Dr. Kimmo Keränen Profile

Dr. Kimmo Keränen

Research Scientist at VTT Technical Research Ctr of Finland Ltd

SPIE Involvement:

Author

Publications (17)

Proceedings Article | 16 February 2017 Presentation + Paper

Presentation + Paper

Design of a backlighting structure for very large-area luminaries

L. Carraro, A. Mäyrä, M. Simonetta, G. Benetti, A. Tramonte, M. Benedetti, E. Randone, A. Ylisaukko-Oja, K. Keränen, T. Facchinetti, G. Giuliani

Proceedings Volume 10126, 1012603 (2017) https://doi.org/10.1117/12.2251825

KEYWORDS: Light emitting diodes, Reflectivity, Optical lithography, Optimization (mathematics), RGB color model, Semiconductors, Manufacturing, Optical design, Optics manufacturing, Laser engraving, Waveguides, Raster graphics, Light sources, Detection and tracking algorithms

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Proceedings Article | 16 February 2017 Presentation + Paper

Presentation + Paper

Design of a lighting system with high-power LEDs, large area electronics, and light management structure in the LUMENTILE European project

L. Carraro, M. Simonetta, G. Benetti, A. Tramonte, G. Capelli, M. Benedetti, E. Randone, A. Ylisaukko-oja, K. Keränen, T. Facchinetti, G. Giuliani

Proceedings Volume 10124, 1012419 (2017) https://doi.org/10.1117/12.2251795

KEYWORDS: Human-machine interfaces, Free space optical communications, Light emitting diodes, Electronics, Electrical efficiency, Light sources and illumination, Photonics, Video, Feature extraction, Diffusion, Reflection, Interfaces, Organic light emitting diodes, Control systems, Sensors, Telecommunications, RGB color model, Ceramics, Light sources

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Proceedings Article | 31 March 2012 Open Access

Open Access

Paper

Printed hybrid systems

Pentti Karioja, Jukka-Tapani Mäkinen, Kimmo Keränen, Janne Aikio, Teemu Alajoki, Tuomo Jaakola, Matti Koponen, Antti Keränen, Mikko Heikkinen, Markus Tuomikoski, Riikka Suhonen, Leena Hakalahti, Pälvi Kopola, Jukka Hast, Ralf Liedert, Jussi Hiltunen, Noriyuki Masuda, Antti Kemppainen, Kari Rönkä, Raimo Korhonen

Proceedings Volume 8344, 83440G (2012) https://doi.org/10.1117/12.915206

KEYWORDS: Electronics, Manufacturing, Printing, Light emitting diodes, Organic light emitting diodes, Polymers, Neodymium, Sensors, Solar cells, Assembly equipment

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Proceedings Article | 14 May 2010 Paper

Paper

LTCC-based differential photo acoustic cell for ppm gas sensing

P. Karioja, K. Keränen, K. Kautio, J. Ollila, M. Heikkinen, I. Kauppinen, T. Kuusela, B. Matveev, M. McNie, R. Jenkins, J. Palve

Proceedings Volume 7726, 77260H (2010) https://doi.org/10.1117/12.851854

KEYWORDS: Silicon, Sensors, Interferometers, Photoacoustic spectroscopy, Sapphire, Absorption, Gas sensors, Glasses, Reflectivity, Waveguides

