Multi-resolution charge-coupled device sensing device

Details Multi-resolution charge-coupled device sensing device Multi-resolution charge-coupled device sensing device

2003-08-13

2004-11-16

Porta, David (Department: 2878)

Radiant energy

Photocells; circuits and apparatus

Photocell controlled circuit

C348S294000, C377S063000

Reexamination Certificate

active

06818878

ABSTRACT:

This application claims the benefit of Taiwan application Serial No. 91118946, filed Aug. 22, 2002.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a multi-resolution charge-coupled device (CCD) sensing device, and more particularly to a multi-resolution CCD sensing device applied to the CCD module and the Contact Image Sensor (CIS) module.
2. Description of the Related Art
Scanners have become widely used in recent years. The user is required to choose from scanning modes with different resolutions when scanning, in accordance with the properties of the document to be scanned. There are several conventional ways to set the resolution, which might be accomplished by using either software or hardware. Using hardware is usually faster and more direct.
The scanning procedures for the scanner with the CCD module are stated as follows. The carriage in the scanner has a light source, and after the light source produces light, it is reflected by the document being scanned, and the light is directed back to the carriage. The light signal is processed by optical components, such as mirrors and lenses, and is then received by the CCD module. The CCD module senses the magnitude of the light signal and then generates corresponding scanned image data.
Referring to
FIG. 1
, a CCD module using a conventional CCD sensing apparatus is shown. The CCD module includes a CCD sensing device
102
, a control circuit
104
, and an output capacitor C. The CCD sensing device
102
includes a photo sensor set
106
, a shift gate
108
, and a CCD shift register
110
. The CCD sensing device
102
, with a resolution of 1200 dpi (dot per inch), is used here as an example. If a CCD sensing device
102
is used to sense a document of 8 inches in width, then the photo sensor set
106
includes 1200×8=9600 photo sensing components.
FIG. 1
shows eight photo sensing components, D
1
~D
8
, that convert light signals into charge signals. The photo sensing components may be photo diodes. The shift gate
108
is used for controlling the transmission of the charge signals. When the photo-sensing components are exposed to light for a predetermined period of time, the photo sensing components generate a corresponding amount of charge, and then the shift gate
108
is turned on to transfer the charge signals to the CCD shift register
110
. The CCD shift register
110
may be a two-phase CCD shift register
110
. The CCD shift register
110
, with 1200 dpi for sensing a document of 8 inches in width, includes 19200 CCD components.
FIG. 1
shows 16 CCD components, E
1
~E
8
and E
1
′~E
8
′, that correspond to the photo-sensing components D
1
~D
8
. The CCD components E
1
~E
8
and E
1
′~E
8
′ are arranged alternately, and are also controlled by phase signals F
1
and F
2
, respectively. Subsequently, by the control of phase signals F
1
and F
2
, the charge signals stored in the CCD components are sequentially output. As shown in
FIG. 1
, eight photo-sensing components D
1
~D
8
out of the 9600 photo sensing components generate charge signals S
1
~S
8
. The charge signals S
1
~S
8
can be transferred to CCD components E
1
~E
8
. The control circuit
104
is used to store the charge signals, which are output from the CCD shift register
110
, in the capacitor C sequentially to acquire the analog output signal Out. The output signal Out is processed by a next stage circuit (not shown), and the scanned image data are then obtained.
However, users need to be able to use different scanning modes with different resolutions. For example, a high-resolution scanning mode is required if the document to be scanned is a color image. If the document to be scanned is text, it simply requires a low-resolution scanning mode. In FIG.
1
, due to the CCD sensing device
102
is a high-resolution sensing device, some properties of the CCD sensing device
102
have to be discarded during low-resolution scanning. Besides, scanning time may be wasted during low-resolution scanning.
FIG. 1
shows the CCD sensing device
102
configured for high resolution and being used for low-resolution 600 dpi scanning; the operation is described as follows: after the photo-sensing components D
1
~D
8
are exposed to light, the charge signals S
1
~S
8
are stored in the CCD components E
1
~E
8
. When the charge signals S
1
~S
8
are output, a simpler method is to require the control circuit
104
to store 4800 sequential charge signals, such as S
2
, S
4
, S
6
, and S
8
, etc., in capacitor C in order to obtain the 600 dpi scanned image data. Another improved method is to require the control circuit
104
to store 9600 sequential charge signals grouping every two charge signals together, such as S
1
+S
2
, S
3
+S
4
, S
5
+S
6
, and S
7
+S
8
, etc., in capacitor C to obtain the corresponding analog voltage values, such as charge signals S
1
+S
2
, S
3
+S
4
, S
5
+S
6
, and S
7
+S
8
, etc., so as to obtain 600 dpi scanned image data. Although the scanned image data are of low resolution, the time it takes to shift out the electric charges stored in the CCD components to the capacitor C is still the same as before and does not decrease. Therefore, for the conventional CCD sensing device
102
, scanning at a low resolution take the same amount of time as scanning at a high resolution.
The chips for CCD sensing at different resolutions have been widely used in the marketplace. To solve the above-mentioned problem, CCD modules with multiple CCD sensing devices of several different resolutions have also become available on the market.
Referring to
FIG. 2
, a conventional CCD module with multiple CCD sensing devices is shown. The CCD module with three CCD sensing devices is used as an example for further illustration. The CCD module has a CCD sensing device
202
a
with a resolution of 1200 dpi, a CCD sensing device
202
b
with a resolution of 600 dpi, and a CCD sensing device
202
c
with a resolution of 300 dpi. Similarly, using CCD sensing devices for an 8-inch wide document as an example, the CCD sensor sets
206
a
,
206
b
, and
206
c
of the CCD sensing devices
202
a
,
202
b
, and
202
c
have 9600, 4800, and 2400 photo-sensing components, respectively. Here, the eight photo sensing components Da
1
~Da
8
, Db
1
~Db
8
, and Dc
1
~Dc
8
are used in the example. The CCD sensing devices
202
a
,
202
b
, and
202
c
, respectively, include CCD shift registers
210
a
,
210
b
, and
210
c
; and the CCD shift registers
210
a
,
210
b
, and
210
c
include 2400, 1200 and 600 CCD components, respectively. The CCD shift register
210
a
is controlled by phase signals F
1
a
and F
2
a
, while the CCD shift register
210
b
is controlled by phase signals F
1
b
and F
2
b
, and the CCD shift register
210
c
is controlled by phase signals F
1
c
and F
2
c
. When shift gates
208
a
,
208
b
, and
208
c
are turned on, the charge signals stored in the CCD components Da
1
~Da
8
, Db
1
~Db
8
, and Dc
1
~Dc
8
can be shifted to the CCD shift registers
210
a
,
201
b
, and
210
c
, respectively.
When the user chooses different scanning modes with different scanning resolutions, the control circuit
204
will choose the outputs of the corresponding CCD sensing devices
202
a
,
202
b
, and
202
c
and send them to capacitor C. Thus, the photo sensor sets
206
a
,
206
b
, and
206
c
are simultaneously exposed to light and store the charge signals in the CCD shift registers
210
a
,
210
b
, and
210
c
while scanning. When choosing the scanning mode of 1200 dpi, the control circuit
204
chooses the output of CCD shift register
210
a
; or, when choosing the scanning mode of 600 dpi or 300 dpi, the control circuit
204
chooses the output of CCD shift registers
210
b
and
210
c
. Since the CCD components of the CCD shift registers
210
b
and
210
c
are both far fewer than that of CCD shift register
210
a
, the time it takes to shift out the stored charges to capacitor C is far less in CCD shift registers
210
b
or
210
c
than in CCD shift r

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