HP M1522nf Service Manual - Page 68

Scanner and ADF functions and operation The following sections describe how the document scanner and the automatic document feeder (ADF) function. Scanner functions The scanner uses a light source, a color-separation method, and a charge-coupled device array (CCD) to collect optical information about the document and transform that into an image file. The scanner consists of these elements: ● A lamp (LED) ● Five mirrors and a lens ● A CCD Figure 4-2 Optical system Scanner Glass LED Lam p CCD Lens The scanner lamp illuminates a small strip of the document (called the raster line). The mirrors direct the light through the lens to the CCD. The CCD senses and records the light, creating an analog representation of the raster line. If the ADF is being used, the document then advances in the ADF to the next raster line. If the flatbed is being used, the scanner module advances to the next raster line. This advancing and collection process continues to the end of the sheet. The image data is collected in the motor controller board, where it is processed and sent to the formatter. The formatter then handles the image data, outputting it as a copy, sending it through the fax card as a fax, or directing it to the computer as scanner output. The resolution of the image data collected depends on the task being performed. Each pixel has 8 bits for each of the three colors (256 gray scale levels for each color), or a total of 24 bits per pixel (24-bit color). 50 Chapter 4 Operational theory ENWW