Correction of the fringe order errors for fringe projection profilometry

Non-contact three-dimensional (abbreviated as 3D) Fringe projection profilometry (abbreviated as FPP) counts as a method of reconstructing the shape of object surface. This technique has been extensively used in many areas, e.g. computer vision, biomedical research, industrial applications, and virtual reality. Using a FPP, sinusoidal patterns are projected on the object surface by mean of a digital projector, and subsequently a camera captures the reflected patterns deformed by the object surface. As the shape information of the object surface is carried by the deformed patterns, the 3D profile can be retrieved through analysing these patterns. The phase unwrapping is a primary issue bound by the existing phase unwrapping techniques in FPP, aiming to recover the absolute phase from wrapped phase. The temporal phase unwrapping with multi-frequency fringe pattern was proposed, prominently advantaged by none-error propagation. Furthermore, the fringe order is deemed as the critical property to retrieve the absolute phase

Micro Fourier Transform Profilometry (μ\muFTP): 3D shape measurement at 10,000 frames per second

Recent advances in imaging sensors and digital light projection technology have facilitated a rapid progress in 3D optical sensing, enabling 3D surfaces of complex-shaped objects to be captured with improved resolution and accuracy. However, due to the large number of projection patterns required for phase recovery and disambiguation, the maximum fame rates of current 3D shape measurement techniques are still limited to the range of hundreds of frames per second (fps). Here, we demonstrate a new 3D dynamic imaging technique, Micro Fourier Transform Profilometry ($\mu$FTP), which can capture 3D surfaces of transient events at up to 10,000 fps based on our newly developed high-speed fringe projection system. Compared with existing techniques, $\mu$FTP has the prominent advantage of recovering an accurate, unambiguous, and dense 3D point cloud with only two projected patterns. Furthermore, the phase information is encoded within a single high-frequency fringe image, thereby allowing motion-artifact-free reconstruction of transient events with temporal resolution of 50 microseconds. To show $\mu$FTP's broad utility, we use it to reconstruct 3D videos of 4 transient scenes: vibrating cantilevers, rotating fan blades, bullet fired from a toy gun, and balloon's explosion triggered by a flying dart, which were previously difficult or even unable to be captured with conventional approaches.Comment: This manuscript was originally submitted on 30th January 1

Universal Phase Unwrapping for Phase Measuring Profilometry Using Geometry Analysis

Traditionally temporal phase unwrapping for phase measuring profilometry needs to employ the phase computed from unit-frequency patterned images; however, it has recently been reported that two phases with co-prime frequencies can be absolutely unwrapped each other. However, a manually man-made look-up table for two known frequencies has to be used for correctly unwrapping phases. If two co-prime frequencies are changed, the look-up table has to be manually rebuilt. In this paper, a universal phase unwrapping algorithm is proposed to unwrap phase flexibly and automatically. The basis of the proposed algorithm is converting a signal-processing problem into a geometric analysis one. First, we normalize two wrapped phases such that they are of the same needed slope. Second, by using the modular operation, we unify the integer-valued difference of the two normalized phases over each wrapping interval. Third, by analyzing the properties of the uniform difference mathematically, we can automatically build a look-up table to record the corresponding correct orders for all wrapping intervals. Even if the frequencies are changed, the look-up table will be automatically updated for the latest involved frequencies. Finally, with the order information stored in the look-up table, the wrapped phases can be correctly unwrapped. Both simulations and experimental results verify the correctness of the proposed algorithm

Interferometric observations of hot stars

Accurate determination of fundamental stellar properties is crucial in understanding and testing models of stellar structure and evolution. To date, most stars with independent determinations of stellar properties based on high-resolution observations by optical interferometers belong to stars of type F5 or later, and most of measurements for early type stars come almost exclusively from the seminal observations with the Narrabri Stellar Intensity Interferometer (NSII) 50 years ago. Additionally, stellar rotation, generally overlooked in standard stellar models for decades, can play a central role for early-type stars, given their frequent high rotation rates. In this case, determination of fundamental stellar properties requires accurate diameter estimates at a range of position angles, and a more detailed modelling of the stellar surface. Recent development of 2D stellar models including a self-consistent rotation description (incorporating differential rotation) in stars with radiative envelopes has provided a method to describe the effects of rotation that links them to fundamental properties,based on a small set of parameters determining the stellar structure (mass,composition,rotation). In this thesis I have determined fundamental stellar properties for 14 new stars with spectral types earlier than F6. For 10 of them, the effects of stellar rotation may be neglected, whereas the other 4 exhibit fast rotation. In order to derive stellar parameters for these stars, I have incorporated state-of-the-art 2D models into a code capable of generating a model synthesizing all observables into a robust and self-consistent framework. Using interferometry,star distances,photometry and spectroscopy in the ultraviolet,visible and infrared, the derived fundamental stellar parameters, together with rotation dependent evolutionary tracks,are used to determine mass and age of the stars,corrected for the bias induced by the star rotation axis orientation

