National Physical Laboratory

Optical Radiation Detectors - Transfer & Working Standards

Used in the realisation of spectral scales, detectors can be supplied as calibrated transfer standards to disseminate responsivity from a primary standard to a customer detector.

Transfer Standard Detectors

Transfer standard detectors

Traceability Diagram

Traceability diagram

NPL's calibrated detectors are traceable to our primary standard, the cryogenic radiometer. Trap detectors are used to transfer the primary spectral responsivity scale from the cryogenic radiometer to working standards using the spectral responsivity facility. The detectors are designed so that a spectrally continuous, high accuracy scale can be generated. The same facility is used to transfer this chain of traceability to other working standards or customers' detectors.

Detectors include thermal detectors with flat spectral response, as well as detectors that respond specifically to a certain region of the spectrum.

Custom-built cavity pyroelectric detectors are made at NPL to provide traceability in the infrared and work as transfer standards for spectral responsivity. We also provide photometers that mimic the response of the V(λ) curve.

Detectors can be used to cover the whole spectral range from the Ultraviolet, through the Visible to the Far Infrared.

Detectors are used at all points in the traceability chain, as transfer standards and working standards.

Further detector characterisation is provided by a Uniformity and Linearity of Response facility, which can be provided along with a Spectral Responsivity system.


Generally supplied in sets of three, there are many types of calibrated detector covering the spectral region 200nm to 14µm, packaged to suit specific customer requirements. Amplifiers and digital voltmeters can be supplied on request.

Detector Spectral Region
GaAsP UV detectors calibrated or uncalibrated 200 nm to 600 nm
Silicon working standard 240 nm to 1000 nm
Silicon trap detectors calibrated or uncalibrated 380 nm to 920 nm
InGaAs near IR detectors calibrated or uncalibrated 900 nm to 1640 nm
InSb sphere detectors tested but uncalibrated 3 µm to 5 µm
HgCdTe sphere detectors tested but uncalibrated 8 µm to 14 µm
Photometers; supplied with temperature control and read-out unit A Silicon photodiode and four element glass V(λ)-correction filter, housing maintaining 30 °C in ambience of 18 °C to 29 °C
Additional amplification systems and lock-in amplifiers for infrared measurements
InSb and HgCdTe additional spheres; 50mm gold coated half sphere and mounting adaptor
Detector comparator stage
Spectral responsivity facilities & Linearity and Uniformity facilities

NPL's support includes the installation of the facility and training in its use.

Contact us for further information

Call the Instruments team on: 020 8943 6539

Last Updated: 10 Apr 2017
Created: 31 Jul 2007


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