Patent Publication Number: US-2022214623-A1

Title: Calibration system and drawing device

Description:
TECHNICAL FIELD 
     The present invention relates to calibration systems for calibrating an exposure light beam for drawing a pattern on a substrate and to drawing devices. 
     BACKGROUND ART 
     In recent years, the amount of electronics used in transportation machines such as automobiles and aircraft has been steadily increasing. Along with this, the number of wire harnesses used for power supply and/or signal transmission and reception with respect to the electronics is also increasing. On the other hand, weight reduction and space saving are required in the transportation machines, and an increase in weight and space occupation due to the increase of the wire harnesses is therefore becoming a problem. 
     In view of these problems, investigations have been made to replace the wire harnesses used in transportation machines with long sheet-like flexible printed circuits (FPCs). 
     As a technique for forming patterns on a long sheet-like substrate, for example, PTL 1 discloses a substrate processing apparatus provided with: a support member having a support surface for supporting a long sheet-like substrate, the support member being provided with reference marks at a plurality of positions on the support surface with respect to the width direction intersecting with the longitudinal direction of the substrate; a conveyance device for moving the substrate supported on the support member in the longitudinal direction; and a drawing device including a plurality of drawing units for scanning ranges smaller than the dimension in the width direction of the substrate while projecting beam spot light onto the support surface or the substrate supported on the support surface, the plurality of drawing units being capable of drawing predetermined patterns along drawing lines obtained from the scan. The plurality of drawing units are arranged in the width direction of the substrate such that the patterns drawn on the substrate by the respective drawing lines of the plurality of drawing units are joined together in the width direction of the substrate in association with the movement of the substrate in the longitudinal direction. 
     NPTL 1 discloses a technique of performing alignment measurement, overlay exposure and workpiece replacement in parallel, in order to perform a process while continuously conveying the film by a roll-to-roll method without stopping the film from being conveyed. 
     PRIOR ART DOCUMENTS 
     Patent Literature 
     
         
         PTL 1: WO2015/152217 
       
    
     Non-Patent Literature 
     NPTL 1: Yoshiaki Kito, et al., “Direct Imaging Exposure Equipment with High Overlay Accuracy for Flexible Substrate in Roll-to-Roll Method,” Journal of the Institute of Image Information and Television Engineers, Vol. 71, No. 10, pp. J230-J235 (2017), the Institute of Image Information and Television Engineers, Sep. 8, 2017 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     Incidentally, in equipment requiring a high level of safety, such as automobiles and aircraft, traceability is required to ensure the high reliability of each component constituting the equipment. For this reason, regarding the patterned substrate, in the step of patterning the substrate, it is necessary to periodically perform calibration for checking positional precision of exposure beam irradiation and the like, and to store the calibration data. 
     Regarding calibration, PTL 1 discloses a technique in which reference patterns formed on an outer periphery of a rotating drum is irradiated with drawing beams and adjustment information (calibration information) corresponding to an arrangement condition or a mutual arrangement error of the drawing lines by the drawing beams is determined based on the reflected light of the drawing beams. PTL 1 requires, when performing calibration, the reference patterns formed on the outer periphery of the rotating drum to be irradiated with the beams, and thus, calibration needs to be performed without setting the substrate, or a substrate with sufficient translucency to allow a beam to pass therethrough needs to be re-set (see paragraph 0147 of citation 1). 
     However, for example, in order to replace the wire harnesses used in an automobile with FPCs, it is necessary to form a continuous wiring pattern of several meters in length (e.g., 6 m or more) on a substrate. In the case of forming a continuous pattern on a long substrate as described above, it is very labor-intensive to remove the substrate and/or to re-set a substrate for calibration each time calibration is performed, and it is also impractical because there is a risk of deterioration in the alignment precision. In short, in the case of forming a continuous pattern on a long substrate, it is very difficult to perform calibration as needed with the technique disclosed in PTL 1. 
     The present invention has been made in view of the above, and an object of the present invention is to provide, in the case of continuously forming a pattern on a long sheet-like substrate, a calibration system and a drawing device that can perform, as needed, calibration of an exposure beam radiated onto the substrate. 
     Means for Solving the Problems 
     In order to solve the above-described problems, the calibration system, which is an aspect of the present invention, is a calibration system for performing calibration in a drawing device. The drawing device includes at least one exposure head that emits a beam for exposure toward an exposure surface of the substrate. The substrate has a long-sheet shape and is conveyed in a longitudinal direction by being supported on part of an outer periphery of a conveying drum having a cylindrical shape. The calibration system is provided with: an optical system that is provided insertably into and removably from an optical path of a beam that is emitted from the exposure head and enters the exposure surface, the optical system guiding at least part of the beam in a direction different from that of the optical path when the optical system is inserted into the optical path; a movement mechanism that inserts and removes the optical system into and from the optical path; and an optical sensor having a light-receiving surface for receiving at least part of the beam that is guided by the optical system when the optical system is inserted into the optical path, the optical sensor outputting a detection signal by detecting an irradiation position and an irradiation intensity at the light-receiving surface of at least part of the beam that has entered the light-receiving surface. 
