White References

Middleton Spectral Vision offers several white reference materials for the calibration of hyperspectral images. The whitereference materials should be measured before the sample using the same illumination configuration. The white standard measurement will be used along with the dark (closed shutter) reference data to correct for non-uniform illumination across the image and to produce results on a true reflectance scale. When measuring white references with the hyperspectral cameras shown in this catalog, SpectralDAQTM software can be used to control the camera settings, motion, and data collection, and can also be used to automatically collect and apply the white reference data for all measurements.

High-Reflectivity Ceramic

Accuflect B6Porous ceramic tiles can be used as a white reference material for hyperspectral cameras. The material is 95-99% reflective in the wavelength range 450-2500 nm, which covers the NIR to SWIR ranges and most of the visible range. The tile exhibits Lambertian light scattering behavior, with high diffuse reflectance . In addition, it maintains its reflectivity in high temperatures (up to 1300°C) and high energy environments with UV exposure. It is a rugged, heattolerant, easy-to-clean alternative to other white reference materials. A typical reflectance spectrum of the ceramic white reference material is shown at the left.

Mechanical CharacteristicsUnits of MeasureSI/MetricImperial
Density gm/cc (lb/ft3) 2.3 143.5
Porosity % 30 30
Color -- white white
Flexural Strength MPa (lb/in2x103) 27.5 4
Compressive Strength MPa (lb/in2x103) 62 9
Maximum Use Temp. (no load) °C (°F) 1200 100

PTFE White Calibration Tiles

Middleton Spectral Vision provides a white calibration tile made of a processed PTFE material to calibrate hyperspectral cameras. A lens with a wider field of view will image a wider area, and longer lengths of the white reference material may be needed to correct for the white balance along the entire length of the imaged line. Two standard lengths are listed here, but longer, custom lengths are available. Contact Middleton Spectral Vision for more details.

The PTFE material in these calibration tiles has ideal properties as a Lambertian reflector. The tiles offer excellent reflection properties, long-term stability and temperature consistency. The reflectance is typically greater than 98% between 300 and 1700 nm, making the tiles an ideal source for calibrating cameras across a wide range of wavelengths.

Specifications

  • Temperature range: -200 °C min. - +260 °C max.
  • Hardness: 30-40 Shore D
  • Water solubility: insoluble
  • Resistance to chemicals: high

Traceable High Refelctivity Diffuse PTFE Standards

white standard.JPGPorous PTFE reference material is another choice for calibrating hyperspectral images. The reference material has high reflectivity and acts as a Lambertian reflector, producing diffuse reflected light that is uniform across the entire surface of the material.

 This material is available in some standard sizes (listed here) and other various sizes with custom holders to accommodate a wide variety of hyperspectral imaging applications. Contact Middleton Spectral Vision to discuss your application requirements, and to determine the appropriate size and shape of the required reference material. The 8 degree hemispherical diffuse reflectance of the material is traceable to the National Research Council of Canada (NRC), and detailed reflectance values and a certificate are provided with the standards.

ParameterValueUnits of Measure
Porosity (by weight)   45 % (nominal)
Thickness 3.0 mm ± 0.25

Mupor

             Typical reflectance spectrum of porous PTFE material

White References Ordering Information
Part numberDescription
MRC-910-W12 Light-reflecting porous ceramic tile, 2” x 12” x 1/4”
MRC-910-W38 White Reference Standard, 36mm diameter, 2.25" housing
MRC-316-004-01 White calibration tile, 300 mm x 25 mm x 10 mm
MRC-316-004-02 White calibration tile, 600 mm x 50 mm x 10 mm
MRC-316-004-04 White calibration tile, 600 mm x 100 mm x 10 mm
MRC-316-004-03 White calibration tile, 430 mm x 430 mm x 10 mm, cased

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