Recently developed tunable MEMS Fabry- Perot interferometers based on Ag thin-film mirrors have enabled building highly miniaturized spectral imagers covering almost the complete VNIR wavelength range. The level of miniaturization required by modern smartphone industry has created extremely compact, high performance electronics and camera technologies and by utilizing these technologies together with the novel MEMS FPI’s, it is possible to create extremely compact spectral imagers while still achieving good performance. This paper presents a spectral imager design that can be fit inside an envelope of 1 cubic inch (25.4 × 25.4 × 25.4 mm3 ) and it will be capable of recording images at freely selectable wavelengths within the range of ca. 650 nm - 950 nm. The imager field of view is ca. 12.5° × 10° and the image size is 640 × 512 pixels. Nominally the imager will be focused from ca. 0.5 m to infinity, but with additional optics it is possible to use the imager as a microscope. The compact size of the imager allows the easy integration to almost any available platform, including small drones, nanosatellites or planetary rovers, where small size is essential. It is also possible to integrate the imager to handheld devices, so the potential field of applications will be extensive.
The Fabry-Perot interferometers (FPI) are essential components of many hyperspectral imagers (HSI). While the Piezo-FPI (PFPI) are still very relevant in low volume, high performance applications, the tunable MOEMS FPI (MFPI) technology enables volume-scalable manufacturing, thus having potential to be a major game changer with the advantages of low costs and miniaturization. However, before a FPI can be utilized, it must be integrated with matching optical assembly, driving electronics and imaging sensor. Most importantly, the whole HSI system must be calibrated to account for wide variety of unwanted physical and environmental effects, that significantly influence quality of hyperspectral data. Another challenge of hyperspectral imaging is the applicability of produced raw data. Typically it is relatively low and an application specific software is necessary to turn data into meaningful information. A versatile analysis tools can help to breach the gap between raw hyperspectral data and the user application. This paper presents a novel HSI hardware platform that is compatible with both MFPI and PFPI technologies. With an MFPI installed, the new imager can have operating range of λ = 600 - 1000 nm with FWHM of 15 - 25 nm and tuning speed of < 2 ms. Similar to previous imager in Ref. 1, the new integrated HSI system is well suited for mobile and cloud based applications due to its small dimensions and connectivity options. In addition to new hardware platform, a new hyperspectral imaging analysis software was developed. The new software used in conjunction with the HSI provides a platform for spectral data acquisition and a versatile analysis tool for a processing raw data into more meaningful information.
Small, tunable MEMS Fabry-Perot interferometer (FPIs) have recently been demonstrated to enable hyperspectral imaging in mobile devices, so far using Bragg reflector mirror technologies, which however limit the device tuning range. This paper presents the realization of a novel MEMS FPI structure based on Ag thin film mirrors (AgMFPI), which allows tuning the entire visible - very near infrared (VNIR) wavelength range (for example 450 - 900 nm) with one single component. The characterized transmission of the components is 12 - 45% with full-width-half-maximum values (FWHM) between 11 - 18 nm using 2 mm optical aperture, while using 3 mm optical aperture results in FWHM values of 12 - 20 nm. A very compact hyperspectral imager can thus be built to cover this spectra by combining this AgMFPI and a typical RGB type of image sensor.
This paper presents a novel miniaturized hand-held hyperspectral imager for VNIR range of λ = 600 – 900 nm based on MEMS Fabry-Perot interferometer (MFPI) technology. In recent years, tunable MFPI optical filters have been utilized to demonstrate sensors for mobile applications, including CO2 smartphone sensor for mid infra-red region and hyperspectral iPhone for visible spectrum. This hand-held sensor module targets the VNIR range in order to enable food sensing, while utilizing low-cost camera technology to enable potential volume scalability for future sensing applications. The sensor module is wirelessly connected to a mobile device, which enables further application algorithms development and cloudbased solutions.