Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
1998-06-05
2001-02-20
Lee, Cheukfan (Department: 2722)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S496000, C358S498000, C358S474000
Reexamination Certificate
active
06191871
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image-reading method and apparatus in which, while a reading member is being transported relative to an original document by moving a document platen or shifting an optical system, the original document is scanned in the orthogonal direction to the transporting direction so as to read the original image.
BACKGROUND OF THE INVENTION
An image reading section is installed in apparatuses such as a facsimile machine, a copying machine and an image scanner serving as a peripheral device of a personal computer. In such an image reading section, a method is adopted in which an original image is read while a reading member is being transported relative to an original document as described above. Here, in the image reading section, normally, the discrimination F (mm/step), which corresponds to the amount of feed of the original document per 1 step of a feeding motor, and the resolution P (mm/line) of the reading member are coincident with each other. Therefore, in an apparatus such as the above-mentioned facsimile machine, when the feeding motor makes one revolution (step), the reading member also carries out one reading operation for one (line).
However, alternation of the resolution P is demanded, for example, in cases such as the standard-letter mode and minute-letter mode in a facsimile machine. In order to meet such a demand, for example, Japanese Laid-Open Patent Publication No. 75780/1993 (Tokukaihei 5-75780) has disclosed a typical conventional technique. In this conventional technique, when a reading operation is carried out by using the resolution reduced to 1
of the maximum resolution, respective “n” number of adjacent CCDs (Charge Coupled Devices) serving as the reading members are connected in parallel with one another so as to addition-combine the outputs of the pixels.
Therefore, the problem with this conventional technique is that it is not applicable unless the desired resolution P is set at an integral multiple of the discrimination F.
Moreover, Japanese Laid-Open Patent Publication No. 145715/1993 (Tokukaihei 5-145715) is listed as another conventional technique. In this conventional technique, supposing that the normal transport speed is V, a transporting operation is carried out at a low speed in the range of V/2 to V, and a predetermined number of scanning lines are disabled depending on the transporting speed.
The subsequent problem with this conventional technique is the occurrence of image distortion due to the disabled scanning lines.
Similarly, Japanese Laid-Open Utility Model Publication No. 191261/1987 (Jitsukaishou 62-191261) has disclosed another conventional technique in which lines that have been read are counted and thinned out so as to fit the resolution on the playback side.
Therefore, the subsequent problem with this arrangement is also the occurrence of image distortion due to the thinning-out process on the above-mentioned lines.
In order to solve these problems, Japanese Laid-Open Patent Publication No.257382/1988 (Tokukaishou 63-257382) has disclosed a conventional technique which can change the resolution P while suppressing image distortion even if the resolution P is not set at an integer multiple of the discrimination F. In this conventional technique, after a reading operation has been carried out with the discrimination F of the transporting motor being set at a predetermined value, conversion to a desired resolution P is made by operation processing on a software basis.
Furthermore, another conventional technique proposes a method in which supposing that the reading speed of a reading member is Vp (msec/line), image data of the entire original document is converted by using a buffer memory so that the transporting speed Vf (msec/step) of a transporting motor can satisfy the following equation (1):
Vf×j=Vp×k
(1),
where j and k are arbitrary integers.
In addition, in the above-mentioned technique, another modified method is proposed in which in the case when, upon using the above-mentioned equation (1), the capacity of the buffer memory has an image-data amount less than one page of an original document, the reading operation of the reading member is temporarily stopped when the buffer memory becomes full.
However, the method using the operation processing on a software basis raises the following problems: an operation processing circuit is required, image distortion occurs due to the operation processing, and the time required for the operation processing gives adverse effects on the entire reading time.
Moreover, another problem with the method using the buffer memory is that a large memory, that is, a memory large enough to store the amount of image data corresponding to at least one page of original document, is required in order to carry out a smooth reading operation, thereby resulting in high costs.
Furthermore, in the method in which the reading operation is stopped when the buffer memory becomes full, upon stoppage of a reading operation, an accumulated offset takes place which is equivalent to the number of lines that have been read and which corresponds to the difference between the discrimination F of the transporting motor and the resolution P of the reading member. This results in an image distortion corresponding to one line, in the very worst case.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide an image-reading method and apparatus which can suppress image distortion by using only a small memory capacity.
In order to achieve the above-mentioned objective, the image-reading method of the present invention comprises the steps of: allowing a transporting member to transport relative to each other an original document having an image to be read and a reading member for scanning the image in a first direction so as to read the image in a second direction that is orthogonal to the first direction; and allowing the reading member to output the image as image data that has been read, wherein the transporting speed of the transporting member is increased in accordance with a desired suppression in the resolution in the image data.
In the above-mentioned method, the above-mentioned transporting member is a stepping motor for intermittently carrying out the transporting operation, and supposing that the discrimination corresponding to a minimum transporting interval of the transporting member is F (mm/step), a desired resolution is P (mm/line) and an acceptable error in the image data is ±&agr;, integers n and i that satisfy the following inequalities are found:
1−&agr;≦(
F×n
)/(
P×i
)≦1+&agr;,
wherein supposing that the reading speed of the reading member is Vp (msec/line), the transporting speed Vf (msec/step) of the transporting member is preferably set as follows:
Vf=Vp×i
.
With the above-mentioned method, the transporting speed of the transporting member is increased in accordance with a desired degree of suppression in the resolution so that the transporting speed of the original document is increased; thus, the image data can be read with a desired resolution.
Therefore, for example, in the case of facsimile machines for carrying out image transmissions, based upon a standard, etc. on communication, an original image is read by using a desired low resolution, and in the case of copying machines and printers, based upon a standard, etc., stipulated inside or outside the office, an original image is read by using a desired low resolution.
For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 5517331 (1996-05-01), Murai et al.
patent: 5668637 (1997-09-01), Yamaguchi
patent: 5684601 (1997-11-01), Endo et al.
patent: 5796928 (1998-08-01), Toyomura et al.
patent: 62-191261 (1987-12-01), None
patent: 63-257382A (1988-10-01), None
patent: 01305768A (1989-12-01), None
patent: 01307363A (1989-12-01), None
patent: 05
Lee Cheukfan
Sharp Kabushiki Kaisha
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