Background and Mission
The Optoelectronics and Measurements group (OPME) comprises an intensive collaboration network of researchers at the Optoelectronics and Measure-ment Techniques Laboratory at the University of Oulu, the Measurement and Sensor Laboratory in Kajaani and VTT Electronics. The group employs more than 60 persons in its research work. In accordance with the principles of Infotech Oulu, the group engages in basic research, drawing on the resources of the three organizations, as well as their extensive industrial connections and wide experience in technology trans-fer. The work includes co-operation projects related to long term research but most product development projects are omitted. As a participant in the Infotech Oulu graduate school, the group also focuses its ef-forts on arranging lecture series and graduate school courses for graduate students. During 2002 the group organized the traditional 3rd Infotech Oulu Workshop on Optoelectronics Devices and Instrumentation. In addition, 5 lectures were organized.
Research collaboration between domestic and inter-national partners has been active. Domestic project collaboration during 2002 was done with the Circuits and Systems Group (CAS) and Electronics Materials, Packaging and Reliability Techniques (EMPART) of Infotech Oulu along with the manufacturing technol-ogy group teams of VTT Electronics. In paper and pulp applications there was co-operation with the Department of Process Engineering of the University of Oulu (Prof. Niinimäki, Prof. Kortela, Prof. Leiviskä) and Metso company (Dr. Pakarinen).
At the international level, the Optical Sciences Cen-ter of the University of Arizona, Tucson, USA was the most important co-operation partner including re-searcher exchange, project co-operation and educa-tional activities. The Technical University of Gdansk, Poland; University of Maryland, College Park, USA; Fraunhofer Gesellschaft-IZM, Berlin, Germany; Tsinghua University, Beijing, China; A.F. Ioffe Insti-tute, St. Petersburg State Technological University, St.Petersburg and International Laser Center of
Mos-OPTOELECTRONICS AND MEASUREMENTS
Professor Risto Myllylä, Optoelectronics and Measurements Laboratory, Department of Electrical and Information Engineering, University of Oulu
Professor Harri Kopola, VTT Electronics, Optoelectronics, Oulu
Juha Kalliokoski, Director of the Measurement and Sensor Laboratory (Kajaani), Univ. of Oulu
[email protected], [email protected], [email protected] http://www.infotech.oulu.fi/opme
cow State University, Russia; Dublin City University, Ireland and University of Luleå, Sweden were also among the primary international co-operation partners of the group.
The group performs basic research in optoelectronic measuring techniques with particular emphasis on the practical applications of these techniques. In this un-dertaking, the group focuses on measuring and mod-eling the propagation of light in turbulent and scattering media such as atmosphere, human tissue, pulp, paper and optical fibres. Interesting properties are, for example, scattering, absorption, reflection, time-of-flight and the so-called photoacoustic phenom-enon. Optical coherence domain measurement tech-niques like laser Doppler and optical coherence tomography (OCT) are leading to an increasing num-ber of applications in biomedical diagnostics. In ad-dition, applications of low coherence interferometry in the industrial measurement solutions are increas-ing. New materials, manufacturing technologies and integration of the systems are developed by combin-ing customized micro-optical devices, optoelectronic devices and novel packaging technologies. The find-ings are used in applications in medicine, the paper, pulp and mechanical wood processing industries, as well as optical communication and instrumentation.
Scientific Progress
Research on MOEMs (Micro Opto Electro Mechani-cal Systems) for sensor and telecommunication tech-nology has been initiated. Optical techtech-nology for wireless communication and measurement is an im-portant application area. Instrumentation within the mechanical wood, pulp and paper industries, and non-invasive methods of monitoring human health are the other application areas targeted by the optoelectron-ics and measurements unit. Microwave measurement techniques have a lot of potential in material exami-nation. In the following, examples of the research work in different applications of the OPME group are pre-sented.
Development of the micro-optical table con-cept
The micro-optical table (MOT) concept was studied for a zero-alignment microscopic system. In practical terms, the zero-alignment concept translates into as-sembly errors that are smaller than the tolerances dic-tated by the performance of the optical system. Very low assembly errors will be achieved through photo-lithographically patterned positioning features on each optical component. The accurate positioning of the optical elements on the MOT is achieved through the sub-micron-precision layout of the photomask. A conceptual design of a fully integrated, optical sec-tioning multi-modal miniature microscope (4M) is shown in the figure. A scanning grating, located in the image plane of the microscope, results in structured illumination and enables optical sectioning. The mi-croscope design measures 9 mm in length, 5 mm in width and 3 mm in height.
