Organic flexible electronics is an emerging technology with huge potential growth in the future which is likely to open
up a complete new series of potential applications such as flexible OLED-based displays, urban commercial signage, and
flexible electronic paper. The transistor is the fundamental building block of all these applications. A key challenge in
patterning transistors on flexible plastic substrates stems from the in-plane nonlinear deformations as a consequence of
foil expansion/shrinkage, moisture uptake, baking etc. during various processing steps.
Optical maskless lithography is one of the potential candidates for compensating for these foil distortions by in-situ
adjustment prior to exposure of the new layer image with respect to the already patterned layers. Maskless lithography
also brings the added value of reducing the cost-of-ownership related to traditional mask-based tools by eliminating the
need for expensive masks. For the purpose of this paper, single-layer maskless exposures at 355 nm were performed on
gold-coated poly(ethylenenaphthalate) (PEN) flexible substrates temporarily attached to rigid carriers to ensure
dimensional stability during processing. Two positive photoresists were employed for this study and the results on plastic
foils were benchmarked against maskless as well as mask-based (ASML PAS 5500/100D stepper) exposures on silicon
In this paper we report the use of projection optical lithography to pattern micron-sized features on
100 μm thick PEN foils. A foil-on-carrier lamination process was developed to ensure a good
dimensional stability during the lithographic processing and imaging of the foil. A stepper based
leveling metrology was used in characterizing the surface flatness of the foil-on-carriers. A
lithography process was developed to image micron and submicron patterns on foil substrates. The
process window for 1-10 μm features was determined from focus and exposure energy experiments.
The lithographic study indicated a reproducible and excellent imaging accuracy for patterning
micron-sized features on flexible substrates. This makes the technology very suitable for the
manufacturing of electronic devices with critical dimensions in the micron and submicron range. In
addition, we made transistors-on-foil demonstrators with the developed foil-on-carrier lamination
and imaging technology.
By using guide stars astronomers are able to detect very faint celestial objects that would otherwise be invisible. This however necessitates the simultaneous observations of two stars at the same time. A system called Star Separator will add this functionality to the ESO-VLTi. In case of the Unit Telescopes of the VLT this system has to be implemented in the existing infra structure while simultaneously fulfilling many functional requirements. The major one being that each set of stars have different relative positions while the star images rotate due to the earth rotation.
About two years ago TNO Science and Industry started to design and build the Star Separators for the Auxiliary Telescopes for the ESO VLTi. Now the Unit Telescopes will also be equipped with Star Separators. Obviously the design is based on that for the Auxiliary Telescopes. However additional functionality had to be implemented to compensate for the effect of earth rotation because no de-rotator, as for the Auxiliary Telescopes, can be implemented.
The presentation will explain the functionalities of the Star Separator and how the opto-mechanical design is done.
Inside the Star Separator system for the Unit Telescopes for the ESO-VLTi two mechanisms are implemented to compensate for the earth rotation that complicates the simultaneous and continuous observations of two stars. The function of the mechanisms is comparable to a de-rotator without the drawback of having to add three folding mirrors. One of the mechanisms is a scan mechanism with two independent orthogonal rotations. It makes use of flexures to eliminate play and to guarantee long term maintenance free operation. It also uses piezo stages for extreme accurate pointing (< 1μrad) for rotations of around 0.1 rad without hysteresis. The second mechanism realizes the optical star splitting being the primary function of the Star Separator.
The European Southern Observatory (ESO) is presently developing the PRIMA facility (Phase Referenced Imaging and Microarcsecond Astronomy). PRIMA will enable the observation of very faint celestial objects. A key element in this facility is the Star Separator that has been designed and is being built by TNO TPD in the Netherlands. This Star Separator makes it possible in principle to simultaneously observe two objects, the guide star and the faint object, with one telescope.
The separation of the faint object and the guide star is case dependent i.e. the separation between the two objects depends on the observation direction. This necessitates the use of a very accurate and stable pointing mechanism. The required repeatability of such mechanism is < 0.5 arcsec while its resolution should be < 0.1 arcsec. By using a statically determined fully elastic guiding and actuation mechanism in combination with closed loop driven piezos the realization of such mechanism was successful. A unique feature of the mechanism is that only the guiding/actuating mechanism needed to be designed. The rest is readily available from piezo suppliers. This makes this pointing mechanism a true low budget solution with excellent performance.
