Abstract: The dynamic range is increased and the noise level is reduced in a bipolar-based active pixel sensor cell with a capacitively coupled base region by forming the capacitor over a portion of the base region and the field oxide region of the cell. In addition, the noise levels are also reduced by heavily-doping the material which forms a portion of the bottom plate of the capacitor with the same conductivity type as the base region of the cell, and by placing the material which forms the portion of the bottom plate in direct contact with the base region.

Abstract: A pixel cell structure having a nonsilicided photodiode overcomes problems associated with the absorption of incident light by silicided surfaces. Furthermore, a photodiode access transistor having a partially silicided gate is interposed between the photodiode and the pixel cell transistors performing reset and row select functions, thereby allowing isolation of the photodiode from leakage associated with silicided junctions. Selective application of voltage to the transistors of the pixel structure according to a clocking sequence permits interaction of the photodiode and the MOS transistors making up the pixel cell, while minimizing exposure of the photodiode to leakage and stress associated with these silicided MOS transistors.

Abstract: An image cell having self-reset which provides improved dynamic range is achieved by having a reset circuit, a comparator circuit and a memory circuit. The image cell operates such that the comparator circuit compares the voltage potential of the image cell with a reference voltage potential. Once the comparator circuit senses that the voltage potential of the image cell transcends the reference voltage potential, the comparator circuit sends a reset signal to the reset circuit. The reset circuit then resets the image cell. Each time the image cell is reset, a reset value is stored in the memory circuit, and the sum of the reset values stored in the memory circuit corresponds to the number of times the image cell has been reset. By resetting the image cell a plurality of times, the dynamic range of a conventional image cell can be increased.

Abstract: A storage pixel sensor disposed on a semiconductor substrate comprises a MOS capacitor storage element having a diffusion terminal and a gate terminal. A speed node is connected to the diffusion terminal and biased at either a first control potential or a second control potential, the first potential selected to keep the MOS capacitor in a state of inversion, the second potential selected to keep the MOS capacitor in a state of depletion. A photodiode has an anode connected to a reference potential and a cathode. A semiconductor reset switch has a first terminal connected to the cathode and a second terminal connected to a reset reference potential. A semiconductor transfer switch has a first terminal connected to the cathode and a second terminal connected to the gate terminal of the capacitive storage element. A semiconductor amplifier has an input connected to the gate terminal of the capacitive storage element and an output.

Abstract: An active pixel image cell which includes a photosensor, active devices for control of the sensor and readout of a signal representing the intensity of light to which the sensor is exposed, and a neuron MOSFET transistor which "both amplifies the signal from the photosensor and" simulates the behavior of a human neuron. An integrated neural network and imaging array may be formed by interconnecting a group of such pixels. Digital signal processing algorithms used for image processing may be implemented at the pixel level by appropriate interconnections between the output signals from the photosensor of surrounding pixels and the neuron MOSFET.

Abstract: An active pixel sensor cell array in which a differential amplifier (whose output is fed back to one of its inputs) amplifies the output of each cell. By using such differential amplifiers, fixed pattern noise in the image data generated by reading the array is reduced. Part of the differential amplifier for each cell is within the cell itself and a current source and tail current sink for the differential amplifier are implemented outside the cell and shared by all cells connected along a column of the array. Preferably, the output amplifier circuitry within each cell includes no PMOS transistor (although it typically includes NMOS transistors). Another aspect of the invention is an active pixel sensor cell including part of a differential amplifier (having an output fed back to one of its inputs, and configured to assert an amplified signal indicative of a sampled output voltage of the cell's photodiode), and circuitry (physically separate from the cell) implementing a remaining portion (e.g.

Abstract: An active pixel sensor cell array in which a two-stage amplifier amplifies the output of each cell. The two-stage amplifier design reduces fixed pattern noise in the image data generated by reading the array, by providing increased gain for the output of each cell without impractically increasing the size and complexity of each cell. For each column of cells of the array, one part of the two-stage amplifier for each cell is shared by all cells of the column, and another part of the two-stage amplifier for each cell is included within the cell itself. Preferably, each cell includes only NMOS transistors (no cell includes a PMOS transistor). In preferred embodiments, a differential amplifier within each cell is the primary stage of the cell's output amplifier, PMOS load circuitry including a secondary output amplifier stage is shared by all cells of the column, and the two amplifier stages for each cell together comprise an op amp.

Abstract: In an active pixel sensor cell, the blue response of the cell is balanced by utilizing a photodiode in lieu of a photogate, and the noise is reduced by quickly reading the voltage on a node, transferring the collected charge from the photodiode onto the node, and then again reading the voltage on the node.

Abstract: The dynamic range of an imaging system that utilizes an array of active pixel sensor cells is substantially increased by reading each cell in the array multiple times during each integration period. Each time a cell is read, the number of photons collected by the cell is saved and the cell is reset if the cell would normally saturate by the end of the integration period. At the end of the integration period, the number of photons collected by each cell is defined by the sum of the values collected during the integration period.

Abstract: The noise in the photo information output from a CMOS-based active pixel sensor cell is reduced by setting the voltage on the output of the cell to a predetermined voltage, such as ground or the power supply voltage, each time the cell is read prior to the cell being read.