Conceptual design of miniature optical data storage systems
A miniaturized data storage system is shown in the figure. In order to perform read and write operations, the following must be performed: the beam has to be kept focused on the uneven surface of the storage media and the data track has to be followed. The de-sign and optimization process includes iterative simu-lations as well as experiments to verify the simusimu-lations.
Wavelength tunable laser
The figure shows a fiber pigtailed wavelength tun-able laser that is potentially suittun-able for mass-mar-kets due to the fact that it comprises of conventional, low-cost devices, such as, an edge-emitting diode la-ser, photodiode, coupling lens and single-mode fiber. The only exception from conventional devices is an electrostatically controllable silicon micromachined MOEMS device, which, however, is potentially a mass-producible device in large manufacturing quan-tities. Wavelength tunable lasers, packaged using LTCC technology, resulted in an 11 nm wavelength tuning range at 1540 nm with a 1.1 to 2.7 nm spectral width.
The printable optics and electronics (PRINTO) The aim of the PRINTO project is to develop roll-to-roll fabrication techniques. This comes from rapid de-velopment in the field of organic and hybrid materials. Devices such as organic light emitting diodes, solar cells, polymeric electronics and flat optics can now be produced on flexible plastic or paper substrates. The technology enables roll-to-roll processing and cost-effective mass production of optoelectronic and electronics devices. Potential applications include embedding photonics and electronics into the pack-aging of a product.
Medical and industrial instrumentation tech-niques and devices
The group is working with optical high and low co-herence measurement techniques and spectroscopy for different medical and industrial applications. These include laser Doppler, optical coherence tomography (OCT) and photo acoustic spectroscopy (PAS). Sev-eral research projects have been started where solu-tions with wireless communication are applied to establish the data transfer link between measurement sensors and a control unit/monitoring device both in an industrial and hospital environment.
A wavelength tunable laser module based on the use of an electrostatically controllable silicon micromachi-ned MOEMS device and LTCC packaging technology.
Miniaturized optical data storage system. A pen-sized miniature microscope: a) a conceptual, scaled diagram of a pen-sized imaging probe equipped at the tip with a 4M device; b) a magnified view of the 4M device layout.
Optical coherence domain techniques
From the optical high coherent measurement meth-ods, a laser Doppler technique based on self-mixing interferometry has been used to measure the arterial pulse shape, which is a very important indicator of the state of the cardiovascular system. Other param-eters from the cardiovascular pulse that have been stud-ied using self-mixing interferometry are autonomic regulation, arterial pulse wave velocity and arterial elasticity.
OCT is a new, very promising imaging technique based on the low coherent interferometry. It is a fascinating measurement method, not only for noninvasive medi-cal instrumentation but also for different industrial applications. As a basis for OCT, the low coherent interferometry method has been used to visualize spe-cially fabricated wood fiber tissues. In addition, the Doppler OCT technique has been applied to flow ve-locity profile measurements of highly scattering sus-pension. As an example of this, a 3D flow velocity profile of scattering suspension in a one millimeter thick glass capillary is shown in the figure. The mea-surement system is developed both for OCT and DOCT applications, which automatically reconstructs a 2D slice image of an object’s internal microstruc-ture with a resolution of less than 15 µm. Moreover the system is able to determine the refractive index variation of scattering material as a function of depth.
Photoacoustic spectroscopy
Erythrocyte aggregation and sedimentation are stud-ied using the PAS technique. By measuring the time delay of a photoacoustic wave from the boundary be-tween the red blood cells (RBC) and plasma/PBS so-lution, the erythrocyte sedimentation rate can be detected. When macromolecular polymer such as dex-tran-70 solution is added into blood, the boundary between RBCs and plasma/PBS solution no longer exists. By recording the changes of PA and optical signals from samples in the whole measuring process, it demonstrates that dextran-70 causes biphasic be-havior of blood aggregation and sedimentation: it in-creases aggregation and sedimentation rate at low
concentration, maximizing at about 3 g/dl dextran, be-yond which it decreases them.
