Ib-Rune Johansen

Non-contact transflectance near infrared imaging for representative on-line sampling of dried salted coalfish (bacalao)

This paper describes a multi-spectral imaging near infrared (NIR) transflectance system developed for on-line determination of crude chemical composition of highly heterogeneous foods and other bio-materials. The system was evaluated for moisture determination in 70 dried salted coalfish (bacalao), an extremely heterogeneous product. A spectral image cube was obtained for each fish and different sub-sampling approaches for spectral extraction and partial least squares calibration were evaluated. The best prediction models obtained correlation R2 values around 0.92 and root mean square error of cross-validation of 0.70%, which is much more accurate than todays traditional manual grading. The combination of non-contact NIR transflectance measurements with spectral imaging allows rather deep penetrating optical sampling as well as large flexibility in spatial sampling patterns and calibration approaches. The technique works well for moisture determination in heterogeneous foods and should, in principle, work for other NIR absorbing compounds such as fat and protein. A part of this study compares the principles of reflectance, contact transflectance and non-contact transflectance with regard to water determination in a set of 20 well-defined dried salted cod samples. Transflectance and non-contact transflectance performed equally well and were superior to reflectance measurements, since the measured light penetrated deeper into the sample.

Micromechanical gratings for visible and near-infrared spectroscopy

We present a micromechanical grating array that acts as a configurable optical filter for low-cost and compact visible and near-infrared spectrometric sensors. We show how the grating array can be used either as a fast scanning monochromator or as a diffractive filter, and that the expected signal-to-noise ratio is approximately equal for the two modes of measurement. The free spectral range of the filter can be matched to a defined spectral measurement region, so that we can optimize the relationship between spectral resolution and electromechanical complexity. We have numerically studied diffraction efficiency and errors in filter shape. Finally, we fabricated a small configurable grating array and present measurement results that demonstrate electrostatic filter modulation.

Photonic-crystal membranes for optical detection of single nano-particles, designed for biosensor application

A sensor designed to detect bio-molecules is presented. The sensor exploits a planar 2D photonic crystal (PC) membrane with sub-micron thickness and through holes, to induce high optical fields that allow detection of nano-particles smaller than the diffraction limit of an optical microscope. We report on our design and fabrication of a PC membrane with a nano-particle trapped inside. We have also designed and built an imaging system where an optical microscope and a CCD camera are used to take images of the PC membrane. Results show how the trapped nano-particle appears as a bright spot in the image. In a first experimental realization of the imaging system, single particles with a radius of 75 nm can be detected.

Optical microphone based on a modulated diffractive lens

The authors present an optical microphone based on a diffractive lens. The distance between the diffractive lens and a reflecting microphone membrane determines the light intensity at the focal point of the lens. With this design, an integrated micromachined microphone transducer can be mass produced at low cost. They describe the sensing principle, calculate the intensity at the focal point, and show how it depends on the membrane position. The authors present results from measurements with a prototype setup which proves the measurement principle and has excellent properties when compared to an expensive condenser microphone.

A novel ultra-planar, long-stroke and low-voltage piezoelectric micromirror

A novel piston-type micromirror with a stroke of up to 20 µm at 20 V formed out of a silicon-on-insulator wafer with integrated piezoelectric actuators was designed, fabricated and characterized. The peak-to-valley planarity of a 2 mm diameter mirror was better than 15 nm, and tip-to-tip tilt upon actuation less than 30 nm. A resonance frequency of 9.8 kHz was measured. Analytical and finite element models were developed and compared to measurements. The design is based on a silicon-on-insulator wafer where the circular mirror is formed out of the handle silicon, thus forming a thick, highly rigid and ultra-planar mirror surface. The mirror plate is connected to a supporting frame through a membrane formed out of the device silicon layer. A piezoelectric actuator made of lead–zirconate–titanate (PZT) thin film is structured on top of the membrane, providing mirror deflection by deformation of the membrane. Two actuator designs were tested: one with a single ring and the other with a double ring providing bidirectional movement of the mirror. The fabricated mirrors were characterized by white light interferometry to determine the static and temporal response as well as mirror planarity.

