CAPACITIVE IMAGING DEVICE WITH ACTIVE PIXELS
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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.
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Citations
36 Claims
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1-20. -20. (canceled)
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21. A capacitive image pixel, comprising:
a three-transistor (3T) sensor comprising a source follower transistor having a gate, wherein the 3T sensor has a charge cycle and a readout cycle, wherein during the charge cycle a first capacitance builds at the gate of the source follower transistor to establish a first gate voltage and wherein during the readout cycle a second capacitance builds at the gate of the source follower transistor to establish a second gate voltage, wherein the difference between the first and second gate voltage is correlative to the nearness of an object. - View Dependent Claims (22, 23, 24, 25)
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26. A capacitive image sensor comprising:
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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 having a gate, wherein the 3T sensor has a charge cycle and a readout cycle, wherein during the charge cycle capacitance builds at the gate of the source follower transistor to establish a first gate voltage; and an insulator layer over the sensor array, wherein during the reading cycle the insulator layer provides a variable capacitance at the gate of each of the source follower transistors, the variable capacitance establishing a second gate voltage, wherein the difference between the first and second gate voltage is correlative to an object being proximate to the insulator layer, the difference within each active pixel used to detect an image of the object. - View Dependent Claims (27, 28, 29, 30, 31, 32)
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33. A method for detecting the nearness of an object comprising:
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initiating a charge cycle within a three-transistor capacitive imaging pixel having a source follower transistor having a gate, an enabling transistor to enable the source follower transistor and a reset transistor to reset the source follower transistor; reading a first voltage at the gate of the source follower transistor; initiating a readout cycle within the pixel; reading a second voltage at the gate of the source follower transistor; and determining the difference between the first voltage and the second voltage, the difference correlative to the nearness of the object. - View Dependent Claims (34, 35, 36)
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Specification