Although confocal fluorescence microscopes are widely used in biology and have been proven to be promising diagnostic tools in dermatologic diagnostics, they are at present uncommon in medical practice. This is mainly due to high costs of acquisition and their large and complex outline. With the integration of a MEMS scanner we present a demonstration system of a confocal fluorescence laser scanning microscope which is affordable and portable. It has a field of view of 500 mu m x 500 mu m and is mainly composed of off-the-shelf components.Since one of the most important factors for obtaining a good, high contrast image is to collect enough photons, it is evident that good optics for optimal collection of light is necessary. These optical performance requirements for the microscope will be discussed in detail. In this design, the MEMS mirror acts as limiting system aperture and directly translates into the amount of laser beam clipping for a given beam diameter. Gaussian beam formulas are valid for an aperture-to-beam-radius T> 1.6. The beam diameter on the other hand translates to necessary relay optics for an addressed Numerical Aperture >= 0.4. On the demonstration setup these different figures of merit are discussed and compared with first images taken of biological samples. (C) 2013 Elsevier GmbH. All rights reserved.

Confocal fluorescence microscopes are a promising imaging tool in medical diagnostics due to their capability to selectively survey cross-sections of individual layers from 'thick' samples. Non-invasive depth resolved investigation of neoplastic skin disorders is one example among other applications. However these microscopes are at present uncommon in medical practice. This is due to their main application area in research. The instruments dealt with here are generally complex, stationary units and are accordingly cost-intensive.It is for this reason, that we have designed a robust and portable MEMS based confocal fluorescence microscope with a field of view of 0.6mm x 0.6mm. This has been made possible by the integration of a 2D micro scanner mirror developed at Fraunhofer IPMS. A variable acquisition depth of cross-sectional images of the fluorescence specimen is enabled by an integrated z-shifter.With the use of commercially available optics an optical demonstrator set up has been realized. To characterize and to demonstrate the ability of this system test measurements were performed. The resolution of the microscope is better than 228 lp/mm determined by 1951 USAF resolution test target. Images of various biological samples are presented and optical sectioning capabilities are shown. A comparison of the measured with the predicted system performance will be given.

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 500 mu m x 500 mu m. 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 perform cross-sectional imaging of fluorescence specimen will be given by an integrated z-shifter.

We report on our investigation to precisely actuate diffractive micromirror arrays (MMA) with an accuracy of lambda/100. The test samples consist of analog, torsional MEMS arrays with 65 536 ( 256x256) mirror elements. These light modulators were developed for structured illumination purposes to be applied as programmable mask for life science and semiconductor microscopy application. Main part of the work relies on the well known characterization of MEMS mirrors with profilometry to automatically measure and approximate the MMA actuation state with high resolution. Examples illustrate the potential of this strategy to control the tilt state of many thousand micromirrors within the accuracy range of the characterization tool. In a dynamic range between 0 and >250 nm the MMA deflection has been precisely adjusted for final MMA application in the deep-UV - VIS - NIR spectral range. The optical properties of calibrated MMAs are tested in a laser measurement setup. After MMA calibration an increased homogeneity and improved image contrast are demonstrated for various illumination patterns.

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.

Although skin is easily accessible to optical methodologies, biopsies are at present a widely used procedure in dermatologic diagnostics. However fluorescence confocal laser scanning microscopy (F-LSM) is a non-invasive imaging technique that allows depth resolved investigations of inflammatory and neoplastic skin disorders in vivo and at high resolution. By applying substances onto or into the epidermis F-LSM is well suited to obtain information regarding the morphological structures of the skin down to a hundred micrometers below the skin surface. Compared to conventional light microscopy of histological sections this optical method has a clear advantage in the case of kinetic measurements. To this end, we have designed a portable confocal fluorescent microscope for future dermatologic studies, offering a field of view of 600μm x 600μm. Based on a dual-axis MEMS mirror (Fraunhofer IPMS, Germany) the confocal character of the system resides in the use of the same path for illumination and detection with spatial filtering of the signal collected from the subsurface analysis plane. Illumination is provided by a 488nm laser and the backscattered fluorescence light is separated from the illumination light by a filter, before being detected behind the pinhole. To reconstruct the image the measured intensity and position information is correlated. The ability to perform crosssectional imaging in the skin will be given by an integrated z-shifter.