Calibration of an FT-IR Spectrometer for Ambient Air Monitoring Using PLS

The objective of this work has been to develop a robust calibration method for simultaneous multigas detection with a Fourier transform infrared (FT-IR) system. Calibration models for the identification and quantification of 23 gases in the presence of high concentrations of background gases such as water vapor, carbon dioxide, and methane have been obtained for an FT-IR instrument with 0.7-cm−1 resolution. The calibration models have been tested on a breadboard instrument for trace gas measurement in manned space missions. The results show that FT-IR combined with multivariate methods such as partial least-squares (PLS) and proper pretreatment of the infrared spectra used in calibration is well suited for this purpose. A procedure for baseline drift compensation has been introduced to make the system insensitive to baseline drift and variations in transmittance. This baseline drift compensation also reduces the need for background measurements. Further, a procedure for incorporating a priori information about the instrument signal-to-noise ratio (SNR) and the absorption strength of interfering absorption lines has been developed. Indoor air monitoring and industrial process monitoring are other possible application areas for these techniques. Parts of this work have been performed in a project for the European Space Agency (ESA) in cooperation with Kayser-Threde GmbH and Daimler-Benz Aerospace, Dornier GmbH.

Towards a “Sample-In, Answer-Out” Point-of-Care Platform for Nucleic Acid Extraction and Amplification: Using an HPV E6/E7 mRNA Model System

The paper presents the development of a “proof-of-principle” hands-free and self-contained diagnostic platform for detection of human papillomavirus (HPV) E6/E7 mRNA in clinical specimens. The automated platform performs chip-based sample preconcentration, nucleic acid extraction, amplification, and real-time fluorescent detection with minimal user interfacing. It consists of two modular prototypes, one for sample preparation and one for amplification and detection; however, a common interface is available to facilitate later integration into one single module. Nucleic acid extracts (n = 28) from cervical cytology specimens extracted on the sample preparation chip were tested using the PreTect HPV-Proofer and achieved an overall detection rate for HPV across all dilutions of 50%–85.7%. A subset of 6 clinical samples extracted on the sample preparation chip module was chosen for complete validation on the NASBA chip module. For 4 of the samples, a 100% amplification for HPV 16 or 33 was obtained at the 1 : 10 dilution for microfluidic channels that filled correctly. The modules of a “sample-in, answer-out” diagnostic platform have been demonstrated from clinical sample input through sample preparation, amplification and final detection.

New method for testing hermeticity of silicon sensor structures

Abstract A method for testing the hermeticity of different wafer-bonding processes used in silicon sensor devices is proposed. The method is based on measuring the gas concentration in a sealed silicon cavity by Fourier-transform infrared spectroscopy (FTIR). The gas concentration and thereby the leakage into the sealed silicon cavity after external pressure exposure is measured by FTIR absorbance. In this work the method has been evaluated by measuring a test silicon cavity filled with a controlled amount of test gas. N 2 O is evaluated as the test gas in this experiment.

Dedicated spectrometers based on diffractive optics: Design, modelling and evaluation

Abstract The described design of diffractive optical elements for low cost IR-spectrometers gives a built-in wavelength reference and allows ‘spectral arithmetic’ to be implemented in the optical performance of the DOE. The diffractive element combines the function of the lenses and the grating and eliminates the need for alignment of those components in the standard scanned grating spectrometer design. The element gives out a set of foci, each with one spectral component, which are scanned across a detector, thus relaxing the demands for scan angle control. It can thus be regarded as an alternative solution to a beam splitter and band pass filter instrument. Software tools have been designed to ease the adaptation of the design to different applications. To model the performance of the spectrometers we have implemented a scalar Rayleigh-Sommerfeldt diffraction model. The gold-coated elements are produced by injection moulding using a compact disc (CD) moulding technique and mould inlays mastered by e-beam lithography. The optimized selection of wavelength bands and the classification of the measured signal use a combination of principal component analysis and robust statistical methods. Typical applications will be material characterization of recycled plastics and gas monitoring. Spectrometers for two different applications have been built and tested. Comparisons between the design goals and the measured performance have been made and show good agreements.

New Method For Testing Hermeticity Of Silicon Sensor Structures

A method for testing hermeticity of different wafer bonding processes used in silicon sensor devices is proposed. The method is based on measuring the gas concentration in a sealed silicon cavity by Fourier Transform Infrared spectroscopy (FTIR). The gas concentration and thereby the leakage into the sealed silicon cavity after external pressure exposure is measured by FTIR-absorbance. In this work the method was evaluated by measuring a test silicon cavity filled with a controlled amount of test gas. N/sub 2/O as testing gas was evaluated in this experiment.