1. 4/14: Scanners Roll Call Response to request Lecture: scanners –general –flatbed –sheet-fed –hand-held –OCR Image courtesy of Microtek www.mteklab.com

2. Other business Recurring themes: –“I studied, and got a good grade.” –“I didn’t study, and got a lousy grade.” –“The exam questions are straight from the notes and class discussions.” –“Some people thought that this would be a blow-off class. It’s not.” –“Coming in for a review session during office hours really helped.”

3. Scanners - general Allows a PC to convert printed images into digital code. Transforms light into voltage levels, and then into computer code. Pictures appear courtesy of Microtek www.mteklab.com

4. Scanners - how they work. We will use a flatbed scanner as an example to discuss how a scanner works. Image courtesy of Mustek http://www.mustek.com.tw

5. Scanners - Light Shines. A paper is placed face-down on the glass of the scanner. A light shines on the paper. The paper reflects the light to a mirror which bounces it to a light-sensing diode. Diagram courtesy of Mustek http://www.mustek.com.tw/Support/html/scannings.html DIODE

6. Scanners - Reflection. The image on the paper reflects different amounts of light, depending on how dark or light the image is. Diagram courtesy of Mustek http://www.mustek.com.tw/Support/html/scannings.html DIODE

7. Scanners - Dots Per Inch The light-sensitive diode records the information for each tiny area of the page. These areas are measured in DPI, or Dots Per Inch. Note that this is a linear unit, not an area unit (i.e. miles versus square miles) Diagram courtesy of Mustek http://www.mustek.com.tw/Support/html/scannings.html DIODE

8. Scanners - total sampling. If a scanner is set at 300 dpi x 300 dpi, how many individual samples of light would it take in a 2 in. x 1 in. area? 2 square inches * 300 dpi * 300 dpi = 180,000 dots total. 2 inches 1 inch 300 dots per inch * 2 inches *300 dots per inch * 1 inch 180,000 dots total

9. DPI: Horizontal & Vertical. Scanners have two dimensions to their resolution: the horizontal and the vertical. The horizontal is determined by the light- sensing diode’s sensitivity and precision. The vertical is determined by the speed that the scan head moves. Image courtesy of Mustek http://www.mustek.com.tw http://www.mustek.com.tw/html/prod/pns600a3e.html

10. Scan Heads. A motor moves the scan head beneath the page. The scan head consists of the light source and a mirror that bounces the reflected light to the lens of the light- sensing diode. Image courtesy of Mustek www.mustek.com.tw

11. The Lens Focuses on the Diode. A lens focuses the reflected light for the light-sensing diode. The diode converts the light to voltage. The more light sensed, the more voltage is produced.

12. Our old pal, the ADC. An analog to digital converter (ADC) stores each analog reading of voltage as a digital pixel. Color depth is the number of bits that are stored for each pixel. Pictures appear courtesy of Mustek http://www.mustek.com.tw/Support/html/scannings.html 1 bit line art 1 bit halftone 8-bit grayscale24-bit color

13. Color Scanning If it is a color scanner, the light is directed through red, green, and blue filters. Each dot has three values recorded for it: the red level, the green level, and the blue level.

14. Off We Go. The digital information is sent on to the rest of the computer. Pictures appear courtesy of Microtek www.mteklab.com

15. Sheetfed Scanners These scanners move the paper past the scan head, rather than moving the scan head past the paper. Image courtesy of Visioneer www.visioneer.com

16. Handheld Scanners These scanners use the human hand as the motor. They are generally smaller, and scan about half a page at a time. Image courtesy of Hewlett Packard www.hp.com

17. OCR: Optical Character Recognition OCR (optical character recognition) –software that lets you convert printed type into editable text. Lorem Ipsum