Eduard Reithmeier

Bio: Eduard Reithmeier is an academic researcher from Leibniz University of Hanover. The author has contributed to research in topics: Structured-light 3D scanner & Projector. The author has an hindex of 15, co-authored 209 publications receiving 1039 citations. Previous affiliations of Eduard Reithmeier include National Metallurgical Academy of Ukraine & University of California, Berkeley.

Robust vibration control of dynamical systems based on the derivative of the state

Abstract: Vibrations may be undesirable in dynamical systems for several reasons. They may affect the security, such as vibrations in primary cycle parts of (nuclear) power plants. They may decrease the quality and functionality of products, such as those manufactured by machine tools. And they may lower the comfort, such as vibrations in car wheel suspension systems or in power trains of cars. One possibility to attenuate these vibrations is by employing active suspension elements. Mounted at appropriate places inside the systems or with respect to their environment, they are able to interchange or dissipate kinetic and potential energy in an effective way with moderate control effort. Their effectiveness depends greatly on the control scheme applied to change damping and stiffness characteristics of the suspension elements. The control schemes, however, very often need information on the state variables involved in the mathematical modeling. On the other hand, it is mostly the acceleration or speed of certain parts that can be sensed reasonably and measured with sufficient accuracy. We propose here a control scheme which is solely based on the derivative of the state variables, provided that active suspension elements or actuators with the above-mentioned properties may be employed within the system. Furthermore, we only use control actions within a discrete set of possible values, which aids the real-time implementation of the designed control algorithms. And, last but not least, the number of control inputs (actuators) may be arbitrary, that is, the system may be mismatched. The scheme is based on the Lyapunov stability theory, which involves discontinuities of the Lyapunov function candidates along trajectories of the state derivative. The effectiveness and behavior of the control scheme is demonstrated on a two-DOF model of an active car seat suspension in order to enhance the driving comfort.

Flexible, fast, and low-cost production process for polymer based diffractive optics.

Abstract: The generation of diffractive optical elements often requires time and cost consuming production techniques such as photolithography. Especially in research and development, small series of diffractive microstructures are needed and flexible and cost effective fabrication techniques are desirable to enable the fabrication of versatile optical elements on a short time scale. In this work, we introduce a novel process chain for fabrication of diffractive optical elements in various polymers. It is based on a maskless lithography process step, where a computer generated image of the optical element is projected via a digital mirror device and a microscope setup onto a silicon wafer coated with photosensitive resist. In addition, a stitching process allows us to microstructure a large area on the wafer. After development, a soft stamp of the microstructure is made from Polydimethylsiloxane, which is used as a mold for the subsequent hot embossing process, where the final diffractive optical element is replicated into thermoplastic polymer. Experimental results are presented, which demonstrate the applicability of the process.

Low-Cost Fabrication of All-Polymer Components for Integrated Photonics

Abstract: For various applications such as optical communication, sensor technology, and optical interconnects, microoptical polymer devices show great promise. Especially, straight and bent optical waveguides as well as beam splitters represent the building blocks of these devices. In this paper, we introduce a novel combination of simple fabrication techniques and cost-efficient polymer materials for the fabrication of planar polymer optical waveguides. We present a low-cost fabrication process through hot embossing and doctor blading techniques and investigate the use of UV curing printing ink and optical adhesive as waveguide core materials with an emphasis on economical fabrication and low optical losses in the near infrared and the visible range of the light spectrum. The refractive indices, the propagation losses and the bend losses of the fabricated waveguides are characterized. We demonstrate propagation losses as low as 0.09 and 0.74 dB/cm for wavelength of 850 and 633 nm, respectively. Furthermore, we investigate the crosstalk between adjacent waveguides as a function of the distance separating them and present an application of the presented fabrication technique in the form of beam splitters. We also investigate beam splitters having spliting ratios of 1:2, 1:4, and 1:8 and demonstrate excess losses per branching region of down to 0.11 dB and high output uniformity. All these experimental values represent important benchmarks, which demonstrate the capability of the presented method to be used for the design of more complex polymer photonic devices.

