In this paper, we report a 64 times 64 active pixel sensor, designed for low-power image sensing for wireless sensor networks. The proposed image sensor computes the temporal difference between two continuous frames and communicates them in an address-event representation format. The image sensor is capable of computing 30 temporal-difference frames per second (fps) and consumes 1 mW with a 3-V power supply. Light-intensity images are also available as an output at a speed of 60 fps. The image sensor was fabricated in a 0.5-mum bulk CMOS process. The fabricated sensor was tested with various stimuli to evaluate its performance. The die size is 3 mm times 3 mm, including pads and test structures. Each pixel occupies an area of 29 times 28 mum ² with a fill factor of 23%. The minimum detectable speed of the temporal-difference is 4.5deg/s.