The main aim of this study is to extending the holographic interferometry technique to measure the effect of the temperature ramp-up rate on the warpage of IC packages in the IR-reflow process . It is noted that both the warpage and the ambient temperature change can cause image fringes. Therefore, an auxiliary sphere is used to identify the fringe numbers caused by the ambient temperature change during the experiment. Then, the Taguchi method will be deduced to study the effect of the temperature ramp-up rate and peak waiting temperature on the warpage of PBGA package in the IR-reflow process.

No description available.

Two collimated laser beams, wavelength O-514 μm are overlapped within a crystal of heavily iron doped lithium niobate to form a one-dimensional volume holographic grating, a few mm long, designed to behave as a highly selective filter at near infra-red wavelengths. A novel recording geometry is described and a variety of diagnostic experiments are undertaken to determine the main characteristics of the grating. A filter fabricated using this method is used to obtain single mode operation from a 1-55 μm semiconductor laser. The historical survey of holography contained in chapter one emphasizes the dynamic properties and applications of photorefractive recording materials. Standard results of two mathematical theories, kinematic and coupled-wave, are used in chapter two to predict the properties of a Bragg grating when replayed with infra-red light. Chapter three details the recording materials suitable for an infra-red filter, followed by a discussion on the concept of 'scaling'. The recording mechanism of iron doped lithium niobate, including its fixing and erasure process, is presented in chapter four as a basis for selecting the most advantageous crystal characteristics. Mathematical models describing the complex dynamic recording process in iron doped lithium niobate are introduced in chapter five. A novel recording geometry involving the use of two prisms is critically described in chapter six, from initial conception to final implementation. The performance of the grating as an infra-red filter is assessed in chapter seven by measuring the angular response of the transmitted and diffracted beams at a wavelength of 1-152 microns. Chapter eight discusses the applications for volume holographic filters, with particular reference to one example. In chapter nine general conclusions are drawn and future directions for research are suggested. A number of appendices are also included.

Holographic lithography is a new technique developed for the fabrication of threedimensional photonic crystals in polymer. Four coherent laser beams are interfered to generate a three-dimensionally periodic interference pattern in a film of photoresist. Subsequent processing steps render a three-dimensional photonic crystal, whose structure is commensurate with the original interference pattern. Two interference patterns are discussed in detail: a face-centred cubic pattern with a conventional lattice constant of 922nm in air and a face-centred cubic pattern with a conventional cube side of 397nm in air (interference wavelength 355nm). Three types of basis are presented for the interference pattern with a 922nm lattice constant: a righthanded, a left-handed and a non-chiral basis. Photonic crystals have been fabricated with both a chiral and a non-chiral basis and evaluated by scanning electron microscopy. Optical transmission measurements are presented for the non-chiral photonic crystals and are interpreted in both a Bragg scattering model and a photonic bandstructure model. A 'GaAs' and a 'diamond' basis are presented for the interference pattern with a 397nm lattice constant. Photonic crystals have been fabricated with the 'GaAs' basis and evaluated by scanning electron microscopy.

This thesis is concerned with the experimental determination of surface displacements of material foils by means of an automatic evaluation of the holographic interferograms obtained in testing. The experimental work utilizes a newly developed method referred to as the "holographic-electro-optical" technique that employs a specially designed microcomputer unit. The experimental procedure and the microcomputer organization are fully described. The application of this technique is illustrated by the evaluation of strain field and thickness changes at a large number of points on both sides of a commercial newsprint paper sample subjected to uniaxial loads. Furthermore, a new quantity called the "volumetric mass density" is introduced for this material for the first time that is experimentally evaluated and correlated to the obtained strain field. In the conclusion of this thesis general remarks concerning the holographic-electro-optical technique are given and the obtained results for the newsprint sample and future research are indicated.

