A digital light modulation microscope (DLMM) using a digital micro-mirror device (DMD, Texas Instruments) has been developed to enable detection of O<sub>2</sub> concentration in micro-bioreactors using O<sub>2</sub>-quenching porphyrin phosphorescent dyes. The emission intensity and phosphorescence lifetime of such dyes are both a function of O<sub>2</sub> concentration. While emission intensity can vary in these dye systems as a function of concentration and illumination intensity, phosphorescence lifetime is primarily sensitive to only O<sub>2</sub> concentration. In contrast to conventional phosphorescence lifetime imaging, the DLMM eliminates the need for a pulsed light source, scanning mirrors, or a high-speed camera for time-gated imaging. This technique can selectively address structured light illumination to each sensor location, which is a beneficial feature for analysis of large micro-sensor arrays within lab-on-a-chip devices. The mirrors on the DMD perform as electronically addressable optical switches, each having a ~15 μs switching time, shorter than the phosphorescence lifetimes of potential O<sub>2</sub> sensing dyes (~25-100 μs). The structured light pattern of the DMD and the switching rate of the mirrors are controlled by a PC. An arc lamp illuminates the DMD uniformly and then projects to the specimen through a filter cube for the selected phosphorescent sensor compound. The emitted light returns to the filter cube and is detected by a photo multiplier tube (PMT). An oscilloscope is used to record the emission signal waveform from the PMT. To demonstrate O<sub>2</sub> sensing with lab-on-a-chip devices, an array of 150-μm-diameter micro-wells coated with phosphorescent porphyrin were observed using the DLMM. The goal of this platform is to measure the O<sub>2</sub> consumption of individual cells trapped in the microwells.