US 6,035,072 A · Mapping defects or dirt dynamically affecting an image acquisition device

Abstract

Defects such as dirt, dust, scratches, blemishes, pits, or defective elements or pixels in a CCD, scanner, photocopier, or image acquiring device are dynamically detected by processing a plurality of images via a computer. A pristine object of calibration is not required. Stationary components of the video images are found and detected so as to produce a low false alarm probability. Text segmentation and measurement of total deviation based on variability related to high-frequency components of the video image are employed to prevent applying the process or method to printed text or graphics. Additional techniques optionally employed are median filtering, sample area detection, and dynamic adjustment of scores. In special cases, only moderately blank documents are used. The dynamic defect detection allows defect compensation, defect correction, and alerting the operator of defects.

Claims20

Dependent claims

A method of dynamically detecting defective regions of an image acquisition device that are corrupted by dirt or defects positionally associated with said image acquisition device comprising the steps of:

a) initializing a score target value h to a predetermined number,
b) initializing a map of potential defects P that associates with each defect the number of the image in which it was found,
c) acquiring a serially numbered image numbered q from said image acquisition device,
d) constructing a map of deviant regions from image number q that includes just those regions having at least a predetermined deviation of intensity or color from the surrounding area in said image,
e) adding each deviant region from said map of deviant regions and its image number q to P.
f) scoring each region r in said map of potential defects with a scoring function that is monotonic in positional correspondence between r and other regions P having image numbers differing from q,
g) removing from P regions obsolete relative to said scoring function,
h) detecting as defective regions just those regions that scored at least said score target value h,
i) repeating steps c through h;
whereby the operator may be alerted to the existence and position of defective regions, or said defective regions may be removed from or compensated for in the acquired images.

7 more elements

A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for dynamically detecting defective regions of an image acquisition device that are corrupted by dirt or defects positionally associated with said image acquisition device comprising the steps of:

a) initializing a score target value h to a predetermined number,
b) initializing a map of potential defects P that associates with each defect the number of the image in which it was found,
c) acquiring a serially numbered image numbered q from said image acquisition device,
d) constructing a map of deviant regions from image number q that includes just those regions having at least a predetermined deviation of intensity or color from the surrounding area in said image,
e) adding each deviant region from said map of deviant regions and its image number q to P,
f) scoring each region r in said map of potential defects with a scoring function that is monotonic in positional correspondence between r and other regions P having image numbers differing from q,
g) removing from P regions obsolete relative to said scoring function,
h) detecting as defective regions just those regions that scored at least said score target value h,
i) repeating steps c through h;
whereby the operator may be alerted to the existence and position of defective regions, or said defective regions may be removed from or compensated for in the acquired images.

7 more elements

Dependencies are inferred from the claim text.

Mapping defects or dirt dynamically affecting an image acquisition device

Life of this patent

Mapping defects or dirt dynamically affecting an image acquisition device

Life of this patent

Abstract

Claims20