Wireless hospital
The purpose of the project is to go through and create technologies which are applicable for wireless data transmission in a hospital LAN between the patient and the monitoring equipment. An additional purpose is to go through data transmission from the monitor to the hospitals data system.
As a result of the project, there will be a requirement specification made for wireless data transmission tech-nology and the applicable low duty sensor technol-ogy which can be used to measure certain parameters of the patient and transfer them wirelessly to the moni-toring apparatus.
The survey of the data transmission technology cov-ers world wide frequency bands from low induction frequencies to gigahertz microwave frequencies. The requirement specification includes the frequency band applicable to the technology, the parameters of the data transmission and the power supply. The goal is to find a world wide frequency band, where the new technol-ogy can be used without new permission procedures. As an alternative, frequency-flexible and program-mable adjustable solutions will be studied. A risk analysis will be made for the chosen technology con-sidering the special requirements in a hospital envi-ronment, and product liability.
Microwave material examination
The research on mechanical wood processing indus-try started in the Measurement and Sensor Labora-tory (MILA) in 1999 with the PUUMI project. At that time, one selected technique for such studies con-cerned microwaves. Microwave technology has been mainly exploited in communication systems. However, our purpose is to use microwave as a tool for material examination, especially for non-destructive testing of wood. Our research interests include the observation of outer knots (branches), inner knots, decayed and rotten parts of wood and homogeneity of wood mate-rial. In year 2002 wood studies which make use of microwaves were carried out within the MYY and MOKSA projects.
The main commercial means for microwave studies at MILA are the vector network analyser, the spec-trum analyser and the simulation software. However, for a particular wood application a novel measure-ment system has to be designed and constructed - so far three units have been built with co-operation with Prof. P. Eskelinen (HUT) and Dr. H. Eskelinen (LUT). The first one determines the structure of wood logs 3D velocity profile of 0.3% Inralipid suspension.
and planks. The device operates at a frequency of 15 GHz. The measured quantities are the attenuation, the phase of a transmitted wave and the amplitude of a reflected radiation. We have managed to measure knots with a minimum size of 10 mm. Besides of the size, it is possible to measure the place of the knot in timber as shown in the figure. Also hollow parts of timber can be exposed. The second unit is the moisture meter and its frequency is 1.7 GHz. At moment, the mois-ture measurements give us only relative and approxi-mate values. The latest system built at MILA works at millimetre wavelengths and it is designed for struc-ture measurements, especially for detecting small knots. The functional testing of the devise is still un-finished. The frequency employed is 34 GHz.
All the above-mentioned, self-built equipment is suit-able for a laboratory environment and therefore they are adapted for basic studies of wood and its struc-ture. However, we believe that a tested and robust microwave measurement method may be transferred to the forest (employed in forestry machinery) or to sawmills as well.
Exploitation of the Results
Active interaction with industry ensures the rapid ap-plication of research results. The work of the group paves the way for the introduction of a new genera-tion of optoelectronic sensors and instruments based on micro-optics, micromechanics and microelectron-ics.
The research results of the group have been presented at conferences and published in professional journals. In projects funded by TEKES, the acquired knowl-edge has been directly transferred to the participating enterprises. Also commissioned research has been di-rectly reported to the enterprises concerned, and sev-eral senior and junior researchers have taken up employment with them.
Future Goals
Reaching an acknowledged position as a top Euro-pean research unit in its own field forms a key objec-tive for the group. Another important goal involves becoming a central cooperation partner for Finnish industry in the development and application of mea-suring techniques and instrument technology. In ad-dition, the group advances the scientific understanding of optoelectronics and measurement applications and produces high-quality dissertations and publications. Finally, the highly applicable, in-depth, information produced by the group also makes a contribution to product development and the creation of new busi-ness opportunities.
The OPME group has been joined by Prof. Mämmelä’s research unit from VTT Electronics. This unit’s main function is to bring professionals in wireless commu-nication to increase the know-how of the group in this field. In the future, the aim is to increase the intelli-gence of sensors with built in wireless communica-tion links. This will increase the informacommunica-tion transfer and bring more flexibility to the complex sensor net-work that exists in the industrial environment. One idea is also that separate sensors could operate inde-pendently and share information if needed.
