To realize the image quality of high end objectives, e. g. high NA microscope objectives working in the DUV spectral region the subgroups have to be manufactured with a mechanical precision which is difficult to achieve cost effectively. For high end microscope objectives the accuracy of the diameter of the lens mount must be within 1 µm, the run-out must be met within 1 µm and the distance of the lens vertex relative to the shoulder of the mount must fit within 1 µm. To realize the required precision, today various measurement techniques and production processes are used. Picking up the subgroups on different machining tools and measurement systems will loosen the accuracy. Here, we present the concept and the layout of a new manufacturing tool where we implemented the different measurement techniques in one CNC machining center.
Most recently the output power of fiber lasers with diffraction limited beam quality has been significantly increased. Further power scaling is usually limited by damage of the fiber end facets, thermo-optical problems or nonlinear effects. Microstructuring the fiber adds several preferable features to the fiber to overcome these restrictions. We review the advantages of rare-earth-doped photonic crystal fibers for power scaling of fiber lasers to the multi kW range with excellent beam quality.
Lens centering is a very traditional area. The question is how is to make a sophisticated robot? It has to detect the centering errors and to adjust the lenses in accordance to a well defined axis. There are four ideas for lens centering: adjustment by joining, by circular milling, by fast and slow turning.
Precise adjustment of the optical components may be achieved by stepped transfer of momentum via special stroke actuators (impulse hammers), which act onto a pre-stressed fiber- optical component. The motion of the component is controlled by a computer and a measurement device. The present paper discusses theory and experiment of this adjustment method, in particular motion behavior of pushed components under the influence of applied momentum, pre-stressing and frictional forces. Additionally it describes generically the wide application range of this adjustment method. In particular the article describes an innovative, automatic adjustment machine (robot) for the alignment of a single- mode fiber assembly, which was developed by the German Fraunhofer-Institute for Applied Optics and Precision Engineering (IOF) in collaboration with Agilent Technologies Inc., a global technology leader in communications, electronics and life sciences. The achieved adjustment accuracy for the fiber optical assembly is in a low micron range for the focusing motion and in a sub-micron for entering of the optics.
The principle of beam-splitter-multi-chip cameras consists in splitting an image into differential multiple images of different spectral ranges and in distributing these onto separate black and white CCD-sensors. The resulting electrical signals from the chips are recombined to produce a high quality color picture on the monitor. Because this principle guarantees higher resolution and sensitivity in comparison to conventional single-chip camera heads, the greater effort is acceptable. Furthermore, multi-chip cameras obtain the compete spectral information for each individual object point while single-chip system must rely on interpolation. In a joint project, Fraunhofer IOF and STRACON GmbH and in future COBRA electronic GmbH develop methods for designing the optics and dichroitic mirror system of such prism color beam splitter devices. Additionally, techniques and equipment for the alignment and assembly of color beam splitter-multi-CCD-devices on the basis of gluing with UV-curable adhesives have been developed, too.
Centering of optical lenses is necessary for obtaining the required resolution of an optical system, especially minimization of distortion. Advantage is the systematic approximation of an minimized centering error of the individual lens in relation to its housing. A method by using stick-slip effect has been developed. The process has an automatic numerical control which operates during rotation of the lines. The adjustment tool is driven by electro-magnetic hammers in a step-by-step mode.
A line scanning device for laser based High Definition Television applications is being developed at IOF. High speed scanning is achieved by a rotating polygonal mirror supported from two hemispherical aerodynamic bearings. For an operation of around 80 000 rotations per minute (rpm), balancing of the rotor to a high precision is necessary. We derive the balancing requirements from elementary considerations and describe in detail how balancing is performed. The method of balancing and the measurement equipment are presented. From the experimental results it is seen, that sufficient balancing for operation at target speed can be obtained within the Rigid Rotor Approximation. However, stability is not satisfactory without additional efforts. Therefore, an `elastic' balancing concept is presented, where mirror related unbalances are compensated on the part itself. Preliminary results within this approach show that stability of the system is improved. This opens up the possibility to significantly increase long term stability and confirms the basic design concept.
In the field of microsystem technologies one future trend is recognized. Manufacturing microsystems monolithically is becoming less reasonable and practicable with increasing applications and complexity. Assembly processes will be needed for the majority of microsystems due to difficulties arising in manufacturing complex structure out of one piece, the need for components to be manufactured by different processes, or simply to connect the microsystem with the macroscopic environment. Additionally, high production output at competitive costs is attainable only by replacing manual assembly with new automatic handling, positioning and joining technologies. To assist in development of microassembly processes, techniques from macroassembly technology may be transferred. Especially in microoptics existing know-how from macroscopic lens-assemblies might be transferred. The microsystem presented a microoptical beam forming system consisting of one SELFOC- and two GRIN- microlenses joined by adhesive bonding, fixed in a protection-mount, which serves additionally as a coupling unit of a multimode fiber, and finally adjusted to a laser diode at a defined distance according to an optical design. Besides complications due to the sensitive optical surfaces and the small and varying geometries of the system components, there is the additional requirement of high accuracies, of 0.1 to 2 micrometers and down to 1 arcsec, needed to realize the optical function of the microsystem. The assembly system, based on a six-axis-precision robot accurate to less than 1 micrometers , consists of a modular designed tool changing system, specially-adapted, self- adjusting grippers, several sensors to monitor positioning, dosage devices to dispense measured quantities of adhesive, in the range of nanoliters, and a specially designed assembly platform to clamp microparts of different geometries.
