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Introduction
This document will provide a description of the PlexBright®Light Measurement Kit components and
instructions for proper usage with the PlexBright Optogenetic Stimulation System (PlexBright System).
Plexon provides the PlexBright Light Measurement Kit, containing the THORLABS PM100D Optical
Power and Energy Meter (PM100D Power Meter) and S140C Integrating Sphere Photodetector (S140C
Photodetector). This kit also includes adaptor pieces required to interface the S140C Photodetector with
PlexBright LED Modules and PlexBright Optical Patch Cables. If you have already purchased the S140C
Photodetector and a matching PM100D Power Meter, then you only need to purchase the necessary
photodetector adaptor kit from Plexon. (See Appendix for more information about why PlexBright
photodetector adaptor pieces are critical for accurate readings.)
This guide will provide a basic overview and describe components, hardware set-up, measuring steady-
state light outputs, dynamic/pulsed light measurements, and includes an Appendix on avoiding light-
clipping with PlexBright Photodetector Adaptors.
Overview
It is often useful to measure light outputs from the PlexBright System. For example, light output
measurements can validate proper functioning of a PlexBright LED Module and proper connection of any
attached PlexBright Optical Patch Cable and PlexBright Fiber Stub Implant. Also, because of variations
between PlexBright LED Modules, PlexBright Optical Patch Cables and PlexBright Fiber Stub Implants,
expected light outputs for a given supply current are only approximate. Light output measurements
enable the precise control of optical stimulation that is often required in optogenetics experiments.
Light output measurements typically require a photodetector and power meter. The photodetector
transduces incident light into an electrical signal, which the power meter processes and converts into a
reading of light intensity. Dierent power meter/photodetector combinations will enable measurements
of PlexBright light outputs, but the wrong components or even the incorrect use of the right components
may lead to inaccurate measurements.
To take measurements of light output from the PlexBright System, Plexon highly recommends use of the
PM100D Power Meter and S140C Photodetector along with specially designed PlexBright Photodetector
Adaptor pieces for the most accurate readings. Standard photodetector adaptors are often not designed
to anticipate the wide output angle of light emitted by the high performance PlexBright System. Thus, the
resulting readings are likely to under represent the true output. Using the PlexBright Light Measurement
Kit as described on the following pages will ensure you have the right equipment and techniques to make
the most accurate measurements.
