Measurement Services
"Measure what is measurable, and make measurable what is not so." - Galileo Galilei
Spectral measurements can be made in wavelength regions from the ultraviolet to long wave infrared and include one or all of the following types of reflectance measurements:
Directional or Reflectance: the fraction of the light incident on a sample at a given angle that is reflected back into the hemisphere.
Hemispheric (HDR) or Directional Reflectance (DDR) and Transmittance (T) measurements as a function of wavelength and incident angle
The hemispherical directional reflectance (HDR) of a surface is defined as the ratio of the total energy reflected into the subtending hemisphere to the energy incident on the surface from the direction Theta, Phi. The measured directional reflectance of a surface may be used to compute two important properties required for radiative heat transfer analysis, viz. the directional emittance and the solar absorptance.
A transmissive material may transmit electromagnetic radiation in one of the following two ways. First, as a collimated beam of light propagates through the material it may be scattered into a hemisphere of 2 p steradians upon exiting the material. Materials that exhibit this type of property ( Scattered Transmittance, Ts) are called translucent.
Secondly, if the transmitted beam is parallel to the incident beam across the width of the entire beam, the transmittance is referred to as Collimated Transmittance (Tc). Materials of this type are called transparent.
Utilizing either the Cary 5000 UV/VIS/NIR reflectometer, the SOC-100 or SOC-400T IR reflectometer HDR or T measurements can be made from the UV out to the very long IR. Data is recorded directly to ascii text files on the PC and is importable into ExCel or other spreadsheet software.
Features & Benefits:
- HDR measurements can be made as a function of incident angle (8 to 80° from normal) vs. most competitors who are restricted to near-normal incidence
- HDR measurements in the IR utilize the SOC100 gold plated hemi-ellipse vs. competitors who utilize diffuse integrating spheres. This allows HDR measurements to be made far into the IR (out to 100um) as opposed to 12-15 microns for companies using just integrating spheres.
- HDR measurements can also be partitioned into Diffuse (DDR) and Specular (SDR) components without altering the test set-up. Competitors must set up for measuring each component separately, if they can measure them at all.
- Transmittance measurements (either Ts or Tc) can be made from normal incidence out to 60° from normal. Most competitors can only make normal incidence T measurements.
Applications:
Aerospace
- Verification of Paint & Coating
- Determination of Solar Absorptance & Thermal Emittance
Energy & Solar power
- Determining the specularity (mirror-like qualities) of reflective components
- Mirror Qualification
- Determination of Solar Absorptance & Thermal Emittance
Military
- Missile Defense
- Aircraft & Ground Target Signature Modeling
Remote Sensing
- Simulator Scene Generation
- Ground Truth
- Material Mapping
Bidirectional Reflectance (BRDF) or Scatter measurements from the UV to LWIR
- The bidirectional reflectance (BRDF) of a surface is defined as the ratio of the luminous radiance reflected into a unit solid angle to the total incident radiance.
Features & Benefits:
- BRDF testing can be performed over a wide range of wavelengths by using broad band sources and bandpass filters. Most competitors utilize only laser sources and are restricted to those wavelengths.
- The following are features for BRDF measurements made on the standard SOC BRDF goniometer.
- Wavelengths: 0.26 to 12.0 micron (discrete wavelengths using bandpass filters).
- Incident Angles: normal incidence to 80° incidence from normal.
- Reflected Angles: -85 to +85° from normal (in zenith). Full 360° azimuthal (rotational) coverage.
- Sample size: ½ “ square or diameter up to 10 “ square or diameter.
- Mapping techniques: In-plane only, In-plane and cross-plane, or Full Hemispherical Mapping (Full Mapping).
- SOC has several additional bidirectional reflectometers that are used to obtain bidirectional reflectance data. One such device is unique in that it is designed to measure the direct retroreflection using laser sources. A Michelson interferometer arrangement is used to enable placement of the detector and source on the optical axis opposite the sample. This setup allows the BRDF in the retro direction to be measured using heterodyned detection methods. Wavelengths available for the interferometer are 0.535 and 1.06 microns.
Applications:
Aerospace
- Verification of Paint & Coating
- Stray light analysis
Energy & Solar power
- Determining the specularity (mirror-like qualities) of reflective components
Military
- Missile Defense
- Aircraft & Ground Target Signature Modeling
Remote Sensing
- Simulator Scene Generation
- Ground Truth
- Material Mapping