     In the above-described calibration system, the exposure surface when the optical system is removed from the optical path and the light-receiving surface when the optical system is inserted into the optical path may be conjugated. 
     In the above-described calibration system, the length of the optical path of the beam from the exposure head to the exposure surface when the optical system is removed from the optical path may be equal to the length of the optical path of the beam from the exposure head to the light-receiving surface when the optical system is inserted into the optical path. 
     In the above-described calibration system, the optical system and the optical sensor may be provided as units with positions fixed relative to each other, and the movement mechanism may insert and remove the units into and from the optical path. 
     In the above-described calibration system, the position of the optical sensor is fixed, and there may be further provided: a second optical system that further guides at least part of the beam, guided by the optical system in a direction different from that of the optical path, in a direction toward the light-receiving surface of the optical sensor; and a third optical system that allows at least part of the beam guided by the second optical system to be imaged on the light-receiving surface. 
     In the above-described calibration system, there may be further provided: a control part that generates, based on the detection signal output from the optical sensor, data representing an irradiation position and an irradiation intensity at the light-receiving surface of at least part of the beam emitted from the exposure head; and a storage part that stores the data representing the irradiation position and the irradiation intensity as calibration data. 
     In the above-described calibration system, the storage part may further store reference data representing a reference irradiation position and a reference irradiation intensity at the light-receiving surface corresponding to a predetermined irradiation position and a predetermined irradiation intensity of the beam at the exposure surface, and the control part may include a determination part that determines, based on the calibration data and the reference data, whether an irradiation position and an irradiation intensity of a beam that has entered the light-receiving surface fall within ranges of predetermined reference values. 
     In the above-described calibration system, the control part may generate, based on the determination result by the determination part, correction value data for correcting at least either the irradiation position or the irradiation intensity of the beam emitted from the exposure head if at least either the irradiation position or the irradiation intensity of the beam that has entered the light-receiving surface fails to fall within the range of the reference value, and the storage part may further store the correction value data. 
     In the above-described calibration system, the exposure head may include: a light source that outputs laser light; a beam-shaping optical system that generates a beam by shaping the laser light into a beam shape; a polygon mirror that causes the beam generated by the beam-shaping optical system to scan; and a drive part that rotates the polygon mirror, and the control part may correct at least either the irradiation intensity or the irradiation position of the beam emitted from the exposure head by controlling at least either the output of the light source or operation of the drive part based on the correction value data. 
     In the above-described calibration system, there may be further provided an adjustment mechanism that adjusts the distance between the exposure head and the conveying drum, and the control part may acquire, based on the detection signal representing the irradiation position of the beam output from the optical sensor, the diameter of the beam at the light-receiving surface and control the adjustment mechanism based on the diameter of the beam. 
     A drawing device, which is another aspect of the present invention, is provided with: a conveying drum that has a cylindrical shape, the conveying drum supporting a long sheet-like substrate on part of an outer periphery and conveying the substrate by rotating about a central shaft of the cylinder; at least one exposure head that emits a beam for exposure toward an exposure surface of the substrate; and at least one calibration system that performs calibration of the at least one exposure head. The calibration system includes: an optical system that is provided insertably into and removably from an optical path of the beam that is emitted from the exposure head and enters the exposure surface, the optical system guiding at least part of the beam in a direction different from that of the optical path when the optical system is inserted into the optical path; a movement mechanism that inserts and removes the optical system into and from the optical path; and an optical sensor having a light-receiving surface for receiving at least part of the beam that is guided by the optical system when the optical system is inserted into the optical path, the optical sensor outputting a detection signal by detecting an irradiation position and an irradiation intensity at the light-receiving surface of at least part of the beam that has entered the light-receiving surface. 
     Effect of the Invention 
     According to the present invention, by inserting, during calibration, the optical system into the optical path of a beam that is emitted from the exposure head and enters the substrate, the beam is guided in a direction different from that of the optical path and enters the light-receiving surface of the optical sensor, calibration can therefore be performed while the substrate remains set on the conveying drum. Therefore, in the case of continuously forming a pattern on a long sheet-like substrate, calibration can be performed as needed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing a schematic configuration of a drawing device including a calibration system according to a first embodiment of the present invention. 
         FIG. 2  is a plan view of the drawing device shown in  FIG. 1 . 
         FIG. 3  is a schematic diagram showing a schematic configuration of the inside of an exposure head. 
         FIG. 4  is a schematic diagram of the exposure head shown in  FIG. 1  as seen from the substrate side. 
         FIG. 5  is a schematic diagram illustrating a substrate on which a pattern is formed. 
         FIG. 6  is an enlarged schematic diagram showing a neighborhood of a calibration unit shown in  FIG. 1 . 
         FIG. 7  is a schematic diagram of a sensor unit shown in  FIG. 6  as seen from the light-receiving surface side. 
         FIG. 8  is a block diagram showing a schematic configuration of a controller shown in  FIG. 1 . 
         FIG. 9  is a flowchart illustrating operations at the time of calibration of the drawing device shown in  FIG. 1 . 
         FIG. 10  is a schematic diagram showing a schematic configuration of a drawing device including a calibration system according to a second embodiment of the present invention. 
