Television – Camera – system and detail – With single image scanning device supplying plural color...
Reexamination Certificate
1999-03-11
2004-06-01
Christensen, Andrew (Department: 2614)
Television
Camera, system and detail
With single image scanning device supplying plural color...
C348S230100, C348S273000, C358S483000
Reexamination Certificate
active
06744466
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of driving a solid-state image sensor, and more particularly to a method of driving a solid-state image sensor which is capable of reading out signal electric charges from photodiodes into a vertical charge coupled device for every predetermined number of vertical pixel lines.
2. Description of the Related Art
These days, there has been developed a camera to be used for a personal computer in order to input images to the computer. An image sensor incorporated in a conventional camera employing a television system such as NTSC and PAL has been conventionally designed to have an interlace system in which a frame is displayed with two fields. For instance, such a image sensor has been suggested in Japanese Unexamined Patent Publications Nos. 61-21689, 2-196567, 4-262679, 7-184125, and 9-55952.
However, an image sensor with an interlace system is accompanied with low resolution of images. Hence, an image sensor incorporated in a camera is recently designed to have a non-interlace system in order to enhance resolution of images. In a non-interlace system, signals running through horizontal scanning lines constituting a frame are output in turn. A non-interlace system has an advantage that images can be displayed with ease on a screen such as a personal computer. Hence, an image sensor associated with a non-interlace system, that is, a progressive scan type image sensor has been in demand, and thus, has been researched.
FIG. 1
is a plan view of an interline type charge coupled device (CCD) image sensor associated with a progressive scan system. The illustrated CCD image sensor is comprised of an image sensing region
1
, a horizontal CCD
2
, an output section or a charge detector
3
, a plurality of photodiodes
4
arranged in the image sensing region
1
in a two-dimensional matrix, and a plurality of vertical CCDs
5
each located adjacent to each row of photodiodes.
Each of the photodiodes
4
transfers a light into a signal electric charge, and accumulates the thus transferred electric charge therein. Each of the vertical CCDs
5
vertically transfers signal electric charges having been transferred from the photodiodes
4
. An electric charge reader
6
positioned between each of the photodiodes
4
and each of the vertical CCDs
5
reads a signal electric charge out of each of the photodiodes
4
into each of the vertical CCDs
5
. The image sensing region
1
except the photodiodes
4
, the vertical CCDs
5
, and the electric charge readers
6
defines an insulating region for insulating a device from another device.
In operation, a light is transferred into an electric charge for a certain period of time in each of the photodiodes
4
, and the thus generated electric charge is accumulated in each of the photodiodes
4
. The electric charges accumulated in the photodiodes
4
are read out into the vertical CCDs
5
through the electric charge readers
6
by applying a certain voltage to the electric charge readers
6
. The electric charges having been read out into the vertical CCDs
5
are transferred towards the horizontal CCD
2
by a horizontal line. The electric charges having been transferred to the horizontal CCD
2
are horizontally transferred in the horizontal CCD
2
, and then, detected at the output section
3
as an output voltage.
FIG. 2
is a plan view illustrating a positional relation between the photodiodes
4
and vertical transfer electrodes
8
constituting the vertical CCD
5
in a progressive scan type image sensor. The vertical CCD
5
includes four vertical transfer electrodes
8
a
,
8
b
,
8
c
, and
8
d
for each of the photodiodes
4
. At least one of the vertical transfer electrodes
8
a
,
8
b
,
8
c
, and
8
d
doubles as a read-out electrode for reading out a signal electric charge from the photodiode
4
to the vertical CCD
5
. For instance, the vertical transfer electrode
8
c
doubles as such a read-out electrode.
When each of the vertical CCDs
5
is driven by four-phase pulses &phgr;V
1
to &phgr;V
4
, vertical drive pulses &phgr;V
1
to &phgr;V
4
are applied to the vertical transfer electrodes
8
a
to
8
d
, respectively, in a four-electrode cycle.
