Gigahertz Optik - Light Measurement Solutions

Luminous Transmission

Luminous Transmission measured in percent is used to specify the light throughput of luminous transparent materials.
The light intensity passing through the material can be reduced by re-reflection at the sample surfaces, by particle inclusions, rest porosity and absorption.
The light output of the material specified as transmission is composed of regular (also in-line or direct transmission) and diffuse transmission components. The sum of the regular and diffuse transmission is specified as Luminous Transmittance.
Materials used for windows in buildings, vehicles or as cover glass for instrumentation are typically specified with very low diffuse transmission for maximum clarity. This specification applies to reflection reducing coatings as well. In order to specify materials for these kinds of applications the regular transmission needs to be measured.
Simplified Measurement:

Light source illuminates the target
Sensor measures light output of test sample
100% measurement set-up without test sample in light path

Regular transmission can either be measured with a uniform light source and a luminance sensor (d/0) or with a collimated beam light source with a flat field sensor (0/0). Measurement with a collimated beam is more sensitive to beam deviation that could be created by wedge characteristics of the test sample.
Uniform light sources employing integrating spheres offer a higher light intensity than collimated beam sources because of better efficiency in light collection of the sources.
For regular transmission measurement the sensor design must exhibit a low sensitivity for diffuse radiation.

Datasheet
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