         FIG. 11  is an enlarged schematic diagram showing a neighborhood of a calibration unit shown in  FIG. 10 . 
     
    
    
     EMBODIMENTS OF THE INVENTION 
     Hereinafter, a calibration system and a drawing device according to embodiments of the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited by these embodiments. In the description of each drawing, the same portions are denoted by the same reference numbers. 
     The drawings referred to in the following description are merely schematic representations of shape, size, and positional relationship to the extent that the subject matter of the present invention may be understood. In other words, the present invention is not limited only to the shapes, sizes, and positional relationships exemplified in the respective figures. In addition, the drawings may also include, among themselves, portions having different dimensional relationships and ratios from each other. 
     First Embodiment 
       FIG. 1  is a schematic diagram showing a schematic configuration of a drawing device including a calibration system according to a first embodiment of the present invention.  FIG. 2  is a plan view of the drawing device. As shown in  FIGS. 1 and 2 , the drawing device  1  according to the present embodiment includes a conveying system  3  for conveying a substrate  2  having a long-sheet shape, a drawing unit  4  for forming a pattern by irradiating the substrate  2  with a beam L for exposure, and a controller  5  for controlling the operation of the conveying system  3  and the drawing unit  4 . In the following, the conveying direction of the substrate  2  will be referred to as the x direction, the width direction of the substrate  2  will be referred to as the y direction, and the vertical direction will be referred to as the z direction (positive in the downward direction). 
     In the present embodiment, a flexible printed circuit (FPC) is used as the substrate  2  to be processed. The FPC is a flexible circuit substrate in which a metal foil such as copper is bonded to a base film made of an insulating resin such as polyimide. The substrate  2  is, for example, a strip-shaped FPC of several meters to several tens of meters in length, and the substrate is unwound from a state of being wound in a roll on an unwinding reel  31  and is wound on a take-up reel  32  after a pattern is formed thereon by the drawing unit  4  while being conveyed by the conveying system  3 . Thus, this method of conveying in which the strip-shaped workpiece is unwound from a roll and wound around a roll after application of predetermined processing is referred to as a “roll-to-roll” method. 
     In the conveying system  3 , a rotary shaft  31   a  for rotatably supporting the unwinding reel  31 , a rotary shaft  32   a  for rotatably supporting the take-up reel  32 , a conveying drum  33 , tension pulleys  34 ,  35  provided respectively on the upstream side (left side in  FIG. 1 ) and the downstream side (right side in  FIG. 1 ) of the conveying drum  33 , and a plurality of guide rollers  36 ,  37  are provided. 
     The conveying drum  33  generally has a cylindrical shape and is supported by a rotary shaft  33   a  which rotates by the rotational driving force supplied from a drive source. The conveying drum  33  supports the substrate  2  in a region of substantially the upper half of the outer periphery  33   b  thereof, and conveys the substrate  2  as the conveying drum rotates. Further, the conveying drum  33  is provided with an encoder  33   c  for measuring the amount of rotation of the conveying drum  33 . 
     The two tension pulleys  34 ,  35  are respectively rotatably supported on rotary shafts  34   a ,  35   a  which are movable in the vertical direction, and are located below the conveying drum  33 . A tension adjusting mechanism for biasing the rotary shaft  34   a ,  35   a  downward is coupled to each rotary shaft  34   a ,  35   a . The substrate  2  wound around the conveying drum  33  can be conveyed with a predetermined tension applied thereon by biasing the tension pulleys  34 ,  35  downward via the rotary shafts  34   a ,  35   a  by means of the tension adjusting mechanism. 
     Each guide roller  36  is rotatably supported on a rotary shaft  36   a  and guides the substrate  2  unwound from the unwinding reel  31  to the upstream-side tension pulley  34 . Each guide roller  37  is rotatably supported on a rotary shaft  37   a  and guides the substrate  2  that has been applied with pattern-forming processing from the downstream-side tension pulley  35  to the take-up reel  32 . 
     The configuration of the conveying system  3  is not limited to the configurations shown in  FIGS. 1 and 2 , as long as the substrate  2  is conveyed in the roll-to-roll method and the pattern-forming processing can be applied to the substrate  2  supported on the outer periphery  33   b  of the conveying drum  33 . Further, a unit (a pre-processing unit, a post-processing unit, etc.) may be provided for performing different processing between unwinding of the substrate  2  from the unwinding reel  31  and reaching thereof to the conveying drum  33 , or between removal of the substrate  2  from the conveying drum  33  and winding thereof on the take-up reel  32 . Typically, an edge position control (EPC) device is provided which detects the edge position of the substrate  2  and finely moves the unwinding device or the take-up device in the conveying system  3  in order to prevent meandering during conveying of the substrate. 
     In the drawing unit  4 , a plurality of exposure heads  41  that emit beams L for exposure toward the substrate  2 , and calibration units  43  and movement mechanisms  44 , which are used when calibrating the beams L, are provided. In the present embodiment, the calibration unit  43  and the movement mechanism  44 , together with the controller  5  described below, constitute the calibration system. 
     The exposure head  41  directly draws a pattern, such as a circuit or a wiring, on the substrate  2  by radiating the beam L onto the substrate  2  supported on the conveying drum  33 .  FIG. 3  is a schematic diagram showing a schematic configuration of the inside of an exposure head. 
