摘要:

As an application of Fourier filtering in the object space, an in-line far-field holography configuration is considered where a detuned interference filter is placed between the diffracting object and the holographic plate. With suitable adjustment of the parameters, such a technique allows the relative amplitudes of the reference and the object beam to be controlled. This results in a modified visibility distribution of the interference fringes, and finally in a faster aperture that better defines the position in depth of the diffracting object during reconstruction. Theoretical computations and preliminary experimental results are presented.

ISSN:0030-3909    

DOI:10.1080/713820873

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Described here is an optical method for imaging a diffused plate, which vibrates angularly; the same optical configuration was applied for defining the dynamic strain distribution over the whole plate. The sensitivity of the measurement was 5·2 microstrains.

ISSN:0030-3909    

DOI:10.1080/713820861

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A new method is presented for the measurement of surface roughness in the range Ra,0·05–10 w m. The data from a strongly defocused low-contrast image of a rough surface is scanned, and the contrast value,C= † I d I ¢, is processed. A relatively low degree of spatial and temporal coherence, combined with a relatively high-image aperture and a detector aperture (which is much wider than the nominal speckle width of the corresponding highly coherent speckle pattern) led to important instrumental advantages, e.g., illumination by an incandescent lamp, simple photodetectors, short measuring times and simple, inexpensive, compact construction. The superposition of uniform intensity to the phase contrast structure, which leads to a strictly monotonic dependence of the measured contrast over a very wide range of the roughness values R a is of great importance. Practical measurements of metallic surface standards are reported and discussed, and the theoretical aspects of the superposition of uniform intensity are pointed out with the help of a new analytic expression for the stochastic contrast.

ISSN:0030-3909    

DOI:10.1080/713820876

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Materials with certain values of the partial dispersion / 12 = [n(u1) mn(u2)]/[n(u1) mn(u3)] and the Abbe number x2= [n(u2) m1]/[n(u1) mn(u3)] are needed in different wavelength regions for the construction of dispersion corrected optical systems. Using a one-oscillator model forn(u) due to Wemple, we investigate the predictions of this model for the n - x -diagram and the / - x -diagram. The influence of a second oscillator is also discussed and compared with experimental results for optical glasses and crystals. The location of the second oscillator is correlated with that of the first one.

ISSN:0030-3909    

DOI:10.1080/713820859

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Several methods of non-coherent optical processing for the recording on film of industrial drawings for archive purposes are described. Several types of film for recording the filtered data are investigated.

ISSN:0030-3909    

DOI:10.1080/713820865

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

We have measured the optical transmittance of composite Au-Ag granular films deposited on quartz slides, before and after annealing, by gas evaporation technique. The crystalline, morphological and compositional structure of these composites have been studied carefully by transmission electron microscopy. The optical data of the annealed samples have been interpreted by the Maxwell-Garnett theory incorporating the formation of alloy grains in them. A satisfactory agreement between theory and experiment has been achieved.

ISSN:0030-3909    

DOI:10.1080/713820864

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

This paper gives a comprehensive survey of the chromatic correction, imaging quality, and spherochromatic aberrations of imaging systems consisting of two or three holographic optical elements (HOEs). HOEs generally represent holographic lenses and holographic gratings. By a suitable combination of two or more HOEs the transversal and longitudinal chromatic aberrations of imaging systems consisting of HOEs can be corrected. The quality of such imaging systems is measured in terms of optical transfer functions (OTFs), and may be demonstrated by transversal ray aberrations. In experiments, OTFs for polychromatic and nearly monochromatic, spatially incoherent radiation are measured and compared with theoretical results. With a system consisting of one holographic grating and one holographic lens only, the transversal chromatic aberration can be corrected. In a system of two or more holographic lenses, however, the longitudinal chromatic aberrations can also be corrected. A system of two holographic lenses behaves like an achromat and a system of three holographic lenses behaves like an apochromat. The measured and calculated OTFs give the quality of such systems in terms of aperture, wavelength range, wavefront aberrations and image field, where the residual aberrations after chromatic correction are the spherochromatic aberrations of different order and the geometrical aberrations introduced by imperfect optical components during the recording of HOEs. With the OTF as a merit function, closed solutions on the basis of the Kirchhoff-Fresnel diffraction integral and computer optimization programs based on ray-tracing show the behaviour and the best geometrical parameters for each system of HOEs. After computer optimization, the best image plane frequently differs considerably from the image plane given by the expression for achromatic behaviour (achromization condition) in the case of large wavelength ranges.

ISSN:0030-3909    

DOI:10.1080/713820862

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Influences of two different developing methods on the optical parameters of dichromated gelatin (DCG) were studied. These two processes for obtaining DCG plates ready for use have been presented by Meyerhofer and Chang and Leonard. The difference between these methods is that the latter involves a hardening process after exposure. The gelatin layers used were obtained from Kodak 649F photographic plates by removing the silver halide. By using the first method, it was observed that the absorption modulation, and hence also the refractive index modulation, penetrate during exposure through the whole DCG layer. The gratings begin to saturate when the exposing energy exceeds 200 mJ cmm 2. In the second method absorption was low. According to our measurements the modulations can reach only 20–30 per cent of the grating thickness. Because the diffraction efficiency of this hologram can be nearly 100 per cent, the refractive-index modulation is very high.

ISSN:0030-3909    

DOI:10.1080/713820882

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A method is presented for obtaining optical reconstructions from holograms recorded at wavelengths that are substantially longer than optical ones. The method makes use of a reference wave that is added digitally to the recorded wave front. The reference wave is constructed so that there is a minimum mean square deviation between the reconstructed wave from a given object point and an ideal wave from the same point at the reconstruction wavelength. The hologram scaling factor, the size of the reconstructed object and the position of the reconstructed object relative to the reconstructing hologram can be chosen in the optimization procedure. Thus it is possible to make several scaled down holograms from one recording to improve the depth resolution of the reconstruction. The main function of the optimized reference wave is to compensate for aberrations due to the discrepancy between the size of the original hologram measured in recording wavelengths and the size of the scaled down hologram measured in reconstruction wavelengths.

ISSN:0030-3909    

DOI:10.1080/713820886

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Conventional Coudé systems on telescopes are notoriously inefficient because of light loss and image degradation. A design is presented that will convert the conventional Coudé of the existing Leoncito 2·2 m telescope to a more efficient arrangement using small high-reflectance mirrors. The conversion is designed to require a minimum of changes to the existing structure.

ISSN:0030-3909    

DOI:10.1080/713820857

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor