Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Opto-mechanical design and analysis for coherent active imaging(Montana State University - Bozeman, College of Engineering, 2022) Neeley, Jaime Branson; Co-chairs, Graduate Committee: Wm. Randall Babbitt and Joseph A. ShawThe objective of this thesis project was to design a monostatic lidar transmit (Tx) and receive (Rx) opto-mechanical apparatus for remote sensing at a variable range of 50 m - 500 m. The scope of this project begins from the fiber output of a pre-designed Frequency-Modulated Continuous Wave (FMCW) lidar system. After design criteria for the lidar module are given, the optical and mechanical design is presented, opto-mechanical tolerancing is presented, and assembly, alignment, and testing procedures are covered as well. This thesis shows that the required design criteria of diffraction-limited optical performance was achieved while accounting for predictable manufacturing and assembly errors modeled using a Monte Carlo tolerance analysis. Furthermore, this thesis shows that the modeled and measured optical performance results were in good agreement and recommendations are given for improvements for the next-generation revision of the lidar Tx/Rx module.Item Characterization of a division-of-focal-plane polarization imager(Montana State University - Bozeman, College of Engineering, 2020) Syed, Musaddeque Anwar Al Abedin; Chairperson, Graduate Committee: Joseph A. ShawPolarization is a fundamental property of light that can be detected with polarization-sensitive instruments. Imaging polarimetry has an immensely wide range of applications, and while much has been accomplished in recent years, there is still a need for sensor systems with improved accuracy, precision, and stability. This paper presents the optical characterization of a commercial division-of-focal plane (DoFP) polarization imager, in an effort to evaluate its performance as a promising instrument in the application of ground-based cloud thermodynamic phase detection. Radiometric characterization values were well within the acceptable region, but the polarimetric contrast was in the range of 20-30, much lower than expected, which may be a result of the broadband measurements being impaired by poor polarizer performance at the blue end of the spectrum. Later, a narrowband polarimetric measurement at 532 + or - 5 nm produced a much enhanced result, with polarimetric contrast in the higher 300s, making the imager a viable option for many remote sensing applications. Also, all-sky imaging of clear daytime sky and its analysis of degree of linear polarization (DoLP) showed encouraging result.Item Development of an active/adaptive laser scanning microscope(Montana State University - Bozeman, College of Engineering, 2018) Archer-Zhang, Christian Chunzi; Chairperson, Graduate Committee: David L. DickensheetsLaser scanning techniques such as confocal microscopy and two-photon excitation fluorescence microscopy (TPM) are powerful tools for imaging biological samples with high resolution, offering three-dimensional (3D) visualization of the behavior of cells in their natural environment. Traditionally, the 3D images are acquired from 2D image stacks with focusing depth controlled through mechanical movement of the specimen relative to the objective lens. The slow mechanical movement (~<20Hz) does not allow the spot of light to be scanned axially sufficiently fast to monitor cell:cell and cell:environment interactions in real time over hundreds of microns in all three dimensions. A fast focus control mirror supports agile scan patterns such as vertical or oblique planes or even arbitrary surfaces, minimizing the time and photo damage required to monitor features of interest within the 3D volume. Because aberrations cause image quality to decrease as the focal point of the beam penetrates deeper into the sample, adaptive optics can enhance resolution and contrast at depth for confocal microscopy and TPM. Combining a fast focus control mirror with a fast aberration correcting mirror leads to a flexible platform called the active/adaptive laser scanning microscope, capable of aberration-corrected beam scanning throughout a 3D volume of tissue. This opens up the possibility of fully corrected, variable-depth imaging along oblique sections or more complex user-defined surfaces within a single image frame.Item Phase gradient averaging for holographic aperture LIDAR in the presence of turbulence(Montana State University - Bozeman, College of Engineering, 2017) Blaszczyk, Christopher Ross; Chairperson, Graduate Committee: Joseph A. ShawThe resolution of an image is dictated by the size and quality of the imaging system. The imaging system has a physical limit to the resolution dictated by the diffraction limited resolution. This limit can be