This thesis aims to characterize the photopolymer resins designed for the 3D printing of Gradient Refractive Index (GRIN) lenses. This thesis focuses explicitly on preparing UV-curable inks doped with nanoparticles that are custom-synthesized for sophisticated optical applications. Four different ink formulations have been studied, including epoxy-based and PMMA-based, together with two commercial UV-curable resins, which are a combination of acrylates and epoxies. Spectroscopy testing of these inks is conducted to study their optical performance for properties like the transmittance and absorbance over the UV, visible light, and NIR regions. The results show that it is possible to obtain significantly different behavior in the optical properties of materials compared to the inks without nanoparticles, offering a promising pathway for developing GRIN lenses with superior characteristics. This research also reports on some modifications performed on an Elegoo Mars 4 DLP printer to control a projector and the DMD device for arbitrary exposure times, further contributing to the development of high-performance optical devices through additive manufacturing.

PRobe far-Infrared Mission for Astrophysics (PRIMA) is a cryogenically cooled NASA mission aimed at making hyperspectral observations in the far infrared. The Netherlands Institute for Space Research (SRON) will design and manufacture a Linear Variable Filter (LVF) for use within PRIMA’s optics. In the design and manufacture of the LVF it is essential to characterize its optical properties. This is done by scanning a laser beam over the LVF’s surface while at 4.2K within a cryostat by means of a cryogenic positioning system. This research is tasked with designing that cryogenic positioning system; which must be capable of 2 degree-of-freedom planar motion to scan the the 40 × 20 mm surface of the LVF, with steps of 25 µm and an uncertainty in LVF position of ±2.5 µm. Additionally, the mechanism must fit within the cryostat, and must be able to bring the LVF to a position that is out of the laser beam, resulting in a total horizontal range of motion of 57.5mm. Due to the large range of motion, high accuracy requirements, low temperature, and limited available space, off-the-shelf solutions are not viable. A custom, highly integrated, solution must be developed. The far-infrared and cryogenic context requires that heat dissipation is kept to a minimum, and has consequences for the applicability
of standard components such as ball bearings.

The design process begins with divergent concept generation. Through the course of two downselects, concepts of lesser promise are eliminated. The final concept consists of a 5-bar mechanism with a parallelogram to constrain the rotation of the LVF. It is driven by two stepper motors. Through the use of a MATLAB model, the lengths of the links that define the mechanism are optimized. A Monte Carlo tolerance analysis is performed to calculate the expected performance of the manufactured mechanism. Lastly, the theoretical mechanism is materialized as a CAD model.

The final design of the mechanism is capable of scanning the 40 × 20 mm surface of the LVF with steps of 25 µm or smaller; meeting the target requirement. The worst-case position uncertainty of of the LVF is approximately ±5 µm; twice larger than the target requirement. The estimated heat dissipation is twice the targeted requirement, at 19.4 mW. The detent torque of the recommended stepper motor-gearbox combination provides a safety factor of 12.6 over the maximum torque required by the mechanism.

Linear Variable Filters (LVFs) are integral to future space missions aimed at measuring the spectral features of distant galaxies. Given the varying red-shifts (shift of light to longer wavelengths as an object moves away from the observer) of these galaxies, an LVF with a resolving power of approximately 10 can effectively identify, classify, and image large populations of galaxies, facilitating studies of cosmic evolution through hyperspectral imaging (HSI) techniques. HSI captures detailed spectral information across a wide range of wavelengths for each pixel in an image, enabling material identification and analysis. Since the galaxies to be studied are very faint, hyperspectral imagers need to be equipped with highly sensitive detectors, cryogenically cooled conditions, and filters with high transmission efficiency. This thesis investigates LVFs based on thin membranes, focusing on materials like silicon nitride (Si3N4) and silicon carbide (SiC). The primary objective is to model these thin and pre-stressed membranes using COMSOL Multiphysics to simulate the thermal expansion and mechanical behaviour of membranes in cryogenic environments. Experimental validation is conducted using Digital Holography Microscopy (DHM) and Laser Doppler Vibrometry (LDV) to ensure the accuracy and consistency of the simulations. The model enables the simulation of membranes with varying dimensions, improving the accuracy of behavioural predictions thereby eliminating the need for physical prototypes for analytical purposes, significantly reducing cost and time. Overall, this research bridges the gap between theoretical models and practical applications of LVFs in space. Enhancing the understanding of material behaviour under extreme conditions advances the development of reliable LVFs for spaceborne optical instruments, offering valuable insights into their durability and performance.

