Field focusing and mapping in a visual prosthesis
The present invention is a system for mapping a high resolution image to a lower resolution electrode array and, by applying varying stimulus to neighboring electrodes, creating a perceived image greater in resolution than the electrode array. The invention is applicable to a wide range of neural stimulation devices including artificial vision and artificial hearing. By applying a sub-threshold stimulus to two neighboring electrodes where the sum of the stimuli is above the threshold of perception, a perception is created in neural tissue between the two electrodes. By adjusting the stimulus on neighboring electrodes, the location of stimulation can be altered. Further, noise can be applied to the stimulating electrode or its neighboring electrodes to reduce the threshold of stimulation.
1. A visual prosthesis comprising:
a camera receiving an image and generating a pixelized image;
a two dimensional array of electrodes suitable for contact with neural tissue; and
an image processing circuit configured to receive said pixelized image from said camera and configured to map said image to said two dimensional array of electrodes, said image processing circuit configured to drive an electrode to create a percept in a direct location, drive at least two adjacent electrodes, within said two dimensional array of electrodes, at a first set of levels, based upon said pixelized image, to create a percept at a first location, different from said direct location, between said at least two adjacent electrodes, and configured to drive said at least two adjacent electrodes at a second set of levels, based upon said pixelized image, to create a percept at a second location between said at least two adjacent electrodes, different from said direct location and said first location;
wherein each of said direct location, said first location and said second location are mapped from different pixels in said image.
2. The visual prosthesis according to claim 1 , wherein said first set of levels are equal levels on each of said at least two adjacent electrodes.
3. The visual prosthesis according to claim 1 , wherein said at least two adjacent electrodes have the same polarity.
4. The visual prosthesis according to claim 1 , wherein said at least two adjacent electrodes stimulate with balanced biphasic pulses.
5. The visual prosthesis according to claim 1 , wherein pixels forming said pixelized image are mapped to said at least two adjacent electrodes as multiple signals in rapid succession such that the pixels form the perception of a single image.
6. The visual prosthesis according to claim 5 , wherein said multiple signals are repeated within one fiftieth of a second.
7. The visual prosthesis according to claim 1 , wherein pixels from said pixelized image are mapped to said plurality of electrodes wherein a signal from an individual of said plurality of electrodes is insufficient to create the perception of light, but the sum of signals from said plurality of electrodes is sufficient to create the perception of light.
8. The visual prosthesis according to claim 1 , wherein varying signals from said at least two adjacent electrodes create the perception of light at varying locations between said at least two adjacent electrodes.