Capacitive imaging device with active pixels
AssigneePalo Alto Research Center Incorporated
InventorJengPing Lu
Life of this patent
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Abstract
An apparatus includes a sensor array with a plurality of active pixels. Each active pixel in the sensor array includes: a three transistor (3T) sensor with a source follower transistor, and a detection diode coupled in series to a parasitic capacitor at a sensing junction. A gate of the source follower transistor amplifier is coupled to the sensing junction. The apparatus includes an insulator layer over the sensor array. The insulator layer provides a variable capacitance to the sensing junctions of underlying active pixels in response to portions of an object being proximate to the insulator layer. The variable capacitance is used to detect an image of the object.
Claims20
A capacitive image sensor, comprising:
- a sensor array comprising a plurality of active pixels, each active pixel in the sensor array comprising:
- a three-transistor (3T) sensor comprising a source follower transistor;
- and
- a detection diode coupled in series to a parasitic capacitor at a sensing junction, wherein a gate of the source follower transistor is coupled to the sensing junction;
- and
- an insulator layer over the sensor array, the insulator layer providing a variable capacitance to the sensing junctions of underlying active pixels in response to portions of an object being proximate to the insulator layer, the variable capacitance used to detect an image of the object.
A method comprising:
- applying a first voltage level to a data line of a three-transistor (3T) sensor of an active pixel in a sensor array, the 3T sensor comprising a source follower transistor with an output coupled to the data line, a gate of the source follower transistor coupled to a sensing junction, wherein a detection diode is coupled in series to a parasitic capacitor at the sensing junction;
- applying a second voltage level to the data line;
- determining a current flowing at the data line in response to the second voltage level being applied;
- determining a variable capacitance of an insulator layer over the active pixel based on the current;
- and
- determining a proximity pattern at the insulator layer based on the variable capacitance.
A method comprising:
- scanning a plurality of active pixels of a capacitive touch sensor, wherein each of the active pixels comprises a three-transistor (3T) sensor, wherein scanning involves performing, for each active pixel, activating an enable transistor of the 3T sensor, and while the enable transistor is activated:
- applying a first voltage level to a data line of the 3T sensor, the 3T sensor comprising a source follower transistor with an output coupled to the data line, the source follower transistor having a gate coupled to a sensing junction, wherein a detection diode is coupled in series to a parasitic capacitor at the sensing junction;
- applying a second voltage level to the data line;
- and
- determining a variable capacitance of an insulator layer over the active pixel based on a current flowing at the data line in response to the second voltage level being applied;
- and
- determining a proximity image based on the variable capacitance measured from each of the plurality of active pixels.
Dependencies are inferred from the claim text.