We present the correction of distortion for a novel type of an all-reflective zoom objective. The all-reflective 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. (C) 2010 Optical Society of America

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.

2D micro scanning mirrors are presented which make use of a degressive spring allowing to achieve an optical scan range of up to 112° x 84°, optically. The scanning mirrors are deployed for highly miniaturized monochrome and full color projectors as well as for laser imagers. The projectors allow for projection with VGA resolution at 50 Hz frame rate. The laser imager supports full color SVGA resolution at 30 Hz frame rate. Both, the projector and the imager are based on a single 2D scanner chip and thus could be combined in a single ultra compact system for simultaneous imaging and projection with high depth of focus.

We fabricated OLEDs having the evaporated Yb cathode and the sputtered Al cathode. Magnetron sputtering is a versatile deposition method, but the energetic particles during sputtering process can damage the underlying organic layers. We applied various process parameters to explain the role of Ar neutrals quoting the former researches. OLEDs showed almost comparable degradation under the discharge voltage of 300 V, but serious degradations were found at the discharge voltage of over 300V and the low process pressure. The degradations influenced on the lifetime of OLED, and the measured luminance decay was much larger than the OLED having the evaporated Yb cathode due to the high leakage currents.

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 d(31) is measured for tempered and untreated aluminum nitride thin films with high enhanced texture coefficients by quasistatic deflected wafer cantilevers.

A technology approach is presented which enables an initial permanent counter electrode deflection of planar out of plane comb drive actuators allowing quasistatic operation of an electrostatic microscanner. The device is assembled by mounting a top wafer with salient stamps onto a mirror wafer. The commonly fix in plane counter electrode parts on the mirror wafer are connected to deflectable platforms via a mechanical structure of coupled hinges. During the wafers assembly the down pressing stamps displace the platforms and result in a predefined permanent out of plane counter comb deflection.

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.

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 nonscientific users.

Laser projection systems that use the flying spot principle and which are based on a single MEMS micro scanning mirrors are a very promising way to build ultra-compact projectors that may fit into mobile devices. First demonstrators that show the feasibility of this approach and the applicability of the micro scanning mirror developed by Fraunhofer IPMS for these systems have already been presented. However, a number of items still have to be resolved until miniaturized laser projectors are ready for the market. This contribution describes progress on several different items, each of them of major importance for laser projection systems. First of all, the overall performance of the system has been increased from VGA resolution to SVGA (800x600 pixels) with easy connection to a PC via DVI interface or by using the projector as embedded system with direct camera interface. Secondly, the degree of integration of the electronics has been enhanced by design of an application specific analog front end IC for the micro scanning mirror. It has been fabricated in a special high voltage technology and does not only allow to generate driving signals for the scanning mirror with amplitudes of up to 200V but also integrates position detection of the mirror by several methods. Thirdly, first results concerning Speckle reduction have been achieved, which is necessary for generation of images with high quality. Other aspects include laser modulation and solutions regarding projection on tilted screens which is possible because of the unlimited depth of focus.

Within this paper the so called “birth and death” method is demonstrated in use with COMSOL Multiphysics. With this method the free and reactionless (death) movement of a solid structure on deformed geometries and the activation of this solid structure at later simulation steps (birth) is possible. For demonstrating the benefit, this method was applied to simulate the thermal induced bending of multilayer coatings. The “birth and death” method is more accurate than standard bulk approaches because it is possible to calculate the influence of layer deposition on deformed substrates.