Probing Power-Absorbing Structures at Near-Infrared Wavelengths using Energy Absorption Interferometry

Energy Absorption Interferometry was recently proposed as an interferometric technique capable of fully characterizing the optical response of single-mode, few-mode and multi- mode power-absorbing structures, such as near-infrared detectors. A detector’s output can be written as the full spatial contraction of the external field correlation tensor and detector response correlation tensor representing their respective spatial coherence states; EAI recovers the latter, solely using power measurements. EAI is essentially a generalization of holography, and allows the reconstruction of the individual degrees of freedom through which the device under test can absorb energy, including their relative sensitivities and spatial forms. The natural modes of the detector response are intimately related to its optical coupling mechanisms and the underlying solid-state phenomena responsible for power absorption: their study therefore has direct applications in improving current infrared detector technology. In particular, device properties dependent on its geometry and material are directly obtained, such as the absorber’s spatial coherence length. EAI yields an experimental procedure where the system under test is excited with two external coherent sources, and the fringe in the total power dissipated is measured as the relative phase between the sources is varied. Iterating for multiple source positions, the fringes’ complex amplitudes allow the two-point detector response function to be retrieved: this correlation function can then be decomposed into a set of natural modes. In this thesis, we demonstrate the application of EAI at near-infrared wavelengths. We describe the theoretical basis of EAI and numerically investigate its feasibility at infrared wavelengths. We present for the first time the design of a room-temperature, fiber-based, 1550 nm-wavelength experiment and its performance. We report the first measurement of the complex-valued DRF of fiber-coupled photodetectors, with single-mode, few-mode and multi-mode behaviors; this includes extending the experimental system to suppress environmental phase drift in optical fibers. We recover the natural modes of the devices under test, and compare their spatial forms to numerical simulations. Finally, we discuss the application of EAI to many-body structures as varied as spin systems and energy-harvesting absorbers, and its extension to measure quantum correlation functions using a pair of probes creating generalized forces

COMPRESSIVE IMAGING AND DUAL MOIRE´ LASER INTERFEROMETER AS METROLOGY TOOLS

Metrology is the science of measurement and deals with measuring different physical aspects of objects. In this research the focus has been on two basic problems that metrologists encounter. The first problem is the trade-off between the range of measurement and the corresponding resolution; measurement of physical parameters of a large object or scene accompanies by losing detailed information about small regions of the object. Indeed, instruments and techniques that perform coarse measurements are different from those that make fine measurements. This problem persists in the field of surface metrology, which deals with accurate measurement and detailed analysis of surfaces. For example, laser interferometry is used for fine measurement (in nanometer scale) while to measure the form of in object, which lies in the field of coarse measurement, a different technique like moire technique is used. We introduced a new technique to combine measurement from instruments with better resolution and smaller measurement range with those with coarser resolution and larger measurement range. We first measure the form of the object with coarse measurement techniques and then make some fine measurement for features in regions of interest. The second problem is the measurement conditions that lead to difficulties in measurement. These conditions include low light condition, large range of intensity variation, hyperspectral measurement, etc. Under low light condition there is not enough light for detector to detect light from object, which results in poor measurements. Large range of intensity variation results in a measurement with some saturated regions on the camera as well as some dark regions. We use compressive sampling based imaging systems to address these problems. Single pixel compressive imaging uses a single detector instead of array of detectors and reconstructs a complete image after several measurements. In this research we examined compressive imaging for different applications including low light imaging, high dynamic range imaging and hyperspectral imaging

The Primordial Inflation Explorer (PIXIE)

