Abstract:
Particles in a glass substrate are measured by executing following steps: sequentially conveying a plurality of glass substrates; scanning with a camera a unit area of a glass substrate in a direction of a travel path of the glass substrate and storing particle information thereof; shifting the camera to a position corresponding to a next unit area for a succeeding glass substrate; storing information on the particles in the unit area of the succeeding glass substrate obtained by scanning the glass substrate; estimating whether a sum of the respective scanned unit areas is within an allowed limit of an area of a glass substrate; and returning to the third step if an answer from the fifth step is “No” or storing information on the particles in the entire glass substrate if the answer is “Yes”.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a method for measuring particles in a glass substrate; and, more particularly, to a method capable of providing sampling information on particles in a glass substrate without interrupting the process line of the cleaned glass substrate.  
       BACKGROUND OF THE INVENTION  
       [0002]     Generally, a glass substrate used in manufacturing a flat display such as a TFT-LCD (thin film transistor—liquid crystal display), a PDP (plasma display panel), an EL (electro luminescence) and the like is formed by molding and then cutting a molten glass melted in a glass melting furnace to meet an initial product standard, which is then coated with a protective film on a surface thereof.  
         [0003]     Unlike a surface defect inspection of such glass substrate, which employs a general vision system, a method for measuring the number of particles present in such a glass substrate employs a high precision laser sensor, which takes a substantial amount of time to perform. Accordingly, a glass substrate undergoing such a time consuming process is taken off the process line, and moreover loading of the glass substrate for such process is non-automated and is done manually.  
         [0004]     Such a manual operation of the glass substrate for measuring particles present therein requires a cleaning room with a large interior space. Furthermore, under such process, obtaining and storing of particles data are carried out manually, further exacerbating the time issue and causing great inconvenience to an operator.  
         [0005]     Moreover, when dealing with a glass substrate of considerable size, loading thereof becomes problematic and a loading device is required.  
       SUMMARY OF THE INVENTION  
       [0006]     It is, therefore, an object of the present invention to provide a method for measuring particles in a glass substrate capable of providing sampling information on the particles in a glass substrate without interruption in a process line; utilizing a clean room space efficiently; and performing an inspection of a large-sized glass substrate.  
         [0007]     In accordance with a preferred embodiment of the present invention, there is provided a method for measuring particles in a glass substrate, including the steps of: (a) sequentially conveying a plurality of glass substrates; (b) scanning with a camera a unit area of a glass substrate in a direction of a travel path of the glass substrate and storing particle information thereof, wherein the camera is placed above the travel path of the glass substrates and a scan width thereof is preset; (c) shifting the camera in a direction perpendicular to the travel path of the glass substrate to a position corresponding to a next unit area for a succeeding glass substrate; (d) storing information on the particles in the unit area of the succeeding glass substrate obtained by scanning the glass substrate using the shifted camera; (e) estimating whether a sum of the respective scanned unit areas is within an allowed limit of an area of a glass substrate; and (f) returning to step (c) if an answer from step (e) is “No” or storing information on the particles in the entire glass substrate obtained by summing up the information on the particles in the respective scanned unit areas if the answer is “Yes”. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:  
         [0009]      FIGS. 1A and 1B  present a flow chart showing a method for measuring particles in a glass substrate in accordance with the present invention;  
         [0010]      FIG. 2  shows a front view of an apparatus to perform a method for measuring particles in a glass substrate in accordance with the present invention;  
         [0011]      FIG. 3  illustrates a side view of an apparatus to perform a method for measuring particles in a glass substrate in accordance with the present invention;  
         [0012]      FIG. 4  depicts a construction of an apparatus to perform a method for measuring particles in a glass substrate in accordance with the present invention; and  
         [0013]      FIG. 5  represents a scanned result obtained by using a method for measuring particles in a glass substrate in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     Referring to  FIGS. 1A, 1B  and  2 , a method for measuring particles in a glass substrate in accordance with the present invention is a method for measuring information on particles P, i.e., a number, positions, sizes, and the like, in a glass substrate  1 , which includes the following steps: step S 10  wherein a plurality of glass substrates  1  are conveyed sequentially; step S 20  wherein information on the particles P residing in a unit area of the glass substrate  1  scanned by a camera  10  is stored as data, the camera  10  maintaining a desired distance from the glass substrate  1 ; step S 30  wherein, while maintaining the desired distance from the glass substrate  1 , the camera  10  is moved a preset distance, e.g., a scan width of the camera  10 , in a direction perpendicular to the travel path of the glass substrate  1 ; step S 40  wherein, after scanning the following glass substrate  1  by the camera  10 , information on the particles P residing in a unit area of the glass substrate  1  is stored; and step S 50  wherein, if a sum of the unit areas of the glass substrates  1  scanned by the camera  10  is within an allowed limit of the area of one glass substrate  1 , information on the particles P in the entire glass substrate  1  is obtained and stored by summing up the information on the particles P residing in the respective scanned unit areas.  