A significant focus of current and next-generation astronomical research is the study of exoplanets and the formation of habitable conditions in planetary systems. This requires high-performance spectrom- eters operating in the far-infrared (FIR) range, with the Fabry-Pérot etalon being the state-of-the-art solution. This thesis, a collaboration between TU Delft and the Netherlands Institute for Space Research (SRON), focused on identifying and overcoming the major performance limitations of the Fabry-Pérot. The performance metrics were spectral resolving power and transmission. The major performance lim- itation was identified to be diffraction, which is particularly relevant in the FIR range. A two-part model was developed based on Gaussian beam propagation and the Huygens-Fresnel principle. Gaus- sian beam propagation is a well-established method that takes diffraction effects into account but is limited to the paraxial approximation, which quickly breaks down in the FIR. The novel application of the Huygens-Fresnel principle to Fabry-Pérot propagation modeling accounts for diffraction effects and remains accurate with large beam divergence caused by diffraction. The Gaussian beam approach was used to validate initial results from the Huygens-Fresnel approach. The effect of diffraction on critical device dimensions, such as cavity length, beam waist, finite aperture, and mirror tilt was investigated. Additionally, an experiment design was proposed to further validate the model. This included research into the design of metal mesh mirrors and silicon-air distributed Bragg reflector mirrors using COMSOL and MATLAB simulations. The successful results of the Huygens-Fresnel model provide new insights into the constraints on critical dimensions of the Fabry-Pérot etalon due to diffraction effects. These insights can be used to propose high-performance Fabry-Pérots designs suitable for the exploration of exoplanets.

Protoplanetary disks (PPDs) have gained substantial attention due to their crucial role in planet formation. Observing their features in the far-infrared (FIR) spectrum has been challenging due to limitations in current optics and detectors, with proposed missions requiring a spectrometer with a spectral resolving power on the order of magnitude of 100,000. A promising solution is the virtually imaged phased array (VIPA), which could surpass the commonly used Fabry-Perot etalon and diffraction grating spectrometers. However, due to their novelty, VIPAs have seen limited applications in space and lack a numerically efficient model, preventing confi- dent recommendation for FIR spectroscopy. In this project, a one-dimensional (1D) analytical VIPA model with a numerically efficient implementation using Gaussian beam formalism was developed, showing close alignment with an advanced 2D model by Hu et al. (2015) based on the angular spectrum of plane waves. The new model demonstrated potential for VIPAs to meet the spectral resolving power required for space missions and showed the possibility to be further expanded to 2D for higher accuracy, while retaining high efficiency. An experimental setup for verifying the simulation results was proposed. The interplay between various device parameters, coupled with the numerous degrees of freedom required for aligning the optical setup, presented significant experimental challenges. Additionally, investigations into the design of inductive metal mesh mir- rors, supported by simulations in COMSOL and MATLAB, uncovered several difficulties that were thoroughly explored. The analytical VIPA model based on Gaussian beam propagation shows promise as a method for optimizing a VIPA for high-resolution far-infrared spectroscopy but further research and experimental validation are necessary to fully establish its efficiency and effectiveness. The project was a collaboration between TU Delft and the Netherlands Institute for Space Research (SRON).

