A novel optically triggered global shutter image sensor using single photon avalanche diodes (SPAD) is proposed. An optical signal with a switching frequency of 100 MHz illuminates SPADs and acts as both a shutter and reset signal source by means of free space optics. Each image sensor pixel contains a front side illuminated SPAD, while a pinned photodiode is used to collect the scene's light from the chip back side to increase the pixel fill factor. The pixel is designed and post layout simulated in 90 nm complementary metal oxide semiconductor technology. Moreover, the jitter performance of 76.2 ps (excluding SPAD and light source jitter) is achieved. The image sensor pixel pitch is 90 µm with 2.27 mW power consumption per pixel with a fill factor of above 90%. The image sensor pixel can take 64 different frames at the rate of 50 Mfps and store until the global readout phase.