         [0015]     At step S 10 , a plurality of glass substrates  1  entering a clean room after being washed are conveyed sequentially. The glass substrates  1  are conveyed by rollers  22  arranged at both sides of a floating table  20 , being floated by air jets coming out of a plurality of floating bars  21  arranged on the floating table  20 .  
         [0016]     Since the plurality of glass substrates  1  are conveyed by being floated by air jets, vibration of the glass substrate  1  is minimized. Consequentially, the camera  10  obtains a clear image of the glass substrate  1 .  
         [0017]     At step S 20 , information on the particles P residing in a unit area is stored, wherein the information is obtained by scanning the glass substrate  1  in a longitudinal direction, i.e., the travel direction of the glass substrate  1 , while the glass substrate  1  passes by the camera  10 ; and the camera  10  is arranged over the travel path of the glass substrate and has a preset scan width.  
         [0018]     Referring to  FIG. 3 , the camera  10  is a line scan camera, which scans a unit area corresponding to the preset scan width. At a lower part of the camera  10  is installed a lens  11 , beside which is arranged an illumination  30 , e.g., a halogen lamp, which illuminates the area to be photographed.  
         [0019]     The camera  10  is arranged, while maintaining a desired distance from the glass substrate  1 , to move along a guide rail  40  which is installed inside a frame  41  positioned above the glass substrate  1  to be perpendicular to the travel path of the glass substrate  1 . Since the camera  10  is joined mechanically with a linear motor  50  which moves along the guide rail  40 , the camera  10  moves along the guide rail  40 , together with the illumination  30 , when the linear motor  50  is driven.  
         [0020]     Referring to  FIG. 4 , as the camera  10  scans a unit area of the glass substrate  1  conveyed below the camera  10  with a preset scan width, an image of the scanned unit area is sent to a controller  60  and information on the particles P, i.e., a number, sizes, positions, and the like, in the image of the scanned unit area is processed by an image processor  61  and stored.  
         [0021]     The information on the particles P in the unit area of the glass substrate  1  may be displayed outside through a display  62  so that the information can be understood easily from the outside.  
         [0022]     At step S 60 , from the information on the particles in the unit area of the glass substrate  1 , it is estimated whether the number of the particles P is equal to or larger than the preset number. And if the number of the particles P is equal to or larger than the preset number, at step S 90 , an alarm  63  raises an alarm to the outside.  
         [0023]     The alarm  63  may be a text or an image which gives an alarm on the display  62 , a speaker which sounds an alarm outside, a blinker, and the like. The alarm  63  may be installed in a place where the particles in a glass substrate  1  are inspected, a place for a former process, i.e., a washing process, or other places in order to influence the other processes by warning of an excessive generation of the particles P in the glass substrate  1 .  
         [0024]     At step S 60 , if the number of the particles P is less than the preset number, step S 30  is executed, wherein, while maintaining the desired distance from the glass substrate  1 , the camera  10  is moved a preset distance in a direction perpendicular to the travel path of the glass substrate  1 .  
         [0025]     At step S 30 , the camera  10  moves a preset distance along the guide rail  40  in a direction perpendicular to the travel path of the glass substrate  1 , together with the linear motor  50 , through an operation of the linear motor  50 . Accordingly, the camera  10  is positioned to scan a unit area neighboring the scanned unit area.  
         [0026]     When the camera  10  is positioned to scan the new unit area of a newly introduced glass substrate  1  which neighbors the scanned unit area, step S 40  is executed.  
         [0027]     At step S 40 , information on the particles P residing in the new unit area is stored, wherein the information is obtained by scanning the newly introduced glass substrate  1  by the camera which is moved a preset distance in a direction perpendicular to the travel path of the glass substrate  1 .  
         [0028]     The information on the particles P in the unit area of the new glass substrate  1  may be displayed outside through the display  62  so that the information on the particles P in the unit area of the glass substrate  1 , i.e., a number, sizes, positions, and the like, can be understood easily from the outside.  
         [0029]      FIG. 5  shows a data format of the result obtained by performing a scan of the unit area using the camera  10 , which includes a map  71  showing positions and distribution of the particles P obtained by scanning a unit area X 3 ; and a table  72  showing numbers of the particles P in the unit area X 3  classified by a particle size (S, M and L). Other than this, the data format can be displayed in various forms.  
         [0030]     The particle size is classified into 3 groups, wherein the size grows in order of S(small), M(medium) and L(large).  
         [0031]     At step S 70 , from the information on the particles P in the unit area of the new glass substrate  1 , it is estimated whether the number of the particles P is equal to or larger than the preset number. If the number of the particles P is equal to or larger than the preset number, at step S 90 , the alarm  63  raises an alarm to the outside. And if not, the following step S 51  is executed.  
         [0032]     At step S 51 , it is estimated whether a sum of the respective unit areas which were scanned during repetition of steps S 30  and S 40  is within an allowed limit of the area of one glass substrate  1 . If the sum is within the allowed limit, by summing up the information on the particles P residing in the respective scanned unit areas, information on the particles P in the entire glass substrate  1  is obtained and stored. This data may be displayed outside as sampling information on the particles P in the entire area of the glass substrate  1 .  
