DETECTION AND HEALING OF STREAKS CAUSED BY DUST IN SHEETFED SCANNERS; MOTOR CONTROL, MODEL BASED HALFTONING, AND PRINT MASK DESIGN USING DIRECT BINARY SEARCH FOR INKJET PRINTERS

<p>In this thesis, I present three research topics in the areas of scanning and printing.</p><p>The first topic is on detecting and removing specific artifacts in images scanned using</p><p>sheetfed scanners. Sheetfed scanners are widely used for scanning stacks of loose pages at</p><p>high speed. The scanhead in the sheet-fed scanners is stationary and the pages are fed with</p><p>an automatic document feeder. When dust particles get stuck onto the scanner glass, they</p><p>reflect the incident light and cause vertical streaks in the scanned images. These artifacts are</p><p>known as dust streaks. I have developed a method for detecting and healing dust streaks.</p><p>The second topic is on motor control system and test page design for inkjet printers.</p><p>Motor control consists of two main parts which are movement of the printhead in the scan</p><p>direction and the process direction. Scan direction movement needs to have a constant</p><p>smooth velocity in order to avoid banding artifacts. Process direction movement needs to</p><p>advance an exact distance in order to avoid misalignment. The full procedure for implementing</p><p>the motor control on a microcontroller, determining optimal parameters, and designing</p><p>test pages for validating the motor control system is presented.</p><p>The third topic is on printer model based halftoning and print mask design using DBS.</p><p>Inkjet printers can fire nozzles at specific pixel locations. Due to nozzle clogging and nonuniformity</p><p>in the nozzles, inkjet printers usually print in the multipass mode to reduce print</p><p>artifacts. In this mode, the printhead goes over the same line more than once with different</p><p>sets of nozzles of the same ink. Print mask determines which pixels are printed at a certain</p><p>pass and which pixels are not printed. I developed a printer model to predict prints and</p><p>also developed test pages to obtain parameters for the printer model. Then, we looked into</p><p>model based halftoning and print mask design using the direct binary search algorithm. In</p><p>addition, I investigated the advantages and disadvantages of using light magenta as opposed</p><p>to using black ink in 4-color printing.</p>