摘要:

It is shown by a computer simulation that a hybrid pseudo-random scanning system may be used for real-time analysis of the structural properties of two-dimensional pseudo-random arrangements of binary screens. It could be used for texture real-time analysis or image pre-processing.

ISSN:0030-3909    

DOI:10.1080/713820866

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Texture differences in a picture are difficult to analyse by digital techniques, but can be identified readily by optical spatial filtering. However, purely optical processors have several disadvantages. A low-cost system is described in which the output from an optical processor is digitized and processed by a microcomputer to produce a colour-coded image. This makes it possible to use the parallel processing capability of the optical processor for preliminary data reduction, while retaining the flexibility and interactive capability of a digital computer.

ISSN:0030-3909    

DOI:10.1080/713820879

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Optical spectrum analysis of coherent 1-D signals scanned in a TV format is accepted as the most powerful technique for the processing of large time-bandwidth products. From recent developments, it has been expressed as an analog implementation of the FFT. Nevertheless, in its usual analysis as a ‘folded spectrum’, little attention has been paid to the effects of the 2-D raster on the coherence of the signal, which the present study shows to be of great importance. From experimental data, a new theoretical approach is derived, which suggests drastic limitations for the spectrum analysis of wide-bandwidth signals.

ISSN:0030-3909    

DOI:10.1080/713820867

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A novel approach to frequency multiplexing of images is presented. By modulating each image pixel at a different (temporal) frequency, the entire image can be transformed into an electrical signal utilizing a single detector. The electrical current of the detector is proportional to the spatial Fourier transform of the image, allowing one to perform spatial frequency manipulations in the time domain. The multiplexing is obtained by using a two-dimensional array of piezoelectric-elasto-optic modulators. By utilizing these effects one makes use of the mechanical resonance of the crystals simplifying the electrical signals needed for excitation. It is shown that a similar (or the same) modulator can be used for image reconstructions; i.e. performing the inverse Fourier transform. Preliminary results obtained with quartz crystals prove the feasibility of this approach.

ISSN:0030-3909    

DOI:10.1080/713820874

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

For quite general optical systems using a certain known auxiliary object, an interferometric method for reconstructing the object in a unique way from intensity data at the output plane of the system has been presented.

ISSN:0030-3909    

DOI:10.1080/713820875

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

This paper deals with the behaviour of a non-coherent field passing through a transparency. It is shown that by means of suitable transparencies, well defined and constant coherence areas can be generated, allowing non-coherent processings. Two examples of such processings are briefly described.

ISSN:0030-3909    

DOI:10.1080/713820860

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The coherence of a laser beam passing through multimode fibres shows considerable variation. Experiments have been carried out in order to investigate this variation. The visibility of interference fringes is taken to be a measure of coherence. A He-Ne laser (632·8 nm wavelength) was used, with a multimode step-index fibre, a multimode graded fibre (Selfoc fibre) and a single-mode step-index fibre. The azimuthal angle of polarization and the degree of polarization of a beam passing through a single mode fibre show little variation compared to a multimode fibre. The visibility of interference fringes produced by two beams passing through either one or two single-mode fibres have an extremely small variation compared to the multimode fibre. The variation of the coherence of a beam passing through a multimode fibre is due to the superposition of different modes produced by the beams being transmitted. The value of visibility obtained by inserting a polarizer to get equal azimuthal angles of polarization is on the whole larger than that obtained without a polarizer. Another cause of the variation of the coherence of a beam passing through the multimode fibre is the different azimuthal angles of polarization produced by beams passing through one fibre.

ISSN:0030-3909    

DOI:10.1080/713820880

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The transmission and reflection properties of a waveguide resonator with DBRs are described near and at the Bragg condition using the method of coupled waves. Different grating configurations characterized by their coupling coefficients, attentuation parameters, and geometric dimensions are included to investigate symmetrical and asymmetrical resonator configurations. Possibilities of realizing tunable systems and optically bistable devices are also mentioned.

ISSN:0030-3909    

DOI:10.1080/713820885

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Electro-optical crystals are used for real-time holography, optical data storage, optical information processing and more recently for speckle applications. Many ferro-electric materials were investigated, the Bi12SiO20(BSO), a cubic, para-electric and electro-optic material was found to be very useful for real-time holographic interferometry and speckle applications. For the application of the BSO in real-time metrology, the crystals is usually biased with a transverse electric field in the 110 or 100 crystallographic direction. Illuminating the crystal with spatially structured information in the 110 direction as a result of a hologram or speckle pattern, a space charge field is built up, leading to a refractive index variation in the crystal. Double-exposure techniques and time average exposure will be presented for real-time deformation displacement and vibration analysis and for contour line holography using a two-wavelengths method. Young's fringes of double-exposed, or in the time-average recorded speckle patterns will be attractive for real-time deformation displacement and vibration analysis.

ISSN:0030-3909    

DOI:10.1080/713820877

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Communication by spectral modulation of white light was proposed a few years ago and has been demonstrated via electro-optic techniques. Compared with conventional modulation intensity systems, the present method takes advantage of simultaneous transmission and reception of analogue signals without any electronic coding of the information. The information is carried along the chosen channel in the form of time-varying path differences between wave-groups of white light. In the device proposed here, these path-differences are introduced at the emission stage by using a set of birefringent quartz plates and transverse electro-optic modulators acting as delay lines. The propagation medium is the atmosphere (steady or turbulent) or any type of light pipe (e.g. a fibre bundle). At the reception stage, the signals are led to a detector PIN array after decoding via Fourier transform spectroscopy; another set of birefringent quartz plates introduces path-differences tuned on and matched with the various carriers. Experiments dealing with simultaneous transmission of video signals (e.g. T.V. images) in a multimode fibre illuminated in white light are reported; various images with several levels of grey have been transmitted and displayed on T.V. monitors. Colour images are transmitted as well.

ISSN:0030-3909    

DOI:10.1080/713820856

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor