An infrared (IR) temperature measurement system consists of not only a sensor module and electron... more An infrared (IR) temperature measurement system consists of not only a sensor module and electronics, but also an optomechanical system that guides IR radiation onto the sensor. The geometry and emissivity of the parts affects the reading, if the detector sees not only the target but parts of the measuring system itself. In normal industrial applications, the optics is designed so that the surfaces stabilize to the same temperature as the sensor. This allows the error caused by the device temperature to be easily calibrated away. The correction is valid for stationary conditions and usually near the calibration temperature, which is typically at room temperature. However, we show that if the sensor is embedded into a mobile (hand-held) device which has heat sources, such as power electronics, the normal conditions are no longer valid and the calibration fails. In order to improve infrared temperature sensing for mobile devices, the optics concept was studied and detailed design was performed. In addition, the optics performance was modelled and verified by measurement sensor prototyping. A calibration procedure noticing ope~a~ional temperature variations was applied. The repeatabIlIty of the implemented IR temperature sensor using on a correct transferred calibration curve was better than ±0.5°C in an operational temperature range from + 12.6 to +49.3°C and target range from + 10 to +90°C.
56th Electronic Components and Technology Conference 2006, 2006
Abstract We have studied technologies to design and fabricate high-bit-rate chip-to-chip optical ... more Abstract We have studied technologies to design and fabricate high-bit-rate chip-to-chip optical interconnects on printed circuit boards (PCBs) using board-embedded polymer waveguides and surface-mounted component packages or modules. In order to demonstrate the ...
A microscope add-on device to a 1.3 Mpix camera phone was selected as a demonstrator system for t... more A microscope add-on device to a 1.3 Mpix camera phone was selected as a demonstrator system for testing inmould integration of electronic substrates and plastic optics. Optical design of the device was quite challenging due to the fact that illumination system needed to be integrated with a double aspheric singlet lens structure as a single optical piece. The designed imaging lens resolution was adequate to resolve 10 mum features with a mobile phone camera. In the illumination optics the light from LEDs embedded into the plastic structure was collected and guided to the surface that was imaged. Illumination was designed to be uniform and adequately bright to achieve high resolution images with the camera phone. Lens mould design was tested by using injection moulding simulation software. The critical mould optical surfaces were designed as separate insert parts. Final shapes producing lens surfaces were tooled by diamond turning on nickel coatings. Electronic circuit board inserts with bonded bare LED chips and packaged SMD LEDs were assembled to the mould and then overmoulded with optical grade PMMA. Experiences proved that inmould integration of electronic substrates, bare LED chips and high resolution imaging optics in injection-compression moulding process is feasible. The yield of embedded packaged and also bare chip components was close to 100% after the right injection moulding process parameters were found. Prototype add-on system was characterized by testing the imaging properties of the device with a camera phone.
A novel add-on device to a mobile camera phone has been developed. The prototype system contains ... more A novel add-on device to a mobile camera phone has been developed. The prototype system contains both laser and LED illumination as well as imaging optics. Main idea behind the device is to have a small printable diffractive ROM (Read Only Memory) element, which can be read by illuminating it with a laser-beam and recording the resulting datamatrix pattern with
The modeling, realization and characterization of photonic module based on the use of Low Tempera... more The modeling, realization and characterization of photonic module based on the use of Low Temperature Co-fired Ceramics (LTCC) technology is reported. The 3D modeling of the system provides possibility to optimize structures, materials and components in order to achieve optimal performance for the final product and still maintain reasonably low fabrication costs. The cost-effectiveness in the product can be further
Micro-Optics, VCSELs, and Photonic Interconnects II: Fabrication, Packaging, and Integration, 2006
Technologies to design and fabricate high-bit-rate chip-to-chip optical interconnects on printed ... more Technologies to design and fabricate high-bit-rate chip-to-chip optical interconnects on printed wiring boards (PWB) are studied. The aim is to interconnect surface-mounted component packages or modules using board-embedded optical waveguides. In order to demonstrate the developed technologies, a parallel optical interconnect was integrated on a standard FR4-based PWB. It consists of 4-channel BGA-mounted transmitter and receiver modules as well as
