Radiometry intensity measurements

Radiometry The measurement of quantities associated with radiant energy. The radiometric unit of intensity is irradiance. 

The various terms that are used for the description of the emission of electromagnetic radiation from a radiant source or for the receipt of electromagnetic radiation by a specified surface element are summarized in Tab. 3-9. The terminology of electromagnetic radiation measurement is divided into radiometry and the subset of photometry (Fig. 3-18). The former is the science that involves the energy measurement of electromagnetic radiation in general. The latter is applied for the same purpose when visible radiation is to be described or measured in relation to the human eye s response. Important photometric quantities are for example luminous flux, luminous intensity, illuminance and luminance (McCluney, 1994). Every photometric quantity has its counterpart in radiometry, and vice versa. 

Irradiation. The liquid formulation was applied with a calibrated bar onto either a KBr crystal for infrared analysis, or a glass plate for hardness and gel fraction measurements. 10 to 20 pm thick films were exposed to the radiation of a 80 W/inch medium pressure mercury lamp, in the presence of air, at a passing speed of 60 m/min, which corresponds to a 0.1 s exposure at each pass. The incident light intensity (Iq) at the sample position was measured by radiometry (International Light IL-390) and... 

The photopolymerizable formulation containing between 1 and 3 wt % photoinitiator was coated on a polypropylene film or on a silicon wafer, at a typical thickness of 24 pm. In some experiments a second polypropylene film was laminated on top of the liquid resin to prevent the diffusion of atmospheric oxygen. The sample was placed in the compartment of an infrared spectrophotometer where it was exposed for a few seconds to the UV-radiation of a medium pressure mercury lamp. The light intensity at the sample position could be varied between 5 and 100 mW cm, as measured by radiometry (International Light radiometer IL-390). 

The base unit candela allows one to establish a quantitative relation between radiometric and photometric measurements of light intensities. In physics and chemistry, the intensities of radiation fields of various natures are normally determined by radiometry in visual optics, in lighting engineering, and in the physiology of the visual system, however, it is necessary to assess the intensity of the radiation field by photometric means. 

---