Fraunhofer-Institut für Photonische Mikrosysteme IPMS

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MEMS based fluorescence microscope with 3D option for dermatological applications

2014 , Bechtel, C. , Knobbe, J. , Grüger, H. , Lakner, H.

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Distortion correction of all-reflective unobscured optical-power zoom objective

2010 , Seidl, K. , Knobbe, J. , Schneider, D. , Lakner, H.

We present the correction of distortion for a novel type of an all-reflective zoom objective. The allreflective unobscured optical-power zoom (OPZ) objective with four mirrors has been previously designed and presented. The magnification of the OPZ can be varied by changing the curvatures of the first and the last mirror, which results in a zoom factor of 3. However, the objective exhibits significant distortion. For the unobscured design principle, we present the basic distortion model with its different types of distortion. Based on simulation data of the objective design, we optimized the parameters of the model and verified that model by applying it to images taken with the objective.

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Origin of damages in OLED from Al top electrode deposition by DC magnetron sputtering

2010 , Gil, T.H. , May, C. , Scholz, S. , Franke, S. , Törker, M. , Lakner, H. , Leo, K. , Keller, S.

In this study, we examine organic light emitting diodes (OLEDs) having Al top electrodes deposited on organic layers by direct-current magnetron sputtering. The OLEDs consisted of electronically doped transport layers and phosphorescent emission layer were characterized by typical current-voltage-luminance measurement. They showed higher leakage currents, decreased forward currents, and corresponding increases of driving voltage after the sputter deposition on the organic layers. The OLEDs exhibited randomly distributed bright spots on the active area, and the bright spots were investigated by scanning electron microscopy/energy-dispersive X-ray spectroscopy. In order to prove the origins of sputter damage, simple organic/Al layer samples were made and investigated by ellipsometry and laser-induced desorption/ionization time-of-flight mass spectrometry. The results are compared with previous works addressing the fundamental phenomena of magnetron sputtering. We conclude that the high leakage current originated from a penetration of sputtered metal atoms into the underlying organic layers, and the decrease of forward current resulted from an interface degradation caused by the radiation of plasma, which reduces charge carrier injection preferentially at the Al/organic layer interface.

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Aluminium nitride: A promising and full CMOS compatible piezoelectric material for MOEMS applications

2009 , Conrad, H. , Schmidt, J.U. , Pufe, W. , Zimmer, F. , Sandner, T. , Schenk, H. , Lakner, H.

Aluminum nitride (AlN) is a promising piezoelectric material suitable for full CMOS compatible MEMS processes. Due to the transversal inverse piezoelectric effect the use of AlN enables quasistatic deformable mirrors by actively coupling lateral strain in micro machined membranes. In this work a fast and reliable way for reactive magnetron rf-sputtered aluminum nitride thin films with piezoelectric properties is shown. The thin AlN films were deposited on amorphous TiAl, SiO2 and silicon substrates using an industrial PVD cluster system. The morphologies of the deposited polycrystalline AlN films are characterized by X-ray diffraction measurements and SEM images of the layer surfaces. An enhanced texture coefficient is used to demonstrate the correlation between the X-ray diffraction pattern and the surface topology. High values of this enhanced texture coefficient will guarantee piezoelectric properties. Virtual powder X-ray diffraction experiments are used to determine the relative powder intensities required for texture coefficient evaluation. The transversal inverse piezoelectric coupling coefficient d31 is measured for tempered and untreated aluminum nitride thin films with high enhanced texture coefficients by quasistatic deflected wafer cantilevers.

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Publication

Design of a confocal fluorescence microscope - Space saving and affordable

2012 , Bechtel, C. , Knobbe, J. , Grüger, H. , Lakner, H. , Reichert, F.

