Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
1998-05-05
2001-07-17
Grant, II, Jerome (Department: 2624)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S413000, C358S498000
Reexamination Certificate
active
06262816
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical scanner using sweeping scan.
BACKGROUND OF THE INVENTION
Optical scanners are capable of producing a representation of the image of an original by projecting an image of the original onto an optical sensor by means of an optical system. The optical sensor thereby provides a signal which represents the image of the original, or a part thereof as intensity levels.
In a practical embodiment the optical sensor is provided as a line detector. But, due to the fact that a line detector is capable of imaging only one scan line on the original at a given point in time, the original is moved past the line detector at a feed rate in order to obtain an image of the entire original, that is the original is scanned. Alternatively the line detector may be moved past the original at a given feed rate.
Various types of photosensor devices may be used as a line detector, e.g. charge coupled devices (CCD's). A CCD builds up an electrical charge in response to the exposure to light. The magnitude of the electrical charge built up is dependent on the intensity are the duration of the light exposure. The intensity of a picture element (pixel) on the original is imaged by a CCD cell. The charge built up in each CCD is sampled and discharged at sampling intervals. Typically the CCD's axe sampled at regular sampling intervals, i.e. at a constant sampling rate. Each sample represents the imaged intensity of a pixel.
The object of scanning an original is to detain a digital representation of the information comprised by the original. The digital representation it typically stored or otherwise processed on a computer that has access to some type of storage media e.g. a harddisc drive. The computer is typically involved in executing a number of different tasks that require varying computational efforts. The computer is thus exposed to a varying load. Therefore, in some situations the computer will be able to receive data at a high rate and in other situations the computer will be able to receive data at a low rate. In some situations transmission of data from the scanner to the computer may be halted for a period of time.
In order to overcome the problems associated with data transfer from the scanner to the computer due to the varying capability of the computer to receive data, a number of methods have been proposed.
A first method suggests that the scanner is provided with an internal buffer that is large enough to hold the entire image representation produced by a scan. The scanning of the original is thereby not affected by the varying capability of the computer to receive data. This method is useful for desktop scanners, but for large format scanners producing images of a size varying from 500 to 1000 megabytes it is not feasible.
A second method suggests that the scanner is operated in intervals, such that the scanner scan at a nominal feed rate while the computer is able to receive data, and when the computer is not able to receive more: data or at least not able to receive data at a maintained data rate, the scanner is halted. However, when the scanner is halted and afterwards when the scanning is resumed, mechanical vibrations caused by displacement means starting abruptly results in distortion of the digital representation of the scanned original. Therefore, this method requires that the scanner is so mechanically stable that no image distortion occurs when the scanner stops and starts. This is possible for slow speed scanners, but for fast scanners that scan at a feed rate larger than 2 inch/second this solution is not feasible.
A third method suggests that the original is initially scanned at a nominal feed rate thereby generating data transferred to the computer at a first data rate. If the computer is not capable of receiving data at this first data rate, the scanning is stopped and then restarted to scan the original at a lower feed rate, thereby generating data transferred to the computer at a second and lower data rate. This is continued until scanning of the entire original succeeds. This method is useful, but it may cause the scanning of an original to take a long time because the scanning is stopped and restarted repeatedly, if a relative low date rate is required for the transfer of data from the scanner to the computer.
SUMMARY OF THE INVENTION
The primary object of the invention is to provide an optical scanner which is capable of stopping and starting scanning even at high feed rates without requiring the scanner to have excessive large internal buffers or to have high mechanical stability, and avoiding time consuming rescans.
There is provided an optical scanner collecting information from an original by means of sweeping scan, said scanner comprising: a line detector for registering intensity information from lines on the original, thereby providing an image signal comprising a succession of line signals; said line detector providing data to a memory; displacement means for displacing the original and said line detector relative to each other at a feed rate; control means for controlling the magnitude of said feed rate; said feed rate being adjusted according to the following rule: if said feed rate is less than a predetermined value and if said memory has capacity for more data, then said feed rate is increased by a value that is a fraction of said predetermined value.
Further, there is provided an optical scanner collecting information from an original by means of sweeping scan, said scanner comprising: a memory; a line detector, said line detector registering intensity information from lines on the original thereby providing an image signal comprising a succession of line signals, said image signal providing data to said memory at a data rate; displacement means for displacing the original and said line detector relative to each other at a feed rate; control means for controlling the magnitude of said feed rate, said feed rate being adjusted according to a procedure comprising a first step: if said memory has capacity for a higher data rate and if said feed rate is less than a preferred value, said feed rate is increased by a value that is a fraction of said preferred value.
Still . . . further, there is provided an optical scanner collecting information from an original by means of sweeping scan, said scanner comprising: a line detector for registering intensity information from lines on the original, thereby providing an image signal comprising a succession of line signals, said image signal being generated at a data rate; displacement means for displacing the original and said line detector relative to each other at a feed rate; a memory; a data processor to convert said image signal into a modified image signal, said data processor reducing the number of line signals from said image signal while said feed rate is below said predetermined value, said modified image signal providing data to said memory; control means for controlling the magnitude of said feed rate, said feed rate being adjusted according to a procedure comprising a first step: if said memory has capacity for a higher data rate and if said feed rate is less then a preferred value, then said feed rate is increased by a value that is a fraction of said preferred value.
It is thereby possible to reduce mechanical vibrations to a non-significant level by slowly raising the feed rate of the scanner until it reaches a nominal scanning speed. It is further possible to reduce the feed rate slowly.
REFERENCES:
patent: 5703968 (1997-12-01), Kuwahara
patent: 5710634 (1998-01-01), Kuriyama
patent: 5943139 (1999-08-01), Tang
Rasmussen Jörgen
Rindsig Michael
Context A/S
Grant II Jerome
Merchant & Gould P.C.
Worku Negussie
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