The Navy Primary Standards Department (NPSD) is charged with maintaining and disseminating the fundamental standards of measurement for the U.S. Navy. Measurement areas include Electrical (standard volt and resistance), Microwave, Temperature, Mass, Pressure, Dimensional, Flow and the topic of this paper, Radiometry, Photometry, and Electro-Optics. This paper is divided into four sections.In the first section we describe the primary measurements performed.These include blackbody calibrations, photometric lamp calibrations, spectral detector, filter and source calibrations, laser power and energy measurements, and optical pyrometry calibrations. Also included in this section are statements of the measurement uncertainty.In the second section we describe the primary standards maintained by the laboratory, the process used to maintain traceability to the National Bureau of Standards (NBS), and the processes used to provide the measurement to lower level laboratories.In particular, we discuss fundamental reference standards such as zinc and tin freeze point blackbodies, Measurement Assurance Programs (MAPs), and the use of primary standards calibrated by NBS. We discuss measurement system development in the third section of the paper. Major topics include automation, system standardization, and development of system uncertainties. The principal systems described are a blackbody calibration system, a spectral calibration system to calibrate detectors, filters and sources, and a laser power and energy calibration system. Finally, we discuss the new primary measurements needed to support future Navy requirements.Main topics are near and far field laser beam profile measurements, low light level measurements, high energy laser measurements, fiber optics measurements, and the development of systems that will extend the measurement of electromagnetic radiation to wavelengths of up to one millimeter.
Description of the primary measurements
Calibration of blackbodiesThe calibration of NPSD working standards is done against tin and zinc freeze point blackbodies. The method of comparison is virtually identical to one of the methods of comparison between the NPSD working standard (STD) and the customer's instrument under test (IUT).A discussion of these follows.Customer blackbody calibrations are carried out by one of three direct comparison methods between the IUT and the STD.The traditional comparison method has been to utilize the design configuration shown in Figure 1. The standard detector is a built -in, biased PbS detector; the frequency of the chopping mirror is roughly 13.5 Hz.A second method relies on this same configuration, but the chopping mirror is now merely flipped manually, and the blackbody output is imaged upon a HgCdTe or an InSb detector cooled to 77K.A third method is to mount the STD blackbody at the aperture of an off axis collimator and image the output on one of the cooled detectors mentioned above.Comparison is then accomplished by exchanging the IUT with the STD in a manner which affords a degree of ...
