Core Context Imager:

This imager captures the full length of the 25cm core segment at a resolution of about 125microns/pixel in color. The imager uses a 3.2Mpx (2048x1536 pixels) Canon Power-Shot S230 with remotely operated functions (shutter release, zoom, flash, WB) via a USB connection. The JPEG image file generated by the camera is about 1.6Mb in size.

Core Microscopic Imager:

Microscopic images of the core are acquired using a Canon EOS-10D with a 100mm macro-lens. This obtains color microscopic quality images of pre-determined sections of the core with about a 7 microns per pixel resolution and a field of view of 2.5x 1.66 cm. The sizes of the JPEG files generated are about 6.7Mb and are transmitted via USB interface. The core will be imaged microscopically at predetermined positions (we expect approximately 4 images per 25cm section of core). The number of these images is limited by operational constraints such as time and data volume.

Visible Near Infrared Spectrometer:

The sections of the core selected to be imaged with the microscopic imager are then analyzed with the VNIR spectrometer. The VNIR spectrometer is an Ocean Optics S2000 Temperature Regulated Spectrometer, with a #3 grate (range of 400nm to 1050nm) with a high-sensitivity linear CCD array (2048 element). The spectrometer system is composed of the spectrometer enclosed inside a temperature control box capable of maintaining the set temperature to within 0.1C; an A/D converter box with USB computer interface, and a Tungsten-halogen illumination lamp. The reflectance probe contains six illuminating and one read fibers, all 400micrometers in diameter, UV/VIS; and is placed at an optimum distance to collect spectra of a spot 5mm in diameter.

Imaging Spectrograph:

The scanning spectrograph permits high-resolution imaging of rock core samples with a high degree of spectral information. The instrument utilizes macroscopic imaging optics and a slit input aperture to sample a line on the object (core). A combination of dispersive and diffractive elements and relay lenses provide light to the array detector, which is separated spatially along the slit in one dimension and spectrally along the other array dimension. This is sampled with an 8-bit monochrome industrial vision CCD camera. Scanning the object in a direction normal to the slit while taking multiple images, permits the formation of a data “hyper-cube” in the mode of classic “push-broom” type remote sensing instruments (e.g. PHILLS, HYDICE). The spectrograph resolves 580 columns of 50-microns spatial elements along the input aperture. The hypercube image length is only limited by the length of the scan, presently configured for rock cores that are 25 cm long. The spectrum is sampled by 780 detector rows spanning the 400 to 1000 nanometer wavelength range. This over-sampled spectral data is averaged, typically over 6 rows, to improve signal quality and to reduce hypercube size.

The spectrograph will operate under current-controlled tungsten-halogen illumination to permit the derivation of reflectance data. A spectral calibration is performed using Krypton and Mercury-vapor emission lamps. Radiometric calibration processes include dark frame subtraction and normalization by a reference frame taken with 99% Spectralon in the object field. A "quick-look" color image is produced at the end of the scan comprised of three wavelength bands that represent normal human perception of red(660 nm), green (530 nm) and blue (460 nm). The instrument operator may specify regions of interest in the quick-look image, and load a request to the hypercube data mining software, which will return reflectance spectra data averaged over these regions. The instrument provides only ~48 db max signal-to-noise ratio, as limited by the dynamic range of the camera and particularly limited in the short- and long-wavelength regions by the spectral response of the silicon CCD sensor and the black-body intensity distribution of the tungsten-halogen lamps.