The base TERALED system contains a radiometric detector only, since the basic purpose of the system is to account for the emitted optical power when performing thermal characterization of the LED under test.
Since Inphora's detector technology is based on using appropriate filters in front of a Si photovoltaic cell, extending the TERALED system towards photometric and colorimetric measurements is possible by the application of a plain detector head and different filters. Silicon photodetectors can be matched with Inphora filters to obtain CIE tri-stimulus type responses for colorimetric measurements of objects and light sources.
figure a.)
figure b.)
figure c.)
Spectral response of Inphora detectors with different filters compared to the corresponding CIE functions: a.), b.), c.)
Also, the CIE V(λ) and V'(λ) functions can be approximated this way with high precision. For a photometric detector the most important quality criterion is its spectral match to the CIE V(λ) function. To describe this the error f1' function has been introduced, characterizing the mean deviation of the spectral match weighted with the CIE Standard Illuminant "A" spectral power distribution, (see CIE Publ. 53 and 69).
Inphora's photometric detectors (including TERALED's IPR-TERADET detector head equipped with a V(λ) filter) conform to these and other CIE specifications. With the TERALED system error class f1'=1.5% is provided (in agreement with the German DIN 5032/Teil 7 classification).
The following filters are provided for use in the TERALED system:
V(λ) filter for luminous flux measurement,
V'(λ) filter for scotopic flux measurement,
1, 2 and filters to measure the tri-stimulus values.
For an automated use of the filters, a filter bank with a carousel storage holding the filters is available.
Photometric and/or radiometric measurements in equilibrium
The LED under test is measured in a stabilized state at a programmed current
and at a programmed temperature. Depending on the filter in use
• total luminous flux (filter matched to the CIE V(λ) or V’(λ) function within 1.5%),
• total radiometric flux,
• X, Y, Z tristimulus values can be measured.
Filter bank
Part number: IPR-TERAFILT
As an optional item, a filter bank with up to 6 different filters can be ordered with the TERALED system. The filter bank has a carousel storage that is rotated with a stepping motor. The filter bank fits directly into the Ø 60 mm detector port of the TERALED sphere.
When the filter bank is installed the radiometric detector is replaced by a plain detector head with no filter in it. The control of the carousel storage is provided by the TERALED control unit – for this the filter bank control cable of the TERALED sphere equipped with an 8 pole RJ plug has to be connected to the filter bank. Beside the control signals this cable also provides the electrical supply for the filter bank.
When attaching the filter bank to the sphere, the radiometric detector and the Ø 60/25 mm port adaptor should be stored at a safe place for any possible later use.
, b.) 
, c.) 
