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 for receiving a pixelized image;
a plurality 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 plurality of electrodes, wherein a set of at least three not linearly placed electrodes are stimulated at a first set of levels to create a percept at a first location between said at least not linearly placed electrodes, and said set of at least three not linearly placed electrodes are stimulated at a second set of levels to create a percept at a second location between said at least not linearly placed electrodes, different from said first location;
wherein said first set of levels and said second set of levels are determined based on mapping said first location and second location from different pixels in said pixelized image.
2. The visual prosthesis according to claim 1 , wherein said first set of levels are equal levels on each of said at least three non-linear electrodes.
3. The visual prosthesis according to claim 1 , wherein said at least three non-linear electrodes have the same polarity.
4. The visual prosthesis according to claim 1 , wherein said at least three non-linear electrodes stimulate with balanced biphasic pulses.
5. The visual prosthesis according to claim 1 , wherein pixels from said pixelized image are mapped to said at least three non-linear electrodes as multiple signals in rapid succession such that they form the perception of a single image.
6. The visual prosthesis according to claim 1 , wherein some pixels 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.
7. The visual prosthesis according to claim 1 , wherein varying signals from said at least two electrodes create the perception of light at varying locations between said at least two electrodes.
8. The visual prosthesis according to claim 1 , wherein said multiple signals are repeated within one fiftieth of a second.