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This text has gone into considerable detail on the analysis and measurement of BSDF data. The importance of using a data set that truly matches a specific should be very clear. There are times when knowing general BSDF levels can be of considerable help. For example, if you have determined via analysis that a ZnSe window will work in your application if its mid-IR scatter can be kept below 10-3 sr-1 at 30 deg from specular, then knowing that windows are routinely made at 10-5 sr-1 in this region lets you proceed with your design. If you needed 10-6 sr-1, then the situation would be a little more difficult. You might actually want your component measured, or you might want to change your design.

Another problem with practical use of BSDF data sets is categorizing the variables associated with the sample, the measuring instrument, and the laboratory-reporting methods. The two BRDF standards (SEMI 1392 and ASTM E2387) described in Section 12.2 provide formats for reporting BRDF data as well as complete definitions of terms. These documents provide a means for laboratories to compare, trade, and purchase reliable measurements on samples of interest. It is also expected that a relational database, probably PC based, will become available that will allow a fast search of hundreds of files to obtain data that fit a particular requirement.

The 32 BSDF scans in this appendix are offered in the spirit of giving merely a sense of values measured from a few samples. Hopefully, it will be useful in the short term. Once an accessible national database is available there will be little need for the microscopic, difficult-to-use windows on BSDF data provided by data sets similar to those in this appendix.

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