Abstract:
A thin film transistor-type optical detecting sensor includes an array substrate provided with a plurality of regions, each region including a plurality of sensor thin film transistors each generating an optical current in response to light reflected from a subject for detection, a plurality of storage capacitors each connected with a corresponding one of the plurality of sensor thin film transistors to store charge representative of the optical current, a plurality of switch thin film transistors each connected with a corresponding one of the plurality of storage capacitors for selectively outputting the stored charge, and a plurality of output lines each connected with a corresponding one of the plurality of switch thin film transistors, a backlight unit disposed beneath the array substrate to provide the light to the plurality of regions, and a drive IC including a plurality of sub-circuits, wherein an n th  sub-circuit is connected with an n th  output line of each region of the array substrate.

Description:
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 an array substrate provided with a plurality of regions, each region including a plurality of sensor thin film transistors each generating an optical current in response to light reflected from a subject for detection, a plurality of storage capacitors each connected with a corresponding one of the plurality of sensor thin film transistors for storing charge representative of the optical current, a plurality of switch thin film transistors each connected with a corresponding one of the plurality of storage capacitors for selectively outputting the stored charge, and a plurality of output lines each connected with a corresponding one of the plurality of switch thin film transistors, a backlight unit disposed beneath the array substrate to provide the light to the plurality of regions, and a drive IC including a plurality of sub-circuits, wherein an n th  sub-circuit is connected with an n th  output line of each region of the array substrate. 
     In another aspect, a thin film transistor-type optical detecting sensor includes an array substrate provided with a plurality of regions, each region including a plurality of sensor thin film transistors each generating an optical current in response to light reflected from a subject for detection, a plurality of storage capacitors each connected with a corresponding one of the plurality of sensor thin film transistors to store charge representative of the optical current, a plurality of switch thin film transistors each connected with a corresponding one of the plurality of storage capacitors to selectively output the stored charge, and a plurality of output lines each connected with a corresponding one of the plurality of switch thin film transistors. 
     In another aspect, a method for manufacturing a thin film transistor optical detecting sensor includes the steps of providing an array substrate with a plurality of regions, each region including a plurality of sensor thin film transistors each generating an optical current in response to light reflected from a subject for detection, a plurality of storage capacitors each connected with a corresponding one of the plurality of sensor thin film transistors for storing charge representative of the optical current, a plurality of switch thin film transistors each connected with a corresponding one of the plurality of storage capacitors for selectively outputting the stored charge, and a plurality of output lines each connected with a corresponding one of the plurality of switch thin film transistors, providing a backlight unit beneath the array substrate for providing the light for the plurality of regions, and providing a drive IC including a plurality of sub-circuits, wherein an n th  sub-circuit is connected with an n th  output line of each region of the array substrate. 
     In another aspect, a method of manufacturing an array substrate includes the steps of providing the array substrate with a plurality of regions, providing each of the plurality of regions with a plurality of sensor thin film transistors each generating an optical current in response to light reflected from a subject for detection, providing each of the plurality of regions with a plurality of storage capacitors each connected with a corresponding one of the plurality of sensor thin film transistors for storing charge representative of the optical current, providing each of the plurality of regions with a plurality of switch thin film transistors each connected with a corresponding one of the plurality of storage capacitors for selectively outputting the stored charge, and providing each of the plurality of regions with a plurality of output lines each connected with a corresponding one of the plurality of switch thin film transistors. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
     FIG. 1 is a perspective view showing a conventional TFT-type optical sensor; 
     FIG. 2 is a plan view showing a unit pixel of the conventional TFT type optical sensor; 
     FIG. 3 is a cross-sectional view taken along a line “III—III” of FIG. 2; 
     FIG. 4 is a plan view showing an interconnection of a drive IC and an array substrate of the conventional TFT-type optical sensor; 
     FIG. 5 is a plan view showing an interconnection of a drive IC and an array substrate of a TFT-type optical sensor according to the present invention; and 
     FIG. 6 is a cross-sectional view of the TFT type optical sensor of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiment of the present invention, which is illustrated in the accompanying drawings. 