Micro-Optics, VCSELs, and Photonic Interconnects, 2004
Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is stud... more Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is studied. The aim is a hybrid optical-electrical board including both electrical wiring and embedded polymer waveguides. Robust optical coupling between the waveguide and the emitter/detector should be achieved by the use of automated pick-and-place assembly. Different coupling schemes were analyzed by combining non-sequential ray tracing with Monte-Carlo tolerance simulation of misalignments. The simulations demonstrate that, with optimized optomechanical structures and with very low loss waveguides, it is possible to achieve acceptable total path loss and yield with the accuracy of automated assembly. A technical demonstrator was designed and realized to allow testing of embedded interconnects based on three different kind of optical coupling schemes: butt-coupling, and couplings based on micro-lens arrays and on microball lenses. They were implemented with PIN and flip-chip-VCSEL arrays as well as 10-Gb/s/channel electronics onto LTCC-based (low-temperature co-fired ceramic) transmitter and receiver modules, which were surface mounted on high-speed PWBs. The polymer waveguides were on separate FR-4 boards to allow testing and characterization of alignment tolerances with different waveguides. With micro-lens array transmitter, the measured tolerances (±10 µm) were dominated by the thickness of the waveguides.
Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is stud... more Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is studied. The aim is a hybrid optical-electrical board including both electrical wiring and embedded polymer waveguides. Robust optical coupling between the waveguide and the emitter/detector should be achieved by the use of automated pick-and-place assembly. Different coupling schemes were analyzed by combining non-sequential ray tracing with Monte-Carlo tolerance simulation of misalignments. The simulations demonstrate that, with optimized optomechanical structures and with very low loss waveguides, it is possible to achieve acceptable total path loss and yield with the accuracy of automated assembly. A technical demonstrator was designed and realized to allow testing of embedded interconnects based on three different kind of optical coupling schemes: butt-coupling, and couplings based on micro-lens arrays and on micro-ball lenses. They were implemented with PIN and flip-chip-VCSEL arrays as well as 10-Gb/s/channel electronics onto LTCC-based (low-temperature co-fired ceramic) transmitter and receiver modules, which were surface mounted on high-speed PWBs. The polymer waveguides were on separate FR-4 boards to allow testing and characterization of alignment tolerances with different waveguides. With micro-lens array transmitter, the measured tolerances (+/-10 mum) were dominated by the thickness of the waveguides.
3rd Electronics System Integration Technology Conference ESTC, 2010
The dominant technology for manufacturing backlight illumination structure (BLIS) is typically ba... more The dominant technology for manufacturing backlight illumination structure (BLIS) is typically based on the use of individually packaged surface mount device light emitting diodes (LEDs) and special light guide plate (LGP) and diffuser films. The prevailing BLIS package, however, contains several separate diffuser films, which results in a thick and costly structure. In addition, the light coupling from LED to the LGP is sensitive to alignment errors causing nonuniform and inefficient illumination. We have demonstrated a novel hot laminated packaging structure for backlighting solutions, which is based on inorganic LED chips and multilayer polymer structure. The main advantages of the implemented system compared to the traditional light guiding system are easy optical coupling with high efficiency in an integrated and thin package. The performed designs of 3 × 3, 5 × 5, and 5 × 7 LED chip matrices, verified by test structure implementations and characterizations, showed that the final thickness of the BLIS depends on the required uniformity of illumination, allowed LED device pitch and efficiency of the diffuser. The final BLIS demonstrator size was 50 × 75 mm 2 consisting of six 25 × 25 mm 2 modules. Each module consisting 5 × 5 LED devices resulting in total number of 150 LED devices with 5-mm pitch. The measured key characteristics of the demonstrator were as follows: average brightness 11.600 cd/m 2 (I LED = 2 mA), luminous efficiency 22 lm/W, color temperature 5550 K, commission on illumination values (x = 0.331, y = 0.411), Color Rendering Index ≥ 70, and total power conversion efficiency of 6.3%. The combination of the developed MATLAB performance simulation tool and cost-of-ownership cost evaluation tool enables us to estimate the manufacturing cost of a specific BLIS element against the required performance, assisting decision-making in different applications and specific individual customer cases.
