(under the class definition) Subject matter wherein the testing process results form a basis for optical comparison with a specimen, article, or portions thereof under test.
SEE OR SEARCH THIS CLASS, SUBCLASS:
46, for electrical lamp circuits which utilize the lamp as a standard for photometry or for optical pyrometry measurements.
421+, for color charts.
SEE OR SEARCH CLASS
250, Radiant Energy,
559.39, for a photocell and associated circuitry for evaluating a material comparing the circuit output to a reference or stored value.