     As shown in  FIG. 3 , a laser light source  411  for outputting laser light, a beam-shaping optical system  412 , a reflecting mirror  413 , a polygon mirror  414 , and an imaging optical system  415  are provided inside the exposure head  41 . Among which, the polygon mirror  414  is provided with a drive device for rotating the polygon mirror  414  about a rotary shaft  414   a.    
     The beam-shaping optical system  412  includes an optical element, such as a collimator lens, a cylindrical lens, a light amount adjusting filter, and a polarizing filter, and shapes the laser light output from the laser light source  411  into the beam L having a spot-shaped beam shape. The reflecting mirror  413  reflects the beam L shaped by the beam-shaping optical system  412  in the direction of the polygon mirror  414 . The polygon mirror  414  rotates around the rotary shaft  414   a  and reflects the beam L incident from the direction of the reflecting mirror  413  in a plurality of directions in the plane orthogonal to the rotary shaft  414   a . The imaging optical system  415  includes an optical element, such as an fθ lens or a telecentric fθ lens, and causes the beam L reflected by the polygon mirror  414  to be imaged on an exposure surface P 1  of the substrate  2  supported on the outer periphery of the conveying drum  33 . In such exposure head  41 , the beam L emitted from the exposure head  41  can be caused to scan one-dimensionally in a predetermined scan range SR by controlling the rotation of the polygon mirror  414 . 
     The configuration of the exposure head  41  is not limited to the configuration illustrated in  FIG. 3 , as long as the beam L can be imaged on the exposure surface P 1  and can be scanned one-dimensionally thereon. For example, the emitting direction of the beam L may be changed by arranging a reflecting mirror between the polygon mirror  414  and the imaging optical system  415 . 
       FIG. 4  is a plan view of the plurality of exposure heads  41  provided in the drawing unit  4  as seen from the substrate  2  side. Although four exposure heads  41  are shown in  FIG. 4 , the number of exposure heads  41  is not limited thereto. The number of exposure heads  41  may be one or more, and can be appropriately configured according to the width of the substrate  2 , the scan range SR (see  FIG. 3 ) and the beam power of the exposure head  41 , and the like. 
     Each exposure head  41  is mounted to a support mechanism provided inside the drawing unit  4  via an adjustment stage  42 . The adjustment stage  42  is provided for manually fine-adjusting the position of the exposure head  41  in the x and y directions as well as the angle with respect to the vertical direction. These exposure heads  41  are arranged such that the edges of the scan ranges SR of the beams L emitted from beam emitting ports  41   a  slightly overlap each other or are adjacent to each other without any space therebetween, between the beams L that scan the adjacent regions in the width direction (y direction) of the substrate  2 . Thereby, scanning can be performed without any space in the width direction of the substrate  2  by means of the plurality of beams L. In addition, the distance of each exposure head  41  from the conveying drum  33  is adjusted such that the beam L is focused on the exposure surface of the substrate  2 . 
       FIG. 5  is a schematic diagram illustrating the substrate  2  on which a pattern is formed by the drawing unit  4 . The two-dimensional exposure pattern  21  is formed on the substrate  2  by conveying the substrate  2  by means of the conveying drum  33  while the beam L emitted from each exposure head  41  shown in  FIG. 4  is scanned in the width direction of the substrate  2 . In this way, a continuous exposure pattern  21  can be formed on the long substrate  2 , as shown in  FIG. 5 , by conveying the substrate  2  while the direct drawing is performed by the beam L. 
     In the drawing unit  4 , a region to be exposed by each exposure head  41  may be preset with respect to the substrate  2 . Therefore, an identification mark (ID)  22   a  to  22   d  for identifying an individual product and/or pattern may be drawn in the exposure region of each exposure head  41 . A high level of traceability can be ensured by managing the identification marks  22   a  to  22   d  in association with data such as a lot number, a drawing device number, an exposure head number, and/or a date and time of exposure. 
       FIG. 6  is an enlarged schematic diagram showing a neighborhood of the calibration unit  43  shown in  FIG. 1 , and shows the arrangement at the time of calibration. 
     The movement mechanism  44  inserts and removes the calibration unit  43  into and from an optical path LP of the beam L that is emitted from the exposure head  41  and enters the exposure surface of the substrate  2 . The movement mechanism  44  is, for example, a single-axis actuator, and inserts the calibration unit  43  into the optical path LP at the start of calibration (see  FIG. 6 ) and removes the calibration unit  43  from the optical path LP when the calibration is completed (see  FIG. 1 ). Such calibration unit  43  and movement mechanism  44  are provided for each exposure head  41 . 
     The configuration of the movement mechanism  44  is not particularly limited, as long as it can move the calibration unit  43  with high precision. In addition, the calibration unit  43  is moved along the direction of conveyance of the substrate  2  (the tangential direction of the outer periphery of the conveying drum  33 ) at the irradiation position of the beam L in  FIGS. 1 and 6 ; however, the direction of movement is not limited thereto. For example, the calibration unit  43  may be moved along the width direction (y direction) of the substrate  2 . 
