Improved calibration of vertical scanning optical profilometers for spherical profiles measurements

A new method for calibrating optical scanning profilometers is presented. Especially adapted to spherical and aspherical profile measurements, it shows an increase of accuracy bigger than one order of magnitude for radius of curvature measurements. Calibration of vertical scaling is obtained with a reduction of its uncertainty by a factor larger than 2, which also demonstrates the advantage of this method for any surface measurements. Using commercially available reference balls, this method is easily implementabl

Assessing microlens quality based on 3D irradiance measurement at the focal spot area

During the fabrication process of microlenses, characterization is essential for two purposes: evaluate the optical quality of the element and provide surface information feedback for process optimization. However, no technique can fulfill these two objectives at the same time. Interferometry is used for quality evaluation and optical profilometry for process optimization. In order to address this problem, we propose to use a high resolution interference microscope to characterize microlenses. The focusing capacity can be directly measured by recording the field near the focal spot at different wavelengths. Information about the microlens surface can also be retrieved. All this is illustrated for the front focus of a fused-silica microlens

On the assessment of aspheric refractive microlenses

Refractive microlenses and microlens arrays are key components for many applications such as optical data communication, laser and medical devices, or cameras. In particular, refractive micro-optics enables the miniaturization of high-tech systems but also offers novel optical functionalities. The success of this technology lies in the wafer-level fabrication technique, using the method of photoresist reflow with a subsequent pattern transfer into the substrate by reactive ion etching. Indeed, it allows the manufacturing in parallel of thousands of spherical or aspheric microlenses smaller than 1 mm. Their characterization is usually performed by measuring their surface, as this allows at the same time the evaluation of the microlens performance and feedback for fabrication process optimization. In this thesis, we assess this characterization approach to understand the fabrication process better and to improve the microlenses performance. Concretely, we first study surface form tolerancing, which is crucial to ensure the microlenses quality. However, the link between the surface form of a microlens and its performance is not straightforward, usually resulting in over-restrictive tolerances. Here, we investigate this connection for simple cases and then compare different approaches to tolerance typical micro-optical systems. Practical guidelines are proposed based on the results. Secondly, we present methods to improve surface measurements. For this, we develop an original calibration procedure that takes into account the aberrations of the imaging system. In the presented example, the accuracy is increased by a factor 7, rendering the characterization of diffraction-limited microlenses with high numerical apertures possible. Thirdly, we model the fabrication process to find correlations with the manufactured surface. Thereby, the fabrication optimization is made faster and more accurate. We validate this approach by increasing the uniformity of a large (100mm x 100mm) microlens array by a factor ~3. Finally, we evaluate another microlens characterization that consists of probing the optical functionalities in transmission and compare it to surface measurements. Particularly, we give the reasons for our doubts about its application to wafer-level microlenses. In conclusion, we show that a quantitative analysis of the microlens characterization allows for a significant improvement of the microlens quality and a better understanding of the fabrication process, resulting in lower production cost. For this reason, we believe that the results presented in this thesis will help to render wafer-level refractive micro-optics a more mature technology and build its bright future

An oncogenic Ezh2 mutation induces tumors through global redistribution of histone 3 lysine 27 trimethylation

B-cell lymphoma and melanoma harbor recurrent mutations in the gene encoding the EZH2 histone methyltransferase, but the carcinogenic role of these mutations is unclear. Here we describe a mouse model in which the most common somatic EZH2 gain-of-function mutation (Y646F in human, Y641F in the mouse) can be conditionally expressed. Expression of Ezh2Y641F in mouse B-cells or melanocytes caused high-penetrance lymphoma or melanoma, respectively. Bcl2 overexpression or p53 loss, but not c-Myc overexpression, further accelerated lymphoma progression, and expression of mutant B-Raf but not mutant N-Ras further accelerated melanoma progression. Although expression of Ezh2Y641F increased abundance of global H3K27 trimethylation (H3K27me3), it also caused a widespread redistribution of this repressive mark, including a loss of H3K27me3 associated with increased transcription at many loci. These results suggest that Ezh2Y641F induces lymphoma and melanoma through a vast reorganization of chromatin structure inducing both repression and activation of polycomb-regulated loci