Scanner frame with coplanar scan window

Details Scanner frame with coplanar scan window Scanner frame with coplanar scan window

2000-09-25

2004-02-24

Lee, Cheukfan N (Department: 2622)

Facsimile and static presentation processing

Facsimile

Picture signal generator

C358S474000, C358S471000, C399S379000, C355S075000

Reexamination Certificate

active

06697176

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to scanners, particularly to the frame of a scanner or copying machine.
2. Brief Review of the Related Art
In a scanner, it is important to maintain a fixed light path from the scanned document to the light sensor. An approach to maintain the fixed light path is to use the Dual Light Module. In a conventional scanner, the scanning window and the light sensor are mounted on different component parts of the scanner frame. Between the scan window and the light sensor are many optical components. The interfaces between these components may have mechanical tolerances relative to one another. As a result, the light path may vary from the design value. Then, error may be introduced in the reproduced image.
FIG. 1
shows a prior art mounting structure of a dual optical module scanner as disclosed in Taiwan Patent Application No. 084210836. In this figure, a scanner window
12
is mounted on the frame
10
of the scanner through two L-shaped brackets
11
. The sensor
18
is mounted on the bottom surface of the frame
10
. The L-shaped brackets
11
have two flanges
114
to scanning glass
12
. The bottom surfaces of the brackets
11
rest on two flanges
14
of the frame
10
. A guiding rail
16
is mounted on the frame for one or two optical modules (not shown) to slide back and forth. The guiding rail
16
is hanging on the frame
10
through two holes
15
along the side wall
17
as shown in the 3-dimensional drawing FIG.
2
. The L-shaped brackets
11
are pinned to the frame by pins
13
as shown in FIG.
1
through holes
103
on the flanges
14
as shown in FIG.
2
.
The structure in
FIGS. 1 and 2
have tolerance problems. The optical system has three optical sub-units. All these sub-units may have relative interface offset with respect to each other. If there is any offset due to tolerance in their dimensions, the length of the light path will be affected.
To avoid the tolerance problem, the light sensor
18
and the guiding rail
16
for the scanning carriage, the material of the frame
10
must be of low temperature coefficient metal. At present, the frame
10
is essentially made of sheet metal base, covered with the bracket
11
, which improves the appearance and supports the heavy scanning glass window. The bracket also serves as an interface between the metal base and the glass window to avoid direct contact of the hard surface of the window and hard surface of the metal frame. As shown in
FIG. 1
, the L-shaped bracket supports the window at the interface (flange)
114
. Such a structure suffers from the tolerance problem of the cushioning bracket.
SUMMARY
An object of this invention is to avoid any light path error between the scan window and the light sensor. Another object of this invention is to planarize the surface of the scan window and top surface of the frame.
These object are achieved by planarizing the top surface of the scanner frame, where the light sensor is mounted, with one of the surfaces of the scan window. With the two coplanar surfaces, there can be no relative motion between the glass window and the frame and the light path between them cannot deviate. The light path between the scan window and the light sensor on the frame of the scanner does not vary regardless of any interface tolerance of the optical components of the optical modules.


REFERENCES:
patent: 5734483 (1998-03-01), Itoh
patent: 6144465 (2000-11-01), Hayashi
patent: 6285441 (2001-09-01), Takahara
patent: 6473206 (2002-10-01), Fujimoto et al.

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