OL 25-RS Diffuse Reflectance Standard
The OL 25RS consists of a 2 x 2 inch, pressed PTFE (Polytetrafluoroethylene), diffuse reflectance plaque. The PTFE powder is packed to a density of 1.0g/cm3 in a blackened aluminum holder. Measurements of diffuse and/or bi-directional spectral reflectance are performed over a customer specified wavelength (from 200 to 2500 nm) and interval.
Diffuse reflectance is based on 10° hemispherical diffuse reflectivity measurements made using the OL 750 Automated Spectroradiometric Measurement System with the OL 740-70 Integrating Sphere Attachment. The four beam “comparison” method is employed to give the most accurate results. The absolute reflectance values of PTFE are based on the results of Weidner and Hsia of NIST1/ for freshly packed PTFE.
Bi-directional reflectance is based on customer specified incidence/reflection angles (typically 30°/0°). Again, the absolute reflectance values of PTFE are based on the results of Weidner and Hsia of NIST 1/ for freshly packed PTFE.
Dimensional Specifications and Layout
For further information, refer to Bulletin 161.
OL 25-RS-S Specular Reflectance Standard
The OL 25RS-S consists of a 2 x 2 inch, front surface coated aluminum mirror with a magnesium fluoride overcoat. Measurements of specular spectral reflectance are performed over a customer specified wavelength (from 0.20 to30 µm) and interval.
Specular reflectance is based on a customer specified incident angle (typically 45°) using the OL 750 Automated Spectroradiometric Measurement System with the OL 740-75M Variable Angle Specular Reflectance Attachment. The measurement is performed using a "self-calibrating" technique which consists of performing a spectral scan with the detector in the 0° position. Following the calibration scan, the sample is placed in the sample holder, rotated to the specified incident angle, and another spectral scan is performed. The specular reflectance is the ratio of the scans.
1/ V.R. Weidner and J.J. Hsia, “Reflection Properties of Pressed Polytetrafluoroethylene Powder,”
J. Opt. Soc. Am. 71, 856-861(1981).
For further information, refer to Bulletin 161.
