Mr. Esko Herrala Profile

Esko Herrala

Product Manager at Specim Spectral Imaging Ltd

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Author

Publications (10)

Proceedings Article | 12 May 2011 Paper

Compact high-resolution VIS/NIR hyperspectral sensor

Timo Hyvärinen, Esko Herrala, Wes Procino, Oliver Weatherbee

Proceedings Volume 8032, 80320W (2011) https://doi.org/10.1117/12.887003

KEYWORDS: Imaging systems, Spectrographs, Signal to noise ratio, Hyperspectral imaging, Cameras, Image quality, Sensors, Spectral resolution, Unmanned aerial vehicles, Image resolution

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Proceedings Article | 17 October 2007 Paper

Performance of the Imaging Spectral Signature Instrument (ISSI) breadboard

Uula Kantojärvi, Kai Viherkanto, Ville Aallos, Heikki Saari, Esko Herrala, Bernd Harnisch

Proceedings Volume 6744, 67441V (2007) https://doi.org/10.1117/12.737800

KEYWORDS: LCDs, Modulation, Spectrographs, Optical filters, Data processing, Spectral resolution, Spectrometers, Cameras, Signal to noise ratio, Image sensors

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Proceedings Article | 16 May 2007 Paper

Imaging spectral signature satellite instrument for the real-time identification of ground scenes with a dedicated spectral signature

Uula Kantojärvi, Heikki Saari, Kai Viherkanto, Esko Herrala, Bernd Harnisch

Proceedings Volume 6585, 65850S (2007) https://doi.org/10.1117/12.723557

KEYWORDS: LCDs, Image sensors, Spectral resolution, Modulation, Spectrometers, Spectrographs, Data processing, Modulation transfer functions, Signal to noise ratio, Liquid crystal on silicon

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With hyperspectral pushbroom imaging spectrometers on Earth observation satellites it is possible to detect and identify dedicated ground pixels by their spectral signature. Conventional time consuming on-ground processing performs this selection by processing the measured hyperspectral data cube of the image. The Imaging Spectral Signature Instrument (ISSI) concept combines an optical on-board processing of the hyperspectral data cube with a thresholding algorithm, to identify pixels with a pre-defined and programmable spectral signature, such as water, forest and minerals, in the ground swath. The Imaging Spectral Signature Instrument consists of an imaging telescope, which images an object line on the entrance slit of a first imaging spectrometer, which disperses each pixel of the object line into its spectral content and images the hyperspectral image on the spatial light modulator. This spatial light modulator will be programmed with a spatial transmission or reflection behavior, which is constant along the spatial pixels and along the spectral pixels identical to a filter vector that corresponds to the spectral signature of the searched specific feature. A second inverted spectrometer reimages the by the first spectrometer dispersed and by the spatial light modulator transmitted or reflected flux into a line of pixels. In case the spectral content of the ground scene is identical to the searched signature, the flux traversing or reflecting the spatial light modulator will be maximum. The related pixel can be identified in the final image as a high signal by a threshold discriminator. A component test setup consists of an imaging lens, two Imspector™ spectrographs, a spatial light modulator, which is a programmable transmissible liquid crystal display and a CCD sensor as a detector. A mathematical model was developed for the instrument and its performance was evaluated in order to compare different concept variations. All components were measured and characterized individually, and the results were used in the simulations. Performance was then analyzed by means of radiometric throughput and spatial and spectral resolutions. The simulations were performed at wavelengths of 450 nm to 900 nm. The throughput was found to be between 1% and 4.5%.

Proceedings Article | 1 April 1998 Paper

Direct sight imaging spectrograph: a unique add-in component brings spectral imaging to industrial applications

Timo Hyvarinen, Esko Herrala, Alberto Dall'Ava

Proceedings Volume 3302, (1998) https://doi.org/10.1117/12.304581

KEYWORDS: Spectrographs, Cameras, Imaging systems, Imaging spectroscopy, Calibration, Spectral resolution, Reflectivity, Sensors, Near infrared, RGB color model

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Proceedings Article | 10 February 1995 Paper

Novel fiber optic dental pulp vitalometer

Matti Makiniemi, Harri Kopola, Kyosti Oikarinen, Esko Herrala

Proceedings Volume 2331, (1995) https://doi.org/10.1117/12.201238

KEYWORDS: Teeth, Oxygen, Absorption, Fiber optics sensors, Fiber optics, Receivers, Sensors, Blood, Infrared radiation, Software

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Proceedings Article | 3 January 1995 Paper

Dental pulp vitality measurement based on multiwavelength photoplethysmography

Ville Sarkela, Harri Kopola, Kyosti Oikarinen, Esko Herrala

Proceedings Volume 2631, (1995) https://doi.org/10.1117/12.229169

KEYWORDS: Teeth, Scattering, Absorption, Light scattering, Blood, Signal detection, Reflectivity, Fiber optics, Tissues, Photoplethysmography

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Proceedings Article | 15 November 1994 Paper

Imaging spectrometer for process industry applications

Esko Herrala, Jukka Okkonen, Timo Hyvarinen, Mauri Aikio, Jorma Lammasniemi

Proceedings Volume 2248, (1994) https://doi.org/10.1117/12.194344

KEYWORDS: Spectrographs, Sensors, Imaging spectroscopy, Cameras, Spectroscopy, Chemical elements, Charge-coupled devices, Prisms, CCD cameras, Digital signal processing

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Proceedings Article | 1 February 1994 Paper

Novel spectroscopic techniques for biomedical applications

Timo Hyvarinen, Mauri Aikio, Esko Herrala, Jouko Malinen

Proceedings Volume 2084, (1994) https://doi.org/10.1117/12.167308

KEYWORDS: Near infrared, Light emitting diodes, Sensors, Spectrometers, Spectrographs, Biomedical optics, Optoelectronics, Blood, Tissue optics, Spectroscopes

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Proceedings Article | 1 August 1992 Paper

New technologies for medical color measurements

Elzbieta Marszalec, Harri Kopola, Risto Myllylae, Esko Herrala

Proceedings Volume 1649, (1992) https://doi.org/10.1117/12.60248

KEYWORDS: Optical fibers, Sensors, Visualization, Spectrophotometry, Medicine, Silicon, Fiber optics, Head, Surgery

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Proceedings Article | 1 August 1990 Paper

Miniaturized FT-IR spectrometer for industrial process measurements

Esko Herrala, Pentti Niemela, Tapio Hannula

Proceedings Volume 1266, (1990) https://doi.org/10.1117/12.20261

KEYWORDS: Spectroscopy, Mirrors, Sensors, Spectrometer engineering, Interferometers, Actuators, Moire patterns, Transducers, Beam splitters, FT-IR spectroscopy

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Showing 5 of 10 publications

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