Thin film measurement system for moving objects based on a laterally distributed linear variable filter spectrometer

Murr, Patrik J.; Wiesent, Benjamin R.; Hirth, Florian; Koch, Alexander W.

doi:10.1063/1.3697750

Cited by 9 publications

(8 citation statements)

References 17 publications

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“…The linear dispersion coefficient of the designed film system is 40 nm/mm, which means that the measured spectrum within a certain sampling range is the average value within the region. The average spectral and spatial effect can deform the measured spectral curve and decrease the transmittance of the central wavelength [24]. The specific transmittance is shown in Equation 3:…”

Section: Resultsmentioning

confidence: 99%

Preparation and Spectrum Characterization of a High Quality Linear Variable Filter

et al. 2018

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To meet the requirements for lightweight, miniaturized dispersive optical systems for space applications, linear variable filters with a high transmittance and spatial dispersion coefficient are proposed. The filters were produced with dual ion beam sputtering, where a single layer thickness variation was achieved with a deposition rate adjustment based on a linear variable correction formula. A linear variable trend matching method was used to correct the film thickness based on the reduction of the mismatch error between two materials: Ta2O5 and SiO2. The influence of the spectral and spatial measuring average effects was addressed by sampling the spot size optimization. This paper presents an all-dielectric linear variable filter that operates between 520 and 1000 nm, with an excellent linear dependence of 40 nm/mm over 12 mm. The linear variable filter possessed a 2.5% bandwidth, and its transmittance was found to be >80% at the central wavelength of the band, with a 0.1% transmittance in the cut-off region. These results indicate great potential for optical devices for space applications, and the developed process has good reproducibility and stability.

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Section: Resultsmentioning

confidence: 99%

Preparation and Spectrum Characterization of a High Quality Linear Variable Filter

et al. 2018

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“…The resolution of the LVF was analyzed in a previous work [12]. Considering the resolution of the LVF and the pixel size of the CMOS 2D sensor array, the system resolution is 1.6% of the LVF center wavelength.…”

Section: Methodsmentioning

confidence: 99%

Static Hyperspectral Fluorescence Imaging of Viscous Materials Based on a Linear Variable Filter Spectrometer

Murr

Schardt

Koch

2013

Sensors

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This paper presents a low-cost hyperspectral measurement setup in a new application based on fluorescence detection in the visible (Vis) wavelength range. The aim of the setup is to take hyperspectral fluorescence images of viscous materials. Based on these images, fluorescent and non-fluorescent impurities in the viscous materials can be detected. For the illumination of the measurement object, a narrow-band high-power light-emitting diode (LED) with a center wavelength of 370 nm was used. The low-cost acquisition unit for the imaging consists of a linear variable filter (LVF) and a complementary metal oxide semiconductor (CMOS) 2D sensor array. The translucent wavelength range of the LVF is from 400 nm to 700 nm. For the confirmation of the concept, static measurements of fluorescent viscous materials with a non-fluorescent impurity have been performed and analyzed. With the presented setup, measurement surfaces in the micrometer range can be provided. The measureable minimum particle size of the impurities is in the nanometer range. The recording rate for the measurements depends on the exposure time of the used CMOS 2D sensor array and has been found to be in the microsecond range.

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“…Even though we designed the width of the LVF to conjugate with the width of a pixel, the LVF is imaged on two rows of pixels due to diffraction and misalignment of imaging system. Considering an arbitrary wavelength λ, the transmittance of the LVF varies along with the length [14], as illustrated in Fig. 4.…”

Section: A Spectrum Imaging Modelmentioning

confidence: 99%

“…During the calibration process, the linear polarizer is rotated from 0 • to 180 • and the imager takes image after every β = 1 • change. The recorded image data at any polarization angle should satisfy (14) and can be rewritten as:…”

Section: B Calibration Of Polarization Coefficientsmentioning

confidence: 99%

Spectrum Reconstruction of the Light-Field Multimodal Imager

Liu

Yuan

2019

IEEE Access

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The multimodal light-field imager can simultaneously capture spectral and polarization characteristic of a two-dimensional target. Due to the diffraction and misalignments of the imaging system, the pixels receive the light passing through different spectral filters and polarizing filters. As a result, the spectral and polarization images constructed by extracting the corresponding filter-pixels contain unwanted information from the other channels. In this paper, we present an imaging model of the spectral and polarimetric radiance for the multimodal light-field imager. Based on the radiance imaging model, calibration schemes are also proposed for determining the spectral response coefficients and polarization response coefficients of the imager. A data reconstruction method based on Tikhonov regularization is proposed to reconstruct the target spectrum with better accuracy. Calibrating and imaging experiments of a prototype are performed and the results confirm the effectiveness of the data reconstruction approach.INDEX TERMS Multimodal light-field imager, hyperspectral imaging, modeling, calibration, data processing.

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Thin film measurement system for moving objects based on a laterally distributed linear variable filter spectrometer

Cited by 9 publications

References 17 publications

Preparation and Spectrum Characterization of a High Quality Linear Variable Filter

Preparation and Spectrum Characterization of a High Quality Linear Variable Filter

Static Hyperspectral Fluorescence Imaging of Viscous Materials Based on a Linear Variable Filter Spectrometer

Spectrum Reconstruction of the Light-Field Multimodal Imager

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