Measurement systems such as systems based on interferometric combination of beams of light, require highly accurate alignment of optical components such as mirrors to achieve fringes. Moreover, the stability of such alignment mechanisms must be even higher. Alignment devices based on flexures provide accurate alignment with excellent resolution, without play or hysteresis.
TNO TPD developed mechanisms for adjustment of mirrors in two degrees of freedom, meaning two rotations, and used these mechanisms in setups to achieve picometer stability. The paper describes the design process and the development of a set of alignment mechanisms. Theoretical and practical aspects are mentioned. First the design aspects for designing stable mounts are given, and then two mechanisms are described. The mechanisms consist of a monolithic adjustment mount for a mirror that is made by wire erosion in such a way that the mirror can rotate about two axes. Adjustment screws in combination with a lever and a gear provide easy and accurate adjustment of the rotation of the mirror. The combination of flexures result in a virtual point of rotation that is positioned on the centre of the mirror surface. In this case, the optical path length of the deflected light path will not change. Two degree of freedom rotation mechanisms have a generic design, so the design can be used in multiple instruments. The measurement systems show high stability of the components.
Homothetic mapping is a technique that combines the images from several telescopes so that it looks like as though they came form a single large telescope. This technique enables a much wider interferometric field of image than current techniques can provide. To investigate the feasibility, a research testbed is build know as Delft Testbed interferometer (DTI). DTI simulates a configuration of three telescopes collecting light of a set of 3 stars. The stars are simulated by coupling light of a Xenon light source into three fibres, which illuminate a parabolic mirror. The light that is used has wavelengths of 500 nm - 800 nm. The light of the three telescopes will be combined in such a way that the beam arrangement in the pupil plane corresponds with the telescope arrangement and the Optical Path Difference (OPD) is minimized for the three beams.
To achieve white light fringes with high visibility, the mechanical testbed that is 2 m x 1 m x 0.5 m in size, requires stable mounting of components. This paper describes the mounting of the diamond turned off-axis parabolic mirrors of 200 mm in diameter and 240 mm flat mirrors; furthermore, it describes components like the telescopes and the active controllable components for repositioning of the beam arrangement.
Mechanisms were developed for alignment of piezo actuators and for delay lines. The delay lines can also be used to compensate pupil rotation.
Test results demonstrate that the test setup is highly stable for temperature as well as for airflow, although the system is placed in a non-thermally controlled lab. This allows measurements of nm, in presence of μm disturbances.
The Delft Testbed Interferometer (DTI) will be presented. The basics of homothetic mapping will be explained together with the method of fulfilling the requirements as chosen in the DTI setup. The optical layout incorporates a novel tracking concept enabling the use of homothetic mapping in real telescope systems for observations on the sky. The requirements for homothetic mapping and the choices made in the DTI setup will be discussed. Finally the planned experiments will be discussed.
Opto-mechanical instruments are sensitive to temperature effects. The optical performance will be influenced by temperature variations within an instrument. Temperature variations can occur due to environmental or internal heat sources. Assembly at a different temperature than eventual operation of the instrument can also influence the performance. This paper describes principles to minimize thermal disturbance of optical performance. The thermal behaviour of a system can area-wise be divided in heat source, heat transfer area and place where the optical performance is affected. Placement of the heat source is critical. Using a large thermal capacity, the influence of the source will be minimized. Heat transfer can be controlled by insulation or by good conduction, the latter minimizing the thermal gradient along the thermal path. Thermo mechanical effects on the optical performance can be controlled using a thermal centre, a combination of materials with different expansion properties, low thermal expansion materials and scaling effects of the optical design.
TNO TPD designs and manufactures opto-mechanical instruments for space and astronomy. The design guidelines described are commonly used in these instruments. Several examples of the application of these design guidelines are presented in this paper.
The Delft Testbed Interferometer (DTI) will be presented. The main
purpose for the DTI is to demonstrate the feasibility of
homothetic mapping, both fixed and under scanning conditions. The
driving design issues behind the DTI will be presented together
with a list of experiments to be conducted with the DTI system in
the field of wide field imaging.