Flatbed scanners include a linear array sensor that is moved relative to the original along an axis that is perpendicular to the axis of the array. Flatbed scanners are configured similar to a copier. With a flatbed scanner, a document to be scanned is typically placed onto a transparent glass platen of the scanner, where a scanner head assembly moves underneath the document to capture the image contained on the document. The image in digital form is often transmitted to a connected computer, or transmitted directly to another peripheral such as a printer or facsimile machine. Drum scanners attach the original to the surface of a cylindrical drum that rotates at a substantially fixed velocity. During the rotation of the drum, an image sensor is moved in a direction parallel to the rotational axis of the drum. The combination of the linear displacement of the image sensor and the rotation of the original on the drum allows the entire original to be scanned. Advantages of the drum and flatbed scanners include the ability to accommodate documents at least as large as A4. Some of these scanners can handle Al paper in a single setup. However, the scanners are not generally portable, since they require a host computer for control, data storage and image manipulation. As portable electronic apparatuses has been achieved through the result of technological advances in areas such as display devices, batteries, and memory devices, many people seek peripherals for use with portable computers such as laptop computers and personal digital assistants. Accordingly, incorporating a very small document scanner into a laptop or PDA, or attaching a document scanner to a laptop or PDA, would significantly enhance their usefulness for data entry.

A handheld or portable optical scanner is an optical scanner which is designed to be moved by hand across the object or document being scanned. Today, a hand scanner is extensively used with a personal computer or a word processor as an image inputting device for optically reading image data out of a document by being operated by hand. Handheld scanners have been used for a number of applications, such as for barcode readers at points-of-sale of products or services, for recording data appearing on original documents for later reproduction or processing, and for translating documents. Handheld scanners can be classified as general purpose or special purpose. Most handheld scanners used for acquiring information from printed media are directed to general purpose uses, so that they can read and store a variety of different types of image information designed for various applications. The other category of handheld scanners is directed to the scanning of very specific types of images to provide a particular form of information. The best known type of scanner in this category is a bar code scanner, which might be used to obtain the identification of a product which carries the bar code image. Portable image scanners can also be classified into a manually scanning type for manually moving the scanner along an image face of a document to be scanned, and an automatic scanning type for automatically moving a given document moved relative to the scanner to read out the image on the document. The handheld scanner may be connected directly to a separate computer by a data cable. The data signals produced by the hand-held scanner may be transferred to a computer as the image data are collected. Alternatively, the handheld scanner may include an on-board data storage system for storing the image data. The image data may then be downloaded to a separate computer after the scanning operation is complete by any convenient means, such as via a cable or an optical infrared data link.

A typical handheld optical scanner may include illumination and optical systems to accomplish scanning of the object. The illumination system illuminates a portion of the document, whereas the optical system collects light reflected by the illuminated scan region and focuses a small area of the illuminated scan region onto the surface of a photosensitive detector positioned within the scanner. Present commercially available handheld document scanners generally use an optical diode array or a charge coupled device (CCD) for converting an optical image into an electronic signal. A typical CCD may comprise an array of individual cells or pixels, each of which collects or builds-up an electrical charge in response to exposure to light. A roller, gear and encoder mechanism is also included in the handheld document scanner to synchronize image data acquisition by the CCD with mechanical movement of the scanner across the document. A handheld scanner device may be provided with a position sensing or navigation system in order to determine the position of the handheld scanner with respect to the object being scanned. The position correlation allows a complete image of the scanned object to be produced even though the scanner may not scan the entire object during a single pass. Handheld document scanners usually indicate on a display screen of the computer if scanner motion is too fast for image capture. Some hand scanners use electromagnetic brakes to prevent the user from dragging the scanner over the image too rapidly, with the mechanical resistance increasing with increases in scanning speed.

Handheld scanners utilize relatively small imaging arrays and generally cannot handle larger than A6 documents in a single pass. This requires stitching algorithms to join together multiple swaths of a larger document. The advantages of the hand scanner are its small dimensions and, in particular, its portability. Disadvantages, however, occur due to the guidance by hand with regard to straight, rectangular guidance over the page to be scanned, uniform speed, uniform applied pressure and overlapping when scanning at least two scanned columns. The image quality of a scan performed with a handheld scanner is largely dependent on the steadiness and alignment of the scan pass. Because of storage requirements of images, handheld scanners are limited to small numbers of documents before transmission is necessary.