The key elements in the development of a smart sen-sor network are the field of measurement physics and modeling. The group will continue modeling the propagation of light in turbulent and scattering me-dia. Also new measurement techniques in combina-tion with tradicombina-tional ones will be developed further for new applications. The focus will be on coherence domain techniques (Laser Doppler and OCT), spec-troscopy (PAS) and photon migration measurements (TOF).
The aim is to combine customized photonic devices and advanced materials and packaging technologies for their implementation in novel systems for optical communications, wireless instrumentation and ma-chine automation. New packaging and manufacturing techniques will be developed. Module integration is an important step when sensor networks are devel-oped. In this step, new measurement techniques, com-munication methods and sensor materials are integrated to an adequate module that is competitive and reliable in the measurement environment. One aim is also harnessing paper production technology for cost effective optoelectronics
The example of a research field is shown in the next figure. Intelligent sensors, which exploit advantages of new measurements techniques, materials and mod-ule integration, transmit information between the pro-A wood log represented by the microwave quantities
(attenuation, phase and reflectance). Knots may be observed at distances of 30, 90 and 125 cm.
cess and the user. Communication is operated using different wireless techniques (RF/optical). The user has a real time connection to different parts and pa-rameters of the process.
As a participant in the Infotech Oulu graduate school, the group will continue effective education of gradu-ate students. The aim is to continue traditional work-shops on optoelectronics devices and instrumentation. In addition, internationally well known scientists will be invited to give lectures to the students.
Personnel
s r o t c o d & s r o s s e f o r p 11 s t n e d u t s e t a u d a r g 35 s r e h t o 20 l a t o t 66 ) % 8 2 T T V , % 2 7 . v i n u ( s r a e y n o s r e p 46External Funding
e c r u o S EUR d n a l n i F f o y m e d a c A 43000 n o i t a c u d E f o y r t s i n i M 164000 s e k e T 960000 c il b u p c i t s e m o d r e h t o 184000 e t a v i r p c i t s e m o d 127000 l a n o i t a n r e t n i r e h t o + U E 426000 l a t o t 1904000Doctoral Theses
Zhao Z (2002) Pulsed photoacoustic techniques and glu-cose determination in human blood and tissue. University of Oulu, Acta Universitatis Ouluensis, Technica, C 169 Hyvärinen V (2002) On the optical inspection of pharma-ceutical compacts and punches. University of Joensuu, De-partment of Physics, Väisälä Laboratory. Dissertations 32.
Selected Publications
Räty J, Peiponen K-E, Peiponen A, Jääskeläinen A & Mäkinen MOA (2002) Measurement of wavelength-depen-dent complex refractive index of transparent and absorbing liquids by a multifunction reflectometer. Applied Spectros-copy 56(7): 935-941.
Palviainen J, Sorjonen M, Silvennoinen R & Peiponen K-E (2002) Optical sensing of colour print on paper by a diffractive optical element. Meas. Sci. Technol. 13: N31-N37.
Hast J, Myllylä R, Sorvoja H & Miettinen J (2002) Arterial pulse wave shape measurement using self-mixing effect in a diode laser. Quantum Electronics 32(11): 975-980. Alasaarela I, Karioja P & Kopola H (2002) Survey and com-parison of distributed fibre optic sensing methods for mea-suring location and quantity information. Optical Engineering 41(1): 181-189.
Karppinen M, Kataja KJ, Mäkinen J-T, Juuso S, Rajaniemi H, Pääkkönen P, Turunen J, Rantala J & Karioja P (2002) Wireless infrared data links: ray-trace simulations of dif-fuse channels and demonstration of diffractive element for multi-beam transmitters. Optical Engineering 41(4):899-910.
Kärkkäinen AHO, Rantala JT, Maaninen A, Jabbour GE & Descour MR (2002) Siloxane based hybrid glass materials for binary and gray-scale mask photoimaging. Advanced Materials 14: 535-540.
Kololuoma T, Kärkkäinen AHO & Rantala JT (2002) Novel synthesis route to conductive antimony doped tin dioxide and micro-fabrication method. Thin Solid Films, 128-131. Kärkkäinen AHO, Tamkin JM, Rogers JD, Neal DR, Hormi OE, Jabbour GE, Rantala JT & Descour MR (2002) Direct photolithographic deforming of organo-modified siloxane films for micro-optics fabrication, Accepted to be published in Applied Optics.
The example of a research field, where separate sen-sors analyze process parameters and give real time information to the user.
