Confocal fluorescence microscopy with high-NA diffractive lens arrays.

Traditionally, there is a trade-off between the numerical aperture and field of view for a microscope objective. Diffractive lens arrays (DLAs) with overlapping apertures are used to overcome such a problem. A spot array with an NA up to 0.83 and a pitch of 75 µm is produced by the proposed DLA at a wavelength of 488 nm. By measurement of the fluorescence beads, the DLA-based confocal setup shows the capability of high-resolution measurement over an area of 3mm×3mm with a 2.5×0.07NA objective. Further, the proposed fluorescence microscope is insensitive to optical aberrations, which has been demonstrated by imaging with a simple doublet lens.

High-resolution confocal microscopy with low-NA objectives based on diffractive lens arrays.

High resolution and large fields of view are difficult to achieve simultaneously by microscope objectives. In this work, we develop a reflection confocal microscope based on diffractive lens arrays to solve the problem. We demonstrate a prototype that generates a spot array with a numerical aperture of 0.78. Laterally, experiments show a spatial cutoff frequency of 1024 lp/mm by a 0.15 NA objective, and 912 lp/mm by a 0.07 NA objective with a 785 nm diode laser. Axially, an average height of 961 nm with a standard deviation of 49 nm is measured with a 925.5 nm calibrated step height target.

Fraunhofer Institute of Optronics, System Technologies and Image Exploitation: introduction to the focus issue.

This focus issue offers a glimpse into the breadth and depth of research in optics and image processing at the Fraunhofer Institute of Optronics, System Technologies and Image Exploitation (abbreviated Fraunhofer IOSB). The institute belongs to the Fraunhofer Society, which is Europe's largest organization for applied research. The society comprises 72 institutes spread throughout Germany as well as subsidiaries in several European countries, and the USA, UK, Chile and Singapore, each focusing on different fields of applied science. It is named after the Bavarian physicist Joseph von Fraunhofer (1787-1826), the inventor of the spectrometer, optical lens manufacturer and an entrepreneur, who exemplified the goals of the society, i.e.: a focus on research excellence, innovation, and commitment to market and customer-oriented research.

Analytical determination of the complex refractive index and the incident angle of an optically isotropic substrate by ellipsometric parameters and reflectance.

An analytical solution for the determination of both angle of incidence (AOI) and the complex refractive index from combined ellipsometric and reflectometric measurements at optically isotropic substrates is presented. Conventional ellipsometers usually measure flat surfaces because the curvatures of the surface alter the reflected or transmitted light, which causes experimental errors due to the deviation of the incident angle. However, in real industrial applications, the shapes of samples are usually curved or even free-form. In this case, the knowledge of the AOI is essential. The proposed method provides a simple way to measure the AOI and the complex refractive index of nonplanar samples without extra or complicated hardware.

ReS2tAC-UAV-Borne Real-Time SGM Stereo Optimized for Embedded ARM and CUDA Devices.

With the emergence of low-cost robotic systems, such as unmanned aerial vehicle, the importance of embedded high-performance image processing has increased. For a long time, FPGAs were the only processing hardware that were capable of high-performance computing, while at the same time preserving a low power consumption, essential for embedded systems. However, the recently increasing availability of embedded GPU-based systems, such as the NVIDIA Jetson series, comprised of an ARM CPU and a NVIDIA Tegra GPU, allows for massively parallel embedded computing on graphics hardware. With this in mind, we propose an approach for real-time embedded stereo processing on ARM and CUDA-enabled devices, which is based on the popular and widely used Semi-Global Matching algorithm. In this, we propose an optimization of the algorithm for embedded CUDA GPUs, by using massively parallel computing, as well as using the NEON intrinsics to optimize the algorithm for vectorized SIMD processing on embedded ARM CPUs. We have evaluated our approach with different configurations on two public stereo benchmark datasets to demonstrate that they can reach an error rate as low as 3.3%. Furthermore, our experiments show that the fastest configuration of our approach reaches up to 46 FPS on VGA image resolution. Finally, in a use-case specific qualitative evaluation, we have evaluated the power consumption of our approach and deployed it on the DJI Manifold 2-G attached to a DJI Matrix 210v2 RTK unmanned aerial vehicle (UAV), demonstrating its suitability for real-time stereo processing onboard a UAV.

