Used to express both Beam Intensity (Beam Candela) and Mean Spherical Intensity (Mean Spherical Candela). One candela is equivalent to 1 lumen/steradian. The current SI unit of luminous intensity. Calibration can also be accomplished by the use of a standard source (lamp) whose output energy at specific wavelengths and measurement distances are traceable to the standard lamp defined by the governing standards body (NIST).

The process of normalizing the signal output from a detector to that of a detector defined as a standard (usually defined by National Institute of Standards and Technology (NIST) under identical illumination conditions). As there is no such thing as a perfect black body, black body simulators are used for this purpose. When heated a black body emits a well defined characteristic spectrum which can be used in characterizing the spectral responsivity of detectors. Beamwidth is usually defined as the angle subtended by a cone encompassing 90% of the energy.Ī black body is an object that absorbs all radiant energy that hits it. The angular width of a cone of light whose apex is at the source. A 500nm band eliminator filter with a band pass of 10 nm would suppress the wavelengths between 495nm and 505nm. These filters are also called notch filters. This can be, for example, between 500nm and 510nm, 1000nm and 1010nm or an equal size segment anywhere in the spectrum.Ī band eliminator filter allows the wavelengths above and below the filter cutoff to pass while suppressing the wavelengths within the band. A bandwidth of 10nm indicates a range of 10nm of radiation. The QNDS,QNDS2 and QNDS3 filters are attenuators that reduce flux density at the detector by factors of 10, 1, respectively.īandwidth describes the size of a spectral segment. Attenuators are typically used when the radiant energy would saturate a detector. A lens with a focal length of 100mm and a diameter of 25mm would have an aperture of f/4.Ī device which reduces the amount of energy reaching a sensor. The f/# is the ratio of the focal length of the lens to its diameter. The aperture of a lens is often expressed in terms of an f/#. Angular aperture is the angle through which the most divergent rays can pass through a hole or lens. To make valid measurements, the contribution from the ambient light or background must be subtracted from each measurement.Ī hole through which radiant energy can pass. This light contributes to the signal measured from the source. See the Optical Radiation Hazard applications page for a listing of ILT light measurement systems used to determine the actinic hazard of a light source.Īmbient light is the light diffused in the environment surrounding a detector measuring the optical radiation from another source. The color or optical density of the strip changes with the exposure. Actinic strips are used in UV processing to monitor the intensity of sources. In our industry the term is usually used with reference to UV radiation and its effects on biological systems. The characteristic of radiation that indicates its capability to produce chemical change. If the %transmission of a certain wavelength is 70% then the material has a 30% Absorptance.

Absorptance can also be inferred from the transmission through a medium. The standard unit of absorptance is percent (%) or a factor between 0 an 1. The ratio of the total absorbed radiant or luminous flux to the incident flux is called absorptance. The absorption is the 'missing piece', when comparing the total reflected and transmitted energy with the incident energy. The dissipation of light (radiation) within a surface or medium, caused by the conversion of radiant (luminous) energy to a different form of energy, usually heat, by interaction with matter. A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Candela meaning