Although confocal fluorescence laser scanning microscopy is a widely used technique in biology, these microscopes are at present uncommon in medical diagnostics. However laser scanning fluorescence microscopy is a non-invasive imaging technique that allows depth resolved investigations of skin disorders. High costs and large outline are factors which impede the establishment of this technology in medical practice. To overcome this obstacle, we have designed a portable confocal laser scanning fluorescence microscope and realized an optical demonstration set-up, offering a field of view of 500m x 500m. The microscope is based on a dual axis MEMS mirror where the confocal character of the system resides in the use of the same path for illumination and detection with the rejection of out-of-focus light by a pinhole. Illumination is provided by a laser and the fluorescence light is separated from the illumination light by a filter, before being detected. The ability to perfo rm cross-sectional imaging of fluorescence specimen will be given by an integrated z-shifter.

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Multispectral characterization of diffractive micromirror arrays

2010 , Berndt, D. , Heber, J. , Sinning, S. , Kunze, D. , Knobbe, J. , Schmidt, J.-U. , Bring, M. , Rudloff, D. , Friedrichs, M. , Rössler, J. , Eckert, M. , Kluge, W. , Neumann, H. , Wagner, M. , Lakner, H.

The present article discusses an optical concept for the characterization of diffractive micromirror arrays (MMAs) within an extended wavelength range from the deep ultra-violet up to near-infrared. The task derives from the development of a novel class of MMAs that will support programmable diffractive properties between 240 nm and 800 nm. The article illustrates aspects of the achromatic system design that comprises the reflective beam homogenization with divergence control and coherence management for an appropriate MMA illumination as well as the transfer of phase modulating MMA patterns into intensity profiles for contrast imaging. Contrast measurements and grey scale imaging demonstrate the operation of the characterization system and reflect the encouraging start of technology development for multispectral, diffractive MMAs.

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Eine 'Reinkarnation' in der Strukturmechanik

2009 , Conrad, H. , Sandner, T. , Schenk, H. , Lakner, H.

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Basic angles in microelectromechanical system scanning grating spectrometers

2011 , Pügner, T. , Knobbe, J. , Lakner, H.

Modern miniaturized scanning grating spectrometers (SGSs) are often based on microelectromechanical system devices. In contrast to classical spectrometers, such systems exhibit additional design constraints, like a symmetrical motion of the grating with a limited deflection. A detailed mathematical analysis of typical SGS configurations based on the grating equation considering these constraints is presented. Equations that relate the basic angles on a scanning grating to the grating properties and the attainable wavelength range of a spectrometer are derived, and the solution set is examined. Furthermore, the analytical description can be used to optimize SGSs with symmetrically moving gratings. The attainable spectral range for a given deflection amplitude of the grating can be calculated. Alternatively, the required grating properties can be determined for a given spectral range.

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Publication

Design für ein Zoomobjektiv mit deformierbaren Spiegeln

2010 , Seidl, K. , Knobbe, J. , Lakner, H.

Es wird ein Design für ein Schiefspiegler-Zoomobjektiv vorgestellt, bei dem sich durch eine gezielte Änderung der Krümmungsradien von zwei Spiegeln der diagonale Bildwinkel zwischen 20° und 60° variieren lässt. Die maximale Anfangsöffnung des Schiefspieglers erreicht dabei einen Wert von 4,5.

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Publication

Diffractive MEMS components, systems and applications

2009 , Grüger, H. , Egloff, T. , Pügner, T. , Scholles, M. , Schenk, H. , Lakner, H.

A MEMS (micro electro mechanical system) technology has been used to produce scanning grating chips which have a tiltable plate with grating structures optimized for the 900nm ... 2500nm range as diffractive element. Based on these chips different spectrometers and a hyper spectral imager have been realized for NIR-spectroscopic applications like agricultural quality analysis, recycling and process control. Ongoing developments aim at the further reduction of size and effort. Chip scale or wafer scale packaging technologies could help to shrink the complete spectroscopic system. The integration of signal processing and evaluation routines opens new applications for a broad range of scientific and non-scientific users.

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