This study presents a novel approach for evaluating the effects of dynamic disturbances on optical performance using sensitivity analysis. The computation of optical performance for perturbed optical systems is too costly with state-of-the-art analysis software when applied in the use case for the optimization of the optomechanical interface, and therefore using a simplified model, based on ray transfer matrices, describing the most critical phenomena provides a solution. The proposed analytical framework employs a Taylor expansion for the merit function, incorporating both the Jacobian and Hessian matrices, to reduce computation time in transient analysis. The effect of small perturbations on the merit function is found to be accurately described by the approximation when solely the Jacobian is included, for larger displacement fields the approximation deviates significantly without the inclusion of the Hessian. Next to this, the definition of a grating matrix is appended to the framework to facilitate the analysis of a larger set of systems. For transient analysis, the proposed framework exhibits a remarkable improvement in computation time, with minimal degradation in accuracy for paraxial systems. All findings hold relevance for the effect of rigid body displacements in coupled mechanical-optical analyses and further optimization of this coupling under disturbed conditions.

Adaptive optics (AO) are essential in ground-based telescopes to correct atmospheric distortions and achieve high-resolution imaging; adaptive secondary mirrors (ASMs) integrate deformable mirrors directly into telescope optics but typically require a wavefront sensor (WFS) for calibration and flattening. When a WFS is unavailable or nonfunctional, alternative methods are needed. This thesis explores the feasibility of flattening the convex ASM of the UH-88 telescope without a WFS, using only a natural guide star and focal plane imaging. By developing a numerical model of the UH-88 system—including the deformable mirror, Mauna Kea atmospheric aberrations, and focal plane camera characteristics—we employed an image metric based on the second moment of intensity to evaluate image quality, adjusting Zernike mode coefficients via the Nelder-Mead simplex optimization algorithm to control mirror shape. Experimental validation using a laboratory setup that replicated key aspects of the UH-88 system confirmed that the ASM could be flattened to within 100 nm RMS surface error, meeting passive mirror operation requirements. The flattening was achieved within a 10-minute timeframe using only focal plane images of a natural guide star distorted by atmospheric turbulence. This study demonstrates that flattening a convex ASM without a WFS is feasible using focal plane image metric optimization, offering a practical solution when the WFS is unavailable or calibrated commands are outdated, thereby ensuring continued high-quality telescope operation.

Cerebral oxygen saturation is an important indicator that reflects the oxygen metabolism of the brain tissues in such patients. The utilization of near-infrared spectroscopy (NIRS) enables the identification of the oxygen saturation levels in nearby tissues by analyzing the distinct oxygenation states of hemoglobin-oxyhemoglobin (HbO2) and the distinctive molecular spectrum of deoxygenated hemoglobin (Hb). It is helpful to realize the objective of noninvasive continuous detection on cerebral oxygen saturation because near-infrared radiation can directly penetrate the skull to obtain the characteristics of the average oxygen saturation of the brain tissues. This also allows a noninvasive way to monitor blood flow in the brain. A frequency comb is a pulsed laser in the time domain and a sequence of discrete, uniformly spaced frequency lines in the frequency domain. Applying the frequency comb to NIRS has the potential to develop a high-speed and fs-level time-of-flight resolution blood flow measurement system. The objective of this thesis is to utilize a chip-based optical frequency comb as an illuminating source in order to conduct time-of-flight measurements of a single target, employing a Michelson interference experiment. The establishment of the time of flight in the single-layer case and the investigation of the non-ambiguity range form the fundamental basis for future experiments multi-layer.

The investigation of the interaction between lasers and brain tissue holds significant theoretical and practical significance in the field of brain physiology studies. A two-dimensional finite element-based simulation model was constructed using the commercial finite element simulation software COMSOL Multiphysics to investigate the propagation of light and photon correlation in tissues. The simulations included static and dynamic conditions of light propagation in tissue. In both cases this diffuse light propagation itself was studied along with photon correlation using the solution of the diffusion equation. Subsequently, the obtained simulation results are assessed and summarized by considering the outcomes of data fitting. The findings indicate that the accuracy of simulating light propagation is higher for larger sizes, although satisfactory results can be achieved for correlation propagation simulations in the small size range. The simulation results remain unaffected by the refinement of the mesh, provided that the fundamental criteria for mesh size are satisfied.

