Grating couplers have been widely used for coupling light between photonic chips and optical fiber. For some quantum-optics and bio-optics experiments on the other hand, there is a need to achieve good light coupling between photonic chips and a microscope system. Here we propose an ultra-compact silicon nitride grating optimized for coupling to a microscope system. The grating coupler is about 4×2 um2 in size. 3DFDTD simulations show that up to 80% of the light @ 532 nm can be coupled upwards.. We fabricated the grating coupler by electron beam lithography and preliminary experimental results show the relationship between coupling efficiency and grating period.