A red VCSEL illuminator module demonstrator was manufactured by injection moulding integration. A... more 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
Optical Modeling and Performance Predictions, 2004
In this paper, an imaging system simulation tool is presented. With the tool, it is possible to s... more In this paper, an imaging system simulation tool is presented. With the tool, it is possible to simulate the performance (quality) of an imaging system. Furthermore, the system allows optimization of the lens system for a given image sensor. Experiments have shown that the tool is useful in actual lens design.
Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is stud... more Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is studied. The aim is a hybrid optical-electrical board including both electrical wiring and embedded polymer waveguides. Robust optical coupling between the waveguide and the emitter/detector should be achieved by the use of automated pick-and-place assembly. Different coupling schemes were analyzed by combining non-sequential ray tracing with Monte-Carlo tolerance simulation of misalignments. The simulations demonstrate that, with optimized optomechanical structures and with very low loss waveguides, it is possible to achieve acceptable total path loss and yield with the accuracy of automated assembly. A technical demonstrator was designed and realized to allow testing of embedded interconnects based on three different kind of optical coupling schemes: butt-coupling, and couplings based on micro-lens arrays and on micro-ball lenses. They were implemented with PIN and flip-chip-VCSEL arrays a...
An infrared (IR) temperature measurement system consists of a sensor module and electronics as we... more An infrared (IR) temperature measurement system consists of a sensor module and electronics as well as an optomechanical system that guides IR radiation onto the sensor. The geometry and emissivity of the optomechanics can affect the temperature reading. We show how the traditional optomechanical design of the IR temperature measuring systems produce inaccurate results when used in handheld mobile devices. When the mobile device is not thermally stable and the measured targets are significantly colder than the device, the measurement error can be several degrees. Our new optomechanical design was optimised for handheld mobile use, and its optics performance was modelled and verified by prototyping. The temperature measurement and sensor calibration is based on only two signals, namely the thermopile and thermistor voltages of the IR detector. This is a very attractive method in high-volume consumer products because no additional components are needed to improve the measurement repeatability. The attainable repeatability of the implemented IR temperature sensor on a correct transferred calibration curve was better than ±0.5 • C in an operational temperature range from +13 to +49 • C and target range from +10 to +90 • C.
Free-space IR transmission provides high bandwidth and good security with small-sized and low-cos... more Free-space IR transmission provides high bandwidth and good security with small-sized and low-cost links, for instance, for high-bit-rate wireless LANs. Some robustness against shadowing is achieved using diffuse channels, but disadvantages are high path loss and multipath propagation. We use ray-trace simulation software to analyze IR channels in realistic office rooms. Simulations are performed to test the methods and to
High-speed intrasatellite networks are needed to interconnect units such as synthetic aperture ra... more High-speed intrasatellite networks are needed to interconnect units such as synthetic aperture radars, high-resolution cameras, and fast image-compression processors that produce data beyond gigabits per second. We have developed a fiberoptic link, named SpaceFibre, which operates up to 3.125 Gb/s and is compatible with the existing SpaceWire network. The link provides symmetrical, bidirectional, full-duplex, and point-topoint communication. It employs 850-nm vertical-cavity surface emitting lasers, radiation-hardened laser-optimized 50/125 µm graded-index fibers, and GaAs p-i-n photo diodes. The transceiver electronics is realized using a multilayer-ceramic-substrate technology that enables the passive alignment of optical fibers to active devices. The SpaceFibre link demonstrator was tested to transfer data at 2.5 Gb/s over 100 m with a bit error rate of less than 1.3 · 10 −14 . Fiber-pigtailed modules were stressed with temperature variations from −40 • C to +85 • C, vibrations up to 30 g, and mechanical shocks up to 3900 g. The test results of 20 modules show that the SpaceFibre link is a promising candidate for the upcoming high-speed intrasatellite networks.
