Facsimile and static presentation processing – Facsimile – Picture signal generator
Patent
1997-08-27
1999-12-21
Mancuso, Joseph
Facsimile and static presentation processing
Facsimile
Picture signal generator
382313, 358474, H04N 1024, H04N 104, G06K 922
Patent
active
060056819
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates generally to devices and methods for forming scanned electronic images of originals and more particularly to scanning devices and methods that permit reconstruction of images from image swaths obtained during image capture.
BACKGROUND ART
Scanners for electronically forming an image of an original are known. Typically, the captured image provided by a scanner is a pixel data array that is stored in memory in a digital format. A distortion-free image requires a faithful mapping of the original image to the pixel data array. Scanners typically include at least one means for imposing a mechanical constraint during the image capture process in order to maximize the likelihood of faithful mapping. The four types of scanners known in the art are drum scanners, flatbed scanners, two-dimensional array scanners and hand scanners. 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. At any moment during the imaging process, the current position within the pixel data array relative to the original can be determined by measuring the angular position of the drum and the translational position of the sensor. The position of the pixel data array with respect to the original is fixed as long as the original is properly attached to the drum, the drum rotation is properly controlled, and the sensor is properly controlled in its displacement along the linear path.
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. Thus, the position of the sensor in one dimension may be known by tracking the relative movement of the sensor. The position of the sensor in the perpendicular direction is implicitly fixed by addressing a particular array element at which intensity is to be measured. In one embodiment of the flatbed scanner, the original is placed on a transparent platen and the sensor, along with an image illumination source, is placed on a side of the platen opposite to the original. As long as the original is not moved relative to the platen, the pixel data array will be fixed with respect to the image to be captured. In another embodiment, the original is moved, rather than the sensor. This second embodiment is typical of facsimile machines. Precision paper transports pro-vide a high degree of positional accuracy during the image-capture process.
Advantages of the drum and flatbed scanners include the ability to accommodate documents at least as large as A4, or 8.5".times.11" paper. Moreover, some of these scanners can handle A1 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.
Two-dimensional array scanners may be used in the absence of mechanical encoding constraints, and require only that the array and the original be held motionless during an exposure period. A two-dimensional array of photosensitive elements directly accomplishes the mapping of the image of the original into a pixel data array. However, because a single 300 dpi mapping of an 8.5".times.11" original requires an image sensor having an array of 2500.times.3300 elements, i.e. 8.25 million pixels, these scanners are cost-prohibitive in most applications.
Conventional hand scanners require a user to move a linear array of electrooptical sensor elements over an original. The movement is by hand manipulation. Array-position information is determined using methods such as those employed in operation of a computer "mouse." As a linear sensor array is moved, the rotation of wheels, balls or rollers that are in contact with the original is sensed, and the position information is determin
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Hewlett--Packard Company
Mancuso Joseph
Truong Hien
LandOfFree
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