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Silicon MEMS cantilever-based photoacoustic technology allows for the sensing of ultra low gas concentrations with very wide dynamic range. The sensitivity enhancement is achieved with a cantilever microphone system in which the cantilever displacement is probed with an optical interferometer providing a pico-meter resolution. In the gas sensor, the silicon cantilever microphone is placed in a two-chamber differential gas cell. By monitoring differential pressure changes between the two chambers, the differential cell operates as a differential infra-red detector for optical absorption signals through a measurement and reference path. The differential pressure signal is proportional to gas concentration in the optical measurement path. We have designed, implemented and tested a differential photo acoustic gas cell based on Low Temperature Co-fired Ceramic (LTCC) multilayer substrate technology. Standard LTCC technology enables implementation of 2.5D structures including holes, cavities and channels into the electronic substrate. The implemented differential photoacoustic gas cell structure includes two 10 mm long cylindrical cells, diameter of 2.4 mm. Reflectance measurements of the cell showed that reflectivity of the substrate material can be improved by a factor 15 - 90 in the 3 - 8 μm spectral region using gold or silver paste coatings. A transparent window is required in the differential gas cell structure in order to probe the displacement of the silicon cantilever. The transparent sapphire window was sealed to the LTCC substrate using two methods: screen printed Au80/Sn20 solder paste and pre-attached glass solder paste (Diemat DM2700P/H848). Both methods were shown to provide hermetic sealing of sapphire windows to LTCC substrate. The measured He-leak rate for the 10 sealed test samples implemented using glass paste were less than 2.0 ×10^-9 atm×cm³/s, which meets the requirement for the leak rate according to MIL-STD 883. The achieved hermetic level suggests that the proof-of-principle packaging demonstrator paves the way for implementing a novel differential photoacoustic gas cell for a future miniature gas sensor module. The future module consisting of a sample gas cell and immersion lens IR-LEDs together with interferometric probing of the cantilever microphone is expected to be capable of measuring ultra low concentrations of a wide range of gases with their fundamental absorption bands at 3 - 7 μm wavelength, such as CO, CO2 and CH₄.

Proceedings Article | 24 February 2010 Paper

Paper

Differential photo-acoustic gas cell based on LTCC for ppm gas sensing

K. Keränen, K. Kautio, J. Ollila, M. Heikkinen, I. Kauppinen, T. Kuusela, B. Matveev, M. McNie, R. Jenkins, P. Karioja

Proceedings Volume 7607, 760714 (2010) https://doi.org/10.1117/12.841363

KEYWORDS: Sensors, Silicon, Photoacoustic spectroscopy, Interferometers, Sapphire, Gas sensors, Light emitting diodes, Waveguides, Reflectivity, Absorption

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Silicon MEMS cantilever-based photoacoustic technology allows for the sensing of ultra low gas concentrations with very wide dynamic range. The sensitivity enhancement is achieved with a cantilever microphone system in which the cantilever displacement is probed with an optical interferometer providing a pico-meter resolution. In the gas sensor, the silicon cantilever microphone is placed in a two-chamber differential gas cell. By monitoring differential pressure changes between the two chambers, the differential cell operates as a differential infra-red detector for optical absorption signals through a measurement and reference path. The differential pressure signal is proportional to gas concentration in the optical measurement path. We have designed, implemented and tested a differential photo-acoustic gas cell based on Low Temperature Co-fired Ceramic (LTCC) multilayer substrate technology. Standard LTCC technology enables implementation of 2.5D structures including holes, cavities and channels into the electronic substrate. The implemented differential photoacoustic gas cell structure includes two 10 mm long cylindrical cells, diameter of 2.4 mm. Reflectance measurements of the cell showed that reflectivity of the substrate material can be improved by a factor 15 - 90 in the 3 - 8 μm spectral region using gold or silver paste coatings. A transparent window is required in the differential gas cell structure in order to probe the displacement of the silicon cantilever. The transparent sapphire window was sealed to the LTCC substrate using two methods: screen printed Au80/Sn20 solder paste and pre-attached glass solder paste (Diemat DM2700P/H848). Both methods were shown to provide hermetic sealing of sapphire windows to LTCC substrate. The measured He-leak rate for the 10 sealed test samples implemented using glass paste were under 2.0 ×10^-9 atm×cm3/s, which meets the requirement for the leak rate according to MIL-STD 883. The achieved hermeticity level suggests that the proof-of-principle packaging demonstrator paves the way for implementing a novel differential photoacoustic gas cell for a future miniature gas sensor module. The future module consisting of a sample gas cell and immersion lens IR LEDs together with interferometric probing of the cantilever microphone is expected to be capable of measuring ultra low concentrations of a wide range of gases with their fundamental absorption bands at 3 - 7 μm wavelength, such as CO, CO₂ and CH₄.

