Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
2001-08-29
2003-12-02
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S214100, C257S072000, C382S124000
Reexamination Certificate
active
06657175
ABSTRACT:
This application claims the benefit of Korean patent application No. 2000-51747, filed Sep. 1, 2000 in Korea, which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical detecting sensor, and more particularly, to a thin film transistor (TFT) type optical detecting sensor using a small-sized drive integrated circuit (IC).
2. Discussion of the Related Art
Generally, optical detecting sensors are used in facsimile and digital copying machines, and in fingerprint recognition systems as an image reader. The optical detecting sensor stores electric charge in accordance with an intensity of light that is reflected from a detecting subject, and then outputs the electric charge via a drive circuit. In recent years, a TFT-type optical detecting sensor has been suggested in which the TFT changes its electrical characteristics in response to incident light.
The TFT-type optical sensor includes a light source that generates light, a window that introduces the light to a subject for detection, a sensor TFT, a storage capacitor, and a switch TFT. The sensor TFT generates an optical current in accordance with the intensity of the light reflected from the subject, and the storage capacitor receives the optical current and stores an electric charge indicative of the optical current. This electric charge represents reflected light intensity data. Then, the switch TFT transfers there reflected intensity light data from the storage capacitor to a main system in accordance with a control signal received from an exterior circuit.
FIG. 1
shows a conventional TFT-type optical sensor including an array substrate
1
, and a backlight unit
2
disposed beneath the array substrate
1
. The array substrate
1
detects the presence of a subject, stores data for related to the subject, and transmits the data to a main system (not shown), such as the fingerprint recognition system, for example. The backlight unit
2
provides light to the array substrate
1
. At this point, the array substrate
1
includes a plurality of unit pixels “P” (in
FIG. 2
) each having a sensor TFT “T
1
” (in FIG.
2
), a storage capacitor “C” (in FIG.
3
), and a switch TFT “T
2
” (in FIG.
2
).
FIGS. 2 and 3
show the unit pixel “P” of the array substrate
1
(in
FIG. 1
) of the conventional TFT-type optical sensor. As shown, a sensor gate line
21
, a sensor data line
61
, a switch gate line
25
, and a switch data line
65
help to define the unit pixel “P.” The sensor gate line
21
and the sensor data line
61
are formed orthogonal to each other so as to cross each other, and the switch gate line
25
and the switch data line
65
are spaced apart from the sensor gate line
21
and the sensor data line
61
, respectively.
The unit pixel “P” is divided into a photo-sensing region “A,” a storing region “B,” and a switching region “C,” all which are formed on a transparent substrate
10
. A sensor gate electrode
22
, a first storage electrode
24
, and a switch gate electrode
26
are disposed in the photo-sensing region “A,” the storing region “B,” and the switching region “C,” respectively. The sensor gate electrode
22
and the switch gate electrode
26
integrally protrude from the sensor gate line
21
and the switch gate line
25
, respectively. Alternatively, parts of the sensor gate line
21
and the switch gate line
25
may not protrude, but used as the sensor gate electrode
22
and the switch gate electrode
26
, respectively. The first storage electrode
24
integrally protrudes from the sensor gate line
21
.
In
FIG. 3
, a first insulating layer
30
covers the sensor electrode
22
, the first storage electrode
24
, and the switch gate electrode
26
. On the first insulating layer
30
, a sensor silicon layer
41
and a switch silicon layer
42
are formed in the sensing region “A” and the switching region “B,” respectively. A sensor ohmic contact layer
52
and a switch ohmic contact layer
54
are formed on portions of the sensor silicon layer
41
and the switch silicon layer
42
, respectively. A sensor source electrode
62
and a sensor drain electrode
63
are formed over the sensor silicon layer
41
, and a switch source electrode
66
and a switch drain electrode
67
are formed over the switch silicon layer
42
. A first storage electrode
24
integrally protrudes from the sensor gate line
21
toward the unit pixel region “P.” The sensor source electrode
62
is connected with the sensor data line
61
, and the sensor drain electrode
63
is spaced apart from the sensor source electrode
62
with the sensor gate electrode
22
centered therebetween. The switch source electrode
66
is connected with the switch data line
65
, and the switch drain electrode
67
is spaced apart from the switch source electrode
65
with the switch gate electrode
26
centered therebetween. A second storage electrode
64
is formed connecting the switch drain electrode
67
and the sensor drain electrode
63
, and the second storage electrode
64
overlaps the first storage electrode
24
.
A second insulating layer
70
covers the sensor source electrode
62
, the sensor drain electrode
63
, the second storage electrode
64
, the switch source electrode
66
, and the switch drain electrode
67
. A shielding pattern
80
that can be made of an opaque material is formed on the second insulating layer
70
over the switch silicon layer
42
.
As shown in
FIG. 4
, the array substrate
1
, having the unit pixels “P” as shown in
FIG. 2
, is connected with a plurality of output lines
92
that are electrically connected with a drive integrated circuit (IC)
93
. Specifically, each switch data line
65
of
FIG. 2
in the array substrate
1
is electrically connected with a corresponding output line
92
. Therefore, when the switch TFT “T
2
” (in
FIG. 2
) switches data, the data is transferred to the drive IC
93
via the output line
92
, such that the main system (not shown) can read the data from the drive IC
93
.
When the backlight unit
2
of
FIG. 1
is switched on to produce light, the sensor TFT “T
1
” of
FIG. 2
generates data representative of reflected light, and the storage capacitor “C” of
FIG. 3
stores the data. Then, the switch TFT “T
2
” of
FIG. 2
switches the data in accordance with a control signal received from an exterior circuit (not shown). The switched data is subsequently transferred to the drive IC
93
via the switch data line
65
of FIG.
2
and the output line
92
.
As previously mentioned, each of the plurality of data lines
65
of
FIG. 2
are correspondingly connected with the same number of output lines
92
. Moreover, the drive IC
93
may have a plurality of sub-circuits (not shown) each connecting with a corresponding output line
92
. In other words, the drive IC
93
of the conventional TFT-type optical detecting sensor has the same number of sub-circuits as the plurality of output lines
92
. Accordingly, the drive IC
93
may be very large in size and very complicated to manufacture, thereby creating high material cost and low manufacturing yield.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a TFT-type optical detecting sensor that substantially obviates one or more of problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an improved TFT type optical sensor implementing a small-sized drive IC.
Additional features and advantages of the invention will be set forth in the description which follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a thin film transistor (TFT) type optical detecting sensor includes
Lee Jae-Kyun
Yoon Tae-Hwan
Allen Stephone B.
LG.Philips LCD Co. , Ltd.
Morgan & Lewis & Bockius, LLP
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