Scanner of variable scanning speeds

Details Scanner of variable scanning speeds Scanner of variable scanning speeds

2000-11-30

2004-06-01

Coles, Edward (Department: 2622)

Facsimile and static presentation processing

Facsimile

Picture signal generator

C358S486000, C358S412000

Reexamination Certificate

active

06744538

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a scanner, and more particularly, to an optical scanner of variable scanning speeds.
BACKGROUND OF THE INVENTION
A scanner is a popular computer peripheral device. The scanner can transfer photographs, texts and pictures on a scanned object to image files. There are two different kinds of resolutions for a scanner: the horizontal resolution and the vertical resolution. The horizontal resolution, which is also called the optical resolution, represents the dot number being captured by a scanning module of the scanner on a scanned object per inch. The vertical resolution, which is also called the mechanical resolution, is determined by the relative movement speed between the scanning module and the scanned object. A conventional scanner uses a stepping motor to drive the scanning module to move relatively to the scanned object or to drive the scanned object to move relatively to the scanning module, so the vertical resolution is determined by the rotation speed of the stepping motor. As a result, the rotation speed of the stepping motor determines the vertical resolution. However, a large variation of the rotation speed may deteriorate the stability of the stepping motor and thus degrade the scanning quality. Therefore the rotation speed of the stepping motor can only be varied in a limited range and consequently the vertical resolution can only be varied within a limited range. A conventional flat bed optical scanner is taken as an example and described in the following.
Please refer to
FIG. 1
, which is a schematic diagram of a conventional flat bed scanner
10
. The scanner
10
includes therein a stepping motor
12
, an input gear
14
, an output gear
16
, a belt
18
, a scanning module
20
and an axle
22
. The scanning module
20
is connected and driven by the belt
18
to slide along the axle
22
during the scanning process. The flat bed scanner
10
uses the stepping motor
12
to drive the output gear
16
via the input gear
14
. The belt
18
is driven by the output gear
16
and then forces the scanning module
20
to move relatively to the scanned object along the axle
22
. To increase the vertical scanning resolution, the rotation speed of the stepping motor
12
is decreased to slow down the relative movement between the scanning module
20
and the scanned object. On the contrary, increasing the rotation speed of the stepping motor
12
will speed up the relative movement between the scanning module
20
and the scanned object, and thus decreases the vertical scanning resolution. Because a large variation of the rotation speed may deteriorate the stability of the stepping motor
12
and thus degrade the scanning quality, the rotation speed of the stepping motor
12
can only be changed in a limited range. Therefore, the vertical resolution of the conventional scanner
10
is limited within a small range.
SUMMARY OF THE INVENTION
Therefore, the present invention provides an optical scanner of variable scanning speeds. The scanner includes a scanning module, a power transmission device, a gear module and a driving device. The scanning module is connected to the power transmission device. The gear module includes at least a first gear and a second gear, and the gear module is capable of switching between a first position and a second position. The driving device drives the gear module. The driving device allows the scanning module and the scanned object to move relatively at a first speed through the first gear when the gear module switches to the first position. The driving device allows the scanning module and the scanned object to move relatively at a second speed by the second gear when the gear module switches to the second position.


REFERENCES:
patent: 5954326 (1999-09-01), Gaarder et al.
patent: 2213356 (1995-11-01), None

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