FIGS. 3A
to
3
C illustrate how an electric charge is transferred in progressive scanning operation. For simplification,
FIGS. 3A
to
3
C illustrate only one vertical CCD
5
, and a partial horizontal CCD
2
located below the vertical CCD
5
. In
FIGS. 3A
to
3
C, a solid circle (&Circlesolid;) indicates a packet containing an electric charge therein, and a hollow circle (∘) indicates a packet containing no electric charge therein.
With reference to
FIG. 3A
, the photodiodes PD
1
to PD
6
are exposed to a light for a certain period of time to thereby transfer a light into signal electric charges, and accumulate the thus generated signal electric charges therein. When a read-out voltage is applied to all the read-out electrodes
6
, the signal electric charges accumulated in the photodiodes PD
1
to PD
6
are read out into the vertical CCD
5
.
Then, as illustrated in
FIG. 3B
, the signal electric charges having been read out into the vertical CCD
5
are transferred towards the horizontal CCD
2
by a horizontal line.
Then, as illustrated in
FIG. 3C
, the signal electric charge having been transferred in the vertical CCD
5
by a vertical line reaches the horizontal CCD
2
, and is transferred through the horizontal CCD
2
by a line. Finally, the signal electric charge is output through the output section
3
(not illustrated in
FIGS. 3A
to
3
C).
FIG. 4
illustrates waveforms of the vertical drive pulses &phgr;V
1
to &phgr;V
4
and how the electric charges are transferred in progressive scanning operation.
The waveforms of the vertical drive pulses are illustrated over one vertical blanking period and subsequent two horizontal blanking periods. The vertical drive pulses are four-phase pulses. Read-out pulses &phgr;TGA, &phgr;TGB and &phgr;TGC read out the signal electric charges from the photodiodes
4
into the vertical CCDs
5
. In
FIG. 4
, the read-out pulses &phgr;TGA, &phgr;TGB, and &phgr;TGC are shown as independent pulses, however, it should be noted that the read-out pulses &phgr;TGA, &phgr;TGB, and &phgr;TGC are applied to the vertical transfer electrode
8
c
doubling as a read-out electrode in the form that the read-out pulses &phgr;TGA, &phgr;TGB, and &phgr;TGC are overlapped onto the vertical drive pulses &phgr;V
3
A, &phgr;V
3
B, and &phgr;V
3
C, respectively.
In a lower half of
FIG. 4
, showing how the electric charges are transferred, the photodiodes
4
and the vertical transfer electrodes
8
are illustrated. Lowermost rows indicate horizontal transfer electrodes
9
constituting the horizontal CCD
2
. A horizontal drive pulse &phgr;H
1
is applied to the horizontal transfer electrodes
9
.
In a lower half of
FIG. 4
, a hollow rectangle indicates a vertical transfer electrode containing no signal electrode charge, and a hatched rectangle indicates a vertical transfer electrode containing a signal electric charge having been read out from the photodiode
4
. Transfer of electric charges with the lapse of time can be understood by virtue of the signal waveforms illustrated in an upper half of
FIG. 4
, and it is also understood that a signal electric charge is located adjacent to which vertical CCD at a certain timing, by virtue of the photodiodes
4
and the vertical transfer electrodes
8
illustrated at the left. Thus, it is understood how electric charges are transferred.
With reference to
FIG. 4
, when the vertical drive pulses &phgr;V
1
to &phgr;V
4
are in a middle level, a channel located below the associated vertical transfer electrode
8
is ready to accumulate electric charges therein. When the vertical drive pulses &phgr;V
1
to &phgr;V
4
are in a low level, a channel located below the associated vertical transfer electrode
8
is not ready to accumulate electric charges therein.
When the read-out pulses &phgr;TGA, &phgr;TGB, and &phgr;TGC are in
Christensen Andrew
NEC Electronics Corporation
Sughrue & Mion, PLLC
Wu Dorothy
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