     A reflecting mirror  431  and a sensor unit  432  are provided in the calibration unit  43 . The relative positions of the reflecting mirror  431  and the sensor unit  432  are fixed. The reflecting mirror  431  is an optical system that is arranged on the optical path LP when the calibration unit  43  is inserted into the optical path LP and guides the beam L in a direction different from that of the optical path LP. 
     The sensor unit  432  has a two-dimensional light-receiving surface and is provided at a position where the beam L reflected by the reflecting mirror  431  can enter the light-receiving surface. The length of an optical path from the position of the reflecting mirror  431  arranged in the optical path LP to the exposure surface of the substrate  2  at the time of calibration is equal to the length of an optical path from the position of the reflecting mirror  431  to the light-receiving surface of the sensor unit  432  at the time of calibration, and the light-receiving surface of the sensor unit  432  and the exposure surface of the substrate  2  to be exposed by the beam L are conjugated. In other words, at the light-receiving surface of the sensor unit  432  when the reflecting mirror  431  is inserted into the optical path LP, the same image of the beam L can be obtained as that at the exposure surface of the substrate  2  when the reflecting mirror  431  is not inserted into the optical path LP. 
       FIG. 7  is a schematic diagram of the sensor unit  432  as seen from the light-receiving surface side. As shown in  FIG. 7 , the sensor unit  432  includes a sensor substrate  433 , and a position detecting element (PSD)  434  and a light intensity detecting element  436 , which are optical sensors mounted on the sensor substrate  433 . A circuit is formed on the sensor substrate  433  for processing the signals output from the position detecting element  434  and the light intensity detecting element  436 . 
     The position detecting element  434  has a two-dimensional light-receiving surface  435  for receiving the beam L, and outputs a detection signal representing an irradiation position of the beam L that has entered the light-receiving surface  435 . As shown in  FIG. 7 , in the present embodiment, two position detecting elements  434  are arranged on the sensor substrate  433 . The positions of these position detecting elements  434  are set so that the center line of each position detecting element  434  overlaps the line of the edge of the scan range SR. In this way, a slight deviation of the irradiation position of the beam L can be detected by providing two position detecting elements  434  with respect to a single sensor unit  432 . 
     The light intensity detecting element  436  is, for example, a photodiode (PD), and outputs a detection signal representing the irradiation intensity of the beam L that has entered the light-receiving surface. 
     It should be noted that a single type of optical sensor may be used instead of the position detecting element and the light intensity detecting element if it can detect both the position and intensity of the beam L that has entered the light-receiving surface with high precision. In this case, such optical sensor may preferably be arranged at the positions (two locations) of the position detecting elements  434 . 
       FIG. 8  is a block diagram showing a schematic configuration of the controller  5 . The controller  5  is a device for comprehensively controlling the operation of each component of the drawing device  1 , and includes an external interface  51 , a storage part  52 , and a control part  53 . 
     The external interface  51  is an interface for connecting various external devices to the controller  5 . Examples of the external devices connectable to the controller  5  include the exposure head  41 , the encoder  33   c , a substrate conveying drive device  61  for driving the conveying system  3 , a calibration-use drive device  62  for driving the movement mechanism  44  of the calibration unit  43 , an input device  63  such as a keyboard or a mouse, a display device  64  such as a liquid crystal monitor, and a data reading-in device  65  for reading in pattern data or the like into the controller  5 . 
     The storage part  52  is configured by using a computer readable storage medium such as a disk drive and/or a semiconductor memory (e.g., a ROM or RAM). The storage part  52  stores, in addition to an operating system program and a driver program, a program for causing the controller  5  to execute a predetermined operation, various types of data and setting information used during execution of the program, and the like. 
     Specifically, the storage part  52  includes a program storage part  521 , a pattern data storage part  522 , a reference data storage part  523 , a calibration data storage part  524 , and a correction data storage part  525 . The program storage part  521  stores the various types of programs described above. The pattern data storage part  522  stores data representing patterns to be drawn by the drawing unit  4 . The reference data storage part  523  stores reference data (reference values) of the irradiation positions and irradiation intensities of the beams L. Here, the reference data refers to data representing: an irradiation position (hereinafter also referred to as a reference irradiation position) in the light-receiving surface  435  of the position detecting element  434  corresponding to a predetermined irradiation position of the beam L in the exposure surface of the substrate  2 ; and an irradiation intensity (hereinafter also referred to as a reference irradiation intensity) at the light intensity detecting element  436  corresponding to a predetermined irradiation intensity of the beam L at the exposure surface of the substrate  2 . The calibration data storage part  524  stores calibration data of the beam L to be exposed on the substrate  2 , in other words, it stores data representing the irradiation position of the beam L in the light-receiving surface  435  of the position detecting element  434  and the irradiation intensity of the beam L that has entered the light intensity detecting element  436 . The correction data storage part  525  stores correction data for adjusting the exposure head  41  based on the calibration data. 
     The control part  53  is configured by using hardware such as a central processing unit (CPU), and reads in the programs stored in the program storage part  521  to perform data transfer and instruction to each component of the controller  5  and the drawing device  1 , and comprehensively controls the operation of the drawing device  1  to execute the pattern-forming processing on the substrate  2 . Further, by reading in the calibration program stored in the program storage part  521 , the control part  53  periodically performs calibration of the exposure head  41 , stores the calibration data, and adjusts the exposure head  41  based on the calibration data. 
