instrument for measuring light intensity
• (n.) an instrument for measuring the intensity of light; a photometer.
Lu·cim'e·ter noun [ Latin lux , lucis , light + -meter .] an instrument for measuring the intensity of light; a photometer. 
lucimeter 1. An instrument for measuring the intensity of light; a photometer. 2. A sunshine recorder designed to measure the combined effect of the duration and intensity of sunshine in promoting evaporation.