Automated Multi-Point Analysis With Multi-Angle Photometric Spectroscopy

Spectral reflection (R) and transmission (T) are the fundamental measurements for characterizing the optical properties of materials and optical coatings. Historically the complete characterization of optical materials and coatings for precision optics has been largely accomplished on the basis of normal and near normal incidence measurements due to the experimental simplicity of such an approach. This simplicity, however, is not without compromise. Normal incidence transmission measurements are typically conducted within the sample chamber of a spectrophotometer whilst near normal reflectance measurements require the use of a suitable reflectance accessory. A consequence of this approach is that there is never any guarantee that reflectance and transmission measurements are made from exactly the same patch on the sample due to sample repositioning during the significant changes in instrument configuration between R and T measurements.Multi-angle Photometric Spectroscopy (MPS) measures the reflectance and/or transmittance of a sample across a range of angles (theta(i)) from near normal to oblique angles of incidence (AOI). A recent development by Agilent Technologies, the Cary 7000 Universal Measurement Spectrophotometer (UMS) combines both reflection and transmission measurements from the same patch of a sample's surface, without sample repositioning, in a single automated platform for angles of incidence in the range 5 degrees <=vertical bar theta(i)vertical bar <= 85 degrees (i.e. angles on either side of beam normal noted as +/-).In this paper we describe the use of MPS on the UMS with rotational (phi) and radial (z) sample positioning control. MPS(theta(i),phi,z) provides for automated unattended multi-angle R/T analysis of multiple individual samples (up to 32 pieces, 1 inch diameter) or mapping of single larger diameter samples (of up to 8 inch diameter). Examples are provided which demonstrate reduced cost-per-analysis in high volume multiple sample testing as well as spatial spectroscopic information obtained on large diameter samples.