Hot Embossing of Polymer Optical Waveguides for Sensing Applications

Abstract: Micro-optical sensors integrated into polymer foils hold great promise for a wide range of applications. One major challenge to date is the reliable, large-scale and cost-effective manufacturing of the required waveguide structures. Several techniques are currently investigated in the field, hot-embossing being particularly promising. In this work, we discuss hot embossing of polymer optical waveguides. We present our recent results in the area of stamp manufacturing and waveguide fabrication. For the characterization of the waveguides, the refractive index, the transmission losses and the beam profile of the coupled light are measured. We also describe next steps towards more advanced waveguides.

Cladded self-written multimode step-index waveguides using a one-polymer approach

Abstract: Low-loss optical-coupling structures are highly relevant for applications in fields as diverse as information and communication technologies, integrated circuits, or flexible and highly-functional polymer sensor networks. For this suitable and reliable production methods are crucial. Self-written waveguides are an interesting solution. In this work, we present a simple and efficient one-polymer approach for self-written optical connections between light-guiding structures such as single-mode and multi-mode optical fibers or waveguides that relies on self focusing of the light inside a photopolymerizing mixture. The optical connections are produced in a two-step process by writing into monomer resin using cw laser light in the blue wavelength range and subsequent UV curing. Since only one photopolymerizing resin is required, we reduced the fabrication complexity compared to previous approaches to obtain a waveguide embedded in a rigid cladding material. We discuss the production method, the results obtained as function of relevant process parameters such as writing speed or curing time, and evaluate optical properties and coupling efficiencies.

A reflectance model for computer graphics

Abstract: This paper presents a new reflectance model for rendering computer synthesized images. The model accounts for the relative brightness of different materials and light sources in the same scene. It describes the directional distribution of the reflected light and a color shift that occurs as the reflectance changes with incidence angle. The paper presents a method for obtaining the spectral energy distribution of the light reflected from an object made of a specific real material and discusses a procedure for accurately reproducing the color associated with the spectral energy distribution. The model is applied to the simulation of a metal and a plastic.

Progress in optics

Abstract: Have you ever felt that the very title, Progress in Optics, conjured an image in your mind? Don’t you see a row of handsomely printed books, bearing the editorial stamp of one of the most brilliant members of the optics community, and chronicling the field of optics since the invention of the laser? If so, you are certain to move the bookend to make room for Volume 16, the latest of this series. It contains seven chapters on widely diverging topics, written by well-known authorities in their fields. These are: 1) Laser Selective Photophysics and Photochemistry by V. S. Letokhov, 2) Recent Advances in Phase Profiles (sic) Generation by J. J. Clair and C. I. Abitbol, 3 ) Computer-Generated Holograms: Techniques and Applications by W.-H. Lee, 4) Speckle Interferometry by A. E. Ennos, 5 ) Deformation Invariant, Space-Variant Optical Pattern Recognition by D. Casasent and D. Psaltis, 6) Light Emission from High-Current Surface-Spark Discharges by R. E. Beverly, and 7) Semiclassical Radiation Theory within a QuantumMechanical Framework by I. R. Senitzkt. The breadth of topic matter spanned by these chapters makes it impossible, for this reviewer at least, to pass judgement on the comprehensiveness, relevance, and completeness of every chapter. With an editorial board as prominent as that of Progress in Optics, however, it seems hardly likely that such comments should be necessary. It should certainly be possible to take the authority of each author as credible. The only remaining judgment to be made on these chapters is their readability. In short, what are they like to read? The first sentence of the first chapter greets the eye with an obvious typographical error: “The creation of coherent laser light source, that have tunable radiation, opened the . . . .” Two pages later we find: “When two types of atoms or molecules of different isotopic composition ( A and B ) have even one spectral line that does not overlap with others, it is pos-