EOP Optical probes

Optical probes with diffuser for irradiance measurements

For measuring irradiance and illuminance as well as for general coupling of light into the spectrometer, Instrument Systems provides a range of optical probes. These differ primarily in the cosine correction, the degree of light throughput and the spectral range. All optical probes include a diffuser for the incident light. Behind the diffuser is the entrance facet of the optical fiber used to couple the light into the spectrometer.


  • flexible optical fiber connector
  • versions with varying cosine correction and light throughput
  • special version with fixed field-of-view of 5.7°
  • Overview of the available optical probes:

    ModelCosine correction Light throughput Spectral rangeApplication
    with fiber bundle connector
    EOP-146 goodmedium190 - 2500 nm for extended light sources
    EOP-120 mediumgood190 - 1700 nmuniversal
    EOP-121mediumgood190 - 1700 nm universal, flat format housing
    EOP-140lowhigh190 - 2500 nm low light levels
    EOP-542n/ahigh190 - 2500 nm 5.7° field-of-view
    with SMA fiber connector
    EOP-350 very lowgood1000 - 5000 nm IR spectral range
    integrating sphere
    ISP40-101excellentlow220 - 2500 nmSpectralon coating for UV measurements
    ISP40-102excellentlow240 - 2600 nmBaSO4 coating for a broad spectral range

    For general applications we recommend the optical probes from the EOP-120 and EOP-121 series (the latter with fiber bundle connector on side), as these offer the best compromise between cosine correction and light throughput.

    A very good cosine correction is necessary for extended light sources, which unfortunately also means low light throughput – as is the case for the EOP-146.

    The optical probe EOP-140 is only recommended for applications that demand a high light throughput. EOP-542 is available for measurements with a specified field-of-view of 5.7°, generally used for measurement of direct sunlight.

    Integrating sphere ISP 40

    Integrating spheres provide an ideal cosine correction together with a broad spectral range. Instrument Systems offers the ISP 40 to meet this requirement. It was developed for generally collecting radiation and for measurements of irradiance. The ISP 40 is ideally suited for analyzing collimated beams, such as those produced by optical imaging systems, fiber optics and endoscopes. The intrinsic “integrating” function of the sphere means that the entire beam is captured, regardless of whether it is divergent or convergent, and launched into the fiber and subsequently coupled into the spectrometer.

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