Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
1999-10-21
2003-07-15
Grant, II, Jerome (Department: 2624)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S473000
Reexamination Certificate
active
06594037
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an image reading apparatus such as copying apparatus, image scanner, or the like using a contact type image sensor.
2. Related Background Art
FIG. 4A
shows an image scanner as an example of an image reading apparatus.
FIG. 4B
is a cross sectional view of a main portion of the image scanner. In
FIG. 4A
or
4
B, reference numeral
1
denotes an original plate glass;
2
a pressing plate to press an original
20
put on the original plate glass
1
;
3
a contact type image sensor;
4
a frame of the image sensor
3
;
5
a lens array;
6
a sensor;
7
a light guide;
8
a sensor holder;
9
a guide shaft;
10
a wire winding barrel (drum);
11
a wire for driving the image sensor; and
12
a driving motor.
Generally, an LED is used as a light source (not shown). The LED is arranged in an edge portion of the light guide
7
. The light beam emitted from the LED is converted into a linear light beam by the light guide
7
to irradiate the surface of the original. An image of the original
20
on the original plate glass
1
is formed onto the surface of the sensor
6
by the lens array
5
and photoelectrically converted by the sensor
6
. By forming the above construction as one unit, the contact type image sensor
3
is formed.
The contact type image sensor
3
is held by the sensor holder
8
which is a holding member and linearly moves in the direction (scanning direction shown by an arrow) perpendicular to the longitudinal direction of the contact type image sensor
3
along the guide shaft
9
while keeping a distance from the original plate glass
1
, thereby scanning the plane-shaped original.
Generally, the frame
4
of the contact type image sensor
3
is made of a resin. The contact type image sensor
3
is formed by fixing various component parts such as light guide
7
, lens array
5
, sensor board, and the like onto the frame
4
. The frame
4
of the contact type image sensor
3
generally has a rod shape in terms of a construction of each of the above parts. Therefore, when it is formed, a tendency of “warp” is likely to occur.
FIG. 5
shows an enlarged diagram of the main portion of such a state.
When the frame
4
has such a warp tendency, a board of the lens array
5
and sensor
6
fixed onto the frame
4
is also deformed in a frame shape. The original plate glass
1
is usually formed by cutting a plate glass called a “float glass” into a desired shape and used. The glass ordinarily has precision that is extremely close to that of a flat surface, so that a radius of curvature of the glass is equal to 100 to 500 mR.
In this case, as shown in
FIG. 5
, a distance between the original plate glass
1
and contact type image sensor
3
differs depending on the location in the longitudinal direction of the contact type image sensor
3
. Therefore, although an object surface focal position of the lens array
5
and the upper surface of the original plate glass
1
coincide in the edge portion of the contact type image sensor
3
, the object surface focal position of the lens array
5
is further deviated to the upper side than the upper surface of the original plate glass
1
in the center portion of the contact type image sensor
3
due to an influence by a warp of the sensor.
It is now assumed that a distance from the top edge surface of the lens array
5
to the object surface side focal position is set to d, a distance from the top edge surface of the lens array
5
to the upper surface of the original plate glass
1
is set to d′, and a depth of field of the lens is set to D. In this case, the following relational expression has to be satisfied to avoid the occurrence of an out-of-focus of the original image to be read.
d−D/
2≦
d′≦d+D/
2
If distance d′ from the top edge surface of the lens array
5
to the upper surface of the original plate glass
1
lies within the range obtained by the above expression, since the upper surface of the original plate glass
1
is located in the depth of focus of the lens array
5
, an out-of-focus does not occur. However, if a value of d′ exceeds the range obtained by the above expression and is shorter than (d−D/2) or longer than (d+D/2), there is a problem such that an out-of-focus occurs. Particularly, in recent years, a conjugate length of the lens array which is used in the contact type image sensor becomes short in accordance with a demand for miniaturization of the apparatus, so that the depth of field is shallow. Consequently, the problem of the out-of-focus is likely to occur.
Generally, a size of gap between the original plate glass
1
and contact type image sensor
3
is very small and there is also a problem such that if a warp amount of the contact type image sensor
3
is large, the lens array
5
or frame
4
is come into contact with the back surface of the original plate glass
1
and an abnormal sound is generated.
FIG. 6
is a schematic diagram of a frame die to form the frame
4
of the contact type image sensor. The direction of the warp of the sensor frame
4
can be controlled by a frame shape or a gate position or by providing a temperature difference between a cabinet side
16
of the frame die to form the frame and a core side
15
, or the like. For example, if a temperature of the die on the cabinet side is set to be higher than that on the core side, a contraction on the core side of a low frame temperature is large, so that the frame can be controlled to a shape that is warped upward. It is, however, substantially difficult to suppress a warp amount to zero.
As means for correcting the warp of the sensor frame
4
, there is a method of fixing the contact type image sensor
3
to a member such as an iron plate or the like and keeping the flatness by using the flatness and rigidity of the iron plate. There is, however, a problem such that an excessive force is applied to the contact type image sensor
3
, longevity and optical characteristics are influenced, and the like. Since the member such as an iron plate is used, there is also a problem of costs such that the number of parts increases.
SUMMARY OF THE INVENTION
In an image reading apparatus using a contact type image sensor, it is an object of the invention to prevent a deterioration of a picture quality such as out-of-focus or the like due to a warp of the contact type image sensor and a contact between the contact type image sensor and an original plate glass.
According to one aspect of the invention, there is provided an image reading apparatus comprising: an original plate glass to put an original; a contact type image sensor to read image information of the original; and moving means for moving the contact type image sensor relatively to the original, wherein a warp shape of the original plate glass in the longitudinal direction of the contact type image sensor and a warp shape of the contact type image sensor are almost the same.
By constructing as mentioned above, the deterioration in picture quality such as out-of-focus or the like and the contact between the contact type image sensor and the original plate glass can be prevented.
REFERENCES:
patent: 5764382 (1998-06-01), Shiraishi
patent: 6147339 (2000-11-01), Matsumoto
patent: 6389183 (2002-05-01), Han
patent: 02036665 (1998-07-01), None
Canon Kabushiki Kaisha
Grant II Jerome
Morgan & Finnegan , LLP
Worku Negussie
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