Method and system for camera with motion detection

• US 5,602,585 A
• Filed: 12/22/1994
• Issued: 02/11/1997
• Est. Priority Date: 12/22/1994
• Status: Expired due to Term

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Dickinson, Alexander G., Salata, Jack E.
• Primary Examiner(s): Britton, Howard W.
• Assistant Examiner(s): LEE, RICHARD J
• Application Number:
  US08/363,456
• Time in Patent Office: 782 Days
• Field of Search: 348/143, 348/151-155, 340/527, 340/554, 340/825.3, 340/825.31, 340/825.32, 377/60
• US Class Current: 348/155
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: H04N 5/76 Television signal recording

Abstract

A motion detection camera system which may be used as a security camera includes an active pixel imaging system operable in a video and differential mode connected to a mode activation circuit that controls the imaging system mode. In the video mode, the imaging system generates an output signal containing information of a viewed area on a frame by frame manner. In the differential mode, the imaging system generates a differential output signal containing information consisting of the differences in the viewed area between adjacent detected frames. Normally, the imaging system camera is operated in the differential mode. If no motion occurs in the viewed area, the corresponding differential output signal representing the interframe differences will have a constant signal level. Upon detecting that the differential output signal deviates by greater than a threshold level indicating motion in the viewed area, the mode activation circuit causes the imaging system to operate in its video mode. The corresponding generated video output signal of the imaging system is then provided to monitoring equipment, such as a video cassette recorder for recording of the motion in the viewed area.

Claims

1. A motion detection camera system comprising:

an active pixel imaging system having an output and a mode select input, the imaging system being operable in a differential or video mode based on the signal at the mode select input, wherein the imaging system generates a video signal containing information for each detected image frame of a viewed area when in the video mode and a differential signal containing information of interframe differences when in the differential mode, the imaging system further comprising;

(i) a plurality of active pixel sensors arranged in 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;

(ii) means for sequentially activating sensors in different portions of the array for a period of time to achieve a desired detected frame interval;

(iii) a plurality of output circuits, each output circuit being connected to the respective sensors in a corresponding portion of the array, each output circuit being operable to store first and second voltage signals received from the connected sensors and to selectively provide a sensor output signal to the imaging system output; and

(iv) a timing controller connected to the activating means and each differential output circuit, wherein the timing controller is operable to cause each sensor row to be sequentially activated, and when in a differential mode, 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 when in a video mode, to cause the activated sensors to provide a voltage signal corresponding to a reference voltage 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 output circuits to sequentially provide the output signals to a common output line to generate either of the imaging system output signals;

a switch having an input, first and second outputs and a control input, the input being connected to the imaging system output, the first output being operable to provide a video output signal to a monitoring device;

a threshold detector having an input and an output, the input being connected to the second switch output; and

a mode selector having an input and an output, the input being connected to the detector output, the output being connected to the switch control input and the imaging system mode select input.

2. A method for a motion detection camera system employing an active pixel imaging system operable in a differential or video mode, wherein the imaging system has an array active pixel sensors, each sensor capable of collecting electrical charge based on 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 generated external to the sensor, comprising the steps of:

operating the imaging system in the differential mode to generate an imaging system output signal as a differential signal containing information of the interframe difference of a viewed area, wherein operating in the differential mode comprises the steps of;

(i) sequentially activating sensors in different portions of the array for a period of time to achieve a desired detected frame interval;

(ii) 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 image of the viewed area at a corresponding immediate previous frame;

(iii) resetting the voltage potential of the respective diffusion nodes of the activated sensors to a reference voltage potential;

(iv) 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;

(v) detecting the second voltage potentials at the diffusion nodes of the activated sensors; and

(vi) generating the differential 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 of the viewed area at the corresponding pixel sensors between the previous and present frames;

detecting whether the differential output signal has a signal level that deviates by greater than a threshold value, wherein a deviation in the differential output signal indicates motion within the viewed area;

operating the imaging system in the video mode upon detecting that the differential output signal level has deviated greater than the threshold value, wherein the imaging system generates the output signal as a video signal containing information for detected frame; and

providing the video output signal to a monitoring device.

3. The method of claim 2, wherein the step of sequentially activating sensors in different portions of the array comprises activating the sensors in corresponding sensor rows.

