Flicker reduction in a single camera captured image and smart multi-functional printer motion error analysis
Abstract
Two different topics are discussed in in this dissertation. The first topic is an efficient flicker reduction method in a single camera captured image. The second topic is a smart diagnostic scheme to detect mechanical motion errors of the multifunctional printer. The flicker artifact dealt with in this paper is the scan distortion arising when an image is captured by a digital camera using a CMOS imaging sensor with an electronic rolling shutter under strong ambient light sources powered by AC. This type of camera scans a target line-by-line in a frame. Therefore, time differences exist between the lines. This mechanism distorts a captured image due to the change of illumination. This phenomenon is called the flicker artifact. The non-content area of the captured image is used to estimate a flicker signal that is a key to being able to compensate the flicker artifact. We have developed two different methods to estimate the flicker signal and a measurement method to indicate the strength of the flicker artifact. The measurement is used to determine whether or not flicker suppression needs to be applied to a particular image, and to evaluate the efficiency of our flicker suppression methods. The flicker-reduced images compensated by our methods clearly demonstrate the reduced flicker artifact, based on both visual observation and our numerical measurement. The multifunctional printer(MFP) mentioned in this paper is a device combining the electrophotographic printer, scanner, and copier. Using this smart multifunctionality of the device, we can diagnose the problem of the device by novel techniques used in the image processing and computer vision areas. Our goal is to help customers be able to diagnose their devices as developing automated diagnostic system embedded in products. Among a number of problems customers may encounter, the problems caused by the MFP products' irregular motions are dealt with in this paper. There are several sources cause the motion error in the printing and scanning mechanism such as vibrations in the optical photoconductor(OPC) drum, scanner head, stepper motor, and gear train. The motion errors arising due to the vibrations of the multiple sources are measured by the novel design of our test page. The measured data is observed in the spatial domain to detect the aperiodic motion error as well as in the frequency domain to find out the dominant periodic motion errors. In addition, the measured data is statistically analyzed using a simple trick in order to distinguish the mixed motion errors coming from the printing part and scanning part. Our result briefly expresses the estimated portions of the motion errors between the two parts. Finally, the results are dedicated to diagnose the malfunction of the MFP products.
Degree
Ph.D.
Advisors
Allebach, Purdue University.
Subject Area
Information Technology|Electrical engineering
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