Fabrication of densely patterned micro-arrayed multichannel optical filter mosaic

Lin

Eighth International Symposium on Precision Engineering Measurement and Instrumentation

et al. 2013

In recent decades, multispectral imaging (MSI) has been approved as an effective tool to detect and discriminate targets in industrial application. A narrowband micro-arrayed multispectral filter mosaic (MSFM) based on MSI technology is proposed to miniaturize MSI instrumentation. There are many reasons to believe that this innovation is going to replace the traditional methods of filtering or dispersing light and bring MSI applications to more industrial fields. However, highly integrated micro pieces of MSFM are arranged periodically, and the spectral profiles of two adjacent pieces cause a spectral interference (SI). To express and estimate the extent of SI, an evaluation method is proposed and its feasibility is reported in this paper. Additionally, the ways reducing the extent of SI are suggested.

Section: Methodsmentioning

confidence: 99%

“…At present, MSI technologies use traditional optical filters, e.g., filter wheels, multi-prisms, or the methods of filtering or dispersing light, e.g., computer tomography imaging spectroscopy (CTIS) [4][5][6] . These MSI instrumental systems are bulky, requiring multiple exposures, and need complicated post-image-processing to MSI.…”

Section: Introductionmentioning

confidence: 99%

An evaluation method of a micro-arrayed multispectral filter mosaic

Lin

Eighth International Symposium on Precision Engineering Measurement and Instrumentation

et al. 2013

“…(4) The photoresist remover and Supersonic Cleaner are used to strip the photoresist. (5) Step ( 1) is repeated. (6) The alignment accuracy of 0.5 µm and exposure is retained.…”

Section: Design Of Lift-off Processmentioning

confidence: 99%

“…The presence of photoresist walls prevents film molecules from reaching the desired location, which causes thinner coating layers at boundaries than the middle part of the filter. Therefore, the edge effect is one of the constraining factors that limit the joint width of the dual channel bandpass thin film filter [5]. In addition, since the alignment accuracy of the lithography machine is 0.5 µm, it will cause some alignment error during the second alignment of the lithography.…”

Section: Dual Channel Bandpass Thin Film Filtermentioning

confidence: 99%

Design and Fabrication of an Integrated Dual-Channel Thin-Film Filter for the Mid-Infrared

et al. 2021

Micro-filters fabricated using integration methods is now the trend for multichannel filters in imaging spectrum systems. Traditional multichannel bandpass filters are mainly fabricated separately by multilayered thin films and then glued together. This approach involves the complexity of precision cutting, dicing, and adhesive bonding; therefore, the possibility of miniaturization is quite limited. In this work, a dual channel bandpass thin film filter for the mid-infrared was fabricated by using the lift-off process. The structure of a 4-cavity Fabray–Perot (F-P) type filter was designed and optimized. The bandpass filter over the range 3.55–3.75 µm with full width at half maximum (FWHM) of 274 nm and the bandpass filter over the range 4.85–4.95 µm with FWHM of 246 nm were obtained with a 4.5 µm joint width. The average transmittance of the filters is more than 83.5% and optical density value of the cutoff is 3. The thickness of 3.55–3.75 µm bandpass filter was measured and the thickness error was analyzed. The results show that the thickness error, especially the thickness error of spacer layers, induces the degradations of peak transmission and bandwidth. This kind of mid-infrared filter has important application in space remote sensing, military, and civil fields.

“…Existing multispectral imaging modalities capture spectral content of a scene using narrowband filters (or their combinations) that attenuate light outside specific wavelength ranges [10][11][12][13]. The center wavelengths of the pass bands are designed to match the object's spectral features of interest such as emission, reflection, or absorption peaks that arise from their material and chemical composition [14].…”

mentioning

confidence: 99%

Fourier multispectral imaging

Jia¹,

Ni²,

Sarangan³

et al. 2015

Opt. Express

Current multispectral imaging systems use narrowband filters to capture the spectral content of a scene, which necessitates different filters to be designed for each application. In this paper, we demonstrate the concept of Fourier multispectral imaging which uses filters with sinusoidally varying transmittance. We designed and built these filters employing a single-cavity resonance, and made spectral measurements with a multispectral LED array. The measurements show that spectral features such as transmission and absorption peaks are preserved with this technique, which makes it a versatile technique than narrowband filters for a wide range of multispectral imaging applications.