This work delves into designing and implementing an optimized self-centering lens mounting technique for the collimator and coupler lenses in the Universal Light Source (ULS) by ASML. The ULS aims to meet the growing demand for smaller logic nodes and higher throughput in optical metrology sensors. To achieve precise alignment and stability, the light source utilizes a supercontinuum spectral shaping method based on a highly non-linear hollow core anti-resonance photonic crystal fiber filled with a high-pressure noble gas.
This research identifies the limitations of the existing lens mounting design in terms of manufacturing, stability, and adhesive usage. To address these challenges, a self-centering design is proposed, leveraging the geometrical relationship between thread angle, barrel and retaining ring diameters, and lens clearance. By optimizing these parameters, the centering error is substantially reduced, demonstrating a considerable improvement in centering precision compared to the current method. Additionally, thermal effects are mitigated through a symmetrical design and local flexibility, reducing the impact of temperature fluctuations during operation and transportation.
An analytical assessment of five different collimator and coupler lens mount concepts are presented to identify an optimal design meeting specific operating temperature, stresses, eigenfrequency, and manufacturability criteria. Numerical analysis is employed to evaluate the performance of each design concept relative to the currently employed mounting designs.
The resulting optimized self-centering coupler and collimator lens mount exhibits centering errors influenced by various tolerances. These tolerances have a deviation of ±0.2% for the lens radial surface, ±1° for the thread angle, and ±0.2 mm for the remaining parameters. The calculated centering errors for coupler lens and collimator lens 1 and 2 are 6.27 μm, 8.24 μm, and 6.98 μm, respectively. However, it is crucial to acknowledge that these results are purely theoretical and necessitate validation through experimental data to ascertain their accuracy.
Overall, this optimized self-centering technique offers enhanced stability, relaxed manufacturing tolerances, and eliminates the need for adhesives when compared to the current flexure design. These significant findings contribute to the advancement of optomechanical engineering and provide valuable insights into the implementation of self-centering mounts, thereby enhancing precision while relaxing manufacturing requirements in optomechanical mounting.

There is a growing demand for precision and high-quality optical objectives and lenses due to their numerous advantages and uses. The market for high precision objective lenses has tremendous potential for development and is a sector that is expanding quickly.

Measuring the aberrations of optical systems is an essential step in the fabrication of high precision optical components. However, when working at the cutting-edge of technology, it is increasingly difficult to provide trustworthy measurements as the used metrology instrument has to be of comparable or higher precision. This poses a major problem especially when working with high numerical aperture (NA) optics.

In this thesis, we will analyze and quantify the measurement uncertainty of a Twyman-Green interferometer used for lens testing of high-NA microscope objectives.

To quantify the measurement uncertainty of the interferometer, various sources of uncertainty that affect the accuracy and precision of the measurements are considered. These include environmental and instrumentation factors such as incorrect phase-stepping, laser instability, camera noise, stray light, photon shot noise, effects of mid-spatial frequencies originating in the optical reference, as well as computational shortcomings such as: incorrect phase unwrapping, polynomial fit errors, incorrect pupil scaling and edge detection.

By carefully analyzing these individual sources of uncertainty and their impact, we determine the overall measurement uncertainty of the interferometer and provide an assessment of its accuracy through Monte Carlo simulations, where the introduced uncertainties are obtained from real measurement data. The uncertainty analysis procedure described in this paper is a useful tool that can also be applied to different types of interferometers by taking proper considerations into account.

Acoustic levitation is an novel method that could lend itself very useful to fast and precise transportation of small objects. To verify the acoustic field and the modelling assumptions, the acoustic field must be visualised and quantified. Different methods to visualise a pressure gradient are investigated and rated against design requirements. These requirements are: 1. difficulty, as the setup should be buildable within the period of a MSc. thesis. 2. Time per measurement and 3. measurement sensitivity. It is decided that using a double coincidence spherical mirror schlieren setup is most suitable measurement method. To capture the high speed sphenomena of ultrasound acoustic waves in air, the schlieren light source is pulsed and matched to the frequency of the acoustics to ’freeze’ the acoustic wave in the air. Parameters that influence the schlieren image are identified and studied. These parameters are duty cycle, cut-off, ISO, light source phase delay and light source frequency. A horizontal cut-off is determined as the best, while it is determined that the other parameters can be adjusted dependent on the acoustic field. The acoustic field generated by double phased array is observed. Trap locations and types can be identified using the schlieren system. Quantification of the schlieren images has been attempted but without satisfactory results, mainly due to an interesting observation regarding a correlation between the camera focus distance and the pressure gradient. The schlieren system is a useful research tool and successful at visualising
the pressure gradient under the assumption that it is constant over the optical axis. Further research is needed to for quantification and to assess the impact of the observation.

