Radiometric and Actinometric Traceability for Photopolymer Processing

Photopolymer processes are often described by an irradiance, exposure time and nominal wavelength. Those quantities are not sufficient to establish what radiation reached a sample. Detector responsivity, spectral bandwidth, spatial non-uniformity, angle, distance, window transmission, temporal modulation and sample geometry can produce different exposures while the displayed settings remain identical. Chemical actinometers add a valuable reaction-based measurement but do not remove these dependencies; they introduce their own absorption, quantum-yield, conversion and analytical boundaries.

This review develops a traceability architecture for radiation used in photopolymer processing. It distinguishes spectral irradiance, band-integrated irradiance, radiant exposure, spectral photon exposure and chemically measured photon quantity. It connects national-scale spectral-irradiance calibration to working instruments, sample-plane mapping and in-process checks while preserving uncertainty at every transfer. Radiometers and actinometers are treated as complementary: the former measures a physical radiation field through a calibrated responsivity, whereas the latter reports a photochemical response under a defined spectral and geometrical condition. The review proposes procedures for spectral mismatch, pulsed or modulated sources, imaging systems, area mapping and cross-platform transfer. The central conclusion is that an exposure setting becomes comparable only when the measurand, plane, spectrum, geometry, timing and uncertainty are fixed.