Hyperspectral sensing system and processing methods for hyperspectral data
A hyperspectral sensing device may include an optical collector configured to collect light and to transfer the collected light to a sensor having spectral resolution sufficient for sensing hyperspectral data. In some examples, the sensor comprises a compact spectrometer. The device further comprises a power supply, an electronics module, and an input/output hub enabling the device to transmit acquired data (e.g., to a remote server). In some examples, a plurality of hyperspectral sensing devices are deployed as a network to acquire data over a relatively large area. Methods are disclosed for performing dark-current calibration and/or radiometric calibration on data obtained by the hyperspectral sensing device, and/or another suitable device. Data obtained by the device may be represented in a functional basis space, enabling computations that utilize all of the hyperspectral data without loss of information.
1. A method for measuring a dark-current-corrected spectrum, the method comprising:
measuring a first spectrum of light using a photosensitive detector having a first integration time;
measuring a plurality of second spectra using the photosensitive detector, each of the second spectra corresponding to a different integration time of the photosensitive detector;
estimating a respective dark-current contribution for each of the second spectra based on a respective lowest value of each of the second spectra;
computing a first estimated dark-current contribution for the first spectrum based on the estimated dark-current contributions for the second spectra and the first integration time; and
subtracting the first estimated dark-current contribution from each value of the first spectrum to produce a dark-current-corrected spectrum.
2. The method of claim 1 , wherein computing the first estimated dark-current contribution includes obtaining a quantitative function predicting dark-current contributions based on input integration times, and using the quantitative function to predict the first estimated dark-current contribution based on the first integration time.
3. The method of claim 1 , wherein the first spectrum and the plurality of second spectra are all measured within an interval of time, and the photosensitive detector remains deployed at an outdoor location during the interval of time.
4. The method of claim 3 , wherein the plurality of second spectra comprises a subset of a plurality of third spectra measured during the interval of time, the plurality of second spectra being selected from the plurality of third spectra based on respective environmental conditions corresponding to each of the second spectra.
5. The method of claim 4 , wherein the environmental conditions corresponding to each of the second spectra are identified based at least partially on data measured by one or more auxiliary sensors disposed in a device containing the photosensitive detector.
6. The method of claim 3 , wherein the photosensitive detector comprises a spectrometer having a spectral resolution of 20 nanometers or better.
7. The method of claim 1 , wherein the photosensitive detector is deployed adjacent a body of water, the method further comprising computing, based on the dark-current-corrected spectrum, a quantity related to water quality of the body of water.