Topic
Candela
About: Candela is a research topic. Over the lifetime, 221 publications have been published within this topic receiving 5629 citations. The topic is also known as: cd.
Papers published on a yearly basis
Papers
Abstract: Candela‐class high‐brightness InGaN/AlGaN double‐heterostructure (DH) blue‐light‐emitting diodes(LEDs) with the luminous intensity over 1 cd were fabricated As an active layer, a Zn‐doped InGaN layer was used for the DH LEDs The typical output power was 1500 μW and the external quantum efficiency was as high as 27% at a forward current of 20 mA at room temperature The peak wavelength and the full width at half‐maximum of the electroluminescence were 450 and 70 nm, respectively This value of luminous intensity was the highest ever reported for blue LEDs
3,887 citations
TL;DR: In this paper, the basic illumination characteristics of lighting source using 10-cd-class InGaN-based white LED (an efficacy of 15lm/W) under a driving condition of AC 100-V.
144 citations
TL;DR: In this article, the authors propose to redefine the candela in terms of fundamental quantum optical entities, i.e. photons, and demonstrate equivalence with existing techniques, together with new possibilities which would result from further improvements in accuracy.
Abstract: The candela, the SI (systeme internationale) unit for optical radiation, has been one of the base units since the inception of the system. The latest definition was in 1979, when it was linked to the derived unit, the watt. Advances in optical technology and the needs of the communication sector suggest that it is timely that consideration be given to redefining the candela in terms of fundamental quantum optical entities, i.e. photons. Validation of this approach will require comparison against the most accurate conventional technique, cryogenic radiometry. A definition in terms of photon number and the requirements for demonstrating equivalence with existing techniques is discussed, together with new possibilities which would result from further improvements in accuracy. Work being carried out at the National Physical Laboratory (NPL) towards these goals is described, drawing on developments of photon-counting calibration techniques and low temperature measurements, and research into single photon sourc...
90 citations
TL;DR: In this paper, an optical power calibrator is described whose overall calibration uncertainty is less than 10/sup -4/ for a green He-Ne laser at a wavelength of 543.5 nm, being close to the wavelength at which the candela is defined.
Abstract: An optical power calibrator is described whose overall calibration uncertainty is less than 10/sup -4/ for an optical power of 0.13 mW. The laser light source of the system operates at a wavelength of 543.5 nm, being close to the wavelength at which the candela is defined, 555 nm. A stable optical power is achieved by stabilizing the intensity and the frequency of a green He-Ne laser. The optical power is detected by a cryogenic absolute radiometer based on the principle of electrical substitution radiometry. It can be used to measure up to 0.5 mW in the visible and near-infrared region with a 3 sigma uncertainty of about 5*10/sup -5/. The factors limiting the overall uncertainty of the calibrator are analyzed: the conductance fluctuations of the temperature sensor in the absorption cavity and the beam scatter are found to be the most significant error sources. Limited absorptivity of the cavity (0.99998) and the background radiation cause additional uncertainty. The system is controlled by a microcomputer with self-check and autocalibration features. >
60 citations
TL;DR: The Système International base unit for photometry, the candela, has been realized by using absolute detectors rather than absolute sources, which permits luminous intensity calibrations of standard lamps with an expanded uncertainty of 0.46%, almost a factor-of-2 improvement.
Abstract: The Systeme International base unit for photometry, the candela, has been
realized by using absolute detectors rather than absolute sources. This change
in method permits luminous intensity calibrations of standard lamps with an
expanded uncertainty of 0.46%, almost a factor-of-2 improvement. A group
of eight reference photometers has been constructed with silicon photodiodes,
matched with filters to mimic the Commission Internationale de
l’Eclairage spectral luminous efficiency function for photopic
vision. The design, characterization, calibration, evaluation, and further
application of the photometers are discussed.
49 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 1 |
| 2020 | 7 |
| 2019 | 4 |
| 2018 | 6 |
| 2017 | 1 |
| 2016 | 5 |