A novel athermal approach for high-performance cryogenic metal optics

This paper describes a new athermal approach for high performance metal optics, particularly with regard to extreme environmental conditions as they usually may occur in terrestrial as well as in space applications. Whereas for mid infrared applications diamond turned aluminium is the preferred mirror substrate, it is insufficient for the visual range. For applications at near infrared wavelengths (0.8 μm - 2.4 μm) as well as at on cryogenic temperatures (-200°C) requirements exist, which are only partially met for diamond turned substrates. In this context athermal concepts such as optical surfaces with high shape accuracy and small surface micro-roughness without diffraction effect and marginal loss of stray light, are of enormous interest. The novel, patented material combination matches the Coefficient of Thermal Expansion (CTE) of an aluminium alloy with high silicon content (AlSi, Si >= 40 %) as mirror substrate with the CTE of the electroless nickel plating (NiP). Besides the harmonization of the CTE (~ 13 * 10-6 K-1), considerable advantages are achieved due to the high specific stiffness of these materials. Hence, this alloy also fulfils an additional requirement: it is ideal for the manufacturing of very stable light weight metal mirrors. To achieve minimal form deviations occurring due to the bimetallic effect, a detailed knowledge of the thermal expansion behavior of both, the substrate and the NiP layer is essential. The paper describes the reduction of the bimetallic bending by the use of expansion controlled aluminium-silicon alloys and NiP as a polishing layer. The acquisition of CTE-measurement data, the finite elements simulations of light weight mirrors as well as planned interferometrical experiments under cryogenic conditions are pointed out. The use of the new athermal approach is described exemplary

Manufacturing of a precision 3D microlens array on a steep curved substrate by injection molding process

In this study, a high volume low cost manufacturing method for microoptical microlens arrays on steep curved substrates using a microinjection molding technique was investigated. The design of the individual lenslets was performed using ZEMAX. This 3D microlens array in this study contains 1219 microlenses that are evenly distributed on its concave surface with a high fill factor. The overall field of view of this microlens array on curved substrates is more than 104°. To complete the manufacturing process, first the mold inserts were machined using a voice coil based fast tool servo technique, then the 3D microlens arrays were injection molded. The injection molding process parameters were evaluated using both experiments and numerical simulation for best molding results. In addition, both geometrical errors and optical performance tests showed that the molded polymer microlens arrays can be used in wide angle imaging applications. This study demonstrated that this combined process is capable of fabricating high precision microlens arrays at steep curved substrates at low cost. The microlens arrays created in this study have broad applications in optical, medical and biomedical domains. The success of this study provided a feasible solution for mass production of 3D microlens arrays on arbitrary substrates

Development of a low cost high precision three-layer 3D artificial compound eye

Artificial compound eyes are typically designed on planar substrates due to the limits of current imaging devices and available manufacturing processes. In this study, a high precision, low cost, three-layer 3D artificial compound eye consisting of a 3D microlens array, a freeform lens array, and a field lens array was constructed to mimic an apposition compound eye on a curved substrate. The freeform microlens array was manufactured on a curved substrate to alter incident light beams and steer their respective images onto a flat image plane. The optical design was performed using ZEMAX. The optical simulation shows that the artificial compound eye can form multiple images with aberrations below 11 μm; adequate for many imaging applications. Both the freeform lens array and the field lens array were manufactured using microinjection molding process to reduce cost. Aluminum mold inserts were diamond machined by the slow tool servo method. The performance of the compound eye was tested using a home-built optical setup. The images captured demonstrate that the proposed structures can successfully steer images from a curved surface onto a planar photoreceptor. Experimental results show that the compound eye in this research has a field of view of 87°. In addition, images formed by multiple channels were found to be evenly distributed on the flat photoreceptor. Additionally, overlapping views of the adjacent channels allow higher resolution images to be re-constructed from multiple 3D images taken simultaneously

Nomograms for morbidity and mortality after oncologic colon resection in the enhanced recovery era: results from a multicentric prospective national study

Purpose: Predicting postoperative complications and mortality is important to plan the surgical strategy. Different scores have been proposed before to predict them but none of them have been yet implemented into the routine clinical practice because their difficulties and low accuracy with new surgical strategies and enhanced recovery. The main aim of this study is to identify risk factors for postoperative morbidity and mortality after colonic resection (CR) without protective stomas, in order to develop a comprehensive, up-to-date, simple, reliable, and applicable model for the preoperative assessment of patients with colon cancer. Methods: Multivariable analysis was performed to identify risk factors for 60-day morbidity and mortality. Coefficients derived from the regression model were used in the nomograms to predict morbidity and mortality. Results: Three thousand one hundred ninety-three patients from 52 hospitals were included into the analysis. Sixty-day postoperative complications rate was 28.3% and the mortality rate was 3%. In multivariable analysis the independent risk factors for postoperative complications were age, male gender, liver and pulmonary diseases, obesity, preoperative albumin, anticoagulant treatment, open surgery, intraoperative complications, and urgent surgery. Independent risk factors for mortality were age, preoperative albumin anticoagulant treatment, and intraoperative complications. Conclusions: Risk factors for morbidity and mortality after CR for cancer were identified and two easy predictive tools were developed. Both of them could provide important information for preoperative consultation and surgical planning in the time of enhance recovery