An infrared (IR) temperature measurement system consists of not only a sensor module and electron... more An infrared (IR) temperature measurement system consists of not only a sensor module and electronics, but also an optomechanical system that guides IR radiation onto the sensor. The geometry and emissivity of the parts affects the reading, if the detector sees not only the target but parts of the measuring system itself. In normal industrial applications, the optics is designed so that the surfaces stabilize to the same temperature as the sensor. This allows the error caused by the device temperature to be easily calibrated away. The correction is valid for stationary conditions and usually near the calibration temperature, which is typically at room temperature. However, we show that if the sensor is embedded into a mobile (hand-held) device which has heat sources, such as power electronics, the normal conditions are no longer valid and the calibration fails. In order to improve infrared temperature sensing for mobile devices, the optics concept was studied and detailed design was performed. In addition, the optics performance was modelled and verified by measurement sensor prototyping. A calibration procedure noticing ope~a~ional temperature variations was applied. The repeatabIlIty of the implemented IR temperature sensor using on a correct transferred calibration curve was better than ±0.5°C in an operational temperature range from + 12.6 to +49.3°C and target range from + 10 to +90°C.
56th Electronic Components and Technology Conference 2006, 2006
Abstract We have studied technologies to design and fabricate high-bit-rate chip-to-chip optical ... more Abstract We have studied technologies to design and fabricate high-bit-rate chip-to-chip optical interconnects on printed circuit boards (PCBs) using board-embedded polymer waveguides and surface-mounted component packages or modules. In order to demonstrate the ...
A microscope add-on device to a 1.3 Mpix camera phone was selected as a demonstrator system for t... more A microscope add-on device to a 1.3 Mpix camera phone was selected as a demonstrator system for testing inmould integration of electronic substrates and plastic optics. Optical design of the device was quite challenging due to the fact that illumination system needed to be integrated with a double aspheric singlet lens structure as a single optical piece. The designed imaging lens resolution was adequate to resolve 10 mum features with a mobile phone camera. In the illumination optics the light from LEDs embedded into the plastic structure was collected and guided to the surface that was imaged. Illumination was designed to be uniform and adequately bright to achieve high resolution images with the camera phone. Lens mould design was tested by using injection moulding simulation software. The critical mould optical surfaces were designed as separate insert parts. Final shapes producing lens surfaces were tooled by diamond turning on nickel coatings. Electronic circuit board inserts with bonded bare LED chips and packaged SMD LEDs were assembled to the mould and then overmoulded with optical grade PMMA. Experiences proved that inmould integration of electronic substrates, bare LED chips and high resolution imaging optics in injection-compression moulding process is feasible. The yield of embedded packaged and also bare chip components was close to 100% after the right injection moulding process parameters were found. Prototype add-on system was characterized by testing the imaging properties of the device with a camera phone.
A novel add-on device to a mobile camera phone has been developed. The prototype system contains ... more A novel add-on device to a mobile camera phone has been developed. The prototype system contains both laser and LED illumination as well as imaging optics. Main idea behind the device is to have a small printable diffractive ROM (Read Only Memory) element, which can be read by illuminating it with a laser-beam and recording the resulting datamatrix pattern with
The modeling, realization and characterization of photonic module based on the use of Low Tempera... more The modeling, realization and characterization of photonic module based on the use of Low Temperature Co-fired Ceramics (LTCC) technology is reported. The 3D modeling of the system provides possibility to optimize structures, materials and components in order to achieve optimal performance for the final product and still maintain reasonably low fabrication costs. The cost-effectiveness in the product can be further
Micro-Optics, VCSELs, and Photonic Interconnects II: Fabrication, Packaging, and Integration, 2006
Technologies to design and fabricate high-bit-rate chip-to-chip optical interconnects on printed ... more Technologies to design and fabricate high-bit-rate chip-to-chip optical interconnects on printed wiring boards (PWB) are studied. The aim is to interconnect surface-mounted component packages or modules using board-embedded optical waveguides. In order to demonstrate the developed technologies, a parallel optical interconnect was integrated on a standard FR4-based PWB. It consists of 4-channel BGA-mounted transmitter and receiver modules as well as