4. The method of claim 2, wherein the step of generating the differential output signal further comprises determining the step of the difference between the detected first and second voltage potentials in the activated sensor row using respective differential output circuits connected to a respective active pixel sensor in each of the portions of the array.

5. The method of claim 2, further comprising the steps of:

storing the first voltage potential of said each activated sensor in a respective one of a first plurality of charge-storage devices; and

storing the second voltage potential of said each activated sensor in a respective one of a second plurality of charge storage devices, wherein the step of generating the output signal includes applying the respective voltage potentials in each of the first and second pluralities of the charge storage devices to a plurality of subtractive signal combiners that sequentially generate the corresponding portions of the differential output signal.

6. The method of claim 2, wherein the step of operating the imaging system in the video mode comprises:

sequentially activating sensors in different portions of the array for a period of time to achieve a desired detected frame interval;

resetting the voltage potential of the respective diffusion nodes of the activated sensors to a reference voltage potential;

detecting a first voltage potential at a diffusion node of said each activated sensor, wherein each of the first voltage potentials correspond to the reference voltage potential;

transferring electrical charges collected for a present frame'"'"'s detected light intensity from the image by said each activated sensor to corresponding diffusion wells within the respective sensors, the voltage potentials at the activated sensors'"'"' diffusion nodes changing from the reference 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 the video 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 image of the viewed area at the corresponding pixel sensors.

7. A motion detection camera system operable in a differential or video mode based on a signal at the mode select input, wherein the imaging system generates a video signal containing information for each detected image frame of a viewed area when in the video mode and a differential signal containing information of interframe differences when in the differential mode, comprising:

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 output circuits, each output circuit being connected to the respective sensors in a corresponding portion of the array, each output circuit being operable to store first and second voltage signals received from the connected sensors and to selectively provide a sensor output signal to the imaging system output; and

a timing controller connected to the activating means and operable to cause each sensor row to be sequentially activated, and when in a differential mode, 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 when in a video mode, to cause the activated sensors to provide a voltage signal corresponding to a reference voltage 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 output circuits to sequentially provide the output signals to a common output line to generate either of the imaging system output signals.

8. A method of operating an imaging system, wherein the imaging system comprises an array of active pixel sensors, each sensor capable of collecting electrical charge based on 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 generated external to the sensor, comprising the steps of:

(i) sequentially activating sensors in different portions of the array for a period of time to achieve a desired detected frame interval;

(ii) 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 image of the viewed area at a corresponding immediate previous frame;

(iii) resetting the voltage potential of the respective diffusion nodes of the activated sensors to a reference voltage potential;

(iv) 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;

(v) detecting the second voltage potentials at the diffusion nodes of the activated sensors; and

(vi) generating the differential 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 of the viewed area at the corresponding pixel sensors between the previous and present frames.

9. The method of claim 8, wherein the step of generating the differential output signal further comprises the step of determining the difference between the detected first and second voltage potentials in the activated sensor row using respective differential output circuits connected to a respective active pixel sensor in each of the portions of the array.

10. The method of claim 8, further comprising the steps of:

storing the first voltage potential of said each activated sensor in a respective one of a first plurality of charge-storage devices; and

storing the second voltage potential of said each activated sensor in a respective one of a second plurality of charge storage devices, wherein the step of generating the output signal includes applying the respective voltage potentials in each of the first and second pluralities of the charge storage devices to a plurality of subtractive signal combiners that sequentially generate the corresponding portions of the differential output signal.

11. The method of claim 8, wherein the step of operating the imaging system in the video mode comprises:

sequentially activating sensors in different portions of the array for a period of time to achieve a desired detected frame interval;

resetting the voltage potential of the respective diffusion nodes of the activated sensors to a reference voltage potential;

detecting a first voltage potential at a diffusion node of said each activated sensor, wherein each of the first voltage potentials correspond to the reference voltage potential;

transferring electrical charges collected for a present frame'"'"'s detected light intensity from the image by said each activated sensor to corresponding diffusion wells within the respective sensors, the voltage potentials at the activated sensors'"'"' diffusion nodes changing from the reference 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 the video 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 image of the viewed area at the corresponding pixel sensors.