inPhocal, a startup company specialized in laser marking, developed a novel optical module to make the depth of focus more than 50mm, and wants to replace ink marking by this laser marking system in the production line when marking information on products. Distortion will always happen when marking 2D patterns onto 3D objects with laser, so deforming the 2D patterns beforehand to make marked pattern keep its shape is necessary. This process is called shape correction. Nowadays, the way to do this shape correction is very complicated and time- consuming. This thesis is focused on providing a new method that can do shape correction easily and fast. In this research, Non-Uniform Rational B-Spline (NURBS) is used in reconstructing the 3D surfaces and the shape correction will be based on these NURBS surfaces. With this NURBS-based shape correction, the pattern can be mapped on to 3D object fast without distortion.

Flatness is an important surface tolerance requirement during the manufacturing of a part of an ASML machine. Flatness can be measured by either measuring the variation in height of the surface in one measurement (a plane-wise measurement) or by measuring the height on multiple xy-coordinates on this surface (point-wise measurement). Point-wise distance measurement sensors tend to have small physical dimensions, while having good specifications on resolution perpendicular to the measured surface. During a separate research, a gap is found in performing a point-wise flatness measurement while accounting for undesired stage deviations. The stage deviations are in the order of
micrometers, while the sensor accuracy is in the order of nanometers. The performance of a point-wise flatness measurement is therefore in a negative sense dominated by the stage inaccuracies rather than sensor performance. During this research the gap is filled by designing, building and testing a feasibility demonstrator which uses reference sensors to account for stage inaccuracies. By performing a live correction with either 1 or 3 reference sensors, the stage inaccuracy (in z, Rx and Ry) can be compensated for. The measured stage wobble for this specific setup is 3.2 µm, which is reduced to 0.13 µm when using three reference sensors. The method of using reference sensors for flatness measurements is shown to work, mainly when using 3 reference sensors.

Single photon detectors are an important optical sensing tool in many industries. However, these highly efficient detectors suffer from variations in the size of an optical cavity when cooling down to 3K. An active positioning system is therefore required to correct the relative position of the fibre to the detector, so an optimal and reproducible cavity size can be achieved, thereby maximizing their efficiency. The literature study performed on cryogenic precision actuators showed that a stepper motor in combination with a motion reduction mechanism is the most feasible design. A stepper motor and a precision screw were two fundamental components of the preliminary design, so their lubrication was removed and were proven to work cryogenically. The rest of the design was based around these fundamental components. Room temperature tests were done to show the functionality of the design and it showed a positioning resolution between 10 nm and 30nm with just a 100nm loss of motion when unloading and loading the system. Cryogenic tests achieved similar results and it showed that the reflected power of a detector was reduced from 8.8% to 3.6%, indicating that the maximum achievable detector efficiency increased from 91.2% to 96.4%.

Lithography machines that manufacture integrated circuits require non-contact and nanometer-scale position measurement, which is led by displacement laser interferometer in some ASML machines. The aim of the project is to design a displacement interferometer using non-polarizing light to meet the requirements and be cost-effective. The design is challenging considering the requirements of 350 mm measurement range, 300 µrad angular range and less than 1 nm periodical non-linearity (PNL) error.

This thesis analyzes all the design requirements first. To fulfill the requirements, efficient design strategies are clarified, and the phase detection method is determined.