Micro-Optics, VCSELs, and Photonic Interconnects, 2004
Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is stud... more Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is studied. The aim is a hybrid optical-electrical board including both electrical wiring and embedded polymer waveguides. Robust optical coupling between the waveguide and the emitter/detector should be achieved by the use of automated pick-and-place assembly. Different coupling schemes were analyzed by combining non-sequential ray tracing with Monte-Carlo tolerance simulation of misalignments. The simulations demonstrate that, with optimized optomechanical structures and with very low loss waveguides, it is possible to achieve acceptable total path loss and yield with the accuracy of automated assembly. A technical demonstrator was designed and realized to allow testing of embedded interconnects based on three different kind of optical coupling schemes: butt-coupling, and couplings based on micro-lens arrays and on microball lenses. They were implemented with PIN and flip-chip-VCSEL arrays as well as 10-Gb/s/channel electronics onto LTCC-based (low-temperature co-fired ceramic) transmitter and receiver modules, which were surface mounted on high-speed PWBs. The polymer waveguides were on separate FR-4 boards to allow testing and characterization of alignment tolerances with different waveguides. With micro-lens array transmitter, the measured tolerances (±10 µm) were dominated by the thickness of the waveguides.
Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is stud... more Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is studied. The aim is a hybrid optical-electrical board including both electrical wiring and embedded polymer waveguides. Robust optical coupling between the waveguide and the emitter/detector should be achieved by the use of automated pick-and-place assembly. Different coupling schemes were analyzed by combining non-sequential ray tracing with Monte-Carlo tolerance simulation of misalignments. The simulations demonstrate that, with optimized optomechanical structures and with very low loss waveguides, it is possible to achieve acceptable total path loss and yield with the accuracy of automated assembly. A technical demonstrator was designed and realized to allow testing of embedded interconnects based on three different kind of optical coupling schemes: butt-coupling, and couplings based on micro-lens arrays and on micro-ball lenses. They were implemented with PIN and flip-chip-VCSEL arrays as well as 10-Gb/s/channel electronics onto LTCC-based (low-temperature co-fired ceramic) transmitter and receiver modules, which were surface mounted on high-speed PWBs. The polymer waveguides were on separate FR-4 boards to allow testing and characterization of alignment tolerances with different waveguides. With micro-lens array transmitter, the measured tolerances (+/-10 mum) were dominated by the thickness of the waveguides.
3rd Electronics System Integration Technology Conference ESTC, 2010
The dominant technology for manufacturing backlight illumination structure (BLIS) is typically ba... more The dominant technology for manufacturing backlight illumination structure (BLIS) is typically based on the use of individually packaged surface mount device light emitting diodes (LEDs) and special light guide plate (LGP) and diffuser films. The prevailing BLIS package, however, contains several separate diffuser films, which results in a thick and costly structure. In addition, the light coupling from LED to the LGP is sensitive to alignment errors causing nonuniform and inefficient illumination. We have demonstrated a novel hot laminated packaging structure for backlighting solutions, which is based on inorganic LED chips and multilayer polymer structure. The main advantages of the implemented system compared to the traditional light guiding system are easy optical coupling with high efficiency in an integrated and thin package. The performed designs of 3 × 3, 5 × 5, and 5 × 7 LED chip matrices, verified by test structure implementations and characterizations, showed that the final thickness of the BLIS depends on the required uniformity of illumination, allowed LED device pitch and efficiency of the diffuser. The final BLIS demonstrator size was 50 × 75 mm 2 consisting of six 25 × 25 mm 2 modules. Each module consisting 5 × 5 LED devices resulting in total number of 150 LED devices with 5-mm pitch. The measured key characteristics of the demonstrator were as follows: average brightness 11.600 cd/m 2 (I LED = 2 mA), luminous efficiency 22 lm/W, color temperature 5550 K, commission on illumination values (x = 0.331, y = 0.411), Color Rendering Index ≥ 70, and total power conversion efficiency of 6.3%. The combination of the developed MATLAB performance simulation tool and cost-of-ownership cost evaluation tool enables us to estimate the manufacturing cost of a specific BLIS element against the required performance, assisting decision-making in different applications and specific individual customer cases.
