Active pixel sensor and imaging system having differential mode

A method for generating a differential output video signal corresponding to an image focused on an active pixel sensor array, each sensor capable of collecting electrical charge for a detected light intensity and having a diffusion well capable of holding an amount of electrical charge, each diffusion well being buffered from electrical signals external to the sensor, the method comprising the steps of:

• sequentially activating sensors in different portions of the array for a period of time to achieve a desired detected frame interval;
• detecting a first voltage potential at a diffusion node of each activated sensor, wherein each of the first voltage potentials correspond to collected charges held by the respective diffusion wells for the detected image at a corresponding immediate previous frame;
• resetting the voltage potential of the respective diffusion nodes of the activated sensors to a predetermined voltage potential;
• transferring electrical charges collected for a present frame's detected light intensity from the image by each activated sensor to corresponding diffusion wells within the respective sensors, the voltage potentials at the activated sensors' diffusion nodes changing from the predetermined voltage potential to second voltage potentials corresponding to the respective amounts of transferred electrical charges;
• detecting the second voltage potentials at the diffusion nodes of the activated sensors;
• and
• generating an output signal based on sequentially determining the difference between the detected first and second voltage potentials of the activated sensors, wherein the sequential activation of the sensors in each portion of the array generates an output signal of sequential segments of the detected differences in the image at the corresponding pixel sensors between the previous and present frames.

A method for generating a differential output signal from an active pixel sensor corresponding to the difference in the detected light intensity of an image over first and second integration time periods, the sensor having a diffusion well capable of holding an amount of electrical charge based on an amount of detected light intensity by the sensor, the diffusion well being buffered from electrical signals external to the sensor, the method comprising the steps of:

• detecting a first voltage potential at a diffusion node of the active pixel sensor corresponding to a collected charge held in the diffusion well for the light intensity detected during the first integration period;
• resetting the voltage potential of the diffusion node to a predetermined voltage potential;
• transferring electrical charge collected for a present frame's detected light intensity from the image by the active pixel sensor to the diffusion well, the voltage potential at the diffusion node changing from the predetermined voltage potential to a second voltage based on the amount of transferred charge;
• detecting the second voltage potential at the diffusion node;
• and
• generating an output signal based on the difference between the detected first and second voltage potentials taken at the diffusion node for the first and second integration period.

An imaging system for generating a differential output video signal based on an image focused on the imaging system, the imaging system comprising:

• a plurality of active pixel sensors arranged into an array of rows and columns, each active pixel sensor being operable to generate a voltage at a diffusion node corresponding to detected light intensity by the sensor, each active pixel sensor being further operable to buffer the voltage potential present on the diffusion node from other signals generated external to the sensor;
• a row decoder having a plurality of control lines connected to the sensor array, each control line being connected to the sensors in a respective column, wherein the row decoder is operable to activate the sensors in a row;
• a plurality of differential output circuits, each differential circuit being connected to the respective sensors in a column, each differential circuit being operable to store first and second voltage signals received from the connected sensors and to selectively provide a difference sensor output signal to the common output line;
• and
• a timing controller connected to the row decoder and each differential output circuit, wherein the timing controller is operable to cause each sensor row to be sequentially activated, and to cause the activated sensors to provide a voltage signal corresponding to a previous detected frame to the output circuits and then to provide a voltage signal corresponding to a present detected frame to the output circuits, and wherein the timing controller is further operable to cause the differential output circuits to sequentially provide the difference output signal to the common output line to generate the imaging system differential output signal.

An imaging system for generating a differential output video signal based on an image focused on the imaging system, the imaging system comprising:

• a plurality of active pixel sensors arranged in an array, each active pixel sensor being operable to generate a voltage at a diffusion node corresponding to detected light intensity by the sensor, each active pixel sensor being further operable to buffer the voltage potential present on the diffusion node from other signals generated external to the sensor;
• means for sequentially activating sensors in different portions of the array for a period of time to achieve a desired detected frame interval;
• a plurality of differential output circuits, each differential output circuit being connected to the respective sensors in a corresponding portion of the array, each differential circuit being operable to store first and second voltage signals received from the connected sensors and to selectively provide a difference sensor output signal to a system output;
• and
• a timing controller connected to the activating means and each differential output circuit, wherein the timing controller is operable to cause the sensors in each array portion to be sequentially activated, and to cause the activated sensors to provide a voltage signal corresponding to a previous detected frame to the differential output circuits and then to provide a voltage signal corresponding to a present detected frame to the differential output circuits, and wherein the timing controller is further operable to cause the differential output circuits to sequentially provide the difference sensor output signal to the system output to generate the imaging system differential output signal.

An active pixel sensor arrangement having a difference output signal comprising:

• an active pixel sensor being operable to generate a voltage at a diffusion node corresponding to detected light intensity by the sensor, the active pixel sensor being further operable to buffer the voltage potential present on the diffusion node from other signals generated external to the sensor;
• means for activating the sensor for a period of time to achieve a desired detected frame interval;
• a differential output circuit connected to the sensor and being operable to store first and second voltage signals received from the connected sensor and to generate the difference sensor output signal based on the stored voltage signals;
• and
• a timing controller connected to the sensor and the differential output circuit, wherein the timing controller is operable to cause the sensor to provide a voltage signal corresponding to a previous detected frame to the output circuit and then to provide a voltage signal corresponding to a present detected frame to the differential output circuit, and wherein the timing controller is further operable to cause the differential output circuit to generate the difference output signal.