Proceedings Article | 16 May 2007 Paper

Paper

Inmould integration of a microscope add-on system to a 1.3 Mpix camera phone

Jukka-Tapani Mäkinen, Kimmo Keränen, Jehki Hakkarainen, Mikko Silvennoinen, Timo Salmi, Seppo Syrjälä, Anneli Ojapalo, Marcus Schorpp, Pekka Hoskio, Pentti Karioja

Proceedings Volume 6585, 658507 (2007) https://doi.org/10.1117/12.722741

KEYWORDS: Cameras, Light emitting diodes, Microscopes, Optics manufacturing, Integrated optics, Imaging systems, Optical design, Prototyping, Lens design, Image resolution

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Proceedings Article | 1 May 2007 Paper

Paper

Injection moulding integration of a red VCSEL illuminator module for a hologram reader sensor

Kimmo Keränen, Toni Saastamoinen, Jukka-Tapani Mäkinen, Mikko Silvennoinen, Ilpo Mustonen, Pasi Vahimaa, Timo Jääskeläinen, Ari Lehto, Anneli Ojapalo, Marcus Schorpp, Pekka Hoskio, Pentti Karioja

Proceedings Volume 6585, 658503 (2007) https://doi.org/10.1117/12.722700

KEYWORDS: Vertical cavity surface emitting lasers, Manufacturing, Prototyping, Fiber optic illuminators, Optics manufacturing, Optical alignment, Modeling, Diamond, Assembly tolerances, Packaging

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A red VCSEL illuminator module demonstrator was manufactured by injection moulding integration. A red VCSEL chip was first attached to a simple FR4 substrate, which contains bonding pads and conducting wires for the VCSEL chip attachment and electrical driving. The substrate was then placed as an insert in an injection mould. The VCSEL chip shielding and optics formation was made in a one-step injection moulding process. The used optical thermoplastic in the processing was polycarbonate (PC). The pursued optical function of the single spherical surface attained in the moulding was to collimate the emitted red light (&lgr;=664.5 nm) from the VCSEL chip. The main critical issue related to the manufacturing of the illuminator module in the injection moulding process was the durability of bonding wire contacts. A single 25 &mgr;m diameter gold wire was used in wire bonding in order to create the upper contact to the chip. The lower contact was processed by attaching the chip to the substrate using conductive epoxy. A test series of 20 modules using FR4 substrate materials were produced. The number of fully operative modules was 12 resulting total module yield of 60%. The main reason for a non-operative module was loosening of the bonding wire during the injection moulding process. The bonding wire durability in the moulding process can be improved by using glob-top shielding of the VCSEL device before injection moulding and using a lower holding pressure in the injection moulding process. A diamond turned insert was used in the mould in order to create a high quality lens surface on the top of the VCSEL chip. The tower average length after one iteration round by mould modification was 8.676 &mgr;m, so the measured value was on average 20 &mgr;m larger than nominal value. The measured RMS roughness of the processed lens surface was 5 ... 7 nm and the radius -3.23 ... 3.83 mm. The radius of the lens and the length of the tower varied depending of the used process parameters. The manufactured illumination module can be integrated with a CMOS image matrix sensor in order to form a compact hologram reader system. The injection moulding integration principle seems to be very promising method to manufacture intelligently integrated and cost-effective optoelectronic products according to experience with this demonstrator.

Proceedings Article | 21 April 2006 Paper

Paper

Cost-efficient hermetic fibre pigtailed laser module utilizing passive device alignment on an LTCC substrate

K. Keränen, J. Ollila, J.-T Mäkinen, K. Kautio, P. Korhonen, V. Heikkinen, O. Väätäinen, J. Heilala, P. Karioja

Proceedings Volume 6185, 61850N (2006) https://doi.org/10.1117/12.663753

KEYWORDS: Prototyping, Manufacturing, Tolerancing, Fiber lasers, Optical simulations, Modeling, Monte Carlo methods, Semiconductor lasers, Packaging, Glasses

