EOP - 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.

Features:

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:

Model	Cosine correction	Light throughput	Spectral range	Application
with fiber bundle connector
EOP-146	very good	medium	190 - 2500 nm	for extended light sources
EOP-120	medium	good	190 - 1700 nm	universal
EOP-121	medium	good	190 - 1700 nm	universal, flat format housing
EOP-140	low	high	190 - 2500 nm	low light levels
EOP-542	n/a	high	190 - 2500 nm	5.7° field-of-view
with SMA fiber connector
EOP-350	very low	good	1000 - 5000 nm	IR spectral range
integrating sphere
ISP40	excellent	low	220 - 2500 nm	solar radiation

For general applications we recommend the optical probes from the EOP-120 und 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. Integrating spheres offer an ideal cosine correction together with a broad spectral range. Instrument Systems has developed and offers several versions of the ISP40 to meet this requirement.

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.

Downloads

EOP datasheet

Further Information

Cosine correction

Assuming that the light source is arranged normal to the detector surface, then according to photometric fundamentals, irradiance can only be correctly determined for an extended source when the signal sensitivity of the detector changes with the cosine of the incidence angle.

E = E₀ x cos(α)

E : irradiance at incidence angle (α)
E₀ : irradiance at normal incidence
α : angle between the incident light beam and the detector normal

As a general rule, the better the cosine correction, the lower the light throughput.