(^562) PC Hardware: A Beginner’s Guide
High-endvideoconferencingcardscanbeaddedtoaPCsystemtomakeitintoaninter-
active videoconferencing stations. The typical system will have a digital camera, which
plugs into the videoconferencing card, and a microphone, which most PC systems are al-
ready equipped with. Low-end systems designed for personal use over the Internet are
available for less than $200 virtually everywhere computer supplies are sold.
Image Capture
The objectives of image capture are not unlike those of audio capture. In both cases, the
purpose is to convert analog information such as a photograph or a human voice into digi-
taldatathatcanbestoredandeditedonacomputer.WhilenotyetasuniversalasPCsound
systems, image capture devices have increased in popularity with the rise of the Internet
and have quickly become essential tools for developing visual content for Web pages.Scanners
Scanners are devices for capturing still images. The scanner uses a light source that reflects
off the image being captured, and information about the reflected image is digitized and sent
to software where it can be stored, edited, or printed. Scanners are available in a wide variety
ofconfigurations,whichcanbecategorizedaccordingtodifferentimagingmethods,howthe
scanner’s interface with the PC, and how the original image is delivered to the scanner:Imaging Method
A scanner, regardless of whether it is handheld or flatbed, uses one of three methods to cap-
tureandreproducetheimageofthedocumentitscans.Thethreeimagingmethodsusedare: Photomultiplier Tube (PMT) This type of scanner uses a vacuum tube to
convert light reflected from the scanned image into an amplified electrical
signal that is sent to the PC. PMT scanners are more expensive and generally
more difficult to use than CCD scanners (discussed next). They are typically
reserved for high-end applications.
Charge-Coupled Device (CCD) This category of scanner includes the
general-purpose scanners used in homes and offices. A CCD is a small
solid-state sensor that converts light into an electric charge, which is then
converted into digital data that can be stored on a PC. A CCD scanner uses
literally thousands of CCDs in an array that scans the entire surface of the
image. More CCDs in the array translates into a higher maximum resolution
for scanned images.
Multipass vs. Single Pass Multipass scanners collect color data using multiple
passes of the light source and CCD array over the surface of the image. Multiple
scans are required because a single scan is required for the red, green, and blue
information on the page. At the end of the three passes, the collected color