Facsimile and static presentation processing – Natural color facsimile – Scanning
Reexamination Certificate
1998-03-31
2002-11-05
Nguyen, Madeleine (Department: 2622)
Facsimile and static presentation processing
Natural color facsimile
Scanning
C038S098000, C348S314000
Reexamination Certificate
active
06476941
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a solid-state image sensing device and an operation method thereof and, more particularly, to a solid-state image sensing device and an operation method for scanning a predetermined area of the solid-state image sensing device.
With the progress of manufacturing technique of a charge coupled device (CCD), the density of pixels in the CCD increases. Further, a number of image sensing apparatuses, such as a video camera and a digital still camera, which adopt scanning method for scanning a predetermined area out of a readable area of the CCD (partial scanning) to realize anti-vibration mechanism, electronic zooming mechanism, display of a reduced image on a liquid crystal display as a finder, and so on, have been commercialized. Furthermore, partial scanning is also applied to automatic focusing and automatic iris diaphragm control. Accordingly, various partial scanning method are used in dependence upon utilization purposes. Some digital still cameras have a function of partial scanning for taking sequence photographs in low resolution so as to increase the number of photographs taken in unit time, in addition to a function for taking a normal high resolution and high quality photograph.
An example of conventional partial scanning operation performed in a digital still camera will be explained below.
FIG. 10
is a view showing a configuration of an interline (interlace) scanning type CCD which is widely used at present. In
FIG. 10
, reference numeral
10
denotes photodiodes (PDs) which perform photoelectric conversion;
11
, four-phase drive vertical charge coupled devices (VCCDs) for transferring signal charges of the PDs
10
;
12
, horizontal charge coupled device (HCCD) for transferring the signal charges transferred from the VCCDs
11
by line; and
13
, an output amplifier for converting each signal charge representing a pixel, transferred via the HCCD
12
, into a voltage signal.
The CCD as described above is operated by an operation unit
200
which controls VCCD operation signals &phgr;V
1
to &phgr;V
4
for operating the VCCDs
11
and HCCD operation signals &phgr;H
1
and &phgr;H
2
for operating the HCCD
12
and outputs as timing pulses at proper levels.
In this type of CCD, normally, signal charges stored in the PDs
10
are transferred to the adjoining VCCDs
11
, then pairs of signal charges of adjoining pixels in the vertical direction are added by two adjoining lines. Thereafter, the signal charges added by two lines are sequentially read out via the HCCD
12
as signal charges of interlaced single lines. The combinations of two lines to be added are alternatively changed in each field period as shown by “field mode” in FIG.
10
. Besides the aforesaid “field mode” scanning method, there is a method for reading each signal charge independently without adding the signal charges. In this case, charges stored in pixels either in the odd lines or in the even lines are alternatively scanned in each field period (referred to as “frame mode” hereinafter).
Next, an output unit of the CCD is explained.
FIG. 11
is a schematic illustrating a configuration of an output unit of the CCD as an image sensing device. In
FIG. 11
, reference numeral
101
denotes a transfer gate of the last element of the two-phase drive HCCD
12
A signal charge is transferred to a floating diffusion gate
103
via an output gate
102
(normally, it is fixed to a predetermined potential) by operating the potential of the transfer gate
101
from High to Low. The signal charge transferred to the floating diffusion gate
103
is then converted to a voltage signal corresponding to the potential of the floating diffusion gate
103
by the output amplifier
13
. The output amplifier
13
is usually configured as a source follower.
Further, reference numeral
104
denotes a reset gate which functions as a “wall” when storing signal charges by applying a Low potential and drains the signal charge in the floating diffusion gate
103
to a reset drain
105
by applying a High potential.
FIG. 12
shows conceptual views illustrating potential profiles of the elements shown in
FIG. 11 and a
flow of signal charges, and
FIG. 13
is a timing chart of a pulse signal (&phgr;H
2
) to be applied to the two-phase drive HCCD
12
, a pulse signal (&phgr;R) to be applied to the reset gate
104
, and a resultant output voltage (Vccdout).
Referring to
FIGS. 11
to
13
, before reading a signal charge stored in each pixel (i.e., before time ts), residual charge in the floating diffusion gate
103
is drained at time tr. Below, the time tr is called “reset time”, time tf is called “field through time”, an output signal level at the field through time tf is called “field through level”, the time ts is called “image signal transfer time”, and an output signal level at the image signal transfer time ts is called “image signal level”.
Regarding frequencies of operation signals for the CCD, the highest frequency is limited in dependence upon performance of the amplifier
13
. An output from the CCD is applied with correlated double sampling (CDS) outside of the CCD, then amplified. In order to properly perform the above processes on the output from the CCD, sufficient duration of the output signal (Vccdout) at field through level as well as at image signal level is required.
Further, it is also necessary to remove effects of irregularity at the leading and trailing edges of operation signals for the HCCD
12
and the reset pulse &phgr;R. Further, there is a limitation due to frequency characteristics of the output amplifier
13
. With the aforesaid limitations, the frequencies of operation signals for the CCD are usually about 10 MHz. Note, when it is assumed that there is no foregoing limitation, frequencies of operation signals capable of securing necessary transfer efficiency for obtaining a non-deteriorated image via the HCCD is higher than 10 MHz, and may be several times higher than that.
Next, an operation for scanning a central area of 640×480 pixels of a 960×600-pixel CCD is explained with reference to FIG.
14
. In the 960×600-pixel CCD, the number of lines scanned in each field period is 300 either in the field mode or in the frame mode (in the field mode, signals of pair of adjoining pixels are combined to generate signals of 300 lines, and in the frame mode, signals either in the odd lines or the even lines of the 600 lines, namely 300 lines, are outputted).
First, right after transferring signal charges in the PDs
10
to VCCDs
11
at time t1 (in the field mode, right after the signal charges of two pixels are added in VCCDs
11
since charges are added as soon as they are transferred to VCCDs
11
), VCCDs
11
are operated at high speed to transfer charges of first 30 (=(300−240)/2) lines to discard the charges to a drain via the HCCD
12
during period t2. In a video camera, this operation is performed during vertical blanking period.
Since it is necessary to keep normal transfer efficiency during the discarding of the charges of the 30 lines, the frequencies of operation signals at this time is set between about 300 kHz and about 400 kHz. Since capacitance of the VCCDs
11
is large, the frequencies of the operation signals for operating the CCD is limited to the above, at most.
The drain may be arranged in parallel to the HCCD
12
, or downstream of the HCCD
12
. Further, the drain may be substituted by a drain configured in the output amplifier
13
. Further, according to
FIG. 14
, operation signals are also applied to the HCCD
12
during the period t2 for transferring from the VCCDs
11
, the signal charges of the 30 lines to be discarded. However, there is a method for temporarily storing the charges to be discarded in HCCD
12
. In this case, right after the charges of 30 lines to be discarded are transferred to HCCD
12
, the charges are transferred via HCCD
12
at high speed (normally, at tens of MHz) to be discarded, during period t3.
After discarding the unnecessary charges of the 30 lines via th
Kondo Kenichi
Yanai Toshikazu
Morgan & Finnegan , LLP
Nguyen Madeleine
LandOfFree
Solid-state image sensing device and operation method thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Solid-state image sensing device and operation method thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solid-state image sensing device and operation method thereof will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2973686