Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
2002-02-19
2004-03-16
Coles, Edward (Department: 2622)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S496000, C358S497000, C358S498000, C358S412000, C358S413000
Reexamination Certificate
active
06707582
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a scanning device, and more specifically, to a scanning device capable of calibrating the step angle errors of a motor.
2. Description of the Prior Art
Desktop scanners are very popular computer peripheral devices. They are used to scan documents to generate corresponding image data. In addition, scanners can provide extra functionality. For example, a scanner may be used to send image data as fax image data to other facsimile devices through a phone line, to other people in an e-mail format through a network, or to a printer for copying. As the scanning technology progresses, the quality requirements for scanners turns more and more rigid as well. It is therefore an important issue to prevent scanning errors caused by errors of either the hardware or the software of the scanner.
Please refer to
FIG. 1
of a schematic diagram of a scanner
10
according to the prior art. As shown in
FIG. 1
, the scanner
10
includes a housing
12
, a transparent platform
14
installed on the housing
12
for a document
20
to be placed on, and a scanning module
16
moveably installed inside the housing
12
for scanning the document
20
and generating an corresponding image of the document
20
. The scanner also has a step motor
18
, installed inside the housing
12
and physically and electrically connected to the scanning module
16
, for driving the scanning module
16
step-by-step to scan the document
20
.
Theoretically, ideal step lengths of the scanning module
16
generated by one-step-forwards motions of the step motor
18
are all the same. Each ideal step length equals to a quotient of a distance traveled by the scanning module
16
driven by one complete rotation of the step motor
18
, divided by the number of the steps traveled by the step motor
18
during the complete rotation. Unfortunately, a step angle error of the step motor
18
caused by manufacturing errors frequently leads to different step lengths of the scanning module
16
generated by one-step-forwards motions of the step motor
18
.
Please refer to
FIG. 2
a
and
FIG. 2
b
, which respectively represent a document to be scanned and an image generated after the scanner
10
scans the document according to the prior art. As shown in
FIG. 2
a
, the document to be scanned includes three parallel lines
21
, a distance
22
between the first and second lines
21
being equal to a distance
24
between the second and the third lines
21
. Due to the step angle error of the step motor
18
, the image generated after scanning the document is slightly different from an actual image of the document. As shown in
FIG. 2
b
, a distance
26
between the first and second lines
21
on the generated image, and a distance
28
between the second and the third lines
21
on the generated image are not equal to the distance
22
between the first and second lines
21
on the actual image of the document and the distance
24
between the second and the third lines
21
on the actual image of the document. In other words, the step angle error of the step motor
18
leads to a scanning error of the scanner
10
. In addition to the step angle errors in the step motor
18
, slight angle errors of spokes also frequently occur in servomotors due to manufacturing errors and lead to errors of images generated by scanning. The higher the resolution of the scanner is, the more conspicuous and intolerable the error of the generated image caused by the angle error is.
SUMMARY OF INVENTION
It is therefore a primary objective of the claimed invention to provide a scanning device for calibrating step angle errors of a motor.
According to the claimed invention, a scanner comprises a housing, a transparent platform, a scanning module, a motor, and a calibration paper. The transparent platform is installed on the housing for a document to be placed on. The scanning module is moveably installed inside the housing for scanning the document. The motor is installed inside the housing for driving the scanning module. The calibration paper is installed at a front end of the housing and has a graph for calibrating step angle errors of the motor.
It is an advantage of the claimed invention that the scanner includes the calibration paper. The scanner scans the graph on the calibration paper before scanning the document to obtain the ideal step length of the scanning module generated by the step motor. In addition, the comparison table disclosed in the claimed invention stores the ideal step length and the actual step length of both the scanning module and the step motor. Thus the scanning module calibrates the image generated by scanning the document according to the distance between the graph and the front end of the transparent platform
54
, the actual step lengths and the ideal step lengths of the scanning module
56
. Consequently, the accuracy of the scanning is significantly improved.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the multiple figures and drawings.
REFERENCES:
patent: 6069464 (2000-05-01), Wu
patent: 57190456 (1981-05-01), None
Avision Inc.
Coles Edward
Safaipour Houshang
Winston Hsu
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