Abstract: The accuracy of an active pixel sensor cell is increased by utilizing a reset diode in lieu of the reset transistor that is conventionally used to reset the voltage on the photodiode of the cell. The reset diode, which is largely unaffected by 1/f noise, consistently resets the photodiode to a substantially constant voltage as opposed to the reset transistor which varies the reset voltage on the photodiode across integration periods due to the effect of 1/f noise. In the present invention, the photodiode is formed by forming a well region of a second conductivity type in a substrate of a first conductivity type. The reset diode is then formed by forming a reset region of the first conductivity type in the well region.

Abstract: A MOS-based active pixel sensor cell utilizes the parasitic bipolar action of the cell to produce a horizontal current in lieu of the vertical image current associated with conventional bipolar-based active pixel sensor cells. Image data is collected during an integration period by applying a negative voltage to the gate of the MOS transistor which is sufficient to reverse-bias both the source/body and drain/body junctions. Following this, the image data is read out by raising the gate voltage such that the source/body junction remains reverse-biased, and the drain/body junction becomes forward-biased. Under these bias conditions, an amplified horizontal image current flows from the source, through the body, and out of the drain.

Abstract: Isolation between the heavily-doped active regions of an active pixel sensor cell is provided by utilizing a series of isolation regions which have a doping concentration that is approximately equal to the doping concentration of a low-density drain (LDD) region. A first isolation region of the series, which has the same conductivity type as the active regions, is formed to adjoin a first active region. A second isolation region of the series, which has the opposite conductivity type as the active regions, is formed to adjoin the first isolation region. A third isolation region, which has the same conductivity type as the active regions, is formed to adjoin the second isolation region and a second active region.

Abstract: The stress placed on the silicon lattice of a photodiode during the formation of field oxide regions by the local oxidation of silicon (LOCOS) is eliminated in the present invention by utilizing a negatively-charged layer of polysilicon to isolate the implanted n-type region of the photodiode from the implanted regions of adjacent photodiodes or other devices. In addition, stress is further reduced in the present invention by forming the n-type region of the photodiode with phosphorous, and by lowering the dose such that the n-type region is lightly doped.

Abstract: A correlated double sampling circuit comprising an input node comprising a first plate of input capacitor and an output node. A first plate of a feedback capacitor is connected to the output node and a second plate of the feedback capacitor is connected to a second plate of the input capacitor. An input transistor has a gate connected to the second plate of the input capacitor, a source connected to a first supply voltage rail, and a drain connected to the output node. A load transistor has a gate connected to a bias node, a drain connected to the output node, and a source connected to a second supply voltage rail. A reset transistor is connected between output node and the second plate of the input capacitor, and has a gate connected to a reset signal line.

Abstract: The leakage current at the silicon-to-silicon dioxide interfaces of an active pixel sensor cell is substantially reduced by eliminating field oxide from the cell, and by insuring that, during integration, every surface region of the cell that is not heavily doped is either biased into accumulation or biased into inversion. Each of these states, in turn, substantially limits the number of electrons from thermally-generated electron-hole pairs at the surface that can contribute to the leakage current.

Abstract: The dynamic range is increased and the noise level is reduced in a bipolar-based active pixel sensor cell with a capacitively coupled base region by forming the capacitor over a portion of the base region and the field oxide region of the cell. In addition, the noise levels are also reduced by heavily-doping the material which forms a portion of the bottom plate of the capacitor with the same conductivity type as the base region of the cell, and by placing the material which forms the portion of the bottom plate in direct contact with the base region.

Abstract: A contactless capacitor coupled bipolar phototransistor having an integrated electronic shutter for reducing the overflow and blooming problems associated with the imaging of strong images. Overflow control and an anti-blooming mechanism are obtained by use of a second emitter (the "shutter") which is used to remove excess image generated charge. This prevents the base-emitter junction potential from becoming forward biased during image integration when the phototransistor is exposed to a strong image. The shutter is biased slightly lower than the first emitter of the phototransistor so that the base-shutter junction is forward biased sooner than the base-emitter junction when the imaging element is exposed to a strong image. The overflow current of the generated holes is then drained to the shutter, rather than into the emitter where it would produce noise on the column sense line.

Abstract: The dynamic range is increased and the noise level is reduced in a bipolar-based active pixel sensor cell with a capacitively coupled base region by forming the capacitor over a portion of the base region and the field oxide region of the cell. In addition, the noise levels are also reduced by heavily-doping the material which forms a portion of the bottom plate of the capacitor with the same conductivity type as the base region of the cell, and by placing the material which forms the portion of the bottom plate in direct contact with the base region.

Abstract: The quantum efficiency of a photodiode is substantially increased by forming the photodiode on a heavily-doped layer of semiconductor material which, in turn, is formed on a semiconductor substrate. The heavily-doped layer of semiconductor material tends to repel information carriers in the photodiode from being lost to the substrate, and prevents noise carriers from the substrate from diffusing up into the photodiode. In addition, the red and blue photoresponses are balanced by adjusting the depth of the photodiode.