Abstract: An active CMOS pixel or pixel array and method for manufacturing uses silicides to improve sheet conductivity of polysilicon and diffusions and for improved conductivity of silicon to metal connections without downgrading the photon sensing performance of the pixels. Masks are used in manufacturing of the pixels by selectively masking photon sensors from the optical opaqueness of silicides and photon sensor related circuit elements from silicide induced photon sensor dark current leakage while allowing formation of silicides for providing highly conductive contacts between. Silicides are used for improving the sheet conductivity of polysilicon and diffusions in the readout transistors and for improved conductivity of silicon to metal line connection pads.

Abstract: The blue signal of a CMOS-based color pixel is increased with respect to the red and green signals by lowering the doping concentration of the surface regions of the pn-junction photodiodes that are used in the blue imaging cells with respect to the surface regions of the pn-junction photodiodes that are used in the red and green imaging cells.

Abstract: In a first embodiment an active pixel sensor includes a photodiode for capturing photocharge, a reset transistor for resetting the photodiode to a reset potential, and a readout transistor, and in a second embodiment an active pixel sensor includes a photodiode for capturing photocharge, a reset transistor for resetting the photodiode to a reset potential, a transfer transistor for transferring captured photocharge, and a readout transistor. In both embodiments, the readout transistor has a drain that is coupled to a first supply voltage during integration of photocharge and a second supply voltage during readout of the photocharge. Accordingly, the sensitivity of an active pixel sensor is increased by increasing the fill factor, the noise an active pixel sensor is reduced by increasing the relative size of the readout transistor, and the gain is compressive as the relative light intensity in an active pixel sensor increases.

Abstract: An imaging array having overflow protection and electronic shuttering features is realized without an increase in pixel complexity. Overflow protection is provided by pulsing each row of the imager with a small overflow pulse during the sense amplifier reset phase. An electronic shutter is realized using a modified version of the pixel readout timing. The shutter provides sub-frame exposure by restricting the number of line-times a pixel is allowed to integrate. For a full-frame exposure, each pixel is read out once per frame; during readout of the other rows of the array, the pixel integrates. For subframe exposure, the pixel is continually reset, using a shutter pulse applied to the row lines during sense amplifier reset, until a certain number of rows (line-times) before it is to be read out. The pixel then is allowed to integrate until it is read out normally.

Abstract: A color separating prism is disclosed for use in an electronic imaging systems such as a video or digital still-image camera. The prism separates an incoming light beam into red, green and blue light components and directs the separated light components onto adjacent imaging sensors. Beam-splitting interfaces of the prism are optically configured to admit approximately ten to twenty percent of a violet light contained in the incoming light beam into the red color channel. The prism may beneficially be optically coupled to a light-rejecting filter or mirror which rejects undesired far-red, far-violet and blue-green components of the light beam. In this manner, the resultant red, green and blue channels approximate a set of substantially non-negative color matching functions to facilitate highly colorimetrically accurate color imaging and thereby reduce or eliminate the need for post-imaging color correction.

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.

Abstract: A storage pixel sensor comprises a photosensor selectively connectable to a reset potential; a switched buffer amplifier having a control terminal coupled to said photosensor, a first terminal connected to a source of a transfer signal, and a second terminal; a storage capacitor coupled to said second terminal of said switched buffer amplifier; and an amplifier coupled to said storage capacitor.

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 extracted from an active pixel sensor cell is reduced by resetting the voltage on the photodiode of the cell to the power supply voltage, and by reading the cell immediately before and after the cell is reset. The voltage on the photodiode is reset to the power supply voltage by applying a reset voltage to the gate of the reset transistor conventionally used to reset the photodiode where the reset voltage is sufficiently larger than the power supply voltage to cause the voltage on the photodiode to be pulled up to the power supply voltage.

Abstract: The present invention relates to a pixel cell and pixel cell array modified to improve performance. One improvement taught by the present invention is implantation of dopant into the silicon to form the base region after formation of polysilicon, resulting in highest base dopant concentrations lying at the thin oxide and emitter interfaces. A second improvement taught by the present invention is a reduction in the size of the heavily doped portion of the emitter to extend no further than the footprint of the emitter contact, thereby inhibiting leakage between the emitter and adjacent polysilicon. A third improvement taught by the present invention is electronic isolation of pixel cells by inter-pixel regions doped with conductivity-altering impurity of a type opposite that of the base rather than by field oxides, thereby eliminating leakage at the field oxide edge.

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: A digital imager apparatus uses the differences in absorption length in silicon of light of different wavelengths for color separation. A preferred imaging array is based upon a three-color pixel sensor using a triple-well structure. The array results in elimination of color aliasing by measuring each of the three primary colors (RGB) in each pixel in the same location.

Abstract: An active pixel image cell which includes a photosensor and an embedded memory element and may be used to produce signals corresponding to the photosensor outputs for successive frames. The structure of the active pixel cell includes an analog, non-volatile, or dynamic memory element and the control elements needed to store the output of the photosensor generated during a previous frame. The pixel elements then generate a signal representing the current frame output of the photosensor. The current frame output and previous frame output are then provided as output signals for the pixel and may be subjected to off-pixel processing as desired. For example, the two values may be subtracted from one another by an off-pixel difference amplifier to form a signal representing the difference between the image on the photodiode sensor of the pixel between successive frames. The difference signal may then be used for purposes of video compression, motion detection, or image stabilization.

Abstract: A 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.