Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
1999-01-21
2003-05-20
Grant, II, Jerome (Department: 2624)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S497000
Reexamination Certificate
active
06567189
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image reading apparatus and an image reading method.
2. Related Background Art
An image scanner using a CCD linear image sensor (hereafter referred to as CCD) has been known so far as an image reading apparatus.
FIGS. 32A and 32B
briefly show the structure of a flat-bed-type scanner, in which
FIG. 32A
is a top view and
FIG. 32B
is a side view. Reference D denotes an original to be read put on an original table glass
100
. The original is irradiated with a light source
101
and the reflected light is turned back by mirrors
102
,
103
, and
104
to focus the original on a CCD
106
by a lens
105
. The original D is entirely read by moving a reading unit
107
with the light source
101
, mirrors
102
,
103
, and
104
, lens
105
, and CCD
106
firmly mounted on it from the left to right in
FIG. 32A
in parallel with the original table glass
100
and thereby scanning the original D to obtain image signals for one page from the CCD
106
. In this case, as shown in
FIG. 32A
, the direction from the top toward the bottom denotes a main scanning direction and the direction from right to left denotes a sub-scanning direction.
FIGS. 33A and 33B
briefly show the structure of a CCD. In
FIG. 33A
, references
201
-
a, b, c, d
. . . denote a photoelectric-conversion pixel string of
202
-
a, b, c, d
. . . denote carrying gates for carrying electric charges photoelectric-converted by the photoelectric-conversion pixel string of
201
-
a, b, c, d
, . . . ,
203
denotes a transfer section for successively transferring the carried electric charges, and
204
denotes an output circuit for linearly reading the transferred electric charges as output signals.
FIG. 33B
shows the photoelectric-conversion pixel portions
201
-
a
and
201
-
b
in
FIG. 33A
by enlarging them.
As described above, the original D is linearly illuminated in the main-scanning direction and an optical image focused on the photoelectric-conversion pixel string of
201
-
a, b, c, d
, . . . moves in the sub-scanning direction shown in
FIG. 33B
at a predetermined speed through an optical lens or the like. Electric charges photoelectric-converted by the photoelectric-conversion pixel string of
201
-
a, b, c, d
, . . . and accumulated are carried to a transfer section
20
in a predetermined period when the focused image moves from the position A to position B shown in FIG.
33
B and then, the focused image is read from the output circuit
204
in a predetermined period when the image moves from the position B to the position C. Hereafter, the above operations are repeated and thereby, a cyclic line sequential signal, that is, a main-scanning line signal is obtained.
Generally, as shown in
FIG. 33B
, a distance AB (and a distance BC) is set equally to a photoelectric-pixel pitch P in the main-scanning direction so that the same resolution can be obtained in main scanning direction and sub-scanning direction.
In the case of the above conventional example, however, to raise the resolution up to two times, it is necessary to decrease the photoelectric-conversion pixel pitch P to ½. Therefore, the pixel size of the photoelectric-conversion pixel string of
201
-
a, b, c, d
, . . . must be decreased to ½ in main scanning direction and sub-scanning direction and the period for the above reading must be also reduced to ½. Therefore, the area of photoelectric conversion pixels is decreased to ¼ and moreover, the time for photoelectric conversion is decreased to ½. Thus, problems occur that the sensitivity is lowered to ⅛ and the image quality is greatly deteriorated.
Moreover, because the transfer rate is doubled, the electric-charge transfer performance is deteriorated and a problem occurs that the heat produced in the transfer section and the power consumption are increased. It is needless to say that these factors deteriorate the image quality of an image reading apparatus. Moreover, because the pixel size decreases, it is necessary to improve the resolution of a lens and thus, the lens cost is increased.
Among the above problems, for the problem of insufficient sensitivity, a method of increasing the size of a photoelectric-conversion pixel and decreasing the focusing magnification of a lens is considered. For example, by increasing the size of photoelectric-conversion pixel up to substantial 2.8 times in main scanning direction and sub-scanning direction, the sensitivity becomes equal to the conventional sensitivity. However, because the size of the transfer section also increases, deterioration of the transfer performance is further progressed and the produced heat is further increased and thus, the image quality is further deteriorated.
Moreover, the chip size in the main-scanning direction is increased up to substantial 2.8 times and thereby, a problem occurs that costs of a CCD and a lens are greatly increased.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a an image reading apparatus capable of realizing a high image quality equal to two-fold high resolution without changing CCDs or lenses or deteriorating characteristics.
To solve the above problems, according to one aspect of the present invention, there is provided an image reading apparatus comprising optical means for focusing the reflected optical image of an original, an image sensor constituted by linearly arranging pluralities of photoelectric-conversion pixels to accumulate linear reflected optical images focused by the optical means in the photoelectric-conversion pixels as signal electric charges and successively output the linear reflected optical images as image signals every certain period, scanning means for scanning the original in a sub-scanning direction vertical to a main scanning direction serving as the direction of the linear reflected optical images, and pixel-shifting means for shifting the relative positions between the position of an optical image focused on the image sensor through the optical means and the photoelectric-conversion pixels on the unit basis of substantial 1/N (N is an integer) the pixel pitch of the image sensor in the main scanning direction.
Moreover, according to an another aspect of the present invention, there is disclosed an image reading method comprising steps of picking up reflected optical images of an original focused by optical means with a linear image sensor constituted by linearly arranging a plurality of photoelectric-conversion pixels and thereby, successively outputting image signals corresponding to the linear reflected optical images every certain period, shifting the relative positions between the position of an optical image focused on the linear image sensor through the optical means on one hand and the photoelectric-conversion pixels in a main scanning direction on the unit basis of substantial 1/N (N is an integer) the pixel pitch of the linear image sensor every plurality of repetitions of sub-scanning when the original is scanned in a sub-scanning direction vertical to a main scanning direction of the linear reflected optical images, and thereby picking up the original.
Furthermore, according to an another aspect of the present invention, there is disclosed a storage medium storing an image-reading program comprising steps of picking up reflected optical images of an original focused by optical means with a linear image sensor constituted by linearly arranging plurality of photoelectric-conversion pixels to successively output image signals corresponding to the linear reflected optical images every certain period, scanning the original a plurality of times in a sub-scanning direction vertical to a main scanning direction of the linear reflected optical images, shifting the relative positions between the position of an optical image focused on the linear image sensor through the optical means and the photoelectric-conversion pixels in a main scanning direction on the unit basis of substantial 1/N (N is an integer) the pix
Inoue Shoichi
Takayama Tsutomu
Takeuchi Yukitoshi
Yoshida Yukio
Grant II Jerome
Worku Negussie
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