An Extended Modular Processing Pipeline for Event-Based Vision in Automatic Visual Inspection.

Dynamic Vision Sensors differ from conventional cameras in that only intensity changes of individual pixels are perceived and transmitted as an asynchronous stream instead of an entire frame. The technology promises, among other things, high temporal resolution and low latencies and data rates. While such sensors currently enjoy much scientific attention, there are only little publications on practical applications. One field of application that has hardly been considered so far, yet potentially fits well with the sensor principle due to its special properties, is automatic visual inspection. In this paper, we evaluate current state-of-the-art processing algorithms in this new application domain. We further propose an algorithmic approach for the identification of ideal time windows within an event stream for object classification. For the evaluation of our method, we acquire two novel datasets that contain typical visual inspection scenarios, i.e., the inspection of objects on a conveyor belt and during free fall. The success of our algorithmic extension for data processing is demonstrated on the basis of these new datasets by showing that classification accuracy of current algorithms is highly increased. By making our new datasets publicly available, we intend to stimulate further research on application of Dynamic Vision Sensors in machine vision applications.

SmartSpectrometer-Embedded Optical Spectroscopy for Applications in Agriculture and Industry.

The ongoing digitization of industry and agriculture can benefit significantly from optical spectroscopy. In many cases, optical spectroscopy enables the estimation of properties such as substance concentrations and compositions. Spectral data can be acquired and evaluated in real time, and the results can be integrated directly into process and automation units, saving resources and costs. Multivariate data analysis is needed to integrate optical spectrometers as sensors. Therefore, a spectrometer with integrated artificial intelligence (AI) called SmartSpectrometer and its interface is presented. The advantages of the SmartSpectrometer are exemplified by its integration into a harvesting vehicle, where quality is determined by predicting sugar and acid in grapes in the field.

Toward Mass Video Data Analysis: Interactive and Immersive 4D Scene Reconstruction.

The technical progress in the last decades makes photo and video recording devices omnipresent. This change has a significant impact, among others, on police work. It is no longer unusual that a myriad of digital data accumulates after a criminal act, which must be reviewed by criminal investigators to collect evidence or solve the crime. This paper presents the VICTORIA Interactive 4D Scene Reconstruction and Analysis Framework ("ISRA-4D" 1.0), an approach for the visual consolidation of heterogeneous video and image data in a 3D reconstruction of the corresponding environment. First, by reconstructing the environment in which the materials were created, a shared spatial context of all available materials is established. Second, all footage is spatially and temporally registered within this 3D reconstruction. Third, a visualization of the hereby created 4D reconstruction (3D scene + time) is provided, which can be analyzed interactively. Additional information on video and image content is also extracted and displayed and can be analyzed with supporting visualizations. The presented approach facilitates the process of filtering, annotating, analyzing, and getting an overview of large amounts of multimedia material. The framework is evaluated using four case studies which demonstrate its broad applicability. Furthermore, the framework allows the user to immerse themselves in the analysis by entering the scenario in virtual reality. This feature is qualitatively evaluated by means of interviews of criminal investigators and outlines potential benefits such as improved spatial understanding and the initiation of new fields of application.

Programmable light source based on an echellogram of a supercontinuum laser.

Illumination systems with tunable spectrums have been receiving an increasing amount of attention due to their wide application and unique capability. This paper proposes a programmable light source in the visible range based on the combination of a prism and an echelle grating. A supercontinuum laser is utilized as the primary source, whose echellogram is projected to a digital mirror device for wavelength selection. A complete calibration procedure is developed to generate any target spectrum of choice. Experiments have shown that spectral peaks with a full width at half-maximum of 1 nm can be easily generated and the wavelength tuning resolution can reach as small as 0.01 nm.