     In FIG. 5, an array substrate  110  of a TFT optical detecting sensor  100  according to the invention includes a first region  111 , a second region  112 , and a third region  113 , with a backlight unit  170  which is shown in FIG. 6, disposed beneath the array substrate  110 . In addition, a plurality of sensor thin film transistors  101 , a plurality of storage capacitors  102 , and a plurality of switch thin film transistors  103  are formed within each of the first, second, and third regions  111 ,  112 , and  113 . The plurality of storage capacitors  102  are connected with a corresponding one of the plurality of sensor thin film transistors, and the plurality of switch thin film transistors  103  are each connected with a corresponding one of the plurality of storage capacitors  102 . 
     As shown in FIG. 6, the backlight unit  170  includes a first independent backlight  170   a,  a second independent backlight  170   b,  and a third independent backlight  170   c,  which correspond to the first  111 , second  112 , and third  113  regions of the array substrate  110 , respectively. The first to third independent backlights  170   a  to  170   c  provide light for the array substrate  110  and operate independently of each other. Therefore, the first to third regions  111  to  113  of the array substrate  110  independently receive the light from the backlight unit  170 . Although the array substrate  110  is divided into three regions, the number of regions may vary. Moreover, the number of the independent backlights of the backlight unit  170  may vary in accordance with the number of regions of the array substrate  110 . 
     Returning to FIG. 5, the TFT optical detecting sensor  100  further includes a drive IC  150  electrically connected with the plurality of switch thin film transistors  103  of the array substrate  110  via a plurality of output lines that may include a first one  121 , a second one  122 , a n th  one  123 , a (n+1) th  one  131 , a (n+2) th  one  132 , 2n th  one  133 , a (2n+1) th  one  141 , a (2n+2) th  one  142 , and a last one  143 . The first to n th  output lines  121  to  123  may be electrically connected with the plurality of switch thin film transistors  103  of the first region  111 , and the (n+1) th  to 2n th  output lines  131  to  133  may be electrically connected with the plurality of switch thin film transistors  103  of the second region  112 . The (2n+1) th  to last output lines  141  to  143  may be electrically connected with the plurality of switch thin film transistors  103  of the third region  113 . At this point, the (n+1) th  output line  131  and the (2n+1) th  output line  141  may serve as the first output lines of the second region  112  and the third region  113 , respectively. The 2n th  output N line  133  and the last output line  143  may serve as the last output lines of the second region  112  and the third region  113 , respectively. That is to say, each region may be connected with n output lines. Specifically, a plurality of switch data lines (not shown) may be formed on the array substrate  110 , and each output line may electrically connect a corresponding switch data line with the drive IC  150 . 
     The drive IC  150  may include first to n th  sub-circuits  151  to  153 . The first sub-circuit  151  may electrically connect with the first output line of each region, and the second sub-circuit  152  may electrically connect with the second output line of each region. In other words, the first sub-circuit  151  may be electrically connected with the first output line  121 , the (n+1) th  output line  131 , and the (2n+1) th  output line  141 , and the second sub-circuit  152  may be electrically connected with the second output line  122 , the (n+2) th  output line  132 , and the (2n+2) th  output line  142 . Like the first and second sub-circuits  151  and  152 , each sub-circuit may be electrically connected with the corresponding output lines having the same relative orders with respect to each region. 
     Accordingly, since the array substrate  110  is divided into “m” number of regions, and each region is connected with “n” number output lines, there exists “m” by “n” (m×n) number of output lines connected with the array substrate  110 . The “m” by “n” number of output lines connect the plurality of switch data lines (not shown) of the array substrate  110  with the drive IC  150 . At this point, though there exist “m” by “n” number of output lines connected with the array substrate  110 , just “n” number of sub-circuits are included in the drive IC  150 , thereby achieving a smaller size of the drive IC  150 . 