     Specifically, functional parts implemented by the control part  53  executing the above-described program include a drawing control part  531 , a calibration control part  532 , a determination part  533 , and a correction part  534 . 
     The drawing control part  531  reads out the pattern data from the pattern data storage part  522 , generates control data such as the power and scanning of the beam L by each exposure head  41  and the conveying speed of the substrate  2  by the conveying system  3 , and outputs the control data to the exposure head  41  and the substrate conveying drive device  61 . Thereby, the substrate  2  is conveyed at a predetermined speed by the conveying system  3 , and a predetermined exposure region of the substrate  2  is irradiated and scanned in the width direction with the beam L emitted from each exposure head  41 . In this manner, a two-dimensional pattern is continuously formed on the substrate  2 . 
     The calibration control part  532  performs control for calibrating the beam L emitted from the exposure head  41  and generates data (calibration data) representing the measured values (calibration values) of the irradiation position of the beam L in the light-receiving surface  435  of the position detecting element  434  and the irradiation intensity at the light intensity detecting element  436 . 
     The determination part  533  determines whether the calibration values are within the reference values based on the reference data stored in the reference data storage part  523  and the calibration data. 
     The correction part  534  generates correction data for correcting the irradiation position and the irradiation intensity of the beam L if the calibration values fail to fall within the reference values, and controls each component based on the correction data. 
     It should be noted that the controller  5  may be configured by a single piece of hardware or may be configured by combining a plurality of pieces of hardware. 
     Next, a calibration method according to a first embodiment of the present invention will be described.  FIG. 9  is a flowchart illustrating the operation at the time of calibration of the drawing device  1 . 
     First, in step S 10 , the controller  5  causes each exposure head  41  to stop irradiating the substrate  2  with the beam L. 
     In the subsequent step S 11 , the controller  5  causes the conveying system  3  to stop conveying the substrate  2 . 
     In the subsequent step S 12 , the controller  5  controls the calibration-use drive device  62  to drive the movement mechanism  44  so as to insert the calibration unit  43  into the optical path LP (see  FIG. 6 ). 
     In the subsequent step S 13 , the controller  5  causes each exposure head  41  to emit the beam L. The beam L emitted from the exposure head  41  is reflected by the reflecting mirror  431  in the calibration unit  43 , and enters the position detecting element  434  and the light intensity detecting element  436  in the sensor unit  432 . Thereby, each position detecting element  434  outputs a detection signal representing the irradiation position of the beam L on the light-receiving surface  435 , while the light intensity detecting element  436  outputs a detection signal representing the irradiation intensity of the beam L. 
     In the subsequent step S 14 , the calibration control part  532  of the controller  5  generates, based on the detection signals output from the position detecting element  434  and the light intensity detecting element  436 , data (calibration data) representing the measured values of the irradiation position and the irradiation intensity of the beam L that has entered the light-receiving surface  435  and stores such data in the calibration data storage part  524 . 
     In the subsequent step S 15 , the determination part  533  compares the calibration data generated in step S 14  with the reference data stored in the reference data storage part  523  in order to determine whether the irradiation position and the irradiation intensity of the beam L emitted from each exposure head  41  are within the reference values. Specifically, the determination part  533  calculates the difference (Δx, Δy) of the measured value of the irradiation position with respect to the reference irradiation position of the beam L and the difference of the measured value of the irradiation intensity with respect to the reference irradiation intensity. Then, a determination is made as to whether the difference of the irradiation position (Δx, Δy) and the difference of the irradiation intensity are equal to or less than predetermined thresholds. 
     If the irradiation position and the irradiation intensity of the beam L are within the reference values (step S 15 : Yes), the operation proceeds to step S 17 . 
     On the other hand, if the irradiation position and the irradiation intensity of the beam L exceed the reference values (step S 15 : No), the correction part  534  generates correction data for correcting the position of each exposure head  41  and the power value of the beam L, and stores such correction data in the correction data storage part  525  (step S 16 ). At this time, the correction part  534  may display the correction data on the display device  64 . Specifically, the correction part  534  corrects the parameter of the output start position (the value of θ at the time of starting the output of the beam L) based on the difference Δx in order to adjust the drawing start point that is set using the signal (see Δθ in  FIG. 6 ) of the encoder  33   c  in the conveying drum  33 . Further, the correction part  534  corrects the parameter of the output start position (the initial position of the polygon mirror at the time of starting the output of the beam L) based on the difference Δy in order to adjust the drawing start point serving as a reference of the beam L emitted via the polygon mirror  414  (see  FIG. 3 ). Further, regarding the irradiation intensity, the correction part  534  corrects the output parameter for each exposure head  41  used in the drawing control part  531 . 
     In the subsequent step S 17 , the controller  5  controls the calibration-use drive device  62  to drive the movement mechanism  44  so as to remove the calibration unit  43  from the optical path LP (see  FIG. 1 ). Thereby, the calibration operation in the drawing device  1  ends. When the drawing operation is restarted after completion of the calibration, each component operates based on the parameters corrected in step S 16 , and the drawing with respect to the substrate  2  can be performed with the corrected irradiation position and irradiation intensity of the beam. 