Using a drop-on-demand print head allows for PC-controlled production of various types of microlenses as well as lens arrays. The possibility to place microlenses on arbitrarily shaped substrates allows for novel optical elements like beam splitters or non-planar scattering discs. Another interesting possibility opened by pre-shaped substrates is the production of concave lenses, which are key elements for aberration correction in micro-optical systems.
With the continuing development of laser-display-technology, a new possibility for the production high level image projection is forwarded and with it the beginning of a new era in television: TV picture formats previously thought impossible, the sharpness, color intensity and unsurpassed resolution of which make the dream of home cinema a reality. The key to this experience is visible laser light in red, green and blue, projected on a screen with the aid of horizontal and vertical deflection units. In this paper, a primarily horizontal deflection system in the form of a rotating polygonal scanner is described. The design of this scanner assembly combines a double spherical air bearing with an integrated polygonal mirror for deflection and a high torque inside drive for quickly reaching high rotation. The Fraunhofer Institute of Applied Optics and Precision Engineering (IOF Jena) develops, from conception to assembled prototype, new self-acting precision bearing systems. This new scanner solution developed out of IOF's previous developments resulting in the first ever sealed, minimal-maintenance, self- acting bearing.
In future most microoptical components will be applied as hybrid integrated systems. The manufacturing of beam shaping optics consisting of two or more microoptical components in a hybrid microsystem places demanding requirements on the assembling process due to the need for extreme positioning accuracy. The basis of the micro-assembly system is a high- precision robot. The robot is used to handle, to grip and to join the components with minimal position deviations. Various vacuum grippers are described. The dispensing of adhesive drops of approximately 5-30 nl volume is an essential part of the task.
The greatest hindrance to wider applications of micro-optics is the inefficiency of the mounting process. Currently there are attempts to remedy this through transferring the know- how from the manufacture of great repeater lenses etc. into the micro-optical technology. Additionally there are necessary new methods for handling and exact positioning. The discussed mounting equipment consists in a six-axis robot, some special developed grippers, a working station for the adjustment and a dosage device (ink-jet and stamp- transfer technique). In future some ideas for special equipments of precision mounting are to be realized. The range of accuracy contents about 0.5 to 5 micrometer and some arcsec.
The manufacturing of beam shaping optics consisting of two or more microoptical components in a hybrid microsystem places high demands on the assembling process for positioning accuracy making a manual alignment process inadequate. The basis for the micro-assembly forms a robotic system. This robot makes it possible to handle, to grip and to join the components with very small position deviations and to apply very small drops of adhesives. The dispensing of adhesive drops of approximately 1 nl volume is an essential part of the task.
The demands of higher precision, higher speed, higher stiffness, and new files of application determine the improvements and new developments of precision bearings. In many applications air bearing systems are often the only alternative, especially when precise movements free of vibration, are necessary. The performance of high precision bearings for scanning is primarily dependent on the design and on the individual components. Main components are the bearing, the drive system, the controller and the optical mirror unit. Runout errors and vibration excitation lead to planar and roundness errors and to an increase in image errors. It is difficult to compensate the highly dynamic errors of a bearing system. Desirable is a very stiff, reproducible and very smooth running bearing system as a basis for good scanning results. Through suitable technology and choice of materials it is possible to optimize an air bearing for a special field of use. With the application of glass and glassceramic new possibilities for the production of precision bearings are present. One such example is a precision glass bearing made of these materials with an integrated polygonal mirror for scanning based upon the well-known design principle of double spherical air bearings.
There is a trend in the optical industry to automate the edge-blackening of optical components. The goal of edge- blackening is to coat the areas outside the functional region of optical components, namely the peripheral areas including the surface edge or 'diaphragm' and apertures, with light absorbing, index-matched material to minimize scattering light. The common method today is the manual application with brush or ink-writer of quick-drying liquid pigmented synthetic resin. The lenses are fitted at a rotary table with a vacuum-pump or with considerable disadvantage inhibiting the automation. Another problem is the use of a high number of lacquers with different or partly unknown properties, due to varying chemical bases.
An effective and universally useful means of adjustment in the realm of precision engineering and optics became possible with the realization of a new driving mechanism. In contrast to traditional adjustment methods, the mechanical component is situated in its final position before the start of the adjustment process. Specific mechanical impulses generated to be a striking mechanism are transmitted either directly to the mechanical component or indirectly to its housing (carrier). This results in minute linear motions or fine angular motions caused by the stick-slip-effect. The following paper explains the preliminary results of our theory and our experiments. A prototype of the electro-mechanical striking mechanism has been researched and developed by the Fraunhofer Institution for Applied Optics and Precision Engineering, Jena, Germany. PC-based algorithm software allows fast and exact positioning for precision engineering and micro-optical components. The described arrangement makes possible step-by-step adjusting movements with the minimum resolution of the steps to 0.5 arcsec.