Patent ID: 8964256
Filing Date: 2015-02-24
Classification: G03G,H04N

Abstract:
1. A method for compensating for streak defects in images formed by a digital printer having a photoreceptor and a raster output scanner (ROS) device comprising: generating test images on the photoreceptor; sensing the cross-process reflectance of the test images on the photoreceptor; generating reflectance profile data of the test images using the sensed cross-process reflectance; generating low spatial frequency reflectance profile data by low-pass spatial filtering the reflectance profile data; generating high spatial frequency reflectance profile data by high-pass spatial filtering the reflectance profile data; generating a ROS compensation parameter from the low spatial frequency reflectance profile data, the ROS compensation parameter varying in amplitude along cross-process positions in a fast-scan direction in an amount needed to compensate for non-uniformities; generating a spatially varying Tone Reproduction Curve (STRC) from the high frequency reflectance profile data; generating a streak-corrected image using the ROS compensation parameter and using the STRC to modify an input image contone data to derive compensated gray levels used for correcting spatial non-uniformities; generating a first test image set on the photoreceptor; generating first test image set reflectance profile data; generating the ROS compensation parameter from differences between the generated first test image set reflectance profile data and a uniform cross process reflectance profile for the first image set; generating a second test image set on the photoreceptor using the ROS compensation parameter; generating second test image set reflectance profile data from the second test image set; creating the STRC from differences between the generated second image set reflectance profile data and a uniform cross process reflectance profile for the second image set; wherein the digital printer is a color image forming machine using a plurality of separate color channels; generating the first image set by developing first full width test patches including separate gray level patches for each color channel; and generating the second image set by developing second full width test patches including separate gray level patches for each color channel.