improved by making the aperture larger on the imaging system. The increase in the physical aperture size can only be practical to a certain extent. However, to get beyond these physical constraints it is possible to use synthetic aperture methods to allow for the aperture to appear to be increased. Synthetic apertures are created by adding apertures coherently together to create a larger aperture that increases the diffraction limited resolution. To sum the aperture coherently the phase information needs to be available. One way to have access to the phase information is to capture the image as hologram. These holograms are captured by using a coherent light source with a reference beam to create an interference pattern that contains the phase information of the target. Holographic apertures can be used in a synthetic aperture method called Holographic Aperture Lidar (HAL). A problem that can arise while capturing images is turbulence in the atmosphere. Turbulence is a change in the index of refraction caused by a change in the temperature and pressure of the atmosphere. This causes the phase of the light to distort dynamically as it propagates making HAL imaging difficult. This thesis will cover a method to restore the original phase of the signal that has passed through turbulence so that it can be used in digital holography and HAL. This method uses averaging of the phase gradient to remove the dynamic turbulence and keep the phase information of the static target. The improvements observed in actual experiments were small, but the basics of the method worked, and the reason for only small improvement are discussed.Item Imaging performance of elliptical-boundary varifocal mirrors in active optical systems(Montana State University - Bozeman, College of Engineering, 2015) Lukes, Sarah Jane; Chairperson, Graduate Committee: David L. DickensheetsMicro-electro-mechanical systems deformable-membrane mirrors provide a means of focus control and attendant spherical aberration correction for miniaturized imaging systems. The technology has greatly advanced in the last decade, thereby extending their focal range capabilities. This dissertation describes a novel SU-8 2002 silicon-on-insulator wafer deformable mirror. A 4.000 mm x 5.657 mm mirror for 45° incident light rays achieves 22 micron stroke or 65 diopters, limited by snapdown. The mirrors show excellent optical quality while flat. Most have peak-to-valley difference of less than 150 nm and root-mean-square less than 25 nm. The process proves simple, only requiring a silicon-on-insulator wafer, SU-8 2002, and a metal layer. Xenon difluoride etches the silicon to release the mirrors. Greater than 90% of the devices survive fabrication and release. While current literature includes several aberration analyses on static mirrors, analyses that incorporate the dynamic nature of these mirrors do not exist. Optical designers may have a choice between deformable mirrors and other types of varifocal mirrors or lenses. Furthermore, a dynamic mirror at an incidence angle other than normal may be desired due to space limitations or for higher throughput (normal incidence requires a beam splitter). This dissertation presents an analysis based on the characteristic function of the system. It provides 2nd and 3rd order aberration coefficients in terms of dynamic focus range and base ray incidence angle. These afford an understanding of the significance of different types of aberrations. Root-mean-square and Strehl calculations provide insight into overall imaging performance for various conditions. I present general guidelines for maximum incidence angle and field of fiew that provide near diffraction-limited performance. Experimental verification of the MEMS mirrors at 5° and 45° incidence angles validates the analytical results. A Blu-ray optical pick-up imaging demonstration shows the utility of these mirrors for focus control and spherical aberration correction. Imaging results of the first demonstration of a deformable mirror for dynamic agile focus control and spherical aberration correction in a commercial table-top confocal microscope are also shown.Item Large-stroke deformable MEMS mirror for focus control(Montana State University - Bozeman, College of Engineering, 2013) Moghimi, Seyyed Mohammad Javad; Chairperson, Graduate Committee: David L. DickensheetsWe developed a novel large-stroke deformable mirror for focus control and spherical aberration correction. The mirrors fabricated using MEMS technology provide full range (150-200 microns in tissue) of focus scanning at high numerical aperture (N.A.