Automatic D.C. offset control for image scanners
AssigneeEastman Kodak Company
InventorsMark E. Stefanik, Martin Potucek
Life of this patent
Estimating the term…
Abstract
A system for calibration and closed loop feedback control of image signals from charge coupled imaging devices (CCDs). During periodic calibration, sampling the output of dark reference cells on a CCD nets an initial D.C. restoration voltage (black) level. Next, a black reference strip is scanned and, an offset value is determined and an offset voltage is added to the D.C. restoration (black) level. During each scan line of regular scanning, dark cells are sampled and produce a voltage that is modified by the offset voltage that was determined during calibration.
Claims24
In a scanner having a photosensitive scanning array for producing a series of analog image signals containing a video component which is characteristic of a scanned image and a D.C. offset component which is characteristic of the scanning array;
- improved means for restoring the image signal to a known D.C. level from which the video component is referenced, said improved means comprising:
- means for periodically scanning a reference region of known reflectivity to produce a scanned value signal;
- means for comparing said scanned value signal to a predetermined value to produce an offset value signal;
- means for periodically producing a signal characteristic of the D.C. offset component of the scanning array;
- means for producing an offset voltage signal from the D.C. offset component signal and said offset value signal;
- and
- means responsive to said offset voltage signal for modifing the image signals.
In a scanner having a photosensitive scanning array for producing a series of analog image signals containing a video component which is characteristic of a scanned image and a D.C. offset component which is characteristic of the scanning array;
- improved means for restoring the image signal to a known D.C. level from which the video component is referenced, said improved means comprising:
- means for periodically scanning a substantially black reference region to produce a scanned value signal;
- means for comparing said scanned value signal to a predetermined value to produce an offset value signal;
- means for producing a signal characteristic of the D.C. offset component of the scanning array;
- means for subtracting the D.C. offset component signal from said offset value signal to produce an offset voltage signal;
- and
- means for adding the offset voltage signal to the image signals to modify the image signals.
A process for restoring a series of scanned image signals containing a video component and a D.C. offset component to a known D.C. level from which the video component is referenced, said process comprising the steps of:
- periodically scanning reference region of known reflectivity to produce a scanned value signal;
- comparing said scanned value signal to a predetermined value to produce an offset value signal;
- periodically producing a signal characteristic of the D.C. offset component of the scanning array;
- producing an offset voltage signal from the D.C. offset component signal and said offset value signal;
- and
- for modifing the image signals in response to said offset voltage signal.
A process for restoring a series of scanned image signals containing a video component and a D.C. offset component to a known D.C. level from which the video component is referenced, said process comprising the steps of:
- periodically scanning a reference region of known reflectivity to produce a scanned value signal;
- comparing said scanned value signal to a predetermined value to produce an offset value signal;
- producing a signal characteristic of the D.C. offset component of the scanning array;
- subtracting the D.C. offset component signal from said offset value signal to produce an offset voltage signal;
- and
- adding the offset voltage signal to the image signals to modify the image signals.
Dependencies are inferred from the claim text.