The Primordial Inflation Explorer is an Explorer-class mission to open new windows on the early universe through measurements of the polarization and absolute frequency spectrum of the cosmic microwave background. PIXIE will measure the gravitational-wave signature of primordial inflation through its distinctive imprint in linear polarization, and characterize the thermal history of the universe through precision measurements of distortions in the blackbody spectrum. PIXIE uses an innovative optical design to achieve background-limited sensitivity in 400 spectral channels spanning over 7 octaves in frequency from 30 GHz to 6 THz (1 cm to 50 micron wavelength). Multi-moded non-imaging optics feed a polarizing Fourier Transform Spectrometer to produce a set of interference fringes, proportional to the difference spectrum between orthogonal linear polarizations from the two input beams. Multiple levels of symmetry and signal modulation combine to reduce systematic errors to negligible levels. PIXIE will map the full sky in Stokes I, Q, and U parameters with angular resolution 2.6 degrees and sensitivity 70 nK per 1degree square pixel. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r < 10(exp. -3) at 5 standard deviations. The PIXIE mission complements anticipated ground-based polarization measurements such as CMBS4, providing a cosmic-variance-limited determination of the large-scale E-mode signal to measure the optical depth, constrain models of reionization, and provide a firm detection of the neutrino mass (the last unknown parameter in the Standard Model of particle physics). In addition, PIXIE will measure the absolute frequency spectrum to characterize deviations from a blackbody with sensitivity 3 orders of magnitude beyond the seminal COBE/FIRAS limits. The sky cannot be black at this level; the expected results will constrain physical processes ranging from inflation to the nature of the first stars and the physical conditions within the interstellar medium of the Galaxy. We describe the PIXIE instrument and mission architecture required to measure the CMB to the limits imposed by astrophysical foregrounds

Cassini atmospheric chemistry mapper. Volume 1. Investigation and technical plan

The Cassini Atmospheric Chemistry Mapper (ACM) enables a broad range of atmospheric science investigations for Saturn and Titan by providing high spectral and spatial resolution mapping and occultation capabilities at 3 and 5 microns. ACM can directly address the major atmospheric science objectives for Saturn and for Titan, as defined by the Announcement of Opportunity, with pivotal diagnostic measurements not accessible to any other proposed Cassini instrument. ACM determines mixing ratios for atmospheric molecules from spectral line profiles for an important and extensive volume of the atmosphere of Saturn (and Jupiter). Spatial and vertical profiles of disequilibrium species abundances define Saturn's deep atmosphere, its chemistry, and its vertical transport phenomena. ACM spectral maps provide a unique means to interpret atmospheric conditions in the deep (approximately 1000 bar) atmosphere of Saturn. Deep chemistry and vertical transport is inferred from the vertical and horizontal distribution of a series of disequilibrium species. Solar occultations provide a method to bridge the altitude range in Saturn's (and Titan's) atmosphere that is not accessible to radio science, thermal infrared, and UV spectroscopy with temperature measurements to plus or minus 2K from the analysis of molecular line ratios and to attain an high sensitivity for low-abundance chemical species in the very large column densities that may be achieved during occultations for Saturn. For Titan, ACM solar occultations yield very well resolved (1/6 scale height) vertical mixing ratios column abundances for atmospheric molecular constituents. Occultations also provide for detecting abundant species very high in the upper atmosphere, while at greater depths, detecting the isotopes of C and O, constraining the production mechanisms, and/or sources for the above species. ACM measures the vertical and horizontal distribution of aerosols via their opacity at 3 microns and, particularly, at 5 microns. ACM recovers spatially-resolved atmospheric temperatures in Titan's troposphere via 3- and 5-microns spectral transitions. Together, the mixing ratio profiles and the aerosol distributions are utilized to investigate the photochemistry of the stratosphere and consequent formation processes for aerosols. Finally, ring opacities, observed during solar occultations and in reflected sunlight, provide a measurement of the particle size and distribution of ring material. ACM will be the first high spectral resolution mapping spectrometer on an outer planet mission for atmospheric studies while retaining a high resolution spatial mapping capability. ACM, thus, opens an entirely new range of orbital scientific studies of the origin, physio-chemical evolution and structure of the Saturn and Titan atmospheres. ACM provides high angular resolution spectral maps, viewing nadir and near-limb thermal radiation and reflected sunlight; sounds planetary limbs, spatially resolving vertical profiles to several atmospheric scale heights; and measures solar occultations, mapping both atmospheres and rings. ACM's high spectral and spatial resolution mapping capability is achieved with a simplified Fourier Transform spectrometer with a no-moving parts, physically compact design. ACM's simplicity guarantees an inherent stability essential for reliable performance throughout the lengthy Cassini Orbiter mission