Pixel cell circuit and implant
A pixel cell circuit comprises an electrode, one or more main photosensitive elements electrically coupled to the electrode for outputting a stimulation signal to the electrode responsive to light illumination, and a shunt arrangement comprising a shunt switch electrically coupled in parallel across the one or more photosensitive elements, and a control arrangement operatively coupled to the shunt switch and configured for placing the shunt switch in an open state responsive to incident light received at the pixel cell and placing the shunt switch in a closed state if no incident light is received at the pixel cell.
1. A pixel cell circuit comprising:
an electrode;
at least one main photosensitive element electrically coupled to the electrode for outputting a stimulation signal to the electrode in response to light illumination;
a shunt arrangement comprising:
a shunt switch electrically coupled in parallel across the at least one main photosensitive element, and
a control arrangement operatively coupled to the shunt switch and configured to place the shunt switch in an open state responsive to incident light received at the pixel cell circuit and place the shunt switch in a closed state if no incident light is received at the pixel cell circuit.
2. The pixel cell circuit according to claim 1 , wherein the shunt switch is one of a micro-electromechanical system device, a nano-electromechanical system device, and a semiconductor-based active component.
3. The pixel cell circuit according to claim 1 , wherein the shunt switch is a semiconductor-based active component selected from a group that includes field-effect transistors and bipolar transistors.
4. The pixel cell circuit according to claim 1 , wherein the control arrangement is configured to place the shunt switch in the open state responsive to incident light received at the at least one main photosensitive element and place the shunt switch in the closed state if no incident light is received at the at least one main photosensitive element.
5. The pixel cell circuit according to claim 1 , wherein the control arrangement comprises an auxiliary photosensitive element, and is configured to place the shunt switch in the open state responsive to incident light received at the auxiliary photosensitive element and place the shunt switch in the closed state if no incident light is received at the auxiliary photosensitive element.
6. The pixel cell circuit according to claim 1 , wherein the control arrangement comprises:
a switch control arrangement;
a power supply arrangement configured to supply power to the switch control arrangement;
a timing control arrangement configured to generate a timing signal to the switch control arrangement;
wherein the switch control arrangement is configured to control the shunt switch based on the timing signal.
7. The pixel cell circuit according to claim 6 , wherein the electrode and the at least one main photosensitive element are connected to each other by a node and the power supply arrangement comprises:
a supply switch; and
a storage capacitor having a first terminal electrically coupled to a reference potential of the pixel circuit, and a second terminal electrically coupled to the node through the supply switch, wherein the switch control arrangement is further configured to control the supply switch based on the timing signal.
8. The pixel cell circuit according to claim 7 , wherein the switch control arrangement is configured to open the shunt switch then close the supply switch responsive to the timing signal indicating that incident light is received at the pixel cell circuit, and to open the supply switch then close the shunt switch responsive to the timing signal indicating that incident light is no longer received at the pixel cell circuit.
9. The pixel cell circuit according to claim 6 , wherein the timing control arrangement comprises an auxiliary photosensitive element and a load electrically coupled to each other in series, wherein the load is electrically coupled to a node connecting the electrode and the at least one main photosensitive element.
10. The pixel cell circuit according to claim 1 implemented using CMOS compatible components.
11. A neural implant, comprising an array of at least one pixel cell, each of the at least one pixel cell comprising a pixel cell circuit according to claim 1 .