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A hermetic fibre pigtailed laser module utilizing passive device alignment on a low temperature co-fired ceramics (LTCC) substrate is demonstrated. The 3-dimensional shape of the laminated and fired ceramic substrate provides the necessary alignment structures including holes, grooves and cavities for the laser to fibre coupling. The achieved passive alignment accuracy allows high coupling efficiency realizations of multi-mode fibre pigtailed laser modules. The ceramic substrate is intrinsically hermetic and it opens up a possibility to produce cost efficient hermetic packaging. In our concept hermetic sealing is produced by utilizing Kovar frame, which is soldered to an LTCC substrate. Kovar frame has a hole for fibre feed-trough and a hermetic glass-metal sealing between fibre and frame is processed using glass preform. The heart of the module is a power laser diode chip, which can produce several watts of continuous power. The module, however, can be finally used as a transmitter in a laser pulse time-of-flight distance sensor and in this application it can be overdriven by a factor of 10. This means that the peak optical power in the pulses can be several tens of watts. The laser chip allows this kind of overdriving due to the fact that the duty factor in the operation is only 0.0001 at 2 kHz pulsing frequency. Optical coupling efficiency of the multi-mode laser system was simulated using optical systems simulation software. The nominal coupling efficiency between 210 μm x 1μm stripe laser and 200/220 μm step index fibre (NA=0.22) was 0.65. The simulated coupling efficiency was verified by prototype realization and characterization. The measured average coupling efficiency of the hermetically sealed prototypes was 0.39. The coupling efficiencies of prototypes varied from 0.14 to 0.64. Leak rate of 1 x 10^-7 [atm x cm³/s] was measured in the helium leak tests for the final prototype module, when the module was tested according to MIL-STD-883D method 1014.9 specification. Leak rate for the module using a buffer stripper fibre without a rubber guard tube was 3 x 10^-9 [atm x cm³/s]. The background helium level before and after the tests was less than 3 x 10^-10[atm x cm³/s]. This clearly higher leak rate in the final module leak measurement is mainly due to the absorbed helium to the fibre polymer buffer layer and rubber guard tube in the pressurization process. Measurements show that the implemented module is hermetic. Cost-of-ownership modelling was performed starting from low production volume up to production of 10 million good modules per year. Module production cost was estimated through COO modelling. Modelling forecasted that the module production can be lower than 10 EUR in high volume production.

Proceedings Article | 20 October 2005 Paper

Paper

Implementing a prototyping network for injection moulded imaging lenses in Finland

K. Keränen, J.-T. Mäkinen, E.J. Pääkkönen, M. Koponen, M. Karttunen, J. Hiltunen, P. Karioja

Proceedings Volume 5965, 59651E (2005) https://doi.org/10.1117/12.625118

KEYWORDS: Prototyping, Lens design, Lenses, Manufacturing, Modulation transfer functions, Cameras, Optics manufacturing, Surface finishing, Tolerancing, Surface roughness

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A network for prototyping imaging lenses using injection moulding was established in Finland. The network consists of several academic and industrial partners capable of designing, processing and characterising imaging lenses produced by injection moulding technology. In order to validate the operation of the network a demonstrator lens was produced. The process steps included in the manufacturing were lens specification, designing and modelling, material selection, mould tooling, moulding process simulation, injection moulding and characterisation. A magnifying imaging singlet lens to be used as an add-on in a camera phone was selected as a demonstrator. The design of the add-on lens proved to be somewhat challenging, but a double aspheric singlet lens design fulfilling nearly the requirement specification was produced. In the material selection task the overall characteristics profile of polymethyl methacrylate (PMMA) material was seen to be the most fitting to the pilot case. It is a low cost material with good moulding properties and therefore it was selected as a material for the pilot lens. Lens mould design was performed using I-DEAS and tested by using MoldFlow 3D injection moulding simulation software. The simulations predicted the achievable lens quality in the processing, when using a two-cavity mould design. First cavity was tooled directly into the mould plate and the second cavity was made by tooling separate insert pieces for the mould. Mould material was steel and the inserts were made from Moldmax copper alloy. Parts were tooled with high speed milling machines. Insert pieces were hand polished after tooling. Prototype lenses were injection moulded using two PMMA grades, namely 6N and 7N. Different process parameters were also experimented in the injection moulding test runs. Prototypes were characterised by measuring mechanical dimensions, surface profile, roughness and MTF of the lenses. Characterisations showed that the lens surface RMS roughness was 30-50 nm and the profile deviation was 5 μm from the design at a distance of 0.3 mm from the lens vertex. These manufacturing defects caused that the measured MTF values were lower than designed. The lens overall quality, however, was adequate to demonstrate the concept successfully. Through the implementation of the demonstrator lens we could test effectively different stages of the manufacturing process and get information about process component weight and risk factors and validate the overall performance of the network.

