EOP - Optical probes with diffuser for irradiance measurements

For measuring irradiance and illuminance as well as for general coupling of light into the spectrometer, we provide 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

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 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. Integrating spheres offer an ideal cosine correction together with a broad spectral range. Giant 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

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.