Real-time determination of laser beam quality by modal decomposition

We present a real-time method to determine the beam propagation ratio M2 of laser beams. The all-optical measurement of modal amplitudes yields M2 parameters conform to the ISO standard method. The experimental technique is simple and fast, which allows to investigate laser beams under conditions inaccessible to other methods.Comment: 8 pages, 4 figures, published in Optics Expres

Fundamental limitations on Earth-like planet detection with Extremely Large Telescopes

We analyse the fundamental limitations for the detection of extraterrestrial planets with Extremely Large Telescopes. For this task, a coronagraphic device combined to a very high order wavefront correction system is required but not sufficient to achieve the $10^{-10}$ contrast level needed for detecting an Earth-like planet. The stellar residuals left uncorrected by the wavefront correction system need to be calibrated and subtracted. In this paper, we consider a general model including the dynamic phase aberrations downstream the wavefront correction system, the static phase aberrations of the instrument and some differential aberrations provided by the calibration unit. A rather optimistic case of a filled circular pupil and of a perfect coronagraph is elsewhere assumed. As a result of the analytical study, the limitation mostly comes from the static aberrations. Using numerical simulations we confirm this result and evaluate the requirements in terms of phase aberrations to detect Earth-like planets on Extremely Large Telescopes.Comment: 8 pages, 8 figures, accepted in A&

Artifical compound eyes - Different concepts and their application to ultra flat image acquisition sensors

Two different approaches for ultra flat image acquisition sensors on the basis of artificial compound eyes are examined. In apposition optics the image reconstruction is based on moiré- or static sampling while the superposition eye approach produces an overall image. Both types of sensors are compared with respect to theoretical limitations of resolution, sensitivity and system thickness. Explicit design rules are given. A paraxial 3×3 matrix formalism is used to describe the arrangement of three microlens arrays with different pitches to find first order parameters of artificial superposition eyes. The model is validated by analysis of the system with raytracing software. Measurements of focal length of anamorphic reflow lenses, which are key components of the superposition approach, under oblique incidence are performed. For the second approach, the artificial apposition eye, a first demonstrator system is presented. The monolithic device consists of a UV-replicated reflow microlens array on a thin silica-substrate with a pinhole array in a metal layer on the backside. The pitch of the pinholes differs from the lens array pitch to enable an individual viewing angle for each channel. Imaged test patterns are presented and measurements of the angular sensitivity function are compared to calculations using commercial raytracing software

International round-robin experiment for angle-resolved light scattering measurement

International audienc

OIC 2010 measurement problem

The Measurement Problem comprises the determination of the reflectance R of highreflective dielectric laser mirrors at 1064 nm, AOI 0°

An image restoration approach for artificial compound eyes

Natural compound eyes combine a small eye volume with a large field of view (FOV) at the cost of comparatively low spatial resolution. Based on these principles, an artificial apposition compound-eye imaging system has been developed. In this system the total FOV is given by the number of channels along one axis multiplied with the sampling angle between channels. In order to increase the image resolution for a fixed FOV the sampling angle is made small. However, depending on the size of the acceptance angle, the FOVs of adjacent channels overlap which causes a reduction of contrast in the overall image. In this work we study the feasibility of using digital post-processing methods for images obtained with a thin compound-eye camera to overcome this reduction in contrast. We chose the Wiener filter for the post-processing and carried out simulations and experimental measurements to verify its use

Parallelized multichannel BSDF measurements

The intensity of scattered light is extremely sensitive to even small changes of illumination wavelength, incident angle, polarization states, or even the measurement position. To obtain light scattering distributions with varied parameters, time-consuming sequential measurement procedures are typically employed. Here, we propose a concept for the measurement of multiple properties at the same time. This is achieved by tailoring orthogonal frequency division multiplexing (OFDM) for light scattering measurement techniques to the required low interchannel crosstalk performance. The concept is used for a highly-robust roughness and contamination characterization, to derive one-shot roughness information, as well as to characterize color and appearance

New Experimental Tool For Enhanced Fiber Mode Analysis

S2 imaging and CFT mode analysis are combined and simultaneously performed. This unique tool provides fully resolved modal fields and accurate mode coefficients for a wide range of mode mixtures guided in an optical fiber. © OSA 2013

Bildsensor

DE 102007045525 A1 UPAB: 20090428 NOVELTY - The sensor (1') has image sensor units e.g. opto-electronic and/or digital units, with light-sensitive surfaces e.g. photodiode, in an array-like arrangement, where centers of the surfaces are junctions spaced to each other and span a two-dimensional network with horizontal and vertical connecting lines (12, 13). Distance between two junctions of the arrangement along one of the lines is different in a center region (5) and in a boundary region (6), and/or distance to the other line from the center region to the boundary region is changed such that the network forms a non-equidistant grid. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following: (1) a camera system comprises an image sensor (2) a method for production of an image sensor. USE - Image sensor for use in a camera system i a portable telecommunication equipment, a scanner, a camera, an image detection equipment, terrestrial and star sensors, a satellite sensor, space flight equipments, a monitoring sensor for monitoring individual parts of an industrial system, a robotic sensor arrangement in microrobot, and a medical sensor arrangement (all claimed) as a vision aid in human eye and in a micro endoscope. ADVANTAGE - The distance between two junctions of the arrangement along one of the lines is different in the center region and in the boundary region, and/or the distance to the other line from the center region to the boundary region is changed such that the network forms a non-equidistant lattice, thus mutually avoiding restrictive aberration e.g. geometrical distortion, in the sensor. The utilization of the array-like arrangement reduces requirements to computation time and storage of required electronics

Defined wetting properties of optical surfaces

Optical surfaces equipped with specific functional properties have attracted increasing importance over the last decades. In the light of cost reduction, hydrophobic self-cleaning behavior is aspired. On the other side, hydrophilic properties are interesting due to their anti-fog effect. It has become well known that such wetting states are significantly affected by the surface morphology. For optical surfaces, however, this fact poses a problem, as surface roughness can induce light scattering. The generation of optical surfaces with specific wetting properties, hence, requires a profound understanding of the relation between the wetting and the structural surface properties. Thus, our work concentrates on a reliable acquisition of roughness data over a wide spatial frequency range as well as on the comprehensive description of the wetting states, which is needed for the establishment of such correlations. We will present our advanced wetting analysis for nanorough optical surfaces, extended by a vibration-based procedure, which is mainly for understanding and tailoring the wetting behavior of various solid-liquid systems in research and industry. Utilizing the relationships between surface roughness and wetting, it will be demonstrated how different wetting states for hydrophobicity and hydrophilicity can be realized on optical surfaces with minimized scatter losses