Duplex scanning, or two-sided scanning, refers to a scanner's ability to scan both sides of a sheet simultaneously. This feature is not as common as simplex scanning, which just scans one side of a sheet. There are two ways for duplex scanning to occur, including a scanner's use of two cameras or its ability to flip the paper. Two-sided scanning most often is found on duplex multifunction printers (MFPs), though there are some stand-alone scanners that also have this feature. The user usually can switch between duplex and simplex scanning, and the only real advantage is seen in time savings, because this type of scan often takes less time and effort.
The most common type of scanning is simplex scanning, because it is easier to make devices that scan one side and most consumers do not need duplex scanning. When two-sided scanning is used, the scan files can be saved in one of two ways. One way is by splitting the front and back scans into two separate images, which tends to be easier for users to work with. In the second way, the scanner combines the two images into one large image, with the two either side-by-side or one under the other.
To achieve duplex scanning, the scanner can do one of two things. If two cameras are in the duplex scanner, one on the top and one on the bottom, then each can individually scan a side of the paper. The other way is to scan the first side, use the document handler to flip the paper over, and then scan the second side. Both are effective, but the latter tends to be a bit cheaper because less hardware is needed.
Many machines have duplex scanning, but the most common devices are MFPs. Stand-alone scanners also may include this type of scanning, but the vast majority of stand-alone scanners are simplex to keep costs low. If an MFP has duplex printing capabilities, then it generally will have a two-sided scanning feature, but not always. An MFP also may print simplex but scan in duplex.
When someone has a duplex scanning machine, he or she often can switch between the two scanning methods. While duplex scanning may seem better, it is wasted if the user is only scanning a single-sided sheet; this can lead to wasted time and larger scan files. If scanning a two-sided sheet, then this feature can help save time, and less effort will be needed, because the user will not need to manually flip sheets.