     Returning now to FIG. 6, an operation of the TFT optical detecting sensor is explained. After the first backlight  170   a  is switched on to provide light, the first region  111  generates a first set of data. The first set of data is transferred to first to n th  sub-circuits  151  to  153  of the drive IC  150  via the first to n th  output lines  121  to  123 , and then is output to a main system (not shown) from the drive IC  150 . After the first backlight  170   a  is switched off to cease production of light, the second backlight  170   b  is switched on to produce light, such that the second region  112  generates a second set of data. The second set of data is transferred to the first to n th  sub-circuits  151  to  153  of the drive IC  150  via the (n+1) th  to 2n th  output lines  131  to  133 , and then is output to a main system (not shown) from the drive IC  150 . Subsequently, the second backlight  170   b  is switched off to cease production of light, and the third backlight  170   c  is switched on to produce light, such that the third region  113  generates a third set of data. The third set of data is transferred to the first to n th  sub-circuits  151  to  153  of the drive IC  150  via the (2n+1) th  to last output lines  141  to  143 , and then is output to a main system (not shown) from the drive IC  150 . 
     When the first backlight  170   a  is switched on, it provides light only for the first region  111 , and thus, sensor TFTs (not shown) formed on the first region  111  generate the first set of data. At this point, because the second and third backlights  170   b  and  170   c  are both in “off” state, sensor TFTs (not shown) of the second and third regions  112  and  113  cannot generate any data. Though the first output line  121 , the (n+1) th  output line  131 , the (2n+1) th  output line  141  are connected with the first sub-circuit  151  of the drive IC  150 , they are electrically independent due to the independent switching of the first to third backlights  170   a  to  170   c.    
     Each of the other output lines connected with the first region  111  also has the above-mentioned electrical independence with respect to the correspondingly positioned output lines connected with the second or third regions  112  and  113 . Thus, during the “on” state of the first backlight  170   a,  only the first set of data is generated by the first region  111  and is transferred to the first to n th  sub-circuits  151  to  153  of the drive IC  150  via the first to n th  output lines  121  to  123 , regardless of the other output lines connected with the same sub-circuits. 
     The total number of the output lines may be constant. Then, if the number of regions increases, the number of sub-circuits included in the drive IC decreases. That is, when the number of the regions is “m” and the number of the output lines connected with each region is “n,” the total number of the output lines is “m” by “n” and the number of the sub-circuits is “n.” At this point, because the total number “m” by “n” of the output lines may be constant, the number “n” of the sub-circuits may be decreased by increasing the number “m” of the regions. For example, if the total number of the output lines is twelve and the number of the regions is three, just four sub-circuits are needed for the drive IC according to the present invention. Moreover, redundant sub-circuits may be further included in the drive IC  150  so that when some sub-circuits malfunction, the redundant sub-circuits can be substituted for them. That is to say, the number of the sub-circuits is preferably “m+α”, wherein “α” is an integer equal to or larger than 1. 
     Still referring to FIG. 6, a light filter  160  may be disposed between the array substrate  110  and the backlight unit  170 . If light is incident normal to a surface of the light filter  160 , the light can pass through the light filter  160 . However, if the light is incident at an angle with respect to the surface of the light filter  160 , the light will be blocked by the light filter  160  and will not pass through. Accordingly, when one of the backlights  170   a  to  170   c  is switched on, light from the switched-on backlight is provided only to the corresponding region of the array substrate  110  disposed directly above on the switched-on backlight. That is, only the light generated from the switched-on backlight disposed directly beneath the corresponding region of the array substrate  110  passes through the color filter, whereas light does not pass through the color filter in all other regions of the array substrate  110 . Accordingly, each of the first to third regions  111  to  113  of the array substrate  110  can operate independently, and thus only a desired region generates data. 
     As above explained, according to the present invention, the array substrate of the TFT-type optical detecting sensor is divided into a plurality of regions to decrease the number of sub-circuits of the drive IC. Specifically, if the array substrate is divided into “m” regions, the number of sub-circuits is decreased to 1/m with respect to that of a conventional TFT-type optical detecting sensor. In addition, the number of bonding pads used for connecting the output lines with the array substrate is also decreased, thereby achieving lower fabrication costs, lower material costs, and higher fabrication yields. 
     It will be apparent to those skilled in the art that various modifications and variation can be made in the method of manufacturing a thin film transistor of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.