abstract: Two-dimensional vision-based measurement is an ideal choice for measuring small or fragile parts that could be damaged using conventional contact measurement methods. Two-dimensional vision-based measurement systems can be quite expensive putting the technology out of reach of inventors and others. The vision-based measurement tool design developed in this thesis is a low cost alternative that can be made for less than $500US from off-the-shelf parts and free software. The design is based on the USB microscope. The USB microscope was once considered a toy, similar to the telescopes and microscopes of the 17th century, but has recently started finding applications in industry, laboratories, and schools. In order to convert the USB microscope into a measurement tool, research in the following areas was necessary: currently available vision-based measurement systems, machine vision technologies, microscope design, photographic methods, digital imaging, illumination, edge detection, and computer aided drafting applications. The result of the research was a two-dimensional vision-based measurement system that is extremely versatile, easy to use, and, best of all, inexpensive. / Dissertation/Thesis / M.S.Tech Technology 2011

<p> It is shown that the resolution of virtual images of dye-doped dielectric nanospheres obtained through dielectric microspheres can be increased beyond the classical diffraction limit by decreasing the period of nanoplasmonic array used for localized plasmonic structured illumination of these objects. In addition, it is also shown that post-imaging processing, which represents an intrinsic part of structured illumination microscopy, is not required for achieving the super-resolved images. This observation is interpreted due to the fact that the radiation of objects placed at the surface of nanoplasmonic arrays with sufficiently short periods can be almost completely redirected into folded dispersions of nanoplasmonic array, so that the diffraction orders responsible for super-resolution are more efficiently coupled to dielectric microspherical antenna compared to that for the uncoupled radiative modes. </p><p> Focal plane arrays (FPAs) are pixelated arrays of photo detectors which are widely used for imaging. The problem of uncooled mid-wave infrared (MWIR) FPAs is related to their large thermal noise. In this work, it is demonstrated that the surface area and thermal noise of pixels can be reduced without sacrificing their sensitivity by using integration with dielectric microspheres, which can be achieved by a novel method of suction assembly of microspheres in microhole arrays. In addition, it is demonstrated that alternative solution of this problem is offered by integration with microconical light concentrators, which can be fabricated by various well-established technologies including the use of the Nanoscribe. Using a simplified two-dimensional (2D) model, it is studied how the photocurrent depends on the geometrical parameters of microcones and on the angle of incidence. </p><p> The photoinduced aggregation of nanoparticles is of interest for material science and nonlinear optics applications. Light-driven assembly of nanoplasmonic particles is observed as an optical memory effect taking place due to the aggregation of 20 nm gold nanoparticles in the illuminated regions of the substrate after full evaporation of the liquid suspension. It is shown that the level of photoexcitation intensity required for observation of this effect is several orders of magnitude smaller compared to that in the previous studies of photoinduced aggregation typically performed using intense laser illumination. It is also demonstrated in a preliminary way that the photoinduced aggregation is facilitated in the spectral range resonant with localized surface plasmon resonances in nanoparticles. </p><p> Inverse scattering algorithms are of interest for many applications; however, they are usually based on low refractive index contrast approximations and measuring the phase distributions. In contrast, Globally Convergent Inverse Scattering (GCIS) algorithms in principle should allow phaseless image reconstruction for high refractive index objects. In order to test the operation of GCIS algorithms, high-index (n~2) barium titanate glass microspheres were assembled directly at a silicon chip of a cell phone camera and the scattering patterns resembling the shape of the Airy disks were detected using a set of narrow spectral filters throughout a broad range of wavelengths in the visible regime. The results were found to be in a good agreement with the image calculations and can be used for the object reconstruction based on GCIS algorithms.</p><p>