     As described above, according to the first embodiment of the present invention, since the beam L emitted from each exposure head  41  is scanned in the width direction as the substrate  2  is directly irradiated with the beam L while the substrate  2  is conveyed by the conveying drum  33 , a two-dimensional exposure pattern can therefore be continuously formed without interruption on the substrate  2 . Therefore, a continuous pattern can be efficiently formed on a long substrate ranging from several meters to several tens of meters in length, and an improvement in throughput can be achieved. 
     Further, according to the first embodiment of the present invention, a high level of traceability can be ensured at the pattern or wiring level by drawing an identification mark in the exposure region of each exposure head  41  with such exposure head  41 . 
     Further, according to the first embodiment of the present invention, since a light source is provided in each exposure head  41 , pattern-forming can be performed with sufficient irradiation intensity. 
     Further, according to the first embodiment of the present invention, by inserting, during calibration, the calibration unit  43  into the optical path LP of the beam L emitted from the exposure head  41 , high-precision calibration can therefore be performed while the substrate  2  remains set on the conveying drum  33 . Therefore, in the case of forming a continuous pattern on a long substrate, calibration can be performed, as needed. 
     Now, in the above-described first embodiment, the determination is made as to whether the measured value acquired in the calibration falls within the range of the reference value, and various types of processing for performing correction are executed if the measured value fails to fall within the range of the reference value. However, it may be sufficient to perform calibration and simply store the calibration data. Further, it may also be sufficient to store the determination result of the measured values acquired in the calibration, and/or the correction data based on the determination result. 
     Further, in the above-described first embodiment, the position and the inclination of the exposure head  41  are manually fine-adjusted by means of the adjustment stage  42 , but an electrically controllable adjustment stage may be provided instead of the adjustment stage  42 , and the position and the inclination of the exposure head  41  may be automatically adjusted based on the result of the calibration. 
     First Variation 
     In the above-described first embodiment, a deviation in the irradiation position of the beam L is detected based on the detection signal output from the position detecting element  434 ; however, a focal spot deviation may be detected. Specifically, a spot diameter of the beam L may be acquired by extracting the irradiation range of the beam L in the light-receiving surface  435  based on the detection signal output from position detecting element  434 . Then, the focal spot deviation is detected by comparing the acquired spot diameter with a spot diameter serving as a reference pre-stored in the reference data storage part  523 . 
     In this case, an adjustment mechanism may be provided for adjusting the distance between each exposure head  41  and the conveying drum  33 , and such distance may be adjusted based on the detected focal spot deviation. This enables the beam L to be focused with high precision on the light-receiving surface  435  of the position detecting element  434 , i.e., the exposure surface of the substrate  2 . 
     Further, a spot shape of the beam L in the light-receiving surface  435  may be acquired by extracting the irradiation range of the beam L in the light-receiving surface  435  based on the detection signal output from the position detecting element  434 . In this case, the inclination of the exposure head  41  (i.e., the angle between the exposure surface of the substrate  2  and the beam L) may be corrected based on the acquired spot shape. 
     Second Variation 
     In the above-described first embodiment, the calibration unit  43  is provided with the reflecting mirror  431 ; however, a beam splitter (half mirror) may be used instead of the reflecting mirror  431 , and only part of the beam L emitted from the exposure head  41  may be reflected and guided to the sensor unit  432 . Here, depending on the type of optical sensor in the sensor unit  432 , such as the position detecting element  434  and the light intensity detecting element  436 , the optical sensor may be damaged due to the excess power of the beam L. Therefore, by reflecting only part of the beam L with the beam splitter, the dimmed beam may be made to enter the optical sensor. In this case, the reference data storage part  523  may store a value that is set by considering the reflectance of the beam splitter as the reference data for the irradiation intensity. 
     Second Embodiment 
       FIG. 10  is a schematic diagram showing a schematic configuration of a drawing device including a calibration system according to a second embodiment of the present invention. As shown in  FIG. 10 , the drawing device  1 A according to the present embodiment includes a drawing unit  4 A instead of the drawing unit  4  shown in  FIG. 1 . In the drawing unit  4 A, a plurality of exposure heads  41  that emit beams L for exposure toward the substrate  2 , and mirror units  46 , movement mechanisms  47 , reflecting mirrors  462 , and calibration units  48 , which are used when calibrating the beams L, are provided. In the present embodiment, these mirror unit  46 , movement mechanism  47 , reflecting mirror  462 , and calibration unit  48 , together with the controller  5  described above, constitute the calibration system. The configuration of the respective components of the drawing device  1 A, other than the calibration system, is similar to that of the above-described first embodiment. In this embodiment also, a mechanism may be further provided for adjusting the focus of the beam L by varying the distance between each exposure head  41  and the substrate  2 , as with the above-described first variation. 
       FIG. 11  is an enlarged schematic diagram showing a neighborhood of the calibration unit  48  shown in  FIG. 10 , and shows the arrangement at the time of calibration. 