A red VCSEL illuminator module demonstrator was manufactured by injection moulding integration. A... more 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
Optical Modeling and Performance Predictions, 2004
In this paper, an imaging system simulation tool is presented. With the tool, it is possible to s... more In this paper, an imaging system simulation tool is presented. With the tool, it is possible to simulate the performance (quality) of an imaging system. Furthermore, the system allows optimization of the lens system for a given image sensor. Experiments have shown that the tool is useful in actual lens design.
Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is stud... more Integration of high-speed parallel optical interconnects into printed wiring boards (PWB) is studied. The aim is a hybrid optical-electrical board including both electrical wiring and embedded polymer waveguides. Robust optical coupling between the waveguide and the emitter/detector should be achieved by the use of automated pick-and-place assembly. Different coupling schemes were analyzed by combining non-sequential ray tracing with Monte-Carlo tolerance simulation of misalignments. The simulations demonstrate that, with optimized optomechanical structures and with very low loss waveguides, it is possible to achieve acceptable total path loss and yield with the accuracy of automated assembly. A technical demonstrator was designed and realized to allow testing of embedded interconnects based on three different kind of optical coupling schemes: butt-coupling, and couplings based on micro-lens arrays and on micro-ball lenses. They were implemented with PIN and flip-chip-VCSEL arrays a...
An infrared (IR) temperature measurement system consists of a sensor module and electronics as we... more An infrared (IR) temperature measurement system consists of a sensor module and electronics as well as an optomechanical system that guides IR radiation onto the sensor. The geometry and emissivity of the optomechanics can affect the temperature reading. We show how the traditional optomechanical design of the IR temperature measuring systems produce inaccurate results when used in handheld mobile devices. When the mobile device is not thermally stable and the measured targets are significantly colder than the device, the measurement error can be several degrees. Our new optomechanical design was optimised for handheld mobile use, and its optics performance was modelled and verified by prototyping. The temperature measurement and sensor calibration is based on only two signals, namely the thermopile and thermistor voltages of the IR detector. This is a very attractive method in high-volume consumer products because no additional components are needed to improve the measurement repeatability. The attainable repeatability of the implemented IR temperature sensor on a correct transferred calibration curve was better than ±0.5 • C in an operational temperature range from +13 to +49 • C and target range from +10 to +90 • C.
Free-space IR transmission provides high bandwidth and good security with small-sized and low-cos... more Free-space IR transmission provides high bandwidth and good security with small-sized and low-cost links, for instance, for high-bit-rate wireless LANs. Some robustness against shadowing is achieved using diffuse channels, but disadvantages are high path loss and multipath propagation. We use ray-trace simulation software to analyze IR channels in realistic office rooms. Simulations are performed to test the methods and to
High-speed intrasatellite networks are needed to interconnect units such as synthetic aperture ra... more High-speed intrasatellite networks are needed to interconnect units such as synthetic aperture radars, high-resolution cameras, and fast image-compression processors that produce data beyond gigabits per second. We have developed a fiberoptic link, named SpaceFibre, which operates up to 3.125 Gb/s and is compatible with the existing SpaceWire network. The link provides symmetrical, bidirectional, full-duplex, and point-topoint communication. It employs 850-nm vertical-cavity surface emitting lasers, radiation-hardened laser-optimized 50/125 µm graded-index fibers, and GaAs p-i-n photo diodes. The transceiver electronics is realized using a multilayer-ceramic-substrate technology that enables the passive alignment of optical fibers to active devices. The SpaceFibre link demonstrator was tested to transfer data at 2.5 Gb/s over 100 m with a bit error rate of less than 1.3 · 10 −14 . Fiber-pigtailed modules were stressed with temperature variations from −40 • C to +85 • C, vibrations up to 30 g, and mechanical shocks up to 3900 g. The test results of 20 modules show that the SpaceFibre link is a promising candidate for the upcoming high-speed intrasatellite networks.
Uploads
Papers by Jukka-Tapani Makinen