The primary objective of the work described in this thesis was to devise a red-sensitive photoresist imaging process for use in the replication of diffraction optics. In the introduction the chemistry of conventional photopolymer systems and photoresists used for holographic recording and the fabrication of diffraction gratings and diffracting optical elements is reviewed. The limitations of commercially available photoresist systems, particularly for applications requiring the use of red light are discussed. A polymer system has been investigated which could be imaged by photochemically generated free radicals, followed by a simple aqueous development procedure as required by the original specification. The polymer chosen for study was a copolymer of methyl methacrylate, methacrylic acid and 2-hydroxyethyl methacrylate. This was derivatized using methacryloyl chloride or methacrylic anhydride in order to introduce cross-linkable units to the polymer backbone. Polymers have been characterized by a number of techniques and the effect of varying composition on aqueous base solubility has been thoroughly studied. Various methods of derivatization have been employed. The ease of imaging has been found to be very sensitive to both the composition of the polymer and the extent of functionalization. High quality images have been obtained from this polymer using an organic solvent developer. Imaging experiments have been carried out on thin films of the photopolymer coated on glass using phenylazotriphenylmethane (PATM) as photoinitiator. Good images of 100 lines permillimetre (1 mm^-1) have been recorded by contact printing. Interferometry has been used to demonstrate that interference patterns having 600 and 1200 1 mm^-1 can be recorded using this polymer with PATM as initiator, exposed to an argon ion laser operating at 458nm. A number of two component photoredox initiator systems have been investigated, the light absorbing species of such systems being a dye such as methylene blue or certain cyanine dyes. The second component of these initiators may be an aryl sulphinate salt, a 1,3-diketone or some alkyl sulphides. The red light-initiated phatopolymerization of acrylamide has been demonstrated using some of these initiators and a low resolution photopolymer image has been recorded using Azure A and perinaphth-1,3-indandione as the photoinitiator system. This polymer can, in principle, produce images over a wide range of wavelengths depending on the nature of the initiator used.

Firstly, a survey is given of excitation processes occurring in gas discharges, together with an analysis of selective excitation processes in gaseous optical masers. Hollow cathode discharges have been investigated as excitation media for gas lasers. Evidence is given for the establishment of a relationship between the 632.8nm helium-neon laser discharge and transition weak to strong discharges. An optimum electron temperature for oscillation on the 632.8nm line is indicated. In a pulsed helium-iodine discharge, oscillation is reported on four new laser transitions, one an intercombination transition. Simultaneous oscillation for the first time is reported on hyperfine components of the ionised iodine lines. Hyperfine intervals of the 6p and 6s levels have been established, giving agreement between calculated and observed hyperfine components of lines. These levels are shown to be strongly perturbed. An anomalous behaviour is reported on hyperfine oscillations on the658.5nm line, which can be attributed to non-equilibrium in the populationof hyperfine sublevels of the 6s level,due to pressure/current changes. Results support the proposal that charge transfer is the selective excitation mechanism in the helium-iodine laser.

The influence of liquids in the laser beam on the emission and propagation characteristics of intense pulsed neodymium lasers is described. Results are presented on Q-switching by a thermal effect in organic solvents, on basic self-modulation and mode-locking processes in an oscillator, and on the transmission and amplification of picosecond light pulses in an inorganic liquid laser.

New techniques have been developed for the analysis of reflection data obtained from metal surfaces. An optimization study has been carried out and it has been shown that for n and k values observed for metals optimization becomes critical. Optimized reflection techniques have been used in experimental studies on terbium and gadolinium films prepared in ultra high vacuum, and the resulting optical conductivity curves are shown to be in good agreement with the predictions of a simple theory based on inter band optical transitions.

The dependence of certain properties of nitrogen lasers on various parameters have been examined and the design of two original nitrogen lasers is presented. The output characteristics of these lasers have been studied as a function of gas pressure, gas flow rate and direction, applied potential, repetition rate, electrode geometry, drive circuitry including the effects of preionization, and the effect of optical feedback by the addition of an optical cavity. The operation of these two lasers in a master oscillator/power amplifier configuration is described and the optimization of this system by varying the drive circuit parameters has been achieved. In the optimized state this configuration produced as much energy per pulse as did the amplifier when operating separately as an oscillator. However, the oscillator/amplifier system produces an output with some additional useful characteristics, such as lower beam divergence and a high degree of polarization. The design of a dye laser which uses a grating at grazing incidence and three mirrors is described. This laser utilizes the polarized output from the oscillator/amplifier system to generate simultaneously two independently tunable wavelengths. A novel pumping arrangement is used which ensures that there is no mode competition between the two wavelengths, that they can have any polarization ratio, that the linewidth of each wavelength can be independently varied and allows the two wavelengths to be generated in different dyes.

