Low-noise active pixel sensor for imaging arrays with global reset
AssigneePictos Technologies, Inc.
InventorsLester J. Kozlowski, David L. Standley
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Abstract
An imaging array of active pixel sensors uses a reset amplifier in each pixel in a four transistor CMOS implementation. The reset amplifier acts as a variable resistance in the source-follower amplifier feedback circuit. The variable resistance is controlled by a range reset voltage applied to the reset amplifier thereby nulling the photodiode reset noise. The ramp reset voltage is applied to all reset amplifiers of all pixels at the same time, thereby providing for reset of the entire array at the same time, i.e., global reset.
Claims20
An active-pixel sensor including a radiation detector in a plurality of active-pixel sensors organized into a sensor array, said active-pixel sensor comprising:
- a transistor amplifier having an input and an output, its input connected to said radiation detector for generating an electrical signal output having a magnitude that is a function of the charge input from the radiation detector;
- a first switch connected to said transistor amplifier for impressing the electrical signal from said transistor amplifier onto an output line;
- a variable resistance connected between said transistor amplifier and said radiation detector for resetting the charge input of said transistor amplifier to a predetermined signal level;
- and
- a second switch connected to said transistor amplifier and said variable resistance for providing a current source to said transistor amplifier during reset.
An active-pixel sensor including a radiation detector in a two-dimensional array of active-pixel sensors organized into rows and columns of sensors, comprising:
- a transistor amplifier having an input and an output, its input connected to said radiation detector for generating an electrical signal output having a magnitude that is a function of the charge at its input generated by the radiation detector;
- a first switch connected to said transistor amplifier for impressing the electrical signal of its output onto a column output line;
- a variable resistance connected between said transistor amplifier and said radiation detector for resetting the charge at said transistor amplifier input to a predetermined signal level;
- and
- a second switch connected to said transistor amplifier and said variable resistance for providing a current source to said transistor amplifier during reset.
Dependencies are inferred from the claim text.