In this study a high efficient p-i-n type orange organic light emitting diode (OLED) is presented. It is based on doped charge transport layers to realize low operating voltage and emitting layer which consists of alpha-NPD(4,4-bis [N-(1- naphtyl)-N-phenylamino]biphenyl) and Iridium(III)bis(2-methyldibenzo-[f,h]quinoxaline)(acetylacetonate) as a host and a phosphorescence dye dopant respectively. Organic layers are vacuum-sublimed on ITO-coated glass substrates in vertical inline deposition tool, and aluminium is deposited directly on organic layer by DC magnetron sputtering to form a cathode. Since sputter deposition of top electrode is known to damage organic layers and degrade OLED performance, various sputter process parameters are selected and applied for cathode formations, and the OLEDs are characterized by means of I-V-L measurements. The OLED characteristics are evaluated with the plasma factors based on sputter process parameters in order to explain the damage sources from sputtering process. The characteristics of OLEDs that cathodes are deposited by sputtering and evaporation are compared. The fabricated OLED which has the lowest damage level exhibits almost comparable result to the OLED that the cathode is deposited by evaporation. The OLED shows good performances of driving voltage of 4.25 V and luminous efficacy of 7.77 lm/W and current efficiency of 10.68 cd/A at 1000cd/m2.

Photogrammetric imaging and measurement techniques are widely used for capturing three-dimensional scenes in sciences and arts. Traditional approaches performing extensive calculations on multiple images are more and more replaced by higher integrated and faster operating measurement devices. This paper presents a MEMS-based system for distance measurement that can be integrated into a commercially available panorama camera and will add three-dimensional measuring capabilities. This combination is very suitable to displace the current procedural manner using different instruments to acquire three-dimensional data on the one hand and texture on the other hand. The data acquisition is simplified and extensive calibration and data transformations is no longer needed. Thereby the accurate allocation between texture and distance data is firmed by design. This work outlines the optical concept to couple both measuring systems into one optical path. While texture is captured line wise, the distance is acquired sequentially. Integration of both functionalities into one housing and one optical system design requires miniaturized components for deflection of the measurement beam. One solution is to use a resonant MEMS scanning mirror. The paper describes the resulting optical setup in detail. The integrated construction principle induces special requirements for the LIDAR distance measuring method used here. In order to ensure eye safety, the measuring light beam is limited to low power signals. The contribution also will present an approach for processing low level signals and performing high measuring rates.

Fraunhofer IPMS already demonstrated a technology for resonant 2D MEMS scanning mirrors, where the resonant driving principle has been established for mirror and frame. Using frequencies of 2500 Hz for the frame and 28 kHz for the mirror full color laser projection systems have been developed. Multiple Lissajous patterns are needed for the generation of one picture. Thus efficiency and frame rate are limited. Recently, a new approach has been invented: still a resonantly moving mirror is used for the fast movement but the frame is driven by a quasi-static drive. Among the several driving mechanisms possible the piezoelectric drive is the most promising. By choosing appropriate piezoelectric materials MEMS process integration is feasible. Besides a quasi-static deviation to generate pictures further options arise. The picture generation algorithm can be simplified if the movement along the rows is stepwise and the movement back is one fast step. This saw tooth like motion could be achieved through the high frequency response of piezoelectric materials. The setup of the chip is similar to the existing 2d scanning mirrors: Inside the mirror with an area of 0.25 to 9 mm2 is mounted on two spring bearings to the frame and resonantly driven through comb structures. The frame bearing to the chip is realized through flat bending actuators. Either the position change has to be considered at the picture generation or a layout has to be designed in a way that ensures a Pivot point in the middle of the mirror.

At Fraunhofer IPMS Dresden micromechanical mirror arrays are developed and fabricated using a high-voltage CMOS process for applications such as lithographic mask writers and adaptive optics. Different approaches for the fabrication of micromechanical mirror arrays with up to 1 million analogue addressable pixels in a MEMS-on-CMOS technology are discussed: sacrificial layer technologies of 1-level actuators made from a single Al-TiAl-Al structural multilayer or 2-level actuators with an additional TiAl hinge layer respectively. Also the fabrication of single crystalline Si micro-mirrors using layer-transfer bonding is discussed.