SPIE Journal Paper | 1 September 2005

Laser profilometer module based on a low-temperature cofired ceramic substrate

Veli Heikkinen, Mikko Heikkinen, Kimmo Keranen, Risto Mitikka, Veli-Pekka Putila, Kari Tukkiniemi

OE, Vol. 44, Issue 09, 093603, (September 2005) https://doi.org/10.1117/12.10.1117/1.2047067

KEYWORDS: Electronics, Sensors, Distance measurement, Profilometers, Optics manufacturing, Ceramics, Mechanical engineering, Optoelectronics, Receivers, Vertical cavity surface emitting lasers

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Proceedings Article | 10 June 2004 Paper

Paper

Cost-effective packaging of laser modules using LTCC substrates

Kimmo Keranen, Jukka-Tapani Makinen, Juhani Heilala, Otso Vaatainen, Kari Kautio, Jyrki Ollila, Jarno Petaja, Mikko Karppinen, Veli Heikkinen, Pentti Karioja

Proceedings Volume 5358, (2004) https://doi.org/10.1117/12.528280

KEYWORDS: Tolerancing, Monte Carlo methods, Fiber lasers, Optical simulations, Optical alignment, Packaging, Semiconductor lasers, Manufacturing, Multimode fibers, Optics manufacturing

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Proceedings Article | 22 January 2004 Paper

Paper

Prototyping of miniature plastic imaging lens

Jukka-Tapani Makinen, Janne Aikio, Veli-Pekka Putila, Kimmo Keranen, Pentti Karioja, Timo Kolehmainen, Janne Haavisto

Proceedings Volume 5178, (2004) https://doi.org/10.1117/12.503480

KEYWORDS: Prototyping, Optics manufacturing, Optical design, Optomechanical design, Tolerancing, Manufacturing, Performance modeling, Design for manufacturability, Lens design, Image quality

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SPIE Journal Paper | 1 October 2001

Miniaturization and module integration of an infrared spectrometer

Kimmo Keraenen, Pentti Karioja, Martti Blomberg, Jussi Tenhunen, Outi Rusanen, Harri Kopola

OE, Vol. 40, Issue 10, (October 2001) https://doi.org/10.1117/12.10.1117/1.1406132

KEYWORDS: Silicon, Sensors, Systems modeling, Infrared spectroscopy, Signal detection, Spectroscopy, Infrared radiation, System integration, Adhesives, Geometrical optics

SPIE Journal Paper | 1 April 2000

All-optical fiber optic interface for sensors and actuators

Pentti Karioja, Risto Jurva, Kimmo Keraenen, Kari Tukkiniemi, Jouko Haapamaa, Ari Tervonen, Marja Englund

OE, Vol. 39, Issue 04, (April 2000) https://doi.org/10.1117/12.10.1117/1.602463

KEYWORDS: Waveguides, Sensors, Integrated optics, Photovoltaics, Solar cells, Actuators, Interfaces, Fiber optics sensors, Light emitting diodes, Data transmission

Proceedings Article | 30 April 1999 Paper

Paper

Main characteristics of a miniaturized multipurpose infrared spectrometer

Kimmo Keraenen, Martti Blomberg, Outi Rusanen, Pentti Karioja, Jussi Tenhunen, Harri Kopola, Ari Lehto

Proceedings Volume 3631, (1999) https://doi.org/10.1117/12.348309

KEYWORDS: Spectroscopy, Silicon, Infrared spectroscopy, Mirrors, Infrared radiation, Sensors, Signal detection, Adhesives, Thermography, Modulation

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Proceedings Article | 4 December 1998 Paper

Paper

Accurate manufacturing and production of optoelectronic parts and modules

Tapio Hannula, Pentti Karioja, Kimmo Keraenen, Harri Kopola, Jouko Malinen, Jyrki Ollila

Proceedings Volume 3491, (1998) https://doi.org/10.1117/12.328716

KEYWORDS: Sensors, Silicon, Optoelectronics, Manufacturing, Spectroscopy, Electronics, Packaging, Metals, Mechanics, Glasses

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Proceedings Article | 24 September 1997 Paper

Paper

Electrically tunable NIR spectrometer

Kimmo Keraenen, Pentti Karioja, Outi Rusanen, Jussi Tenhunen, Martti Blomberg, Heikki Lehto

Proceedings Volume 3099, (1997) https://doi.org/10.1117/12.281225

KEYWORDS: Silicon, Spectrometers, Packaging, Manufacturing, Interference filters, Fabry–Perot interferometry, Near infrared, Mirrors, Adhesives, Optical filters

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Showing 5 of 17 publications

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