SignificanceScanning laser optical tomography (SLOT) is a volumetric multi-modal imaging technique that is comparable to optical projection tomography and computer tomography. Image quality is crucially dependent on matching the refractive indexes (RIs) of the sample and surrounding medium, but RI matching often requires some effort and is never perfect.AimReducing the burden of RI matching between the immersion medium and sample in biomedical imaging is a challenging and interesting task. We aim at implementing a post processing strategy for correcting SLOT measurements that have errors caused by RI mismatch.ApproachTo better understand the problems with poorly matched Ris, simulated SLOT measurements with imperfect RI matching of the sample and medium are performed and presented here. A method to correct distorted measurements was developed and is presented and evaluated. This method is then applied to a sample containing fluorescent polystyrene beads and a sample made of olydimethylsiloxane with embedded fluorescent nanoparticles.ResultsFrom the simulations, it is evident that measurements with an RI mismatch larger than 0.02 and no correction yield considerably worse results compared to perfectly matched measurements. RI mismatches larger than 0.05 make it almost impossible to resolve finer details and structures. By contrast, the simulations imply that a measurement with an RI mismatch of up to 0.1 can still yield reasonable results if the presented correction method is applied. The experiments validate the simulated results for an RI mismatch of about 0.09.ConclusionsThe method significantly improves the SLOT image quality for samples with imperfectly matched Ris. Although the absolutely best imaging quality will be achieved with perfect RI matching, these results pave the way for imaging in SLOT with RI mismatches while maintaining high image quality.
Refractive index matching is typically achieved with combinations of silicone oils in Scanning Laser Optical Tomography. This leads to destruction of some types of samples such as silicone waveguides. A correction method was developed which allows image acquisition with high quality without perfectly matching the refractive index of medium and sample. This enables the use of water as the immersion medium instead of silicone oil. Promising results with high image quality are presented.
LiDAR technology plays a vital role in various applications, including autonomous driving, environmental monitoring, and robotics. Accurate target detection is a crucial task in LiDAR systems to ensure the precise identification of objects and obstacles. However, the absence of clear standards for LiDAR system design parameters poses challenges in determining the optical system configurations. This paper focuses on a procedure that determines the necessary resolutions in LiDAR systems, with a specific emphasis on target detection algorithms. The investigation methodology encompassed the steps involved in scenario generation, capturing LiDAR point cloud data, and evaluating the obtained LiDAR data. Multiple widely-used algorithms are selected to represent diverse approaches to object detection. The paper concludes by summarizing the derived angular resolution requirements for each algorithm. By incorporating these findings, developers can optimize LiDAR system configurations to meet the specific demands of their application domains, ultimately enhancing the performance and reliability of LiDAR applications.
While most of the efforts in the development of vehicle headlamps are focused on the design of high-resolution visible beam distributions, recent research shows the possibilities of using a near-infrared auxiliary headlamp for machine vision. Contrary to previous non-imaging approaches not designed to attenuate parts of the beam, this feature can supplement missing light during low-beam driving. This paper aims to evaluate various emitters and optical concepts for an auxiliary near-infrared headlamp, with particular emphasis on etendue and power density. Firstly, the system requirements for an automotive headlamp consisting of a visible and near-infrared source are discussed. Secondly, we evaluate differnent design approaches to the optical system with focus on the near-infrared subsystem. Consequently, the optomechatronical system is discussed, looking at optics, electronics and mechanics seperately.
Additive Manufacturing (AM) to produce parts of optical systems is gaining popularity due to design flexibility and functional integration. However, one of the significant challenges in the field of AM for optical systems is the limited manufacturing accuracy compared to traditional manufacturing methods. This causes an increase in manufacturing and assembly errors, which affects the fit and function of the produced parts and therefore the performance of the optical system. This work aims to reduce the negative impact of manufacturing and assembly errors on optical performance, as exemplified in practice by additively manufacturing housings and lens mounts for a Raman spectroscopy system. For this, the simulated optical system of a Raman spectrometer is used to perform the optical tolerance analysis, such as identifying critical components and sensitivity analysis. The Manufacturability of additive manufacturing is then evaluated by measuring printed standard specimens. According to optical and mechanical tolerance analysis, design and manufacturing problems can be found. Then the structure is optimized using the design flexibility provided by additive manufacturing, and accumulated errors from assembly and manufacturing are reduced by minimizing the number of installed components. Measuring the intensity of the Raman signal revealed that the improved design reduced the accumulated errors in the mechanical structure. In addition, the signal-to-noise ratio is significantly enhanced by 265 % compared to the non-optimized design. Hence, this design optimization based on tolerance analysis is an effective methodology for enhancing the performance of additively manufactured optical systems from the perspective of AM technology development in optical domain.
Additive Manufacturing of glass opens up new possibilities for the design and integration of optical components. By varying the shape and size of optical elements, optical systems specifically adapted to various applications can be fabricated cost-effectively. The Laser Glass Deposition (LGD) process uses a CO2 laser with a wavelength of 10.6 μm to locally generate temperatures above 2000 °C in fused silica fibers. This enables the Additive Manufacturing and Rapid Prototyping of glass by melting and then layer-by-layer deposition of fibers. However, these high temperatures can result in very high residual stress in the material. The development of a coaxial LGD process aims for a more uniform heating of the glass fiber during the printing process in order to enable a direction-independent process and to reduce the residual stresses within the printed components. In this work, a novel concept for the coaxial LGD process and its successful experimental application is presented. Further, a numerical simulation model is developed to describe the temperature distribution in the glass fiber during the coaxial LGD process. Based on experimental results and on the numerical simulation, the potentials and challenges of the coaxial LGD process are discussed.
Due to their exibility, highly transparent silicone materials offer potentials for the development of adjustable optics. Previously realized mechanisms for changing the focal length of a solid silicone lens applied discrete points of force to mechanically deform the geometry. This article describes an approach to adjust the focal length of silicone lenses quickly and precisely. The chosen approach aims for a minimal number of moving components to provide reliability and reduced complexity. A contactless and stepless adjustment is realized by using electromagnetic control. To determine the functionality of the lens, the tunable range of the focal length will be investigated.
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