The scientific community recognizes the critical role played by ptychography in nanoscale imaging. Compared with the conventional imaging, which has high requirements on the manufacturing of optical elements, ptychography, as a computational imaging technique, uses a set of measured intensities of the diffraction patterns to reconstruct the image of the object and hence no imaging system is needed. This technique is especially useful in the short wavelength, e.g. EUV, regime, where manufacturing high quality optical elements such as mirrors is extremely expensive.

Most of the present ptychographic algorithms require the illumination of the object to be both spatially and temporally coherent so that the diffraction pattern can be interpreted as the intensity of the Fourier transform of the field exiting the object. However, the coherence of the sources that produce the EUV radiation often cannot be guaranteed. Therefore, it is crucial to extend the ptychography method to consider partial coherence effects. This requires the use of a flexible propagator which depends on the wavelength to deal with the temporal partial coherence and a modal representation for the spatially partially coherent field. Also, the ambiguity of the reconstructed modes of the probe will be solved by an orthogonalization approach, which could enhance the reproducibility of the results. These methods will be implemented on an existing ptychography platform based on automatic-differentiation and will be validated using both simulation data and experimental data. ... Read more

There are strict tolerances on the placement of optical components in high performance optical systems. Compliant alignment mechanisms can be used to meet these tolerances. Conventional manufacturing techniques, such as milling and spark erosion, have been used to produce an extensive library of alignment solutions but are limited in the geometries they can produce. Metal 3D printing (SLM) is a newer manufacturing method that can produce complex geometries in a large design space with unique limitations but has no extensive library of solutions. A design method is proposed to construct building blocks for concept generation as a foundation for this library. The method aims at achieving this by reducing the size of the solution space, dividing it into separate constraint combinations. These constraint combinations and tools to develop them into building blocks are presented as tables with geometries and a flowchart describing their use. The design method is demonstrated by applying it towards the development of a compact, low-mass mechanism with three independent alignment stages. FEM analysis and a prototype in Ti6Al4V are used to explore some of the properties and manufacturability of this demonstration case. ... Read more

With climate change being a prime source of concern around the world, air pollution is a topic that requires special attention. Therefore, it is of utmost importance to track and measure the emissions in our environment for detecting the sources and understating the climate change so as to figure out possible solutions. Despite ongoing development, the current LEO and GEO satellite instruments have a long prolonged global survey, revealing the pollution trends at a broad scale, but there is still a lack of high-resolution data to pinpoint pollution sources.

For this, John Hopkins University (Applied physics lab) and NASA are now developing a new earth atmospheric monitoring mission called Compact Hyperspectral Air Pollution Sensor (CHAPS) to address it at a local scale. Presently, TNO is carrying out the design study for this system by employing both freeform optics and additive manufactured mechanics. The mission objective is to perform targeted local measurements of the atmosphere on a daily basis by providing high spatial and temporal resolution possible in UV-VIS wavelength range.

In order to characterize, quantify, and monitor emissions from urban areas, power plants, and other anthropogenic activities, it is important to collect accurate and precise data and calibrate the optical instrument. But the data often received from the sensor is not reliable due to the operational and the non-operational conditions leading to cross-sensitivity, change in the trajectory, and optomechanical errors. For this, an on-board calibration system is developed to perform continuous calibration of the science product, that is compatible with both the instrument and the satellite platform and is robust to the variable operating conditions. This requires a stable system that achieves a good performance that is insensitive to thermal and mechanical disturbances, in order to meet the strict specifications.

As opposed to conventional methods, additive manufacturing, enables new possibilities for developing Optomechanical structures because of the layer-wise manufacturing technique. This manufacturing process is widely touted as a foundation for the next industrial revolution as it offers profound advantages like shorter lead time, lower wastage of materials, and higher geometric complexity that can be useful for multi-functional and multi-material structures. It can also facilitate good strength, significant mass reduction, and better dimensional homogeneity and stability. At the same time, additive manufacturing is not an easy process and requires new design strategies and solutions for overcoming the existing constraints.

The prime research objective is to investigate the optomechanical design of the spectral calibration module applying a kinematic approach. The second research objective is to investigate design and the potential improvements when applying additive manufacturing. The present case study demonstrates and evaluates the preliminary phase of the calibration module design study, thus providing the key ingredients for the realisation of the full system. ... Read more

In aerial manipulation, Unmanned Aerial Vehicles (UAVs) are equipped with manipulators to perform a variety of tasks such as inspections of critical infrastructure at heights. A fundamental issue is that the shaking forces and moments of the manipulator cause the UAV to tip-over and become unstable. Control based methods have been applied in which the UAV provided a compensation force or moment at the propellers. However, the dynamic model required was too complex to compute on-board in real time and simplifications led to poor performance. This thesis resolves the issue of shaking forces and moments by creating a new manipulator using inherent dynamic balancing principles. The advantage of these principles is that the manipulator architecture achieves both functions of supporting and positioning the end effector as well as balancing. This helps to reduce the weight of the manipulator. The result of the synthesis work is a manipulator which is reactionless, lightweight, has 3 degrees of freedom, and is compatible with a UAV. First a manipulator is designed using inherently force balanced architectures. Next, active moment balancing is developed through a novel control scheme. Finally, a simulation is performed to prove the dynamic balancing and control method. It shows the manipulator is reactionless. However, the control scheme’s tracking still needs improvement. This work is useful to enable UAVs with manipulators to perform a variety of tasks such as inspections of surfaces at height. ... Read more