सीएसआईआर-राष्ट्रीय भौतिक प्रयोगशाला

CSIR-National Physical Laboratory

Optical Radiation Metrology

Optical radiation measurements cover the wavelength region of electro-magnetic spectrum from 200nm to 2500nm. The wavelength region from 200 nm to 2500nm is maximally used for measurement of many interlinking disciplines. As Radiometric measurements are used in a wide range of industries including opto-electronics, telecommunications, lighting, space and in health and safety, precision measurements are required for specification for systems, for quality control in industries and in scientific research. The objective of this section is to establish, maintain, and upgrade the existing base unit of optical radiation, i.e., candela and to provide calibration facilities for various photometric parameters namely luminous flux, illuminance, luminance, luminous intensity, detector responsivity, color temperature and radiometric parameters namely spectral radiance and spectral irradiance in the range from 200nm to 2500nm.

In addition, this section also provides measurement facilities for spectroscopic parameters namely spectral reflectance, spectral transmittance, absorbance, and polystyrene film calibration by FTIR. Other calibration facilities include calibration of thermo-vision camera, black-body and NIR related measurements.

Variable temperature blackbody, Goniophotometer, Fourier Transform NIR and IR spectrophotometer, Raman-spectroscope, spectral irradiance measurement setup, spectrophotometers, corretected photon metrology setup, LED measurement setup, various standard lamps and detectors.


Source based primary standard of spectral radiance in the form of a variable temperature blackbody has been established. This blackbody works in the temperature range of 1800K – 3200K with temperature stability of ± 0.2K. Its emissivity is 0.999, and exhibits radiance uniformity within 0.1%, in the wavelength range 0.2 μm-2.5 μm. The uncertainty in spectral radiance measurement using this blackbody is 0.3-0.5% in the wavelength range 0.2 μm-0.4 μm, and 0.1-0.3% in the wavelength range 0.4 μm-2.5 μm, respectively. The established facility is shown in the Fig. 1.

Fig.1: Blackbody Setup

Luminous Intensity, Illuminance and Illuminance Responsivity Measurement

Luminous intensity, illuminance and illuminance responsivity measurements are carried out using 3.0 m optical bench. The optical bench and other measurement instruments are shown in Fig. 2.