Through a holographic recording a property from the third dimension, the depth, is obtained in the form of a phase map of the incident light. One wavelength holography will have a unique phase for the depth range corresponding to the wavelength of the light and outside this range the real depth can not be resolved. By introducing more wavelengths to the measurement the unique phase combination of the waves will have a wider range and larger objects can be resolved. Up to six wavelengths can be simultaneous recorded by making them occupy different spatial frequencies. A set of spatial frequencies together describing a property of the wave is referred to as a lobe. For more than 6 wavelengths and a larger depth range produced by a more seldom repeated unique phase combination the individual waves will occupy the same frequencies, i.e. the lobes overlap. The separation of overlapping lobes is essential in order to make precise and time independent measurements of large and/or moving objects. To separate the lobes the complex fields, i.e. the phases together with the amplitudes, were simulated to propagate a distance and again recorded. The propagation leads to a phase shift of the spatial frequencies which reveals the complex fields in the case of two overlapping wavelengths. For three overlapping wavelengths the resolution, i.e spatial frequencies describing the object, has to be reduced in order to determine the individual complex fields. Since the propagation is a linear transformation for the frequencies that do not overlap, only the overlapping elements whose propagation is nonlinear produce new information. The new information gained is therefore independent of the number of wavelengths used which limits the exact determination of the fields to two wavelengths. Through the holographic recording another property of the complex field is obtained which is the superimposed individual intensities. This bounds the complex fields to certain values, i.e. restricts the possible amplitude of the waves. The recording in the two planes produces two intensity distributions which both must be satisfied by the complex fields. The optimization model for this was formulated and a simple optimization algorithm was implemented. Instead of an equality constraint of the intensities the inequality constraint was implemented, mainly due to that the optimization process was out of the scope of the thesis and the inequality constraint resulted in a simple implementation. The result pointed out important properties even though the optimization could not separate the fields satisfactorily for more than three wavelengths. The inequality constraint contains enough information to solve the case of three overlapping wavelengths.

Thesis--Karolinska Institutet. / Extra t.p. with thesis statement inserted. Four articles by the author reprinted from Acta odont. Scand. and Sc. ed. bull. in pocket. Includes bibliographical references (p. 31-34).

Thesis--Karolinska Institutet. / Extra t.p. with thesis statement inserted. Four articles by the author reprinted from Acta odont. Scand. and Sc. ed. bull. in pocket. Includes bibliographical references (p. 31-34).

A time-resolved holographic interferometer specially suited for high-speed visualization of the gas flow in shock tube experiments has been developed. Holographic interferometry, which is based on the recording of two coincident holograms at different times so that one of them acts as a reference field, can accurately reveal the density distribution in a gas. The device described here fills the need for a practical method to record short sequences of holographic interferograms documenting the evolution of shock wave reflections that are not self-similar in time. Multiple hologram recording was implemented on an existing holographic interferometric system through the technique of spatial frequency multiplexing, in which the holograms are overlaid but the reference beam is angled differently for each exposure. Because the object beam is not involved in the multiplexing process, the imaging optics of the original system could be left unmodified. The upgrade only entailed the introduction of an angular sweeping system in the reference beam path. The beam multiplexing assembly was initially based on a spinning mirror design, which produced fairly satisfactory recordings of non-interferometric holographic sequences but was incapable of accurately overlaying a second set of exposures establishing the reference field for each image. The mechanical sweeping system had other drawbacks as well, among them the tendency to create extraneous fringes in the holographic images because of the unavoidable angular motion of the reference beam over the duration of a laser pulse. A solid-state multiplexing system was then devised in which the reference beam was split into several branches, each aimed at the film from a different direction and individually shuttered by a ferroelectric liquid crystal light valve. Beam sweeping was achieved by opening the shutters in sequence as the laser was pulsed, but it was also possible to record the reference exposure on all images simultaneously with a single laser pulse by having all shutters open at the same time. A prototype three-image system was constructed and successfully tested by recording interferometric sequences of a shock wave reflecting off a model at framing intervals down to 100 μs. / Graduate

Phoropters are the most common instrument used to detect refractive errors. During a refractive exam, lenses are flipped in front of the patient who looks at the eye chart and tries to read the symbols. The procedure is fully dependent on the cooperation of the patient to read the eye chart, provides only a subjective measurement of visual acuity, and can at best provide a rough estimate of the patient's vision. Phoropters are difficult to use for mass screenings requiring a skilled examiner, and it is hard to screen young children and the elderly etc. We have developed a simplified, lightweight automatic phoropter that can measure the optical error of the eye objectively without requiring the patient's input. The automatic holographic adaptive phoropter is based on a Shack-Hartmann wave front sensor and three computer-controlled fluidic lenses. The fluidic lens system is designed to be able to provide power and astigmatic corrections over a large range of corrections without the need for verbal feedback from the patient in less than 20 seconds.