Short-wave infrared (SWIR) spectral imager based on Fabry-Perot interferometer for remote sensing

Abstract

VTT Technical Research Centre of Finland has developed a spectral imager for short-wave infrared (SWIR) wavelength range. The spectral imager is based on a tunable Fabry-Perot interferometer (FPI) accompanied by a commercial InGaAs Camera. The FPI consists of two dielectric coated mirrors separated by a tunable air gap. Tuning of the air gap tunes also transmitted wavelength and therefore FPI acts as a tunable band bass filter. The FPI is piezo-actuated and it uses three piezo-actuators in a closed capacitive feedback loop for air gap tuning. The FPI has multiple order transmission bands, which limit free spectral range. Therefore spectral imager contains two FPI in a stack, to make possible to cover spectral range of 1000 -1700 nm. However, in the first tests imager was used with one FPI and spectral range was limited to 1100-1600 nm. The spectral resolution of the imager is approximately 15 nm (FWHM). Field of view (FOV) across the flight direction is 30 deg. Imaging resolution of the spectral imager is 256 x 320 pixels. The focal length of the optics is 12 mm and F-number is 3.2. This imager was tested in summer 2014 in an unmanned aerial vehicle (UAV) and therefore a size and a mass of the imager were critical. Total mass of the imager is approximately 1200 grams. In test campaign the spectral imager will be used for forest and agricultural imaging. In future, because results of the UAV test flights are promising, this technology can be applied to satellite applications also.

Quantitative Remote Sensing at Ultra-High Resolution with UAV Spectroscopy: A Review of Sensor Technology, Measurement Procedures, and Data Correction Workflows

“…The Rikola HSI records up to 32 individual bands within a second; so, for example, a hypercube with 60 freely selectable individual bands can be captured within a 2-s interval. Recently, a sort-wave infrared (SWIR) range prototype camera was developed, with a spectral range of 0.9-1.7 µm and an image size of 320 × 256 pixels [65,66].…”

Tree Species Recognition in Species Rich Area Using Uav-Borne Hyperspectral Imagery and Stereo-Photogrammetric Point Cloud

“…The SWIR camera consists of the commercial InGaAs camerathe Xenics Bobcat-1.7-320, the imaging optics, the FPI module, control electronics, a battery, a GPS sensor and an irradiance sensor (Mannila et al, 2014). The Xenics Bobcat-1.7-320 is an uncooled Indium Gallium Arsenide (InGaAs) camera, with a spectral band of 0.9-1.7 µm and 320 × 256 pixels, and with a pixel size of 20 × 20 µm.…”

Remote Sensing of 3-D Geometry and Surface Moisture of a Peat Production Area Using Hyperspectral Frame Cameras in Visible to Short-Wave Infrared Spectral Ranges Onboard a Small Unmanned Airborne Vehicle (UAV)

“…The hyperspectral camera developed at the VTT Technical Research Centre of Finland (VTT) [16]- [19] is based on the use of multiple orders of a variable air-gap FPI. When the FPI is placed in front of the sensor, the wavelength of the light passing the FPI is a function of the interferometer air gap (see Fig.…”

“…The FPI technology makes it possible to manufacture a lightweight frame format hyperspectral imager operating on the time-sequential principle. The first prototypes of the FPIbased cameras were operating in the VNIR spectral range [16]- [18], and recently, a short-wave infrared (SWIR) region prototype operating in the spectral range of 1100-1600 nm was presented [19]. The FPI technology has also become commercially available in the VNIR range (http://www.rikola.fi).…”