Facsimile and static presentation processing – Natural color facsimile – Scanning
Reexamination Certificate
2000-11-21
2004-08-31
Williams, Kimberly (Department: 2626)
Facsimile and static presentation processing
Natural color facsimile
Scanning
C358S514000, C348S311000, C348S220100, C348S312000
Reexamination Certificate
active
06785027
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a CCD (charge coupled device) solid-state imaging device for use in an image sensor. More particularly, the present invention relates to a method for driving a CCD solid-state imaging device capable of performing a high-speed pixel-decimated read operation (“monitoring mode”) for use in a high pixel density digital still camera.
2. Description of the Related Art
FIG. 1
is a plan view illustrating a structure of a secondary image sensor (CCD solid-state imaging device) which is representative of CCD-based imaging devices.
The CCD solid-state imaging device includes: a plurality of photodetector columns
11
a
each including a vertical array of photodetectors (photodiodes)
11
; a plurality of vertical CCDs
12
each for reading signal charges generated in the photodetectors
11
along one of the photodetector columns
11
a
; a horizontal CCD
13
for receiving signals transferred from the vertical CCDs
12
and horizontally transferring the received signals; a charge-voltage conversion section
14
for converting signal charges from the horizontal CCD
13
into voltage signals; and an amplifier
15
for amplifying voltage signals from the charge-voltage conversion section
14
. The CCD solid-state imaging device further includes vertical transfer electrodes
16
(in the illustrated example, four such electrodes are provided for implementing a 4-phase driving operation) for controlling the signal charge transfer in the vertical CCDs
12
, and horizontal transfer electrodes
17
(in the illustrated example, two such electrodes are provided for implementing a 2-phase driving operation) for controlling the signal charge transfer in the horizontal CCD
13
.
As a color filter arrangement for the photodetectors
11
in each photodetector column
11
a
, an RGB (R: red, G: green, B: blue) Bayer arrangement is employed in the illustrated example. Specifically, the photodetector columns
11
a
include an alternating pattern of two types of vertical photodetector arrays, with the first type of array including the photodetectors
11
of R, G, R, G, . . . , G, in this order from top to bottom, and the second type of array including the photodetectors
11
of G, B, G, B, . . . , B, in this order from top to bottom.
In the field of secondary image sensors, the pixel density (i.e., the number of pixels provided per unit area of the device) has been increasing. Particularly, current main stream digital still cameras include over two million pixels therein. A commonly-employed method for driving an imaging device such as a high pixel density digital still camera is a method which allows the user to switch between a still mode and a monitoring mode. The still mode is a mode in which data (signal charges) from all pixels (photodetectors) is read out and processed, and is selected when still images are processed, e.g., when printing out a picture that has been taken. The monitoring mode is a mode in which pixel data from all pixels, is thinned or decimated so as to use only a portion of the total pixel data, and is selected when moving images are processed, e.g., when adjusting the frame to select the object to be imaged, including the background or setting, while watching the monitor output.
The still mode operation and the monitoring mode operation will now be described.
FIG. 2
is an enlarged view of a portion of a CCD solid-state imaging device corresponding to two photodetector columns. In
FIG. 2
, like elements to those shown in
FIG. 1
are provided with like reference numerals. The CCD solid-state imaging device includes blocking pixels
28
at the bottom of each photodetector column, each of which is covered with a light blocking film to prevent light from entering the device therethrough.
In the illustrated example, the decimation ratio in the monitoring mode is {fraction (1/7)}, i.e., only data from one out of seven pixels (corresponding to seven photodetectors
11
) is used (such an operation is referred to herein as a “{fraction (1/7)} decimation operation”). The vertical transfer electrodes (vertical transfer gates)
16
include six different types (phases) of vertical transfer electrodes (“6-phase gates”), i.e., &PHgr;
V1A
, &PHgr;
V1B
, &PHgr;
V2
, &PHgr;
V3A
, &PHgr;
V3B
and &PHgr;
V4
, and
28
such gates are used as one unit. Alternatively, when a ¼ decimation operation is employed, the 6-phase vertical transfer electrodes (gates) are used, and 16 such gates are used as one unit. Herein, gates &PHgr;
V1A
, &PHgr;
V1B
, &PHgr;
V3A
and &PHgr;
V3B
are used for reading out signal charges from photodetectors, and the other gates &PHgr;
V2
and &PHgr;
V4
are used solely for signal transfer.
(Still Mode)
Referring to
FIGS. 3 and 4
, the still mode operation will now be described.
FIG. 3
illustrates a timing chart for the various vertical transfer electrodes
16
for the vertical CCDs
12
in the still mode.
FIG. 4
shows potential lines representing the respective potential states of the various vertical transfer electrodes
16
for the vertical CCDs
12
at each of the different points in a time period from t
31
to t
36
in FIG.
3
.
The different periods referred to in
FIG. 3
are defined as follows. The “one horizontal period” refers to a period of time starting from a read start time at which signal charges from one row of pixels, which have been received by the horizontal CCD
13
from the vertical CCDs
12
, are read out to output terminals, and ending at the following read start time at which signal charges from the next row of pixels, which have been received by the horizontal CCD
13
from the vertical CCDs
12
, are read out to the output terminals. The “horizontal blanking period” refers to a period of time starting from a point in time at which a clocking operation (for reading out signal charges from one row of pixels, which have been received by the horizontal CCD
13
from the vertical CCDs
12
, to the output terminals) is terminated, and ending at a point in time at which a clocking operation (for reading out signal charges from the next row of pixels, which have been received by the horizontal CCD
13
from the vertical CCDs
12
, to the output terminals) is initiated. The “one vertical transfer cycle” refers to a period of time in which signal charge, which have been received by the vertical CCDs
12
, is transferred vertically by one packet (one step) (from the potential state of time t
31
to the potential state of time t
32
in FIG.
4
). The term “packet” used herein refers to a potential well which is controlled by each vertical transfer electrode
16
for the vertical CCDs
12
. In other words, a “packet” is a receptacle for receiving a signal charge which is generated in a photodetector (corresponding to a low potential portion of the potential line shown next to “t
31
” in
FIG. 4
, for example). Each signal charge which has been read out from a photodetector is input to a corresponding packet, and is stored therein until it is transferred to the next packet.
In
FIG. 3
, “Ts” denotes one vertical transfer cycle in the still mode.
FIG. 4
shows potential lines representing the respective potential states of the various vertical transfer electrodes
16
of one of the vertical CCDs
12
along the line a-a′ in FIG.
2
. In order to read out signals from all of the R, G and B pixels, signals of two different color components are read out for each of two successive fields (A Field and B Field).
First, in the A Field and at time t
31
, R signal charges (┌
2
┘, ┌
4
┘, ┌
6
┘, . . . ) from the pixels (photodetectors
11
) of pixel numbers
2
,
4
,
6
, . . . (hereinafter, “pixels #
2
, #
4
, #
6
, . . .”), are readout from the photodetectors
11
to the corresponding packets of the vertical CCD
12
(
FIG. 4
) under the control of the electrodes &PHgr;
V1A
and &PHgr;
V1B
. Simultaneous with this read operation, G signal charges (
FIG. 2
) from the adjacent column of pixels next to the column of the pixels &nu
Conlin David G.
Daley, Jr. William J.
Edwards & Angell LLP
Sharp Kabushiki Kaisha
Worku Negussie
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