Fixed pattern noise mitigation for a thermal imaging system
AssigneeSeek Thermal, Inc.
InventorsRoss Williams, William J. Parrish, Jason Wolfe
Life of this patent
Estimating the term…
Abstract
An imaging system whose Field of View FOV experiences occasional motion in relation to viewed scenes may be configured to reduce Fixed Pattern Noise (FPN) of acquired image data. FPN may be reduced by developing a pixel by pixel FPN correction term through a series of steps including blurring the image, identifying pixels to exclude from some calculations, a motion detector and an FPN updater for frames under motion and an FPN decay element for frames that are still.
Claims20
A method for reducing Fixed Pattern Noise (FPN) in an imaging system including at least one imaging sensor and associated image signal processing chain, wherein successive frames of image pixel data are generated and passed to the image signal processing chain, and where the Field of View (FOV) of the imaging system is subject to occasional motion relative to imaged scenes, the method comprising:
- selecting a group of pixels Px,y sig, the group of pixels Px,y sig comprising at least a portion of an image frame;
- applying an FPN filter to generate an FPN correction term FPNx,y;
- and
- modifying individual pixels of Px,y sig based at least in part on FPNx,y from a previous image frame to generate a corrected set of pixels Px,y for calculating a value of FPNx,y for the current frame;
- wherein applying the FPN filter comprises:
- blurring at least some of the pixels Px,y to create a blurred pixel set Kx,y and saving the blurred pixel set Kx,y for at least one following frame, wherein Kx,y values are available for the current frame and at least one previous frame during the application of the FPN filter;
- identifying pixels that meet one or more predetermined criteria as excluded pixels for a current image frame;
- detecting image motion by comparing Kx,y values from the current frame and the at least one previous frame;
- calculating, when motion is detected, an updated FPNx,y term based at least in part on Px,y and Kx,y, for current non-excluded pixels and based at least in part on previous FPNx,y information for currently excluded pixels;
- and
- when motion is not detected, decaying FPNx,y for both excluded and non-excluded pixels.
An imaging system with Fixed Pattern Noise (FPN) reduction, the imaging system comprising;
- at least one imaging sensor and associated image signal processing chain, wherein successive frames of image pixel data are generated and passed to the image signal processing chain, and where the Field of View (FOV) of the imaging system is subject to occasional motion relative to imaged scenes:
- a selection element configured to select a group of pixels Px,y sig, the group of pixels Px,y sig comprising at least a portion of an image frame;
- an FPN filter configured to generate an FPN correction term FPNx,y;
- and
- an FPN application element configured to modify individual pixels of Px,y sig based at least in part on FPNx,y from a previous image frame to generate a corrected set of pixels Px,y for calculating a value of FPNx,y for the current frame;
- wherein the FPN filter includes:
- a blurring element configured to blur at least some of the pixels Px,y to create a blurred pixel set Kx,y and to save the blurred pixel set Kx,y for at least one following frame, wherein Kxy values are available for the current frame and at least one previous frame during application of the FPN filter;
- an exclusion element configured to identify pixels that meet one or more predetermined criteria as excluded pixels for a current image frame;
- a motion detection element configured to detect image motion by comparing Kx,y values from the current frame and the at least one previous frame;
- an FPNx,y update element configured to calculate, when motion is detected, an updated FPNx,y term based at least in part on Px,y and Kx,y, for current non-excluded pixels and based at least in part on previous FPNx,y information for currently excluded pixels;
- and
- an FPNx,y decay element configured to decay, when motion is not detected, FPNx,y for both excluded and non-excluded pixels.
Dependencies are inferred from the claim text.