The description of a new experimental design for microluminescence is presented in this article. The design is based on the optical analysis of a magnified luminescent region and has been proven to be useful for studying the photon transport mechanism in a solid luminescent material. Lock-in detection and a liquid-nitrogen-cooled detector are used to obtain signal-to-noise ratio as good as102.The performance of the system is discussed by using the measurements taken from a natural ruby crystal. Using transport theory to fit our data, we found the photon diffusion length in the ruby crystal to be on the order of 46 &mgr;m. ©1997 American Institute of Physics.