         [0033]     The data displayed as information on the particles P in the entire area of the glass substrate  1  is statistical data on the plurality of glass substrates  1  scanned by the camera  10  until the sum of the scanned unit areas reaches the allowed limit of the area of a glass substrate  1 .  
         [0034]     At step S 51 , whether the sum of the respective unit areas of the glass substrates  1  is within the allowed limit of the area of a glass substrate  1  or not is estimated by following ways: obtaining a scanning number of the camera  10  by comparing the width of the glass substrate  1  with the scan width of the camera  10 ; and figuring out when the sum of the respective unit areas of the glass substrates  1  approaches most closely to the area of a glass substrate  1 .  
         [0035]     At step S 80 , it is estimated whether the number of the particles P is equal to or larger than the preset number by using the information on the particles P in the entire area of the glass substrate  1  which is obtained at step S 50 . If the number of the particles P is equal to or larger than the preset number, the alarm  63  raises an alarm to the outside at step S 90 . And if not, the above-described procedure is terminated.  
         [0036]     Referring to  FIG. 4 , information on the particles P in the respective unit areas of the glass substrates  1  and that in the entire area of the glass substrate  1  may be sent to other process servers  2  and displayed outside so that a succeeding measures can be taken to reduce generation of particles P in the glass substrate  1 .  
         [0037]     A method for measuring particles in a glass substrate described-above operates in a following sequence.  
         [0038]     At step S 10 , a plurality of glass substrates  1  entering the clean room after being subjected to a washing process is floated by air jets and conveyed sequentially at regular intervals. When a sensor (not shown) detects a glass substrate  1  entering the clean room, the camera  10  arranged over the travel path of the glass substrate  1  scans a unit area in a longitudinal direction, i.e., the direction of travel path, with a regular scan width.  
         [0039]     At step S 20 , information on the particles P, i.e., a number, sizes, positions, and the like, is obtained and stored from the unit area of glass substrate  1  scanned by camera  10 . And this data may be displayed outside through the display  62 .  
         [0040]     At step S 60 , it is estimated whether the number of the particles P is equal to or larger than the preset number from the information on the particles P in the scanned unit area of the glass substrate  1 . If the answer is “Yes”, i.e., if the number of the particles P is equal to or larger than the preset number, the alarm  63  raises an alarm to the outside at step S 90 . And if the answer is “No”, i.e., if the number of the particles P is less than the preset number, step S 30  is executed to move the camera  10  in a direction perpendicular to the travel path of the glass substrate  1 . That is, when the linear motor  50  is driven, the camera  10 , together with the linear motor  50 , is moved along the guide rail  40  in a direction perpendicular to the travel path of the glass substrate  1  such that it will be positioned to scan a unit area neighboring the scanned unit area.  
         [0041]     At step S 40 , information on the particles P residing in the new unit area which is obtained by scanning the newly introduced glass substrate  1  is stored. And the data may be displayed outside through the display  62 .  
         [0042]     At step S 70 , from the information on the particles P in the unit area of the new glass substrate  1 , it is estimated whether the number of the particles P is equal to or larger than the preset number. If the number of the particles P is equal to or larger than the preset number, the alarm  63  raises an alarm to outside at step S 90 . And if not, the following step S 51  is executed, wherein it is estimated whether the sum of the respective unit areas which were scanned during repetition of steps S 30  and S 40  is within the allowed limit of the area of a glass substrate  1 .  
         [0043]     At step S 51 , if the answer is “No”, i.e., if the sum is not within the allowed limit, steps S 30  and S 40  are repeated again. And if the answer is “Yes”, i.e., if the sum is within the allowed limit, at step S 50 , information on the particles P in the entire glass substrate  1  is obtained and stored by summing up information on the particles P residing in the respective scanned unit areas.  
         [0044]     The sampling data displayed as information on the particles P in the entire area of the glass substrate  1  is used as statistical data of the plurality of glass substrates  1  scanned by the camera  10  until the sum of the scanned unit areas falls within the allowed limit of the area of a glass substrate  1 .  
         [0045]     When the data is displayed outside as information on the particles P in the entire area of the glass substrate  1  scanned by the camera  10 , at step S 80 , it is estimated whether the number of the particles P is equal to or larger than the preset number. At step S 90 , if the number is equal to or larger than the preset number, the alarm  63  raises an alarm to outside.  
         [0046]     The information on the particles P in the respective unit areas of the glass substrates  1  and that in the entire area of the glass substrate  1  may be sent to other process servers  2 , e.g., the washing process, and displayed outside so that a succeeding measures can be taken to reduce generation of particles P in the glass substrate  1 .  
         [0047]     As described above, by obtaining and storing information on the particles P in the respective unit areas and in the entire area of the glass substrates  1  scanned by the camera  10 , and displaying the information as a statistic, a method for measuring particles in a glass substrate in accordance with the present invention is capable of providing sampling information on the particles in a glass substrate without interruption in the process line; utilizing a clean room space efficiently; and performing an inspection of a large-sized glass substrate.  
         [0048]     While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.