromatic behaviour associated with diffractive optical elements is exploited herein to design a hybrid (diffractive-refractive) lens triplet showing very great wavelength-compensation capabilities for the Fraunhofer diffraction pattern of any diffracting screen under broadband point-source illumination. Within the paraxial Fresnel diffraction theory, we show that perfect compensation for the axial position of the Fourier transform of the input can be accomplished if we neglect the secondary spectrum of the refractive objective. Simultaneously, an achromatic correction for the scale of the Fraunhofer pattern is achieved. In this way, even for white light, only a low residual transversal…
F-GAMMA: On the phenomenological classification of continuum radio spectra variability patterns of Fermi blazars
2012
The F-GAMMA program is a coordinated effort to investigate the physics of Active Galactic Nuclei (AGNs) via multi-frequency monitoring of Fermi blazars. In the current study we show and discuss the evolution of broad-band radio spectra, which are measured at ten frequencies between 2.64 and 142 GHz using the Effelsberg 100-m and the IRAM 30-m telescopes. It is shown that any of the 78 sources studied can be classified in terms of their variability characteristics in merely 5 types of variability. It is argued that these can be attributed to only two classes of variability mechanisms. The first four types are dominated by spectral evolution and can be described by a simple two-component syst…
Die elektronenstreu-apparatur am mainzer 300 MeV-elektronen-linearbeschleuniger
1972
Abstract In this paper, we attempt to give a general survey and a comprehensive description of the most significant features of the facilities for electron scattering experiments at the Mainz 300 MeV Linear Accelerator, along with a list of literature, where more detailed information on certain subjects can be found. The accelerator provides energies between 80 and 300 MeV. Scattering angles are available up to 160° resulting in a momentum transfer region up to 3.0 fm −1 . The overall experimental resolution is 0.1%. Cross sections down to 10 −34 cm 2 /sr can be measured. The main features of the apparatus are: an achromatic magnet system with 90° deflection, a double focusing spectrometer,…
Achromatic fan-out diffractive system for white-light free-space optical interconnects
2001
Abstract A simple and versatile white-light fan-out diffractive system based on the achromatization of the fractional Talbot effect is proposed. This achromatic configuration is able to interconnect a single polychromatic point source with a 2-D array of optoelectronic microdevices with low residual chromatic aberration even for white light. The whole broadband beamsplitter system is formed by two simple diffractive optical elements, a periodic diffractive lenslet array and a diffractive lens, that are made with a direct laser writing technique giving high light efficiency. The focal amplitude distribution corresponding to the lenslet array produces, by free-space propagation, self-replicas…