Television – Camera – system and detail – With single image scanning device supplying plural color...
Reexamination Certificate
1999-01-05
2003-07-29
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
With single image scanning device supplying plural color...
C257S234000, C257S230000, C257S229000, C257S231000, C358S483000
Reexamination Certificate
active
06600512
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color linear image sensor and driving method, and more particularly to a color linear image sensor and its driving method for reducing residual images without greatly increasing a line-to-line distance of the color linear image sensor.
2. Description of the Related Art
With popularization of personal computers and requests for higher performance of copying machines in recent years, demands for color linear image sensors for reading color images have increased.
Such a color linear image sensor is usually constructed in a manner that three CCD linear image sensors having charge transfer functions are arranged in parallel and color filters having different colors, e.g., R (red), G (green) and B (blue) filters, are placed on the light receiving section array of each CCD linear image sensor.
FIG. 11
is an entire constitutional view showing an example of such a color linear image sensor.
In
FIG. 11
reference numerals
1
a
,
1
b
and
1
c
denote light receiving sections having color filters of RGB (not shown) placed thereon; and
2
a
,
2
b
and
2
c
denote signal charge reading sections for reading signal charges stored after photoelectric conversion in the light receiving sections to signal charge transfer sections
3
a
,
3
b
and
3
c
provided in the vicinity. Signal charges Q
1
, Q
2
and Q
3
of the respective light receiving sections are read to the signal charge transfer sections (indicated by white arrows. Reading pulses are &phgr;TG
1
,
2
and
3
. Pulse lines are not shown).
In the case of the CCD linear image sensor, the signal charge transfer sections
3
a
,
3
b
and
3
c
usually include two-phase driven CCD shift registers, and pulse lines L
1
, L
2
, L
3
, L
4
and L
5
(clock pulse is &phgr;
1
or &phgr;
2
; connection from the pulse line to each signal charge transfer section is indicated by an arrow) for driving the two-phase driven CCD shift registers are arranged in the vicinity of the signal charge transfer sections.
Signal charges transferred by the signal charge transfer sections
3
a
,
3
b
and
3
c
are outputted to the outside by output circuits
4
a
,
4
b
and
4
c
composed of signal charge detection sections including a floating diffusion region for converting the signal charges into signal voltages and analog circuits such as source followers or inverters, and then color signals are obtained.
FIG. 15
is a timing chart showing a driving method of the conventional color linear image sensor shown in FIG.
11
. (Common among colors).
The signal charges of the light receiving sections
1
a
,
1
b
and
1
c
are stored while clock pulses &phgr;TG
1
,
2
and
3
applied to the signal charge reading sections
2
a
,
2
b
and
2
c
are at LOW levels. In the period T when the clock pulses are at HIGH levels, the signal charges are read to the specified signal charge transfer sections
3
a
,
3
b
and
3
c.
Subsequently, in these signal charge transfer sections, the signal charges are transferred by two-phase clock pulses &phgr;
1
and &phgr;
2
(phases reverse to each other), and then outputted from the output circuits
4
a
,
4
b
and
4
c.
If the foregoing color linear image sensor is used for a scanner or a copying machine, scanning is performed by the three CCD linear image sensors having the color filters vertically to the arraying direction thereof. Accordingly, for obtaining color information (e.g., RGB) regarding an image of a specified place on an object, signal processing must be performed after externally storing bits of color information of first and second lines in the period from the end of scanning the specified place by the first line (e.g., R) to the end of scanning by a third line (e.g., B) and then obtaining three bits of color information. Consequently, an external memory having a very large capacity must be used.
For example, in the case of a color linear image sensor of a class of 5300 pixels×3 array which is used for a color copying machine or a high resolution color scanner, if gradation is set to 10 bits, a necessary capacity C of an external memory is obtained by the following expression:
C
=5300×10×3×(M+1) bits (1)
Herein, M denotes, in the form of a scanning number of times, a line-to-line distance between two light receiving section array adjacent to each other among the light receiving section array. For example, if a size of one pixel of each of the R, G and B light receiving sections is 8 &mgr;m×8 &mgr;m and line-to-line distances between the R and G light receiving section array and between the G and B light receiving section array are both 64 &mgr;m, M is obtained by the following expression:
M
=64 &mgr;m/8 &mgr;m (2)
Accordingly, a capacity C of the external memory is 1431000 bits.
As apparent from the expression (1), for reducing a capacity of the external memory, it is necessary to reduce a scanning number of times in the period from the end of scanning by the first line (e.g., R) to the end of scanning by the third line (e.g., B) by shortening a distance among the three light receiving section array.
FIG. 12
is an expanded view of a region surrounded with a broken line X
1
of FIG.
11
. In the drawing, the same reference numerals as those used in
FIG. 11
, e.g.,
1
a
and
1
b,
denote the same elements. A reference numeral
5
denotes an aluminum wiring line to which a two-phase clock pulse &phgr;
1
or &phgr;
2
is applied;
6
a contact for connecting the aluminum wiring line
5
with one selected from two kinds of polycrystalline silicon electrodes
11
a
and
11
b
of the CCD shift register which constitutes the signal charge transfer section
3
a;
7
also a contact for connecting together the two kinds of polycrystalline silicon electrodes
11
a
and
11
b
of the CCD shift register;
8
an aluminum wiring line to which clock pulses for driving the signal charge reading sections
2
a
and
2
b
are applied;
9
a contact for connecting the aluminum wiring line
8
with polycrystalline silicon electrodes
11
b
for constituting the signal charge reading sections
2
a
and
2
b;
and
12
an element separation region for separating each pixel of the light receiving section and the signal charge transfer section.
A size of one pixel of the light receiving section is determined by a portion held between the aluminum wiring lines
5
and
8
.
Light shielding of the signal charge transfer section
3
a
is usually performed by another kind of aluminum wiring line, but its explanation will be omitted.
As apparent from
FIG. 12
, main factors for deciding a line-to-line distance (distance from the center of the light receiving section
1
a
to the center of the light receiving section
1
b
) are as follows:
(1) a size of one pixel of the light receiving section;
(2) a size of the signal charge reading section;
(3) a size of the signal charge transfer section; and
(4) a size of the element separation region between the signal charge transfer section and its adjoining light receiving section array (including a size of the pulse line). In the example of
FIG. 12
, a line-to-line distance is totally 64 &mgr;m (M=8), which is obtained by adding up the following sizes: a size of one pixel of the light receiving section is 8 &mgr;m; a size of the signal charge reading section is 10 &mgr;m; a size of the signal charge transfer section is 18 &mgr;m; a size of the element separation region between the signal charge transfer section and its adjoining light receiving section array is 25 &mgr;m; and a size of a connected part between (2) and (3) is 3 &mgr;m.
Regarding the foregoing factors (1) to (4), for (1), its size cannot be changed, because it is a fixed pixel size. For (2), it is very difficult to set its size to be lower than 10 &mgr;m, because a region must be provided for connecting a clock wiring line for driving the signal charge reading section with a polycrystalline silicon electrode for constituting the signal charge reading section. For (3), e
Garber Wendy R.
Hannett James M
NEC Corporation
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