Study On The System Image Processing For Visual Cortex Prostheses

Human got 70% of message about the world through the visual system. Blind coused by a variety of reasons brought a grate pain and inconveninent for the patient's life, work and study. Although the ophthalmic medicine has a rapid development in recent years, there is still not a good treatment for the blind caused by degradation or damnification of retina and optic nerve functions. However, with the development of neuroscience, microelectronincs and computer technology, the visual prosthesis which could produce phosphenes by the elecreical stimulation on the visual pathway brought a hope for the majority of blind patients.In resent years, many research groups are committed to the research of visual prosthesis. According to the difference of stimulation parts, the visual cortex prosthesis can be divided into three types: visual cortex prosthesis, retinal prosthesis and optic nerve prosthesis. The principle of visual proshesis is that transform the image single into electrical single, produce phosphenes by the elecreical stimulation on the visual pathway to produce light perception in the patients in order to repair some of visual function. This paper is based on the project supported by the subproject of the"863"project《The key technologies and applied research of minimally invasive chip outside the visual cortex based on MEMS》. The purpose of this projece is to research the image processing system for visual cortex prosthesis.At present, the visual cortex prosthesis mainly use the phosphone to transmit the visual information. The key of visual cortex prosthesis is how to transform the original image information into the phosphene array of electrical stimulation which adapted to the visual cortex. The paper discussed the methods of image compression for visual cortex prosthesis especially, and used the wavelet teanstorm method to simplify and compress the image information from the spatial prequency and spatial resolution of image respectively. This paper combined the visual characteristics of the human eye with the system to simulate the pre-processing on the retinal. It makes image processing closer to the visual processing. In addition, the paper established the model of brightness compression by relation characteristic function between phosphenes and stimulation intensity. This model simplified the image brightness infoemation greatly.In addition, the paper also discussed the selection of the image processing system's hardware for the visual cortex prosthesis. Then we introduced a set of image processing system based on DM642, which applied to the visual cortex prosthesis. According to the different conditions and requests between the animal experiment and practically visual prosthesis, the images will be peocessed in different ways. This method increased the expansibility of the system.Finally, a visual cortex in vitro prosthetic device was built combining with 16 channels of electrical stimulation pulse generator in this article. The device will control various channels in electrical stimulation pulse generator to produce corresponding pulse sequences after collecting and processing the picture signal. The transformation of picture signal to visual cortex adapted electrical stimulation signal was achieved by experimental prototype, and the requisition and target was accomplished basically.