A 37 × 37 pixels artificial retina chip with edge enhancement function for 3-D stacked fully implantable retinal prosthesis

To restore visual sensation of blind patients suffering from age-related macular degeneration (AMD) and retinitis pigmentosa (RP), we have been developing a fully implantable retinal prosthesis with three-dimensional (3-D) stacked artificial retina chip. This chip has layered structure similar to human retina and includes such functions as converting incident light into electrical signal, processing visual information, and generating stimulus current pulse. In this paper, we have developed a photoreceptor chip with selectable sensitivity circuit and a stimulus current generator chip with edge enhancement function using four-neighbor Laplacian filter for 3-D staked artificial retina chip. As results, the 37 × 37 pixels photoreceptor chip correctly converted incident light into electrical signal, and the edge enhancement and stimulus current generator chip with edge enhancement function successfully emphasized the edges of input images and generated biphasic stimulus current patterns. By stacking these two chips, artificial retina chip having a pixel number of 37 × 37, a pixel size of 75 × 75 μm², and the fill-factor more than 27%, will be realized.