A brief survey is given of the progress made in the study and development of Q-switched lasers in recent years, and a review of the theory relevant to the work described, is outihed. A gain-switched giant pulse ruby laser system, employing two ruby rods of differing lengths in a single resonant cavity coupled with a rotating prism,has been developed. A systematic study of the output characteristics of this system under various conditions has been carried out. High resolution spectroscopy, including nanosecond time-resolution, of the emission of this laser, and also of a Pockels cell switched laser, has rendered possible the direct observation of the axial and off-axial mode structure, and has shown the existence of an intensity dependent frequency shift towards higher frequency in the giant pulses. When the two ruby rods in the gain-switched device are differentially cooled, simultaneous two frequency output pulses with powers in the tens of megawatt region are obtained, the wavelength separation of the two frequencies being tunable from 1 to 5.5Å. The suitability of this device for certain experiments in non-linear optics, such as the generation of the sum and difference frequencies in crystals, and nonlinear resonance mixing in plasmas, is considered. The two frequency output of the laser system has been mixed in ADP, to generate the sum frequency, and the conversion efficiency of the latter process compared with that of second harmonic generation.

A general method, of approach to resonant non-linear optical phenomena involving travelling waves has been developed. Maxwell's equations are solved for the electric field in a spherical Fabry-Perot type optical resonator, which encloses uniaxial arisotropic media. The specific case of propagation perpendicular to the optic axis is considered but the theory can be extended to cover the general case including double refraction. In the presence of more than one optical field of this form, when the medium enclosed in the resonator is non-linear, by expanding the polarisation in terms of the electric field in the normal way coupled mode equations are obtained for amplitudes of the eigen modes concerned. This general formalism is then used to examine resonant second harmonic generation in the small conversion approximation from a fundamental beam in the lowest order 0-0 mode. Analytical solutions are obtained in three limiting cases, weak focussing, strong focussing and the focus removed infinitely from the non-linear medium. The general case is solved numerically. From the results the values of the variable parameters can he obtained which give the maximum output in any given mode. Graphs are presented giving the output variation in 0-0 and 0-2 modes with focus position, phase matching, focussing and spot size. From there it can be seen that the optimum focussing for the 0-0 mode occurs at 1/20 = 5.65 (1 crystal length, zo one half the confocal parameter). Secondly degenerate parametric amplification between two lowest order inodes is examined under the approximation that the pump beam is undepleted. An analytic solution is obtained for the single pass amplification in the weak focussing limit and preliminary results of numerical computations for the general case are given. From these results a value for the optimum threshold condition is calculated.

Methods for the production and detection of shock waves are reviewed with particular emphasis on the production of shock waves by exploding wires and by the absorption of energy from a pulsed laser system. An exploding wire system is described for the generation of shockwaves in perspex plates. Observation is made using the stress induced bi-refrigence, and 'time integrated' photographs of shock waves are produced. At lower energies the exploding wire produces a mixture of wire vapour and molten droplets. The disintegration of the droplets is shown and described in terms of the mechanism shown by Lane and Edwards⁽¹⁰⁴⁾ to operate forwater droplets. A modified Kerr cell shutter with an unsymmetric electrode geometry is described with reference to possible use as a fast light shutter for measuring shock wave velocities. A development of this shutter has one of the electrodes in the Kerr cell consisting of a stack of razor blades. Light which has been diffracted from an electrostrictively induced phase grating near the blade edges, has been detected. A number of mechanisms are described which take effect within the modified cell. A system for the production and detection of shock waves by a Q-switched ruby laser is described. Shock waves are produced in liquids both by electrical breakdown and by evaporation of the surface material from a metal target. Experimental results show the production of shock waves with velocities up to 10⁴ m/s in water. The ablation wave produced when the surface of a metal wire is evaporated by a laser has been photographed. This shock wave accelerates as it moves towards the centre of the wire. Finally, the process of stimulated Brillouin scattering is described as the pulsed laser is focused into a liquid.