Television – Camera – system and detail – Solid-state image sensor
Reexamination Certificate
1999-11-15
2004-07-20
Garber, Wendy R. (Department: 2712)
Television
Camera, system and detail
Solid-state image sensor
C348S324000
Reexamination Certificate
active
06765615
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to apparatus for reducing minimum exposing time of an image-acquiring device of an image processing system, and particularly relates to apparatus for reducing minimum scanning time necessary for a high-resolution-image-acquiring device to scan an object in a low resolution.
2. Description of the Prior Art
An image processing system makes use of focusing a reflected light beam from an object through a photodetector to generate an electrical signal representing the image of the object for further processing, storing and displaying. Among various applications such as image scanners, camera recorders or facsimile machines everywhere in the modern world, in spite of somewhat differences between these machines, there is one necessary primary step. In other words, it is necessary for an image system to acquire an image signal by converting an image of the object to an electrical signal.
Taking an image scanner as example, the block diagram in the prior art is shown in FIG.
1
. It is composed of an exposing timing signal source
8
, a shift control signal source
9
, a light source
10
, a glass surface
11
, a mirror
12
, a lens
13
, a photo-sensing device
14
, a charge coupled device (CCD) shift register
15
, a pre-processing device
16
and a post-processing device
17
. The pre-processing device
16
is implemented by electrically coupling a dc-gain voltage amplifier
16
a
, an analogue-to-digital converter (ADC)
16
b
. The waveform of the output signal
20
, shown in
FIG. 2
, of an exposing timing signal source
8
is fed to photo-sensing device
14
.
This system mentioned above operates in the way that photo-sensing device
14
converts the light emitted by light source
10
, a text or a picture firstly reflected by the glass surface
11
and secondly reflected by the mirror
12
to an image signal.
Note that when the front edge of pulse
21
(
FIG. 2
) is fed to the photo-sensing device
14
, the photo-sensing device
14
pour out all the charges to the CCD shift register
15
. After the photo-sensing device
14
has poured out all the stored charges, it cumulate the charges produced in the time interval between the back edge of the pulse
21
and front edge of the pulse
23
. Subsequently, the photo-sensing device begins to produce and accumulate charge until next front edge arrives. Thus an optical image is transformed into an electrical signal. The electrical signal parallel output to the CCD shift register
15
, and is serially fed to the pre-processing device
16
.
To precisely describe the operation of photo-sensing device
14
responding to the exposing timing signal source
8
, and that of the CCD shift register
15
responding to the shift control signal source
9
. The operation of the system is described below. A line of scanned object is exposed to the light source
10
, and the photo-sensing device
14
transfers the light from the line on the scanned object into a plurality of groups of charges responding to the pulse
19
and pulse
21
of the output signal
20
of the exposing timing signal source
8
. Each cell of the photo-sensing device
14
is exposed to the light from the lens
13
during the exposing time interval between pulse
21
and
23
of the output signal
20
of the exposing timing signal source
8
. After the pulse
21
has arrived at the photo-sensing device
14
, the plurality groups of charges is fed to the CCD shift register
15
at the same time. In addition, each of the plurality groups of charges generated by each cell of the photo-sensing device
14
is fed to the corresponding potential-energy wells of the CCD shift register
15
.
Subsequently, each of the plurality groups of charges stored in each potential-energy wells in the CCD shift register
15
is transmitted to the pre-processing device
16
one after another responding to the output clock pulse
30
of the shift control signal source
9
. The plurality groups of charge is stored in each potential-energy well of the CCD shift register
15
before the pulse
23
next to the pulse
21
arrive at the photo-sensing device
14
. In addition, each group of charge stored in each potential-energy well of the CCD shift register
15
is subsequently transmitted to the pre-processing device
16
. In other words, the group of charge stored in the first potential-energy well al of the CCD shift register
15
is transmitted to the pre-processing device
16
responding to the first pulse
31
A
1
of the clock pulse
30
(shown in FIG.
3
).
Then the group of charge stored in the second potential-energy well a
2
of the CCD shift register
15
is transmitted to the pre-processing device
16
responding to the second pulse
31
A
2
of the clock pulse
30
(shown in FIG.
3
). Finally the group of charge stored in the n'th potential-energy well an of the CCD shift register
15
is transmitted to the pre-processing device
16
responding to the n'th pulse
31
An of the clock pulse
30
(shown in FIG.
3
). For the operation mentioned above, it is designed that after the n'th pulse
31
An of the clock pulse
30
has been arrived at the CCD shift register
15
, the pulse
23
of the pulse
20
arrives at the photo-sensing device
14
. So the exposing time of the photo-sensing device
14
is a fixed value, i.e., time interval between pulse
21
and pulse
23
, which is a multiplication of pixel rate and pixel number, in spite of the variation of operational mode.
The pixel rate mentioned above is the number of group of charge stored in the potential-energy well of the CCD shift register
15
in a unit time interval. The pixel number mentioned above is the number of the potential-energy well of the CCD shift register
15
. In a high resolution mode, more cells of the photo-sensing device
14
are utilized to be exposed to the light source
10
. Whereas, in a low resolution mode, less cells of the photo-sensing device
14
are utilized to expose to the light source
10
. In addition, the lens seat
18
is moved to a position to fit the scope of projection to the photo-sensing device
14
. The position of the lens
13
and the lens seat
18
in the low resolution mode which employing less cells of photo-sensing device
14
is not illustrated in FIG.
1
. However the necessary exposing time interval employed in the high resolution mode is the same as that of the low resolution mode. So the user has to wait for a while even the low resolution mode of the image processing system is employed. This is an origin of waste of time for the user.
After the electrical signal has been fed to the pre-processing device
16
, the dc-gain voltage amplifier
16
a
adjusts the dc-gain of the electrical signal and then feed it to the ADC
16
b
. Contrast adjustment by a Gamma characteristic is performed by the post-processing means
17
, and then obtained the output signal which can be further processed or displayed.
In a traditional image-acquiring device of a modern image processing system, it is necessary to provide the user with the high resolution mode and the low resolution mode for various applications. Fewer cells of photo-sensing device
14
are exposed to the light source
10
in the low resolution mode than the high resolution mode. However, the charges in each cell of the photo-sensing device
14
are transmitted through the CCD shift register
15
to the pre-processing device
16
in both high resolution mode and low resolution mode. So the necessary exposing timing interval for the high resolution mode and the low resolution mode is all the same, which is the multiplication of the pixel rate and the pixel number of the photo-sensing device
14
. And this is the waste of time for the user when a lower resolution mode of the image processing system is employed. In the traditional image-acquiring device of a modern image processing system, when the frequency of the output signal of the shift control signal source is increased to lower the exposing timing interval. It tends to result the residual charges generated i
Chen Shih-Huang
Kuo Shih-Zheng
Garber Wendy R.
Sughrue & Mion, PLLC
Umax Data Systems Inc.
Wilson Jacqueline
LandOfFree
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