Filter-radiometer-based realization of candela and establishment of photometric scale at UME

Establishment of a computer-controlled retroreflection measurement facility to characterize photometric properties of retroreflectors

“…Two photometer heads were used in the measurement system. The first photometer head, which had been calibrated against reference filter-radiometer [10,11], was used as an observation detector (OPH) in order to measure luminous intensity unit after reflection of light from the retroreflector surface. This detector is fixed to a commonly used observation angle of a = 1°30 0 with an accuracy of 0.001°and can easily move from 0.1°to 5.0°b y moving the detector, if retroreflection properties at different observation angles are required.…”

“…Observation and reference photometers were calibrated against reference filter-radiometer that traceable to the photometric scale of UME [10,11]. The first photometer was used as an observation photometer head for measuring luminous intensity unit reflected by the retroreflector in candela and the second one was used as a reference Fig.…”

Estimation of Calibration Uncertainties in the Detector-Based Photometric Calibrations

“…The detector-based luminous intensity calibrations are carried out at UME on a six-meter long optical bench [6]. The optical bench contains: (i) an enclosed cabinet for mounting a lamp under the calibration (LUC), (ii) a rack with a computer for monitoring and to control of electrical parameters of the LUC, (iii) a carriage on rail for gliding the reference photometer (RP) from the LUC up to 6 m and (iv) a set of baffles between the LUC and the RP for reducing stray light (Fig.…”

“…The photometer head had been calibrated using new detector-based UME illuminance scale with expanded uncertainty of 0.30% (k = 2) [5,6]. Thus, the standard uncertainty in the illuminance responsivity value was estimated as u(s v ) = 0.019 nA/lx.…”

Upgradation of a spectral irradiance measurement facility at National Physical Laboratory, India

“…The purpose of establishing spectral irradiance measurement and calibration facility is to provide services to various R&D laboratories and industries. In addition, the integrated value of spectral irradiance weighted by spectral luminosity function (V(O) function) over entire visible region (400 nm -800 nm), multiplied by photometric radiation equivalent (K m =683 lm/W) provides the value of illuminance, which multiplied with the square of the distance gives the value of the luminous intensity in terms of SI base unit candela (cd) [8,9]. Hence, it is also an important parameter to cross-check the scales of photometry.…”