Three interferometer designs are investigated and developed in this thesis. The design concepts are collected from ASML internal references. Mathematical models are built to represent the optics and trace the light in each interferometer. Optimization tools are developed to solve and tune the parameters that fulfill all the dimension-related requirements. Geometrical optics simulations are performed to verify the mathematical models and the optimization results. The source and behavior of PNL error in each interferometer are carefully researched. In a design with lenses, sequential mode simulations are performed to calculate the wavefront error. Further calculations based on the wavefront error indicate this interferometer design is not feasible.

Based on the theoretical analysis two interferometer designs can fulfill all the requirements. These two interferometers are built in the cleanroom with off-the-shelf parts to validate the working principle and PNL errors. The optics, optomechanics and electronics used in the tests are explained. The methods of alignment and measurement are introduced. The working principles of the two interferometers are validated, and the behaviors of PNL error match the theoretical analysis.

Future industrial lithography machines will use interferometers for wafer-stage position metrology. Interferometers suffer from phase wrapping, which is why in this thesis an absolute phase detection system has been developed. The absolute phase detection system will use two lasers, with the second laser allowing for limited changes in the wavelength. An efficient implementation of the excess fractions method has been developed to perform the absolute phase capture. To improve the longevity of the system the second laser should ideally be allowed to turn of when not used for absolute phase capture, which requires a wavelength estimation algorithm. Such a wavelength estimation algorithm has been implemented, and it can also provide an initial estimate for the OPD of the interferometer to be used in the excess fraction method. Both the excess fractions method and the wavelength estimation method have been experimentally verified. The results were satisfactory, thus providing all the building block for an absolute phase capture system.

This work investigates low-cost three-dimensional (3D) ultrasound reconstruction from a two-dimensional (2D) hand-held probe with motion tracking. The best available motion tracking is an optical tracking system, which is expensive and requires external tracking hardware. Here, a low-cost manoeuvrable motion tracker, an inertial measurement unit (IMU) sensor, has been tested by comparing it with an optical tracking system. The motion of the probe has been divided into a rotation and translation movement. Comparing the IMU sensor rotation tracking with the optical tracking, while rotating 40 degrees, resulted in an average Pearson’s correlation of 0.99 ± 0.0056. The average Pearson’s correlation between the translation tracking of the IMU sensor and the optical tracking system, in a translation of 15 centimetres, was 0.13 ± 0.78. The rotation and translation tracking is used to reconstruct the ultrasound volume of a phantom. In a rocking motion reconstructed volume the horizontal distance between phantom features had a mean error of 45%, a vertical distance was reconstructed with a mean error of 0.25%. In a translation motion reconstructed volume these errors were 29% and 1.4% for respectively horizontal feature distance and vertical feature distance. This study demonstrates that an IMU sensor can be used to track the motion of the probe. The rotation tracking of the IMU sensor is comparable with the rotation tracking of an optical tracking system. The translation tracking of the IMU sensor is on average not comparable with an optical tracking system, however some translations have been tracked with a high correlation. A reason to explain the low average correlation of the translation tracking of the IMU sensor is the method of gravity vector correction in the accelerometer data. Future research should focus on the clinical evaluation of the rotation tracking and the development of an accurate translation tracking method by studying the initial gravity vector or looking at different translation tracking methods.

Use of earth observation satellites have grown at a very high rate over the past few decades. On a closer observation of things around, most of them uses satellites, directly or indirectly. Satellites are being used in the day-to-day life without being aware of its application. Satellites are used for small things like weather report, communication to very large things like internet of things (IOT) and earth observation. Some CubeSats are also used for interplanetary missions. For the purpose of earth observation missions, the satellites are installed with an optical payload which is a camera. The cameras used for space are different from the regular camera and have special specifications in terms of the materials, components and the design which make them suitable for space missions. The optical payload which is to be launched has to be made sure that it can survive the launch and in orbit environment. This research focuses on the testing of these CubeSats and check if they are suitable for launch. The research starts with reviewing the testing procedure that is followed before the satellite is launched. A setup is provided for checking the performance of the camera mounted on the CubeSat and its suitability for launch. To investigate the performance of the camera, MTF and correlation techniques are used on different images to come to a conclusion.