Spectral measurements of the directional hemispherical reflectance of samples exhibiting variant reflection behavior were performed in the near and mid infrared spectral region using the integrating sphere method. The main components of the experimental setup were a sphere with a diffuse gold coating and a commercial Fourier transform spectrometer for the spectral analysis of the radiation incident on and reflected by the sample which is located in the center of the sphere. The capability of the device to measure absolute reflectances was tested with polished slices of high purity silicon and germanium, the reflectances of which can be calculated from the refractive indices. Agreement between the measured and calculated values was found to be within 0.01. Diffuse reflectance standards are not yet available in the infrared. The uncertainty of absolute reflectance measurements is estimated to be ±0.02. Several examples of chemical and technical applications are presented. A relatively low spectral resolution, 16 cm<sup>−1</sup>, was used to keep the measurement times short, within the range of a few minutes, thereby minimizing signal drifts. Higher resolution, sometimes necessary for special purposes in chemical analysis, can be attained by longer measurement times. No extensive sample preparation and adjustment is necessary besides the choice of the desired angle of incidence.

PDF Article

Cited By

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
Login to access OSA Member Subscription