The most critical factors for materials grown by chemical vapor deposition (CVD) are the local substrate temperature distribution and gas-phase concentration/distribution of activated growth species near the substrate surface. We present a micro-optical system design which can perform spatially resolved in situ spectroscopic measurements of both local substrate temperature and gas-phase species concentrations/distributions in real time. We present spatially resolved emission spectra from a high density plasma showing variation in CH, C2, and H radicals near the substrate during diamond growth. Substrate temperatures can be calculated from the measured blackbody emission spectra, using standard linearization methods. These techniques provide a flexible tool for temperature measurement and process optimization during CVD film growth, as well as means of studying the complex surface chemistry underlying the growth of diamond films and other technologically important materials. © 1997 American Institute of Physics.