Optical imaging techniques such as voltage-sensitive dye imaging and intrinsic imaging allow for the recording of neuronal activity at high spatio-temporal scales over a large field of view 1 , 2 revealing some mesoscopic scale dynamics such as propagating waves 3. 4 In practice however, the achievable image quality deteriorates significantly away from the point of best focus due to the curvature of the brain, which fundamentally limits the spatial extent of the cortex that can be studied through a single image. To improve the field of view achievable by optical imaging, we developed a new optical system adapted to the curvature of the non-human primate brain in study. This is achieved by using a curved detector in combination with an appropriate optical system of double Gaussian and aspherical lenses. Furthermore, to ensure a uniform and reliable illumination of the cortex, we have designed and built a new illumination system consisting of a ring of LEDs at four different wavebands. This static solution will enable imaging for the first time neuronal activity over a very large field of view (15-20mm) with high spatial and temporal resolution. Preliminary results show a significant increase of the area in focus of a spherical object imaged through the custom optics compared with the standard neuronal imaging optics.