     The movement mechanism  47  is, for example, a single-axis actuator, and inserts the mirror unit  46  into the optical path LP of the beam L at the start of calibration (see  FIG. 11 ) and removes the mirror unit  46  from the optical path LP when the calibration is completed (see  FIG. 10 ). The configuration of the movement mechanism  47  is not particularly limited, as long as it can move the mirror unit  46  with high precision. In addition, the direction in which the mirror unit  46  is moved is not limited to the direction of conveyance of the substrate  2  (the tangential direction of the outer periphery of the conveying drum  33 ) at the irradiation position of the beam L, and the mirror unit  46  may be moved, for example, along the width direction (y direction) of the substrate  2 . 
     A reflecting mirror  461  is provided in the mirror unit  46 . The reflecting mirror  461  is an optical system that is arranged on the optical path LP when the mirror unit  46  is inserted into the optical path LP and guides the beam L in a direction different from that of the optical path LP. As with the above-described second variation, a beam splitter (half mirror) may be provided instead of the reflecting mirror  461 . 
     The reflecting mirror  462  and the calibration unit  48  are located at predetermined positions within the drawing unit  4 A. The reflecting mirror  462  is a second optical system that further reflects the beam L reflected by the reflecting mirror  461  inserted on the optical path LP, and guides the beam L toward the calibration unit  48 . Although the second optical system is configured by a single reflecting mirror  462  in  FIG. 11 , a plurality of mirrors and the like may be used to configure the second optical system. Further, as with the above-described second variation, a beam splitter (half mirror) may be used, instead of the reflecting mirror  462 , to dim the beam L that enters the calibration unit  48 . 
     An imaging optical system  481  and a sensor unit  482  are provided in the calibration unit  48 . Among which, the configuration of the sensor unit  482  is similar to the configuration of the sensor unit  432  described in the first embodiment (see  FIG. 7 ). 
     The imaging optical system  481  is a third optical system that allows the beam L reflected by the reflecting mirror  462  to be imaged on a light-receiving surface of an optical sensor in the sensor unit  482 , such as a position detecting element and a light intensity detecting element. The light-receiving surface of the optical sensor in the sensor unit  482  and the exposure surface of the substrate  2  to be exposed by the beam L are conjugated and therefore, at the light-receiving surface of the sensor unit  482  when the mirror unit  46  is inserted into the optical path LP, the same image of the beam L can be obtained as that at the exposure surface of the substrate  2  when the mirror unit  46  is not inserted into the optical path LP. Although a plurality of optical elements are shown as the imaging optical system  481  in  FIG. 11 , the third optical system may be configured with a single lens. 
     Such mirror unit  46 , movement mechanism  47 , reflecting mirror  462 , and calibration unit  48  are provided for each exposure head  41 . 
     The overall operation of the drawing device  1 A according to the present embodiment at the time of calibration is similar to that of the above-described first embodiment (see  FIG. 9 ), except that, in step S 12  of  FIG. 9 , the mirror unit  46  is inserted into the optical path LP and in step S 17 , the mirror unit  46  is removed from the optical path LP. 
     The present invention as thus far described is not limited to the above-described first and second embodiments and variations, and various inventions can be formed by appropriately combining a plurality of components disclosed in the above-described first and second embodiments and variations. For example, such various inventions may be formed by excluding some components from all components shown in the above-described first and second embodiments and variations, or by appropriately combining the components shown in the above-described first and second embodiments and variations. 
     DESCRIPTION OF REFERENCE NUMBERS 
       1 ,  1 A . . . drawing device;  2  . . . substrate;  3  . . . conveying system;  4 ,  4 A . . . drawing unit;  5  . . . controller;  21  . . . exposure pattern;  22   a  to  22   d  . . . identification marks;  31 ,  32  . . . reels;  31   a ,  32   a ,  33   a ,  34   a ,  35   a ,  36   a ,  37   a ,  414   a  . . . rotary shafts;  33  . . . conveying drum;  33   c  . . . encoder;  33   b  . . . outer periphery;  34 ,  35  . . . tension pulleys;  36 ,  37  . . . guide rollers;  41  . . . exposure head;  41   a  . . . beam emitting port;  42  . . . adjustment stage;  43 ,  48  . . . calibration unit;  44 ,  47  . . . movement mechanism;  46  . . . mirror unit;  51  . . . external interface;  52  . . . storage part;  53  . . . control part;  61  . . . substrate conveying drive device;  62  . . . calibration-use drive device;  63  . . . input device;  64  . . . display device;  65  . . . data reading-in device;  411  . . . laser light source;  412  . . . beam-shaping optical system;  413 ,  431 ,  461 ,  462  . . . reflecting mirrors;  414  . . . polygon mirror;  415 ,  481  . . . imaging optical systems;  432 ,  482  . . . sensor units;  433  . . . sensor substrate;  434  . . . position detecting element;  435  . . . light-receiving surface;  436  . . . light intensity detecting element;  521  . . . program storage part;  522  . . . pattern data storage part;  523  . . . reference data storage part;  524  . . . calibration data storage part;  525  . . . correction data storage part;  531  . . . drawing control part;  532  . . . calibration control part;  533  . . . determination part;  534  . . . correction part