=0.5-0.7) for confocal microscopy and optical coherence tomography (OCT). In addition to large stroke, low power consumption and high speed operation are other key factors of the developed devices. The impact of this project is broad since the miniaturized deformable mirrors have a wide range of applications. In addition to focus scanning in microscopes they can also be used in small form factor systems such as cell phone cameras and robot vision. Furthermore, laser based microscopes equipped with the focus control mirror may be useful for skin cancer diagnosis and treatment. This thesis consists of seven chapters. The first chapter introduces optical focus control and focus control elements. The second chapter describes different schemes for optical focus control in imaging systems including transmissive variable lenses. The principle of operation, fabrication, and characterization of electrostatic deformable mirrors are reviewed in Chapter 3. High-speed focus control mirrors with controlled air damping are discussed in Chapter 4. In this chapter a model adopted from the analysis of MEMS microphone is used to design the backplate of a MEMS deformable mirror. Moreover, electrostatic-pneumatic MEMS deformable mirrors are introduced in Chapter 5. Analytical model is developed for electrostatic-pneumatic actuation in order to design a MEMS mirror with two membranes. Applications of MEMS deformable mirrors are demonstrated in optical systems in Chapter 6. Finally, a summary and future work are discussed in Chapter 7. The fabrication process details are given in Appendix A.Item Multi-spectral imaging of vegetation for CO 2 leak detection(Montana State University - Bozeman, College of Engineering, 2011) Hogan, Justin Allan; Chairperson, Graduate Committee: Joseph A. ShawThough its status as a crisis situation remains the subject of much debate [1,2] there does exist evidence that global warming is a real phenomenon [3] and that its processes are to some degree enhanced by anthropogenically introduced greenhouse gases, perhaps most notably carbon dioxide (CO 2) [3]. This claim is backed by observations of increasing atmospheric CO 2 concentrations from nearly 280-ppm around 1750 to 360 ppm in 1995 [4]. By the end of 2010, this number was up to approximately 390 ppm [5]. To reduce human influence on the global environment, carbon capture and sequestration (CCS) is proposed as a means of collecting CO 2 generated through industrial and consumer processes and sequestering it so as not to release it into the atmosphere, thereby reducing atmospheric concentrations of the gas. Suggested methods of sequestration include direct deep-sea injection [6], soil sequestration through improved land use and management practices [7], and geological carbon sequestration in which captured carbon is injected into underground geological features. This research focuses primarily on development and testing of a leak detection technology for deployment to geological sequestration sites. A diverse technology portfolio will be required to implement safe and efficient sequestration solutions [8]. Included in this portfolio is technology capable of monitoring sequestration site integrity; detecting and signaling leakage, should it occur. Early leak detection is paramount to ensuring on-site safety and to minimize, or at least understand, potentially harmful environmental leak effects.Item Surface micro-machined SU-8 2002 deformable membrane mirrors(Montana State University - Bozeman, College of Engineering, 2011) Lukes, Sarah Jane; Chairperson, Graduate Committee: David L. DickensheetsImaging systems are continually decreasing in size, especially in applications such as microscopy and cell phone cameras. Much research is being done to increase focus control capabilities of these instruments. This paper describes a wet-etch release and a dry-etch release fabrication technique for SU-8 2002 surface micro-machined deformable mirrors for focus control and compensation of focus-induced spherical aberration. Producing a good quality SU-8 2002 membrane layer proved difficult and a detailed discussion of the recipe development is presented. A thorough review of both release processes is also included. The dry-etch release process has high yield and realizes larger mirrors with greater than a two-fold improvement in stroke, relative to the wet-etch release. This paper presents deflection vs. voltage plots, mechanical frequency response measurements, surface roughness and flatness, and intrinsic stress for the 750 micron - 4.24 mm nominal dimension circular and elliptical boundary membrane mirrors. The use of a 3 mm x 4.24 mm elliptical boundary mirror for 45° incidence focus control in microscopy is also demonstrated. The intrinsic stress of the film indicates that devices of similar size should be capable of 30 micron displacement in the future. This would allow for sufficient focus control in high NA microscopy applications, while the mirror or mechanism for such control could fit into an endoscopic sized imaging system.